international journal of engineering materials and manufacture (2016) 1(2) 71-74 https://doi.org/10.26776/ijemm.01.02.2016.05 j. norhasnidawani, h. n. azlina , h. norita, and m. h. ani department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: noorazlina_hassan@iium.edu.my reference: j. norhasnidawani, h. n. azlina, h. norita, and hanafi ani (2016). effect of nanoparticles on wettability of nanocoating on carbon steel. international journal of engineering materials and manufacture, 1(2), 71-74. effect of nanoparticles on wettability of nanocoating on carbon steel norhasnidawani johari, noor azlina hassan, norita hassan, and mohd hanafi ani received: 28 november 2016 accepted: 15 december 2016 published: 20 december 2016 publisher: deer hill publications © 2016 the author(s) creative commons: cc by 4.0 abstract nanocoatings plays an important role in coating industry. the great potential of nanocoatings was studied due to an excellent adhesion strength and corrosion protection of carbon steel. nanocoatings was formulated through copolymerization of epoxy resin with the incorporation of zinc oxide (zno) and silica (sio2) nanoparticles. zno and sio2 were synthesized using sol-gel technique. epoxy acted as host while the nanoparticles incorporate as guest components. the performance of wetting ability with different medium was analysed using contact angle. water medium showed the addition of 3wt% of hybrid between zno and sio2 was the best nanocoating to form hydrophobic surface and was also the best nanocoating surface to form hydrophilic surface with vacuum oil dropping. the contact angle was smaller than 90° in oil dropping. keywords: zinc oxide (zno), silica (sio2), nanoparticles, contact angle, nanocoating, carbon steel 1 introduction nanocoatings market is envisaged to grow over the next 5 to 10 years across all market segments. this is attributed to growing need for better facilities and advances in nanocoatings technology. this industry is segmented by type of future markets that includes anti-bacterial, anti-fouling, anti-fingerprint, easy to maintain and self-cleaning nanocoatings [1]. potential applications such as self-cleaning increasing interest in wettability concerns. wettability is one of the important characteristics that determine the properties of final coating [2]. the degree of wetting when a solid and liquid interact is determined by measurements of contact angle. surface with low wettability shows the contact angles (<90°) while large contact angle is (>90°) corresponding to high wettability [3]. steel is widely used for construction especially in heavy industries such as in the petrochemical, marine, and etc that exposed to corrosion [4]. sol-gel hybrid coatings of organic and inorganic materials can combine the mechanical toughness and flexibility of organic components with the thermal stability and hardness of inorganic components [5]. epoxy (organic) coating is a type of common organic coatings used to protect metal against corrosion. research by armelin [6] reported that the benzene rings in epoxy giving good properties such as resistance to chemical, good mechanical properties, thermal stability and good adhesion make it widely used for protective coatings. the epoxy contains ring opening during curing time. the hydrophobic and hydrophilic group in epoxy structure increases the adhesion properties. the epoxy molecule is combined with a hardener material and effect crosslinking during curing or hardening [7]. zno is used as nanoparticles increased the adhesion and absorption of the uv radiation can stop solar degradation. the uv light is transform into vibration and heat [8]. the incorporation of silica nanoparticles provides better adhesion since nanoparticles acted denser and compact structure in the coating. the coating having good properties with solid and protective network layer when the nanoparticles are uniformly distributed throughout the coating. the nanoparticles function as elastomeric structure within the coating [9]. this research discussed on the wetting ability when deionised water and vacuum oil come into contact with the carbon steel. effect of nanoparticles on wettability of nanocoating on carbon steel 72 2 methodology the nanoparticles was synthesized by using sol gel method. there were 18 pieces of carbon steels used in the study. the surfaces of samples were ground and polished with a manual hand grinder machine. the samples were then rinsed in distilled water and dried with acetone to remove traces of water. this step was conducted quickly to avoid premature corrosion. brushing technique was used to coat the samples. before coating, the epoxy was blend with hardener and stirred at 500rpm for 5 minutes, using overhead stirrer. nanoparticles powder was poured right after and continuously stirred for another 5 minutes to obtain homogeneous mix. after mixing, the modified epoxy coating was then applied onto carbon steel coupons. the coupons were left to dry overnight in fume cupboard at room temperature. then, the effect of nanoparticles on wetting ability was measured using contact angle. the conditions of testing are listed in table 1. 3 results and discussion 3.1 deionized water dropping there was attraction between the solid and liquid on the surface influenced by surface energy. based on figures 1, deionized water drop on carbon steel surface showed that partial wetting occurred. this condition is known as hydrophobic or water hating. the contact angle of water droplet on surface is between 71° to 77°. the contact angle of liquid drop is based on the adhesive forces between the liquid and the surface [9]. the adhesives force was repelled and a liquid drop minimizes its contact with the surface. it was called hydrophobic where the area of solid surface decreased. incorporation of nanoparticles into coating increased the degree of contact angle. this showed that zno and sio2 nanoparticles was effectively imparting hydrophobic properties to the steel surface and determining the corrosion behaviour of the surface. foreign particles were also repelled from the coating surface due to high contact angle. it shows that the wetting energy is getting smaller and become more hydrophobic [10]. figure 1 show micrograph images of water dropping on nanocoating surface. addition of 3wt% zno+2wt%sio2 (hybrid) was the best formulation of nanocoating to form hydrophobic surface with good work of adhesion. table 2 summarized the contact angle behaviour on different surface of nanocoating through deionized water dropping analysis. (a) (b) (c) (d) (e) (f) (g) (h) (i) figure 1: micrograph images of water dropping on nanocoating: (a) plain epoxy; (b) 2wt% zno; (c) 3wt% zno; (d) 2wt% sio2; (e) 3wt% sio2; (f) 1wt% zno+4wt% sio2; (g) 2wt% zno+3wt% sio2; (h) 3wt% zno+2wt% sio2; (i) 4wt% zno+1wt% sio2 3.2 vacuum oil dropping oil molecules have low surface tension and stronger attraction to the molecules of the solid surface. this shows that, the adhesive force is stronger than cohesive forces. vacuum oil dropping onto carbon steel showed that there are strong adhesive forces on nanocoating surfaces due low surface tension and increases the area of solid surface contact [11]. this type of surface is called partial wetting or water loving. incorporation of nanoparticles improved the ability of coatings and improved the adhesion between coating and substrate [12]. in the case of vacuum oil dropping analysis nanocoating allows liquids to spread on surface due to low surface tension. the contact angle is less than 90°, as shown in figure 2, shows that the oil drop spreads out and wet the surface. figure 2(h), exhibit the lowest contact angle among all due to strong adhesive forces. it showed that in marine applications, when there was attraction between surface and coatings, adding another layer of nanocoating was enough after certain period of time. table 3 summarized the contact angle, wetting energy and work of addition on different surface of vacuum oil dropping. norhasnidawani et al., (2016): international journal of engineering materials and manufacture, 1(2), 71-74 73 table 1: selected condition during contact angle testing properties (unit) water oil rec. temperature ( 0 c) 20 20 syringe temperature ( 0 c) 20 20 drop volume (l) 18.3 0.65 rec. time 05:54.8 53:28:4 rec. posx (mm) 0 0 rec. posy (mm) 0 0 table 2: contact angle of nanocoating (water drop) surface (wt%) contact angle (degree) wetting energy (mn/m) work of adhesion (mn/m) epoxy 72.71 21.64 94.44 2zno(single) 77.96 15.18 87.98 3zno(single) 73.38 20.83 93.63 2sio2(single) 73.05 21.23 94.03 3sio2(single) 75.31 18.46 91.26 1zno+4sio2(hybrid) 73.58 20.57 93.38 2zno+3sio2(hybrid) 74.88 18.99 91.79 3zno+2sio2(hybrid) 75.71 17.98 90.78 4zno+1sio2(hybrid) 75.86 17.78 90.58 table 3: contact angle of nanocoating (oil drop) surface (wt%) contact angle (degree) wetting energy (mn/m) work of adhesion (mn/m) epoxy 19.95 68.43 141.23 2zno(single) 12.96 70.95 143.75 3zno(single) 15.85 70.03 142.83 2sio2(single) 14.12 70.60 143.40 3sio2(single) 19.43 68.65 141.45 1zno+4sio2(hybrid) 12.76 71.00 143.80 2zno+3sio2(hybrid) 13.17 70.89 143.69 3zno+2sio2(hybrid) 11.51 71.34 144.14 4zno+1sio2(hybrid) 12.87 70.97 143.77 (a) (b) (c) (d) (e) (f) (g) (h) (i) figure 2: micrograph images of vacuum oil dropping on nanocoatings: (a) plain epoxy; (b) 2wt% zno; (c) 3wt% zno; (d) 2wt% sio2; (e) 3wt% sio2; (f) 1wt% zno+4wt% sio2; (g) 2wt% zno+3wt% sio2; (h) 3wt% zno+2wt% sio2; (i) 4wt% zno+1wt% sio2 effect of nanoparticles on wettability of nanocoating on carbon steel 74 4 conclusions in this research study, adding nanoparticles into epoxy coating decreased the wetting energy and become more hydrophobic. addition of 3wt% zno+2wt%sio2 (hybrid) was the best nanocoating surface to form hydrophobic surface for deionized water dropping. for vacuum oil dropping, adding nanoparticles allowed liquids to spread on surface. nanoparticles increased the ability of nanocoatings. there was improvement in adhesion of coating and carbon steel as a substrate. addition of 3wt% zno+2wt%sio2 (hybrid) was the best nanocoating surface to form hydrophilic surface with vacuum oil dropping. acknowledgement the authors acknowledge ministry of higher education (mohe) for research grant frgs13-077-125-0318 for funding this research activities. the authors are grateful to the materials department laboratory where the experimental studies were conducted. references 1. thomas (2013). market research study on nanocoatings. retrieve from: http://marketpublishers.com. 2. cabrera-sierra, sosa, e., oropeza, m. t., & gonzalez, i. (2012). electrochemical study on carbon corrosion process in alkaline sour media. electrochimia acta, 47(13-14), 2149-2158. 3. armelin, e. (2011). corrosion protection with polyaniline and polypyrole as anticorrosive additives for epoxy paint. corrosion science, 50(3), 721-728. 4. tan, a. l. k., & soutar, a. m. (2008). hybrid sol-gel coatings for corrosion protection of copper. thin solids film, 516(16), 5706-5709. 5. atik, m., & aegerter, m. a. (2009). corrosion resistant sol-gel zro2 on stainless steel. journal of non-crystalline solids, 147-148, 236-241. 6. shen, g. x., chen, y. c., lin c.j., & scantleburry, d. (2012). study on a hydrophobic nano tio2 coating and its properties for corrosion protection of metals. electrochimia acta, 50(25-26), 5083-5089. 7. shang, j., flury, m., james, b. h., & richard, l. zollars. (2008). comparison of different methods to measure contact angles of soil colloids. journal of colloid and interface science, 328(2), 299-307. 8. phan, h. t., caney, n., marty, p., colasson, s., & gavillet, j. (2009). surface wettability control by nanocoating: the effects on pool boiling heat transfer and nucleation mechanism. international journal of heat and mass transfer, 52(23-24), 5459-5471. 9. zhai, l., fevzi, c. c., robert, e. c., & michael, f. r. (2004). stable superhydrophobic coatings from polyelectrolyte multilayers. nanoletters, 4(7), 1349-1353. 10. shen, g. x., chen, y. c., lin, l., lin, c. j. & scantlebury, d. (2005). study on a hydrophobic nano-tio2 coating and its properties for corrosion protection of metals. electrochimica acta, 50(25-26), 5083-5089. 11. rosario, r., gust, d., antonio, a. g., mark hayes, j. l., taraci, t. c., dailey, j. w. & picraux, s. t. (2004). lotus effect amplifies light-induced contact angle switching. journal of physical chemistry b, 108(34), 12640-12642. 12. steele, a., bayer, i., & loth, e. (2009). inherently superoleophobic nanocomposite coatings by spray atomization. nanoletters, 9(1), 501–505. international journal of engineering materials and manufacture (2016) 1(2) 65-70 https://doi.org/10.26776/ijemm.01.02.2016.04 m. norsalawani, and r. bahar department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: rbahar@iium.edu.my reference: norsalawani, m., and bahar, r. (2016). minimum quantity lubrication (mql) and its effect on tool wear during miniature drilling: an experimental study. international journal of engineering materials and manufacture, 1(2), 65-70 minimum quantity lubrication (mql) and its effect on tool wear during miniature drilling: an experimental study norsalawani mohamad, and rubina bahar received: 06 october 2016 accepted: 13 december 2016 published: 20 december 2016 publisher: deer hill publications © 2016 the author(s) creative commons: cc by 4.0 abstract miniature drilling is widely used in industries including electronics and reconstructive surgeries to create small sized holes. chip removal and effective supply of coolant are the two limiting factors that make the process more complex compared to other meso scale machining processes and also contribute to the tool wear. the tool wear in the process is mainly caused by the interaction, motion and chip production between the tool and work piece. uniform supply of coolant must be ensured to reach the drilled cavity to keep the tool wear to a minimal level. this study includes experimental investigation of the tool condition after applying minimum quantity lubrication (mql) system as a greener approach as the name indicates. the tool condition with mql has also been compared with dry and flood cooling. two different types of drill bit materials (high speed steel and carbide) have been tested under same experimental condition to drill through aluminum alloy 6061 and it has been found that overall performance in terms of tool condition after applying mql was better compared to the other two methods. the overall wear propagation area was measured for both the conditions. it was seen, the wear propagation covered minimal area with mql while for flood and dry condition wear was spread over a bigger area on flank. keywords: minimum quantity lubrication (mql), micro-drilling, hss drill bit, carbide drill bit, tool wear. 1 introduction in all metal cutting operations, one of the most significant limitation is tool wear. it is caused by the normal load generated by the interaction, motion and chips produced between tool and work piece. it is important to improve the tool life, minimizing the tool wear and improve the performance of machining operations. during machining, cutting fluids also play an important role to provide necessary cooling and lubrication to protect from corrosion with enhanced chip flushing. the machined surface as well as the cutting tool’s condition is significantly affected by the cutting fluid. among the different types of lubrication system, the major two categories are flooding and mist application[1]. minimum quantity lubrication (mql) system falls under the latter category. mql uses a very small amount of a fluid. according to the german din specification, up to 50 ml/hour of lubricant (for some exceptional cases up to 150 ml/hour) can be classified under mql [2]. although the amount may vary greatly depending on the materials, processes and the tools as some materials are naturally more lubricant than others, some processes are better able to get the fluid to the right place, and bigger tools need more lubricant than smaller ones [3]. mql has been proven to be effective in terms of tool wear for various machining like grinding [4, 5], milling [6, 7] turning [8, 9] and many more. mql has larger scope to be applied in mini to micromachining as well due to the requirement of less heat removal rate and effective chip removal [3]. for micro-drilling, effect of mql is more significant as the mist coolant is more capable of entering the micro channel between the drill bit and the newly created hole; as small scale drilling is susceptible to clogging of chips with the tool [10]. for overall drilling purposes, mql has been able to draw significant attention in terms of lower rate of built up edge (bue) formation and tool life compared to dry condition[11], drilled hole roundness deviation was better using mql compared to dry and flood coolant as reported minimum quantity lubrication (mql) and its effect on tool wear during miniature drilling: an experimental study 66 by [12]. in terms of different coatings of the cemented carbide drill as reported by [13], with a special design of the drill to have better mist distribution , the performance was equivalent to flood cooling. in this paper, two different material drill bits have been tested for the tool wear condition under three lubrication condition: flood, mql and dry for drilling on aluminum alloy 6061. mql is found to be a better choice for both the tools. the average area of the wear was measured and compared for the tools used under different condition. 2 methodology 2.1 equipment and material selection the micro drilling machine used to conduct the experiment is mikrotools multi-process machine tool dt110. this machine can travel in three directions which are x, y and z axis. for this project, the aluminium alloy 6061 has been chosen for the work piece material with medium fatigue strength and good finishing characteristic. two drill bits of hss and carbide with 1 mm diameter, same drill point angle and cutting direction were used. 2.2 minimum quantity lubrication system and other equipment bluebe mql system was used with an environment friendly biodegradable lubricant. it also served as the necessary coolant. bluebe fk type can deliver air and lubricant to the nozzles which can be adjusted separately with lubricant consumption 4-8 ml per hour / per nozzle. accu-lube lb-6000 was used as the lubricant with vegetable oil base. nikon measuring microscope model mm-400/l is used to measure the wear obtained on the tool. the microscope is connected to the computer to capture the image of cutting tool by using nis-element f3.0 software. design of experiment (doe) is required to determine the relationship between the variables and parameters that will affect the response and performance. for this study, two level factorial design was used by using design-expert 6.0.8 software. 2.3. experimental parameters this study investigates the performance of mql over other two methods of lubrication dry lubrication and flood lubrication. figure 2(a-b) shows flood condition and mql condition respectively. the experimental parameters are listed in error! reference source not found.. figure 1: the blube mql system (a) (b) figure 2: drilling with (a) flood coolant (b) mql norsalawani and bahar (2016): international journal of engineering materials and manufacture, 1(2), 65-70 67 table 1: experimental parameters parameter description work piece material aluminum alloy 6061 cutting tool diameter 1.00mm depth of cut 6mm feed rate (mm/min) 8.0 spindle speed (rpm) 25000 tool material carbide and high speed steel lubrication condition dry/flood/mql table 2: types of wear found on the tools tool lubrication method tool wear observation c a r b i d e t o o l dry flank wear crater wear adhesion flood plastic deformation flank wear crater wear mql crater wear flank wear h s s t o o l dry flank wear crater wear flood crater wear flank wear burr mql flank wear adhesion crater wear 3 results 3.1 the tool wear analysis the tool wear has been analysed to compare the effect of different lubrication processes on tool wear of different materials drill bits. initial experiment was conducted on carbide drill bit under dry machining conditions with feed rate of 4 mm/min and spindle speed of 18000 rpm. however, no significant wear was seen on the tool bit. the feed rate and spindle speed are increased to the 8 mm/min and 25000 rpm respectively to obtain clear and significant tool wear. then all the experiments conditions are conducted with those new cutting parameters. the types of wear observed for two different drill bit is listed in table 2. 3.2 observation of tool wear between the processes and tool material the results of the experiments were compared for the tool wears occurred during dry machining, presence of flood coolant and with mql for every tool bit. the observations of tool wear is done using nikon measuring microscope. total area of wear is measured and compared for each condition. mainly crater wear and flank wear were observed on the tool with presence of adhesion and burr in some cases. crater wear usually results from the high temperature at the contact zone, or it exceeds the level of resistivity of the cutting materials. it is formed as a concave section on the tool face formed by the sliding action of chips on the surface while flank wear mainly occurs due to high cutting speed, low percentage of oil in fluid flow and insufficient cutting fluid. it occurs on the tool flank as a result of friction between the machined surface of the work piece and the tool flank. the most significant observations that can be seen is the adhesion of work material to the drill bit. when machining the aluminum work piece under the combined action of the temperature and pressure, the chip adhesion with the cutting tools took place. a patch of wear including circular grooves has grown significantly in flood coolant for both materials, and among them, the carbide tool bit has more adhesion because it has the least abrasive resistance. error! reference source not found. summarizes the crater wear and error! reference source not found. describes the flank wear observed for the two tools under the three different lubrication conditions. from these tables, it can be seen that flank wear was more obvious on dry machining. it occurred because the high temperature and friction at the tool-work piece area. minimum quantity lubrication (mql) and its effect on tool wear during miniature drilling: an experimental study 68 table 3: crater wear for carbide and hss tools experiment conditions dry machining flood coolant mql carbide tool hss tool table 4: flank wear for carbide and hss tools experiment conditions dry machining flood coolant mql carbide tool hss tool the flute of high speed steel and carbide tool bits were also compared as seen in error! reference source not found.. the hss tool had more obvious tool wear, compared to carbide. this may be attributed to carbide’s inherent higher hardness and toughness which enabled the carbide tool to maintain high hardness at elevated temperature, and therefore, absorbing more energy before fracture. error! reference source not found. summarizes the overall wear propagation area considering crater and flank wear. as it can be seen from the table that the propagation of wear over the tool surface was minimum with applying mql for both the tools. the effect of mql was more dominant for hss tool for flank wear and for crater wear, mql provided better machining condition for the carbide tool. figure 3 shows the interaction graph extracted from design expert plot. the comparison between flood and mql has been presented here as the dry and flood condition results were quite close. it is observed from the figures that crater wear affected carbide tool more significantly compared to hss tool. mql has proven to be the best possible lubrication option among the available three methods. when considering flank wear, carbide tool was stronger adhesion plastic deform adhesion burr norsalawani and bahar (2016): international journal of engineering materials and manufacture, 1(2), 65-70 69 compared to hss tool. in terms of lubrication method, still mql is proven to be the one to provide better tool quality irrespective of tool material used. table 5: flute condition for carbide and hss tools experiment conditions dry machining flood coolant mql carbide tool hss tool table 4: results comparison of crater wear and flank wear run tool materials machining conditions crater wear area (mm 2 ) flank wear area(mm 2 ) 1 hss flood coolant 0.0925 0.0995 2 hss mql 0.088 0.0483 3 hss dry 0.131 0.0657 4 carbide flood coolant 0.127 0.0295 5 carbide mql 0.0967 0.0198 6 carbide dry 0.2495 0.1079 (a) (b) minimum quantity lubrication (mql) and its effect on tool wear during miniature drilling: an experimental study 70 figure 3: interaction graph between experiment conditions and tool materials on the tool wear [x= a: tool material, y=b: type of coolant 4 conclusions an experimental study was conducted to observe the tool condition using three different method of lubrication: dry, flood and mql for drilling miniature holes in aluminium 6061 alloy. two different material drill bits (hss and carbide) with same geometric parameters have been used. it has been observed after machining that mql provided better tool condition in terms of flank wear, crater wear and flute condition. the wear propagation was minimal when using mql method. it is evident from the results that mql mist had better cooling effect as it could enter the cavity between the drill bit and drilled hole easily due to lower surface tension during machining compared to flood coolant. however, the tools behaved differently for different types of wear. the findings can be summarized as:  mql is suitable for different type of tool material for miniature drilling.  the tool wear propagation is minimum when using mql compared to dry and flood coolant condition.  different material tool behaved differently in terms of crater and flank wear; hss was found to be strong when crater wear was investigated while carbide tool had least flank wear under mql and flood condition. acknowledgements the authors are grateful to the kulliyyah of engineering, international islamic university malaysia for necessary technical and financial support for the work. references 1. groover, m. p. (2013). fundamentals of modern manufacturing. 2. standards (2011) committee tools and clamping devices (fws) working committee, din 69090-1 mql maching technology part 1. terms and definitions. 3. walker, t. (2013). the handbook: a guide to machining with minimum quantity lubrication, v 1.0.3. unist, inc. 4. hadad, m. j., tawakoli, t., sadeghi, m. h., & sadeghi, b. (2012). temperature and energy partition in minimum quantity lubrication-mql grinding process. international journal of machine tools and manufacture, 54-55, 1017. 5. da silva, l. r., bianchi, e. c., fusse, r. y., catai, r. e., franca,t. v., & aguiar, p. r. (2007). analysis of surface integrity for minimum quantity lubricant-mql in grinding. international journal of machine tools and manufacture, 47(2), 412-418. 6. rahman, m., senthil kumar, a., & salam, m. u. (2002). experimental evaluation on the effect of minimal quantities of lubricant in milling. international journal of machine tools and manufacture, 42(5), 539-547. 7. iqbal, a., al-ghamdi, k. a., & hussain, g. (2016). effects of tool life criterion on sustainability of milling. journal of cleaner production, 139, 1105-117. 8. attanasio, a., gelfi, m., giardini, c., & remino, c. (2006). minimal quantity lubrication in turning: effect on tool wear. wear, 260(3), 333-338. 9. hadad, m. & sadeghi, b. (2013). minimum quantity lubrication-mql turning of aisi 4140 steel alloy. journal of cleaner production, 54, 332-343. 10. smith, g. t. (2008). cutting tool technology: industrial handbook. springer. 11. bhowmick, s., lukitsch, m. j., & alpas, a. t. (2010). dry and minimum quantity lubrication drilling of cast magnesium alloy (am60). international journal of machine tools and manufacture, 50(5), 444-457. 12. ahsan, n. m. m., kibria, g. m., ahmed, r. m., islam, a. m., & hossain, m. m. (2010). performance evaluation of minimum quantity lubrication (mql) in drilling operation,” in international conference on mechanical, industrial and energy engineering, 1–5. 13. fox-rabinovich, g., dasch, j. m., wagg, t., yamamoto, k., veldhuis, s., dosbaeva, g. k., & tauhiduzzaman, m. (2011). cutting performance of different coatings during minimum quantity lubrication drilling of aluminum silicon b319 cast alloy. surface and coatings technology, 205(16) 4107-4116. international journal of engineering materials and manufacture (2017) 2(2) 25-30 https://doi.org/10.26776/ijemm.02.02.2017.01 n. a. ibrahim, h. f. h. muataz , e. y. t. adesta, n. a. endut and a. h. asman department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: muataz@iium.edu.my reference: ibrahim, n. a., hazza, m. h. f., adesta, e. y. t., endut, n. a., and asman, a. h. (2017). experimental study of stressstrain behaviour of open-cell aluminium foam sandwich panel for automotive structural part. international journal of engineering materials and manufacture, 2(2), 25-30. experimental study of stress-strain behaviour of open-cell aluminium foam sandwich panel for automotive structural part nur asmawiyah ibrahim, muataz hazza f. al hazza, erry yulian triblas adesta, nor amalina endut and asyfiq hanif asman received: 25 february 2017 accepted: 09 june 2017 published: 27 june 2017 publisher: deer hill publications © 2017 the author(s) creative commons: cc by 4.0 abstract because of high stiffness and strength to weight ratio, aluminium foam sandwich (afs) has huge advantage in automotive industries in order to reduce the vehicle’s weight which consequently will reduce the fuel consumption. while reducing the weight, afs must also maintain high strength and durability compared to other competitive materials used which perform same functionalities. afs had been proved its suitability for industrial application by previous researchers such as in aerospace, automotive and architecture. however, there is still a gap need to be filled in order to expand the use of the afs in another application. in this paper, the tensile strength of afs panel made of from aluminium skin sheets and open-cell aluminium foam core with various thicknesses is investigated. to achieve the objectives of the research, experimental work has been conducted. full factorial of two independent factors: core thickness with two levels and skin thickness with three levels. jmp software (version 11) has been used to analyse the data. experimental work was done using universal testing machine. the stress-strain behaviour was analysed. the result shows that the effect of skin to core ratio is significant on the stress-strain behaviour. keywords: aluminium foam sandwich, design of experiment, stress-strain curve, tensile strength, open-cell. 1 introduction in the past few years, metallic foams have gained their reputations in the industries all around the world. the main factor that leads to the further development of this type of material is caused by the demand of lightweight constructions such as automotive and ship parts. one of the most frequently used metallic foam is the aluminium foam. because of its low-cost manufacturing process and more convenience, aluminium foam tends to be chosen more compared to other type of metallic foam. the manufacturing process of the aluminium foam consist of two routes; pm and lm routes. lm routes used melting aluminium that then foamed to be aluminium foam. pm routes on the other hand, used powder metallurgy in order to produce the aluminium foam intended [1]. the further development of the aluminium foam is aluminium foam sandwich (afs). it is an advanced material technology that consist of highly porous aluminium foam core that sandwiched by two aluminium sheets acting as the faces on the both sides of the core [2]. applications of afs have been widely proposed on several sectors and industries including ship building [3], aircraft and railway industries [4], automotive parts [5] and several other constructions industries. afs have several advantageous to offer compared to dense aluminium metal. afs more stiff when compared to the dense aluminium sheet with the same weight [6]. moreover, when compared to bare aluminium foam, the metal sheets of the afs that acting as faces allows it bear greater tensile load and reduced the deformation of the core. bare aluminium foam has low endurance to tension and the fractures can occur faster compared to afs. the aluminium foam that has been sandwiched together with the metal sheets also can avoid the occurrence of corrosion and surface damage. figure 1 show an example [5] of using afs in manufacturing a novel lifting arm supporting a repair platform mounted on a small lorry experimental study of stress-strain behaviour of open-cell aluminium foam sandwich panel for automotive structural part 26 figure 1: lifting arm made from afs sandwich panels [5] however, the main intention of applications of afs is to reduce weight of the respective construction parts. in order to overcome the minimum level of energy resources, such as fuel, some actions must be done. energy resources, especially the non-renewable type like petroleum and natural gas need to be controlled and minimised in terms of usage. in automotive industries, to be exact, designs of the parts have to consider the reduction of the mass. reduced in mass can improve the performance and lower the usage of fuel. an extra 100 kg in weight alone would results in 0.72 l/100 km increase in fuel consumption for hybrid-electric vehicles (hev), and 0.77 l/100 km increase in fuel consumption for internal combustion engine vehicles (icev). weight is proved to have a significant factor of fuel consumption when both weight and power are evaluated as fuel consumption factor [7]. as the increase of the fuel’s price from time to time, the reductions of automotive weight may be the solutions to the problems of shortage in energy resources that we are facing nowadays. it also will benefit us in terms of economic for long term runs. in order to be used as substitute materials, afs have to undergo several tests and experiments to prove that it is qualified to replace the currently used material. the afs supposed to have the same or better properties when compared to the conventional material used for the past constructions. in terms of mechanical properties, for example, afs should possess the ability of withstanding high load and deform at a minimum level. it also needs to have a high durability in order to perform well as the substitution material in the constructions of automotive parts. 2 methodology in this research, twelve specimens of afs were tested under tensile test for determining the tensile stress/strain curve. the specimens are designed so that an aluminium foam acting as the core of the sandwich and attached in between of aluminium sheet grade 6061. based on the foams supplied, two levels of thickness of the aluminium foam were used which is 6.35 and 10 mm. while the level for aluminium skin thickness were 0.4mm, 0.6mm and 0.8 mm. the design of experiments of input combination was developed in jmp statistical analysis software and six numbers of runs with different input combination had been created. table 1 explained more regarding the number of runs required. the process begins by constructing the ‘dog-bone’ shape specimens of afs. the aluminium foams and the aluminium sheets will be cut using the edm wire cut machine to produce the intended shapes. then, the foams will be glued together using the araldite rapid steel epoxy with the aluminium sheets on the both side to become the afs as shown in figure 2. after that, the specimen was undergo tensile test using instron 5582 universal testing machine, the specimen was clamped at both and pull upward with one side remain fixed. the pulling process continued at a constant speed of 1.67 mm/min until the specimen fully brake. figure 3 shows the setup of the specimen and the specimen that is fully brake. as the load applied to the specimens, a stress-strain curve will be constructed using the bluehill software. table 1: design of experiment for afs no. of run input parameters core thickness skin thickness 1 6.35 0.4 2 6.35 0.6 3 6.35 0.8 4 10.0 0.4 5 10.0 0.6 6 10.0 0.8 ibrahim et al., (2017): international journal of engineering materials and manufacture, 2(2), 25-30 27 figure 2: ‘dog-bone’ afs specimens a b figure 3: (a) setup of the specimen on the tester machine, (b) the broken specimen. 3 process developments 3.1 fabrication of aluminium foam sandwich to investigate the stress/strain curve of aluminium foam sandwich (afs), first the sandwich panels were fabricated. before fabricating the afs, aluminium sheet and foam were cut into dog-bone shape as referred to standard. the sheet and foam were cut using electrical discharge machine (wire cut) but for thickness less than 0.4mm need to be cut by scroll saw. in this process, it is found that edm wire cut cannot support the specimen that were too thin which will cause nonlinear edge finishing. the aluminium used to produce foam was aluminium grade 6061. the bulk density and porosity of the foam was 0.2 g/cm 3 and 93% respectively. to have the connection between the skin and core, the mixture of epoxy resin and experimental study of stress-strain behaviour of open-cell aluminium foam sandwich panel for automotive structural part 28 hardener with ratio 2:1 was layered in between the aluminium sheets and aluminium foam. according to astm standard of c393/c393m, the stable ratio for designing the specimen for sandwich structure is as the equation below: 𝑡 𝑐 ≤ ~0.10 t : skin thickness c : core thickness 3.2 selection of testing method and input variables the mechanical testing method used in this research in order to determine the mechanical behaviour of stress/strain curve of afs was tensile test using universal instron testing machine. the test was conducted under the velocity control of constant 1.67 mm/min. for having the more reliable and accurate data, the test was repeated. the first trial of six run was conducted with the velocity constant of 1.67 mm/min and the output set was the tensile stress/strain curve and the maximum load afs can withstand. the thickness of foams were 6.35mm and 10mm, while the thickness of sheets were 0.4mm, 0.6mm and 0.8mm. the result and graph were extracted and tabulated and show in the result and discussion part. for the second trial, the six number of run with same input parameters combination as first trial were conducted using same machine set up. result for experimental were analysed based on the previous researchers. next, the work was continued with the data analysis. the pattern and value of maximum tensile stress-stress curve when maximum loaded and break were analysed. it is important to know the maximum load afs can withstand for determining the suitable application of the afs parameter. after that, desirability function of the model was developed in jmp statistical analysis in order to have stable and balance result. 4 experiments and measurement the experiments were designed using full factorial of two independent factors: core thickness with two levels (6.32 and 10 mm) and skin thickness with three levels (0.4, 0.6, and 0.8) mm. therefore, total six treatments have been conducted. the core and skin thickness considered the ratio not to be more than 0.1 based on astm standard of c393/c393m. each treatment has been conducted with two replications to increase the reliability of the test. the experiment was designed in order to determine the tensile stress-strain of afs and how sandwich structure affects the curve. the responses were analysed using desirability function in jmp software. the experimental work first conducted by fabrication of the afs. then the test was proceeding by gripping the both side of dog-bone afs specimen to the tensile test machine. the universal instron testing machine was connected to the computer which contained blue hill software for developing the stress-strain curve of afs. after the specimen gripped to testing machine tightly, the tensile test was started by clicking the start icon in the blue hill software and undergoes tension until the specimen break. the results were extracted from the blue hill software for analysing process. 5 results and discussions the experimental results were analysed using desirability function in jmp statistical analysis software. the stress – strain curve for the six runs have been concluded in table 2 for each individual run. table 3 concluded the results for the tensile test of afs for 6 runs. the tests were repeated in order to get more accurate result. the solid line shows the stress-strain curve obtained from the tensile tests on dog-bone specimens of afs. there two stress-strain curve for each run which represent the result for first and second trial respectively. stress was calculated by dividing the force over the cross-sectional area for both skins and core. based on the graphs tabulated below, the stress value shows the almost constant result for both first and second trial with the differences was 4% to 20%. the highest stress obtained was for run 3 for combination of skins and core thickness of 0.8mm and 6.35mm respectively. while the lowest value of stress (mpa) was for run 4 for combination of 10mm core and 0.4mm skins thickness. as expected, based on the pattern of collected data, it can be see that as the skin to core ratio increase, the stress, strain and maximum load also increase. this can be support by previous research done by shetty and han also mentioned the effect of skin to core ratio [8]. they also found out that as the skin to core ratio increase, the tensile stress also experience the increases. ibrahim et al., (2017): international journal of engineering materials and manufacture, 2(2), 25-30 29 table 2: tensile stress-strain curve for afs run first trial second trial 1 2 3 4 5 6 experimental study of stress-strain behaviour of open-cell aluminium foam sandwich panel for automotive structural part 30 table 3: data compilation of tensile test on afs for first and second trial run skin to core ratio first trial second trial maximum stress (mpa) maximum strain (mm/mm) maximum load (n) maximum stress (mpa) maximum strain (mm/mm) maximum load (n) 1 0.062 12.854 0.002 1378.61 15.045 0.007 1613.63 2 0.094 23.247 0.007 2632.73 22.16 0.011 2509.64 3 0.126 26.998 0.014 3219.56 28.601 0.018 3410.70 4 0.062 10.328 0.006 1673.00 8.059 0.004 1305.60 5 0.094 15.482 0.011 2553.36 16.246 0.014 2729.25 6 0.126 19.734 0.016 3433.72 21.104 0.020 3672.00 6 conclusions in this study, specimens of afs with two levels of core thickness and three levels of face thickness have been fabricated. next, the specimens have been undergone through tensile test were the stress-strain behaviour was analysed. based on this experimental study of afs the following conclusions are drawn.  increase in the ratio of face-to-core thickness will increase the tensile modulus value of the specimen.  increase in face thickness will increase the tensile modulus value if the core thickness kept constant.  increase in core thickness will decrease the tensile modulus value if the face thickness kept constant.  in order to replace the aluminium alloy car parts, the design of the afs need to be modified so that it will become stronger. acknowledgement this research was funded by ministry of higher education malaysia under research grant frgs15-247-0488. the authors also acknowledged the support from technical staff from manufacturing and material engineering department for the support in carrying out the research work. references 1. kammer, c. (1999). aluminum foam. talat lecture 1410, european aluminium association, 1-24. 2. banhart, j., & seeliger, h. w. (2012). recent trends in aluminium foam sandwich technology. advanced engineering materials, 14(12), 1082-1087. 3. banhart, j., schmoll, c., & neumann, u. (1998). light-weight aluminium foam structures for ships. in proceedings of the conference on materials in oceanic environment, 55-63. 4. yu, c. j., eifert, h, banhart, j., and baumeister, j. (1998). metal foaming by a powder metallurgical method: production, properties and applications, materials research innovations, 2, 181–188. 5. banhart, j. (2005). aluminium foams for lighter vehicles. international journal of vehicle design, 37 (2-3), 114125. 6. ashby, m. f., evans, t., fleck, n. a., hutchinson, j. w., wadley, h. n. g., & gibson, l. j. (2000). metal foams: a design guide. elsevier. 7. reynolds, c., & kandlikar, m. (2007). how hybrid-electric vehicles are different from conventional vehicles: the effect of weight and power on fuel consumption. environmental research letters, 2(1), 014003. 8. shetty, r., & han, c. d. (1978). a study of sandwich foam coextrusion. journal of applied polymer science, 22(9), 2573-2584. international journal of engineering materials and manufacture (2017) 2(3) 58-66 https://doi.org/10.26776/ijemm.02.03.2017.03 a.h. abdullah, d. sujan cdt 250, curtin university malaysia 98009 miri, sarawak, malaysia e-mail: d.sujan@curtin.edu.my reference: abdullah, a.h., and sujan, d. (2017). mechanical performance of cockle shell (caco3) powder and oil palm fibre reinforced epoxy composites. international journal of engineering materials and manufacture, 2(3), 58-66. mechanical performance of cockle shell particles (csp) and oil palm fibre (opf) reinforced epoxy composite abdul hamid abdullah and sujan debnath received: 15 august 2017 accepted: 13 september 2017 published: 15 september 2017 publisher: deer hill publications © 2017 the author(s) creative commons: cc by 4.0 abstract the effects of particle sizes (range 1, 2 and 3) and particle loading (5wt%, 10wt%, 15wt%, 20wt% and 25wt %) on the mechanical properties (tensile and flexural properties), water absorption properties and morphology analysis (optical microscope) of epoxy composites reinforced with cockle shell particles and hybrid epoxy based composite reinforced with cockle shell particles and oil palm fibres were investigated. pre-chemical treatment of alkaline solution (naoh) with 5% concentration was used to treat the oil palm fibre prior to the fabrication of composite. based on the findings, the composite with smaller size and lower loading of cockle shell particle showed higher improvement in mechanical properties. meanwhile, the hybrid epoxy based composite reinforced with smaller size of cockle shell particle and oil palm fibre showed enhancement in mechanical properties. for water absorption analysis, cockle shell particle-epoxy composites with lower particle loading showed less water uptake. keywords: cockle shell particle, oil palm fibre, epoxy composite 1 introduction there are various types of fibres and fillers that been used in the polymer composites such as glass, carbon, aramid, nylon, carbon black and silica etc. however, the movement towards environmentally sustainable engineering solutions has led to the rise of another class of composite material, commonly referred to as “green composites” that contain either naturally occurring and/or waste material as one of its component. the utilization of waste materials which are abundant and cheap, especially from clean resources, has become more popular nowadays. seashell has been considered to be a good candidate to be used as a bio-filler for preparing polymer composites because it is inexpensive, abundant, environmental friendly and is a renewable resource. moreover, it has very high content of calcium carbonate (caco3) plus organic matrix. calcium carbonate (caco3) extracted from limestone, has been long been used as a filler in the plastic and rubber. however, the mining and quarrying of limestone is not very sustainable in the long term compared to seashell which is renewable resource. moreover, the quarrying of limestone is damaging the landscape, producing smoke and dust plus deteriorating the water quality. the large consumption of cockles generating a large volume of shell waste which contributes to the deterioration of environment as it needs to be disposed at the landfill site. recycling of shell waste is very good way to reduce the garbage that need to be processed at the landfill site, and offers an opening to develop this waste material into useful products. the aim of this study is to investigate the effect of different cockle shell particle loading and size reinforced polymer composites and the hybrid polymer based composites reinforced cockle shell particle and oil palm fibre in term of mechanical, water absorption and morphology properties. 2 methodology 2.1 materials the cockle shells used were collected from restaurants, and the oil palm fibre is supplied by sarawak oil palm company. the cockle shell particles were extracted by grinding the shell using ball mill machine. while oil palm fibres were extracted from oil palm empty fruit bunch (opefb) through retting process. the epoxy resin was selected as matrix phase and hardener used as curing purposes from miracon sdn. bhd was procured together. mechanical performance of cockle shell (caco3) powder and oil palm fibre reinforced epoxy composites 59 2.2 preparation of cockle shell particles the cockle shell particles were separated in three ranges size depending on size of the particles. three series of samples (epoxy reinforced by cockle shell particles) were prepared: • first series with 5, 10, 15, 20 and 25 wt% particles belonging to particles size (≥ 63 and < 212 (µm) range 1. • second series with 5, 10, 15, 20 and 25 wt% particles belonging to particles size (≥ 212 and < 425 (µm) range 2. • third series with 5, 10, 15, 20 and 25 wt% particles belonging to particles size (≥ 425 and < 500 (µm) range 3. 2.3 fibre treatment the oil palm fibres were treated with 5% concentration alkaline solution. then, the fibres were immersed into 5% concentration of sodium hydroxide (naoh) for 5 hours at room temperatures. subsequently, the fibres were washed with distilled water until the ph 7 value was reached. finally, the fibres were dried in an oven at 80 °c for 8 hours and then sealed in plastic bag. 2.4 fabrication of composite hand lay-up process was chosen in the fabrication of the composites. prior to fabrication of frekote 770-nc (release agent) was applied on the surface of the mould. the masses of 5 wt%, 10 wt%, 15 wt%, 20 wt% and 25 wt% of cockle shell particles was prepared and measured. the ratio of epoxy resin to hardener was 100:30 according to the manufacturer guidelines. then the cockle shell particles was mixed with epoxy resin and stirred thoroughly for 5 minutes until the filler was completely mixed with the resin by using scraprotatescrap-mixing method. this method was to reduce the trapping of air bubbles. next, was degasified using a vacuum chamber. after that, the mixture was poured into the mould and left for solidification. after solidification, composites were post–cured in an oven for 2 hours at 80oc. for reference purpose, pure epoxy specimens were also fabricated. figure 1: hand layup technique [3] 2.5 mechanical property analysis the mechanical properties of the composites (tensile and flexural properties) were tested by using the universal testing machine. the tensile testing was conducted accordance to astm d638 while flexural testing was conducted accordance to astm d790. the crosshead speed was fixed at 5mm/min and 5 kn of load cell was applied until the specimen was failed. five identical specimens of every sample were used for each test. 2.6 water absorption property analysis the water absorption of composite specimen was conducted accordance to astm d570. the initial weight of three identical composite specimens for each sample was recorded before immersed in the distilled water. the composite specimens were taken out from the distilled water for every 24 hours to study the water absorption for each specimen. 2.7 morphology analysis the morphological analysis of the fracture surface of cockle shell particles-epoxy composites and cockle shell/oil palm fibres-epoxy composites were conducted by an optical microscope. by means of this observation, it restricted the view to only observe the dispersion and agglomeration of particles and fibre pull out of the composite specimen after fracture and the weak matrix bonding can also be seen. abdullah and sujan (2017): international journal of engineering materials and manufacture, 2(3), 58-66 60 3 results and discussion 3.1 mechanical property figure 2 and figure 3 illustrated the tensile and flexural strength for the composites as a function of particle loading. it was observed that decrease in tensile and flexural strength with the increasing of particle loading for all three different particle sizes composites. one of the factors for poor mechanical properties at higher particle loading was due to the poor adhesion between the epoxy resin and particles. this poor adhesion increases with the increasing of particle loading. this poor adhesion would lead to inefficient of stress transfer at the particle filled epoxy interface, thus caused de-bonding to occur and generates stress concentration and affects the particles not able to carry any load, finally accelerates the specimen of the composite to break. furthermore, the poor dispersion of cockle shell particles, presence of void or porosity and de-wetting of epoxy resin inside the composite specimens, decreased the tensile and flexural strength of composite at higher particle loading by generating stress concentration points which lead to a crack initiation spot under the applied stress [4]. moreover, decrease in tensile and flexural strength was observed when the particle size increases. this was due to particles with smaller size have a higher total surface area, thus providing higher strength of particles filled epoxy composites, in other words, tensile and flexural strength increase with the increasing of surface area filled particles, so a more effective stress transfer from the epoxy resin to the particles are able to be achieved [5]. besides, increasing in particle size caused the reduction of wettability between the adhesion of particles and epoxy resin. thus, the effectiveness number of bonds between particles and epoxy resin would decrease. consequently, the surface area of compatibility would decrease, thus the tensile and flexural strength decrease with increasing particle size [6]. as referring to figure 4 and figure 5, it was observed that tensile and flexural modulus increase linearly with the increasing of particle loading until an optimum was reached. the improvement can be indicated to good adhesion between the particlesmatrix. figure 2: tensile strength versus various particles loading figure 3: flexural strength versus various particles loading mechanical performance of cockle shell (caco3) powder and oil palm fibre reinforced epoxy composites 61 figure 4: tensile modulus versus various particles loading figure 5: flexural modulus versus various particles loading figure 6 and figure 7 illustrated the effect tensile and flexural strength on the cockle shell particle/oil palm fibre hybrid epoxy composites. it was observed that the tensile strength of hybrid composite is inversely proportional to the cockle shell particle size. according to figure 6, the tensile strength of hybrid composites with particles size in range 1 (33.83 mpa) and range 2 (28.03 mpa) showed an improvement of 35.3% and 21.9% respectively as compared to particles size in range 3 (21.88 mpa). in the figure 7, the flexural strength with improvement of 54.3% and 47.8% was observed at composites with particles size in range 1 (96.78 mpa) and range 2 (84.74 mpa) as compared to particles size in range 3 (44.21 mpa) respectively. apart from that, it was also observed the flexural strength of hybrid composites were higher as compared to the cockle shell epoxy composites in range 1 and 2 respectively as shown in figure 7. for example, the flexural strength of hybrid composites in range 1 and 2 had increased 19% and 12% as compared to the cockle shell particles epoxy composites in range 1 and 2 respectively. abdullah and sujan (2017): international journal of engineering materials and manufacture, 2(3), 58-66 62 figure 6: tensile strength of epoxy composites figure 7: flexural strength of epoxy composites figure 8: tensile modulus of epoxy composites mechanical performance of cockle shell (caco3) powder and oil palm fibre reinforced epoxy composites 63 figure 9: flexural modulus of epoxy composites the theory behind the tensile and flexural strength of hybrid composite were inversely proportional to the particle size were mainly due to the good interaction between the particle, fibre and matrix with the decreasing of particle size. according to the research by packham, the quality of interface adhesion for fibre-reinforced composites plays an important character for the strength of particulate composites. the strength of interface adhesion determines the stress transfer between the mechanisms [7]. furthermore, for well bonded particles composite, the applied stress is able to transfer sufficiently to the particles from the matrix, hence this improves the strength of composite [8]. besides, the flexural modulus of hybrid composites with particle size in range 1 and 2 had increased 9.6% and 18% as compared to hybrid composites in range 3. as referring to figure 8, it showed that the tensile modulus of hybrid composite decrease with decreasing the size of cockle shell/oil palm fibre-epoxy composite. the reasons for decrease in strength and modulus were due to the poor interaction caused by the hydrophilic properties of particles and oil palm fibres (some waxy substances, natural fats and impurities were still entrapped on the surface of oil palm fibres after chemical treatment) and the hydrophobic properties of epoxy resin. this poor interaction resulted in debonding of filler and fibres from the matrix. the increase in flexural modulus as shown in figure 9 can be attributed to good interfacial adhesion between constituents of the composite [9]. 3.2 water absorption property figure 10, figure 11 and figure 12 showed the effect of particle size on the percentage of water absorption for the epoxy composites. it was observed that the percentage of water absorption of composites increased constantly with the increasing of immersed time and particle loading for all three different particle sizes. after few days of immersion, “white layer substance” was observed on the top of water surface. the white layer substance became thicker and the void became clearer on the surface of the composites with the increased of immersion time. this was due to the loosing of resin after the long immersion of time, with the loosing of resin which could lead to larger interfacial area between the particle and matrix, hence caused the increasing of water absorption [10]. besides, high percentage water absorption of composites was due to the hydrophilic nature of natural filler. one of the reasons for higher water absorption at higher particle loading was due to the increasing formation of agglomerations causes by the difficulties of obtaining a homogeneous dispersion of particle within the matrix. the agglomeration of particles could lead to the trapping of air bubbles in the composite. thus, the capacity of water absorption increases at higher particle loading. by comparing to the figure 10, figure 11 and figure 12, it shows that the composite with particle size in range 1 (smallest particle size in this research) had higher percentage of water absorption than the particle size in range 2 composite and 3 composite. this happened because smaller particle size has higher total surface area which leads to increase of water uptake. abdullah and sujan (2017): international journal of engineering materials and manufacture, 2(3), 58-66 64 figure 10: water absorption versus square root of hours (≥ 63 and < 212 (µm) figure 11: water absorption versus square root of hours (≥ 212 and < 425 (µm) figure 12: water absorption versus square root of hours (≥ 425 and < 500 (µm) mechanical performance of cockle shell (caco3) powder and oil palm fibre reinforced epoxy composites 65 3.3 morphology property referring to figure 13(a), it can be observed that the cockle shell particle-epoxy composite with size in range 1 (≥ 62 and < 212 (µm) had good dispersion of particles, as it also can be seen that the particles was surrounded by epoxy resin. this indicating good dispersion of particles filled epoxy resin in the composite, thus resulting in good particlematrix adhesion. as referring to figure 13(b), the cockle shell particle-epoxy composite with size in range 3 (≥ 425 and < 500 (µm) experienced agglomeration between the particles in the composite, this represent poor interface adhesion between the particle and matrix, thus lead to debonding of particle in this composite. in figure 14, it can observe that the oil palm fibre reinforced epoxy composite experienced fibre pull out. moreover, it also showed that the oil palm fibre composite experienced poor distribution of fibre and the present of void in the composite thus caused debonding to occur and finally leads to decrease in mechanical properties. figure 13: optical microscope image of cockle shell particle epoxy composite with size in (a) range 1 (≥ 62 and < 212 µm), and (b) range 3 (≥ 425 and < 500 µm) figure 14: optical microscope of cockle shell particle and oil palm fibre reinforced epoxy composite 4 conclusions the summary is as follows: • the results show a major improvement in mechanical properties with the decreasing of particle size and particle loading. • the young’s modulus of cockle shell particle-epoxy composite was observed to be increased with increasing particle loading. • for hybrid composite, it was observed that the tensile and flexural strength increase with decreasing particle size. • morphology analysis showed that smaller size of cockle shell particles composite had good dispersion of particle compared to larger size of particles. • the strength of composites is strongly affected by the particle size and loading. abdullah and sujan (2017): international journal of engineering materials and manufacture, 2(3), 58-66 66 acknowledgement the researchers would like to thank the curtin university sarawak for providing the research grant (csrf) that has made this work possible references 1. supaphorn, t., yamada, k., leong, y. w. & hamada, h. (2011). development of cockleshell-derived caco3 for flame retardancy of recycled pet/recycled pp blend. materials sciences and applications, 2, 59-69. 2. yuhazri, m. y., phongsakorn, p.t. & haeryip, s. (2010). a comparison process between vacuum infusion and hand lay-up method toward kenaf/polyster composites. international journal of basic & applied sciences, 10(3), 54-57. 3. behzad, k. (2011). effect of calcium carbonate as mineral filler on the physic and mechanical properties of wood based composites, world applied science journal, 13(1), 129-132. 4. arrakhiz f. z., el achaby m, malha m, bensalah m.o., fassi-fehri, o., bouhfid, r. (2012). mechanical and thermal properties of natural fibres reinforced polymer composites: doum/low density polyethylene. materials and design, 43, 200-205. 5. li, y., pickering, k. l. (2008). hemp fibre reinforced composites using chelator and enzyme treatments. composites science and technology, 68(15), 3293-3298. 6. packham, d. e. (2001). work of adhesion: contact angles and contact mechanics. international journal of adhesion and adhesives, 16(2), 121-128. 7. nakamura, y., yamaguchi, m., okubo, m. & matsumoto, t. (1992). effect of particle size on mechanical properties of epoxy resin filled with angular-shaped silica. journal of applied polymer science, 44(1), 151-158. 8. gu, j., ma, l., gan, m., zhang, f., li, w. & huang, c. (2012). preparation and thermal properties of poly (2,3dimethylaniline)/zro2 composite. thermochimica acta, 549, 13-16. 9. hussein, a. a., salim, r. d. & sultan, a. a. (2011).water absorption and mechanical properties of high density polyethylene/ egg shell composite, journal of basrah researches (sciences), 37(3a), 15. 10. shuhadah, s., & kamaruddin (2008). thermal analysis, water absorption and morphological properties of egg shell powder filled low density polyethylene composites, proceedings of mucet, unimap, kangar, perlis, 1516. international journal of engineering materials and manufacture (2021) 6(3) 187-194 https://doi.org/10.26776/ijemm.06.03.2021.10 m.h. afif 1 , sumaiya islam 1 , neamul khandoker 2 , abdul md mazid 2 1 department of mechanical engineering, faculty of engineering and science, curtin university, malaysia. 2 college of engineering and aviation, central queensland university, melbourne, australia. e-mail: n.khandoker@cqu.edu.au & a.mazid@cqu.edu.au reference: afif et al. (2021). shear and hardness properties study of aa-6061 aluminium alloy lap-joints produced by friction stir welding process using h13 tool steel. international journal of engineering materials and manufacture, 6(3), 187-194. shear and hardness properties study of aa-6061 aluminium alloy lapjoints produced by friction stir spot welding process using h13 tool steel afif bin mohamad hanapiah, sumaiya islam, neamul khandoker and abdul md mazid abstract by virtue of high-strength verses weight ratio aluminium alloys are achieving attentions in automobile, marine, and aircraft industries as it reduces the fuel consumption for running the vehicles. but their main drawback is the destruction of their carefully engineered microstructures by high heat generated in traditional welding processes. friction stir welding (fsw) minimizes excessive heat in the welding zone and does not influence the microstructural features. fsw is currently one of the recommended solutions for manufacturing aluminium alloy welded machine parts. in this study, aa6061 al-alloy strips were lap joined using the improvised fsw setup tool clamping it on the spindle of a cnc milling machine with the speed rate varied from 1000 rpm to 3000 rpm, and three different feed rates 5, 15, and 25 mm/min. shear strength experiments of these joints revealed that samples created with the speed rate of 1000 rpm and feed rate of 25 mm/min performed best showing the highest load carrying capacity of 8976 n with elongation of 1.04%. they also demonstrated highest vickers hardness value of 31 at the centre of the weldment. keywords: 6061 aluminium alloy, machine design, friction stir welding, shear strength, hardness, automobile 1 introduction friction stir welding (fsw) is based on a very simple concept. in 1991, the welding institute (twi), uk invented friction stir welding in which a rotating pin stirs the material across the joint line forming the bond with two plates of either same or dissimilar material. the friction between the tool and the top surface of material will generate heat and cause plastic deformation of the material without melting it [1]. the fsw process takes place in the solid phase below melting temperature point of the material. as a result, it does not experience defects related to re-solidification, porosity, and cracking. the joint will have a fine microstructure and lead to good mechanical properties compare to usual fusion welding technique which causes degradation to weld material [1]. furthermore, lower temperature operation will reduce distortion and residual stresses. figure 1 shows the process of friction stir spot welding (fssw) to a lap joint with two sheets. a rotating tool with the pin is plunged into the material from the top surface of the upper sheet for given time to generate heat from the friction and plastic deformation. there is a backing plate to support the lower sheet from downward tool force. softened material near the tool cause plastic flow and the mix up of upper and lower sheets materials with assistance from the shoulder that provides compressive force. the solid phase bond is built after the tool is drawn away from the material. the appearance and cross-sectional configuration of spot stir welding shown in figure 2. the top surface will look like a button with hole and bottom surface is flat. from cross section it is observed that the upper and lower sheet materials are mixed, and the tool penetrates up to the lower sheet. previous studies demonstrated the effect of welding parameters on microstructure of dp600 steel material [3]. formation of bainite and ferrites were discussed relating to the increased hardness property compared to the base metal. another study used a mathematical model to predict the tensile strength of friction stir welded aluminium alloy [4]. the developed model could predict the tensile strength of fsw joint with 95% confidence level. studies of friction stir welding of dissimilar materials were also reported [5]. apart from these there are a lot of information on friction stir welding process automation and control [6]. self-optimization and tool wear of fsw process were also of importance for various researchers [7]. the objective of this current study is to develop a friction stir spot welding setup and use it to investigate the effect of fssw process parameters on strength properties of the manufactured joints. received: 12 march 2021 accepted: 08 may 2021 published: 15 july 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 mailto:n.khandoker@cqu.edu.au shear and hardness properties study of aa-6061 aluminium alloy lap-joints produced by friction stir welding process 188 figure 1: friction stir spot welding (fssw) illustration. (a) plunging state (b) spot welding stage (c) retraction stage [2] figure 2: spot friction stir welding appearance and cross section (mishra, 2007) 2 experimental setups 2.1 fixture and backing plate for friction stir spot welding, the design of backing plate and fixtures is crucial for weld quality. it is important that workpiece does not lift or move during the welding process. the objective of the design is to ensure that it provides good weld quality. manufacturing of clamping system and welding table will determine the quality of the welding (daniela lowasser 2009). fixture design contains several parts with different materials. first part is a backing plate which is placed below the weld specimen. it provides support for the axial force from the tool during the welding process. also, the backing plate is required to withstand high-temperature operational environment and to have good heat dissipation properties to improve weld quality (p. upadhyay 2010). selected material for the backing plate is h13 tool steel. tool steel was selected because of its excellent combination of resistance to thermal fatigue cracking and high toughness (hudson tool steel corporation 2016). next fixture component is the side plates. weld coupon sides need to be supported against the rotational force from rotating tool. the elongated holes for the side plates are used to accommodate different sizes of the coupons. these plates do not require to have same properties as the baking plate and top plate because it has small contact area with the coupons. last part is the top plate which provides clamping to the weld specimen in lap joint configuration. the clamp is needed to avoid unnecessary material distortion during applied force and arising temperatures. selected material for this application is tool steel. for the tool, a simple design with high effectiveness is selected. in fssw, the tool is the key component in generating required heat to soften the material for welding process and provide force to join two sheets together. tool material must resist thermal fatigue cracking as it operates in high temperature. h13 tool steel was selected because of its combination of resistance to thermal cracking and toughness (azom 2013). h13 tool steel has been tested for many friction spot stir welding applications and gave better quality for pin less tool design (r rai 2013). table 1 show the chemical composition of the h13 tool steel. the complete fssw manufacturing set-up is shown in figure – 3, 4, and 5. reference: afif et al. (2021). international journal of engineering materials and manufacture, 6(3), 187-194. 189 table 1: chemical composition of h13 tool steel [8] material c mn si cr mo v h13 tool steel 0.32-0.45 0.20-0.50 0.80-1.20 4.75-5.50 1.10-1.75 0.80-1.20 figure 3: friction stir spot weld manufacturing set-up figure 4: tool fitted into collet and chuck figure 5: assembly of fssw fixture on the milling table shear and hardness properties study of aa-6061 aluminium alloy lap-joints produced by friction stir welding process 190 2.2 welding schedules the experiment was conducted according to the welding schedules below so that each weld condition has unique parametric setup. the fssw capability window has been developed based on the rotational speed and feed rate of the tool of a cnc milling machine (leadwell v30). pre-trial of the welding have been conducted to determine the maximum and minimum capacity of the cnc milling machine. the operational window of friction spot stir welding is shown in table 2 and figure 6. the experiment was conducted at each end of operation boundary and a point in the middle. the tool penetration depth was kept constant for all experiments at 4 mm. table 2: weld conditions for fssw condition tool rotation (rpm) feed rate (mm/min) 1 3000 25 2 3000 5 3 2000 15 4 1000 5 5 1000 25 figure 6: fssw operational ranges figure 7: weld coupon under lap shear tensile test with universal testing machine 0 5 10 15 20 25 30 0 500 1000 1500 2000 2500 3000 3500 f e e d r a te ( m m /m in ) tool rotation (rpm) friction spot stir welding operation reference: afif et al. (2021). international journal of engineering materials and manufacture, 6(3), 187-194. 191 3 result and discussion 3.1 fssw lap shear strength to investigate the quality of the friction spot stir welds manufactured at different conditions, samples from each weld conditions 1, 2, 3, 4, and 5 were tested for their strengths. the lap shear tensile tests were conducted with instron 5982 universal testing machine. the samples were clamped to the machine as shown in figure 7. as the test started, weld sample was pulled at a rate of 1 mm/min. all the data was recorded in a computer connected to the testing machine using instron bluehill software. based on the graph in figure 8, weld produced under condition 5 (1000 rpm, and 25 mm/min feed rate) had the highest average strength of 8976 n followed by condition 4 (1000 rpm, and 5 mm/min feed rate) with around 7600n strength. lowest strength was obtained by condition 3 (2000 rpm, and 15 mm/min feed rate) followed by condition 1 (3000 rpm, and 25 mm/min feed rate) and condition 2 (3000 rpm, and 5 mm/min feed rate). condition 5 shows that slow tool speed combined with high feed rate resulted into strong lap shear strength as the material around the tool properly stirred and mixed with combinations of high axial pressure. moreover, high tool speed caused larger grain size of the microstructure resulting into a reduction of weld strength [9]. figure 8: graph of load vs extension (compared all condition) 3.2 lap shear strength optimization from experimentally obtained shear strength data, further analysis has been made to determine the optimization point for welding process parameters such as feed rate and tool speed. data optimization of the welding process was determined using design expert® software. for this experiment, the welding parameters were limited to an operational range determined earlier as shown in figure 6. the output of the software is shown in figure 9. for optimum design point equal to one, the parameter is outside the operational boundary. therefore, the best prediction is close to experimental condition 5 (1000 rpm, and 25 mm/min feed rate) with a design point of 0.825. 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2 3.6 4 4.4 4.8 5.2 5.6 6 a p p l i e d l o a d ( n ) extension (mm) condition 1 condition 2 condition 3 condition 4 condition 5 shear and hardness properties study of aa-6061 aluminium alloy lap-joints produced by friction stir welding process 192 figure 9: desire points for optimized welding parameter 3.3 hardness distribution figure 10 shows the position of the hardness profile test for welded aluminium. the tests were conducted based on atsm e92-2016 standard [10]. samples were tested across the weld area using akashi vickers hardness tester. three points were selected for each sample. one point at the centre of tool insertion and one point at the left side and another at right side with 7 mm distance apart. one kg indentation force for 10 seconds was used for all the tests. figure 11 shows the hardness profile for all weld conditions. it was observed that all manufacturing conditions produced almost the same hardness trend. hardness is at its peak in position 2 which is the centre of the weld and the hardness value decrease towards the outer diameter of the weld. it is also can be observed that condition 5 (1000 rpm, and 25 mm/min feed rate) had the highest overall hardness followed by condition 4 (1000 rpm, and 5 mm/min feed rate). lowest overall hardness was observed for condition 1 (3000 rpm, and 25 mm/min feed rate). it shows that feed rate has a minor influence on the obtained hardness values. figure 10: hardness profile measurement positions design-expert® software factor coding: actual desirability design points 1.000 0.000 x1 = a: rpm x2 = b: feed 1000 1500 2000 2500 3000 5 10 15 20 25 desirability a: rpm (rpm) b : f e e d ( m m /m in ) 0.2 0.2 0.4 0.4 0.6 prediction 0.825 reference: afif et al. (2021). international journal of engineering materials and manufacture, 6(3), 187-194. 193 figure 11: hardness profile for fssw aluminium 4 conclusions the aim of this study was to gain a better understanding of the friction stir spot welding process so that it can be an alternative to conventional lap joining processes. by using a cnc milling machine, friction spot stir welding was performed successfully. the key components for friction spot stir welding for aluminium are the tool and a good fixture. there were three components of the fixture used in the experiment which were a backing plate, side plates and top plate. all components functioned as per the design. following is the summary of obtained results. • the process of friction spot stir welding was achieved with the designed fixtures and good welds were manufactured. • friction stir spot weld quality was determined based on the lap shear strength and vickers hardness number. • the highest strength of 8976 n at 2.6 mm extension was obtained at the fssw manufacturing condition of 1000 rpm and 25mm/min feed rate. • the highest vickers hardness values (hv) were obtained at the centre of each weld for all manufacturing conditions. • the highest overall hardness number (hv 31) was obtained at 1000 rpm and 25 mm/min feed rate and the lowest overall hardness number (hv 28) was obtained at 3000 rpm, and 25 mm/min feed rate. references 1. k. mishra, friction stir welding and processing science and engineering, springer, 2014. 2. m. w. m. rajiv s. mishra, friction stir welding and processing, asm international, 2007. 3. hamid ashrafi, m shamanian, r. emadi, and m ahl sarmadi, "effect of welding parameters on the microstructure and tensile properties of friction stir welded dp600 steel," sae int. j. mater. manuf., 2019. 4. k. elangovan, v. balasubramanian, s. babu, "predicting tensile strength of friction stir welded aa6061 aluminium alloy joints by a mathematical model," materials and design, 30, pp 188–193, 2009. 5. sadeesh p, venkatesh kannan m, rajkumar v, avinash p, arivazhagan n, devendranath ramkumar k, narayanan s, "studies on friction stir welding of aa 2024 and aa 6061 dissimilar metals," procedia engineering, 2014. 6. b.t. gibson, d.h. lammlein, t.j. prater, w.r. longhurst, c.d. cox, m.c. ballun, k.j. dharmaraj, g.e. cook, a.m. strauss, "friction stir welding: process, automation, and control," journal of manufacturing processes, 2014. 7. r.a. prado, l.e. murr, k.f. soto, j.c. mcclure, “self-optimization in tool wear for friction-stir welding of al 6061+20% al2o3 mmc, materials science and engineering a, 349, pp 156-165, 2003. 8. azom, "h13 tool steel chromium hot-work steels," 10 july 2013. [online]. available: http://www.azom.com/article.aspx?articleid=9107. [accessed 20 mac 2017]. 9. zhaohua zhang, xinqi yang, jialong zhang, guang zhou, xiaodong xu, binlian zou, "effect of welding parameters on microstructure and mechanical properties of friction stir spot welded 5052 aluminum alloy," materials and design, pp. 4461-4470, 2011. 10. astm e92 16, astm international, west conshohocken, pa, 2016. 26 27 28 29 30 31 7 m m 0 m m + 7 m mv ic k e r s h a r d n e ss n u m b e r (h v ) hardness test position condition 1 condition 3 condition 4 condition 5 shear and hardness properties study of aa-6061 aluminium alloy lap-joints produced by friction stir welding process 194 11. z. c. daniela lowasser, friction stir welding: from basics to applications, elsevier, 2009. 12. a. r. p. upadhyay, "effects of thermal boundary conditions in friction stir welded aa7050-t7 sheets," materials science and engineering, p. 1537–1543, 2010. 13. "hudson tool steel corporation," 2016. [online]. available: http://www.hudsontoolsteel.com/technicaldata/steelh3. [accessed 26 october 2016]. 14. a. d. h. k. d. h. b. &. t. d. r rai, "review: friction stir welding tools," science and technology of welding and joining, pp. 1743-2936, 2013. 15. a. b. ashu garg, "on lap shear strength of friction stir spot welded aa6061 alloy," journal of manufacturing processes, pp. 203-215, 2017. 16. y. j. chao, "failure mode of spot welds:interfacial versus pullout," science and technology of welding and joining, pp. 133-137, 2003. international journal of engineering materials and manufacture (2016) 1(2) 59-64 https://doi.org/10.26776/ijemm.01.02.2016.03 d. m. nuruzzaman , f. f. b. kamaruzaman, and n. b. m. azmi faculty of manufacturing engineering, university malaysia pahang 26600 pekan, pahang darul makmur, malaysia e-mail: dewan052005@yahoo.com reference: nuruzzaman, d. m., kamaruzaman, f. f. b. and azmi, n. b. m. (2016). effect of sintering temperature on the properties of aluminium-aluminium oxide composite materials. international journal of engineering materials and manufacture, 1(2), 59-64 effect of sintering temperature on the properties of aluminiumaluminium oxide composite materials dewan muhammad nuruzzaman, farah fazira binti kamaruzaman, and nasrah binti mohd azmi received: 06 october 2016 accepted: 07 december 2016 published: 20 december 2016 publisher: deer hill publications © 2016 the author(s) creative commons: cc by 4.0 abstract in this study, aluminium-aluminium oxide (al-al2o3) metal matrix composites of different weight percentage reinforcements of aluminium oxide were processed at different sintering temperatures. in order to prepare these composite specimens, conventional powder metallurgy (pm) method was used. three types specimens of different compositions such as 95%al+5%al2o3, 90%al+10%al2o3 and 85%al+15%al2o3 were prepared under 20 ton compaction load. then, all the specimens were sintered in a furnace at two different temperatures 550 o c and 580 o c. in each sintering process, two different heating cycles were used. after the sintering process, it was observed that undistorted flat specimens were successfully prepared for all the compositions. the effects of sintering temperature and weight fraction of aluminium oxide particulates on the density, hardness and microstructure of al-al2o3 composites were observed. it was found that density and hardness of the composite specimens were significantly influenced by sintering temperature and percentage aluminium oxide reinforcement. furthermore, optical microscopy revealed that almost uniform distribution of aluminium oxide reinforcement within the aluminium matrix was achieved. keywords: aluminium-aluminium oxide, metal matrix composite, density, hardness, microstructure 1. introduction in recent years, particle reinforced metal matrix composites (mmcs) are gaining popularity for advanced applications. generally, in processing of a metal matrix composite, a soft metal with high ductility and toughness is reinforced by a hard ceramic material with high strength and modulus. these metal-ceramic composites are capable of multiple functions in diverse engineering fields. for structural applications, aluminium based metal matrix composites have significant potential due to their high stiffness, modulus, specific strength, corrosion and wear resistance. in the development of these mmcs, substantial progress has been achieved so that these composites can be used for potential applications such as in automotive and aerospace industries. researchers reported that these metal matrix composites are suitable for high performance structures and showed improved properties over conventional metals and alloys [1-4]. friction and wear behaviors of a359-20 vol% sic particle composites slid against automobile friction material were experimentally investigated [5]. it was found that the wear resistance of the composites was greatly related to the strength and hardness of the sic particles. fatigue lives of aluminium alloy-alumina silicate particulate composites were investigated [6] and it was found that these composites showed longer fatigue lives in lower stress state than the unreinforced aluminium alloy whereas at elevated stress state, these composites exhibited reduced fatigue lives regardless of the reinforcement fractions. the properties of mmcs depend on many factors such as different properties of matrix material, size, shape, hardness, volume fraction and distribution of the reinforcement etc. [7]. thermal conductivity and microstructure of the aluminium oxide particulate reinforced aluminium composites were investigated [8]. the obtained results revealed that the thermal conductivity of the composites was significantly influenced by the volume fraction of aluminium oxide. mechanical properties of silicon carbide particulate dispersed composites were investigated [9] and it was found that due to the addition of silicon carbide particulates, hardness and sliding wear resistance properties were improved. microstructure and properties of zinc oxide whiskers reinforced aluminium based composites were investigated [10]. the obtained results revealed that composite properties were effect of sintering temperature on the properties of aluminium-aluminium oxide composite materials 60 greatly influenced by the reinforced zinc oxide. the influence of different weight fractions of silicon carbide particulate reinforcement on the properties of aluminium based metal matrix composites were investigated [11]. the obtained results revealed that hardness and impact strength of the composites were significantly influenced by the weight fraction of silicon carbide. in this study, aluminium was used as matrix material and aluminium oxide was used as reinforced material for the preparation of mmc. in the fabrication, aluminium-aluminium oxide composite specimens containing 5%, 10% and 15% weight percentages of aluminium oxide particulates were prepared under 20 ton compaction load. after that, all the specimens were sintered at two different sintering temperatures 550 o c and 580 o c using two heating cycles. the effects of sintering temperature and weight fraction of aluminium oxide particulates on the properties of al-al2o3 composites were investigated. the properties such as hardness, density and microstructure of the composites were analyzed. 2. experimental in processing of the aluminium-aluminium oxide (al-al2o3) composite specimens, conventional powder metallurgy (pm) method was used. for the processing of composites, aluminium powders were used as matrix material and aluminium oxide particulates were used as reinforcement. in the fabrication process, 5%, 10% and 15% weight fractions of aluminium oxide powder materials were added to 95%, 90% and 85% weight fractions of aluminium powder respectively to prepare three types of composite specimens. in order to process the specimens, the major three steps are blending, compacting and sintering. at the beginning, on the basis of molecular weight, the weights of aluminium and aluminium oxide powders were measured. in order to achieve a good homogeneous mixture, mixing and blending of metal and ceramic powders were carried out so that ceramic al2o3 particulates are uniformly distributed into the aluminium matrix. a cylindrical steel die was used for the cold compaction of mixed al-al2o3 powders of different compositions. the mixed powders were cold compacted at room temperature using a hydraulic press (toyo: model tl30, capacity 30 ton). all the composite specimens were prepared under 20 ton compaction load. at this stage, these green compacts are very fragile and the cohesive strengths of these green compacts are very low. after that, these green compact specimens were sintered using a sintering furnace (nabertherm: made in germany). two heating cycles were applied during the sintering process. in the first cycle, the temperature started from about 30 o c and with a heating rate of 5 o c/min, it reached to 400 o c. at this temperature, a holding time of 30 minutes was maintained. during the second cycle, with a heating rate of 5 o c/min, the temperature started from 400 o c which reached to sintering temperature 550 o c and a holding time of 1 hour 30 minutes was maintained. at the last stage of sintering, the specimens were allowed to cool in the furnace in order to reach the room temperature. same processes were followed for another set of specimens of different compositions and all the specimens were sintered at a different temperature 580 o c. after completing the sintering process, all the samples were prepared for characterization and hardness testing. using a metallurgical microscope (olympus bx51m, made in japan), microstructural analyses of the samples were carried out. vickers hardness measurements of the samples were carried out using microvickers hardness tester (wilson hardness: model 402 mvd, made in usa). for the microvickers hardness measurement of the specimens, standard test method was followed according to astm e384 standard. in order to measure the hardness, the specimens were cut along the transverse direction. then the specimens were prepared for cold mounting. vickers hardness (hv) was measured under test load of 300 gf (2.94 n) along the longitudinal axis of the test specimen. for each sample, 10 measurements were taken with an interval of 1 mm to avoid any effect by the neighbouring indentations, and the average value of these hardness measurements was taken into consideration. 3. results and discussion the influence of the weight percentage of aluminium oxide reinforcement on the density of aluminium-aluminium oxide composite specimens before and after the sintering process is shown in figure 1. these specimens were prepared under 20 ton compaction load and at sintering temperature 550 o c. the measured densities are shown for 5%, 10% and 15% weight fractions of aluminium oxide in the composites. before the sintering process, aluminium-aluminium oxide composites containing 5, 10 and 15 weight% of al2o3 particulates exhibited densities 2.5, 2.52 and 2.55 g/cm 3 respectively. on the other hand, after sintering process, aluminium-aluminium oxide composites containing 5, 10 and 15 weight% of al2o3 particulates exhibited densities 2.54, 2.55 and 2.6 g/cm 3 respectively. from these obtained results, it is very clear that the density of the composite increases with the increased al2o3 particulate weight fraction, after the sintering process, the density of the composites increases 1.6, 1.19 and 1.96% due to the content of aluminium oxide particulate weight fraction 5, 10 and 15% respectively. figure 2 also shows the densities of aluminium-aluminium oxide composites of different percentage compositions before and after the sintering. in this case, all the specimens were prepared under 20 ton compaction load and at sintering temperature 580 o c. the obtained results show that before the sintering process, the measured densities of the composites containing 5, 10 and 15 weight% of al2o3 particulates are 2.47, 2.52 and 2.55 g/cm 3 respectively. on the other hand, after the sintering process, the measured densities of the composites are 2.59, 2.66 and 2.69 g/cm 3 for the 5, 10 and 15 weight% of al2o3 particulate contents respectively. the effect of al2o3 particulate weight fraction on the density variation of the composite was studied and the density increases 4.86, 5.55 and 5.49% for the 5, 10 and 15 weight% of al2o3 respectively. it can be understood that in general, the densities of the composites nuruzzaman et al., (2016): international journal of engineering materials and manufacture, 1(2), 59-64 61 are higher for 580 o c sintering temperature than the densities obtained for 550 o c sintering temperature. furthermore, as a comparison of these results with the results obtained for 550 o c sintering temperature (figure 1), it is certainly clear that in this case (figure 2), the percentage increase in the density of the composites is somewhat more than that of the sintered al-al2o3 composites prepared at 550 o c and containing three different weight fractions of al2o3. figure 1: density variations for different percentage compositions of aluminium-aluminium oxide composites before and after sintering (sintering temperature: 550 o c) figure 2: density variations for different percentage compositions of aluminium-aluminium oxide composites before and after sintering (sintering temperature: 580 o c) effect of sintering temperature on the properties of aluminium-aluminium oxide composite materials 62 variations in hardness of aluminium-aluminium oxide composites containing 5, 10 and 15% weight fractions of aluminium oxide are shown in figure 3. these composites were prepared under 20 ton compaction load and at sintering temperature 550 o c. microvickers hardness testing was carried out under a test load of 300 gf (2.94 n) for these al-al2o3 composite specimens. all these hardness measurements were made along the depth of the specimen and the measured average values of vickers hardness of the composites are 22.6, 23.5 and 24.8 hv, containing 5, 10 and 15 weight% of al2o3 particulates respectively. it is apparent that due to the increase in the weight fraction of al2o3 reinforcement, an increase in the hardness of al-al2o3 composites occurred. the obtained results reveal that the increase in average hardness of the composite is about 3.9% and 9.7% for 5% and 10% increase in the al2o3 weight fraction respectively. figure 3: hardness variations for different percentage compositions of aluminium-aluminium oxide composites (sintering temperature: 550 o c). variations in hardness of aluminium-aluminium oxide composites are also shown in figure 4. in this case, the composites were processed at sintering temperature 580 o c. the measured average values of vickers hardness of the composites are 24.2, 25.5 and 26.7 hv for the 5, 10 and 15 weight% of al2o3 particulates respectively. the average hardness increased by 5.8% and 10.3% due to the increase in 5% and 10% al2o3 weight fraction respectively. it is believed that due to high hardness of al2o3 and stronger interfacial bonding between al matrix and al2o3 particulates at higher sintering temperature, the improvement in the hardness of the al-al2o3 composites occurred. moreover, as a comparison of these hardness results with the results obtained for sintering temperature 550 o c (figure 3), it is indeed clear that in this case (figure 4), due to the higher sintering temperature, the average hardness of al-al2o3 composites of all the compositions is somewhat higher than that of the composites prepared at sintering temperature 550 o c. figures 5(a)-(c) show the optical microscopy of al-al2o3 composites of different compositions prepared at 550ºc sintering temperature. in the photomicrographs, the blackish part is the al2o3 particulates while the whitish part is the aluminium matrix. the micrograph shows reasonably good distribution of al2o3 particulates in the aluminium matrix. it is believed that during the fabrication process, good interfacial bonding was achieved between al matrix and al2o3 particulates. from the figures, it is apparent that the sharpness of the microstructure is good. figures 6(a)(c) show the microstructure of al-al2o3 composites of different compositions prepared at 580ºc sintering temperature. in the micrograph, the whitish part is the aluminium matrix and the blackish part is the al2o3 particulates. these micrographs indicate nearly uniform distribution of the al2o3 particulates in the aluminium matrix. moreover, it is apparent that the sharpness of the microstructure is quite strong. it is strongly believed that strong particle-matrix interfacial bonding was achieved during processing of the samples at higher sintering temperature. these results are supported by the measured hardness in figure 4. as a comparison, these al-al2o3 composites prepared at 580ºc show somewhat improved microstructure than the composites prepared at 550ºc (figure 5). nuruzzaman et al., (2016): international journal of engineering materials and manufacture, 1(2), 59-64 63 figure 4: hardness variations for different percentage compositions of aluminium-aluminium oxide composites (sintering temperature: 580 o c) figure 5: microstructure at 550ºc (a) 95% al + 5% al2o3 (b) 90% al + 10% al2o3 (c) 85% al + 15% al2o3 figure 6: microstructure at 580ºc (a) 95% al + 5% al2o3 (b) 90% al + 10% al2o3 (c) 85% al + 15% al2o3 a b c a b c 100 µm 100 µm 100 µm 100 µm 100 µm 100 µm effect of sintering temperature on the properties of aluminium-aluminium oxide composite materials 64 4. conclusion in this study, the effects of sintering temperature and weight fraction of al2o3 particulates on the properties of alal2o3 composites were investigated. it was observed that density of composite specimen increases with the increase in al2o3 weight percentage in al-al2o3 composite. hardness of the composite specimen also increases with the increase in al2o3 percentage in al-al2o3 composite. moreover, it was observed that density, hardness and microstructure of the composites were significantly influenced by the sintering temperature. al-al2o3 composites showed higher density and hardness when these composites were processed at sintering temperature 580 o c as compared to the composites that were processed at 550 o c. due to the improved particle-matrix interfacial bonding at higher sintering temperature, the composite showed better properties. as a result, the composites showed improved microstructure at 580 o c as compared to the composites that were processed at 550 o c. acknowledgements the authors wish to thank university malaysia pahang for the financial support through research grant rdu130350. the authors also wish to extend their sincere thanks to all the technical staffs involved to complete this research work. references 1. lees, j. k., dhihra, a. k., & mccullough r. l. (2005) composite materials, wiley. 2. chawla, k. k. (2013) composite materials: science and engineering – springer. 3. veeresh, k. g. b., rao, c. s. p., & selvaraj, n. (2011). mechanical and tribological behavior of particulate reinforced aluminum metal matrix composites – a review. journal of minerals & materials characterization & engineering, 10(1), 59–91. 4. mahendra, b. m., arulshri k. p., & iyandurai, n. (2013). evaluation of mechanical properties of aluminium alloy 2024 reinforced with silicon carbide and fly ash hybrid metal matrix composites. american journal of applied sciences, 10(3), 219-229. 5. daoud, a., & abou el-khair, m. t. (2009). wear and friction behavior of sand cast brake rotor made of a35920 vol% sic particle composites sliding against automobile friction material. tribology international, 43(3), 544-553. 6. arivukkarasan, s., dhanalakshmi, v., suresh babu, a., & aruna, m. (2013). performance study on fatigue behaviour in aluminium alloy and alumina silicate particulate composites. journal of applied science & engineering, 16(2), 127-134. 7. fang, c. k., fang, r. l., weng, w. p., & chuang, t. h. (1999). applicability of ultrasonic testing for the determination of volume fraction of particulates in alumina-reinforced aluminum matrix composites. materials characterization, 43(4), 217-226. 8. tatar, c., & ozdemir, n. (2010). investigation of thermal conductivity and microstructure of the α-al2o3 particulate reinforced aluminium composites (al/al2o3-mmc) by powder metallurgy method. physica b: condensed matter, 405(3), 896–899. 9. dasgupta, r., & meenai, h. (2005). sic particulate dispersed composites of an al–zn–mg–cu alloy: property comparison with parent alloy. materials characterization, 54(4-5), 438-445. 10. guo, z., xiong, j., yang, m., & li, w. (2008). microstructure and properties of tetrapod-like zno whiskers reinforced al matrix composite. journal of alloy and compounds, 461(1-2), 342–345. 11. singla, m., dwivedi, d. d., singh, l., & chawla, v. (2009). development of aluminium based silicon carbide particulate metal matrix composite. journal of minerals & materials characterization & engineering, 8(6), 455– 467. international journal of engineering materials and manufacture (2020) 5(1) 19-28 https://doi.org/10.26776/ijemm.05.01.2020.04 r. e. jonjo and s. t. nyalloma mechanical and maintenance engineering department fourah bay college, university of sierra leone barham road, southern central, 00232 freetown, sierra leon e-mail: sahr.nyalloma@usl.edu.sl reference: jonjo, r. e. and nyalloma, s. t. (2020). modelling the effect of road excitation on vehicle suspension system. international journal of engineering materials and manufacture, 5(1), 19-28. modelling the effect of road excitation on vehicle suspension system robert emmanuel jonjo and sahr tamba nyalloma received: 19 march 2020 accepted: 29 march 2020 published: 30 march 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 abstract the vehicle suspension system serve a dual purpose – to provide passenger comfort and good road holding. in the design of a vehicle suspension system, these two contradictory criteria must be balanced out. road irregularities are also a major source of anxiety amongst drivers and passengers alike. this research was undertaken to investigate the effect road irregularities will have on the vehicle structure especially the suspension system. in this study, the responses of different linear vehicle models are studied for step road input. the mathematical models considered are: a two degrees-of-freedom system (quarter car model) and a four degrees-of-freedom system (half car model). the equations of motion for both models were obtained using newton’s method. these models are analysed using simulink/matlab. different response parameters such as the acceleration of the vehicle body and the travel of the suspension are investigated for a passive suspension system. the responses of the vehicle suspension due to changes in parameters such as suspension stiffness and damping coefficients are investigated. the results show that road irregularities affect the vehicle structures and the response of the suspension system is dependent on the suspension parameters. passive suspension systems do not satisfy road holding and passenger comfort at the same time. 1 introduction the vehicle suspension consists of springs, shock absorbers and other linkages that separates the car body from the car wheel. the functions of the automotive suspension on a vehicle includes; isolating a car body from road irregularities, providing good handling by ensuring that roll and pitch motion are minimized and supporting the vehicle static weight. vehicle suspension system should therefore isolate the vehicle body from road disturbances in order to give maximum passenger ride comfort whiles retaining continuous road-wheel contact so as to provide excellent road holding (changizil and rouhani 2011). it is therefore a challenge to design a vehicle to satisfy both ride comfort and road holding. suspension systems are generally classified as passive, semi-active and active suspensions (ghazaly and moazz 2014, tejas 2016) • passive suspensions: passive suspension systems usually consist of a non-controlled spring and a damper with fixed parameters (agharkakli .a 2012). they lack enough energy absorption capability to sustain the load input into the vehicle systems (gao et al 2016). they lack stability when compared with other suspension systems (dahunsi 2011). • semi-active suspensions: semi active suspensions on the other hand provide a rapid change in rate of springs and damping coefficients. they usually have a fixed spring rate and a variable shock absorber. they do not provide any energy into suspension system. compared to the active suspensions, these suspensions use less energy to operate and they are cheaper (williams 1994). • active suspensions: the active vehicle suspension system employs electronic control systems that monitor the operation of the suspension elements. in active suspension systems, the shock absorber is replaced by a force actuator. they reduce car body accelerations by allowing the suspension to absorb wheel accelerations using an actuator (pedro and ekoru 2013). unlike passive and semi-active suspensions, active suspensions give dynamic compensation (kashem et al. 2012). they are superior in performance than passive and semi-active suspension systems. 2 mathematical modeling the three common vehicle models found in literature are the quarter car model (two degrees of freedom), the half car model (four degrees of freedom) and the full car model (seven degrees of freedom). roll and pitch motions are modelling the effect of road excitation on vehicle suspension system 20 ignored in the quarter car model. a half car model on the other hand considers either roll motion or pitch motion. the full car model considers roll, yaw and pitch motions. 2.1 quarter car model the quarter car model shown in figure 1 is simple and widely used for dynamic performance analysis. it is a two degrees of freedom model. the quarter car model consists of one-fourth of the body mass, suspension components and one wheel. it represents the suspension system at any of the four wheels of the vehicle and the degrees-offreedom are displacement of axle and displacement of the vehicle body at a particular wheel. the assumptions of a quarter car modelling are as follows: • the tire, spring and damper are modelled as a linear spring without damping, • rotational motion in wheel and body are ignored, • the tire remains in contact with the road surface at all times • effect of friction between road and wheel is neglected. consider the free body diagram of the forces acting on the sprung mass as shown in figure 2 with 𝑍𝑠 >𝑍𝑢>𝑍𝑟 .the equation of motion of the sprung mass 𝑀𝑆�̈�𝑆 + 𝐶𝑆(�̇�𝑆 − �̇�𝑈 ) + 𝐾𝑆(𝑍𝑆 − 𝑍𝑈 ) = 0 (i) equation (i) can be rewritten as �̈�𝑠 = 1 𝑀𝑆 { 𝐶𝑆(�̇�𝑢 − �̇�𝑠) + 𝐾𝑆 (𝑍𝑢 − 𝑍𝑠)} (ii) also, the free body diagram of the forces acting on the unsprung mass is shown in figure 3. the equation of motion of the unsprung mass becomes: 𝑀𝑈�̈�𝑈 − 𝐶𝑆(�̇�𝑠 − �̇�𝑢) − 𝐾𝑆(𝑍𝑠 − 𝑍𝑢 ) + 𝐾𝑡 (𝑍𝑢 − 𝑍𝑅 ) = 0 (iii) also, equation (iii) becomes; �̈�𝑈 = 1 𝑀𝑈 {−𝐶𝑆(�̇�𝑢 − �̇�𝑠 ) − 𝐾𝑆(𝑍𝑢 − 𝑍𝑠 ) − 𝐾𝑡 (𝑍𝑢 − 𝑍𝑅 ) (iv) figure 1. quarter car model figure 2. forces acting on sprung mass for quarter car model figure 3. forces acting on the unsprung mass for the quarter car model 2.2 half car model the half car suspension model is a four degree of freedom system shown in figure 4. this model considers both pitch and bounce motion of the vehicle. in this model, the following assumptions are made; • the vehicle undergoes both pitch and bounce motion separately. • the half car model can be a side, front or rear car model depending on the section of the vehicle considered. in this study, the side half car model will be considered. • the tire, springs and dampers are modelled as a linear spring. • the wheel is in contact with the road at all times. jonjo and nyalloma (2020): international journal of engineering materials and manufacture, 5(1), 19-28 21 the free body diagram for both the sprung and unsprung masses with bounce and pitch motion is shown in figures 5 and 6. the equation of motion of the sprung mass exhibiting bounce motion is: 𝑀𝑠�̈�𝑠 + 𝐶𝑠𝑟 (�̇�𝑠 − �̇�𝑢𝑟 − 𝐶𝜃)̇ + 𝐶𝑠𝑓 (�̇�𝑠 − �̇�𝑢𝑓 + 𝑏𝜃)̇ + 𝐾𝑠𝑟 (𝑍𝑠 − 𝑍𝑢𝑟 − 𝐶𝜃) + 𝐾𝑠𝑓 (𝑍𝑠 − 𝑍𝑢𝑓 + 𝑏𝜃) = 0 (v) the equation of motion of the sprung mass exhibiting pitch motion is 𝐼�̈� − 𝐶𝑠𝑟 𝐶(�̇�𝑠 − �̇�𝑢𝑟 − 𝐶�̇�) + 𝐶𝑠𝑓𝑏(�̇�𝑠 − �̇�𝑢𝑓 + 𝑏�̇�) − 𝐾𝑠𝑟 𝐶(𝑍𝑠 − 𝑍𝑢𝑟 − 𝐶𝜃) + 𝐾𝑠𝑓 𝑏(𝑍𝑠 − 𝑍𝑢𝑓 + 𝑏𝜃) = 0 (vi) the equation of motion for both the front unsprung mass and rear unsprung mass are given respectively as, 𝑀𝑢𝑓 �̈�𝑢𝑓 − 𝐶𝑠𝑓(�̇�𝑠 − �̇�𝑢𝑓 + 𝑏�̇�) − 𝐾𝑠𝑓 (𝑍𝑠 − 𝑍𝑢𝑓 + 𝑏𝜃) + 𝐾𝑡𝑓 (𝑍𝑢𝑓 − 𝑍𝑟𝑓 ) = 0 (vii) 𝑀𝑢𝑟 �̈�𝑢𝑟 − 𝐶𝑠𝑟 (�̇�𝑠 − �̇�𝑢𝑟 − 𝐶�̇�) − 𝐾𝑠𝑟 (𝑍𝑠 − 𝑍𝑢𝑟 − 𝐶𝜃) + 𝐾𝑡𝑟 (𝑍𝑢𝑟 − 𝑍𝑟𝑟 ) = 0 (viii) figure 4. half car model figure 5. free body for sprung mass exhibiting bounce motion figure 6. free body diagram for sprung mass exhibiting (pitch motion) 3 simulation 3.1 simulation parameters in the current research vehicle parameters to undertake simulation of the quarter car and half car models were obtained for a passenger sedan as presented by (agostinacchio et al. 2014) and presented in tables one and two respectively. road excitation input is a step signal of amplitude 10 cm. modelling the effect of road excitation on vehicle suspension system 22 3.2 simulation and results the simulink block diagram for the quarter car and half car models are shown in figures 8 and 9 respectively. both figures represent the differential equations of motion for the two models investigated, that is, equations 2 and 4 for the quarter car model and equations 5, 6, 7 and 8 for the half car model. using the parameters presented in tables 1 and 2, simulation of the system models was undertaken and the results presented in graphical format. the displacement of the vehicle body, displacement of the unsprung mass(s), deflection of the wheels, suspension travel, acceleration of the car body in the vertical direction are the parameters that were investigated. the effect of the changes of various passive suspension parameters are investigated by keeping all other system parameters fixed and gradually varying the parameter being investigated. figure 7. free body diagrams for front and rear unsprung mass table 1. simulation parameters for quarter car model parameter symbol values unit sprung mass of the vehicle 𝑀𝑠 400 kg unsprung mass of vehicle 𝑀𝑢 40 kg stiffness of tire 𝐾𝑡 190000 n/m spring constant of axle 𝐾𝑠 21000 n/m damping coefficient of axle 𝐶𝑠 1000 ns/m table 2. simulation parameters for half car model parameter symbol values unit sprung mass of the vehicle 𝑀𝑠 400 𝑘𝑔 moment of inertia of vehicle 𝐼𝑦 1100 𝑘𝑔𝑚 2 unsprung mass of front axle 𝑀𝑢𝑓 40 𝑘𝑔 unsprung mass of rear axle 𝑀𝑢𝑟 40 𝑘𝑔 stiffness of front tire 𝐾𝑡𝑓 150000 𝑁 𝑚⁄ stiffness of rear tire 𝐾𝑡𝑟 150000 𝑁 𝑚⁄ spring constant of front axle 𝐾𝑢𝑓 21000 𝑁 𝑚⁄ spring constant of rear axle 𝐾𝑢𝑟 21000 𝑁 𝑚⁄ damping coefficient of front axle 𝐶𝑠𝑓 1500 𝑁𝑠 𝑚⁄ damping coefficient of rear axle 𝐶𝑠𝑟 1500 𝑁𝑠 𝑚⁄ front body length from centre of gravity 𝑐 1.47 𝑚 rear body length from centre of gravity 𝑏 1.4 𝑚 jonjo and nyalloma (2020): international journal of engineering materials and manufacture, 5(1), 19-28 23 figure 8. simulink block diagram for quarter car model figure 9. simulink block diagram for half car model 3.2.1 simulation for quarter car model the displacement of the sprung and unsprung masses, acceleration of the sprung and unsprung masses, suspension travel and tire deflection are presented in table 3. figures 10, 11 and 12 show the displacement of the sprung mass, acceleration and displacement of the unsprung mass for the quarter car model. modelling the effect of road excitation on vehicle suspension system 24 table 3. simulation results for quarter car model no parameters values maximum sprung mass displacement maximum unsprung mass displacement sprung mass acceleration suspension travel wheel deflection rms acceleration 1 sprung mass 400 0.1569 0.1268 16.776 -2.969 0.050 -0.115 0.0268 -0.100 0.5829 2 500 0.1601 0.1258 13.569 -2.439 0.053 -0.113 0.0258 -0.100 0.472 3 1000 0.1686 0.1238 6.920 -1.329 0.059 -0.1175 0.0238 -0.100 0.253 4 1500 0.1730 0.1231 4.643 -0.923 0.064 -0.1189 0.0231 -0.100 0.178 5 unsprung mass 50 0.1576 0.1309 15.796 -3.436 0.049 -0.1125 0.0309 -0.100 0.582 6 100 0.1584 0.1433 13.045 -5.056 0.051 -0.1161 0.0433 -0.100 0.586 7 150 0.1599 0.1461 11.452 -5.420 0.062 -0.1180 0.0426 -0.100 0.597 8 200 0.1631 0.1539 10.622 -6.335 0.067 -0.112 0.0534 -0.100 0.593 9 suspension stiffness 21000 0.1569 0.1268 16.776 -2.959 0.050 -0.1115 0.0268 -0.100 0.5829 10 30000 0.1646 0.1217 17.858 -4.346 0.054 -0.1059 0.0217 -0.100 0.639 11 40000 0.1709 0.1164 19.010 -5.892 0.055 -0.099 0.0164 -0.100 0.704 12 60000 0.1750 0.1197 20.139 -7.330 0.056 -0.095 0.0197 -0.100 0.791 13 damping coefficient 1500 0.1569 0.1268 16.776 -2.959 0.050 -0.115 0.0268 -0.100 0.5829 14 2000 0.1492 0.1188 18.998 -3.200 0.043 -0.099 0.0188 -0.100 0.659 15 2500 0.1421 0.1120 20.023 -3.195 0.037 -0.091 0.0120 -0.100 0.749 16 3000 0.1381 0.1100 22.478 -3.542 0.038 -0.0828 0.0108 -0.100 0.786 17 tire stiffness 150000 0.1569 0.1268 16.776 -2.959 0.050 -0.1115 0.0268 -0.100 0.5829 18 200000 0.1555 0.1310 19.880 -5.183 0.050 -0.1205 0.031 -0.100 0.629 19 250000 0.1542 0.1388 23.220 -7.252 0.050 -0.1278 0.0388 -0.100 0.680 20 300000 0.1535 0.1439 26.143 -8.821 0.049 -0.1324 0.0439 -0.100 0.747 jonjo and nyalloma (2020): international journal of engineering materials and manufacture, 5(1), 19-28 25 figure 10. displacement of the sprung mass quarter car model figure 11. acceleration of sprung mass quarter car model figure 12. displacement of the unsprung mass modelling the effect of road excitation on vehicle suspension system 26 3.2.2 simulation for half car model the simulation results for the halfcar model is presented in table 4. figures 13, 14 and 15 show the displacement of the sprung mass, and the displacement of the unsprung masses for the half car model. 4 results simulations were carried out for the quarter car and halfcar models. different response properties were investigated such as vehicle sprung mass displacement, unsprung mass displacement, suspension travel, wheel deflection. from the simulation results presented in tables 3 and 4, it is observed that the vehicle experiences a vertical acceleration as it passes over a road irregularity. the following general observations are made from the simulation results. from the simulation results it is evidently clear that an increase in the sprung mass leads to a lower vertical acceleration of the car body, an increase in the vertical displacement of the car body and an increase in the suspension travel. if all other parameters are kept constant whiles the unsprung mass(es) is gradually increased, similar trends are observed as in the case of the sprung mass. vertical acceleration is reduced but suspension travel is increased. increasing damping coefficient reduces car body displacement and suspension travel considerably but vertical acceleration increases whereas an increase in the stiffness of vehicle suspension leads to an increase in vertical acceleration. the suspension travel shows an increase and decrease pattern. figure 13. displacement of sprung mass of half car model figure 14. displacement of front unsprung mass figure 15. displacement of rear unsprung mass modelling the effect of road excitation on vehicle suspension system 27 table 4. simulation results for half car model no parameters values sprung mass displace unsprung mass displacement sprung mass acceleration suspension travel wheel deflection rms accelerat ion front rear front rear front rear 1 sprung mass 400 0.148 0.1299 0.1301 32.034 -10.685 0.0415 -0.1045 0.0416 -0.1046 0.0299 0.030 3.80 2 500 0.151 0.1277 0.1278 26.057 -7.295 0.0443 -0.1074 0.0444 -0.1075 0.0278 0.0278 3.080 3 1000 0.1602 0.1231 0.1235 13.539 -2.434 0.0525 -0.1137 0.0527 -01138 0.0234 0.0236 1.595 4 1500 0.1652 0.1225 0.1226 9.129 -1.697 0.0570 -0.1159 0.0573 -0.1160 0.0225 0.02258 1.102 5 front unsprung mass 50 0.148 0.1361 0.1299 30.318 -10.178 0.0419 -0.1023 0.0421 -0.1055 0.0361 0.0299 3.748 6 100 0.150 0.1485 0.1294 24.453 -7.746 0.0471 -0.0989 0.0434 -0.1080 0.0485 0.0294 3.430 7 150 0.148 0.1567 0.1297 23.178 -10.807 0.0613 -0.0930 0.0424 -0.1100 0.0568 0.0297 3.226 8 200 0.148 0.1607 0.1288 21.392 -12.042 0.0747 -0.0880 0.0438 -0.1110 0.0677 0.0288 3.090 9 rear unsprung mass 50 0.1482 0.1298 0.1360 30.292 -10.172 0.0421 -0.1054 0.0419 -0.1020 0.0298 0.0362 3.748 10 100 0.1501 0.1292 0.1486 25.460 -7.748 0.0432 -0.1087 0.0474 -0.0989 0.0292 0.0486 3.436 11 150 0.1480 0.1295 0.1569 23.179 -10.823 0.0423 -0.1090 0.0613 -0.0939 0.0295 0.0569 3.227 12 200 0.1506 0.1286 0.1609 21.402 -12.052 0.0438 -0.1114 0.0747 -0.0889 0.0286 0.0609 3.090 13 front suspension stiffness 21000 0.1483 0.1299 0.1301 32.034 -10.685 0.0415 -0.1045 0.0416 -0.1046 0.0299 0.0300 3.801 14 30000 0.1523 0.1257 0.1312 32.306 -9.342 0.0421 -0.1000 0.0452 -0.1036 0.0257 0.0312 3.917 15 40000 0.1547 0.1206 0.1315 33.043 -9.524 0.0412 -0.0958 0.0479 -0.1028 0.0206 0.0315 4.056 16 50000 0.1565 0.1200 0.1317 33.924 -10.805 0.0393 -0.0919 0.0506 -0.1023 0.0200 0.0317 4.179 17 rear suspension stiffness 21000 0.1483 0.1299 0.1301 32.034 -10.085 0.0415 -0.1045 0.0416 -0.1046 0.0299 0.0300 3.801 18 30000 0.1521 0.1316 0.1267 32.203 -9.607 0.0449 -0.1014 0.0422 -0.0985 0.03163 0.0267 3.967 19 40000 0.1545 0.1316 0.1212 32.461 -9.477 0.0477 -0.1022 0.0408 -0.0956 0.03164 0.0212 4.071 20 50000 0.1559 0.1317 0.1202 33.609 -10.772 0.0501 -0.1019 0.0389 -0.0919 0.0317 0.0202 4.188 21 front damping coefficient 1500 0.1483 0.1299 0.1301 32.034 -10.085 0.0.415 -0.1045 0.0416 -0.1046 0.0299 0.0300 3.801 22 2000 0.1440 0.1254 0.1318 33.159 -10.669 0.0387 -0.0922 0.0372 -0.1011 0.0254 0.0318 4.102 23 2500 0.1406 0.1230 0.1320 34.671 -11.702 0.0366 -0.0847 0.0336 -0.0997 0.0230 0.0322 4.272 24 3000 0.1375 0.1230 0.1314 35.598 -12.669 0.0349 -0.0800 0.0310 -0.0986 0.0231 0.0314 4.498 25 rear damping coefficient 1500 0.1484 0.1299 0.1300 32.034 -10.685 0.0415 -0.1045 0.0416 -0.1046 0.0299 0.0300 3.807 26 2000 0.1440 0.1317 0.1255 33.148 -10.684 0.0370 -0.1011 0.0387 -0.0922 0.03170 0.0255 4.100 27 2500 0.1405 0.1319 0.1233 34.548 -11.761 0.0335 -0.0995 0.0367 -0.085 0.0317 0.0255 4.274 28 3000 0.0317 0.0319 0.1234 35.656 -12.700 0.0308 -0.0985 0.0350 -0.0802 0.0317 0.0255 4.495 modelling the effect of road excitation on vehicle suspension system 28 5 conclusions in this work the effect of road excitations on a passive suspension for a passenger car was investigated. mathematical modelling has been performed using a two and four degrees of freedom models. the differential equations of motion were simulated with simulink/matlab. the results from the simulation were used to analyse the performance of vehicle dynamics for step input road profile. the following conclusions are drawn. on the basis of the results, it can be concluded that road excitations affect the vehicle suspension which determines the ride comfort and stability of the vehicle. references agharkakli a., ghobad shafiei sabet, armin barouz (2012). simulation and analysis of passive and active suspension system using quarter car model for different road profile. international journal of engineering trends and technology, 3 (5). agostinacchio, m., ciampa d. and olita, s. (2014). the vibration induced by surface irregulation in road pavements– a matlab approach. springer, 6, 267-275. changizi, n. and m. rouhani, (2011). comparing pid and fuzzy logic control of a quarter car suspension system. the journal of mathematics and computer science, 2(3), 559-564. gao, h; xue,s; yin,s; qiu, j; wang c. output feedback control of multirate sampled-data systems with frequency specifications. ieee trans. control syst. technol. 2016 ghazaly, n. m. and a. o. moazz, (2014). the future development and analysis of vehicle active suspension system. iosr journal of mechanical and civil engineering, 11(5), 19-25. kashem,s.b.a; ektesabi, m.; nagarajah, r. comparison between different sets of suspension parameters and introduction of a new modified skyhook control strategy incorporating varying road condition. vehicle systems dynamics. 2012. pedro, j. o. and j. e. d. ekoru (2013). proportional-integral derivative control of nonlinear half-car electro-hydraulic suspension systems. journal of zhejiang university-science a (applied physics & engineering), 14(6), 401-416. turakhia t. p, prof. m. j. modi (2016). mathematical modeling and simulation of a simple half – car vibration model. international journal for scientific research & development, 4(2), 2321-0613. williams r.a, (1994). electronically controlled automotive suspensions. computing & control engineering journal, 5(3), 143-148. list of abbreviations 𝑀𝑠=sprung mass of vehicle 𝑀𝑢𝑓=unsprung mass of front axle 𝑀𝑢𝑟=unsprung mass of rear axle 𝐾𝑢𝑓 =suspension stiffness of front axle 𝐾𝑢𝑟 =suspension stiffness of rear axle 𝐶𝑠𝑓=damping coefficient of front axle 𝐶𝑠𝑟=damping coefficient of rear axle 𝐾𝑡𝑓=stiffness of front tire 𝐾𝑡𝑟 =stiffness of rear tire l=length of wheelbase b=distance to front axle from centre of gravity c=distance to rear axle from centre of gravity ɵ=pitch angle 𝑍𝑟𝑓=road excitation at the front wheel 𝑍𝑟𝑟=road excitation at the rear wheel international journal of engineering materials and manufacture (2019) 4(3) 116-123 https://doi.org/10.26776/ijemm.04.03.2019.04 y. m. ahmed 1 , h. d. lafta 1 , a. a. a. rahman 1 and b. t. salih 2 1 department of mechanical engineering technical college of engineering sulaimani polytechnic university kurdistan region, sulaimani, iraq 2 department of mechanical engineering sulaimani technical institute kurdistan region, sulaimani, iraq e-mail: azhin.abdallah@spu.edu.iq reference: ahmed, y. m., lafta, h. d., rahman, a. a. a and salih, b. t. (2019). experimental study of the performance of base metal and welding line of the household lpg cylinder manufactured in kurdistan region. international journal of engineering materials and manufacture, 4(3), 116-123. experimental study of the performance of base metal and welding line of the household lpg cylinder manufactured in kurdistan region yassin mustafa ahmed, hameed d. lafta, azhin abdullah abdul rahman and barzan talib salih received: 06 september 2019 accepted: 13 september 2019 published: 27 september 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract liquefied petroleum gas (propane or butane) is a colourless liquid which readily evaporates into a gas. it has no smell, although it will normally have an odour added to help detect leaks. liquefied petroleum gas is stored and handled as a liquid when under pressure inside an lpg cylinder. liquefied petroleum gas cylinders are subjected to various tests to ensure their compliance requirements as per standard. this research studies the durability of welding and performance of base metal of lpg. home cylindrical in kurdistan region. the experiments were carried out on three types of lpg cylinder using in kurdistan regions a, b, and c and an unformed plate. to carried out the samples and tests during the research we depending on the standard tests for lpg cylinders. three samples are extracted from each of lpg cylinders and unformed plate for each of tensile test, bending test and hardness test according to iso 6892-2016 and asme standards from each type of lpg cylinders and from unformed plate to examine the mechanical properties. in addition, chemical compositions also were carried out. these values are compared with standard. keywords: lpg, astm, asme, iso, bs 5045, lpg cylinder, pressure vessel, welding 1 introduction liquefied petroleum gas (lpg) is a colourless liquid which readily evaporates into a gas. it has no smell, although it will normally have an odour added to help detect leaks. when mixed with air, the gas can burn or explode when it meets a source of ignition. it is heavier than air, so it tends to sink towards the ground [1]. lpg is composed predominantly a mixture of hydrocarbons such as propane, propylene, butane or butylene. the gas can be liquefied at moderate pressure, and can be stored in cylinders as a liquid under pressure and is drawn out and used as gas. this means that it can be transported and stored as liquid and burnt as gas. the expansion ratio of gas liquid is 270:1 at atmospheric pressure. the expansion factor makes lp-gas more economical to transport and stored with large quantities of gaseous fuel in a small container .containers are normally filled 80-85% liquid, leaving 15-20% vapour space for expansion due to temperature increase. the household gas cylinder weighs approximately 14 kg. nowadays, composite materials have been used widely which are proved to be more effective. these composite materials are wound over metal liner thus acting as over wrapped composite pressure vessel. lpg cylinder is one kind of pressure vessel that stores pressurized gases. lpg cylinder material should have high tensile and compressive strength for withstanding the high pressure of the gases [2]. the cylinders play a crucial role in containing and transporting hazardous lpg from filling plant to end consumer [3]. lpg cylinders are to be manufactured from definitely prescribed raw material to ensure safety of cylinders through material quality specifications [4]. although there are clear standards and statutory norms for design, http://spu.edu.iq/en/1377 mailto:azhin.abdallah@spu.edu.iq ahmed et al. (2019): international journal of engineering materials and manufacture, 4(3), 116-123 117 manufacturing and usage of cylinders, there are certain gaps in these standards in terms of ensuring material safety compliance. lpg cylinder production is composed of several sheet metal forming, surface treatment and testing processes. the process starts with blanking, deep drawing and piercing, trimming and joggling. next are the welding operations for valve boss, valve guard ring, foot ring and the two halves. the finished cylinder is then heat treated, tested, shot blasted, painted and then the valve is attached and tested finally [5]. the main steps involved in manufacturing process of lpg cylinders are shown in figure 1. figure 1: the process of manufacturing of lpg cylinders (bhadur and marg, 2008). 2. literature review liquefied petroleum gas (lpg) cylinders that have an important position from the point of use have been taken into consideration, so, many researches have made by researcher as explained below. nihal a. siddiquia, et al. (2013) investigated a study on the welded low-carbon steel cylinders exceeding 5 litres of water capability which are produced and tested as per indian standard (is 3169). ramakrishna, siddiqui and sojan (2013) conducted several tests on lpg cylinders, in which acceptance test is one of the important tests to reveal cylinder parent metal mechanical properties. two tensile specimens are prepared from finished cylinder batch for this test and tested on a universal testing machine to determine, yield strength, percentage elongation and ultimate tensile strength of parent metal. values of these test results are compared against standard values prescribed in indian standards to decide acceptance of cylinder batch for market release. mahmud, et al. (2017) study the effect of annealing temperature on the mechanical properties of sg 255 steel. experimental study of the performance of base metal and welding line of the household lpg cylinder 118 the sg 255 steel is used in manufacturing of domestic lpg cylinder in kurdistan region. furthermore their work aims to obtain experimentally better mechanical properties at particular ductility with lower annealing temperature and to minimize the cost of the manufacturing of lpg cylinders. a number of samples were made according to iso 6892, and then heat treated with different annealing temperature (850, 900 and 950 ºc). moreover, the tensile tests of these samples were carried out until failure to obtain the mechanical properties. it was shown that higher elongation percentage 34.18% with an annealing temperature 900 ºc can be achieved, and this leads to minimize the cost of manufacturing of the cylinders without degrading of their quality. y. li, and f. wang (2019) was proposed an integral manufacturing process with hot drawing and cold flow forming for large diameter seamless steel gas cylinders. the primary aim of this research was to find out the impacts of the manufacturing method on gas cylinders made of 34crmo4 steel's microstructure and mechanical characteristics. two preformed cylinders were produced by hot drawing. one cylinder was then further manufactured by cold flow forming. the experiments were carried out using three types of material sample, namely, base material (bm), hot drawing cylinder (hd), and cold flow-formed cylinder (cf). tensile and impact tests were performed to examine the mechanical properties of the cylinders in longitudinal and transverse directions. microstructure evolution was analysed by scanning electron microscopy (sem) and electron backscatter diffraction (ebsd) to reveal the relation between the mechanical properties and the microstructure of the material. it is found that the mechanical properties of the 34crmo4 steel gas cylinders were significantly improved after hot drawing and flow forming plus a designed heat treatment, compared with the base material. the observations of microstructure features such as grain size, sub grain boundaries, and residual strain support the increase in mechanical properties due to the proposed manufacturing process. in this study, an unformed plate and the sheet materials of liquefied petroleum gas (lpg) cylinders that have an important position from the point of use have been taken into consideration. the household lpg cylinders can be divided in to two main groups, the first group imported by the central government and the second group locally produced in the kurdistan region from different companies and different cities. a group of specimens were taken from the unformed plate and base metal of the cylinders, while another one were taken across the cylinders from the weld zone transversely in the middle of the cylinders, which had the same initial thickness of 3 mm. note that effect of geometric discontinuities due to weld toe was eliminated since the thickness of entire samples was kept constant. different test results are compared against standard. table 1: mechanical properties of lpg cylinders [10] mechanical properties of lpg cylinders value minimum yield strength 240 n/mm2 tensile strength 360-430 minimum elongation 30 % table 2: chemical composition of lpg cylinders [10] chemical composition % max c 0.16 mn 0.50 si 0.20 p 0.03 s 0.03 3. materials the material of the lpg cylinders and unformed plate is low alloy carbon steel with 3mm thickness. the mechanical and chemical composition required according to bs 5045 [10] are given in tables 1 and table 2 respectively. 4. methodology 4.1 chemical composition analysis of lpg cylinder: to achieve this study, we used three of lpg cylinder from different company and different cities (b, c, d), and an unformed plate (a) to making the specimens. to distinguish between the lpg cylinders, and also to mention the name of the companies or cities are indicated by letters. the letter (a) is the mentioned to the unformed plate, (b) is the letter for the first cylinder, (c) is the letter for the second cylinder and (d) is the letter for the third cylinder. the chemical compositions examination of the test specimens was achieved by spectrometry instrument see figure 2. it is also the results of chemical composition are shown in table 3. from the above chemical compositions of cylinders and unformed plate from table 3 it can be seen that the contents of all elements, except for silicon and manganese in all samples were nearly same. sample (b) had somewhat lower silicon content and higher manganese content than the other samples, since all cylinders came from different production batches and thus likely from different raw steel sheet. with respect to the investigations of this work this small deviation could be omitted. however, all the chemical contents of all cylinders and unformed plate were in the acceptable range of the standard of steel grades used for lpg cylinder except manganese. ahmed et al. (2019): international journal of engineering materials and manufacture, 4(3), 116-123 119 4.2 tensile test the investigated lpg cylinders were manufactured by using deep drawing process from two low carbon steel plate with dome shape and an intermediate cylinder, which were subsequently welded together along the peripheral direction (figure 1). microstructure and mechanical behaviour of the welding line were differed from the base low carbon steel and could considerably affect the structural integrity and performance of lpg cylinder. tensile testing was carried out at room temperature (23c°) as per iso 6892-2016 [11]. the tensile test specimens with the gauge length of 50 mm were prepared from the sidewall of cylinders in the longitudinal direction. a group of specimens was taken from the base metal, while another one was taken across the cylinders and had the weld zone transversely in the middle according to asme section ix 2013 [12]. as shown in figure 3 and figure 4. note that the effect of geometric discontinuities due to weld toe was eliminated since the thickness of entire samples was kept constant. the tensile tests were carried out on a universal testing machine as shown in figure 5. the achieved mechanical properties such as yield strength, tensile strength and elongation of the base metal and weld area of the specimens were presented in tables 4, and table 5. table 3: chemical composition of lpg cylinders and unformed plate sample c % si % mn % p % s % a 0.129 0.192 0.92 <0.0005 <0.0005 b 0.119 0.082 1.05 <0.0005 0.0054 c 0.135 0.163 0.926 0.0005 0.0030 d 0.124 0.181 0.966 <0.0005 0.0034 figure 2: chemical composition of samples figure 3: tensile test samples (weld metal) experimental study of the performance of base metal and welding line of the household lpg cylinder 120 figure 4: tensile test samples (base metal) figure 5: tensile test machine table 4: the tensile test results of the cylinders and unformed plate (base metal) sample ultimate strength (mpa) yield strength(mpa) elongation a 456.86 325.56 33.8 b 389.86 249.33 28.8 c 417.2 283.33 25.9 d 447.4 304 28.53 standard (360-430) min (240) min (30)% table 5: the tensile test results of the cylinders on welded area sample ultimate strength (mpa) yield strength(mpa) elongation b (tensile shear strength) 361.9 306 47.8 b (asme) 405.5 310 28.3 c ( asme) 447.8 310 35 d ( asme) 434.7 305 35.5 standard (360-430) min (240) min (30)% by observing the tensile test results, we found that the unformed metal (sample a) and sample (d) exhibited highest yield and tensile strengths whereas sample (b) had lower ultimate and yield strength while its elongation similar to sample (d) and higher than of sample (c). furthermore the yield and tensile strengths of sample (c) were greatly higher than those of sample (b) while the elongations of sample (c) much decreased as compared to sample (a). it is ahmed et al. (2019): international journal of engineering materials and manufacture, 4(3), 116-123 121 obvious that the tensile properties especially the elongation of sample b, c, d were little different from bs50445 standard [13] and the yield stress is higher than 240 mpa in all cases; all gas cylinders are within the range of bs5045 standard however, the ultimate strength of sample (a), (d) are greater than that of the standard as shown in the table 4. it is concluded that the subsequent forming process does not cause significant changes in the mechanical properties of the material after heat treatment. on the other hand, from table 5 it can be seen that sample (c) and sample (d) exhibited high ultimate tensile strengths and yield strength with similar elongation whereas sample (b) had lower ultimate tensile shear strength while its elongation higher than of those samples. furthermore the elongation of sample (b) was greatly lower than those of the other samples. it is obvious that the tensile properties especially the elongation of sample b, c, and d were little different from bs50445 standard and the yield stress is higher than 240 mpa in all cases; all gas cylinders are within the range of bs5045 standard however, the ultimate strength of sample (a), (d) is are greater than that of the standard as shown in the table 5. it is appearing that the material of the cylinders exhibits good ductility. 4.3 hardness test the preparation of hardness test samples has carried out with an appropriate cutting method, which involves selecting the correct cutting tool with using a cooling liquid to avoid the samples from burning and distortion. to cut and prepare the specimens for the hardness exam, a milling machine process with cooling liquid was used as shown in figure 6. after cutting, the samples were grinded and polished in order to prevent any scratches and to accomplish right reading. the vickers hardness testing was carried out for different locations of the sample face, as shown in figure 7, to check the consistency and uniformity of the properties. the micro-hardness testing was carried out as per astm a384 [13]. diamond indenter (pyramid) with face angle of 136° was used. during testing (1kg) load was applied on sample with dwell time of 15 seconds, and both the diagonals of pyramid indenter (d1 and d2) were measured with microscope at a magnification of 500x. the results of the hardness tests have shown in the table 6. the average hardness results revealed that the values of (sample d) offered the highest value as compared to other samples while sample (c) shows the lower result as compared to others. figure 6: cutting process of lpg cylinders figure 7: hardness test samples table 6: results of the average hardness test sample average vickers hardness (kg/mm2) sample (a) 147.24 sample (b) 153.28 sample (c) 142.7 sample (d) 162.66 experimental study of the performance of base metal and welding line of the household lpg cylinder 122 4.4 bending test bending test is a one of an important test that standard required to achieve. this test achieved perpendicular to the weld zone which has been bent through angle180°. bending tests for ductility provide a simple way to evaluate the quality of materials by their ability to resist cracking or other surface irregularities during one continuous bend condition. the bending tests were carried out in accordance with aws standard [14] for all three lpg cylinders to evaluate their welding qualities. the results of such a test obtained by the same tensile machine, the bending test samples and machine has shown in figures 8, 9, and 10. the bending test results showed that the samples were bent at 180 degrees without breaking or cracking in the samples. this means that the samples met the requirements of the standards. the ductility of weld was satisfactory and there are no defects in the welding joints for all samples. figure 8: prepared bending test samples figure 9: bending test sample figure10: bending test machine ahmed et al. (2019): international journal of engineering materials and manufacture, 4(3), 116-123 123 5. conclusions from the above study, the following points can be concluded based on the results of tensile, hardness, bending tests, and chemical composition: 1. all the chemical contents of all cylinders and unformed plate were in the acceptable range of the standard of steel grades used for lpg cylinder except manganese. 2. the tensile properties of the unformed plate and base metal of the lpg cylinders were show little different from bs50445 standard and they are in the acceptable range. 3. the ultimate tensile strength, yield strength and elongation of the weld metal of the lpg cylinders are nearly similar according to asme standard. 4. it is clear that from the results that average hardness values of sample (d) have recorded greatest value as compared with other samples. 5. bending results showed that there was no development of crack was noticed during the bending test. acknowledgement the authors acknowledged the support from technical staff from mechanical engineering department at sulaimani polytechnic university for their support in carrying out this research work. references 1. chandrakar, a. t. a. k. m. (2017). design and analysis of a composite cylinder for the storage of liquefied gases, international journal for scientific research & development, 5(3). 2. kiran, c. s. and sruthi, j. (2018) design and finite element analysis of domestic lpg cylinder using ansys workbench. cvr journal of science and technology, 14, 97-101. 3. mulla, n., k. bicha (2015). design and stress analysis of pressure vessel by using ansys., international journal of engineering sciences & research technology, 4(7), 578-585. 4. akula, r., siddiqui, a. n., and sojan l. p. (2013). review of liquefied petroleum gas (lpg) cylinder life cycle. international journal of advanced engineering technology, iv, 124-127. 5. bhadur, s. z. and marg, m. b. (2008). hot rolled steel plate up to 6 mm sheet and strip for the manufacture of low pressure liquefiable gas cylinders. wrought steel products sectional comitte, 1–8. 6. nihal a. siddiquia, akula ramakrishna, p. sojan lalc, (2013). review on liquefied petroleum gas cylinder acceptance test as per indian standard, is 3196 (part 3): 2012. international journal of advanced engineering technology, iv, 119-123. 7. s. l, ramakrishna and siddiqui (2013). impact of sample preparation methods on impact of sample preparation methods on liquefied petroleum gas cylinder parent metal liquefied petroleum gas cylinder parent metal tensile. journal of engineering research and studies, 12–15. 8. f. j. mahmud, k. m. abdulrahman, h. j. muhammed and b. a. h. seed (2017). the influence of annealing temperature and soaking time on the ductility of sg 255. kurdistan journal of applied research (kjar), 2(3), august. 9. y. li, w. fang, c. lu, z. gao, x. ma, w. jin, y. ye (2019). wang microstructure and mechanical properties of 34crmo4 steel for gas cylinders formed by hot drawing and flow forming materials, 1-1. 10. british standard (bs5045: part 2:1978) specification standard for transportable gas containers. 11. iso 6892: metallic materials tensile testing part 1: method of test at room temperature 2016. 12. asme boiler and pressure vessel code – ix, 2013. 13. astm 384: test method for micro indentation hardness of materials, 2011. 14. aws, welding handbook, (1998): welding technology, eighth edi. aws, american welding society, vol. 1. international journal of engineering materials and manufacture (2016) 1(1) 27-34 https://doi.org/10.26776/ijemm.01.01.2016.06 riza, m1. and adesta, e.y.t1, 2 1faculty of engineering, international islamic university malaysia, kuala lumpur 53100, malaysia 2agile and sustainable manufacturing research unit (asmaru) e-mail: eadesta@iium.edu.my reference: riza, m., & adesta, e.y.t. (2016). investigation of cutting temperature for aisi h13 in high speed end milling. international journal of engineering materials and manufacture, 1(1), 27-34. investigation of cutting temperature for aisi h13 in high speed end milling muhammad riza and erry y. t. adesta received: 15 september 2016 accepted: 27 september 2016 published: 03 october 2016 publisher: deer hill publications © 2016 the author(s) creative commons: cc by abstract heat produced at the tool-chip interface during high speed milling operations have been known as a significant factor that affect to tool life and workpiece geometry or properties. this paper aims to investigate cutting temperature behaviours of aisi h13 (48 hrc) under high speed machining circumstances during pocketing. the experiments were conducted on cnc vertical machining centre by using pvd coated carbide insert. milling processes were done at cutting speeds 150, 200 and 250 m/min and feed rate were 0.05, 0.1 and 0.15 mm/tooth. depths of cut applied were 0.1, 0.15 and 0.2 mm. tool path method applied in this experiment was contour in. results presented in this paper indicate that by increasing cutting speed the cutting temperature is lower than low cutting speed. however, by decreasing feed rate leads to cutting temperature low. cutting temperature phenomena at the corner of pocket milling were also investigated. the phenomena showed that cutting temperature tends to decrease a moment when cutter comes to the corner of pocket and turning point of tool path and increase extremely a moment before leaving the corner and turning point. keywords: cutting temperature, tool path, aisi h13, high speed end milling, pocketing 1 introduction end milling is a basic machining operation in the manufacture of mechanical components to generate a flat surface and/or a three-dimensional free-formed surface; it requires high geometric accuracy and high productivity. during the machining, most of the power consumed for plastic deformation is converted into heat, and high temperatures are generated. high temperature is claimed to cause several types of thermal damage to the cutting tool and workpiece, such as rapid tool wear and thermal expansion of the workpiece [1]. to clarify the influence of temperature on the thermal damage and to select appropriate cutting conditions, good understanding of milling temperatures is required. since end milling is an intermittent machining process, the cutting tool is depending on cyclical heating and cooling, and temperature variation in the cutting tool is more complicated than in turning. the achievement of these objectives by high speed end milling places it at the front line of rapid tooling and manufacturing technologies. one of the important parameters to optimize cutting conditions is cutting temperature during milling of inconel 718. this conditions is applicable for dry machining of difficult-to-cut materials. the thermocouple should be placed as close as possible to the cutting zone to get accurate measurement result [2]. among three cutting parameters, cutting speed was claimed as the most influence parameter in temperature rise. it was found that between two temperature devices used during the experimental work, infrared pyrometer generated higher cutting temperature reading than embedded thermocouple. it is due to the ability of infrared pyrometer records all factors involved (workpiece, cutting tool and especially chips temperature) during machining operation [3]. the increase of machining parameters such as cutting speed and feed rate implicate increase of cutting temperature during end milling of al 6063. it was found that the relation between feed rate and depth of cut are significant [4]. depth of cut is claimed as the most influential factor affect to surface temperature during machining of aisi 1020 medium carbon steel. surface roughness increases as feed rate increased and such condition leads to workpiece temperature decreases. a better surface quality can be achieved in higher cutting temperature condition http://www.refdoc.fr/?traduire=en&formrechercher=submit&formrechercher_txt_recherche_name_attr=auteursnom:%20%28mohammed%29 http://www.refdoc.fr/?traduire=en&formrechercher=submit&formrechercher_txt_recherche_name_attr=auteursnom:%20%28mohammed%29 investigation of cutting temperature for aisi h13 in high speed end milling 28 during machining. cutting temperature in this research can be used as a predictor of cutting performance [5]. the higher negative angles of tool holder is, the higher cutting force becomes. simultaneously, cutting temperature rises in line with the rises of cutting force. it causes tool wear occurred rapidly and effect to reduction of cermet inserts life [6]. dr. carl salomon [7] in 1931 revealed that there is a specific cutting speeds area where machining is difficult to be performed because of heat generated is extremely high. therefore, high-speed machining is also known as cutting speeds beyond that limit. generation of similar tool temperature at two different cutting speed can be done at both conventional and high speed machining. this condition is thoroughly shown in figure 1. two different cutting speed is indicated by va (conventional speed) and vb (high speed) which produce the same life of cutting tool. the tool temperature decreases when the cutting speed moves further area of b resulting in “unlimited” life of cutting tool [7, 8]. by applying up milling technique, temperature recorded increases gradually during the cutting period and the highest cutting temperature is achieved right after machining process end during milling of ti–6al–4v. oppositely, by applying down milling technique, the cutting temperature increases rapidly just after cutting process begun and decrease during the cutting. it is clear that significant temperature rise occurred when down milling is applied compared to up milling technique [8]. a number of researches [2-6, 8] have been carried out around cutting temperatures and much important understanding has been gained. however, the cutting temperature of aisi h13 in high speed end milling by considering cutting temperature at the corner of pocket has not been explored. cutting temperature at the corner of pocket plays significant role to ensure that geometrical accuracy and surface quality is satisfied. 2 experimental details the workpiece material used in this research was h13 steel that is hardened and tempered to 48 hrc. the dimensions of the workpiece were 130x100x30 mm. cutting tool 20 mm in diameter was utilized in pocketing process. the cutting tool accommodate two indexable inserts in every single cutting process. each surface was milled using a fresh cutting edge. the coromill 490 insert tools were securely installed to the tool holder. the milling processes were carried out on cnc vertical machining center mazak nexus 410a-ii cnc mill without any cutting fluid. these experiments adapted contour-in direction tool path strategies. contour in tool path strategy described as the path movement of tool during milling along the boundary, creating a window frame-like milling path towards the centre. figure 2 shows contour-in tool path strategy. milling processes were conducted at cutting speeds 150, 200 and 250 m/min. with feed rate were 0.05, 0.1 and 0.15 mm/tooth. depths of cut involved were 0.1, 0.3 and 0.5 mm for every milling process. all the process and parameters were programmed in cnc programming. there are two devices attached to machine while experiment conducted that are dynamometer and thermal camera. the dynamometer is supported by its devices such as charge amplifier, signal conditioning and signal analyser to measure cutting force. thermal camera on the other hand equipped by image analyser to measure cutting temperature. figure 3 and figure 4 show experimental setup and experimental procedure. figure 1: high speed machining diagram [7, 8]. riza and erry (2016): international journal of engineering materials and manufacture, 1(1), 27-34 29 figure 2: contour-in tool path strategy. figure 3: schematic diagram of experimental setup. tp1 tp2 tp3 tp5/tp tp6 tp7 tp8 tp10 start /tp4 tp11/end investigation of cutting temperature for aisi h13 in high speed end milling 30 figure 4: schematic of experimental procedure. machining process at high speed end milling journal, textbook, internet, etc design of experiments (rsm) geometry & tool material data ɣŕ nc programming workpiece data machine data cutting force (n) machining data fn, vc, n, fz, oc data analysis + data verification data processing conclusions cutting temperature investigation of aisi h13 in high speed end milling milling process high speed end milling parameters (fn, vc, n) cutting path strategies (contour in) end start documentation /publications cutting temp. (oc) infra red analyser dynamometer thermal camera charge amplifier signal conditioner signal analyser e x p e r im e n ta l s e tu p riza and erry (2016): international journal of engineering materials and manufacture, 1(1), 27-34 31 3 results and discussions 3.1 cutting temperature of aisi h13 the cutting temperature of this experiment was measured by thermopro (model tp8) infrared (ir) thermal imaging camera. infra red photograph taken can be seen in figure 5. the effect of an increase cutting speed on cutting temperature is illustrated in figure 6. it can be seen that cutting temperature tend to increases signifacntly until cutting speed reached 200 m/min. the range of cutting temperature for cutting speed 200 m/min and below is between 317.4oc to 920.9oc. once cutting speed reachs into 250 m/min the cutting temperature decline drastically. the cutting temperature in this area is between 104.6oc to 132.2oc. cutting temperature average at speed of below 200 m/min is 649.4oc and drop significantly to 117.4oc when speed of 250 m/min is applied. the ratio of cutting temparature under 200 m/min is 82% higher than speed of 250 m/min. it can be observed that beyonf the area of cutting speeds tested, the surface temperature increased with cutting speed and obviously there is reduction at higher speeds occurred. this approach is similar to what has been discovered by salomon [7] and contrary with mcgee’s findings [9]. mcgee has found that temperature rised paralleled cutting speed untill a maximum which was the same with the workpiece melting point. refer to what has been concluded by dewes (1999) about salomon’s curve that the there is the highest point at middle of cutting speed curve when cutting speed beyond this point, the cutting temperature decreases at higher cutting speed. figure 6 revealed that at speed of 200 m/min the cutting temperature reaches its highest point. it can be considered that cutting temperature at speed up to 200 m/min as the peak cuttting temperature and at speed of 250 m/min is the turn down point of cutting temperature where the lowest cutting temperature is 104.6oc. it is agreeable with salomon’s hypotesis. declination of cutting temperature may be caused by the force produced from the cutting process. as figured out in figure 6 that the cutting force is higher at cutting speed of below 200 m/min. compared to cutting speed of 250 m/min. at cutting speed of below 200 m/min the cutting force is 153n in average while at cutting speed of 250 m/min the force produced was 132n. the cutting temperature begins decline at speed 200 m/min. with 650oc in average. it can be concluded that the melting point of aisi h13 is up to 650oc in average and may be workpiece materials begin to lose their strength and can be cut without difficulty. this is results in cutting energy produced is decreased with the increase of cutting speed. figure 5: infrared photograph of cutting process (vc=200 m/min, vf=0.1 mm/tooth, doc=0.2 mm). figure 6: cutting temperature and cutting force variation in machining of aisi h13. 0 50 100 150 200 250 0 100 200 300 400 500 600 700 800 900 1000 cu tt in g f or ce (n ) cu tt in g t em pe ra tu re (o c) machining parameters temp force investigation of cutting temperature for aisi h13 in high speed end milling 32 3.2 effect of machining parameters on cutting temperature 3.2.1 effect of cutting speed on cutting temperature the results obtained give a understandable idea about values of temperature achieved at high speed end milling process. cutting forces were measured to evaluate and to justify the cutting temperature produced in machining processes. figure 7 shows effect of cutting speed in relation to cutting temperature and cutting force in contour-in path strategy. this figure evidence that at the lower cutting speed, cutting temperature produced is high. when cutting speed reached 150 m/min the cutting temperature is 587oc and turn down drastically to 120oc at speed 250 m/min. this is due to heat produced during milling process at low cutting speed engaged with workpiece longer than at high cutting speed. the chips produced at high speed is released faster than low speed. 3.2.2 effect of feed rate on cutting temperature figure 8 illustrates the effect of feed rate in relation to cutting temperature and cutting force in contour-in path strategy. this figure revealed that feed rate produce lower cutting force and cutting temperature at lower condition. this is because at the lower feed rate, contact time between cutting tool and workpiece is longer than high feed rate. it gives enough time for cutting tool and workpiece to produce heat. at feed rate setup to 0.05 mm/tooth cutting temperature and cutting force are 328oc and 136 n respectively. at feed rate of 0.15 mm/tooth the cutting temperature increased 75% (1427oc) as effect of incremental of force produce by this feed rate that is 408 n. 3.2.3 effect of depth of cut on cutting temperature figure 9 demonstrates the effect of depth of cut in relation to cutting temperature and cutting force in contour-in path strategy. the figure below illustrated that in high speed end milling where contour in path strategy applied, the highest cutting temperature and cutting force is at depth of cut of 0.15 mm. this is because the deeper depth of cut is, the larger contact area between cutting tool and workpiece (depth of cut). figure 7: effect of cutting speed in relation to cutting temperature and cutting force in contour-in path strategy. figure 8: effect of feed rate in relation to cutting temperature and cutting force in contour-in path strategy. 0 20 40 60 80 100 120 140 160 0 100 200 300 400 500 600 700 800 vc = 150 vc = 200 vc = 250 cu tt in g fo rc e (n ) cu tt in g te m pe ra tu re (o c) cutting speed (m/min.) temp. force 0 50 100 150 200 250 300 350 400 450 0 200 400 600 800 1000 1200 1400 1600 fc =0.05 fc = 0.1 fc = 0.15 cu tt in g fo rc e (n ) cu tt in g te m pe ra tu re (o c) feed rate (mm/tooth) temp. force riza and erry (2016): international journal of engineering materials and manufacture, 1(1), 27-34 33 figure 9: effect of depth of cut in relation to cutting temperature and cutting force in contour-in path strategy. 3.3 cutting temperature at the corners of the pocket the behaviour of cutting temperature at the corner of pocket and at the turning point of tool path is shown in figure 10 apparently. cutting temperature when cutter engaged with pocket or turning point is relative low. a few moments since the cutter engage the pocket or turning point, the temperature at that corner becomes higher. as seen in figure 10, a moment when cutter comes to turning point 1 (tp1) the temperature is 449.8oc and right after 1 second tremendously rise up to 1163.7oc. it is more than 200% temperature incremental by only hang about in tp1 by 1 second. the same behaviour occurred at tp2. temperature at tp2 that is when cutter reached this point for the first time is 758.1oc and increases sharply to 1287oc in the next second of time. this is because the table speed needs to be slowed down to give chance the table changing the cutting in accordance with the tool path. as consequence of this action, motor of cnc milling machine experiences a temporary stop before cutting tool turn the feed direction. since the spindle speed unchanged thus it can generates friction and heat, excessively. if the heat produced is very far above the tolerance demands, the workpiece machined may be getting burning marks or even start to burn as a result of this heat. 4 conclusions in this research, the development of latest study about cutting temperature and cutting force were studied. effect of machining parameters in relation to cutting temperature and cutting force in the pocket’s corner in contour-in path strategy were highlighted. the important finding can be concluded as follows: 1. cutting temperature increases as cutting speed is increased. however, at the higher level of cutting speed (250 m/min.) the cutting temperature of aisi h13 turn down. it is agreeable with salomon’s hypothesis. 2. feed rate (fc) play a significant causes augmentation of cutting temperature and cutting force in high speed end milling when countur-in tool path applied. 3. cutting temperature when cutter engaged with pocket or turning point is relative low. a few moments since the cutter engage the pocket or turning point, the temperature at that corner becomes higher than previous. this is because the table speed needs to be slowed down to give chance the table changing the direction in accordance with the tool path. as consequence of this action, motor of cnc milling machine experiences a temporary stop before cutting tool turn the feed direction. 4. in general, fluctuate of cutting force cause rise and fall of cutting temperature in machining processes during the experiment. the cutting force is related to the cutting temperature. acknowledgement with deep grief and condolence, the authors would like to acknowledge the contribution of phd candidate mohamad yuhan suprianto who passed away in mecca during his pilgrimage. without his contribution this research would not be successful. we pray to almighty allah to place him in the haven with his myriads of bounties. 0 20 40 60 80 100 120 140 160 180 0 100 200 300 400 500 600 700 800 doc = 0.1 doc = 0.15 doc = 0.2 cu tt in g fo rc e (n ) cu tt in g te m pe ra tu re (o c) depth of cut (mm) temp. force investigation of cutting temperature for aisi h13 in high speed end milling 34 figure 10: temperature history of aisi h13 at the corner (vc=250 m/min, vf=0.15 mm/tooth, doc=0.20 mm). references 1. sato, m., tamura, n., & tanaka, h. (2011). temperature variation in the cutting tool in end milling. journal of manufacturing science and engineering, 133(2), 021005. 2. coz, g. l. & dudzinski, d. (2014). temperature variation in the workpiece and in the cutting tool when dry milling inconel 718. international journal of advanced manufacturing technology, 74(5), 1133–1139. 3. fata, a. g. j. (2011). temperature measurement during machining depending on cutting conditions. p&a science and technology, 1(2), 16-21. 4. sivasakthivel, p. s., & sudhakaran, r. (2013). optimization of machining parameters on temperature rise in end milling of al 6063 using response surface methodology and genetic algorithm. international journal of advanced manufacturing technology, 67(9), 2313–2323. 5. suhail, a. h., ismail, n., wong, s. v. & jalil, n. a. a. (2011). workpiece surface temperature for in-process surface roughness prediction using response surface methodology. journal of applied sciences, 11(2), 308-315. 6. adesta, e. y. t., riza, m., & ali, m. y. (2012). cutting force impact to tool life of ct5015 in high speed machining by applying negative rake angles. applied mechanics and materials, 117-119, 633-638. 7. salomon, c. j. (1931). process for machining metals of similar acting materials when being worked by cutting tools. german patent: 523594. 8. longbottom, j. m., & lanham, j. d. (2006). a review of research related to salomon’s hypothesis on cutting speeds and temperatures. international journal of machine tools & manufacture, 46(14), 1740–1747. 9. mcgee, f. j. (1979). high speed machining study: methods for aluminium workpieces. american machinist, 121126. -100 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 te m pe ra tu re (o c) time (seconds) surface temperature countour path; vc=200 m/min. ; vf = 0.1 mm/tooth; doc = 0.15 mm t_min t_max t_avg tp1 tp2 tp3 tp4 tp5 tp6 tp7 tp8 tp9 tp10 tp11 international journal of engineering materials and manufacture (2021) 6(4) 312-318 https://doi.org/10.26776/ijemm.06.04.2021.07 ali, m. y. , rahim, a. s. and ya’akub, s. r. mechanical engineering programme area faculty of engineering, universiti teknologi brunei tungku highway, gadong be1410 brunei darussalam e-mail: yeakub.ali@utb.edu.bn reference: ali et al. (2021). solar energy system for brunei residence. international journal of engineering materials and manufacture, 6(4), 312-318. solar energy system for brunei residence mohammad yeakub ali, ahmad syahmi rahim and seri rahayu ya’akub received: 17 march 2021 accepted: 24 july 2021 published: 01 october 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract brunei darussalam is a country that receives high amounts of solar irradiation annually as it is located near the equator. with the abundance of oil & natural gas resources, the country has one of the cheapest electricity costs in the world. this would in turn make solar power underutilized. the purpose of this project is to design a solar system for brunei’s medium sized residence to meet the daily energy demands. a comprehensive analysis was conducted on the solar photovoltaic system for determining the optimum sized parts and components. the design process was divided into detailed sections so that the values are calculated using pvsyst simulation software. the simulation also predicted the specific energy production, performance evaluation, and the losses. cost analysis was also conducted to find the efficiency and the feasibility of the system. the designed solar energy system has a capacity of 60 kwp, producing 75 mwh of usable energy annually. this system uses 66% of the energy available from the sun to generate electricity which covers the electrical demand of brunei’s residences. keywords: solar energy, home electrification, off-grid solar electrification, pvsyst, brunei darussalam 1 introduction brunei darussalam (abode of peace), a small wealthy nation with about 430000 population, is located on the north coast of the borneo island in southeast asia surrounded by the south china sea and malaysian state of sarawak. it has developed wealth from extensive petroleum and natural gas fields and is classified as a developed country. the economy of brunei is small and wealthy, and is a mixture of foreign and domestic entrepreneurship, government regulation and welfare measures, and of village traditions. the government provides free education, excellent health care and pensions. the country relies on its fossil fuel produce to generate almost all the electrical energy to meet the energy demands. there is only one solar power plant in brunei named tenaga suria brunei that has a nominal capacity of around 1.2 kwp which generates an average total of approximately 1.3 gwh of electricity per year (ismail, 2015). although brunei has its own solar farm, it however, only generates at most 2 gwh annually which is only 0.05% of the country's annual electricity generation (international energy agency, 2016). brunei still aims to increase the use of renewable energy as source for power generation to 10% by 2035 (energy department brunei darussalam, 2014). brunei government subsidizes lot of consumables including energy. as a result, electricity cost in brunei is one of the lowest in world where the tariff system in the country starts with b$0.01 (usd 0.0075) per kwh for the first 600 kwh. price per kwh increases for every increase in the tier (table 1). located in the tropical region about 4 degrees north of the equator, the country experiences high amount of solar radiation all year round. with the amount of solar radiation, brunei can take the upper hand to meet the electrical demand of its residences from solar sources alone. taking advantage of this available abundance of solar resource can lessen the reliance on oil and gas and thus providing the country with clean energy. the solar irradiance will not be that same across the surface of the earth as it varies differently between different region and with the diurnal cycle. the surface incident of electromagnetic energy per unit time on a unit area is called "solar irradiance" or often been referred to as "flux" (stickler, 2016). the total solar irradiance that hits the earth's horizontal surface is the global horizontal irradiance (ghi) (vashishtha, 2012). areas that are most favourable are in the subtropical regions where the value of the ghi can go up to 2618 kwh/m 2 , while part of northern europe can be up to 824 kwh/m 2 at most with much lower value during the winter. solar energy system for brunei residence 313 in many southeast asian regions, the sun radiates often, and it radiates intensively. however, this source is still used to different extent across different region. while china and india are already underway with much larger projects, the southeast asian potential is still largely untouched (jacob, billen, & bianchi, 2019). by 2025, the electricity demand is predicted to increase by 50% in the region. thus, the organisation of asean has decided to an objective where the region will use renewable sources for 23% of its primary energy to meet the demands. 1.1 problem statement combining those two factors together, brunei's oil and gas produce is the primary source of generating energy while only 0.05% coming from solar pv. this shows that solar energy is not a popular way to generate their electricity to power up residences. with the high amount of solar irradiance brunei receives, solar power is being underutilize. since solar energy is not that popular in brunei, there are limited studies that focuses on designing an off-grid solar energy system for brunei's residences. this project might not have any immediate impact as the country still enjoy one of the lowest rates of electricity. unfortunately, this luxury might disappear in the future. when the time comes, the country would want search for the best alternative to obtain cheap electricity, then this project will have its significance. 1.2 objectives the aim of this project is to design an off-grid solar system for brunei residences with moderate electricity demand. there are specific objectives that should be attained in order to achieve the objective of this project:  to estimate daily electrical load for residences within lambak area.  to introduce a basic off-grid solar system layout and configuration.  to select system components and carry out cost analysis.  to simulate the model system using pvsyst software.  to evaluate the performance for the designed system. this project focuses on the design and simulation of a solar photovoltaic system fit to meet the electrical demand of brunei residences specifically in a selected location named lambak. chapters are divided as follows. a brief literature review in chapter 2 analyses the different types of energy sources, both renewable and nonrenewable, that is available worldwide. this chapter does put an emphasis more towards solar energy as its technologies and components are also reviewed. methods of research to design the system is outlined and explained in chapter 3. this chapter shows the different steps to obtain variables that will help in the making of the system configurations. results from both simulation and calculations are portrayed and discussed in chapter 4 where the basic design of the solar system layout and configurations are introduced. in this chapter, pvsyst software is used to simulate the effectiveness of the proposed design. conclusions from the project will be summarized in chapter 5 where recommendations and suggestions are given to further improve the project or its related field in the future. 2 solar photovoltaic systems solar photovoltaic system is a system where the process of converting solar radiation to electrical energy occurs. the systems are classified into two namely on-grid, and offgrid solar photovoltaic systems. on-grid photovoltaic systems are designed specifically to operate with the national electrical grid connected to the system. this system is made to supply electricity for the ac electrical loads. when there is excessive amount of energy generated, the excess energy will be returned into the grid (alkhadi & dulaimi, 2018). a system where there is no connection to the national electrical power grid is classified as an off-grid solar photovoltaic system. this system comprises of the photovoltaic module, solar charge controller, batteries, inverters, and loads (figure 1) (alkhadi & dulaimi, 2018). this system uses the solar panels to provide electrical power during the day and use electricity stored in batteries during the night. the batteries will then be recharged during the day to store electrical energy where the light from the sun is available. for a small-scale stand-alone system, it does not have to be attached on the roof top of the houses or buildings as it can be portable. this will provide more reliable and free electrical power anywhere. it also provides back up power supply when there is no solar energy absorbed by the solar panel. ali et al. (2021): international journal of engineering materials and manufacture, 6(4), 312-318 314 figure 1: schematic diagram of an off-grid system (alkhadi & dulaimi, 2018) 3 solar system designs numerous studies have been published with regards to the different designs of solar systems in different countries. these studies were mostly done in countries that are in the subtropical climate such as bangladesh, egypt, iraq, jordan, and nigeria, where the potential of solar energy is the greatest. when comparing these studies' research methods, they are somewhat similar where the estimation of load being the first parameter to be found. another parameter comes after load estimation is determining the tilt angle with respect to their geographical location. then comes the selection of their area's system voltage, followed by the selection of the photovoltaic system components which begins with the photovoltaic module. these pre-determined components help to design the system with controlled variables. studies on the designing of the solar energy system resulted in different configurations even if some studies were carried out in the same country. the reason being is that the criterial components are different. not only that but some countries are big thus determining the tilt angle might have been slightly different. some studies include the material and dimensions of the wire used in the system to ensure minimal power loss. some studies also include the calculation of payback period of the system to show the worth of implementing solar photovoltaic system for residences. 3.1 daily load estimation and sun hours in order to know the electrical demand of brunei’s residences, load estimation survey is to be conducted. this survey includes the estimated daily energy demand in watt-hour of all the appliances used in a residence. the average total energy consumption will be used to figure out the sizing and rating of each component. the amount of sunlight that photovoltaic modules receive is also important to consider when designing a solar energy system. electrical energy a photovoltaic module can be more accurately represented during peak sun hours. peak sun hours are the hour when sunlight is at its most intense where the usual average may lie closer to 3 or 4 hours. the average total of peak sun hours will also be used to figure out the sizing and rating of each component. system sizing is basically the process of calculating and evaluating the suitable voltage and current for each of the photovoltaic system components. the evaluation has to be done in order to meet the demand of the daily consumption of electricity in a residence. this chapter focuses on the design of the solar energy system for the residences of brunei darussalam. also, included in this chapter is the results obtained from the load estimation surveys, the findings of necessary parameters, the calculation results of the designing processes and the simulation results of design performance. there are 40 survey-interviews that were successfully conducted on different households of kampong lambak and its surrounding areas where each household provided different load profile estimates. the total power used varies from 10.270 kw to 38.801 kw. whereas the energy consumption varies from 58.342 kw/day to 362.590 kwh/day (figure 2). load profile of the appliances for selected households are shown in ‘appendix a’. the sun hours that brunei received annually is a minimum of 4 hours per day. this means that the solar insolation in which this country would receive 4 hours of the sun at its peak giving out the maximum irradiance of around 1 kwm2⁄. although brunei is located near the equator where the solar radiation is high all year round, its sun hours are not as much as those of the subtropics or desert areas (figure 3). solar energy system for brunei residence 315 figure 2: graph of total daily energy consumption for each household surveyed figure 3: amount of sun hours received each day (alte, 2020) 4 pvsyst software simulation the designed photovoltaic system has undergone simulation using the pvsyst software and in this section, results from the simulation of the designed system will be analysed. from the simulation, the energy produced by the system, specific production value, performance ratio and system losses were acquired. the obtained results will be analysed for the performance evaluation of the designed photovoltaic system. full report obtained from the pvsyst software simulation is shown in ‘appendix c’. from the obtained main simulation results, there are three main parameters that has been evaluated. the first parameter being the total amount of energy that was generated by the system on an annual basis. the energy produced by the designed photovoltaic system is 90.87 mwh/year. the second parameter is the specific production of energy by the designed system on an annual basis for each installed kwp which is 1456 kwh/kwp/year. the third main parameter that has been evaluated by the software is the average yearly performance ratio of 66.05%. pvsyst software did not compute the system efficiency. therefore, the evaluation of system efficiency must be done manually. since the annual value of the energy that is directly supplied to the user is known, the average monthly value for the energy that is supplied to the user is 6257.75 kwh. from the full report in ‘appendix c’, under the pv array characteristics, the collector area can be acquired thus enabling the calculation of the efficiency of the designed system. the formula of calculating system efficiency is provided by pvsyst as shown in equation 1 (pvsyst, n.d.) ali et al. (2021): international journal of engineering materials and manufacture, 6(4), 312-318 316 𝑆𝑦𝑠𝑡𝑒𝑚 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 = 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑀𝑜𝑛𝑡ℎ𝑙𝑦 𝐸𝑈𝑠𝑒𝑟 𝐶𝑜𝑙𝑙𝑒𝑐𝑡𝑜𝑟 𝐴𝑟𝑒𝑎 (1) various losses in the designed photovoltaic system are represented in the arrow lost diagram that was obtained from pvsyst software simulation (figure 4). the diagram helps to analyse the various losses that are to be faced when installing the system. from the diagram, horizontal global irradiation is 1816 kwh/m2. however, the effective irradiation on the collector is 1766 kwh/m2. just from irradiance level itself, a loss of 3.1% of initial energy already occurs. when the effective irradiation falls on the surface of the photovoltaic module, electrical energy is produced, thus undergoing the photovoltaic conversion phase. after undergoing the photovoltaic conversion phase, the array nominal energy at standard testing condition is 110.3 mwh. at standard testing conditions, the efficiency of the photovoltaic array is 17.86%. the effective energy at the output of the array is 92.5 mwh. there are various losses in between where 0.6% are losses due to irradiance level, 11.2% are losses due to the temperature, 2.5% losses through unused energy due to full battery, and mismatch losses and ohmic wiring losses at 1.1% and 2.3% respectively. a total of 17% of losses occurs in this stage. from the photovoltaic array, the energy will pass through the charge controller and inverter. at this stage, the energy reduces to 88.5 mwh. a total of 4.4% losses occurred within the charge controllers and inverters. there are further losses when it reaches the energy supplied to the user stage, which by now the energy reduces to 75.1 mwh. during energy storage, a further 17.9% losses occurred in the process of battery storage. figure 4: arrow loss diagram for the designed photovoltaic system solar energy system for brunei residence 317 5 cost analysis since the photovoltaic system has been designed, cost analysis can be carried out. cost analysis can give strong evidence on the performance of the designed system whether it is efficient or not. furthermore, this analysis can determine the feasibility of the system if it were to be installed. the cost breakdown of the selected component of the system and its designed quantity has been tabulated in table 1 with that high total cost of the system, it is very possible that bank loan is needed to install the designed system. table 1: cost breakdown of system components items manufacturer rating qty cost (usd) photovoltaic modules talesun 300 w 208 15600 solar charge controller bluesun 48 v 140a max 10 1280 deep-cycle batteries deka 253 ah 308 64680 inverters jinan deming 40 kw 1 3049 mounting, cabling and connector generic 500 estimated shipping cost by sea 4000 total cost of the system 85109 total cost system after 10 years of 4.5 % p.a. financing 123408.05 6 conclusions & recommendations the aim of this project was to design an off-grid solar system for brunei residences to meet the moderate electricity demand. the objective was achieved by estimating the daily electrical needs of residences around lambak area. pvsyst simulation software is used in this project to verify the efficiency and feasibility of the design. this research showed: 1. a multi-staged criterion was conducted when designing this solar photovoltaic system. this gives the best optimization to the selection of ratings for each of the main component as well as its arrangement. the designed solar energy system did meet its energy demand both during the day and night. furthermore, the system can provide energy to meet the load demand on a maximum of 3 days without solar input. 2. the results from the software simulation did verify the efficiency and the feasibility of the system design as it converts 66.1% of the sun’s energy into electricity. furthermore, the specific energy cost of the system is usd 0.08 per kwh and has a payback period of 21.7 years further proves efficiency and the feasibility of the designed system. the low cost per kwh shows that the solar photovoltaic sources are indeed a good alternative for electricity generation in this country. 3. finally, this project provides a base and structure for the evaluation of the design solution. the evaluation is not only restricted to lambak and its surrounding areas, but also in other parts of the country since the sun irradiation is high all year round. this project may not be as important as it is now, but when the country is considering renewable energy sources for cheap energy, then this project will have its significance. conclusions & recommendations 4. the survey that was carried out to determine the total power usage and daily load consumption is not accurate, thus resulting of an overestimated value for system sizing. this, in turn, would make the current evaluated cost to be higher than it should. therefore, making the payback period longer and the specific cost per kwh higher. 5. this project can be further improved by conducting a more in-depth survey to accurately measure the energy usage of a household to obtain the weekly power usage so that more accurate evaluation can be done. further improvements can be made by including the wires used to connect each component for system sizing and performance simulation so that it gives more accurate results that can be applied in real life. 6. the survey that was carried out to determine the total power usage and daily load consumption is not accurate, thus resulting of an overestimated value for system sizing. this, in turn, would make the current ali et al. (2021): international journal of engineering materials and manufacture, 6(4), 312-318 318 evaluated cost to be higher than it should. therefore, making the payback period longer and the specific cost per kwh higher. 7. this project can be further improved by conducting a more in-depth survey to accurately measure the energy usage of a household to obtain the weekly power usage so that more accurate evaluation can be done. further improvements can be made by including the wires used to connect each component for system sizing and performance simulation so that it gives more accurate results that can be applied in real life. reference 1. h. ismail, “tenaga suria brunei – brunei’s very own solar farm!” solar brunei, 2015. [online]. available: https://www.solarbrunei.com/blogs/news/76917508-tenaga-suria-brunei-bruneis-very-own-solar-farm. [accessed 2019]. 2. “electricity information 2016,” international energy agency, 2016. [online]. available: https://www.iea.org/statistics/?country=brunei&year=2016&category=electricity&indicator=solargen&mo de=table&datatable=electricityandheat. [accessed 2019]. 3. energy department brunei darussalam, energy white paper, bandar seri begawan, brunei darussalam: energy department, prime minister’s office brunei darussalam, 2014. 4. g. stickler, “educational brief – solar radiation and the earth system,” national aeronautics and space administration, 2016. [online]. available: https://web.archive.org/web/20161229182712/http://education.gsfc.nasa.gov/experimental/july61999siteupda te/inv99project.site/pages/science-briefs/ed-stickler/ed-irradiance.html. [accessed 2019]. 5. s. vashishtha, “differentiate between the dni, dhi and ghi,” first green consulting, 2012. [online] available: https://firstgreenconsulting.wordpress.com/2012/04/26/differentiate-between-the-dni-dhi-and-ghi/. [accessed 2019]. 6. j. jacob, d. billen, and g. bianchi, solar power: shining prospects in southeast asia and india, munich, germany: roland berger gmbh, 2019. a. alkhalidi, and n. dulaimi, “design of an off-grid solar pv system for a 7. rural shelter,” 2018. doi:10.13140/rg.2.2.24352.07689 8. “solar insolation map world,” alte, 2020. [online]. available: [accessed 2020]. 9. “simulation variables: standalone system,” pvsyst.. available: https://www.pvsyst.com/help/simulation_variables_standalone.htm. [accessed: 10 july 2020]. international journal of engineering materials and manufacture (2018) 3(1) 9-17 https://doi.org/10.26776/ijemm.03.01.2018.02 j. s. m. ali, h. meftah and m. masturah department of mechanical engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: jaffar@iium.edu.my reference: ali, j. s. m., meftah, h. and masturah, m. (2018). stress analysis of thin-walled laminated composite beams. international journal of engineering materials and manufacture, 3(1), 9-17 stress analysis of thin-walled laminated composite beams under shear and torsion j. s. mohamed ali , meftah hrairi and masturah mohamad received: 09 december 2017 accepted: 29 december 2017 published: 30 march 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract an educational software which can aid students in the stress analysis of thin wall open sections made of composite material has been developed. the software enables students to easily calculate stresses in different shapes of thin walled open section and evaluate the stresses in each ply under shear and torsion. results obtained through this software have been validated against ansys. the software is intended to be an educational tool for effective teaching and learning process on thin-walled structures, aircraft structures and composite structures courses. keywords: educational software; stress analysis; thin wall open section; composite structures 1 introduction composite materials are well known to have excellent fatigue resistance, high specific strength and stiffness, good corrosion resistance, excellent fire resistance and lower thermal expansion. in early years of development of composite materials in aerospace application, they were only used for secondary and tertiary structure of the aircraft. however, recently, the airframe and primary structures are also made entirely of composite. moreover in aerospace industry, most of the aircraft structures are thin-walled in nature and open section beams are used in aircrafts to stiffen the thin skins of the cellular components and provide support for internal loads from floors, engine mountings, etc. thus the focus of this study is on the stress analysis of composite thin-walled open sections. literature on stress analysis of thin walled sections under different type of loadings are numerous. parambil (2010) presented a closed form solution for ply by ply stress analysis of thin-walled beam with un-symmetrical cross-section ibeam and validated with respect to ansys. nurhuda and ali (2017) developed an educational software for thinwalled sections of isotropic and composite materials. the software evaluates only the average normal stresses due to bending and average shear stresses due to shear and torsion for i, c, t, and z cross-section beams. thus layerwise stress analysis was not carried out in this study. vishal (2012) extended the research done by parambil (2010) in stress analysis of laminated composite beam under torsional loads for i-beam. he has done the analysis to calculate shear center, equivalent torsional stiffness, equivalent warping stiffness and equivalent bending stiffness and compared with ansys. kollar and pluszik (2012) introduced a new theory called torsional-warping shear deformation theory in order to determine the stiffness of anisotropic beams. the theory also includes the restrained torsional warping from vlasov’s theory and the in-plane shear deformations from timoshenko theory. hubert (2013) studied on thin-walled composite column under axial compression. lachenal et al. (2013) introduced a new feature to i-composite beam by re-designing and adding a morphing twist functionality to the beam. the flanges layup were designed to obtain a highly non-linear torsional stiffness whilst the web are designed for lower stiffness in order to allow large twist deformation. carpinteri et al. (2014) studied the effect of warping of u-shaped beam under torsion and shear force. li and easterbrook (2014) developed a simple way to derive the torsional equations for thin-walled open or closed or combined open and closed sections beam under free torsion using a simple statically indeterminate concept. sachidananda (2016) in his work presented stress analysis of unsymmetrical layup of composite i-beam. ply stresses due to axial loads were presented and compared to fea analysis. stress analysis of thin-walled laminated composite beams under shear and torsion 10 through the literature survey, it can be concluded that many scholars have derived the closed form solutions for thin-walled laminated structures, where most of them chose the laminated plate, ibeam and box beam as subject of their researches. very few have carried out the ply stress analysis and have tabulated results which are useful for validation. furthermore, it was found that software based on closed form solution is not available for ply stress analysis of thin walled sections, which motivated to develop such an educational software. the present work is the continuation of work done by ali et al [2015] which focused on i, c and topen section of thin-walled laminated composite beams under axial loads and bending moments only. in this work it has been extended for the shear and torsional loading. the software has been developed in matlab which is able to calculate ply stresses (σx, σy, τxy), and the results were validated against fea software (ansys). in this paper, only i, c and t beams which are subjected to torsional loads and shear force is presented. the software is valid for beams which are long, un-tapered and slender with ratio of the cross-sectional dimension to the length is at least 1/10. meanwhile, the ratio of the laminate thickness to the cross-sectional dimension is at least 1/10. present software utilizes a beam theory developed by kollar and pluszik (2002) which neglects the effect of shear deformation and restrained warping. 2 methodology a cantilever beam made up of thin-walled laminated open section made of composite material subjected to shear force and torsional moment is considered for analysis. the following laminate theory with general laminate constitutive equations and the theory of laminated beam analysis are from kollar and pluzsik (2002) and datoo (1991). the lay-up of each wall segment is symmetrical, however every wall segment can have different lay-up configuration. 2.1 determination of elastic constants of laminate the procedure for computing the stiffness, compliance and equivalent elastic constants, which is similar for any laminate configuration, is as follows: firstly, determine the reduced stiffness terms qij and determine the transformed reduced stiffness terms �̅�𝑖𝑗 using the qij terms. the stress-strain relationship in the reduced stiffness terms is shown in eq. (1). meanwhile, the total of direct and shear strain is shown in eq. (2). [ 𝜎𝑥 𝜎𝑦 𝜏𝑥𝑦 ] = [ �̅�11 �̅�12 �̅�13 �̅�12 �̅�22 �̅�23 �̅�13 �̅�23 �̅�33 ] [ 𝜀𝑥 𝜀𝑦 𝛾𝑥𝑦 ] (1) [ ϵ𝑥 ϵ𝑦 γ𝑥𝑦 ] = [ ϵ𝑥 0 ϵ𝑦 0 γ𝑥𝑦 0 ] + 𝑧𝑘 [ 𝑘𝑥 𝑘𝑦 𝑘𝑥𝑦 ] (2) determine the laminate stiffness terms aij, bij and dij. force and moment intensities can be determined as shown in eq. (3). [ 𝑁𝑥 𝑁𝑦 𝑁𝑥𝑦 𝑀𝑥 𝑀𝑦 𝑀𝑥𝑦] = [ 𝐴11 𝐴12 𝐴13 𝐵11 𝐵12 𝐵13 𝐴12 𝐴22 𝐴23 𝐵12 𝐵22 𝐵23 𝐴13 𝐴23 𝐴33 𝐵13 𝐵23 𝐵33 ⋮ 𝐵11 𝐵12 𝐵13 𝐷11 𝐷12 𝐷13 𝐵12 𝐵22 𝐵23 𝐷12 𝐷22 𝐷23 𝐵13 𝐵23 𝐵33 𝐷13 𝐷23 𝐷33] [ ϵ𝑥 0 ϵ𝑦 0 γ𝑥𝑦 0 𝑘𝑥 𝑘𝑦 𝑘𝑥𝑦] (3) the laminate stiffness terms aij, bij and dij are inverted to obtain the corresponding compliance terms aij, bij and dij. [ ϵ𝑥 0 ϵ𝑦 0 γ𝑥𝑦 0 𝑘𝑥 𝑘𝑦 𝑘𝑥𝑦] = [ 𝑎11 𝑎12 𝑎13 𝑏11 𝑏12 𝑏13 𝑎12 𝑎22 𝑎23 𝑏12 𝑏22 𝑏23 𝑎13 𝑎23 𝑎33 𝑏13 𝑏23 𝑏33 ⋮ 𝑏11 𝑏12 𝑏13 𝑑11 𝑑12 𝑑13 𝑏12 𝑏22 𝑏23 𝑑12 𝑑22 𝑑23 𝑏13 𝑏23 𝑏33 𝑑13 𝑑23 𝑑33] [ 𝑁𝑥 𝑁𝑦 𝑁𝑥𝑦 𝑀𝑥 𝑀𝑦 𝑀𝑥𝑦] (4) 2.2 analysis of thin-walled composite open sections a thin-walled composite open section is made from an assembly of flat layered laminated composite. a section is defined as thin-walled if its thickness is small compared to the cross-sectional dimension; the ratio of the thickness to ali, et al. (2018): international journal of engineering materials and manufacture, 3(1), 9-17 11 the cross-sectional dimension is at least one tenth. in this analysis, a cantilevered beam is considered which is fixed at one end subjected to either shear force or torsional load. the length of the beam is in x-direction, the height of the beam’s cross-section is in z-direction and y-direction is the width of the beam’s cross-section. three different crosssections are considered in this analysis which are i, c and tsections as shown in figure 1. all laminates considered are symmetric and details of the layup of the laminates are presented in tables 1 and 2. figure 1: cross-sections c, i and t of beam 2.2.1 torsion according to kollar and springer (2003), for an open-section beam under torsion, the in-plane forces per unit length which are ny, nxy and moment per unit length my are zeros. thus, the expressions for nx, mx and mxy in matrix form is: [ 𝑁𝑥 𝑀𝑥 𝑀𝑥𝑦 ] = [𝑅ŋ][𝜇𝑘] −1[𝑅𝑘][𝑊] [ 𝑁 𝑚𝑦 𝑚𝑧 𝑇 ] (5) where n, my, mz and t are the applied force, moment and torque at the centroid. under pure torsion, n, my and mz are zero. the expressions of rŋ,μk, rk and w are as follows: [𝑾] = [𝑷]−𝟏 (6) [𝑷] = ∑ ⌈𝑹𝒌⌉ 𝑲 𝒌=𝟏 [𝑹𝒌] 𝑻[𝝎𝒌] −𝟏 (7) [𝑹𝒌] = [ 𝟏 𝒛𝒌 𝒚𝒌 𝟎 𝟎 𝐜𝐨𝐬 𝜶𝒌 −𝐬𝐢𝐧 𝜶𝒌 𝟎 𝟎 𝟎 𝐬𝐢𝐧 𝜶𝒌 𝟎 𝐜𝐨𝐬 𝜶𝒌 𝟎 𝟎 𝟏 ] (8) [𝝎𝒌] = 𝟏 𝒃𝒌 [ 𝒂𝟏𝟏 𝟎 𝟎 𝟎 𝟎 𝟎 𝟎 𝒅𝟏𝟏 𝟎 −𝒅𝟏𝟑 𝟐 𝟎 𝟏𝟐 𝑨𝟏𝟏𝒃 𝟐 𝒌 𝟎 −𝒅𝟏𝟑 𝟐 𝟎 𝒅𝟑𝟑 𝟒 ] (9) [ 𝑨𝟏𝟏 𝑨𝟏𝟐 𝑨𝟏𝟑 𝑨𝟏𝟐 𝑨𝟐𝟐 𝑨𝟐𝟑 𝑨𝟏𝟑 𝑨𝟐𝟑 𝑨𝟑𝟑 ] = [ 𝒂𝟏𝟏 𝟎 𝟎 𝟎 𝒅𝟏𝟏 𝒅𝟏𝟑 𝟎 𝒅𝟏𝟑 𝒅𝟑𝟑 ] −𝟏 (10) [𝑹ŋ] = [ 𝟏 𝟎 ŋ 𝟎 𝟎 𝟏 𝟎 𝟎 𝟎 𝟎 𝟎 −𝟐 ] (11) where ŋ is the position along the wall segment. stress analysis of thin-walled laminated composite beams under shear and torsion 12 [𝝁𝒌] = [ 𝒂𝟏𝟏 𝟎 𝟎 𝟎 𝒅𝟏𝟏 𝒅𝟏𝟑 𝟎 𝒅𝟏𝟑 𝒅𝟑𝟑 ] (12) after obtaining the expressions for nx, mx and mxy, these values can be substituted into equations (4) and (1). we are interested to find the value of maximum shear stress. thus, the equation is reduced to: 𝜏𝑥𝑦 = [ǭ13 ǭ23 ǭ33] [ ϵ𝑥 ϵ𝑦 γ𝑥𝑦 ] (13) 2.2.2 shear force expression for shear flow for open section under application of shear forces vz and vy (kollar and springer 2003): 𝒒𝒐𝒑𝒆𝒏 = − 𝑬𝑰𝒛𝒛𝑽′𝒛−𝑬𝑰𝒚𝒛𝑽′𝒚 𝑬𝑰𝒚𝒚𝑬𝑰𝒛𝒛−(𝑬𝑰𝒚𝒛) 𝟐 ∫ 𝒛 𝒂𝟏𝟏 𝒔𝟏 𝟎 𝒅𝒔 − −𝑬𝑰𝒚𝒛𝑽′𝒛−𝑬𝑰𝒚𝒚𝑽′𝒚 𝑬𝑰𝒚𝒚𝑬𝑰𝒛𝒛−(𝑬𝑰𝒚𝒛) 𝟐 ∫ 𝒚 𝒂𝟏𝟏 𝒔𝟏 𝟎 𝒅𝒔 (14) average shear stress can be obtained by dividing shear flow by the wall thickness. 𝜏𝑥𝑦 = 𝑞𝑜𝑝𝑒𝑛 𝑡 (15) 2.3 ansys simulation the i, c, and t cross-section beams are modelled using ansys by using shell 181 layered element. meshing is done by setting the size of width lines to 0.01, meanwhile the length lines are set to 500 number of division. the spacing ratio is set to a negative value so that the density of the element will be increased at the edges. prior to application of load, the model is bonded to each other using the contact wizard. one edge of the beam is constrained by setting all degree of freedom to zero. a typical ansys output window is shown in figure 2 for the case of torsion of tbeam. 3 results and discussions the programming for the stress analysis components discussed in the previous section was carried out in matlab. three different standard thin-walled cross-sections – c, i, and t-sections are considered in the analysis. user will be asked to enter material properties, cross-sectional of the beam, number of layers and their orientation. the software will compute the laminate stiffness properties based on the user input data as shown in figure 3. for a given input of torsional moment, the output is the maximum shear stress in each ply. for stress analysis for shear force, user is required to enter any value of shear force and the software will generate the average shear stress. the length of the beam is taken to be 10 inches and all the tabulated results (tables 3-9) are presented at the mid of the beam i.e. at x= 5 in. the y and z coordinates referred in the tables are as shown in figure 1, with z=0 is at the mid plane of the laminate of flange for c and i section and it is at the bottom for t section. 3.1 validation of the results the individual components of the software were checked to ensure its validity and accuracy by comparing the results with ansys. the material used in this analysis is t300/977-2 carbon/epoxy laminate. the elastic properties of the plies for all cross-section are: e1 = 21.75(10 6 ) psi, e2 = e3=1.595(10 6 ) psi, g12 = g13 =0.8702(10 6 ) psi, g23 =0.5366(10 6 ) psi, 12= 13= 23= 0.25. all plies are 0.005 inch thick. table 1 and 2 below give the data of the geometrical cross-section (width for flange and height for web) and ply orientation of each sections respectively. similar to parambil (2015), for the top flange, the ply orientation is [45/45/0/90]s. for the lower flange, the ply orientation is [45/-45/02/90]s while for the web is [45/-45]. table 1: width of geometrical cross-section case upper flange (in) lower flange (in) web (in) (height) i-beam 0.5 0.75 0.5 c-beam 0.5 0.5 0.5 t-beam 1 n/a 0.5 ali, et al. (2018): international journal of engineering materials and manufacture, 3(1), 9-17 13 table 2: ply orientation case upper flange lower flange web i-beam (±45/0/90)s (±45/02/90)s (±45)s c-beam (0/±45/90)s (0/±45/90)s (±45)s t-beam (0/±45/90)s n/a (±45)s 3.1.1 beam under torsion i, c and tbeams which are subjected to torsional moment value of 0.5 lb.in is analysed in this section. if a torsional moment is applied about x-axis, the beam will twist with a constant rate of twist. in ansys, one end is fixed and a constant rate of twist is applied at the other end. typical results for shear stresses in each ply for flange and web of t section is given in tables 3-4, whereas the table 5-6 gives results for shear stresses in each ply for flange and web of c section. it can be found from the tables that the results from the present software agree well with the ansys results except for some cases. the error involved is attributed to the modelling error in ansys such as in the case of applying torsion, a statically equivalent load was applied in fea. figure 2: typical ansys output window (shear stress sxy for t-beam on layer 2 under torsion) figure 3: typical input/output window for the matlab software stress analysis of thin-walled laminated composite beams under shear and torsion 14 table 3: shear stress on the upper flange of t-beam due to torsion x y z 5 0 0.5 ply unit : lb/in2 sxy 1 (0) ansys 227.63 present software 216.947 %diff 4.92 2 (45) ansys 783.14 present software 746.443 %diff 4.92 3 (-45) ansys 595.41 present software 567.438 %diff 4.93 4 (90) ansys 0.00 present software 0.00 %diff 0.00 5 (90) ansys -75.875 present software -72.3158 %diff 4.92 6 (-45) ansys -1194 present software -1138.06 %diff 4.92 7 (45) ansys -1172.1 present software -1117.01 %diff 4.93 8 (0) ansys -303.5 present software -289.263 %diff 4.92 table 4: shear stress on the web of t-beam due to torsion x y z 5 0 0.25 ply unit : lb/in2 sxz 1 (45) ansys 241.58 present software 236.016 %diff 2.36 2 (-45) ansys 4.2521 present software 4.24759 %diff 0.11 3 (-45) ansys -712.91 present software -696.679 %diff 2.33 4 (45) ansys -495.91 present software -484.775 %diff 2.30 ali, et al. (2018): international journal of engineering materials and manufacture, 3(1), 9-17 15 table 5: shear stress on the lower flange of c-beam due to torsion x y z 5 0.25 0 ply unit : lb/in2 sxy 1 (0) ansys 232.88 present software 225.893 %diff 3.09 2 (45) ansys 832.35 present software 774.849 %diff 7.42 3 (-45) ansys 614.99 present software 593.354 %diff 3.65 4 (90) ansys 0.00 present software 0.00 %diff 0.00 5 (90) ansys -71.163 present software -75.2977 %diff 5.49 6 (-45) ansys -1168 present software -1182.04 %diff 1.19 7 (45) ansys -1142.4 present software -1166.17 %diff 2.04 8 (0) ansys -299.2 present software -301.191 %diff 0.66 table 6: shear stress on the web of c-beam due to torsion x y z 5 0 0.25 ply unit : lb/in2 sxz 1 (45) ansys 270.25 present software 250.828 %diff 7.74 2 (-45) ansys 0.00 present software 0.00 %diff 0.00 3 (-45) ansys -781.81 present software -730.488 %diff 7.03 4 (45) ansys -535.96 present software -499.682 %diff 7.26 3.1.2 beam under shear force the following section shows the results for isection beam under -100lb shear force at the centre of the web. typical results for average shear stresses for upper and lower flange (y=0) as well as on the web (z=0.25) is given in tables 7-9. it can be found from the table that the results from the software agree well with the ansys with a reasonable modelling error. as the software for the case of shear loading produces the average shear stress as the output, the layerwise results of shear stresses from ansys were averaged to compare with the software thus leading to further error in shear loading case. stress analysis of thin-walled laminated composite beams under shear and torsion 16 table 7: average shear stress on the lower flange of i-beam due to shear force ply unit : lb/in2 sxy 1(45) ansys -5289 2(-45) 12494 3(0) 556.31 4(0) 552.32 5(90) 548.32 6(90) 544.33 7(0) 540.34 8(0) 536.35 9(-45) 11518 10(45) -4501.7 ansys (average) 1749.927 present software 2003.85 %diff 12.67 table 8: average shear stress on the upper flange of i-beam due to shear force ply unit : lb/in2 sxy 1(45) ansys 15865 2(-45) -23317 3(0) -571.37 4(90) -577.71 5(90) -584.05 6(0) -590.39 7(-45) -24220 8(45) 16552 ansys (average) -2180.44 present software -2382.5 %diff 8.48 table 9: average shear stress on the web of i-beam due to shear force ply unit : lb/in2 sxz 1(45) ansys -8364.9 2(-45) -12453 3(-45) -12453 4(45) -8364.9 ansys (average) -10409 present software -9834.84 %diff 5.84 4 conclusions a software that can perform stress analysis of thin-walled open sections made of composite materials has been developed using matlab. the results for shear force and torsion obtained from the software were found to be in good agreement with ansys and these tabulated results presented will be useful for validation. this software combined with the earlier software (ali, et al., 2015) will be able to calculate ply stresses and average stresses due to axial load, bending moment and torsion, average shear stress due to shear force, axial and bending stiffness, torsional stiffness, rate of twist as well as section properties such as centroid and shear centre. thus this software is expected to be useful as an educational tool for both students and lecturers for effective teaching-learning process. ali, et al. (2018): international journal of engineering materials and manufacture, 3(1), 9-17 17 references 1. ali, j.s.m. masturah, m. and meftah hrairi. (2015). stress analysis of thin-walled laminated composite beams. aprn journal of engineering and applied sciences, 10(21), 10088-10095. 2. carpinteri, a. et al. (2014). the effect of the warping deformation on the structural behaviour of thinwalled open section shear walls. thin-walled structures, 84, 335-343. 3. datoo, m. h. (1991). mechanics of fibrous composites. london: elsevier applied science. 4. hubert, d. (2013). numerical analysis of stability of thin-walled composite column with open crosssection. mechanics and mechanical engineering, 17(1), 29-35. 5. kollar, l. p. and springer, g. s. (2003). mechanics of composite structures. cambridge: cambridge university press. 6. kollar, l.p. and pluzsik, a. (2002). analysis of thin-walled composite beams with arbitrary layup. journal of reinforce plastics and composite, 21(16), 1423-1465. 7. kollar, l.p. and pluzsik, a. (2012). bending and torsion of composite beams. journal of reinforce plastics and composite, 31(7), 441-480. 8. lachenal, x., daynes, s., and weaver, p.m. (2013). a non-linear stiffness composite twisting i-beam. journal of intelligent material systems and structures, 25(6), 744-754. 9. li, l.y. and easterbrook, d. (2014). free torsion of thin-walled structural members of open and closed sections. applied mathematics and mechanics, 35(1), 25-32. 10. nurhuda bt ismail and mohamed ali j.s. (2011) educational software for stress analysis of thinwalled section 2: composite material. icmaae’11, may 17-19, iium, kualalumpur. 11. parambil, j. c. (2010). stress analysis of laminated composite beam with i-section. m.sc. thesis. the university of texas at arlington: arlington. 12. sachidananda, g. (2016). stress analysis of laminated composite beams with i-section. special issue on international journal of recent advances in engineering & technology, 4(5), 69-74. 13. vishal, m.s.s. (2012). torsional analysis of a composite i-beam. m.sc. thesis. the university of texas at arlington: arlington. retrieved april20, 2012. https://uta-ir.tdl.org/ international journal of engineering materials and manufacture (2022) 7(3) 71-77 https://doi.org/10.26776/ijemm.07.03.2022.01 dinesh reddy nallagangula, abdul md mazid , neamul khandoker school of engineering and technology central queensland university, rockhampton, australia e-mail: a.mazid@cqu.edu.au reference: dinesh reddy nallagangula, abdul md mazid, neamul khandoker (2022). surface integrity study of ti-alloy using optimal cutting speed. international journal of engineering materias and manufacture, 7(3), 71-77. surface integrity study of ti-alloy using optimal cutting speed dinesh reddy nallagangula, abdul md mazid and neamul khandoker received: 27 may 2022 accepted: 08 july 2022 published: 20 july 2022 publisher: deer hill publications © 2022 the author(s) creative commons: cc by 4.0 abstract ti-alloy represents a significant metal portion of aircraft structural and engine components for high reliability. surface integrity is one of the most relevant parameters used for evaluating the quality of finish machined surfaces. the residual stress and surface alteration with each layer and depth of work hardening by machining ti-alloy are critical due to safety and sustainability concerns. residual stresses, white layers well microstructural alterations can be figured out to improve surface qualities of end products. many parameters such as cutting speed, feed rate, depth of cut affect the machined surface quality particularly surface fisnish. this article provides details of lathe turning for investigation of surface roughness for varying cutting parameters. an attempt has been made to search for best ranges of cutting regimes that could produce best surface roughness for machining ti-6al-4v alloy using uncoated cutting tool. taylor-hobson device is used to measure the surface roughness on the machined workpieces. in this project three series of experimentaions were carried out and a total of 16 steps of operations in each series are performed for determining the surface roughness. real life experimental investigation has allowed to express the results in graphical form (using tabulated data) that has suggested best ranges of cutting regimes (parameters) for obtaining the best ranges of surface roughness for machining ti-6al-4v using uncoated carbide tool. the work has indicated to investigate the science of bulk flow, particularly the plastic deformation, for difficult to machine materials, at a much higher temperature. behaviour of cutting tool materials for high speed cutting is another isuue to develop. keywords: ti-alloy, machining, surface roughness, surface integrity 1 introduction lathe turning is the most widely used metal removal process where material properties, turning parameters, tool wear, dynamic systems interact in a complex way and eventually affect the surface integrity. in this work an attempt has been made to investigate the effect of cutting parameters on surface roughness and eventually surface integrity of α-β titanium alloy ti-6al-4v. titanium alloys are used in various industrial applications specially in aviation and automotive industries because of their high strength-to-weight ratio, excellent corrosion resistance and high strength at higher application temperature. however, titanium alloy (ti-6al-4v) has been recognised, by many researches, as a difficult to cut material due to its low thermal conductivity, high toughness and strength properties, high chemical reactivity with cutting tool material and high hardness. these cause unusual temperature rise in cutting zone (umasekar et al., 2006), faster tool failure, poor surface roughness and higher level of sublayer residual stresses (ezugwu and wang, 1997). as such optimizing cutting parameters for individual alloy using particular cutting tool for better surface roughness and surface integrity remains as a chellenge in academia and industries (mazid et al., 2019). lathe turning parameters has been optimized for different grades of titanium alloy by analyzing various mehods such as surface roughness (akkus and yaka, 2021; umasekar et al., 2017), vibration signal (anil et al., 2016), lubrication method (revenkar et al., 2014), cutting tool temperature (vinayagamoorthy and xavior, 2014) and in addition, sublayer stresses that remains in a body which is stationary at equilibrium condition after removal of external load is residual stress (withers & bhadeshia, 2001). this stress involves numerous sub-surface and superficial characteristics inclusive of plastic deformation, metallurgical changes, crack formation and surface roughness. residual stress is induced on the microstructure layers due to mismatching in the thermal expansion coefficient of the deposited layers (non-uniform), plastic deformation, interstitial impurities and deposition process as shown in the figure 1. the term surface integrity deals with the different mechanical properties such as residual stress and hardness, metallurgical states, and topological parameters (jawahir et al., 2009). the importance of surface integrity in the field of engineering including biomedical applications is very high. according to machado and wallbank (1990) in surface integrity study of ti-alloy using optimal cutting speed 72 the process of the surface integrity, the issues related to the alloy are a surface drag, micro-crack, feed marks, surface tear, deforms and debris. due to plastic deformation, in the machining process, the primary issue related is white layer formation (fig. 1) and plastic deformation. the hardening of the subsurface is seen in the ti alloy which is due to the thermal and mechanical loads. the calculation of the residual stress for the surface integrity can be achieved using different method whereas no quality of work is performed for the ti-alloy. whereas, the finite element based way for the modelling or simulation process is the best approach because of its computational power and advance numerical solutions. for the residual stress assessment in ti-alloy, the most important is the machining process parameters since residual stress is evident in the machining process. the machining has been performed using the lathe turning. for the cutting speed (v) optimization, with different speed and machining fluid-applied, turning operation is completed with measurement of the surface roughness at each step. afterwards, the plot of average surface roughness against individual cutting regimes helps to visualize the best surface roughness zone in graph. likewise, feed rate (f) optimization helps to determine surface quality. the study by guo et al. (2009) illustrated that the stress evident in the solid body that exists remaining when external loading is removed from the body is known as residual stress. this residual stress has a different effect on the machining phenomenon such as deformation, static strength, dynamic strength, chemical resistance and magnetism. the residual stress that is obtained from the hard turning and the grinding is different such as for the fresh tool ware hook-shaped residual stress is evident for the hard turning. in contrast, grinding produces a significant amount of residual surface stress only. similarly, using the worn tools, in the white layer (thermal), there is a considerable amount of tensile stress with more profound and compressive nature is seen for hard turning. oblique cutting (fig. 2) conditions are described throughout by the cutting parameter combination of the depth of cut d, cutting speed v, feed rate f and tool corner/nose radius r. the cutting process is parallel to the direction of motion to remove the unwanted material from a workpiece. the chip flow angle is defined as direction of the chip flow velocity is at an angle normal to the cutting edge of the tool. figure 1: surface integrity and microscopic view (jawahir et al., 2009) figure 2: oblique cutting process (a) process schematic, (b) tool geometry 2 research scope the project concentrates on the research for the economic and sustainable manufacturing processes development for ti-alloys based on the v, f, and d parameters of machining inrespect of surface integrity. the current piece of work targets the followings: mazid et al. (2022). international journal of engineering materials and manufacture, 7(3), 71-77 73 • determining the optimum set of cutting parameters, for uncoated carbide tools, that can provide sufficient enough surface roughnes. thus to increase cutting tool life with less wear. • to provide sustainable procedure for manufacturing industries to make the ti-alloy parts easier and low cost. 3 experiments the machine operation is performed with variation in speed (v), feed (f), and depth of cut (d) using a conventional lathe to produce three sets of samples using uncoated carbide tool. during the process, the tool may damage and needs to replace. using surtronic roughness machine, the roughness of the surface is measured for each sample. 3.1 sample workpiece and cutting tool ti-alloys are recognised as difficult to machine materials which is highly problematic for manufacturing industries. the solution to this problem is made by using hybrid cutting tools. they come with diamond, ceramics and cbn. the tool used to machine the ti-alloy samples is uncoated carbide tools. the tool geometry parameters are lead angle 97°, rack angle 7° and the nose radius 0.8 mm. these values may differ while operating to get the right v, f, d parameters. roughing, facing, turning, finishing and chamfering is done by the triangular tool. the ti-alloy ti-6al-4v (sample workpiece drawing is shown below in fig. 3 (ahsan et al 2016) with length 600 mm and diameter 60 mm. it is a cylindrical shaft. fig. 3 depicts the drawing of the sample-workpiece which explains its dimensions. the workpiece is divided into 16 different parts (samples) with equal size of 5 mm grooving in between. figure 3: sample workpiece specimen (ahsan et al.) 3.2 sample preparation procedures the workpiece specimen (fig. 3) is clamped in 3-jaw chuck of an available conventional chuks. it is series of machining operation with variable machining parameters. in this real life experiment 16 steps of machining operations, 16 steps of turning with various v, f, d cutting parameters. experimental data tables can be obtained, on request, from the contact authour. during the process of turning cutting speed (v) varied within the range of 15 m/min to 120 m/min throughout the process of turning. this is known as step turning and is performed under eight steps taking the depth of cut and cutting speed constant 0.7 mm and 0.2 mm/rev respectively. tool wear can occur during some time when an increase in the feed rate; at that point, tool bit must be replaced. sparkling can occur when a tool gets damaged. by using surface roughness measuring device, surface roughness can be known, and the specimen is taken for the inspection under a microscope to examine the surface integrity of the specimen whether it had any surface deformation such as, plastic deformation, cracks and some factors that influence machining operations. the constant cutting speed with different feed influence of cutting speed on the surface roughness profile the surface roughness increases with decrease in the cutting speed. this fact can be attributed to a technological contribution inherent to the cutting process, which produces high imperfection cutting surface, change in surface finish can be obtained geometrical model. the geometrical model doesn’t consider the important influence of cutting speed on surface finish (monkova and hloch, 2012). 3.3 surface roughness measurement there is a device available to measure the roughness of the surface. for measuring the roughness of the surface surtronic 3+ roughness measuring device (fig. 4) was used. the roughness of the surface depends on the finishing and the cutting parameters that are associated with the workpiece (wang et al., 2012). the surface roughness on the workpiece/sample are measured by talyrond surtronic for the roughness parameter of the workpiece. surface integrity study of ti-alloy using optimal cutting speed 74 figure 4: talyrond surtronic 3+ surface roughness measurment device figure 5: surface profile at cutting speed (a) 283 m/min, (b) 141 m/min, and (c) 71 m/min. depth of cut 0.5 mm, and feed rate 0.10 mm/rev (davim, 2010) 4 results and discussions a conventional lathe machine was used to produce the samples. measured data were recorded in tabular forms. the machining operation is carried out for three times in each speed to attaine the average surface roughness value. at every speed three surface roughness values were obtained and the average surface roughness is calculated from the three values. cutting speed study: the measured data (for three series of experimentations) were tabulated and surface roughness graphs were built in respect of individual cutting parameters (v, f, d). the graph in fig. 6 provides machining data where cutting speed was varied while feed rate and depth of cut were kept constatnt at the values of feed rate = 0.15 mm/rev and depth of cut = 1.1 mm. the surface roughness measured varies with various cutting speeds. the cutting speed is calculated by using the fundamental formula: 𝑣 = 𝜋 × 𝐷 × 𝑁 1000 where, 𝜋 = 3.14 d = 60 mm (as available) n = spindle speed in rpm mazid et al. (2022). international journal of engineering materials and manufacture, 7(3), 71-77 75 figure 6: cutting speed and ra graph (v and f kept constant) the above graph (fig. 6) describes the machining process for cutting speed optimisation. the graph is plotted between cutting speed (m/rev) and the average surface roughness (𝜇𝑚) values from the table and graph the optimum surface roughness value is found at a range of 80 m/min to 140 m/min cutting speed (v). these cutting speeds having the possible best surface roughness ra value of 1.5− 1.7 𝜇𝑚. when the cutting speed is minimum and maximum the surface roughness values are higher but when the cutting speed is in-between these values (80 – 140 m/min) better surface roughness values are obtained. feed rate study: similarly a second series of experiments were carried out while the feed rate was varied and cutting speed and depth of cut were kept constant. the data obtained were recorded in tabular form in an xl-sheet and the result was presented in graphical form (fig. 7) of variation of surface roughness inrespect of varible feed rate. the graph in fig. 7 was produced using the experimented data describing machining process where the feedrate is turning operation in sixteen different steps of the workpiece from 0.035 mm/rev to 0.25 mm/rev where the cutting speed and depth of cut are kept constant and at each step the surface roughness is measured. accepted constatnt cutting speed = 80 m/min and depth of cut = 1.1 mm. figure 7: feed rate and ra graph ( v = 80 m/min, d = 1.1 mm kept constatnt) the above graph describes the machining process for feedrate optimisation. the graph was plotted using federate (m/rev) and the surface roughness (𝜇𝑚). from the table and graph the optimum surface roughness is obtained inbetween feedrate from 0.055 mm/rev to 0.1 mm/rev. it was found in the graph as the feedrate increases, surface roughness also increases. the surface roughness value is 0.7 𝜇𝑚 which is obtained at feedrate 0.05 mm/rev. depth of cut study: the graph given below in fig. 8 was built of tabulated data describing the machining process for depth of cut variation, variation from 0.3 mm to 1.8 mm by increasing 0.1 mm for every step up to 1.8 mm, the sixteen different depth of cut were used and relevant surface roughness values were measured using talyrond surtronic 3+ machine. in this series of experiments cutting speed and feed rate were kept constant. these values are taken from the previous above two graphs, the constant values were cutting speed = 81 m/min and feedrate = 0.055 mm/rev. surface integrity study of ti-alloy using optimal cutting speed 76 figure 8: depth of cut and ra graph (f = 0.055 mm/rev, v = 80 m/min kept conatant) the graph given above (fig. 8) describes the machining process for depth of cut optimization. the graph was plotted using depth of cut (mm) to surface roughness (𝜇𝑚), the best surface roughness values are obtained for values of depth of cut within the range of 0.3 mm and 0.5 mm. the surface roughness value at 0.5 mm depth of cut is 0.4 𝜇𝑚 as the depth of cut increases the surface roughness value also increases. 5 conclusion and future scope after performing operations on the ti-alloy (ti-6al-4v) using uncoated carbide tool and processing the obtained series of data the following conclusion can be made: best surface roughness values can be expected while using cutting speed within the range of 80 m/min to about 140 m/min (fig. 6). beyond these values starting from 150 m/min upto 210 m/min surface roughness values rapidly increasing from 0.80 μm to 6 μm. strangely cutting speeds beyond 210 m/min and upto 340 m/min (maximum as we could set in the available lathe) surface roughness remains almost same around 6 μm. this creates a thirst to look for beyond that limit of cutting speed and hence new cutting tool materials that could survive high speed cutting. best surface roughness expected to be obtained while using feed rate 0.052 mm/rev to 0.105 mm/rev. it is evident from the graph (fig. 7) that the feed rates ranging from 0.10 mm/rev and 0.20 mm/rev surface roughness increases but reasonabley stable and it goes upto maximum 3 μm which is not that bad for many parts. but that value crucially increases (worsens) while using feed rate beyond 0.20 mm/rev and surface roughness rapidly increases upto 7 μm which may not be acceptable for many parts made of valuable ti-alloys. best surface roughness possible to obtain while using depth of cut within the range of 0.30 mm to 0.50 mm (fig. 8). depth of cut within the range of 0.60 mm to 1.60 mm higher but reasonably stable values. but once feed rate goes beyond 1.6 surface rougness values geometrically increases, suggesting not to use this range of depth of cut. from conclusion as evident that these are opening eyes for scienbtist to think about the plastic deformation beyond temperature 2,000° while so far we know a little about plastic deformation only bellow 1,000° for machining general steel materials. it is essential to look for plastic deformation process in machining hard materials. searching for chip formation phenomeno and behaviour of cutting tools and dynamic systems at a temperature range beyond 2,000° for hard materials or known as difficult to machine materials. authours sincerely agreed, since this is a pioneering work, in future more accurate experimentations, not only searching for best ranges of machining parameters, but searching for new and tougher cutting tool materials that could survive at high speed cutting. this certainly reduces the machining cost enhancing the sustainability and open up the science of plastic deformation of difficult to machine materials at much higher temperature. acknowledgement: the authours acknowledge sincere help of mr randall stock and mr garry hoar (retired) of cqu machine shop for preparing samples. the work was partially supported by cqu nsrg grant 2019. references 1. ahsan, k. b., mazid, a. m., clegg, r. e., pang, g. k. h. (2016). morphological investigation of ti-6al-4v chips produced by conventional turning. international journal of machining and machinability of materials, 18 (1/2), p. 138-154. 2. akkuş, h., & yaka, h. (2021). optimization of cutting parameters in turning of titanium alloy (grade 5) by analysing surface roughness, tool wear and energy consumption. experimental techniques, 1-12. mazid et al. (2022). international journal of engineering materials and manufacture, 7(3), 71-77 77 3. ezugwu, e., wang, z. (1997). titanium alloys and their machinability – a review. journal of material processing technology, 68, pp.262-274. 4. guo, y.b. & li, w., jawahir, i.s. (2009) surface integrity characterization and prediction in machining of hardened and difficult-to-machine alloys: a state-of-art research review and analysis. machining science and technology, 13 (4), 437–470. 5. jawahir i. s., brinksmeier, e., m’saoubi r., aspinwall d. k., outeiro j. c., meyer d., umbrello d., jayal a. d. (2011). surface integrity in material removal processes: recent advances. cirp annals – manufacturing technology 60 (2011) 603-626. 6. machado, a.r. & wallbank, j. (1990) machining of titanium and its alloys — a review. proceedings of the institution of mechanical engineers, part b: journal of engineering manufacture, 204 (1), pp.53–60. 7. mazid, m. a., hasan, m. s. and ahsan, k. b. (2019) an investigation on optimum process parameters in terms of surface roughness for turning titanium alloy ti-6al-4v using coated carbide. international journal of engineering materials and manufacture. 4(4), 137-145. 8. monkova, k. & hloch, s. (2012) the dependency of the tool life on the cutting speed at the investigation of the tool with specific geometry. advanced materials research, 622–623, .347–351. 9. j. paulo davim (2010). surface integrity in machining. springer. 10. revankar, g. d., shetty, r., rao, s. s., & gaitonde, v. n. (2014). analysis of surface roughness and hardness in titanium alloy machining with polycrystalline diamond tool under different lubricating modes. materials research, 17(4), 1010-1022. 11. rodrigues, a. p., pai, p. s., & d’mello, g. (2016). surface roughness evaluation in high-speed turning of ti6al-4v using vibration signals. indian journal of advances in chemical science s1, 160, 164. 12. umasekar, v. g., gopal, m., rahul, k., saikiran, s., & mowli, g. s. (2006). investigation of surface roughness in finish turning of titanium alloy ti-6al-4v. carbon, 100, 0-029. 13. vinayagamoorthy, r., & xavior, m. a. (2014). investigations on the machinability of titanium alloy during precision turning. middle-east journal of scientific research, 22(12), 1782-1787. 14. withers, p.j. & bhadeshia, h.k.d.h. (2001) residual stress. part 2–nature and origins. materials science and technology, 17:4, 366–375. international journal of engineering materials and manufacture (2021) 6(3) 132-140 https://doi.org/10.26776/ijemm.06.03.2021.04 ameer j. nader and saad k. shather production and metallurgy engineering department university of technology, iraq baghdad e-mail: pme.19.17@grad.uotechnology.edu.iq references: ameer and saad (2021). influence of abrasive water jet (awj) on surface roughness. international journal of engineering materials and manufacture, 6(3), 132-140. influence of abrasive water jet (awj) on surface roughness ameer j. nader and saad k. shather received: 27 february 2021 accepted: 01 may 2021 published: 15 july 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract abrasive water jet (awj) is one of the most advanced and valuable non-traditional machining processes because of its massive advantages of removing metals ranging from hard to soft. this paper focused on studying the influence of jet pressure, feed rate and standoff distance on surface roughness during cutting carbon steel using abrasive water jet cutting. a surface roughness device assessed the surface roughness by performing sixteen experiments to identify the distinct texture of the surface. based on the experiences, the best surface roughness value was 3.14 μm at jet pressure 300 mpa, standoff distance 4mm and feed rate 30 mm/min. the taguchi method was introduced to implement the experiments and indicate the most influential process parameters on average surface roughness. the experimental results reveal that feed rate has a significant effect on average surface roughness. keywords: abrasive water jet, feed rate, surface roughness, carbon steel. 1 introduction abrasive water jet (awj) cutting machine is one of the most superior modern machining technologies utilized in the manufacturing industry for material processing. abrasive water jet (awj) cutting is a non traditional machining technology [1-2]. awj cutting operation is based on the material erosion by high-speed water jet with abrasive particles [3]. awj cutting process is a powerful technology for machining different engineering materials and a wide range of thicknesses. awj cutting is broadly utilized in machining materials such as brass, aluminum, titanium, steel, inconel, stone, and any composites and glass [4-6]. no heat-affected zone, ability to machine a wide range of materials, non-contact of the tool with a workpiece and low machining force on the work surface has raised the use of abrasive water jet machining over other machining processes. [7-8]. the influence of machining parameters on the surface topography and surface roughness of titanium metal by awj was studied and identified the parameters which affects the surface roughness. it was observed that the standoff distance had proportional relationship with average surface roughness [9]. the effect of awj machining parameters such as jet pressure, and standoff distance on surface roughness of brass 360 was investigated. they found that the water jet pressure as the most influential factor related to surface roughnes [10]. taguchi method is the most suited method to identify the optimized parameter with the reduced number of experiments without altering its quality [11-12]. the taguchi experiment method was used to conduct an analysis based on a study of average surface roughness in abrasive water jet (awj) cutting of cast iron metal. transverse speed, water pressure, standoff distance and material feed rate are all known as process parameters that affect the roughness of the surface. the most crucial factor influencing surface roughness was water pressure, which had an inverse proportional relation with average surface roughness [13]. the influence of awj process parameters such as water pressure, nozzle traverse speed, abrasive mass flow rate and standoff distance on surface roughness (ra) of aluminium was studied . was studied the result indicate that the use of high water pressure and low standoff distance is preferred to obtain good surface finish [14]. the taguchi method based analysis of variance (anova) was proposed to optimize the abrasive water jet machining process parameters to decrease average surface roughness. the importance of process parameters was achieved through variance analysis based on the l9 orthogonal array, which revealed the most important parameters being feed rate [15]. many researchers have been carried out on various parameters of awjm. little literature was available on influence standoff distance, pressure jet, and feed rate on average surface roughness and dimensional accuracy. the present study highlights experimentally the influence of metal cutting variables such as pressure jet, feed rate and standoff distance on the surface roughness through the abrasive jet machining of the carbon steel alloy. influence of abrasive water jet (awj) on surface roughness 133 2 material abrasive water jet (awj) experiences were carried out on a sample of carbon steel of (10 x 40 x 118) mm dimensions with the following chemical composition according to the standard bs en10025-2: table 1: chemical composition of carbon steel (measured). c % mn % si % p% cu % mo % cr % s % al % co % ni % fe % 0.14 1.30 0.47 0.028 0.18 0.045 0.16 0.017 0.004 0.012 0.15 97.4 carbon steel is non-alloy steel in which carbon is a fundamental component that determines its grade. carbon steel is strong, good formability and wedability, shock-resistant, and strengthening by coldwork; this metal is often the most practical choice. and it is widely used in various fields for various purposes such as constructing bridges and buildings, automobile industries and oil indistry [4]. according to bs en 10025-2, the sample has the name and number s355j2 and 1.0577, respectively, in addition to the following mechanical properties: table 2: mechanical properties of carbon steel (measured). yield strength (mpa) tensile strength (mpa) elongation after fracture (mm) 355 470 to 630 22 l 20 t figure 1: photograph of the carbon steel workpiece 3 machine the experimental setup for the abrasive water jet machine (model no. 3020; yonoda, china) is shown in figure 2. the machine uses a 3-stage plunger-type high-pressure pump that can generate high pressures up to 413 mpa (60 000 psi). the machine has a water discharge capacity of 2.6 litres/min at this rated pressure. the maximum traverse speed of the machine is limited to 1200 mm/min and the motion is controlled by a cnc, a motorized z-axis for vertical movement. the working and technical specifications of the machine are given in table 3. all the experiments were conducted at 90 o jet impingement angles only. the cutter head consists mainly of two nozzles, one of them is primary (jewel orifice) and the other is secondary (focusing or mixing tube). the primary nozzle is the orifice in which exits water form the cutting stream. typically jewels are created from ruby, diamond, or sapphire, a “jewel” mounted in a steel insert. its diameter ranges from 0.007” to 0.020” (0.178 – 0.51) mm [16], notice figure 3. secondary nozzle sometimes refers to as mixing tube or focusing tube. this is a tube manufactured from a tough material that concentrates the water and abrasive into a coherent beam for cutting. typically, a mixing tube has a diameter of 0.030″ (0.76 mm) [16], notice figure 3, to the abrasive water jet nozzle to cut efficiently and improve the life of components . the jewel orifice must be accurately aligned in the nozzle body. after the pure water jet is formed, abrasives are added utilizing either the suspension or injection methods as shown in figure 4. the significant parameters of the abrasives are the mechanical behavior, the material structure and hardness, grain size, grain shape, and distribution [17]. ameer and saad (2021): international journal of engineering materials and manufacture, 6(3), 132-140. 134 figure 2: experimental setup for abrasive water jet machining. table 3: technical specifications of awjm figure 3: orifice and mixing tube. machine yonoda, china maximum transverse speed 1200 mm/min impact angle 90 ○ mixing tube length 76.2 mm focusing/mixing tube diameter 1.02 mm orifice diameter 0.3 mm maximum working pressure 413 mpa maximum distance from the workpiece 10 mm table size 2000 x 3000 mm operation program nc studio v10 influence of abrasive water jet (awj) on surface roughness 135 red garnet 80 mesh with an average particle size of 0.180µm is used as an abrasive material throughout the experiment, which is the most popular kind of abrasive utilized in awj cutting machine because of the following facts. (1) it is widely available, thus relatively inexpensive. (2) it is an inert material that does not interact with the material to be cut. (3) when hitting the target, it breaks down, forming sharp edges, thus making better cutting performance. [18]. figure 4: injection and suspension system [17]. 4 experimental procedure the machining was done by considering the jet pressure, standoff distance and feed rate and each process parameter were varied over four levels, as shown in table 4. based on the taguchi’s design philosophy, standard orthogonal array l16, as shown in table 5, has been selected to complete the experiment and to estimate its impacts on surface roughness. cutting was performed on a sample of carbon steel having dimensions (10 x 40 x 118) mm. after machining was completed, surface roughness on the cut surface was measured in terms of the average roughness ra, using a surface roughness measuring device at various zones of the cut surface. table 4: process control parameters and levels parameter units level i level ii level iii level iv pressure jet mpa 225 250 275 300 feed rate mm/min 30 50 70 90 standoff distance mm 1 2 3 4 table 5: experimental design no. pressure (mpa) feed rate (mm/min) standoff distance (mm) 1 225 30 1 2 225 50 2 3 225 70 3 4 225 90 4 5 250 30 2 6 250 50 1 7 250 70 4 8 250 90 3 9 275 30 3 10 275 50 4 11 275 70 1 12 275 90 2 13 300 30 4 14 300 50 3 15 300 70 2 16 300 90 1 ameer and saad (2021): international journal of engineering materials and manufacture, 6(3), 132-140. 136 5 measurement of surface roughness roughness is the measure of the texture of a machined surface. it is quantified by vertical deviation of the real surface. roughness is usually defined as a measured surface's high-frequency short wavelength. the abrasive water jet experiments were conducted on carbon steel based on taguchi’s l16 orthogonal array using jet pressure, feed rate and standoff distance. there are several techniques employed to measure surface roughness. the method adopted to measure the surface roughness during the present investigation is ra (the arithmetic mean of the peaks and valleys from the mean line through a sampling length). it is the most widely used and internationally employed parameter for the measurement of surface roughness. this method can be defined by the mean deviations present above and below the mean plane of the surface measured within a certain distance. it is referred to (ra) and can be calculated from the following equation [19]: 𝑅𝑎 = 1 𝑙𝑚 ∫ |𝑦| 𝑥=𝑙𝑚 𝑥=0 𝑑𝑥 (1) where lm is the profile length used for parameter evaluation, y is the ordinate of the centerline profile, as shown in figure 5. figure 5: roughness average (ra) [18]. the portable electronic device (pocket surf iii) is used to measure the surface roughness as shown in figure 6, where traversing length (10) mm, measuring a range of (0.3 – 6.35) μm and accuracy (±0.05) μm. the average surface roughness is calculated using four readings of the roughness from the surface of the machined workpiece and take the average of these readings as the final value of the average surface roughness. figure 6: photo of the surface roughness measuring device. influence of abrasive water jet (awj) on surface roughness 137 6.1 the design of experiments (doe) the method of designing experiments when taking into account process parameters at different levels is known as design of experiments (doe). taguchi's method for experimental design offers a simple, systematic, and efficient approach for determining the efficiency, expense, and quality of an experiment (aydin et al., 2010). statistically designed experiments are conducted more efficiently as they consider many parameters simultaneously. they can identify significant interactions with a minimum number of experiments, unlike conventional experimentation, a complete factorial experimental set consisting of abrasive strain, standoff distance, and feed rate as process parameters, each at 4-levels with all possible combinations, totaling 16 experiments, was chosen based on the above. the process parameters range is specified in table 5. 6.2 analysis data minitab is a widely used mathematical software program in fields such as statistics, mathematics, sports, economics, and engineering. it is highly interactive program that allows data entry, anova analysis, regression analysis, doe design, reliability/survival tests, taguchi analysis, drawing control charts for processes, plotting time series plots, multivariate tests, and other tasks very simple and time-saving. it is the most effective method for quality improvement initiatives based on results. minitab (version 17) was used in this study for anova analysis and plotting various graphs [20]. in the analysis of variance (anova), the f ratio was applied to calculate the important process parameter on the material removal rate and average surface roughness. an f ratio is estimated from the experimental results and then compared to the critical value. if the f ratio estimated is larger than the f critical value, it is an indication that the statistical test is important at the confidence level selected [21]. in this work, an analysis of variance was carried out for the confidence level of 96.1 %. it was found that the factors feed rate (t) and pressure (p) was the most significant factor impacting the assessment of the average surface roughness. to observe the impact of important factors, the results of the response parameters are displayed through graphs. the experimental tests are designed for four levels and three parameters. 7 results in this section, the influence of the process parameters such as jet pressure, feed rate and standoff distance on the surface roughness during awj cutting of carbon steel was examined. table 6 shows the predicted and measured results of surface roughness for the target material samples by (taguchi design). figure 7 explains the main effects plot of process parameters on the surface roughness. four readings of surface roughness for each specimen were recorded and the average of them was taken for the workpiece. the predicted average surface roughness values were compared with the measured values, as presented in table 6. the results of the surface roughness (ra) were close between predicted and measured . the ability of independent value to predict the surface roughness was (96.1%). this means that the correlation coefficient between the dependent variable's measured value and the expected value is good table 6: measured and predicted surface roughness n0. pressure (mpa) feed rate (mm/min) standoff distance (mm) measured ra (μm) predicted ra (μm) 1 225 30 1 3.46 3.46 2 225 50 2 4.10 4.03 3 225 70 3 4.08 4.26 4 225 90 4 4.86 4.74 5 250 30 2 3.38 3.44 6 250 50 1 3.86 3.85 7 250 70 4 4.37 4.29 8 250 90 3 4.51 4.52 9 275 30 3 3.29 3.19 10 275 50 4 3.64 3.80 11 275 70 1 3.89 3.80 12 275 90 2 4.21 4.23 13 300 30 4 3.14 3.16 14 300 50 3 3.62 3.52 15 300 70 2 3.74 3.72 16 300 90 1 3.91 3.99 ameer and saad (2021): international journal of engineering materials and manufacture, 6(3), 132-140. 138 figure 7: main influence for average surface roughness. 7.1. influence of jet pressure on the average surface roughness by conducting experiments, it’s observed that average surface roughness decreases from 4.86 to 3.14 μm when increasing the pressure from 225 to 300 mpa, as shown in figure 8, taking into consideration the standoff distance. it is seen that the average surface roughness improves with a rise in hydraulic pressure up (inverse relationship). a raise in the jet pressure causes a rise in the kinetic energy of the abrasive particles to the maximum level, brittle abrasives break down into smaller ones. this result decreases the waves developed on the machined surface. consequently, it produces a smooth finish with a decrease in the surface roughness value [10]. figure 8: a plot of influence of jet pressure on the average surface roughness (ra). 2.5 3 3.5 4 4.5 5 5.5 225 250 275 300 a v e r a g e s u r f a c e r o u g h n e s s ( μ m ) pressure (mpa) 30 mm/min 50 mm/min 70 mm/ min 90 mm/min influence of abrasive water jet (awj) on surface roughness 139 7.2. influence of feed rate on the average surface roughness by conducting experiments, it’s observed that average surface roughness increases from 3.14 to 4.86 μm when increasing the fee rate from 30 to 90 mm/min, as shown in figure 9, taking into consideration the standoff distance. it is seen that the average surface roughness improves with a low feed rate down (direct relationship). the reason for this is due to the participation of a more significant number of the higher kinetic energy of abrasive particles that cut the metals smoothly [15]. figure 9: a plot of impact of feed rate on the average surface roughness (ra). 7.3. influence of standoff distance on the average surface roughness by conducting experiments, it’s observed that average surface roughness increases from 3.14 to 4.86 μm when increasing the standoff distance from 1 to 4 mm, as shown in figure 10, taking into consideration the jet pressure. it is seen that the average surface roughness improves with a low standoff distance down (direct relationship). the reason for this is because that rise in standoff distance produces divergence profile and scattering effect of the jet after exit of the foucsing nozzle tip, thereby decreasing the density and kinetic energy of abrasives that caused poor machining efficiency and thus provided higher surface roughness. because of that, at lower standoff distance, the abrasives have higher density and kinetic energy, thereby cutting the workpiece smoothly and giving better surface finish [9]. figure 10: a plot of impact of standoff distance on the average surface roughness (ra). 2.5 3 3.5 4 4.5 5 5.5 30 50 70 90 a v e r a g e s u r f a c e r o u g h n e s s ( μ m ) feed rate (mm/min) 225 map 250 mpa 275 mpa 300 mpa 2.5 3 3.5 4 4.5 5 5.5 1 2 3 4 a v e r a g e s u r f a c e r o u g h n e s s ( μ m ) standoff distance (mm) 30 50 70 90 ameer and saad (2021): international journal of engineering materials and manufacture, 6(3), 132-140. 140 8 conclusions from the experimental tests results and the above discussions, the following conclusions can be drawn: 1. the most significant control factors on surface roughness were pressure jet and feed rate. standoff distance has a lesser influence on surface roughness. 2. average surface roughness improves with a raise in jet pressure and decreases feed rate and standoff distance; this is due to the participation of a more significant number of the higher kinetic energy of abrasive particles that cut the metals smoothly. 3. the result reveals that the jet pressure 300 mpa, the feed rate 30 mm/min and the standoff distance of 4 mm are the optimal process parameters to obtain low surface roughness on carbon steel, with ra values of 3.14 μm. references 1. sreekesh k., govindan p., a review on abrasive water jet, int. j. recent adv. mech. eng. 3 (2014) 153–158. 2. natarajan y., murugesan p. k., mohan m., ahmed s., abrasive water jet machining process: a state of art of review. journal of manufacturing processes 49 (2020) 271–322. 3. yuvaraj n., pradeep kumar m., multiresponse optimization of abrasive water jet cutting process parameters using topsis approach, mater. manuf. process. 30 (2015) 882–889. 4. gupta k. j., abrasive water jet machining of engineering materials springer (2020). 5. dharmagna r. tripathia, krupang h. vachhania, soni kumarib, dinbandhua, kumar abhisheka. experimental investigation on material removal rate during abrasive water jet machining of gfrp composites. materials today: proceedings (2020). 6. bhandarkar v., singh v., gupta t.v.k., experimental analysis and characterization of abrasive water jet machining of inconel 718. materials today: proceedings (2019). 7. mohamad w.n.f., kasim m.s. , norazlina m.y , hafiz m.s.a , izamshah r. , mohamed s.b., effect of standoff distance on the kerf characteristic during abrasive water jet machining. results in engineering 6 (2020) 100101. 8. bagchi a., srivastava m., tripathi r., chattopadhyaya s.. effect of different parameters on surface roughness and material removal rate in abrasive water jet cutting of nimonic c263. materials today: proceedings (2019). 9. vasanth s., muthuramalingam t., vinothkumar p., geethapriyan t., murali g., performance analysis of process parameters on machining titanium (ti-6al4v) alloy using abrasive water jet machining process, procedia cirp 46 (2016) 139–142. 10. naresh babu m, muthukrishnan n.,”investigation on surface roughness in abrasive water-jet machining by the response surface method,”mater manuf processes 29 (2014) 1422–8. 11. kumar s., gajendran s., kesavan r., estimation of optimal process parameters for abrasive water jetmachining of marble using multi response techniques. materials today: proceedings 5 (2018) 11208–11218. 12. badgujar p.p., rathi m.g., taguchi method implementation in abrasive waterjet machining process optimization. international journal of engineering and advanced technology (ijeat), 3 (2014), 66-70. 13. aultrin k.s.j., anand m.d., optimization of machining parameters in awjm process for an copper iron alloy using rsm and regression analysis, int. j. emerg. eng. res. technol. 2 (2014) 19–34. 14. shibin r., anandakrishnan v., sathisha s., sujana v.m., investigation on the abrasive water jet machinability of aa2014 using sic as abrasive. materials today: proceedings (2019). 15. selvan m., raju n.m.s., h. k. sachidanand h.k., “effects of process parameters on surface roughness in abrasive waterjet cutting of aluminium,” front. mech. eng. 2012, 7(4): 439–444. 16. maneiah d., shunmugasundaram m. , raji reddy a., and begum z., optimization of machining parameters for surface roughness during abrasive water jet machining of aluminium/magnesium hybrid metal matrix composites. materials today: proceedings (2020) 1. 16. jegaraj j. j. r. and babu n. r., “a strategy for efficient and quality cutting of materials with abrasive waterjets considering the variation in orifice and focusing nozzle diameter," international journal of machine tools and manufacture, vol. 45, no. 12-13, pp. 1443-1450, oct. 2005. 17. khalid w., hussain m., nasir bashir m., quaz m.m., ali i., bhatti j., ur rehman h., "development of water jet cutting and study on different parameters," journal of applied and physical sciences, vol. 5, no.3, pp. 8187, 2019. 18. el-hofy h. a., advanced machining processes, united states of america: mcgraw-hill, 2005. 19. klichová d., sitek l, hloch s. valentinčič j. ,advances in water jetting springer (2019). 20. satyanarayana b. and srikar g., "optimization of abrasive water jet machining process parameters using taguchi grey relational analysis (tgra)," international journal of mechanical and production engineering, vol. 2, no. 9, pp. 82-87, 2014. 21. aydın g., karakurt i.and aydıner k., "a study on the use of taguchi approach in awj machining of the granite," international mining congress and exhibition of turkey, vol. 22, pp. 111-116, 2011. international journal of engineering materials and manufacture (2021) 6(4) 319-323 https://doi.org/10.26776/ijemm.06.04.2021.08 s. islam masteq software pty ltd collins street tower, level 3, 480 collins street melbourne, vic 3000, australia e-mail: saiful.islam@masteq.com.au reference: islam, s. (2021). artificial intelligence in healthcare. international journal of engineering materials and manufacture, 6(4), 319-323. artificial intelligence in healthcare saiful islam received: 11 april 2021 accepted: 23 july 2021 published: 01 october 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract artificial intelligence (ai) is the ability of a computer program or machine to think or learn that possess human-like intelligence. these computing devices use this intelligence to provide services such as speech recognition, natural language processing and identifying disease in healthcare. to work efficiently, ai requires adequate data that is used to train systems. the efficiency of any ai system depends on the availability of this data. this article is mainly focused on recent advents in the technology of artificial intelligence. the importance of ai in healthcare is identified and described in this report. the applications of artificial intelligence in healthcare such as clinical care, medical research, drug research and public healthcare are briefly discussed here. the purpose of this article is to demonstrate that artificial intelligence is being used in all domains of life and particularly in the field of healthcare. this report presents the role of artificial intelligence in healthcare. keywords: artificial intelligence, neural network, machine learning, healthcare, medicine, diagnosis. 1 introduction artificial intelligence deals with the computer or any computing resources that perform some tasks which usually requires human-like intelligence. ai has enabled significant progress in natural language processing, speech recognition, image processing, computational intelligence, and many other areas. all these advances in computer science open many opportunities in artificial intelligence by enhancing human decision making in healthcare. recent research and studies show that ai can perform medical and clinical diagnostics at a level equal to experienced clinicians. ai can be integrated and applied to many healthcare applications including detection of disease, delivery of health services and drug discovery. ai has the potential to help address important healthcare challenges, but the efficiency of ai system depends on the availability of quality health data which is used to train system. at the same time, health data has many privacy issues associated with it, collecting health data of the patient, and sharing those data to user is practically difficult task and quite expensive. there are many private sector companies which are collecting and selling those data. some major applications of ai in healthcare organizations are described below: a. medical research ai can be used to analyse and identify patterns from large complex datasets faster than compared to any other previously developed systems. ai can also be applied for searching scientific articles for research and studies. researchers have also developed an artificial intelligence-based robo-scientist called eve which is designed to make drug discovery faster than ever. b. healthcare organization ai can be used to improve the patient experience which can be in the form of an app which facilitates interaction with patients. this app collects appropriate information from patients and delivers to clinicians that help them to deliver appropriate treatment. c. clinical care ai systems help in identifying diseases by analysing clinical data and research publications. possible uses of ai in clinical care includes: artificial intelligence in healthcare 320 i. medical imaging: ai shows promising results in detecting diseases such as breast and skin cancers, eye diseases and other medical implications by systematically collecting medical scans and other health records. ii. echocardiography: using ultrasonic systems integrated with ai helps in detecting patterns of heartbeats and diagnose coronary heart disease. such a system is implemented at john radcliffe hospital in oxford. iii. surgery: robotic arms controlled by ai are used in clinical surgery. d. public health ai has the potential to identify infectious diseases with their cause sources like water contamination, air pollutants, and others. ai also helps in identifying adverse drug effects by scanning drug content. e. patient and consumer-facing applications several apps are available in markets that offer healthcare advice and personalized health assessments. these apps identify medical implications by communicating with the patient in the form of a chatbot. artificial intelligence-based systems have some limitations based on where it is applied. ai in healthcare also has some limitations which are listed below. i. digital health data is required to train ai based systems and apps to maintain the consistency of this digital data. ii. humans have some attributes that are difficult for ai to process such as compassion. 2 research methodology the research article is secondary in nature. the author has analysed empirical works of celebrated professionals and respected organizations to find the outcome of this research paper. 3 ai technology in healthcare following are the major fields in which artificial intelligence can aid modern health care & recent projects which are being implemented. 3.1 using artificial intelligence to improve hospital inpatient care according to daniel b. neill (2005), ai has the potential to improve many patients' care processes. integrating ai in healthcare will maximize the efficiency of the healthcare system and minimize the risk of side effects by recommending appropriate diagnostic tests. ai uses previous health data to discover new medical knowledge, it also monitors the patient’s health to collect train dataset which ultimately increases system performance. in this paper, the author suggested one way to collect data of health records using electronics health records (ehr) as per the health information technology for economic and clinical health (hitech) act. the author shows recent advances in ai system by showing case studies of various healthcare systems. clinical decision support systems (cdss) are one of the most successful healthcare applications which primarily focus on the diagnosis of a patient’s condition by giving symptoms and other demographic information as input to system. artificial intelligence is combined with machine learning to detect and identify diseases based on large pool of healthcare data. artificial intelligence analyses past data and learns the pattern. it analyses all the cases of disease and learns about the symptoms of the disease. it then creates filters which can alert prior to shock & organ dysfunction. artificial intelligence helps doctors by providing pre-diagnosis and assist them to move forward to the right direction of treatment when a patient visits the hospital. several inhibitors of beta-secretase are used for the treatment of alzheimer's. a machine learning (ml) algorithm is developed considering structural, physical and chemical characteristics of these inhibitors. ml, multilayer perceptron (mlp), logitboost (lb), & decision table (dt) functions were applied to set of molecular descriptors for an active and inactive compound in 5-fold cross validation. the highest accuracy achieved by this data set was 88.86% by mlp. the developed model is currently being used for selection of possible drug candidate from the database of these compounds. 3.2 primary healthcare using artificial intelligence khairnar, v. d., saroj, a., yadav, p., shete, s. & bhatt, n. (2019) has proposed the new technology which emphasizes in providing proper health care to the remote patients by keeping in mind their poor financial conditions, lack of facilities and lack of means of transportation by prescribing them the precise medicine within a millisecond excluding the communication delay with the help of artificial neural network (ann) by converting the received voice messages from the patient to text message, and in replay to their solution the medicines are also sent by text messages. the technology includes neural network, natural language toolkit, google api, natural language processing, programming language-python, interactive voice response, php, html, r studio and artificial neural network. the main objective of this technology is to collect the data related to various diseases and medicines to cure the disease to create an environment that focuses on the high quality of patient health care. using this technology, they enhance the quality of health care and bridge the gaps in healthcare services, which significantly saves the life of the person in the absence of the doctor. recently doctors developed an algorithm with the help of google to detect the cardiovascular risks to a person by recognizing hidden patterns in retinal images. more than 280,000 patients’ retinal images were utilised to train and understand the hidden pattern [3]. it was verified on two distinct datasets of 12,026 & 999 patients, respectively. another machine makes out the peculiarities of a blood vessel and inform different islam (2021): international journal of engineering materials and manufacture, 6(4), 319-223 321 variables such as age (+/3.3 yrs.), smoking status, systolic blood pressure, and hba1c by analysing images. detection of diabetic retinopathy & macular edema was automated just by analysing retinal fundus photographs at the same way. 3.3 mobile based healthcare management using artificial intelligence to propose the proper health care management system, amiya, k., tripathy, a.k., carvalho, r., pawaskar, k., suraj y. and vijay, y. (2015, pp 1-6) proposed the system which consists of mobile-based heart rate management so that the data can be transferred and diagnosed based on the heart rate and communicated directly to the doctor. it also includes the video conferencing facility which helps to communicate face-to-face with the doctor and get out of the problem, the system consists of doc-bot module which gives solution to the disease of the patient and the module is implemented in artificial intelligence markup language (aiml), the doc-bot uses feed-forward neural network for classification of the disease and solving them. the proposed system also consists of the online blood bank which provides the latest details related to the type and quantity of the availability of the blood in different hospitals. 3,4 mapping the challenges of artificial intelligence in the public sector sun, t. q. & medaglia, r. (2019) focused on adaption of the artificial intelligence (ai) system in ibm watson in public healthcare to map to analyse how the three groups of stakeholders (government policymakers, hospital managers/doctors and information technology (it) firm managers) receive the challenges of artificial intelligence (ai) in public sector. artificial intelligence is the most potential in doing transformative work – mining medical records, assisting repetitive jobs and designing treatment plans. the system focuses on huge data collection related to the various diseases and their treatment, huge collection of books, articles, and notes related to various medicines so that no disease should be left out which does not have its treatment. machine learning governs and trains complicated neural networks such as ibm watson cloud & targeted realtime early warning system (t.r.e.w.s.) [17]. these sophisticated systems analyse age, bmi, heart rate, exercise habits, eating habits, sleep pattern and human’s psychological behaviour through various sensors such as smartwatch, health band, browsing history, mobile phone activity etc. once the data is uploaded on the cloud, this data is categorized and analysed with the help of cognitive networks. 3.5 artificial intelligence image recognition in healthcare. gavrilov, d., melerzanov, a., schelkunov, n. & gorodilov, a. (2018) focused on one of the most dangerous cancer tumors – melanoma. as melanoma does not have the painful symptoms in the early stage so the cancer is diagnosed late. the proposed system states the using of the computer vision to solve the problem of detecting melanoma at an early stage. after the introduction of such a diagnosis, it becomes possible for the expert to take a proper decision and based on that decision various tools are used such as telemedicine. the system is based on the deep convolutional neural network, it uses imagenet large scale visual recognition challenge (ilsvrc) which provides proper image of the disease. they used the imagenet challenge to prepare inception of the disease. the system also proposed the online skin check-up so that every user can check his/her moles for melanoma risk online without any cost. the system success rate is 91% of recognition of skin disease. 3.6 artificial intelligence contribution to ehealth application. cabestany, j., rodriguez-martín, d., pérez, c., & sama, a. (2018) proposed the system to analyse how artificial intelligence (ai) technique can improve the management of data generated by the ehealth activity. in this system, they have developed a wearable device that allows continuous monitoring of the patient's disease. this new invented device “holter” will help neurologists to diagnose more accurately the disease of the patient and let them to take critical decisions about the medicine and the treatment related to the disease. this new wearable device consists of microcontroller to manage all peripherals, a set of sensing components, communication module-based bluetooth technology and a power management system that can minimize the internal consumption during its execution period. the result detected by the wearable device is then analysed through a set of various algorithms to diagnose the disease and help to reach through its treatment. to understand how data is collected by this new computing device, they have proposed the four different levels of multi-layered architecture, which include – sensing layer, networking layer, service layer and interface layer which provides an interface to the user and other applications. 3.7 application of artificial intelligence to cure disease chanchaichujit, j. (2015) proposed a system that is based on the control and management of tuberculosis (tb) using artificial intelligence (ai). the author suggested that the tb disease is caused by m. tuberculosis bacteria (mtb), this bacteria mainly affects the lungs and that tb is an airborne disease which spread through the air with the contact of mtb caused person. the author has given three stages to get controlled form tb – diagnostic connectivity, data repository and gateway, and data representation and applications. the author conveys that one of the key success factors for developing the artificial intelligence (ai) for tb detection is the training of the algorithm with a huge amount of the data, which will later help them to differentiate the infection from the normal cases. the author uses the dac4tb, which consists of a huge amount of data to cure tb, which includes data of multiple tb tests, cxr, afb, genexpert and tb cultures of many patients and various design algorithms to cure tb disease. with the help of artificial intelligence in healthcare 322 such more comprehensive results, physicians and healthcare workers can make better recommendations. artificial intelligence creates a valid clinical pathway to reduce the cost and time of traditional methods. piyush mathur & kamal maheshwari conducted a study under the aegis of ayasdi clinical variation management (cvm) application where 1,786 patients were analysed [7]. all the patients had colorectal surgery in 2015-2016. the program analysed multidimensional data sets under supervision. results segregated their data set into 9 different groups with similarity analysis based on ketorolac dosage. this dosage is a non-steroidal anti-inflammatory drug (nsaid) which is usually used in surgery to treat postoperative pain. in addition, they identified a link to low intraoperative fluids and relatively lower length of stay along with lower cost group. this eventually broaden their clinical pathway for treatment. artificial intelligence aids as a virtual assistant in robotic technology. fluoroscopic imaging guides to do heart catheterization that exposes operator, staff & patient to harmful radiation. to avoid this radiation, a selfdirected robot (cath-bot) is used to remotely supervise cardiac catheterization [7]. this robot develops a patient’s specific 3d anatomical model by hospital electronic record system that includes mri, ct, and ultrasound etc. temporal syncing is implemented through respiratory/ecg gating. catheter’s location is tracked via an electromagnetic tracking system with patient anatomy. all trial catheterizations were successfully completed and no difference in fluoroscopy emts was found in initial result. total procedural time was 3.9 secs lower than fluoroscopy. this project is still under improvisation which will also add catheter feedback positioning. 4 conclusions in rapid healthcare advancement, it is necessary to adopt new changes in the system and deliver better services to patients. ai has incredible potential to learn from past data or experience and make better decisions in the future. artificial intelligence is very useful in healthcare. ai, ml, and dl combining help in identifying diseases, allotting proper drugs to patients and reduces the risk of side effects of drugs. ai also helps in identifying real-time health information by continuously monitoring users’ behaviours and emotions. this paper revealed different applications of ai in healthcare, which are the attributes that ai uses to detect medical implications, factors affecting the efficiency of the ai system. ai with machine learning algorithms helpful in tuberculosis detection, brain tumour detection and not only for detection we can also apply ai in medical diagnostic and clinical care. many medical practitioners believe that technology has several advantages over traditional practices as it can analyse large datasets simultaneously, gives us an unsupervised discovery which discloses hidden patterns and enhances the speed by suggesting auto-generated clinical pathways. artificial intelligence is a tool which provides aid to medical practitioners in early diagnosis and help lower the mortality rate & medical inflation. the most challenging issue in artificial intelligence is to collect health data and to identify medical implications from available data due to less amount and complexity of data. ai community is on the way to develop such algorithms that are more adequate in pattern matching and identification and able to work on a massive quantity of unstructured health data. 5 references 1. adam. c. & uzialko (2019). artificial intelligence will change healthcare as we know it. business news daily. retrieved from https://www.businessnewsdaily.com/15096-artificial-intelligence-in-healthcare.html 2. cabestany, j., rodriguez-martín, d., pérez, c., & sama, a. (2018, june). artificial intelligence contribution to ehealth application. in 2018 25th international conference" mixed design of integrated circuits and system"(mixdes) (pp. 15-21). ieee. 3. cath-bot: first step toward an independent heart catheterization robot aimed [internet]. aimed. 2018 [cited 2 november 2018]. available from: http://ai-med.io/dt_team/cath-bot-first-step-towardan-independent-heartcatheterization-robot/ 4. gavrilov, d., melerzanov, a., schelkunov, n., & gorodilov, a. (2018). artificial intelligence image recognition in healthcare. in 2018 international conference on artificial intelligence applications and innovations (ic-aiai) (pp. 24-26). ieee. 5. gulshan, v., peng, l., coram, m., stumpe, m., wu, d. & narayanaswamy, a. development and validation of a deep learning algorithm for detection of diabetic retinopathy in retinal fundus photographs. jama. 2016; 316 (22): 2402 6. henry, k., hager, d., pronovost, p., saria, s. a targeted real-time early warning score (trewscore) for septic shock. science translational medicine. 2015;7(299):299ra122299ra122. 7. identifying clinical variation using machine intelligence: a pilot in colorectal surgery aimed [internet]. aimed. 2018 [cited 2 november 2018]. available from: http://ai-med.io/dt_team/identifying-clinicalvariationusing-machine-intelligence-a-pilot-incolorectal-surgery/ 8. khairnar, v. d., saroj, a., yadav, p., shete, s., & bhatt, n. (2019). primary healthcare using artificial intelligence. in international conference on innovative computing and communications (243-251). springer, singapore. 9. furmankiewicz, m., sołtysik-piorunkiewicz, a. & ziuziański, a. (2014). artificial intelligence systems for knowledge management in e-health: the study of intelligent software agents. research gate. retrieved from https://www.researchgate.net/profile/anna_soltysikhttps://www.businessnewsdaily.com/15096-artificial-intelligence-in-healthcare.html https://www.researchgate.net/profile/anna_soltysik-piorunkiewicz/publication/271014570_artificial_intelligence_systems_for_knowledge_management_in_e-health_the_study_of_intelligent_software_agents/links/54bd0ee30cf218da9390d759/artificial-intelligence-systems-for-knowledge-management-in-e-health-the-study-of-intelligent-software-agents.pdf islam (2021): international journal of engineering materials and manufacture, 6(4), 319-223 323 piorunkiewicz/publication/271014570_artificial_intelligence_systems_for_knowledge_management_in_ehealth_the_study_of_intelligent_software_agents/links/54bd0ee30cf218da9390d759/artificial-intelligencesystems-for-knowledge-management-in-e-health-the-study-of-intelligent-software-agents.pdf 10. machine-learning models for selection of drugcandidates for treatment of alzheimer's disease aimed. aimed. 2018 [2 november 2018]. retrieved from: http://ai-med.io/dt_team/machine-learning-modelsfor-selection-ofdrug-candidates-for-treatment-ofalzheimers-disease/ 11. neill, d. b. (2013). using artificial intelligence to improve hospital inpatient care. ieee intelligent systems, 28(2), 92-95. 12. nivetha, m. & nivethika, s. (2018). artificial intelligence in healthcare – a review. research gate. retrieved from https://www.researchgate.net/publication/329163470_artificial_intelligence_in_healtshcare-a_review 13. peter, j. & kent, n. (2012). patient behaviour and the benefits of artificial intelligence: the perils of ‘‘dangerous’’ literacy and illusory patient empowerment. elsevier. retrieved from https://www.researchgate.net/profile/peter_schulz2/publication/221250696_bad_literacy_the_internet_and_t he_limits_of_patient_empowerment/links/57f5422108ae91deaa5c77e9/bad-literacy-the-internet-and-thelimits-of-patient-empowerment.pdf 14. sun, t. q. & medaglia, r. (2019). mapping the challenges of artificial intelligence in the public sector: evidence from public healthcare. government information quarterly, 36(2), 368-383. 15. thomas, m. & maddox. (2019). questions for artificial intelligence in health care. viewpoint. retrieved from https://jamanetwork.com/journals/jama/article-abstract/2718456 16. tripathy, a. k., carvalho, r., pawaskar, k., yadav, s. & yadav, v. (2015, february). mobile based healthcare management using artificial intelligence. in 2015 international conference on technologies for sustainable development (ictsd) (pp. 1-6). ieee. 17. vincent, j. the clinical challenge of sepsis identification and monitoring. plos medicine. 2016;13(5): e1002022. 18. zillner, s. & neururer, s. big data in the health sector. new horizons for a data-driven economy. 2016:179194. 19. 2017 global medical trends survey report [internet]. willis towers watson. 2018 [cited 2 november 2018]. retrieved from: https://www.willistowerswatson.com/en/insights/2 017/05/2017-global-medical-trendssurvey-report https://www.researchgate.net/profile/anna_soltysik-piorunkiewicz/publication/271014570_artificial_intelligence_systems_for_knowledge_management_in_e-health_the_study_of_intelligent_software_agents/links/54bd0ee30cf218da9390d759/artificial-intelligence-systems-for-knowledge-management-in-e-health-the-study-of-intelligent-software-agents.pdf https://www.researchgate.net/profile/anna_soltysik-piorunkiewicz/publication/271014570_artificial_intelligence_systems_for_knowledge_management_in_e-health_the_study_of_intelligent_software_agents/links/54bd0ee30cf218da9390d759/artificial-intelligence-systems-for-knowledge-management-in-e-health-the-study-of-intelligent-software-agents.pdf https://www.researchgate.net/profile/anna_soltysik-piorunkiewicz/publication/271014570_artificial_intelligence_systems_for_knowledge_management_in_e-health_the_study_of_intelligent_software_agents/links/54bd0ee30cf218da9390d759/artificial-intelligence-systems-for-knowledge-management-in-e-health-the-study-of-intelligent-software-agents.pdf https://www.researchgate.net/publication/329163470_artificial_intelligence_in_healtshcare-a_review https://www.researchgate.net/profile/peter_schulz2/publication/221250696_bad_literacy_the_internet_and_the_limits_of_patient_empowerment/links/57f5422108ae91deaa5c77e9/bad-literacy-the-internet-and-the-limits-of-patient-empowerment.pdf https://www.researchgate.net/profile/peter_schulz2/publication/221250696_bad_literacy_the_internet_and_the_limits_of_patient_empowerment/links/57f5422108ae91deaa5c77e9/bad-literacy-the-internet-and-the-limits-of-patient-empowerment.pdf https://www.researchgate.net/profile/peter_schulz2/publication/221250696_bad_literacy_the_internet_and_the_limits_of_patient_empowerment/links/57f5422108ae91deaa5c77e9/bad-literacy-the-internet-and-the-limits-of-patient-empowerment.pdf https://jamanetwork.com/searchresults?author=thomas+m.+maddox&q=thomas+m.+maddox https://jamanetwork.com/journals/jama/article-abstract/2718456 international journal of engineering materials and manufacture (2018) 3(1) 1-8 http://dx.doi.org/1026776/ijemm.03.01.2018.01 k. junyi1 and n. hasan2 1department of chemical engineering, faculty of integrated technologies, universiti brunei darussalam, brunei 2petroleum and chemical engineering programme, faculty of engineering, universiti teknologi brunei, brunei e-mail: nurulhasan@asme.org reference: junyi, k. and hasan, n. (2018). a review of the factors that influence the condition of wax deposition in subsea pipelines. international journal of engineering materials and manufacture, 3(1), 1-8. review of the factors that influence the condition of wax deposition in subsea pipelines koh junyi, nurul hasan received: 10 october 2017 accepted: 20 february 2018 published: 30 march 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract when crude oil is transported via sub-sea pipeline, the temperature of the pipeline decreases at a deep depth which causes a difference in temperature with the crude oil inside. this causes the crude oil to dissipate its heat to the surrounding until thermal equilibrium is achieved. this is also known as the cloud point where wax begins to precipitate and solidifies at the walls of the pipeline which obstruct the flow of fluid. the main objective of this review is to quantify the factors that influence wax deposition such as temperature difference between the wall of the pipeline and the fluid flowing within, the flow rate of the fluid in the pipeline and residence time of the fluid in the pipeline. it is found the main factor that causes wax deposition in the pipeline is the difference in temperature between the petroleum pipeline and the fluid flowing within. most literature deduces that decreasing temperature difference results in lower wax content deposited on the wall of the pipeline. the wax content increases with rising flow rate. as for the residence time, the amount of deposited wax initially increases when residence time increases until it reaches a peak value and gradually decreases. flow-loop system and cold finger apparatus were used in literature investigations to determine the trends above. three new models are generated through a regression analysis based on the results from other authors. these new models form a relationship between temperature difference, flow rate, residence time and reynolds number with wax deposition. these models have high values of r-square and adjusted r-square which demonstrate the reliability of these models. keywords: wax deposition; influential factors for wax deposition; wax model development symbol/abbreviation wat wax appearance temperature, °c tp temperature of the walls of pipeline, °c tf temperature of the fluid in the pipeline, °c δt temperature difference between tp and tf, °c wd wax deposition, weight in percentage (%) fr flow rate, ml/min rs residence time, min rn reynolds number (based on dia) introduction the wax deposition has always been one of the most challenging and long-standing issues faced by petroleum industry when transporting crude oil via sub-sea pipelines. the temperature difference between the cold ambient temperature at the sub-sea level and the fluid is considered to be the main reason causing the formation of wax in the pipeline. for the wax to precipitate, the crude oil has to be at a temperature lower than wat. this temperature is similar to the freezing point where a liquid or fluid begins to solidify[1, 2]. this causes a shrinkage in flow area of the pipeline deposited wax becomes thicker. when exposed to cold surroundings, the cooling of crude oil in the pipelines causes droplets to group together and solidifies, giving a cloudy appearance. the oil droplets eventually lose their flowability, causes blockage in the pipeline and can result in pressure rise pipelines at an ocean floor experiences temperature of about 4°c and wax molecules begin to precipitate on the pipeline walls due to the cooling of crude a review of the factors that influence the condition of wax deposition in subsea pipelines 2 oil by the surrounding [3]. however, throughout the pipeline, the heat loss is inconsistent because there is a differential temperature gradient along the pipeline and this affects the rate of wax deposition [4]. to solve this critical issue, it is necessary to investigate and understand and quantify the factors that cause the problem for optimum crude productivity and flow assurance. the influencing factors that affect the behavior of wax deposition include the temperature gradient across the pipeline wall and the fluid within, flow rate and residence time. investigation of these factors involve the studies of two methods: the flow-loop system and cold finger apparatus. in flow–loop experiments, the fluids are circulated in a loop which it will pass through one or several measurements. cold finger, on the other hand, is an equipment that bears a resemblance to a finger hence the name. it consists of a cold finger (a cylindrical metal heat exchanger), which is kept at a lower temperature and immersed in a higher temperature of the crude oil. two separate water baths are used to control both temperatures (crude oil and cold finger) which can be varied for different thermal gradient [5, 6]. it is simply a technique where a temperature controlled rod is submerged in heated oil, and a significant quantity of wax must precipitate before visual determination of deposition is visible. therefore, this technique usually yields the lowest estimate of wat and does not make a direct representation of wax deposition in oilfield pipelines [7]. kelechukwu, al salim [8] conducted flow loop tests to investigate temperature difference, residence time and flow rate relations with wax deposition. the flow loop consists of several components: a stainless steel tank which acts as the reservoir, a twin pipe exchanger, a temperature controlled bath system and a hydrostatic pump whose purpose is to allow the mixture to move continuously. the reservoir tank has a radius of 180 mm and a height of 550 mm for holding 50 l reservoir. included in the system is a centrifugal pump which is utilized to allow continuous flowing of the coolant (water), a bypass valve and thermocouples. the temperature was ranged from 40-55°c, and the flow rate was varied from 100-500 ml/min. charlton et al. 2017 [9] attempted to validate model of hydrate deposition used in olga. molecular modeling is expensive, and an example is set of modeling methane hydrate by chen et al. [10]. as understood the blockage risk in oil pipelines by hydrate [11] will cause problems in the years to come. experiments on these phenomena are time-consuming and one of the bests approaches to perform solid-liquid-gas slug flow mechanistic model coupling hydrate dispersion formation with heat and mass transfer [12]. on the other hand, pore-scale formation of methane hydrate in the sand sediment using the phase-field model [13] is another way to capture the physics. mahto and kumar [14] investigated temperature difference using flow loop setup that included 5 l hot bath filled with crude oil sample, which was pumped into test-tube of the flow line surrounded by a cooling jacket which is continuously circulating cooling water over the test tube. their set-up is of smaller scale compared to experiments from kelechukwu, al salim [8]. deposition process initiates when circulating crude sample is cooled by the cooling jacket. the flow rate is determined by measuring the volume of crude oil collected in the measuring cylinder for a fixed time. after crude oil flows in the test tube for a different time interval (residence time), the flow is stopped, and diesel is circulated to wash the crude oil. the weight of the test tube is measured before, and after the experiment and the weight, difference indicates the amount of wax deposited during the flow. by studying and analyzing the results obtained from different authors, the objectives of interest is are enumerated in the followings: • to quantify the temperature difference effect between the walls of the pipeline (tp) and the fluid (tf) on wax deposition. • review the relationship between flow rate of the fluid in pipeline and wax deposition. • study the impact of wax deposition due to the residence time of the fluid in the pipeline. • to offer a general model of the factors influencing wax deposition. • what about the flow types? results and discussions according to research conducted by kelechukwu et al.[8], it is found that the deposited wax in pipeline decreases with increasing temperature difference. the results are shown in figure 1, figure 2, figure 3, and figure 4. all four figures measure the similar parameter but differ in residence time. it can be seen that at any residence time, wax deposition decreases at the nearly consistent rate when there is an increase in differential temperature across the pipeline wall and the fluid. for example in figure 1, at a low-temperature difference of 13°c, the wax deposit weight is at approximately 0.33% while this value decreases to as low as 0.1% when temperature difference increases to 28°c. flow rate is maintained at 100 ml/min. when the flow rate is varied, the trend of the graph remains mainly unchanged. a similar experiment was conducted by mahto and kumar [14], and they obtained similar trend regarding the relationship between wax deposition and temperature difference. their results are shown in figure 5, figure 6 and figure 7 where the water bath in their model was kept constant at 23°c to allow accurate measurement for wax deposition. wax deposition decreases with increasing differential temperature across the pipeline wall, and the fluid which is in complete understanding of previous work carried out by cole and jessen [15], bott and gudmundsson [16] and haq [2]. however, these results were in disagreement with reports by nazar, dabir [17] and jennings and weispfennig [5] stating that increasing temperature difference will result in increasing amount of deposited wax. impact on wax due to temperature difference conducted by nazar et al. (2001) is illustrated in figure 8 where the trend of the result is in contradiction to results from kelechukwu et al. (2010) and mahto and kumar (2013) junyi and hasan (2018): international journal of engineering materials and manufacture, 3(1), 1-8 3 figure 1 effect on wax deposit (weight percentage) due to temperature differential at 3 min (kelechukwu et al., 2010) figure 2 effect on wax deposit (weight percentage) due to temperature differential at 6min (kelechukwu et al., 2010) figure 3 effect on wax deposit (weight percentage) due to temperature differential at 9 min (kelechukwu et al., 2010) figure 4 effect on wax deposit (weight percentage) due to temperature differential at 12 min (kelechukwu et al., 2010) jennings and weispfennig [5] experimented using coldfinger system and stated that their results could provide some insight into wax deposition process even though not as accurate as flow loop tests to represent wax deposition in real life subsea pipelines. creek, lund [18] conducted a test by keeping a constant temperature difference between the pipe walls and flowing oil of 8.3°c while decreasing the inlet temperature of the oil to as much as 25°c below the wat. these tests were performed under laminar conditions. it was found that no deposition was observed when there was no temperature difference. kelechukwu, al salim [8] investigated the impact on deposited wax at the pipeline wall due to flow rate on wax as shown in figure 9, figure 10, figure 11 and figure 12. at any temperature, it is observed that the deposited wax decreases with increasing flow rate. for instance, in figure 8, the deposited wax percentage is at approximately 0.33 % at 100ml/min flow rate. as flow rate increases, the deposited wax gradually decreases until it attains 0.2 % at 500 ml/min. this result can be explained in terms of viscous drag which increases due to increasing velocity of the fluid. viscous drag acts as a resistance force to the flow of the fluid hence will increase with increasing velocity according to the fluid dynamics. this force helps to cause the wax deposition layer to become thinner or even remove the deposited wax completely provided that the shear stress of the deposited wax is exceeded. as we can see from figure 5, figure 6 and figure 7, mahto and kumar [14] obtained similar trend when experimenting on the effect of flow rate. at constant residence time and temperature differential, the wax deposit weight percentage decreased with increasing flow rate. research on the impact of flow rate conducted by creek, lund [18] found that deposited wax increases in thickness when flow rate increases. this result applies for a review of the factors that influence the condition of wax deposition in subsea pipelines 4 both laminar and turbulent flow. brown, niesen [19] suggest that deposited wax is harder when it is formed at the higher shear rate. these results are in agreement with results by lund [20] and venkatesan [21]. since the fluid flows in the pipeline is of turbulent flow, it contributes greatly to the decrease in deposited wax with increasing flow rate. the increase in wax deposited however is due to a deposition process called diffusion in the laminar region. the decrease in a wax deposition with increasing flow rate while diffusion was responsible for the increase in a deposition with increasing flow rate in the laminar region [22]. research also shows that when flow velocity exceeds 1.5 ms-1, wax deposition becomes very weak. figure 5 effect on wax deposit (weight percentage) due to temperature differential at 60 min (mahto and kumar, 2013) figure 6 effect on wax deposit (weight percentage) due to temperature differential at 180 min (mahto and kumar, 2013) figure 7 effect on wax deposit (weight percentage) due to temperature differential at 300 min (mahto and kumar, 2013) figure 8 effect on wax deposit due to temperature differential (nazar et al., 2001) experimental results from kelechukwu, al salim [8] on residence time are illustrated in figure 13, figure 14, figure 15 and figure 16, it was found that deposition of wax increases at a constant rate with increasing residence time but only up to certain point, where the deposition of wax increases at a slower rate. lastly, the wax deposition decreases with increasing residence time. in figure 13, it can be seen that wax deposit weight percentage increases linearly from 0.32 % to 0.5 % when the time is increased from 3 to 6 min at constant 13 °c. then, the wax deposition slows down greatly and only increases by 0.1 % for 9 min. then, the deposited wax gradually decreases until approximately 0.4 % at 18 min. these trends were found at other experimented flow rates of 200 ml/min, 300 ml/min, 400 ml/min junyi and hasan (2018): international journal of engineering materials and manufacture, 3(1), 1-8 5 and 500 ml/min. the same author stated that residence time allows a higher rate of heat loss resulting in lower fluid temperature. this, in turn, causes the wax to precipitate and deposit at the wall of the pipeline. since this experiment was conducted in a close-loop system, there is no continuous supply of fresh sample (fluid) therefore causing a depletion in a wax deposition at longer residence time. it was deduced that at a higher value of residence time, the amount of wax deposit drops because the layers of deposited wax provide thermal insulation [23]. to further strengthen this obtained result, mahto and kumar [14] also obtained similar trend even though their experiments are conducted at a higher time value. their result is shown in figure 17. these findings are in agreement with researchers by cole and jessen [15], bott and gudmundsson [16], haq [2] and towler and rebbapragada [24]. however, it is important to note that this scenario cannot be applied in practical oilfield pipeline because the reservoir continuously supplies fresh crude oil. this result in shorter residence time for the fluid hence increased in wax deposition compared to experiments. gooya, gooya [25] conducted an experiment to investigate the relationship between δt, flow rate with wax deposition. the main difference his experimental setup differs from the other authors is gooya et al. (2013) involves pipe length as the additional variable compared to the other authors. the results are shown in figure 18 and figure 19. it is found that wax thickness is at maximum during the first 200 m in the pipeline and a higher δt is recorded when the flow rate is lower during the first 3500m. for higher flow rate, δt is higher. this is due to deposition mechanisms which result in decreasing the stripping rate and concentration gradient. this causes a decrease δt at pipe distance greater than 3500 m. figure 9 effect of flow rate on deposited wax percentage at 3min (kelechukwu et al., 2010) figure 10 effect of flow rate on deposited wax percentage at 6 min (kelechukwu et al., 2010) figure 11 effect of flow rate on deposited wax percentage at 9 min (kelechukwu et al., 2010) figure 12 effect of flow rate on deposited wax percentage at 12 min (kelechukwu et al., 2010) a review of the factors that influence the condition of wax deposition in subsea pipelines 6 figure 13 effect on wax deposition due to residence time at 100 ml/min (kelechukwu et al., 2010) figure 14 effect on wax deposition due to residence time at 200 ml/min (kelechukwu et al., 2010) figure 15 effect on wax deposition due to residence time at 300 ml/min (kelechukwu et al., 2010) figure 16 effect on wax deposition due to residence time at 400 ml/min (kelechukwu et al., 2010) figure 17 effect on wax deposition due to residence time (mahto and kumar, 2013) figure 18 effect of pipe length on wax thickness (gooya et al., 1013) junyi and hasan (2018): international journal of engineering materials and manufacture, 3(1), 1-8 7 using their results, regression analysis is attempted here to generate model relating all the variables (δt, flow rate and residence time) with wax deposition. the results are shown in figure 20, figure 21, figure 22 and new models have been developed as shown in the equation (1), equation (2) and equation (3) for wax deposit results based on kelechukwu, al salim [8], mahto and kumar [14] and gooya, gooya [25] respectively. for this model, the values of r-square and adjusted r-square are 0.867 and 0.862 respectively. the standard error is just a low 4.6%. the high value of adjusted r square and low standard error indicates that this model is a good fit. the coefficients for intercept, δt, flow rate and residence time are 0.46503, -0.01103, -0.00042 and 0.00724 respectively. for this model developed, the r-square and adjusted r-square values are 0.968 and 0.963 respectively. these extremely high values back the validity of this model. the standard error is just a lowly 3.8%. the coefficients for intercept, δt, flow rate and residence time are 2.34324, -0.02969, -0.00062 and -0.00128 respectively. this developed model had high values of r-square and adjusted r-square which records 0.9737 and 0.9730 respectively. the standard error is at 0.07% which can be neglected because of its extremely low value. from all these values, it can be concluded that this model is the most fitting among all three models. this model records 0.00592 for intercept, -4.1 x 10-6 for δt, 2.15 x 10-6 for flow rate, -120 x 10-6 for residence time and lastly -0.00306 for reynolds number. 𝑊𝑊𝑊𝑊 = 0.46503 − 0.01104∆𝑇𝑇 − 0.000042𝐹𝐹𝐹𝐹 + 0.00724𝐹𝐹𝑅𝑅 (1) 𝑊𝑊𝑊𝑊 = 2.34324 − 0.02969∆𝑇𝑇 − 0.00062𝐹𝐹𝐹𝐹 + 0.00128𝐹𝐹𝑅𝑅 (2) 𝑊𝑊𝑊𝑊 = 5.922 − 0.0041∆𝑇𝑇 − 0.00215𝐹𝐹𝐹𝐹 + 0.00001𝐹𝐹𝑅𝑅 − 3.06𝐹𝐹𝑅𝑅 (3) figure 19 relationship between δt and pipe length (gooya et al., 2013) figure 20 comparison between real result and developed model for works by kelechukwu et al. (2010) figure 21 comparison between real result and developed model for works by mahto and kumar (2013) figure 22 comparison between real result and developed model for works by gooya et al. (2013) a review of the factors that influence the condition of wax deposition in subsea pipelines 8 conclusions literature review on the impacts of the temperature differential across the pipeline wall and the fluid within, flow rate and residence time have on wax deposition is conducted in this paper. flow-loop system and cold finger apparatus are used to simulate the paraffin wax deposition at wall pipeline which forms one of the core issues in the petroleum industry. the amount of wax deposited is plotted for every experiment conducted by different authors so that they can be easily analysed for every factor. it is concluded that temperature difference between the wall of pipeline and the fluid within represents the most important factor for wax deposition. there is still uncertainty whether a huge temperature differential leads to less wax deposition due to different results produced by different work. however, it is absolute that the amount of deposited wax decreases with the increased flow when conducted with both experiment setups. also, the deposited wax increases with residence time but attain opposite result when the certain maximum time value is achieved. regression analysis is applied to generate models relating all three influencing factors with wax deposition. r-square and adjusted r-square values for all models exceed 85% which backs the validity of the models. in total, three new models are generated. despite that, further work is still needed in this scope to obtain more concrete results so that the more accurate influential rate of these factors are determined compared to real life flowing in subsea pipelines. references 1. reistle jr c. methods of dealing with paraffin troubles encountered in producing crude oil. bureau of mines, washington, usa, 1928. 2. haq ma. deposition of paraffin wax from its solution with hydrocarbons (usms 10541). soc. petro eng 1978. 3. huang z, lee hs, senra m, scott fogler h. a fundamental model of wax deposition in subsea oil pipelines. aiche journal 2011;57:2955-64. 4. singh p, venkatesan r, fogler hs, nagarajan n. formation and aging of incipient thin film wax‐oil gels. aiche j 2000;46:1059-74. 5. jennings dw, weispfennig k. effects of shear and temperature on wax deposition: coldfinger investigation with a gulf of mexico crude oil. energy & fuels 2005;19:1376-86. 6. paso kg, fogler hs. bulk stabilization in wax deposition systems. energy & fuels 2004;18:1005-13. 7. lira-gc, hammami a. wax precipitation from petroleum fluids: a review. dev petro science 2000;40:557-608. 8. kelechukwu em, al salim hss, yassin aam. influencing factors governing paraffin wax deposition during crude production. int j phy sci 2010;5:2351-62. 9. charlton tb, di lorenzo m, zerpa le, koh ca, johns ml, may ef, aman zm. simulating hydrate growth and transport behavior in gas-dominant flow. energy & fuels 2017. 10. ji h, chen d, zhao c, wu g. molecular dynamics simulation of methane hydrate formation and dissociation in the clay pores with fatty acids. j phy chem c 2018;122:1318-25. 11. norris bwe, johns ml, may ef, aman zm. assessing hydrate blockage risk in oil pipelines: deploying a new transient simulation capability. int conf multiphase prod technol; cannes, france. 2017. 12. bassani cl, barbuto faa, sum ak, morales rem. a three-phase solid-liquid-gas slug flow mechanistic model coupling hydrate dispersion formation with heat and mass transfer. chem eng. sci 2018;178:222-37. 13. fukumoto a, kamada k, sato t, oyama h, torii h, kiyono f, nagao j, temma n, narita h. numerical simulation of pore-scale formation of methane hydrate in the sand sediment using the phase-field model. j natural gas sci eng 2018;50:269-81. 14. mahto v, kumar a. effect of several parameters on wax deposition in the flow line due to indian waxy crude oil. int j appl eng res dev 2013;3:1-10. 15. cole r, jessen f. paraffin deposition. oil gas j 1960;58:87-91. 16. bott t, gudmundsson j. deposition of paraffin wax from kerosene in cooled heat exchanger tubes. canadian j chem eng 1977;55:381-5. 17. nazar a, dabir b, islam m, editors. measurement and modeling of wax deposition in crude oil pipelines. spe latin american and caribbean petroleum engineering conference; 2001: society of petroleum engineers. 18. creek j, lund hj, brill jp, volk m. wax deposition in single phase flow. fluid phase equilibria 1999;158:801-11. 19. brown t, niesen v, erickson d, editors. measurement and prediction of the kinetics of paraffin deposition. spe annual tech conf and exhib; 1993: soc petro engr. 20. lund h. investigation of paraffin deposition during single phase flow in pipelines. msc. thesis, uni tulsa, 1998. 21. venkatesan r. the deposition and rheology of organic gels: university of michigan.; 2004. 22. agrawal k, khan h, surianarayanan m, joshi g. wax deposition of bombay high crude oil under flowing conditions. fuel 1990;69:794-6. 23. hoteit h, banki r, firoozabadi a. wax deposition and aging in flowlines from irreversible thermodynamics. energy & fuels 2008;22:2693-706. 24. towler bf, rebbapragada s. mitigation of paraffin wax deposition in cretaceous crude oils of wyoming. j petro sci eng 2004;45:11-9. 25. gooya r, gooya m, dabir b. effect of flow and physical parameters on the wax deposition of middle east crude oil under subsea condition: heat transfer viewpoint. heat and mass transfer 2013;49:1205-16. abstract introduction references international journal of engineering materials and manufacture (2019) 4(4) 170-177 https://doi.org/10.26776/ijemm.04.04.2019.05 abutu, j. 1 , lawal, s. a. 1 , ndaliman, m. b. 1 , lafia-araga, r. a. 2 , abdulrahman a.s. 3 1 department of mechanical engineering 2 department of chemistry 3 department of material & metallurgical engineering federal university of technology, minna p.m.b, 65 minna, niger state, nigeria e-mail: mbndaliman@futminna.edu.ng reference: abutu, j., lawal, s. a., ndaliman, m. b., lafia-araga, r. a. and abdulrahman a. s. (2019). effects of particle size distribution on the properties of natural-based composite. international journal of engineering materials and manufacture, 4(4), 170-177. effects of particle size distribution on the properties of natural-based composite abutu joseph, lawal sunday albert, ndaliman mohammed baba, lafia-araga ruth anayimi and abdulrahman asipita salawu received: 03 october 2019 accepted: 09 november 2019 published: 15 december 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract in this study, locally sourced natural materials (coconut shells and seashells) were used separately to produce composites. the powders were sieved with sieve size of 10 µm and characterized using a particle size analyser (dls) in order to ascertain their particle size distribution. also, the effects of particle size distribution on the performance of sourced coconut shells and seashells-based composite was investigated. about 52% of the characterized powder was afterward used along with other ingredients (35% binder, 8% alumina and 5% graphite) to produced composites using moulding pressure (14 mpa), moulding temperature (160 ºc), curing time (12 min) and heat treatment time (1 hr). the performance of the composites was thereafter evaluated using standard testing procedures. the results of particle size analysis indicated that the seashell powder (0.27) possesses lower distribution width (pdi) compared to the coconut shell powder (0.342) while the coconut shell (542.3 nm) showed lower z-average diameter compared to the seashell powder (1096 nm) with some little traces of nanoparticles (<10 µm). also, the experimental results obtained from composite characterization indicated that the coconut shell-based samples exhibited better performance in terms of its mechanical and tribological properties compared to the seashell-based samples. keywords: coconut shells, seashells, particle size analysis, composite, dynamic light scattering 1 introduction it was reported that particles of different sizes in a given powder have different flow and packing properties that tend to alter the volume of a powder (chamoli et al., 2008). subhash et al. (2017). coconut shell powder (fig. 1b) is obtained from agricultural wastes and used in the preparation of various attractive articles (antiques) and also applied in the production of activated charcoal as well as reinforcement material in the production of composites. in addition, powder of natural materials such as seashell (exoskeletons of mollusks) are mainly composed of calcium carbonate, intermediate layer (calcite) and the outer layer of horny substance known as conchiolin (schaeffer, 2014). salmah et al. (2013) reported that coconut shells are lignocellulosic filler which exhibits excellent properties compared to mineral fillers (kaolin, calcium carbonate, mica and talc). some of the outstanding properties reported by the author include minimal health hazard, high-specific strength-to-weight ratio, low cost, biodegradability, environmental friendly and renewability. also, matthew (2012) reported that moisture desorption of coconut shells takes place between 25 and 150 °c and at 150 °c, degradation of sclerenchyma cells, which are responsible for holding water in the shell occurs. further heating of the shells between 190 °c to 260 °c may result to the degradation of hemicellulose present in the shell and at 240 °c to 350 °c, degradation of cellulose take place. the final stage of thermal degradation involves the breakdown of lignin which occurs between 280 °c and 500 °c (matthew, 2012). therefore, in this study, powders were prepared from two locally sourced natural raw materials (coconut shell and seashell) and characterized using particle size analyser (zetasizer nano) with the aim of comparing the particle size distribution of the powder particles when sieved using the same sieve size and analysed by the similar equipment and testing conditions. abutu et al. (2019): international journal of engineering materials and manufacture, 4(4), 170-177 171 2 literature review pei-jia et al. (2018) suggested that, in order to select the appropriate dispersing and solvent agents, it is important to have sufficient knowledge of the basic chemical properties when preparing a well-dispersed powder suspension for dls characterization. as a result, in the work of tanmaya (2011), the elemental composition (proximate) and content distribution (ultimate) of coconut shell powder were investigated using chnso elemental analyser (variael cube, germany). the results of proximate and ultimate analysis of the coconut shell powder are shown in table 1. based on the findings presented in table 1, the author concluded that, coconut shell has good amount volatile content to be used as a material for composite production. also, norazlina et al. (2015) revealed that seashell primarily consist of calcium carbonate (caco3), been naturally above 80% caco3 by weight with only about 2 % protein content and no complex extraction process is needed to use it for composite production. seashell exhibit significant combinations of low weight, toughness, stiffness and strength which are in some cases unrivalled by mineral fillers (vignesh et al. 2015). table 2 shows the chemical composition of a commercial calcium carbonate and calcium carbonate obtained from seashell as reported by michele et al. (2012). the seashell powder used in the study was utilised as filler by the authors to produce a composite using polyester binder. the test results indicate that the commercial caco3 based composite possesses an impact and tensile strength of 918 mpa and 3.2 kjm –2 respectively while seashell-based composite exhibit an impact and tensile strength of 904 mpa and 3.4 kjm –2 correspondingly. the authors concluded that seashell can be used in place of commercial caco3 to produce composites since commercial caco3 and seashell (mussel or oyster shells) produces similar results regardless of their variation in distribution of particle size or particle sizes. nia et al. (2012) in their study, demonstrated six submicron particle sizing techniques which include dynamic light scattering (dls), scanning mobility particle sizing, particle tracking analysis (pta), tunable resistive pulse sensor (trps), transmission electron microscopy (tem) and differential centrifugal sedimentation (dcs). one of the commonly used technique, dynamic light scattering (dls) measures the particle size of sieved powder by determining the average hydrodynamic diameter of a particle suspension through measurement of the changes produced by particles scattering light in a speckle pattern moving under brownian motion (will et al., 2013). pei-jia et al. (2018) also revealed that dls is a relatively affordable and fast tool which can be used for determining the size distribution, polydispersity index (pdi) and mean size of a nanoparticle sample. a device known as zetasizer (the world’s most widely used systems for nanoparticle) which incorporates two techniques in a distinct condensed unit, and has a range of accessories and options to optimise as well as simplify the size of different sample type can be used in this technique (dls). hermann (2009) also revealed that there is need to characterize sourced powdered particles. some of the reasons highlighted by the author include to: i. study the behaviour in a specific environment ii. study the characteristics of different powdered material for specific applications iii. achieve optimization during production of the composite. iv. study the interaction of the sourced material with biological systems. therefore, in this study, the effects of particle size distribution on the performance of locally sourced coconut shells and seashells-based composite was investigated by characterizing the powders and developed composite using particle size analyser (zetasizer nano) and standard testing methods respectively. table 1: proximate and ultimate analysis of coconut shell powder source: tanmaya (2011) content proximate analysis (% w/w) elemental composition (%) moisture content 10.1 oxygen 22.61 fixed carbon 11.2 hydrogen 4.89 ash content 14.2 sulphur 3.50 volatile matter 64.6 nitrogen 4.77 carbon 64.23 table 2: chemical composition of seashell and commercial caco3 source: michele et al. (2012). oxides caco3 from seashell (%) commercial caco3 (%) cao 95.7 99.1 so3 0.7 sio2 0.9 k2o 0.5 0.4 fe2o3 0.7 al2o3 0.4 mgo 0.6 sro 0.4 effects of particle size distribution on the properties of natural-based composite 172 3 research materials the seashell and coconut shell used in this study as shown in figure 1 and figure 2 were sourced locally. seashells (the shells of sea snails) were collected from a local seafood vendor situated in lagos bar beach, lagos nigeria, while coconut shells were obtained from a coconut trader in a sabon tasha market in kaduna nigeria. sieving of the ground seashell and coconut shell was done using sieve of 10 µm mesh size. 3.1 particle size analysis particle size analysis of the sieved powder was conducted using a particle size analyser [zetasizer (nano series), model: zen1600, s/n: mal1084260, malvern, uk] connected to a computer system (figure 3) situated at the centre for genetic engineering and bio-technology (step b) in federal university of technology, minna, nigeria. 3.2 production of composites materials used in the production of the seashell and coconut-shell reinforced composites are shown in table 3. also, production of composites was carried at the federal college of chemical and leather technology (fcclt), samaru, zaria (polymer workshop) using a compression moulding machine (model: 0577-86365889, wenzhou zhiguang shoe-making machine co. ltd). (a) (b) figure 1: (a) crushed coconut shells and (b) sieved coconut shell powder (a) (b) figure 2: (a) seashells and (b) sieved seashells powder figure 3: particle size analyser abutu et al. (2019): international journal of engineering materials and manufacture, 4(4), 170-177 173 4 research methodology 4.1 powder preparation the method in preparation of the coconut shell and seashell powder involve washing with soap as well as detergent, cleaning using dried cloth, drying in an hot air oven operating at a temperature of 150 o c followed by crushing using pestle and mortar as well as grinding with grinding machine and finally sieving using a sieve size of 10 µm. 4.2 particle size analysis the zetasizer system used in this study measured the particle size of the seashell and coconut shell powder. the system used methanol of 0.5476 cp viscosity as dispersant while the temperature and duration of measurement were set at 25 o c and 60 minutes respectively. the testing procedure include, preparing the test samples in accordance with sample preparation guidelines outline by the manufacturer and there after loosening the lid of the zetasizer and turning it on. this is followed by choosing the measurement type and cells appropriate for the sample and filling the cells with the prepared test sample after the laser stabilises. thereafter, measurement of standard operating procedure (sop) was made to ensure that measurements carried out on the samples were done in a consistent manner. finally, the cell filled with the prepared samples is inserted into the instrument and measurement is carried out at stabilised temperature. the results displayed on the screen is saved and afterward opened as a measurement file. the result obtained were presented in four section, this include the sample details (record number, sample name, dispersant name, the standard operating procedure (sop) used, measurement date and time as well as the measurement file name), system details (cell type, temperature, run duration and attenuator), results (zeta potential, standard deviation, peak mean and conductivity) and graph. 4.3 composite production production of samples was carried out using standard procedure outlined by chemiplastica (2010) and abutu et al. (2018) using a compression moulding machine. as presented in table 4, the composition of the coconut shell and seashell-reinforced samples as well as process parameters (moulding pressure, moulding temperature, curing time and heat treatment time) remained constant throughout the production process. in order to improve the properties of the composites, samples produced were subjected to further heat treatment using a hot air oven operating at a temperature of 150 ֩c. 4.4 characterization of composites in order to study its performance of the developed composites, samples characterized using standard testing procedures shown in table 5. table 3: materials used for production of composites function coconut shell-based composite seashell-based composite reinforcement coconut shell powder seashell powder binder epoxy resin epoxy resin abrasives alumina alumina friction modifier graphite graphite table 4: percentage composition and process parameters % compositon process parameters reinforcement 52 moulding pressure (mp) 14 mpa binder 35 moulding temperature (mt) 160 ºc abrasives 8 curing time (ct) 12 min friction modifier 5 heat treatment time (htt) 1 hr table 5: testing equipment and methods properties equipment used testing method/standard ultimate tensile strength (mpa) universal testing machine astm d638 type iv mode bending strength (mpa) universal testing machine en iso 178:2003 hardness (shore d scale) durometer astm d2240 type d scale compressive strength (mpa) universal testing machine astm d695 impact strength (j/mm) impact tester (charpy mode) astm e23 coefficient of friction inclined plance (15 ֩) s.o.n. act, 2015 wear rate (mg/m) antopaar tribometer astm g99 effects of particle size distribution on the properties of natural-based composite 174 5 results and discussions 5.1 polydispersity index and z-average the summary of polydispersity index (pdi) and z-average diameters in nanometres values for each sample of coconut shell (c) and seashell powder (s) are presented in table 6. the pdi values presented in table 5 represent an estimate of the width of distribution while z-average diameter represents the mean hydrodynamic diameter. these two parameters were automatically calculated on the zetasizer system in accordance to the international standard on dynamic light scattering, iso13321 (1996). from the result presented in table 3, it can be observed that the seashell particles possesses lower distribution width (0.27) compared to the coconut shell powder (0.342) when sieved using similar sieve size (10 µm) while the coconut shell (542.3) showed lower z-average diameter compared to that of seashell powder (1096). 5.2 particle size distribution the results of particle size distribution by volume as well as intensity of the coconut shell and seashell powder are shown in figure 4–7. 5.2.1 coconut shell powder the intensity distribution of coconut shell particles shown in figure 4 describes how much light was scattered by the particles in the different size bins while the volume distribution of the particle sizes presented in figure 5 represent the total volume of particles in the different size bins. as shown in figure 4, it can be observed that some of the particles appeared to be nano (≤100 nm) and the intensity size distribution from particles in water shows two peak regions of 290 nm (0.29 µm) and 4725 nm (4.725 µm) with standard deviations of 137.8 nm (0.1378 µm) and 803.6 nm (0.8036 µm) by intensity respectively. similarly, figure 5 showed that the shape of the distribution seems to be different and appears to be biased towards smaller sizes with fewer of the particles appearing to be nano (≤100 nm). it can also be observed that the volume size distribution of the particles shows two peak regions of 322.4 nm (0.3224 µm) and 5041 nm (5.041 µm) with standard deviations of 177.2 nm (0.1772 µm) and 874.7 nm (0.8747 µm) by volume respectively. all the particle sizes of the coconut shell powder were found to be below 10000 nm (10 µm) with little trace of nano particles. table 6: polydispersity index and z-average of samples sample pdi z-average diameter (nm) c 0.342 542.3 s 0.270 1096 figure 4: particle size distribution by percentage intensity abutu et al. (2019): international journal of engineering materials and manufacture, 4(4), 170-177 175 5.2.2 seashell powder the intensity distribution of the seashell particle describes how much light is scattered by the particles at different size bins while the volume distribution of the seashell particle sizes represent the total volume of particles in the different size bins. from figure 6, it can be observed that the intensity size distribution from seashell particles in water showed a single peak region of 1603 nm (0.1603 µm) with a standard deviation of 1079 nm (0.1079 µm) by intensity. all the particle sizes were found to be below 10000 nm (10 µm) with absence of nanoparticles. also, in figure 7, the shape of the distribution seems to be different and appears to favour both smaller and larger sizes. it can also be observed that the volume size distribution of the particles showed a peak region of 1443 nm (0.1443 µm) with a standard deviation of 840.8 nm (0.8408 µm) by volume. compared to the coconut shell powder, all the particle sizes of the seashell powder were found to be below 10000 nm (10 µm) but with no traces of nanoparticles. 5.2.3 characterization of composite samples the experimental results obtained from the characterization of the coconut shell-based (figure 8a) and seashell-based (figure 8b) composite are shown in table 7. from the experimental results presented in table 7, it can be observed that the coconut shell-based sample showed better performance (mechanical and tribological properties) with wear rate of 0.0315 mg/m and friction coefficient of 0.614 compared to the seashell-based composite having wear rate and friction coefficient of 0.0725 mg/m and 0.525 respectively. this improved performance of coconut shell-based composite may be attributed to lower z-average (mean hydrodynamic diameter) of coconut shell powder, which was 542.3 nm versus 1096 nm obtained for seashell powder. these results are in agreement with the earlier findings. figure 5: particle size distribution by percentage volume figure 6: particle size distribution by percentage intensity effects of particle size distribution on the properties of natural-based composite 176 yawas et al. (2016) reported that reduced particle size (z-average) of powder particles in a composite lead to an increased surface area which in turn result in an increase in good interfacial bonding ability between the powder particles and resin. vignesh et al. (2018) also investigated the effects of particles size distribution on the properties of natural-based composite and revealed that, composites composed of smaller particle sizes give better performance as it is capable of avoiding the occurrence of voids which can pose negative effects on the properties of composites. figure 7: particle size distribution by percentage volume (a) (b) figure 8: heat treated samples (a) coconut shell-based composite and (b) seashell-based composite table 7: experimental results properties coconut shell-based composite seashell-based composite ultimate tensile strength (mpa) 7.38 2.55 bending strength (mpa) 8.34 7.25 hardness (shore d scale) 63.31 55.81 compressive strength (mpa) 3.817 2.975 impact strength (j/mm) 0.032 0.097 wear rate (mg/m) 0.0315 0.0725 coefficient of friction 0.614 0.525 abutu et al. (2019): international journal of engineering materials and manufacture, 4(4), 170-177 177 6 conclusions and recommendations this study presents the effects of particles size distribution on the properties of coconut shell and seashell-based composites. powder samples of the two natural materials were subjected to particle size analysis using an analyzer in order to study their size distribution and thereafter used to separately produce composites of two distinct based materials (coconut shell and seashell powder) with the aim of comparing the effects of the based materials. based on the experimental results obtained, the following conclusions can be drawn: 1. the coconut shell and seashell powder sieved with the same mesh size (10 µm) possesses different z-average diameter (542.3 and 1096 nm) with the coconut shell powder containing some traces of nanoparticles (≤100 nm). 2. also, the volume size distribution of the sieved coconut shell particles shows two peak regions (322.4 nm and 5041 nm) while the seashell particles showed a single peak region (1603 nm) with no trace of nanoparticles. 3. finally, samples produced using coconut shell powder as based material exhibited better mechanical and tribological properties compared to the seashell-based samples. therefore, compared to seashell, coconut shell powder sieved with 10 µm mesh size is the most recommended reinforcement material for use in composite production. references abutu j., lawal s.a., ndaliman m.b., lafia-araga r.a., adedipe o. & choudhury i. a. (2019). production and characterization of brake pad developed from coconut shell reinforcement material using central composite design. sn applied sciences. 1:18. chamoli; k., jain, d. & pathak, k (2008). ind j pharm ed res, 42 (4), 168-171. chemiplastica (2010), thermoset processing manual compression molding, retrieved from, http://www.chemiplastica.com/pdf/compression-molding-guidelines.pdf. hermann, s. (2009). overview of the methods and techniques of measurement of nanoparticles, nanotrust – possible health effects of manufactured nanomaterials, vienna, 24 september 2009. available at http://www.jrc.ec.europa.eu. matthew, l.k. (2012). thermal degradation as a function of time and temperature in a coconut shell powder polypropylene composite, master’s thesis, baylor university, waco, texas. michele, r.r., hamestera, p.s.b. & daniela, b. (2012). characterization of calcium carbonate obtained from oyster and mussel shells and incorporation in polypropylene. journal of materials research, 15(2), 204-208. nia, c. b., caterina, m., jordan, t., molly, m.s. & alexander, g.s. (2012), emerging techniques for submicrometer particle sizing applied to stöber silica, 28, 10860–10872. norazlina, h., fahmi, a.r.m., & hafizuddin, w.m. (2015). caco3 from seashells as a reinforcing filler for natural rubber, journal of mechanical engineering and sciences, 8, 1481-1488. pei-jia, l., wei-en, f., shou-chieh, h., chun-yen, l., mei-lin, h., yu-pen, c., hwei-fang, c. (2018). methodology for sample preparation and size measurement of commercial zno nanoparticles, journal of food and drug analysis, 26, 628-636. subhash, p. c. b., nagaraju, r., saritha, d., deepthy, k & supraja, b. (2017). analysis of particle size distribution of some powders and dosage forms by skewness and kurtosis, journal of chemical and pharmaceutical research, 9(6), 113-119. salmah, h., koay, s.c. & hakimah, o. (2013). surface modification of coconut shell powder filled polylactic acid biocomposites, journal of thermoplastic composite material,26 (6), 809-819. schaeffer, h. (2014), seashell, retrieved from www.brittanica.com/ebchecked/topic/5 310 21/seashell. tanmaya k.r. (2011). pyrolysis of coconut shell, m.tech thesis submitted to; department of chemical engineering, national institute of technology, rourkela, 31-32. vignesh, k., anbazhagan, k., ashokkumar, e., manikandan, r. & jayanth, a. (2015). experimental analysis of mechanical properties of sea shell particlespolymer matrix composite, international journal of mechanical and industrial technology, 3(1), 13-21. will, a., darby, k., victoria, a.c., åsa, k.j. & matt, t. (2013). a comparative study of submicron particle sizing platforms: accuracy, precision and resolution analysis of polydisperse particle size distributions, 405, 322–330. yawas, d.s., aku, s.y. & amaren, s.g. (2016). morphology and properties of periwinkle shell asbestos-free brake pad. journal of king saud universityengineering sciences, 28,103-109. http://www.chemiplastica.com/pdf/compression-molding-guidelines.pdf http://www.jrc.ec.europa.eu/ http://www.brittanica.com/ebchecked/topic/5310 http://dx.doi.org/10.1016/j.jksues.2013.11.002 international journal of engineering materials and manufacture (2021) 6(4) 324-331 https://doi.org/10.26776/ijemm.06.04.2021.09 uddin, m. s. and abedin, m. z. department of mechanical engineering dhaka university of engineering and technology gazipur-1707, bangladesh. e-mail: abedin.mzoynal@duet.ac.bd reference: uddin and abedin (2021). segregation of plastic waste from solid wastes: bangladesh perspective. international journal of engineering materials and manufacture, 6(4), 324-331. segregation of plastic waste from solid waste stream: bangladesh perspective md sanuwar uddin and mohammad zoynal abedin received: 16 april 2021 accepted: 22 april 2021 published: 01 october 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract solid waste is an inevitable by-product of human beings, animals and also of industrial-commercial activities. obviously solid waste creates a greater problem to the environment, if it is not properly managed. bangladesh being a heavily populated country needs to pay adequate attention to waste management. waste generation in bangladesh is increasing because of rapid urbanization and economic development of the country. at present, total solid waste generation in bangladesh is around 27000 tons/day and in the four important city corporations is about 13,332 tons. particularly in dhaka city, it is around 7500 tons/day. this amount is likely to reach about 47000 tons per day in entire bangladesh and 15000 tons per day for dhaka city alone by 2030. at present, landfilling is the only method for disposal of heterogeneous waste stream and there are three landfills in dhaka city. most of these landfill sites are in open dumps polluting land, water and air. development of any new landfill site is near to impossible due to land scarcity and increasing of land prices especially in dhaka city. improperly disposed waste is posing serious health implications to the people and it may transmit various diseases especially by non-degradable wastes like polythene. rather, a proper segregation system to recover of resource from plastic wastes can play a very important role in mitigating the difficulties of solid waste that can act as a raw material for product design in bangladesh too. therefore, a comprehensive study report followed by a model of plastic waste segregation system for bangladesh has been highlighted in the paper. keywords: solid wastes, plastic wastes, segregation, resource recovery, product design. 1 introduction management of municipal solid waste (msw) is a widely discussed topic in the scientific community due to its importance in energy conservation, environmental sustainability, economic growth, safety and so on. in addition, it is now becoming a demanding issue due to the increased rate of industrialization, urbanization, per capita income and change of habits in life pattern of the people [1]. thereby, waste management (wm) has become one of the key issues across the globe including bangladesh especially in the mega cities like dhaka [2]. besides, volume and varieties of waste stream is also creating tremendous pressure on the disposal capacities, forcing the city authorities continuously to search out for optional and acceptable ways to deal with this demanding issue [3]. bangladesh being an emerging middle economy country has now a population of about 168 million with a density of around 1400 per square kilometer and is expected to rise up to about 177 million by 2025. presently about 21,332 tons per day of solid wastes (sw) are generated in this country. this estimation is projected to be increased up to 47,000 tons per day by 2030, wherein dhaka city subsidizes about 6870 tons per day [4]. dhaka is growing fast into an extended mega city with an enormous population growth rate of 6 percent per year and wastes are being generated at a faster pace due to the rapid growth of industries and population, which possesses a serious threat to the management of msw [5]. for instance, especially in dhaka city around 550 tones plastic wastes are accumulated per day [6]. among the msws, plastic wastes seem to be a threat to the environment as it creates toxic gases and parasites like dioxin, forun and pathogens that ultimately leads to the serious degradation of life of the living beings and the environment as well. especially, plastic wastes seriously contaminate the environment by all means, degrading the uddin and abedin (2021): international journal of engineering materials and manufacture, 6(4), 324-331 325 quality of soil, contaminating water body and air. to restore the problem, several researches have been concentrated in the transformation process from plastic waste into useful resources using different technologies. though plastic is one of the integral parts of our daily life, it plays vital role for polluting the environment. the more is the usage of the plastic products; the more is the pollution of environment gets. in recent years the plastic consumption has increased manifolds leading to accumulation of plastic waste in large amounts. therefore, the usage of plastic product is interrelated to the polluted environment affecting human and plant life. our aim should be towards reducing the plastic product and its usage but if not, then to move to recycling and make its wastage more of a resource. even if it’s not, then the process of segregating the plastics from main waste stream should be strongly practiced. therefore, a well-thought-out waste management system that would protect human health, natural resources and the environment, requires continual upgradation of the existing waste management system [7]. 2 waste scenario in the world the exponential growth of population, urbanization and development of the social economy, coupled with the improvement of living standards, have increased the amount of msw generation throughout the world. figure 1 shows the composition of municipal solid waste in the world where mostly organic waste (46%) are seen to be generated [3]. a twofold increase in global msw generation was observed from 2000 through 2010. during 2010, annually global msw generation was 1.3 billion mt, and by 2025, it is projected to reach 2.2 billion mt per year and 4.2 billion mt per year by 2050 [4]. such rapid rise of waste footprint will undoubtedly harm sustainable living style and the local environment (air, water, land) and human health, if not appropriately managed [5]. rapid population growth and the accompanied factors like profligate industrialization for national economic growth and urbanization causing severe msw management problems in several cities in developing and underdeveloped countries. generally, in european countries and organization for economic cooperation and development (oecd) countries, msw covers waste from households (82% of total msw), including bulky waste, waste from commerce and trade, office buildings, institutions, and small businesses, yard and garden waste, street sweepings, the contents of litter containers, and market cleansing waste [6]. the msw discussed in the paper, excludes the waste from municipal sewage networks and treatment and municipal construction and demolition waste. however, national descriptions, definition of msw may differ from country to country. in a developing economy like bangladesh, msw is generally defined as the waste produced in a municipality. most of the msws generated in developing countries are not segregated and may be either hazardous or non-hazardous. in general, whatsoever be the source of msw, its impact on the environment and quality of life is mainly related to air, water, and soil contamination. it is also associated with space consumption, odours, and aesthetic prejudice [7]. several different systems to separate food waste collection for later biological treatment have been implemented in european countries over the last decades. highly efficient methods based on source-segregation of household food waste exist in austria, germany, sweden, the netherlands and spain [8]. however, these systems have in common feature that without households' participation in the initial act of source-segregating, the efficiency is vastly decreased. 3 waste scenario in bangladesh in dhaka, msw is usually handled and processed by a large informal sector similar to other developing countries. but no separation scheme currently available here. also, no collection and disposal schemes are available for hazardous wastes. waste is generally collected by waste collectors who take the waste to the local waste collection point. then conventional open trucks are used to move the wastes to the landfill site. waste generation is significantly increased over the decades, and landfills are becoming scarce. a recycling industry runs its scheme to collect wastes. in the scheme, the waste is collected from door to door as well as from the collection point and landfill sites as well. figure 1: composition of municipal solid waste [3]. segregation of plastic waste from solid wastes: bangladesh perspective 326 as for renewable energy, waste is taken to the treatment site, where these wastes are turned into biogas to produce energy. the government is working with several ngos to develop biogas production plants and established 13,500 biogas plants [9]. the climate of bangladesh is also favorable for biogas production as it needs 35°c to produce biogas which is optimum to the average temperature of bangladesh. the government, municipality, private organization and ngos are involved to the waste management processes. figure 2. depicts a yearly increasing rate of solid wastes generation in bangladesh from 1985 to the predicted year of 2030 [2]. from the figure, it seen that solid waste generation has been abruptly increasing in bangladesh after 2015s mainly due to the change in economic income of manpower and increased rate of industrialization in bangladesh. figure 3 depicts the area of land needed for smooth disposal of solid waste in bangladesh from 1985 up to 2030 [2]. at present there are about 150 hectares of land allotted to accommodate the msw of all major cities of bangladesh till 2015. however, unfortunately, no facility has been augmented specialty about number and size of waste disposal areas. thereby, disposal sites are getting saturated with increased rate of msw in bangladesh. 4 composition and properties of waste of dhaka city in bangladesh majority of msw in bangladesh comprises of food wastes which is almost similar to other cities of the world. figure 4 shows various composition of msw of dhaka city. table 1 shows the state of solid wastes as per category of household, industrial, commercial wastes and at the same time moisture content of the solid wastes. proximate analysis is done to find the physical properties, and ultimate analysis is done to get the chemical properties. figure 2: urban ppopulation and waste generation from 1985 to 2030 for bangladesh [2]. figure 3: waste generation in tons and llandfill area in hectare in bangladesh [2]. 0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000 0 10,000,000 20,000,000 30,000,000 40,000,000 50,000,000 60,000,000 70,000,000 80,000,000 90,000,000 1985 1990 1995 2000 2005 2010 2015 2020 2025 2030 w a st e g e n e ra ti o n ( t o n s) u rb a n p o p u la ti o n year urban population waste generation(tons) 0 50 100 150 200 250 300 350 0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000 1985 1990 1995 2000 2005 2010 2015 2020 2025 2030 la n d fi ll ( h e ct a re ) w a st e g e n e ra ti o n ( t o n ) year waste generation(tons) landfill of 5mm depth(hectare) uddin and abedin (2021): international journal of engineering materials and manufacture, 6(4), 324-331 327 figure 4: waste composition of dhaka city of bangladesh in 2017. table 1: composition and properties of msw of dhaka city in bangladesh. component residential waste by weight (%) commercial waste by weight (%) industrial waste by weight (%) food and vegetable waste 59.51 62.05 26.37 paper products 11.21 6.28 7.59 plastics, rubber and leather 17.67 4.62 6.01 metals 0.15 0.28 glass and ceramics 0.37 garden wastes, tree trimming and straw 8.76 2.86 4.32 cloths 18.93 46.20 rocks, dirt and miscellaneous 2.30 4.62 9.49 moisture content (%) 50.00 54.00 60.00 biodegradable substances are those that naturally degrades or breaks down. in other words, natural agents such as sunlight, microorganisms, water, ozone, and others cause this decomposition, turning them into organic manure. example: food waste, paper, dead plants, wood, etc. [13]. non-biodegradable compounds are those that take a long time to degrade. certain goods cannot decay because of how they are processed, and they do not occur naturally. as a result, they affect our environment when they remain in the ecosystem for a long time without getting decomposed. example: plastic, glass, ceramics, metal [13]. hazardous waste is distinct from other wastes because it cannot be disposed of in the same manner as other by-products of our daily lives [14]. they can be found in different physical states such as gaseous, liquids, or solids. treatment and solidification processes can be needed depending on the physical condition of the waste. in our case, plastic is this type of waste. plastic cannot biodegrade; it breaks down into smaller pieces. toxic chemicals leach out of plastic and are found in nearly all of us' blood and tissue. burning of plastics can release dioxins, which are most harmful to human organisms. dioxin is a toxic organic chemical that contains chlorine, and it is produced when chlorine and hydrocarbons are heated at high temperatures. inhaling dioxin or being exposed to its fumes can cause many deadly results. 5 segregation of solid waste stream figure 5 shows the flow of waste, recyclables, and money in msw management in dhaka. in the figure, it is noted that the recyclable waste flows from disposal sites to the waste pickers and then to the recyclable shop. on the other hand, the recyclable waste flows from door-to-door mixed waste collector to the recyclable shop. generally, the msw is categorized into recyclable, biodegradable, and non-biodegradable wastes. here is our suggested msw flow that will make msw management much more efficient and affect the environment less. here, the waste flow has been established by different colours. generally, the flow of recyclable waste has been established and the rest of the waste is separated into 'biodegradable wastes' and 'non-biodegradable wastes,' which needs to be sent to the respective collection sites in the area. from there, the wastes are taken to the municipal collection point. non-biodegradable wastes are directly sent for treatment. on the other hand, biodegradable wastes go through a check to see if there is any non-biodegradable waste within them. if there is, they are sent for treatment too. biodegradable wastes are sent to disposal sites or landfills. additionally, the figure 6, shows the segregation process of biodegradable and bio non degradable wastes separately. food wastes (78%) paper (5%) polythene 3% plastic/rubber 2.50% wood 1.5% leather 1.5% textile 3.50% metal 1% glass 1% other 3% food wastes (78%) paper (5%) polythene (3%) plastic/rubber (2.5%) wood (1.5%) leather (1.5%) textile (3.5%) metal (1%) glass (1%) others (3%) waste stream segregation of plastic waste from solid wastes: bangladesh perspective 328 figure 5: flow of waste, recyclables and money in msw management in dhaka. figure 6: suggested msw flow. 7 collection of waste generation data in dhaka city of bangladesh the waste data of 50 houses for the month of april 2020, collected by the author for a local area of dhaka city in bangladesh and total manpower found to 250 and total amount of waste generated roughly around 498 kg/day. summarised information of the wastes is shown in table 2. a typical model of waste collection and disposal system of house hold waste and wastes disposal of associated community-based organization (cbo) has been developed by the author and shown in table 2. 1. amount of wastes of 30 houses per day = 115.60 kg. 2. waste generation in one month = 115.60 x 30 = 3450 kg. 3. total manpower found in 50 houses in one day 250 and in 30 days = 250x30= 7500. 4. per capita waste generation: 3450/7500 =0.46 kg per day. note: there are 4-6 persons in a house. 8 plastic waste segregation model from solid waste stream recently one more effective and workable waste collection and segregation model has been developed as shown in figure 7 which now practised by a group of community personnel comprising 280 houses and total manpower around 1050 living that community under saidpur city of bangladesh. figure 7 shows the separation process of both degradable and non-degradable wastes. the physical system of plastic waste segregation model is developed in the saidpur city of bangladesh. figure 8 shows the partial view of the of the plastic waste segregation system in saidpur city of bangladesh. the solid waste is randomly thrown in any roadside and the reiverside of bangladesh [figure 8(a)], however, people are generally seen to be engaged in segregating the wastes from the solid waste stream [figure 8(b)]. accordingly to the model doveloved in the saidpur city of bangladesh, the solid waste stream is systematically segregated to separte the plastic waste which is partially shown in the figures 8 (c), (d), (e) and (f), respectively. uddin and abedin (2021): international journal of engineering materials and manufacture, 6(4), 324-331 329 table 2: day wise waste collection data of 50 houses in dhaka city area of bangladesh in 2020. sn date composition of waste (in kg) amount (in kg) kitchen paper plastic rubber glass metal others total 1 1 april 2.50 0.20 0.20 0.20 0.06 0.14 0.24 3.54 2 2 april 1.90 0.15 0.25 0.30 0.05 0.09 0.20 3.00 3 3 april 1.90 0.10 0.20 0.05 0.05 0.40 2.50 4 4 april 2.00 0.10 0.20 0.20 0.05 0.05 0.45 2.55 5 5 april 2.00 0.16 0.25 0.30 0.20 0.10 0.40 3.25 6 6 april 2.10 0.15 0.25 0.25 0.05 0.15 0.50 3.60 7 7 april 1..90 0.15 0.25 0.35 0.05 0.05 0.35 2.75 8 8 april 2.05 0.10 0.25 0.25 0.10 0.12 0.43 3.14 9 9 april 2.75 0.15 0.25 0.35 0.22 0.15 0.40 3.40 10 10 april 2.50 0.15 0.25 0.22 0.15 0.15 0.30 2.80 11 11 april 1.75 0.15 0.20 0.35 0.15 0.50 2.90 12 12 april 2.50 0.10 0.35 0.25 220 13 13 april 1.90 0.15 0.25 0.30 0.05 00.26 2.86 15 15 april 2.00 0.10 0.20 0.05 0.05 0.50 3.00 16 16 april 1.80 0.15 0.25 0.30 0.12 0.14 0.60 3.12 17 17 april 2.15 0.16 0.24 0.25 0.56 3.15 18 18 april 2.75 0.15 0.25 0.30 0.05 0.05 0.25 2,85 19 19 april 1.25 0.15 0.10 0.43 2.78 20 20 april 2.65 0.32 0.25 0.30 0.60 3.40 21 21 april 2.50 0.14 0.25 0.11 0.22 0.23 2.99 22 22 april 2.67 0.14 0.3 0.10 0.35 0.40 3,22 23 23.april 2.57 0.13 0.24 0.25 0.15 0.05 0.32 3.14 24 24 april 1.77 0.15 0.25 0.36 0.25 0.34 3.40 25 25 april 2.55 0.17 0.22 0.25 0.25 0.15 0.25 3.10 26 26 april 2.00 0.15 0.25 0.31 0.55 3.45 27 27 april 2.50 0.12 0.25 0.22 0.23 0.35 0.46 3.15 28 28 april 1.90 0.15 0.23 0.33 0.15 0.35 3.14 29 29 april 2.03 0.11 0.13 0.22 0.35 3.12 30 30 april 2.10 0.15 0.25 0.22 0.12 0.36 3.30 total 72.10 5.40 6.00 6.60 6.9 6.3 12.3 115.60 figure 7: plastic waste segregation model from solid waste stream. metal crushing polythene glass tiles plastic & rubber paper bricks winding tape rice (pond) food items (biogas) food items (aerobic digestion) food items (composting) msw (source) separation degradable non degradable primary transfer station (pts) primary transfer station (pts) secondary transfer station (sts) fine separation fine separation segregation of plastic waste from solid wastes: bangladesh perspective 330 (a) solid waste stream filling (b) waste segregation randomly from solid waste stream (c) primary transfer station (pts) (d) secondary transfer station (sts) (e) plastic waste cage (f) plastic waste cage figure 8: partial view of the plastic waste segregation system in saidpur city of bangladesh. 9 conclusions the segregation of plastic waste from solid waste stream has been analyzed for bangladesh perspective. the following conclusions may be drawn from the present analysis. 1. msw management is essential for a developing country like bangladesh as its generation is increased coupled with an increase in population growth. nonetheless, management of the waste varies from country to country including its segregation process. once we cannot avoid the waste we should make endeavour as how can we turn waste into a good source of income and energy source rather than a burden. we have developed a step towards turning the waste beneficial for us by separating it at the source as a more efficient management uddin and abedin (2021): international journal of engineering materials and manufacture, 6(4), 324-331 331 method. for a country like bangladesh, cbo (community based organization) waste separation and management are more effective due to financial and land constraints. 2. the municipal solid waste (msw) management includes recycling, composting, disposal and waste-to-energy e.g. incineration. waste management is not possible with a single method. for this reason, a hierarchy of ranking strategy is also developed for municipal solid waste management. the waste management hierarchy consists of various levels: arranged from most preferred to least preferred methods based on their environmental soundness e.g. source reduction, reuse; recycling or composting; energy recovery; treatment and disposal. 3. unfortunately, general people of bangladesh are not much aware of the consequence of waste dumped as landfills. as we cannot avoid the waste, our effort has to be continued to make best use of wastes, with waste minimization strategy e.g. reduce, reuse and recycle (3r strategy). once we all will be motivated then wastes will no longer be a problematic issue. we must seek for the action plan as how best we get benefits out of the msw. it is only possible, if we can separate the waste at its source and technically manage it as a resource not considering it as burden. technical management plan of waste for resource recovery can lead to a substantial reduction in the overall waste quantities requiring final disposal in bangladesh and as well as in the globe. references 1. un data. (2012). country profile: bangladesh. [online]. available: http://data.un.org/ [11 march, 2021] 2. the study on solid waste management in dhaka city: clean dhaka master plan, jica final report for dhaka city corporation, ge jr 05-017, march 2005. 3. samah, m. a. a., manaf, l. a., aris, a. z. & sulaiman, w. n. a. (2011). solid waste management: analytical hierarchy process (ahp) application of selecting technology for malaysia. current world environment (cwe) journal, 6, 1-16. 4. ahammed, a. a. (2013). selection of the most appropriate package of solar home system using analytic hierarchy process model in rural areas of bangladesh. renewable energy, 55, 6-11. 5. marie, m. (2009). energy system analysis of waste-to-energy technologies. phd thesis, alborg university, denmark. 6. state of practice for emerging waste conversion technologies, final report of us environmental protection agency (epa), epa/600/r-12/705, october 2012. 7. enayetullah, i., sinha, a. h. m. & akhter, s. s. (2012). urban solid waste management scenario of bangladesh: problems and prospects. waste concern technical documentation,102-110. 8. bruce, j. c. & marc, j. r. (2010). economic feasibility of a plasma arc gasification plant. proceedings of the 18th annual north american waste-to-energy conference, nawtec18, 11-13, florida, usa. 9. islam, k. m. n. (2017). municipal solid waste to energy generation: an approach for enhancing climate cobenefits in the urban areas of bangladesh. renewable and sustainable energy reviews, 81(2), 2472-2486. 10. shiri, n. v., kajvana, p. v., ronjon, h. v., pais, n. l. & naik, v. m. (2015). processing of waste plastics into building materials using a plastic extruder and compression testing of plastic bricks. journal of mechanical engineers and automation (jmea), 5(3-b), 39-42. 11. chiemchasisri, c., charnnok, b. & visvanathan, c. (2010). recovery of plastic wastes from dumpsite as refuse – derived fuel and its utilization in small gasification system. elsevier bio resource technology, 101, 1522–1527. 12. janajreha, i., adeyemia, i. & elagroudy, s. (2020). gasification feasibility of polyethylene, polypropylene, polystyrene waste and their mixture: experimental studies and modeling. sustainable energy technologies and assessments, 39, 100654. 13. topacio, a., arkuino, r. c., romano, k. v. & abutin, j. c. (2018). development of hydrophobic composite roof tiles utilizing recycled plastic materials. material engineering and development, 65-72. 14. gangaraju, p. m., ramayya, k.v., praksh, p. b., basha, s. k. g. & kumar, b. s. (2020). making of plastic tiles using waste plastic collected from fertilizer bags, plastic wires and waste tyre tubes (polypropylene, polyurethane, thermoplastic and polyester). international journal of advanced science and technology, 29(5), 7657-7662. http://data.un.org/ https://www.sciencedirect.com/science/journal/13640321 international journal of engineering materials and manufacture (2021) 6(3) 114-123 https://doi.org/10.26776/ijemm.06.03.2021.02 rodrigo ferreira 1,2 , gabriel lopes de castro martinelli 2 , alessandro roger rodrigues 2 and reginaldo teixeira coelho 2 1 department of control and industrial processes, federal institute of pernambuco, av. luís freire, 500 cidade universitária, cep 50740-545, recife – pe, brazil. 2 são carlos school of engineering, university of são paulo, brazil e-mail: rodrigoferreira@recife.ifpe.edu.br reference: ferreira et al. (2021). tool feed and burr size influence on wettability of ti6al4v micro end-milled. international journal of engineering materials and manufacture. 6(3), 114-123. tool feed and burr size influence on wettability of ti6al4v micro endmilled ferreira, r., martinelli, g. l. c., rodrigues, a. r. and coelho, r. t. received: 26 february 2021 accepted: 29 april 2021 published: 15 july 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract surface texturing, using micro-milling, has promising applications in the industry of medical implants, since it can assist cell adhesion and thus improve osseointegration. ti6al4v alloy is used as implant material due to its excellent biocompatibility and high mechanical strength. however, those mechanical properties reduce machinability creating some challenges for micro-milling. the way to initially assess cell adhesion is using surface wettability, usually conducted with water. at the present work, micro-channels were machined in ti6al4v by micro end-milling with 500 µm width per 50 µm depth with 1000 µm distant from each other. the effect of feed per tooth (fz) on wettability was analysed and some interesting relations with burrs formed on channel walls were obtained. values of feed per tooth were 3, 6, 12 and 15 µm. wettability results showed that slotted surface is more hydrophilic on channel direction, with contact angles around 30° to 43°. in contrast, on the perpendicular direction the surface tends to be hydrophobic with contact angles between 75° and 146°. in addition, contact angle increases (hydrophobic tendency) as feed per tooth increases (along with roughness), even on channel direction. the presence of burrs also tends to disturb wettability results. therefore, surface wettability depends on channel direction, burr size and tool feed per tooth, as well. keywords: micromilling, wettability, ti6al4v, surface roughness, burrs. 1 introduction implants made of pure titanium or ti6al4v alloy, begin with conventional machining processes, such as turning and/or milling, which produce characteristic roughness and macro textures on the surface, allowing initial biological integration [9]. micro-milling can create 3d textures to help cell adhesion, growth and proliferation, due to its characteristics [20]. however, there are still few studies relating feed per tooth and the influence of burrs on surface wettability, which is the first indication for good biological integration with human body, when applied to medical implants. textured surface for implants has been extensively investigated lately to reduce healing time and reducing body rejection, after work published by brånemark et al., 1969 [2]. nowadays, the number of implants tends to increase, since life span is steadily growing and customization will be even more necessary. first studies addressing facial titanium implants in dentistry applications, between 1969 and 1980, realized that surface roughness could significantly affect healing period, which was later referred as osseointegration [1]. shorter times for osseointegration and, consequent success in medical implants, are straightly related with cell adhesion, growing and proliferation [3]. in order to develop and stimulate those vital cell mechanisms, implant material has to match body region, roughness and textures must be adequate at macro-, microand nano-levels as well as surface energy [12]. after 1990 new surface treatments, after machining, such as thermal aspersion, chemical corrosion, sand blasting and anodization have contributed to improve implant surface even further. some biomimetics process, coating with hydroxyapatit and using some bio-glasses are another ways to improve osseointegration phenomena potentially [7]. overall, machining has been the most promising process to create textures to improve wettability and, as a consequence, biological integration. recent publications, such as, pratap & patra, 2018b [15] reported that certain tool feed and burr size influence on wettability of ti6al4v micro end-milled 115 geometries obtained with micro ball noses can affect wettability. wang et al., 2016 [21] shown that combining micromilling and anodization led to better cell adhesion. in a recently published article on micro dimples, indicated that micro-textures type conical modify bacterial adhesion on the surface [8]. one of the variables indicated to assess the potential of an implant surface is wettability. the wettability may indicate how the blood will behave interacting with the material surface and its speed to promote better osseointegration [16]. thus, when proposing the construction of topography in biomaterials at the macro, meso, micro and nanometric scales, it is necessary to investigate the wettability and its interaction with the topography and roughness [18]. depending on the implant region, a more uniform wettability can be chosen, where the fluid spreads evenly over the surface. another possibility is the creation of grooves so that the spreading is more effective in one direction. this effect of spreading non-uniform fluid is called wettability anisotropy [6]. grooves on the surface of ti6al4v have enhanced cell adhesion compared to smooth surfaces [4]. micro-milling can be an alternative for the manufacture of cavities (slots or channels) that promote anisotropy of wettability and have potential application in metallic implants. the present work investigates wettability of ti6al4v of a surface textured with micro channels. channels were end-milled with increasing values of feed per tooth (fz), resulting in different roughness values and some burrs at the walls. wettability results were different, depending on roughness at the bottom of channels, on direction and on burr shape, orientation and dimensions. 2 materials and methods 2.1 material and experimental set-up the material used was ti6al4v eli (extra low interstitial) titanium alloy in the annealed condition and with the presence of the α and βphases, in the form of hot-rolled sheets produced by the company timet, which meets the requirements found in the astm f136 standard. table 1 contains the typical chemical composition of the sample, hardness (rockwell scale) and average grain size according to astm e112-12. table 1: typical chemical composition ti6al4v, grain size and hardness. elements fe v al c o n grain size astm (µm) hardness (rc) weight percent 0.18 4.08 5.98 0.009 0.11 0.009 10 30 the samples of ti6al4v/eli alloy were initially prepared by gently flat-milling them into small blocks with 12 x 26 x 10 mm. a flat-end mill, diameter 20 mm, with 2 inserts, was used working with 720 rpm, fz = 0.050 mm/tooth and depth of cut 0.100 mm. insert recommendations (r390-11 t3 08m-pl 1030) for cutting conditions. the texture experiments were carried out on a three-axis machining centre (hermle c800u), 500 nm positioning system (±3µ). in its spindle, a nsk nakanishi hes 510 milling spindle was clamped. the hes 510 is capable of speeds up to 50,000 rpm continuously variable from 6,000 upwards. the speed control is the nsk controller nakanishi astro e500z. maximum tool run-out error was 2.0 µm. tools used were all flat-ended micro mill, solid carbide, two fluted type ms2ms d0050, diameter 500 µm (figure 1a), multilayer coating of tialn (figure 1b and 1c) and micro-grain cemented carbide substrate (grain size <0.6 µm), edge radius rε of 2.2 µm (figure 1e and 1f) measured in the ols 4100 olympus confocal microscope. for each test a new tool was used and its cutting-edge aspect, rake and clearance face were examined under the confocal and sem (figures 1d and 1e). ferreira et al. (2021): international journal of engineering materials and manufacture, 6(3), 114-123. 116 figure 1: characterization of the micro tool. a) tip of the micro end mill. b) higher magnification of the cutting edge for eds analysis. c) result of the eds chemical analysis. d) edge view by sem. e) confocal view to measure the edge radius. f) measurement of the edge radius. initially, the machining centre went through warm up for 30 minutes before each test. the milling operations produced full slots (channels) in one-step cutting (figure 2a). each slot (channel) was cut on the y-axis direction (figure 2a) and twenty-six of them were produced, along the x-axis with 1000 µm of pitch (p) (figure 2b). all channels were set for 50 µm depth of cut (doc) and resulted in 500 µm wide. values of feed per tooth (fz) used were: 3, 6, 12 and 15 µm. the cutting speed was set at 44 m/min and the speed set on the nakanishi hes 501 fixed at 28,000 revolutions per minute (figure 2a). figure 2: configuration for slot cutting. a) general view and cutting parameters. b) geometry of the channels in the front view and c) top view. tool feed and burr size influence on wettability of ti6al4v micro end-milled 117 2.2 wettability the contact angle (θ) between the liquid and solid phase is an essential parameter for inferring surface energy and evaluating the surface wettability [17]. at the present investigation, the attension biolin™ tensiometer, depositing 3 µl of deionized (di) water on the surface, was the elected technique. before the test, all samples were cleaned in an ultrasonic acetone bath. the calculation of the contact angle (θ) uses the young-laplace equation and was measured over 10 seconds. the baseline and vector lines between the external surface of the di water drop and the solid surface were determined using one attension™ software. three measurements in different regions were performed on each sample (first channels, central ones and final ones) with an average measurement between the left and right angles (referred to as θl and θr, respectively). images taken from the front and side of the channels served to evaluate the cases presented in figure 3a e 3b. the shape of the droplet and its spreading enabled the qualitative assessment of wettability in both directions, i.e., along channel direction and perpendicular to it. some significant anisotropy in wettability was found [13]. anisotropy of wettability is a phenomenon that is correlated to the non-uniform spreading of the drop deposited on the surface [11]. thus, the creation of specific micro textures has a strong influence on wettability and may require analysis in different directions (figure 3b). figure 3: analysis of wettability for smooth surfaces and with directional micro textures. a) uniform wetting behaviour, the front and side views of wettability have similar contact angles. b) directional micro textures with a difference in the contact angle as a function of direction. in this case, the contact angles in the front view will be different from the side view. 2.3 superficial characterization three-dimensional surface topography and area roughness (sa) inside the channels were measured by confocal microscopy ols 4100. roughness measurements were taken in channels 1, 14 and 26 of all pieces manufactured in relation to the x direction at the tool entrance, middle length and at tool exit of each specific channel. burr height measurements were performed using the olympus lext 4100 software. the measurements made in the regions of interest used the roi (region of interest) tool of the lext software (confocal microscopy), where it is possible to delimit an area. in our case we used a squared region with 200 µm of side. scanning electron microscopy (sem) was also performed on the leo 440 microscope for selected cutting condition, in order to evaluate the burr formation in up and down milling locations. 3 results and discussion figure 4 shows general aspects of channels obtained with different value of feed per tooth (fz) at increasing magnifications. the lowest fz value (3 µm) produced the most severe burrs on both sides of the channel, the up and down milling. it can also be noted protruding burrs inside and outside the channels. increasing fz to 6 µm, figure 4b, there is a considerable reduction of burrs, however they continue to protrude inside and outside the channels. when ferreira et al. (2021): international journal of engineering materials and manufacture, 6(3), 114-123. 118 using fz = 12 µm and 15 µm, shown in figures 4c and 4d, burrs are at the same magnitude, but are clearly pushed outside the channels. figure 4: scanning electron microscopy fz = 3, 6, 12 and 15 µm. a) severe burr formation for fz = 3 µm. b) lower burr formation for fz = 6 µm. c) lower burrs pushed outside of the channels for fz = 12 µm. d) lower burrs and pronounced feed marks for fz = 15 µm. confocal microscopy was used to evaluate 3d images of the channels e their cross sections, also assessing burrs on the walls. figure 5a shows one channel produced with fz = 3 µm where it can be seen aspects of the burrs, such as their height. in comparison, figure 5b, used fz = 6 µm, shows some lower burrs. on the other hand, figures 5c and 5d show burrs bending on both sides of the walls. figure 5e shows average heights on both walls, up and down a) b) c) d) tool feed and burr size influence on wettability of ti6al4v micro end-milled 119 milling. it is noted that fz = 6 and 12 µm produced the lowest burr heights simultaneously on both walls, similarly to thepsonthi & özel, 2014 [19]. figure 5: 3d topographies for channels manufactured with different feeds per tooth. a) fz = 3 µm. b) fz = 6 µm. c) fz = 12 µm. d) fz = 15 µm. e) graph of burr height as a function of feed per tooth. figure 6 shows values of surface roughness, sa, as a function of fz. it can be noted that roughness has a direct relation with fz, being sa = 55 nm, the lowest value using fz = 3 µm, similar to results found by ziberov et al.,2020 [23]. in contrast, the channel machined with fz = 15 µm reached a maximum of sa = 321 µm, combined with a relatively high value of burr height. figure 6: a) values of surface roughness, sa, as a function of feed per tooth. b) machined surfaces images. ferreira et al. (2021): international journal of engineering materials and manufacture, 6(3), 114-123. 120 figure 7 shows results of wettability measuring the contact angle as a function of fz, initially perpendicular to the channel direction. the drops of water were landed on the first channels, on the last ones and on the centrals. that intended to assess wettability all over the produced texture on the same surface. figure 7: contact angle depending on fz and the position of the channels. the displayed direction is perpendicular to the channel direction (front view). looking only on the first channels of all fz values, it can be noted an increase on contact angle (hydrophobic surfaces). that behaviour seems to follow surface roughness, which also increases with similar tendency. high values of surface roughness seem to create obstacles for water to spread and aggravated by high walls due to burr heights, especially when fz = 3 µm. looking now at central channels only, fz = 3, 6 e 12 µm, are all hydrophobics. however, fz = 15 µm shows lower contact angle, slightly lower than 90° going to the hydrophilic direction. that cutting condition combined lower burr height and burrs pushed outside, which allowed water to spread over the channels easier than when burrs were higher. lateral burrs, result smooth when cutting forces are higher, due to unavoidable edge wear during micro milling [5]. although tool wear was negligible after each experiment, some edge rounding was observed, which could have been the cause for burr shape observed. figure 8 shows contact angle measured on the channel direction. all angles were well below 90°, resulting in hydrophilic surfaces [13]. however, contact angles moderately increase with fz, up to 12 µm. such phenomenon is related with roughness and the surface shape left by the tool edge (see figure 4), which creates higher obstacles for water spreading [10]. the super hydrophilic results for fz = 3 µm can be attributed to a combination of low surface roughness at the bottom of the channels, with higher walls (due to burrs heights) making easy for the water to spread along the channel and difficult to overcome the walls. similar results were found by yanling, jian, & huadong, 2018 [22] for the micro-milling of al6061, this work showed the influence of burrs in preventing the spread of the drop deposited on the surface, generating hydrophobic surfaces in the front and side views. such tendency did not continue with fz = 15 µm, because surface roughness at the bottom of the channels reached certain values that impeded water to spread further inside, allowing it to overflow the channels. the direction of the burrs, pushed outside for fz = 15 µm, also facilitated overflow. tool feed and burr size influence on wettability of ti6al4v micro end-milled 121 figure 8: contact angle as a function of fz and channel position. comparing contact angles measured in perpendicular directions (figures 7 and 8), there is a notable anisotropy regarding wettability, due to the selected texture made by micro channels. along the channels results indicate hydrophilic behaviour and perpendicular hydrophobic one [14]. internally water molecules are attracted to each other, due to cohesion, and at the contact with air, or with a solid, they can be attracted due to adhesion. when the drop of water first touches the ti6al4v surface, it will search for the shape with minimum surface area possible, due to surface tension effect. the final shape of the water will result from the equilibrium of those attractions, minimizing the surface tension. firstly, the water fills the micro channels starting from the bottom. it is easy to run on the bottom because it has to adhere to the metal and only overcome the surface roughness on the bottom and on the walls. as expected, the droplet stretches more within the micro channels. that spreading stops when the adhesion between water molecules with air, and with metal, reaches the equilibrium with the cohesion between them internally. such equilibrium happens at the bottom and on the walls. simultaneously, the same equilibrium has to be achieved perpendicularly, over the micro channels, because the volume of water allows overflow. to overflow, however, enough potential energy has to be spent to reach the top of the burrs and run on the space between channels. that path seems to require much more energy because all droplets spread much less across the channels. for low roughness on the bottom and walls, when peaks and valleys are smooth, and circular in shape, water spreads easily. for roughness with the same shape, but with higher peaks and deeper valleys more energy has to be spent and water does not spread as far, before starts overflowing. if the height of the walls is lower, due to lower burrs, the water can now spread further. the shape of the burrs has also significant role to play and the spreading can be easier if burrs are pushed outside the channels, keeping the walls smoother. therefore, anisotropy in wettability can be explained based on these considerations, according to the results found at the present work. further investigations will also be needed, especially on the chemical compositions of the oxide layers present on the ti6al4v surface, after micro milling, since different oxides can have different adhesion forces on water molecules. 4 conclusions the study performed to investigate the influence of different values of feed per tooth (fz) on the wettability of ti6al4v, texturized by micro end milling, allowed the following conclusions: 1. values of fz between 6 and 12 µm minimized burrs on the top of the walls. those seems to be the best conditions for texturizing surfaces of medical implant. surfaces created inside the micro channels, on bottom and walls, indicate hydrophilic behaviour, which is a good indication for biological integration; 2. lower and higher values of fz, 3 µm and 15 µm, respectively, still produced hydrophilic surfaces inside the channels, but with excessive burrs at the top of walls, being less suitable for implants. ferreira et al. (2021): international journal of engineering materials and manufacture, 6(3), 114-123. 122 3. the selected texture with micro channels 50 x 500 µm, having a pitch of 1000 µm proved to be hydrophobic on the direction perpendicular to the channels. however, such texture may be useful only for specific applications on medical implants, for example in regions where directional wettability is required; 4. modifications on the selected texture, for example, reduction of pitch, may improve the wettability and reduce anisotropy, using 6 and 12 µm to minimize burr formation. acknowledgement the authors would like to thank mitsubishi brasil and, more specifically, its employees thiago rigo (tr tools) and émerson matsumoto for providing technical information. we also thank the company engimplan engenharia de implantes for supplying the titanium alloy ti6al4v and the federal institute of pernambuco for the phd permit of the author. we thank to the employees of the institute of chemistry of são carlos, phd. márcio de paula and msc. andré tognon, for their analysis in the scanning electron microscope and tensiometer. thanks also go for fapesp grant 2016/11309-0. references 1. branemark, p. i. (1983). osseointegration and its experimental background. the journal of prosthetic dentistry, 50(3), 399–410. https://doi.org/10.1016/s0022-3913(83)80101-2 2. brånemark, p. i., breine, u., adell, r., hansson, b. o., lindström, j., & ohlsson, a. (1969). intra-osseous anchorage of dental prostheses: i. experimental studies. scandinavian journal of plastic and reconstructive surgery and hand surgery, 3(2), 81–100. https://doi.org/10.3109/02844316909036699 3. brett, e., flacco, j., blackshear, c., longaker, m. t., & wan, d. c. (2017). biomimetics of bone implants: the regenerative road. bioresearch open access, 6(1), 1–6. https://doi.org/10.1089/biores.2016.0044 4. gui, n., xu, w., tian, j., rosengarten, g., brandt, m., & qian, m. (2018). fabrication and anisotropic wettability of titanium-coated microgrooves. journal of applied physics, 123(9). https://doi.org/10.1063/1.5020517 5. han, j., hao, x., li, l., zhong, l., zhao, g., & he, n. (2020). investigation on micro-milling of ti–6al–4v alloy by pcd slotting-tools. international journal of precision engineering and manufacturing, 21(2), 291–300. https://doi.org/10.1007/s12541-019-00247-1 6. holmes, h. r., & böhringer, k. f. (2015). transporting droplets through surface anisotropy. microsystems and nanoengineering, 1(0), 1–9. https://doi.org/10.1038/micronano.2015.22 7. jaeger, n. a. f., & brunette, d. m. (2001). production of microfabricated surfaces and their effects on cell behavior. in titanium in medicine material science, surface science, engineering, biological responses and medical applications (vol. 216, pp. 343–374). https://doi.org/10.1007/978-3-642-56486-4_11 8. jain, a., kumari, n., jagadevan, s., & bajpai, v. (2020). surface properties and bacterial behavior of micro conical dimple textured ti6al4v surface through micro-milling. surfaces and interfaces, 21(september), 100714. https://doi.org/10.1016/j.surfin.2020.100714 9. kang, c. w., & fang, f. z. (2018). state of the art of bioimplants manufacturing: part i. advances in manufacturing, 6(1), 20–40. https://doi.org/10.1007/s40436-017-0207-4 10. kim, j. h., kang, s. m., lee, b. j., ko, h., bae, w. g., suh, k. y., … jeong, h. e. (2015). remote manipulation of droplets on a flexible magnetically responsive film. scientific reports, 5, 1–10. https://doi.org/10.1038/srep17843 11. kwon, d., wooh, s., yoon, h., & char, k. (2018). mechanoresponsive tuning of anisotropic wetting on hierarchically structured patterns. langmuir, 34(16), 4732–4738. https://doi.org/10.1021/acs.langmuir.8b00496 12. liu, m., zeng, x., ma, c., yi, h., ali, z., mou, x., … he, n. (2017). injectable hydrogels for cartilage and bone tissue engineering. bone research, 5(november 2016). https://doi.org/10.1038/boneres.2017.14 13. ma, c., bai, s., peng, x., & meng, y. (2013). anisotropic wettability of laser micro-grooved sic surfaces. applied surface science, 284, 930–935. https://doi.org/10.1016/j.apsusc.2013.08.055 14. pratap, t., & patra, k. (2018a). direction dependent dynamic wetting of semi-hemispherical end micro-groove textured ti-6al-4v surface. surface and coatings technology, 356(july), 138–149. https://doi.org/10.1016/j.surfcoat.2018.09.037 15. pratap, t., & patra, k. (2018b). fabrication of micro-textured surfaces using ball-end micromilling for wettability enhancement of ti-6al-4v. journal of materials processing technology, 262(june), 168–181. https://doi.org/10.1016/j.jmatprotec.2018.06.035 16. rabel, k., kohal, r. j., steinberg, t., tomakidi, p., rolauffs, b., adolfsson, e., … altmann, b. (2020). controlling osteoblast morphology and proliferation via surface micro-topographies of implant biomaterials. scientific reports, 10(1), 1–14. https://doi.org/10.1038/s41598-020-69685-6 17. rupp, f., gittens, r. a., scheideler, l., marmur, a., boyan, b. d., schwartz, z., & geis-gerstorfer, j. (2014). a review on the wettability of dental implant surfaces i: theoretical and experimental aspects. acta biomaterialia, 10(7), 2894–2906. https://doi.org/10.1016/j.actbio.2014.02.040 18. tan, j., & saltzman, w. m. (2004). biomaterials with hierarchically defined microand nanoscale structure. tool feed and burr size influence on wettability of ti6al4v micro end-milled 123 biomaterials, 25(17), 3593–3601. https://doi.org/10.1016/j.biomaterials.2003.10.034 19. thepsonthi, t., & özel, t. (2014). an integrated toolpath and process parameter optimization for highperformance micro-milling process of ti–6al–4v titanium alloy. international journal of advanced manufacturing technology, 75(1–4), 57–75. https://doi.org/10.1007/s00170-014-6102-2 20. wan, y., wang, t., wang, z., jin, y., & liu, z. (2018). construction and characterization of micro/nanotopography on titanium alloy formed by micro-milling and anodic oxidation. international journal of advanced manufacturing technology, 98(1–4), 29–35. https://doi.org/10.1007/s00170-017-0323-0 21. wang, t., wan, y., kou, z., cai, y., wang, b., & liu, z. (2016). construction of a bioactive surface with micro/nano-topography on titanium alloy by micro-milling and alkali-hydrothermal treatment. proceedings of the institution of mechanical engineers, part h: journal of engineering in medicine, 230(12), 1086–1095. https://doi.org/10.1177/0954411916675382 22. yanling, w., jian, y., & huadong, y. (2018). superhydrophobic surface prepared by micro-milling and wedm on aluminum alloy. materials research express, 5(6). https://doi.org/10.1088/2053-1591/aac6a3 23. ziberov, m., de oliveira, d., da silva, m. b., & hung, w. n. p. (2020). wear of tialn and dlc coated microtools in micromilling of ti-6al-4v alloy. journal of manufacturing processes, 56(may), 337–349. https://doi.org/10.1016/j.jmapro.2020.04.082 international journal of engineering materials and manufacture (2021) 6(3) 152-162 https://doi.org/10.26776/ijemm.06.03.2021.06 almusaied, z. i. and asiabanpour, b. ingram school of engineeringtexas state university san marcos, tx 78666 usa e-mail: ba13@txstate.edu reference: almusaied and asiabanpour (2021). a novel design of hybrid hydrophilic-superhydrophobic surfaces for fog harvesting. international journal of engineering materials and manufacture, 6(3), 152-162. a novel design of hybrid hydrophilic-superhydrophobic surfaces for fog harvesting zaid almusaied and bahram asiabanpour received: 28 february 2021 accepted: 01 may 2021 published: 15 july 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract the continuous growth in the human population and climate change exacerbates the problems related to water scarcity. harvesting the atmospheric water can mitigate the water scarcity in many regions around the globe. fog collection using hybrid hydrophilic-superhydrophobic surfaces has the capacity to achieve a higher water collection rate. in this paper, a new method and materials are introduced to create the hybrid surfaces. the method includes additive manufacturingto make sheets with holes-, mixing and casting polymeric matrix composite, and a controlled spray coating mechanism. the materials comprised of hydrophobic coating on top of the acrylic printed sheet and hydrophilic composite. the ratios of the pitches to diameters of the hydrophilic regions varied during the experiments to obtain the best water generation. the water collection rate for the sample with diameters of 583 um and a pitch of 1600 um has achieved 57% more than the untreated hydrophilic sample. the contrast in wettability accomplished by this novel method has the potential to be implemented on a large scale for atmospheric water harvesting. keywords: hydrophilic, superhydrophobic, hybrid surfaces, fog harvesting, additive manufacturing 1 introduction water is considered one of the most fundamental substances to life on earth. it comprises a significant percentage of all living creatures; 60% of an adult human body is made of water [1]. the projection of the world health organization (who) for drinking and domestic needs of water is averaging from 50 to 100 litres per person per day [2]. furthermore, water is needed and used heavily in agriculture and various industries. the food and agriculture organization (fao) forecasted that 1.2 billion people already reside in agricultural regions facing insufficient water supply [3-4]. urban areas around the globe are likewise facing shortages with quantity and/or quality. the united nations' projection for the urban dwellers not having adequate supply and management of water increased by 50% since 2000 [5]. the continuous growth in the global population will increase the demand for freshwater, and more areas will face the shortage. the water crises are also aggravated by climate change through the increase in droughts occurrence [6]. the united nations expects 4.8 to 5.7 billion people to suffer from water shortage by 2050 for at least one month per year [7]. while water covers 71% of our planet, less than 1% of this water is usable freshwater [8]. many approaches have been considered and pursued to overcome water shortages. seawater desalination is one of them, yet the process requires high investment and consumes high energy [9]. one of the other approaches to solve the water crisis is to collect water from sustainable-untapped resources such as the water in the atmosphere. the estimation of the amount of water in the atmosphere is about 3000 cubic miles [8]. the water in the atmosphere can be in a gaseous or condensed form. the fog consists of tiny water droplets that reside in the air, with a small diameter ranging from 1 to 40 um [10]. many floras and faunas have evolved throughout millions of years to survive in a harsh dry environment by harvesting the atmosphere's water. among the many observed creatures to do so are the namib beetle desert (stenocara gracilipes), various cactaceae species, the green tree frogs (litoria caerulea), the cribellate spider (uloborus walckenaerus), and the bermuda grass (cynodon dactylon) [11-13]. these creatures have unique wetting characteristics and surface structures that lead to efficient water generation either by dewing or fog basking. the dewing process includes a phase transfer where the water vapor condenses into the water as the temperature drops below the dewpoint. in comparison, fog basking is mainly a collection of fog's tiny water droplets. a novel design of hybrid hydrophilic-superhydrophobic surfaces for fog harvesting 153 the stenocara beetle inhabits the namib desert, where the annual rainfall is fewer than 13mm, and the fog happens around 30 days per year [9]. the beetle's dependence on fog harvesting was a source of intensive studies and biomimicry. the pioneering work of parker and lawrence (2001) suggested that the beetle's dorsal consists of random hydrophilic bumps, with a diameter of 0.5mm and a pitch of 1-1.5mm in the middle of the waxy hydrophobic region [14]. more recent studies by nørgaard and dacke (2010) postulate that the stenocara beetle has a hydrophobic surface rather than a hybrid hydrophilic-hydrophobic nature [15]. yet, the research to make and study hybrid surfaces for both condensation and fog harvesting during the last couple of decades has successfully shown such surfaces' efficiency [16-24]. the construction of hybrid surfaces by the researchers varied with materials, processes, and their complexity. parker and lawrence (2001) created a simple hybrid surface by embedding hydrophilic sphere glasses with a diameter of 0.6 mm in hydrophobic wax [14]. the water collection rate of their hybrid surface was more than that of the hydrophobic wax [14]. mondal et al. used needles as the hydrophilic part and penetrated them through superhydrophobic sheets to create hybrid surfaces for water collection by dewing [16]. hou et al. formed the hybrid surface using photolithography and etching to fabricate hydrophilic micro-pillars of silicon dioxide surrounded by superhydrophobic fluorinated nano-grass and tested their condensation efficiency [17]. garrod et al. created the hybrid surfaces by plasmachemical deposition and modification with a broad study of the affective dimensions, and pitches of the hydrophilic part to the hydrophobic region were implemented [18]. zhang et al. (2015) used inkjet printing to achieve a micropattern of the hydrophilic array on top of the superhydrophobic layer [19]. their printed super hydrophilic array was created by in situ polymerization of polydopamine [19]. wang et al. (2015) made the biphilic surface by using thermal pressing to attach treated superhydrophobic metal gauzes to a hydrophilic polystyrene sheet [22]. wong et al. (2015) created a hybrid surface of micropatterned hydrophilic poly (2hydroxypropyl methacrylate) on hydrophobic polystyrene with the dewetting process [24]. while the aforementioned methods successfully created and examined the efficacy of the hybrid surfaces with different sizes, the majority of them used expensive and complicated procedures. in this paper, a new, inexpensive method is introduced to create hybrid surfaces. the hybrid surfaces made here consist of an array of hydrophilic regions in the middle of a superhydrophobic. the surfaces are fabricated using additive manufacturing, spray coating, polymeric matrix composite mixing, and casting. the paper postulates that the water collection rate (wcr) can be enhanced by using the new hybrid surfaces. furthermore, the research explores the hybrid surfaces’ wcr by changing the hydrophilic region’s diameter and between them. the rest of this paper is organized as the following. in section 2, materials, equipment, samples’ preparation, and experiment setup are presented. section 3 illustrates the results and discussion including the samples' dimensions, samples' wettability, and the water collection rate for the samples. the conclusion is presented in section 4. figure 1: the stenocara gracilipes. the beetle inspired the research of hybrid surfaces. the beetle inhabits the namib desert, and it depends on fog to generate its water [14]. 2 materials, equipment, samples preparation and experiment setup 2.1 design, materials, equipment, and samples preparation in this research, eight samples were prepared. the samples were distributed as follows: six were hybrid surfaces, one hydrophilic, and one superhydrophobic. the sample's preparation included the design of the sample and separate implementation of the superhydrophobic portion and the hydrophilic part, and finally attaching them to create a controlled array of hydrophilic regions in the superhydrophobic area. almusaied and asiabanpour (2021): international journal of engineering materials and manufacture, 6(3), 152-162. 154 hybrid surface hydrophilic regions superhydrophobic area the design criteria for the hybrid surfaces include a four-by-four array of hydrophilic circles. the diameter of the circles is designed to be 400um for three samples and 500um for the other three. the pitches for the hydrophilic regions are designed to vary from 1.5, 2, and 3 of the diameters. figure 2: the holes' diameters and pitches of the sheets. the purpose of the design is to control the ratio of the superhydrophobic to the hydrophilic area in the samples. table 1: the design criteria for two different diameters with three pitches for the hybrid surface to evaluate the best ratio to enhance the water collection rate. hole diameter pitch = 1.5 diameter pitch = 2 diameter pitch = 3 diameter 400 600 800 1200 500 750 1000 1500 the superhydrophobic part is made using additive manufacturing and spray coating. the designs were first created using autocad inventor. the samples' peripheral dimensions were 14.5mm by 12.5 m, while the thickness of the sheets designed to be 100um. additionally, two l-shape frames were added to each sample to prevent the warping of the sheet due to the cleaning and its small thickness. polyjet 3d printer (stratasys objet260) is used to print the samples. the materials used for printing are made of acrylic monomer, exo-1,7,7-trimethylbicyclo (2.2.1) hept-2-yl acrylate; tricyclodecane dimethanol diacrylate, photoinitiator, acrylic oligomer, and titanium dioxide. the printing ensured minimum support material by including the optimum orientation, glossy and high-quality print settings. the printed sheets were collected and cleaned manually using a spatula and di water, then sonicated with non-ionic soap and di water for ten minutes for each step. later, the sheets were cleaned with acetone, methanol, isopropanol. the next step was converting the printed sheets into superhydrophobic by coating them. the superhydrophobic coating was made by mixing 10mg/ml of hydrophobic fumed silica and ethanol. the sheets attached to a slide glass and airbrush were used to coat them. a controlled speed stage was made to ensure consistency for all samples. the stage consisted of a lead screw, arduino, stepper motor, and dual h bridge driver. the airbrush used a pressure of 3.8bar, and it was held vertically 22cm from the stage. the stage speed was 40 rpm with a correspondent linear speed of 320 mm/min. the hydrophilic part was made using polymer matrix composite with copper powder as filler. the used copper powder particle size was 325 mesh (0.1%> 63µm, 96.1%<45µm) [25]. the resin of the matrix material is made of bisphenol a-epichlorohydrin polymer (=>60% w/w), and (3(2,3epoxypropoxy) propyl) trimethoxy silane (>= 0.1) [26]. the hardener is made of: isophorone diamine (7 13% w/w), bisphenol a (0.1 1 % w/w), diethylenetriamine (0.1 1 % w/w), and tetraethylenepentamine (0.1 1 % w/w) [27]. an equivalent volume of resin and hardener were used to create the composite polymeric matrix. the overall composite mixture was created with a weight percentage of 25% of the polymer and 75% filler. the composite consisted of 0.125g of resin, 0.125g of hardener, and 0.75g copper powder. the composite component mixed for three minutes and leveled for another one minute. the composite was mixed inside a prepared silicon-based mold. the mold dimensions were 15, 25.4, and 1 mm. the manual mixing was performed with a spatula for three min and the leveling for another minute. the final step for the sample preparation was attaching the coated sheets to the prepared composite; this was done after six minutes from the start of the mixing. later, the samples were detached from the molds after 24 hours. a novel design of hybrid hydrophilic-superhydrophobic surfaces for fog harvesting 155 furthermore, the two additional samples with no hole in the design were prepared, one was coated to become only superhydrophobic, and the other was without coating (to be only hydrophilic). figure 3: the seven cad designs to implement the six hybrid surfaces, hydrophilic, and superhydrophobic samples for the experiments. figure 4: a. the design of the sample as it's attached to the composite. b. the prepared samples with different diameters and pitches 2.2 the experiment's setup the wcr of the samples was tested in a lab environment with fog/mist emulation. a commercial humidifier (levoit model lv600hh) was used for this purpose. the flow velocity was measured as 0.5 ±1 m/s. the mist was generated with an average of 300 ml/h and ejected with an angle of 50 ̊. a sample holder was designed and printed. the sample's distance from the humidifier outlet was 12.5 cm. the average humidity of the sample was measured to be around 90-95%, and the experiments were done at a room temperature of 21±1 ̊c. almusaied and asiabanpour (2021): international journal of engineering materials and manufacture, 6(3), 152-162. 156 a. b. figure 5: a. the schematic of the experiment's settings. b. water collection on the sample 3 results and discussion three types of results obtained for the experiments: • samples' dimensions • samples' wettability • the water collection rate for the samples 3.1 samples' dimensions the dimensions of hybrid surfaces' components were determined using both stereomicroscope and digital microscopy (hirox digital microscope). the diameters of the holes and their pitches were measured for the sheets after printing. while the estimated pitches were close to the design, the diameters were less by different percentages. the designs were modified by adding 200um for each diameter. the new calibrated samples were printed again and measured. furthermore, the calibrated samples were used to fabricate the hybrid surfaces and were finally measured. figure 6: the samples' pitches were measured using a stereomicroscope. the original designs were later modified by adding 200 um for the diameters. this was done due to the limitations of the printer and to make the diameter close to the intended designs. superhydrophobic surface hydrophilic water droplet a novel design of hybrid hydrophilic-superhydrophobic surfaces for fog harvesting 157 figure 7: the samples' diameters were measured using a stereomicroscope. the original designs were later modified by adding 200 um for the diameters. this was done due to the limitations of the printer and to make the diameter close to the intended designs. the overall observation for the dimensions of the printed sheet is higher accuracy of the pitches compared to the diameters of the holes. the thickness of the printed sheets, composite, and coating layers were measured using the digital microscope. a sliding glass was partially covered with scotch tape and coated with the exact coating mechanism, later the tape was removed, and a step was created for the measurement. the total thickness for the sample designed with diameters of 500um and a pitch of 1500um was 787 ± 20um. table 2: the layers thicknesses for the sample designed with diameters of 500um and a pitch of 1500um as measured optically layer thickness uncertainty composite thickness (fig. 8) 654 μm ±11μm blank sheet (fig. 9) 113 μm ±11 μm four passes coating (fig. 10) 20 μm ±13 μm figure 8: the coating was measured using the hirox digital microscope. the coating on the glasses performed with the same conditions as on the sheet. superhydrophobic coated sheet hydrophilic composite almusaied and asiabanpour (2021): international journal of engineering materials and manufacture, 6(3), 152-162. 158 figure 9: the uncoated sheet as measured by the hirox digital microscope figure 10: the composite thickness measured by digital microscope 3.2 samples' wettability the wettability of the samples' component describes the behaviour of the contact between them and the water. the wettability is measured through the contact angle between the interfaces of the air-water and the solid-water at the three phases contact line. multiple contact angles can occur with different local minimum free energy. these contact angles are encapsulated between the advancing and receding angles as they represent the maximum and minimum contact angles for the system [28]. the measurement of the advancing and receding contact angle was obtained using sessile-drop goniometry. di water droplets were placed on the samples with the needle was halfway inside the droplets. quasi-static conditions were created for the measurements by using an automated pump with a slow flow. the pump flow rate used in the experiment was 0.08 ul/sec. the advancing contact angles were calculated as the water was pumped in until the baseline of the droplet started to move. at the same time, the receding angles measured with the water pumped out of the droplet, and the baseline began to shrink [29-30]. table 3: the advancing contact angle (aca) and receding contact angle (rca) were measured using a goniometer. the droplet volume increased and decreased with 0.08ul/sec to obtain quasi-static conditions material aca rca hysteresis hydrophilic sheet 73.4 ± 1.5 50 ± 2 23.4 ± 2.5 hydrophilic composite 72 ± 0.4 29.4 ± 1.1 42.6 ± 1.2 superhydrophobic coated sheet 163.1± 0.5 161.7 ± 0.6 1.4 ± 0.8 a novel design of hybrid hydrophilic-superhydrophobic surfaces for fog harvesting 159 figure 11: a. the aca for the superhydrophobic area. b.the rca for the superhydrophobic area. the measurements obtained using a goniometer and automated water dispenser with a volume rate of 0.08 ul/sec 3.3 the water collection rate for the samples the wcr of the eight samples was attained in the lab using a humidifier to emulate the fog. figure 12: the water collection rate for the samples, including the homogeneous hydrophilic and homogeneous superhydrophobic samples the wcrs for the six hybrid samples are more than that of the untreated hydrophilic sample. this can be explained through the analysis of the collection mechanism. the fog harvesting mechanism can be divided into three steps [3133]. • collecting and capturing the deposited water droplets • migration and accumulation of the droplets • the shedding the first step of fog harvesting is majorly influenced by fog density. the second step started with the captured droplets on the surface beginning to move from the area with low surface free energy into the ones with high surface free energy. the driving force for the movement can be described by the following equation: f1= 𝛾 (cos 𝜃 1 − cos 𝜃 2 ) ------------(1) [34-35]. where f1 is the droplet migration driving force, 𝛾 is the water surface tension of the water, 𝜃1 and 𝜃2 are the contact angles of the hydrophilic and hydrophobic regions, respectively. thus, the higher contrast in wettability will create a more potent migration driving force and faster droplets growth on the hydrophilic regions. the droplets continue to grow on both the hydrophilic and the superhydrophobic regions; they still will be under a pinning capillary force that keeps them attached to the surfaces. the third step: the shedding of the water droplets will start when the force exerted by gravity is more significant than the retention force. the previous condition is described by the furmidge equation: 𝑚𝑔 sin 𝛼 > 𝛾𝑙 (cos 𝜃𝑟 − cos 𝜃𝑎 ) --------(2) [31]. almusaied and asiabanpour (2021): international journal of engineering materials and manufacture, 6(3), 152-162. 160 where m is the mass of the droplet, g is the gravity acceleration, α is the sliding angle, γ is the water tension, 𝑙 is the width of contact of the droplet, 𝜃𝑟 is the receding angle on the hydrophilic region, and 𝜃𝑎 is the advancing angle for the hydrophobic region. the measured low contact angle hysteresis for the superhydrophobic area indicates a cassie-baxter wetting condition. the cassie-baxter wetting condition is associated with minimum contact area between the droplets and the surface, as the air pockets exist underneath the droplets. some of the droplets on the hybrid surfaces were observed not moving to the hydrophilic regions; this might indicate a wetting transition from the cassie-baxter regime into the more pinned wenzel state. in the wenzel state, the surface asperities penetrate the water droplet, and no air pocket exists. the transition happens primarily due to the young-laplace pressure, making the droplet wet the air pockets underneath them. the aforementioned wetting's transition can also explain the water collection behaviour on the superhydrophobic sample. the hydrophilic sample, on the other hand, showed less water collection as the water droplets created bigger pinned droplets which emulated the stagnate film is condensation. in addition to the previous mechanism and affecting factor, additional variables influence the wcr, such as the wind speed, the distance from the source of mist, and the fog droplet size [32]. the droplet kinetic energy, due to the wind, helps the droplets' collection, migration, and shedding. on the other hand, a very small droplet size combined with high wind speed might lead to the loss of the droplets due to evaporation. another factor that might influence the collection is the account of water vapor condensation into water. the previous mechanism assumed the wcr is only associated with fog water droplets, while the high saturation occurring during the experiment might lead to the water vapor phase transition. 4 conclusions • hybrid surfaces for fog harvesting were created successfully using pol-jet 3d printing, hydrophobic coating, and hydrophilic polymeric composite. • the water collection rate of the hybrid surfaces was compared to that of the hydrophilic and superhydrophobic samples. the dimension of the diameter and pitches of the hydrophilic regions in the hybrid surface significantly influence the wcr. • the diameter of the hydrophilic region and the pitches varied to obtain the best wcr. the sample with 582 ± 51 um diameter and 1600 ±75 pitch achieved 57% more water than the untreated hydrophilic surface. • the novel method to create hybrid surfaces is scalable. it can be modifying to any curvature by detaching them from the mold after 30 min and attach them to any other surface. • further studies are needed to fully capitulate the influential factors on the fog harvesting mechanism and the relation among them • the printing accuracy slightly affected the desired dimensions; other options for the manufacturing of the sheet might lead to better results acknowledgement this work was completed with funding from the us department of agriculture (grant # 2016-38422-25540). the authors would like to thank the usda and texas state university for providing funding and access to both infrastructure and laboratories. the sponsors are not responsible for the content and accuracy of this article. the authors declare that there is no conflict of interest regarding the publication of this paper. references 1. the water in you: water and the human body. (2021). retrieved 17 march 2021, from https://www.usgs.gov/special-topic/water-science-school/science/water-you-water-and-human-body?qtscience_center_objects=0#qt-science_center_objects 2. human right to water and sanitation | international decade for action 'water for life' 2005-2015. (2021). retrieved 17 march 2021, from https://www.un.org/waterforlifedecade/human_right_to_water.shtml#:~:text=according%20to%20the%20 world%20health,and%20few%20health%20concerns%20arise. 3. human right to water and sanitation | international decade for action 'water for life' 2005-2015. (2021). retrieved 17 march 2021, from https://www.un.org/waterforlifedecade/human_right_to_water.shtml#:~:text=according%20to%20the%20 world%20health,and%20few%20health%20concerns%20arise. 4. fao. 2020. the state of food and agriculture 2020. overcoming water challenges in agriculture. rome. 5. urbanization | un-water. (2021). retrieved 18 march 2021, from https://www.unwater.org/waterfacts/urbanization/ 6. bhaduri, a., bogárdi, j., leentvaar, j., & marx, s. (2014). the global water system in the anthropocene: challenges for science and governance. springer. a novel design of hybrid hydrophilic-superhydrophobic surfaces for fog harvesting 161 7. wwap (united nations world water assessment programme)/un-water. 2018. the united nations world water development report 2018: nature-based solutions for water. paris, unesco. 8. howard perlman, u. (2017). how much water is there on earth. usgs water science school. water.usgs.gov. retrieved 25 march 2021, from https://water.usgs.gov/edu/earthhowmuch.html 9. chen, z., & zhang, z. (2020). recent progress in beetle-inspired superhydrophilic-superhydrophobic micropatterned water-collection materials. water science and technology. doi: 10.2166/wst.2020.238. 10. rajaram, m., heng, x., oza, m., & luo, c. (2016). enhancement of fog-collection efficiency of a raschel mesh using surface coatings and local geometric changes. colloids and surfaces a: physicochemical and engineering aspects, 508, 218-229. doi: 10.1016/j.colsurfa.2016.08.034 11. lee, a., moon, m., lim, h., kim, w., & kim, h. (2012). water harvest via dewing. langmuir, 28(27), 1018310191. doi: 10.1021/la3013987. 12. sharma, v., sharma, m., kumar, s., & krishnan, v. (2016). investigations on the fog harvesting mechanism of bermuda grass ( cynodon dactylon ). flora, 224, 59-65. doi: 10.1016/j.flora.2016.07.006. 13. zhang, s., huang, j., chen, z., & lai, y. (2016). bioinspired special wettability surfaces: from fundamental research to water harvesting applications. small, 13(3), 1602992. doi: 10.1002/smll.201602992. 14. parker, a., & lawrence, c. (2001). water capture by a desert beetle. nature, 414(6859), 33-34. doi: 10.1038/35102108. 15. nørgaard, t., & dacke, m. (2010). fog-basking behaviour and water collection efficiency in namib desert darkling beetles. frontiers in zoology, 7(1), 23. doi: 10.1186/1742-9994-7-23. 16. mondal, b., mac giolla eain, m., xu, q., egan, v., punch, j., & lyons, a. (2015). design and fabrication of a hybrid superhydrophobic–hydrophilic surface that exhibits stable dropwise condensation. acs applied materials & interfaces, 7(42), 23575-23588. doi: 10.1021/acsami.5b06759. 17. hou, y., yu, m., chen, x., wang, z., & yao, s. (2014). recurrent filmwise and dropwise condensation on a beetle mimetic surface. acs nano, 9(1), 71-81. doi: 10.1021/nn505716b. 18. garrod, r., harris, l., schofield, w., mcgettrick, j., ward, l., teare, d., & badyal, j. (2007). mimicking a stenocara beetle's back for microcondensation using plasmachemical patterned superhydrophobic−superhydrophilic surfaces. langmuir, 23(2), 689-693. doi: 10.1021/la0610856. 19. zhang, l., wu, j., hedhili, m., yang, x., & wang, p. (2015). inkjet printing for direct micropatterning of a superhydrophobic surface: toward biomimetic fog harvesting surfaces. journal of materials chemistry a, 3(6), 2844-2852. doi: 10.1039/c4ta05862c. 20. gürsoy, m. (2020). all-dry patterning method to fabricate hydrophilic/hydrophobic surface for fog harvesting. colloid and polymer science, 298(8), 969-976. doi: 10.1007/s00396-020-04656-x. 21. moazzam, p., tavassoli, h., razmjou, a., warkiani, m., & asadnia, m. (2018). mist harvesting using bioinspired polydopamine coating and microfabrication technology. desalination, 429, 111-118. doi: 10.1016/j.desal.2017.12.023. 22. wang, y., zhang, l., wu, j., hedhili, m., & wang, p. (2015). a facile strategy for the fabrication of a bioinspired hydrophilic–superhydrophobic patterned surface for highly efficient fog-harvesting. journal of materials chemistry a, 3(37), 18963-18969. doi: 10.1039/c5ta04930j. 23. park, j., & kim, s. (2019). three-dimensionally structured flexible fog harvesting surfaces inspired by namib desert beetles. micromachines, 10(3), 201. doi: 10.3390/mi10030201. 24. wong, i., teo, g., neto, c. and thickett, s., 2015. micropatterned surfaces for atmospheric water condensation via controlled radical polymerization and thin film dewetting. acs applied materials & interfaces, 7(38), pp.21562-21570. 25. atomized, c., 2021. buy copper atomized at inoxia ltd. [online] inoxia.co.uk. available at: <https://www.inoxia.co.uk/products/chemicals/elements/copper-atomized> [accessed 19 april 2021]. 26. gorillatough.com. 2021. [online] available at: <https://www.gorillatough.com/wp-content/uploads/gorillaepoxy-resin-3.pdf> [accessed 19 april 2021]. 27. gorillatough.com. 2021. [online] available at: <https://www.gorillatough.com/wp-content/uploads/gorillaepoxy-hardener-sds-update.pdf> [accessed 19 april 2021]. 28. marmur, a., della volpe, c., siboni, s., amirfazli, a., & drelich, j. (2017). contact angles and wettability: towards common and accurate terminology. surface innovations, 5(1), 3-8. doi: 10.1680/jsuin.17.00002. 29. huhtamäki, t., tian, x., korhonen, j., & ras, r. (2018). publisher correction: surface-wetting characterization using contact-angle measurements. nature protocols, 14(7), 2259-2259. doi: 10.1038/s41596-018-0047-0. 30. drelich, j. (2013). guidelines to measurements of reproducible contact angles using a sessile-drop technique. surface innovations, 1(4), 248-254. doi: 10.1680/si.13.00010. 31. dorrer, c., & rühe, j. (2008). mimicking the stenocara beetle-dewetting of drops from a patterned superhydrophobic surface. langmuir, 24(12), 6154-6158. doi: 10.1021/la800226e. 32. tang, x., & guo, z. (2020). biomimetic fog collection and its influencing factors. new journal of chemistry, 44(47), 20495-20519. doi: 10.1039/d0nj04632a. 33. lei, j., & guo, z. (2020). a fog-collecting surface mimicking the namib beetle: its water collection efficiency and influencing factors. nanoscale, 12(13), 6921-6936. doi: 10.1039/c9nr10808d almusaied and asiabanpour (2021): international journal of engineering materials and manufacture, 6(3), 152-162. 162 34. zhu, h., huang, y., lou, x., & xia, f. (2019). beetle-inspired wettable materials: from fabrications to applications. materials today nano, 6, 100034. doi: 10.1016/j.mtnano.2019.100034 35. chaudhury, m., & whitesides, g. (1992). how to make water run uphill. science, 256(5063), 1539-1541. doi: 10.1126/science.256.5063.1539 international journal of engineering materials and manufacture (2022) 7(1) 25-34 https://doi.org/10.26776/ijemm.07.01.2022.03 md. najmul hasan, samsul islam and mohammad zoynal abedin department of mechanical engineering dhaka university of engineering & technology, gazipur gazipur 1707, bangladesh e-mail: abedin.mzoynal@duet.ac.bd reference: hasan, m. n., islam, s. and abedin, m. z. (2022). performance evaluation of textile effluent treatment plant: bangladesh perspective. international journal of engineering materials and manufacture, 7(1), 25-34. performance evaluation of textile effluent treatment plant: bangladesh perspective md. najmul hasan, samsul islam and mohammad zoynal abedin received: 17 september 2021 accepted: 14 december 2021 published: 01 january 2022 publisher: deer hill publications © 2022 the author(s) creative commons: cc by 4.0 abstract the present study was undertaken to evaluate the performance efficiency of an effluent treatment plant (etp) of a textile industry located at tongi, bangladesh with biological treatment (bt) and membrane bio-reactor (mbr) with an average inflow of 300 m3/hr. the effluent samples were collected from the inlet and outlet of the etp on a weekly basis for a 4 weeks’ period and were analysed for key parameters such as colour, temperature, total suspended solids (tss), total dissolved solids (tds), ph, dissolved oxygen (do), biological oxygen demand (bod), and chemical oxygen demand (cod). in this study, it was observed that the colour of the effluent in the inlet was dark blue and after multiple unit treatments of the colour’s final outlet the discharge, water colour was very light purple. the temperature was varied from 32.2⁰c to 34.33⁰c. the tds was varied from 1252.5 mg/l to 1087.5 mg/l and the percentage removal efficiency of tds was varied from 21.47% to 42.7%. the tss was varied from 4 mg/l to 4.5 mg/l and the percentage removal efficiency of tss was varied from 98.48% to 98.21%. the ph value was varied from 6.48 to 7.63. the do value in the inlet was varied from 6.47 mg/l to 6.775 mg/l. the bod was recorded from 12.75 mg/l to 17.75 mg/l and the percentage removal efficiency of bod was varied from 89.92% to 87.24%. the cod was varied from 33.75 mg/l to 34.25 mg/l and the percentage removal efficiency of cod was varied from 91.11% to 90.5%. it is conjectured that the values of the measured parameters are seen to be within the permissible limit as per the standard of the department of environment (doe) of bangladesh. keywords: textile industry, effluent treatment plant, bod, cod, tss, tds, industrial effluent, water quality. nomenclature: abbreviation/symbol meaning tss total suspended solids tds total dissolved solids ph potential of hydrogen do dissolve oxygen bod biological oxygen demand cod chemical oxygen demand ds dissolved solids ss suspended solids doe department of environment mg/l milligrams per litter etp effluent treatment plant c degree celsius ppm parts per million 1 introduction bangladesh is one of the most important textiles and garment exporters countries within the world. the ready-made garment (rmg) sector has become the biggest manufacturing sectors in bangladesh with approximately 4490 apparel manufacturing units registered under the bangladesh garment manufacturers and exporters association (bgmea) in 2008 [1]. amidst differing types of industries, wet processing of textiles, steel, paper, fertilizers, cement, and pharmaceuticals produce an enormous quantity of effluents. but industrial effluent is the most important environmental concerns recently faced by the country. the untreated textile wastewater can cause rapid depletion mailto:abedin.mzoynal@duet.ac.bd performance evaluation of textile effluent treatment plant: bangladesh perspective 26 of dissolved oxygen if it is directly discharged into the surface water sources because of its high bod value. the effluents with high levels of bod and cod values are highly toxic to the biological life. the high alkalinity and traces of chromium which is utilized in dyes adversely affect the aquatic life and also interfere with the biological treatment processes [2]. on average, approximately 200 litters of water are required to supply l kg of textiles. the chance factors are primarily related to the wet processes such as scouring, de-sizing, mercerizing, bleaching, dyeing and finishing. desizing, scouring and bleaching processes produce large quantities of wastewater. these chemicals aren't only poisonous to humans but also found toxic to aquatic life (who, 2002) and that they may lead to food contamination. ammonia is harmful to fish or other aquatic organisms at free (un-ionized) concentration of 10-50 µg/l or higher ph and also the sulphide within the effluent are of environmental concern because they will result in the poor air quality of a region if not properly taken care of; thus becoming threat to human, vegetation, and materials [3]. the large volumes of wastewater generated also contain a good sort of chemicals used throughout processing. these can cause damage if not properly treated before being discharged into the environment [4]. the effluent generated from different sections of a factory must be treated before it is discharged to the environment. various chemicals and physicals means are introduced for this purpose. the untreated wastewater can cause rapid depletion of dissolved oxygen if it is directly discharged into the surface water sources thanks to its high bod value. the effluents with high bod and cod values are highly toxic to the biological life [5]. the effluent treatment plant may be a combination of physicochemical followed by aerobic biological treatment. the plant consisted of the subsequent primary and secondary treatment unit operations: sump well, equalization basin, chemical dosing tank, primary clariflocculator, activated sludge basin, secondary clarifier and sludge drying bed [6]. the quality effluent treatment plants are often analysed by their physicochemical and biological analysis. monitoring of the environmental parameters of the effluent would allow having, at any time, an exact idea on performance evaluation of etp and if necessary, appropriate measures is also undertaken to stop adverse impact on the environment. the efficiency of individual units of effluent treatment plants determines the general performance of the plant and therefore the final effluent quality. the textile industry may be a water-intensive industry that consumes large quantities of water and thus produces an outsized volume of wastewater during its manufacturing steps like dyeing, mercerizing, bleaching, and finish process [7]. characterization of the wastewater of the textile industry are evaluated in terms of temperature, do, tss, tds, ph, bod, cod, for the influent and effluent of the chosen plant. the performance of etp also will be evaluated and the standard of reclaimed wastewater are compared with national standards to see its suitability for reuse and associated environmental impacts. the wastewater generates about 50% of total freshwater consumption. the untreated fibre industry wastewater can cause rapid depletion of do if it is directly discharged into the surface water thanks to higher values of ts, ss, ds, bod and cod [8]. the textile industry is additionally considered to be one in every of the largest threats to the environment. the fabrication operations not only utilize huge quantities of power and water, but they also generate considerable amounts of waste. the textile industry utilizes variety of dyes, chemicals, and other materials to impart the desired qualities to the fabrics. these operations produce a big number of effluents. the standard of effluents is specified they can’t be put to other uses, and that they can create environmental problems if they are disposed of without appropriate treatment. this review paper discusses different textile processing stages, pollution problems related to these stages, and their eco‐friendly alternatives [9]. advanced wastewater treatment technologies such as advanced oxidation process, aerated lagoon, bioreactor, constructed wetland, membrane bioreactor, nano-technology, ionexchange, desalination, and reverse osmosis etc. don't seem to be popular for industrial and municipal wastewater treatment in bangladesh till now. however, the technologically ahead countries are recovering valuable nutrients, elements and metals from wastewater but bangladesh lags behind yet [10]. the effluent generated from different sections of a mill must be treated before it is discharged to the environment. various chemicals and physical means are introduced for this purpose. the effluent treatment plant within the dyeing industry could be a chemical-biological combination process developed [5]. the objective of the present research is to evaluate the performance analysis of textile effluent treatment plant (etp) of tamishna group at tongi, dhaka, bangladesh. figure 1: etp plant with mbr technology used in tamishna group at tongi, dhaka, bangladesh. hasan, islam and abedin (2021): international journal of engineering materials and manufacture, 7(1), 25-34 27 2 experiment1al method the study was applied within the tamishna group at tongi, bangladesh. the information is analysed by comparing the concentration as per the quality method such as collection of primary data, sample collection, selection of sampling locations, determination of physical (colour, temperature, total dissolved solids, total suspended solids and chemical properties (ph, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand). the selection of sampling location is considered by taking inlet water, after mechanical treatment but before equalization tank and taken out let water at the discharge point. we consider sample collection for 4 weeks and 4 samples are from the inlet and outlet (n = 4) and taken 500 ml plastic bottle with throughout clean and washed with water. the physical parameters are colour, temperature, total dissolved solids (tds), total suspended solids (tss) and the chemical parameters are ph, dissolve oxygen (do), biological oxygen demand (bod), chemical oxygen demand (cod). table 1: effluent characteristics from textile industry. process effluent composition nature sizing starch, waxes, carboxymethyl cellulose (cmc), polyvinyl alcohol (pva), wetting agent. high in bod, cod de-sizing starch, cmc, pva, fats, waxes, pectin’s. high in bod, cod, ss, dissolved solids (ds) bleaching sodium hypochlorite, cl2, naoh, h2o2, acids, surfactants, nasio3, sodium phosphate, short cotton fibre. high alkalinity, high ss mercerizing sodium hydroxide, cotton wax high ph, low bod, high ds dyeing dyestuff’s urea, reducing agents, oxidizing agents, acetic acid, detergents, wetting agents. strongly coloured, high bod, ds, low ss, heavy metals printing pastes, urea, starches, gums, oils, binders, acids, thickeners, cross-linkers, reducing agents, alkali. highly coloured, high bod, oily appearance, ss slightly alkaline, low bod table 2: instruments details with test methods. serial parameters unit test instrument brand origin test method instruments picture 1 ph hq40d multimeter hacha u.s.a. usepa electrode method 2 tds/ conductivity mg/l hq40d multimeter hacha u.s.a. usepa direct measurement method1, 2 3 do mg/l hq40d multimeter hacha u.s.a. direct measurement method1 4 temperature °c glass thermo meters g h zeal ltd england direct measurement 5 tss mg/l spectrophotometer hacha u.s.a. photometric method1 6 colour pl-co spectrophotometer hacha u.s.a. platinum-cobalt standard method1, 2, 3 7 cod mg/l spectrophotometer with cod reactor hacha u.s.a. usepa1 reactor digestion method2 8 bod mg/l bod incubator velp scientifica italy respirometric method mg/l bod track ii hacha u.s.a performance evaluation of textile effluent treatment plant: bangladesh perspective 28 2.1 physical parameters for determination of colour, we use the method of platinum-cobalt standard method-1, 2, 3 and the procedures are taken etp inlet and outlet water sample, sample cell 2 pcs (1 no sample cell needs water 10 ml, 2 no sample cell needs sample water 10 ml), start program 120 colour, 455 nm or program 125 colour, 465 nm whether 1 no sample (distilled water cell) to program zero then 2 no sample to push read then result. for determination temperature, we use the method of usepa direct measurement method-1, 2 and the temperature of both inlet and outlet water is measured by multimeter at the quality temperature and ratio. for determination of total dissolved solids (tds), we use the method of usepa direct measurement method-1, 2. dissolved solids consult with any minerals, salts, metals, cations or anions dissolved in water. total dissolved solids (tds) comprise inorganic salts (principally calcium, magnesium, potassium, sodium, bicarbonates, chlorides, and sulphates) and a few small amounts of organic matter that are dissolved in water. it's expressed in mg/l or parts per million (ppm). it's measured directly by multimeter. for determination of total suspended solids (tss), we use the method of photometric method-1 and total suspended solids (tss) are solids in water that may be trapped by a filter. tss can include a good kind of materials, like silt, decaying plant and animal matter, industrial wastes, and sewage. high concentrations of suspended solids can cause many problems for stream health and aquatic life. the foremost accurate method of determining tss is by filtering and weighing a water sample. we collect samples during a clean glass or plastic bottle, then we preserve those samples for later analysis and keep the samples at or below 6 °c (43 °f) for up to 7 days, then let the sample temperature increase to temperature before analysis. we also start program by 630 suspended solids, for information about sample cells, adapters or light shields and blend 500 ml of sample in an exceedingly blender at high speed for exactly two minutes, pour the blended sample into a 600-ml beaker. after that we prepare the sample by stirred the sample and immediately pour 10 ml of the blended sample into a sample cell, prepare the blank by filled a second sample cell with 10 ml of water or deionized water. and we also clean the blank sample cell, insert the blank into the cell holder, push zero. the display shows 0 mg/l tss. swirl the prepared sample to get rid of any gas bubbles and uniformly suspend any residue. after that clean the prepared sample cell and we insert the prepared sample into the cell holder. finally, push read and results show in mg/l tss. 2.2 chemical parameters for chemical parameters, the value of ph was determined. it is defined as the negative log of the proton concentration. ph = − log[h+] (1) the method of usepa electrode procedure was used. at first, we analysed the samples immediately and the samples couldn't be preserved for later. after that we collected samples during a clean glass or plastic bottles, rinsed the probe with deionized water and lastly dried the probe with a lint-free cloth. for the laboratory test, the probe was placed in a beaker that contained the sample. the probe was not allowed to touch the stir bar, bottom or sides of the container. then the air bubbles were removed from under the probe tip, and the sample was stirred at a slow to moderate rate. for the field test, the probe was placed within the sample and the probe moved up and all the way down to remove bubbles from the electrode, then it was guaranteed to put the temperature sensor fully within the sample. the probe was rinsed with deionized water and was dried with a lint-free cloth. for the calculation, ph meters read directly in ph units. 2.3 determination of dissolved oxygen (do) dissolved oxygen (do) is one of the foremost important indicators of water quality and it is essential for the survival of fish and other aquatic organism and also, it is expressed in mg/l or parts per million (ppm). the main consideration with the sample collection is to stop contamination of the sample with atmospheric oxygen. the samples were analysed at the gathering site. for the laboratory test, the probe was placed in a beaker that contained the sample. the probe was not allowed to touch the stir bar, bottom or sides of the container. then the air bubbles were removed from under the probe tip, and the sample was stirred at a slow to moderate rate. for the field test, the probe was put within the sample and moved up and right down to remove bubbles from the probe tip. when the measurement was seen to be stable, the lock icon was shown and when the worth was stable, the mv value was stored and recorded that indicated the temperature value. 2.4 determination of biochemical oxygen demand (bod) bod is the amount of dissolved oxygen (do) needed by aerobic biological organisms during a body of water to interrupt down organic material present in a very given water sample at a particular temperature over a particular fundamental measure. the sample was taken in a suitable bottle where the sample volume for inlet was as 160 ml, outlet as 355 ml. no ph adjustment was performed for inlet, rather for outlet, ph was adjusted at 6-8 by sulfuric acid 0.1n solution. stir bar was taken for every bottle and bod buffer pillow 6 drops were added into the water. then, potassium hydroxide 6 to 7 pcs was added into the bottle tube and set in bod track and set channel of all bottles both for inlet and outlet. the standard value was set as 350 mg/l for inlet and as 70 mg/l for outlet. after 5 days bod was directly measured within the bod track display. hasan, islam and abedin (2021): international journal of engineering materials and manufacture, 7(1), 25-34 29 2.5 determination of chemical oxygen demand (cod) cod is the amount of oxygen required to chemically oxidize the biodegradable and non-biodegradable organic matter and cod often is employed as a measurement of pollutants in wastewater and natural water and also, it is expressed in milligrams per litre (mg/l) which indicates the mass of oxygen consumed per litre of solution. the test method of usepa1 reactor digestion method-2 was used. the procedures are as follows: (apha, 2005) cod vile hr (20-1500 ml) inlet and cod vile lr (3-50 ml) outlet and add 2 ml water sample, set the temperature at 150 and place the sample within the cod reactor. after that, keep the duration at 2 hours and take out the vile and calm down at temperature. at last, the vile was placed into the spectrophotometer and set the black vile program at 0, then click to read button for vile sample report. 3 results and discussions as this effluent treatment plant is shared with multiple wet processing units, there was an excellent possibility to urge the variation within the wastewater quality from time to time. therefore, it had been not feasible to sampling the wastewater in a very single day and find accurate data. the industry has three shifts (8 hours per shift) in production operation. weekly water sampling was performed at the inlet point (after mechanical screening) likewise as at the outlet point and it had been continued for four consecutive weeks. for evaluating the performance of etp, the accurate idea of the composition of effluents is extremely important due to the industrial effluents contain various pollutants which will alter the standard of the receiving water and also the environment at large. industrial effluents contaminate surface water, soil and groundwater thanks to the presence of various pollutants (e.g., soluble solids, suspended solids, organic matter, heavy metals and toxic chemicals). therefore, pre-treatment of discharged wastewater and determining the standard of the effluent is momentous. the study was conducted to characterize the standard of the effluent of inlet and outlet of etp in terms of physical and chemical parameters analysis. the standard values for the waste from industrial units are provided in table 3 according to the environment conservation rules in 1997. 3.1 physical parameters 3.1.1 colour analysis the physical parameters were inspected with various processes. in these parameters, it was seen that the colour of the inlet wastewater was blue and the colour of the outlet discharge water was light purple. the colour of the effluent in inlet was blue because the dye house unit used lot of dyestuffs and chemicals and after multiple unit treatments of the colour’s final outlet the discharge water colour was flash purple. 3.1.2 temperature analysis the normal range of temperature for the inlet is showed in the graph from 39.65±0.31 to 41.9±0.62 and the mean range is showed for the outlet is showed in the graph from 32.2±0.14 to 34.33±46 against the doe standard of 40⁰c which are shown in figure 2. it is seen from the figure 2 that the colour of inlet wastewater colour was navy blue because the dye house unit used lots of dyestuffs and chemicals and after multiple unit treatments of the colour's final outlet, the discharge watercolour was flash purple. within the study, the utmost average of temperature within the inlet was recorded 41.9⁰c in week2 and minimum temperature 39.48⁰c in week4 and on the opposite hand, the utmost mean of temperature within the outlet was recorded 34.33⁰c in week 4 and minimum temperature was 32.2⁰c in week 2. within the four weeks’ data analysis in step with the observed values, the temperature is within the suitable limit of doe standard of 40⁰c. 3.1.3 tds performance the mean value range of inlet is showed in the graph from 1612.5±194 to 1940±146.97 and the mean value range of outlet is showed in the graph from 1087.5±35.94 to 1252.5±9.57 against the doe standard of 2100 mg/l which are shown in figure 3 and figure 4. table 3: standard for waste from industrial units (the environment conservation rules, 1997). parameters unit value found in this study standard limit value temperature ⁰c 34.33 40 tss mg/l 4.5 150 tds mg/l 1252.5 2100 ph mg/l 6.48 to 7.63 6 to 9 do mg/l 6.47 to 6.775 4.5 to 8 bod mg/l 17.75 50 cod mg/l 34.25 200 performance evaluation of textile effluent treatment plant: bangladesh perspective 30 figure 2: temperature performance. figure 3: percentage removal efficiency of tds analysis of 4 weeks. figure 4: tds performance. it is seen from the figure 3 and figure 4 that the maximum mean of tds was recorded in inlet as 1940 mg/l in week 3 and the minimum value was 1612.5 mg/l in week 1. on the other hand, the utmost average of tds in outlet was recorded as 1252.5 mg/l in week 1 and the minimum value is 1087.5 mg/l in week 4. within four weeks’ data analysis in step with the observed values, the tds is within the suitable limit of doe standard of 2100 mg/l. the bottom percentage removal efficiency was recorded as 21.47% in week 1 and the best percentage of removal efficiency was recorded as 42.7% in week 4. 3.1.4 tss analysis the mean value range of inlet is showed in the graph from 243.75±4.79 to 257.5±11.93 and the mean value range of outlet is showed in the graph from 4±0.82 to 4.5±0.31 against the doe standard of 150 mg/l which is shown figure 5 and figure 6. it can be seen from figure 5 and figure 6 that the maximum mean of tss was recorded in inlet as 257 mg/l in week 2 and week 1 and the minimum value is 243.75 mg/l in week 4. on the other hand, the 0 10 20 30 40 50 week 1 week 2 week 3 week 4 t e m p e r a t u r e ( ⁰c ) temperature performance inlet(⁰c) outlet(⁰c) doe std(⁰c) 21.47 27.42 39.82 42.71 0 10 20 30 40 50 week 1 week 2 week 3 week 4 t d s r e m o v a l ( % ) percentage removal efficiency of tds 0 500 1000 1500 2000 2500 week 1 week 2 week 3 week 4 t d s ( m g / l ) tds removal performance inlet(mg/l) outlet(mg/l) doe std(mg/l) hasan, islam and abedin (2021): international journal of engineering materials and manufacture, 7(1), 25-34 31 utmost average of tss in outlet was recorded as 4.5 mg/l in week 3 and the minimum value was 4 mg/l in an exceedingly week within four weeks’ data analysis (figure 6). in step with the observed values the tds is within the suitable limit of doe standard of 150 mg/l. the proportion removal efficiency of tss was consistent throughout the week but the bottom percentage removal efficiency was recorded as 98.21% in week 3 and the very best percentage of removal efficiency was recorded as 98.48% in week 2 (figure 5). 3.2 chemical parameters 3.2.1 ph analysis the mean value range of inlet is showed in the graph from 8.95±0.38 to 9.33 ±0.22 and the mean value range of outlet is showed in the graph from 6.48 ±0.1 to 7.63±0.1 against the doe standard from 6 to 9 which is shown in figure 7. it can be seen from figure 7 that the ph of the raw effluent is incredibly high because the incoming wastewater is extremely alkaline in nature. the bleaching agents employed in the method are the reasons for top alkaline wastewater. the ph correction is finished with the assistance of hcl and brings all the way down to neutral which is favourable ph for biological treatment. the maximum normal value of ph in inlet was recorded as 9.33 in week 4 and the minimum value was 8.95 in week 3. on the other hand, in outlet, the utmost normal value was recorded as 7.63 in week 1 and the minimum value is 6.48 in week 2 within four weeks’ data analysis which are within the suitable limit of doe standard from 6 to 9. the ph correction is completed with the assistance of sulfuric acid and brings right down to neutral which is favourable ph for biological treatment. 3.2.2 do performance the mean value range of inlet is showed in the graph from 0.1±0.08 to 0.58±1.01 and the mean value range of outlet is showed in the graph from 6.775±0.05 to 6.475±0.1 against the doe standard value from 4.5 to 8 mg/l which is shown in figure 8. it can be seen from figure 8 that the maximum normal value of liquidate in the inlet was recorded as 0.2 mg/l in week 4 and the minimum value was 0.1 mg/l in week 2. on the other hand, the utmost average of liquidate in the outlet was recorded as 4, 6.775 mg/l in week 4 and the minimum value is 6.47 mg/l in week 2. within four weeks’ data analysis in line with the observed values, the do value is within the suitable limit of doe standard from 4.5 to 8. figure 5: percentage removal efficiency of tss analysis of 4 weeks. figure 6: tss performance. 98.39 98.48 98.21 98.37 98 98.1 98.2 98.3 98.4 98.5 98.6 week 1 week 2 week 3 week 4 t s s r e m o v a l ( % ) percentage removal efficiency of tss 0 50 100 150 200 250 300 week 1 week 2 week 3 week 4 t s s ( m g / l ) tss performance inlet(mg/l) outlet(mg/l) doe std(mg/l) performance evaluation of textile effluent treatment plant: bangladesh perspective 32 3.2.3 bod performance the mean value range of inlet is showed in the graph from 119±23.42 to 139.25±4.65 and the mean value range of outlet is showed in the graph from 12.75±0.96 to 17.75±4.43 against the doe standard of 50 mg/l shown in figure 9 and figure 10. it can be seen from figure 9 and figure 10 that the maximum mean value of bod within the inlet was recorded as 139.25 mg/l in week 3 and the minimum value was 119 mg/l in week 1. on the other hand, the utmost mean of bod within the outlet was recorded as 17.75 mg/l in week 3 and 12.75 mg/l in week 4 within four weeks’ data analysis (figure 10) which are consistent with the observed values of the bod within the appropriate limit of doe standard of 50 mg/l. the removal efficiency of bod was consistent throughout the week but the bottom percentage removal efficiency of bod was recorded as 87.24% in week 1 and also the highest percentage of removal efficiency was recorded as 89.92% in week 4 within four weeks of knowledge analysis (figure 9). figure 7: ph performance. figure 8: do performance. figure 9: percentage removal efficiency of tss analysis of 4 weeks. 0 2 4 6 8 10 12 week 1 week 2 week 3 week 4 p h ph performance (inlet) (outlet) doe std -2 0 2 4 6 8 10 week 1 week 2 week 3 week 4 d o ( m g / l ) do performance inlet(mg/l) outlet(mg/l) doe std(mg/l) 87.24 87.71 87.32 89.92 85 86 87 88 89 90 91 week 1 week 2 week 3 week 4 b o d r e m o v a l ( % ) percentage removal efficiency of bod hasan, islam and abedin (2021): international journal of engineering materials and manufacture, 7(1), 25-34 33 3.2.4 cod performance the mean value range of inlet is showed in the graph from 357.5±20.62 to 380 ±9.13 and the mean value range of outlet is showed in the graph from 75±3.86 to 34.75±4.0333 against the doe standard 200 mg/l shown in figure 11 and figure 12. it can be seen from figure 11 and figure 12 that the mean maximum value of cod within the inlet was recorded as 380 mg/l in week 4 and the minimum value was 357 mg/l in week 3. on the other hand, the mean maximum value of cod within the outlet was recorded as 34.25 mg/l in week 1 and the minimum value was 33.75 mg/l in week 3 within four weeks’ data analysis (figure 12). in step with the observed values, the cod is within the suitable limit of doe standard of 50 mg/l. the removal efficiency of tss was consistent throughout the week but the bottom percentage removal efficiency of cod was recorded as 90.5% in week 1 and therefore the highest percentage of removal efficiency was recorded as 91.11% in week 4 within four weeks of information analysis (figure 11). figure 10: bod performance. figure 11: percentage removal efficiency of cod analysis of 4 weeks. figure 12: cod performance. 0 50 100 150 200 week 1 week 2 week 3 week 4 b o d ( m g / l ) bod removal performance inlet (mg/l) outlet (mg/l) doe std (mg/l) 90.5 90.53 90.57 91.11 89.9 90.1 90.3 90.5 90.7 90.9 91.1 91.3 91.5 week 1 week 2 week 3 week 4 c o d r e m o v a l ( % ) percentage removal efficiency of cod 0 100 200 300 400 500 week 1 week 2 week 3 week 4 c o d ( m g / l ) cod performance inlet(mg/l) outlet(mg/l) doe std(mg/l) performance evaluation of textile effluent treatment plant: bangladesh perspective 34 4 conclusions the performance analysis of textile effluent treatment plant (etp) of tamishna group at tongi, dhaka, bangladesh is carried out in the present study. the physical parameters of the plant such as colour, temperature, total dissolved solids (tds), total suspended solids (tss) and the chemical parameters such as ph, dissolve oxygen (do), biological oxygen demand (bod), chemical oxygen demand (cod) are measured and anlaysed which are compared with the standard values of doe of bangladesh. the major findings of the present analysis can be written in the following way. 1. the colour of the inlet wastewater is blue and the colour of the outlet discharge water is light purple. the temperature within the inlet was varied from 41.9⁰c to 39.48⁰c and the outlet was 32.2⁰c to 34.33⁰c due to dye used for the yarn. 2. the tds in inlet water was varied from 1940 mg/l 1612.5 mg/l and outlet was 1252.5 mg/l to 1087.5 mg/l. the removal efficiency of tds was varied from 21.47% to 42.7%. in addition, the tss in inlet was varied from 257 mg/l to 243.75 mg/l and outlet was 4 mg/l to 4.5 mg/l and the removal efficiency of tss was varied from 98.48% to 98.21%. 3. the ph of the effluent within the inlet was alkaline in nature (i.e., 9.33) due to the scoring and bleaching agents along with the huge hydrated oxide utilized in the method. the ph correction is completed with the assistance of sulfuric acid and brings right down to neutral which is favourable ph for biological treatment. 4. the do value was varied from 6.47 mg/l to 6.775 mg/l. the bod within the inlet was varied from 119 mg/l to 139.25 mg/l and also the outlet was recorded from 12.75 mg/l to 17.75 mg/l. the removal efficiency of bod was varied from 89.92% to 87.24%. the cod in inlet was varied from 380 mg/l to 357 mg/l and outlet was from 33.75 mg/l to 34.25 mg/l. the percentage removal efficiency of cod was varied from 91.11% to 90.5%. aknowlagdement the authors would like to express their gratitude to the tamishna group at tongi, bangladesh for their cooperation. the authors also thanks to jahangirnagar university, dhaka, bangladesh for the help. references 1. khan, m., ahmed, s., evans, a., & chadwick, m. (2010). methodology for performance analysis of textile effluent treatment plants in bangladesh. chemical engineering research bulletin, vol 13(2), pp 61-66. 2. palamthodi s, patil d & patil y (2011). microbial degradation of textile industrial effluents. african j biotechnology vol 10, pp 12657-12661. 3. r.o. yusuf and j.a. sonibare, (2004). characterization of textile industries’ effluents in kaduna, nigeria and pollution implications. global nest: the int. j. vol 6(3), pp 212-221. 4. desai, p. a. & kore, v. s. (2011). performance evaluation of effluent treatment plant for textile industry in kolhapur of maharastra. universal journal of environmental research and technology, vol1, pp 560-565. 5. hasan, k., mia, m., jahid, m., mueeid, m. and xu, d. (2013). implementation & performance analysis of effluent treatment plant for waste water treatment in the dyeing textile industries. international journal of scientific & engineering research, vol 7(6). 6. singh, a., gautam, r. and sharma, r. (2020). performance evaluation of a common effluent treatment plant (cetp) treating textile wastewaters in india. journal of industrial pollution control, vol 24(2), pp 111-121. 7. assefa, t. and sahu, o. (2016). performance analysis of textile industry wastewater treatment plant with physicochemical characterizations. journal of environmental treatment techniques, vol 4(1), pp 22-30. 8. kumar, u. (2017). performance evaluation of effluent treatment plant of srf limited, malanpur bhind (m.p.). international journal for research in applied science and engineering technology, vol 5(4), pp 1475-1478. 9. madhav, s., ahamad, a., singh, p. and mishra, p. (2018). a review of textile industry: wet processing, environmental impacts, and effluent treatment methods. environmental quality management, vol 27(3), pp 31-41. 10. alam, o., wahid, s., hossain, m. and chakraborty, m. (2017). the performance analysis of effluent treatment plants (etps) of different industries in chittagong city. international journal of sustainable water and environmental systems, vol 9(1), pp 29-40. 11. apha. (2005). standard methods for the examination of water and wastewater. 21st edition. american public health association, washington, d.c. 12. csus. (1993). operation of wastewater treatment plants. volume 2. 4th edition. california state university, sacramento, ca. 13. metcalf & eddy, inc. (2003). wastewater engineering: treatment and reuse. 4th edition. mcgraw-hill, new york, ny. international journal of engineering materials and manufacture (2019) 4(3) 96-106 https://doi.org/10.26776/ijemm.04.03.2019.02 e. sukirman 1 , y. sarwanto 1 , w. ari adi 1 , a. insani 1 and y. f. buys 2 1 centre for science and technology of advance materials-batan puspiptek, serpong 15314, indonesia. e-mail: skm2792@batan.go.id 2 university of malaya, jalan universiti, 50603 kuala lumpur wilayah persekutuan kuala lumpur, malaysia. e-mail: yose@um.edu.my reference: sukirman, e., sarwanto, y., ari adi, w., insani, a., and buys, f. y. (2019). weak ferromagnetic property and electromagnetic waves absorption characteristic of la(1-x)baxmno3. international journal of engineering materials and manufacture, 4(3), 96-106 weak ferromagnetic property and electromagnetic waves absorption characteristic of la(1-x)baxmno3 e. sukirman, y. sarwanto, w. ari adi, a. insani, and y. fachmi buys received: 23 may 2019 accepted: 30 august 2019 published: 27 september 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract the weak ferromagnetic property and the electromagnetic waves absorption characteristic of la(1-x)baxmno3 (lbmo) compounds have been investigated. the samples of lbmo that are lamno3 (s0), la0.9ba0.1mno3 (s1); la0.8ba0.2mno3 (s2); and la0.7ba0.3mno3 (s3) were synthesized using high energy milling (hem) method. samples were characterized by means of xrd (x-ray diffractometer), hrpd (high-resolution powder neutron diffractometer), eds (energy dispersive x-ray spectroscopy, vsm (vibrating sample magnetometer), and vna (vector network analyzer). there is no magnetic ordering of ferromagnetic in s1 and s2 samples due to the ba occupation factors of both less than 0.2. the ba content in the s3 sample is greater than 0.2, hence the ferromagnetic property of the compound is not so visible with the vsm as well as the vna. the absorption characteristics of electromagnetic waves using vna indicated that there is an absorption of em waves in the frequency range between 8-12 ghz with almost the same peak frequency for all four samples at 10.8 ghz with the absorption of around 5 db. the existence of a weak ferromagnetic property can be detected clearly using hrpd. neutron diffraction as a probe can observe the magnetic structure accurately even in a material having a weak ferromagnetic property. keywords: la-manganite, ba-substitution, cystal structure, electromagnetic wave absorber, weak ferromagnetic. 1 introduction generally, the parent compound, lamno3 with perovskite abo3 structure has antiferromagnetic insulator properties in which mn is present in a single oxidation state (mn +3 ). it is found that the stable phase is the antiferromagnetic atype, which corresponds to the ferromagnetic order of the manganese ions in the basal planes (a, b) and antiferromagnetic order of these ions between these planes along the c axis [1]. the conductivity of rare-earth manganese oxides is enhanced to approach that of metal or semiconductor from the insulating state when doped and their colossal magnetoresistance effect (cmr) is remarkable [2]. therefore, they are fascinating to be studied and applied on a large scale due to their unusual electromagnetic properties [3−5]. besides that due to the unusual magnetic and electronic properties of the lamno3 compound, one can develop a very good electromagnetic wave absorbing device [6-8]. luckily, the desired properties of lamno3 can be tuned easily by partial substitution of the trivalent rare-earth element (la 3+ ) with divalent alkaline earth elements, such as ba 2+ forming a new compound of la(1-x)baxmno3 (lbmo). the property as a microwave absorber of this manganite is usually obtained by varying the concentration of ba 2+ element [3]. substitutions at the trivalent rare earth site (a-site) by a divalent alkaline earth metal ion like ca, sr, ba or pb causes part of the mn +3 are oxidized to mn +4 ions and transforms this compound to a ferromagnetic metal [9]. in order, the electric charge of the compound to remain neutral, a number of mn 3+ ions donate some of its electrons to mn 4+ and therefore formed a mixed valence system of [𝑳𝒂(𝟏−𝒙) 𝟑+ 𝑩𝒂𝒙 𝟐+][𝑴𝒏(𝟏−𝒚) 𝟑+ 𝑴𝒏𝒚 𝟒+]𝑶𝟑 𝟐−. the ferromagnetic behaviour occurred due to magnetic interactions between mn 3+ and mn 4+ ions through the doubleexchange mechanism [10]. sukirman et al., (2019): international journal of engineering materials and manufacture, 4(3), 96-106 97 the previous studies [11] showed that a strong ferromagnetism of lbmo compound occurred at x ≈ 0.2, and at x > 0.2 the properties of ferromagnetic materials become weak, while at x < 0.2 the material becomes antiferromagnetic at room temperature. the purpose of this research is to determine the crystal structure, and to observe a weak ferromagnetic property of magnetic material in relation with the electromagnetic waves absorption characteristic of la(1-x) baxmno3 (lbmo) compounds. it will be carried out using the neutron diffraction method, under the assumption that it could not be done by any other method. no studies have ever been done so far to prove the problem. in this study, the lbmo samples were synthesized by solid-state reaction method using high energy milling (hem) process. 2 methodology the samples were prepared by using solidstate reaction method to the raw materials of la2o3, baco3, and mno2, where the purity of la2o3 raw material is 99.5 % from local products and the remaining two raw materials have more than 99.9 % purity from merck products. the solid reaction in this research was conducted through high energy milling (hem) process with the same procedure as before [12]. subsequently, the precursors were sintered at 1200c for 5 hours at a heating rate of around 49c/min and the cooling was carried out naturally to room temperature in the furnace. it was synthesized four kinds of samples of la1-xbaxmno3 that are lamno3 (s0), la0.9ba0.1mno3 (s1), la0.8ba0.2mno3 (s2), and la0.7ba0.3mno3 (s3). phase characterization was then performed with x-ray diffractometer (xrd), type of pw1710 philips with cooper anode tube, = 1.5406 å, the data were collected in the scattering angular range of 10 o up to 100 o in the interval of 0.02 o at room temperature. the phase was also characterized using high-resolution powder neutron diffractometer (hrpd) with =1.8216 å. the sample was loaded into a cylindrical vanadium holder. the data was collected in the scattering angular range of 2.5 o up to 157 o in the interval of 0.05 o at room temperature. the xrd data were analysed with the help of general structure analysis system (gsas) and the neutron diffraction data was refined using the fullproof software. the elementary analysis was performed using scanning electron microscope (sem) and energy dispersive x-ray spectroscopy (eds) of jeol instrument. the electromagnetic waves absorption characteristics of the samples were analysed by using vector network analyser (vna) of advantest r3770 types with the frequency range of 300 khz 20 ghz. the magnetic properties of materials were characterized using vibrating sample magnetometer (vsm), oxford type 1.2 hin method. measurement of magnetic properties of materials was made in an applied magnetic field to a maximum value of 1 tesla. vsm measurements were carried out at room temperature. measurements, xrd, hrpd, vsm and sem / eds were performed at the centre for advanced materials science and technology (pstbm), batan, puspiptek, setu, tangerang selatan. while the measurements of vna were done at the centre for electronic research and telecommunications (ppet), lipi, bandung. 3 results and discussions the rietveld analysis based on the x-ray diffraction data using gsas software from the lamno3, la0.9ba0.1mno3, la0.8ba0.2mno3, and la0.7ba0.3mno3. samples were showed in figure 1(s0), 1(s1), 1(s2) and 1(s3), respectively. the diffraction pattern of s0 exhibited a single phase diffraction profile within the limits of accuracy of the tool. the dots are the observed intensity, the solid line was the calculated intensity, and the difference pattern was shown at the bottom of the chart. the s0 sample crystallizes into the space group: i12/a1, with 2 = 1.3 and the lattice parameters: a = 7.7839(5) å, b = 5.5288(4) å, c = 5.4781(3) å,  = 90˚,  = 90.746(2)˚,  = 90.0˚ and volume, v = 235.73(4) å 3 . the coordinates of the atomic fractions were shown in table 1. the smoothing on the occupancy factor of oxygen atoms caused their value to be greater than 1.0. according to previous research [11], the s0 sample should display the properties as a paramagnetic material. this will be proved by measurement using vsm. the diffraction pattern of s1 sample which was the result of analysis by rietveld method was shown in figure 1(s1). the s1 samples also showed a single phase diffraction pattern within the limits of accuracy of the tool. it was obtained a better fitting result with 2 = 1.3. the s1 sample crystallized also into the space group: i12/a1 in accordance with the results of previous research [11], the lattice parameters: a = 7.8142(9) å, b = 5.5462(6) å, c = 5.4993(6) å,  = 90˚,  = 90.593(5)◦,  = 90◦ and volume, v = 238.33(7) å3. the atomic fraction coordinates (xj, yj, zj), and the atomic occupancy factor (gj) of s1 sample was indicated in table 2. the mole fraction of la and ba that were 0.86, and 0.105, respectively, correspond to the weighed mole fraction on the synthesis that was 0.9 and 0.1, respectively. the occupation factors of mn, o(1) and o(2) were not refined, because the smoothing caused their value to be greater than 1.0. table 1. the coordinates of atomic fractions (xj, yj, zj), and atomic occupancy factor (gj) of s0 sample. atom gj xj yj zj la 0.810(1) 0.25 0.5066(6) 0.0 mn 0.85(2) 0.0 0.0 0.0 o(1) 1.0 0.25 0.0 0.0 o(2) 1.0 -0.013(2) 0.198(3) 0.292(4) weak ferromagnetic property and electromagnetic waves absorption characteristic of la(1-x)baxmno3 98 figure 1. the x-ray diffraction pattern of lamno3 (s0), la0.9ba0.1mno3 (s1), la0.8ba0.2mno3 (s2), and la0.7ba0.3mno3 (s3). based on the results of previous research [11], the s1 sample should display the properties as an antiferromagnetic or a paramagnetic instead of ferromagnetic material due to the occupation factor of ba was smaller than 0.2. this will be proved by measurement using vsm. the pattern of diffraction after analysis by rietveld method of s2 sample was showed in figure 1(s2). it appeared on the figure that the sample displayed a single phase diffraction pattern to the sukirman et al., (2019): international journal of engineering materials and manufacture, 4(3), 96-106 99 extent of the accuracy of the tool. the s2 sample crystallized into the space group: i12/c1 in accordance with the results of previous research [11], with the goodness of fitting, 2 = 1.2, the lattice parameters: a = 5.5118(3) å, b = 5.5401(4) å, c = 7.8244(4) å,  = 90◦,  = 90.447(6)◦,  = 90◦ and volume, v = 238.92(1)å3. the atomic fraction coordinates (xj, yj, zj), and the atomic occupancy factor (gj) of s2 sample were indicated in table 3. the occupation factor of oxygens was not refined, because the smoothing caused their value to be greater than 1.0. the atomic fraction coordinates of o(2) were not refined, because when those parameters were smoothed caused the chisquare enlarged. it appeared in table 3 that the s2 lacked la and ba atoms in its unit cell that were 0.65 and 0.17, respectively. the mole fraction of la and ba atoms did not correspond to the weighed mole fraction on the synthesis that was 0.8 and 0.2, respectively. the previous studies [11] showed that a strong ferromagnetism of lbmo compound occurred when the ba occupation factor of x ≈ 0.2, and at x < 0.2 the material becomes antiferromagnetic. thus, s2 sample should also display the properties as an antiferromagnetic or a paramagnetic material instead of ferromagnetic one due to the occupation factor of ba 2+ ion was smaller than 0.2. this will be proved by measurement using vsm. the diffraction pattern after being analysis by the rietveld method of s3 sample was shown in figure 1(s3). it appeared on the figure that there was a peak of foreign phase at 2 ≈ 36˚, where this peak was marked with symbol . based on xrd data, the presence of this foreign phase cannot be analysed, possibly because the amount is smaller than the xrd detection limit. table 4 was the coordinates of atomic fractions (xj, yj, zj), and atomic occupantion factor (gj) of s3 sample. it appeared in this table that the occupation factor (gj) of la and ba atoms in its unit cell ware 0.61 and 0.22, respectively. thus, the s3 sample should displays a weak ferromagnetic property due to gj of ba 2+ ion was greater than 0.2, this will be proved later. the s3 sample crystallized into the space group: r-3c in accordance with the results of previous research [13], with the goodness of fitting, 2 = 1.6 and the lattice parameters: a = b = 5.5301(7) å, c = 13.532(3) å,  =  = 90 ˚ ,  = 120˚, volume, v = 358.41(9) å3. the occupation factor of oxygen was not refined, because the smoothing caused its value to be greater than 1.0. table 2. the coordinates of atomic fractions (xj, yj, zj), and atomic occupancy factor (gj) of s1 sample. atom gj xj yj zj la 0.86(1) 0.25 0.502(1) 0.0 ba 0.105(4) 0.25 0.502(1) 0.0 mn 1.0 0.0 0.0 0.0 o(1) 1.0 0.25 0.0 0.0 o(2) 1.0 -0.017(4) 0.204(4) 0.281(5) table 3. the coordinates of atomic fractions (xj, yj, zj), and atomic occupancy factor (gj) of s2 sample. atom gj xj yj zj la 0.65(1) 0.0 0.499(2) 0.75 ba 0.17(3) 0.0 0.499(2) 0.75 mn 0.853(9) 0.0 0.0 0.0 o(1) 1.0 0.0 0.056(3) 0.25 o(2) 1.0 0.251 0.249 -0.03 table 4. the coordinates of atomic fractions (xj, yj, zj), and atomic occupancy factor (gj) of s3 sample. atom gj xj yj zj la 0.61(1) 0.0 0.0 0.25 ba 0.22(1) 0.0 0.0 0.25 mn 0.92(2) 0.0 0.0 0.0 o 1.0 0.480(6) 0.0 0.25 figure 2 showed the eds spectrum of s0, s1, s2, and s3. the four samples showed an identical eds spectrum. table 5 was the mass fraction of the elements in s0, s1, s2, and s3 samples which were based on the number of counts each peak of the eds spectrum. then the mass fraction of ba elements in s1, s2 and s3 were then converted into the mole fraction of ba elements, the result was showed in table 6. it appeared in table 6 that the mole fraction of ba elements in s1 and s2 showed by eds data in accordance to data of xrd and also in accordance to the one on weighing, that was 0.1 and 0.2, respectively. this means that on weak ferromagnetic property and electromagnetic waves absorption characteristic of la(1-x)baxmno3 100 both samples, the ba atoms have entered into the unit cell of lamno3.the mole fraction of the xrd data is the mole fraction per unit cell, whereas the mole fraction of the eds data is the one of the element present in the sample. the mole fraction of the ba element in s3 showed by eds data was in accordance with the one on weighing, i.e., 0.3, but was incompatible with xrd data, i.e., 0.2. it was concluded that there was about 0.1 mole of ba elements not entering into the unit cell of lamno3, but forming a new phase. a foreign peak on figure 1 (s3) appearing at 2 ≈ 36˚ was assumed to belong to the new phase formed by ba elements. table 5. the mass fraction of o, mn, ba and la elements in s0, s1, s2, and s3 samples. energy mass fraction (%) element (kev) s0 s1 s2 s3 o 0.525 18.68 0.09 17.88 0.07 22.23 0.06 18.94 0.07 mn 5.894 21.72 0.25 23.65 0.19 19.76 0.18 20.94 0.21 ba 4.464 5.67 0.25 10.06 0.23 17.16 0.27 la 4.648 59.60 0.35 52.80 0.29 47.95 0.27 42.96 0.31 figure 2. the eds spectrum of lamno3 (s0), la0.9ba0.1mno3 (s1), la0.8ba0.2mno3 (s2), and la0.7ba0.3mno3 (s3). sukirman et al., (2019): international journal of engineering materials and manufacture, 4(3), 96-106 101 table 6. the mole fraction of ba element in s1, s2, and s3 samples result from the conversion of its mass fraction. mole fraction of ba element. sample weighing xrd eds s1 0.1 0.105(4) 0.098(2) s2 0.2 0.17(3) 0.170(2) s3 0.3 0.22(1) 0.283(2) figure 3. the microwave absorbing characteristics of the s0, s1, s2 and s3 samples in the range of 2-12 ghz. the interaction of the ceramics with electromagnetic waves characterized by using an hp8720b vector network analyser in the frequency range of 2-12 ghz was shown in figure 3. the results revealed that the electromagnetic wave absorption characteristics of s0, s1, s2, and s3 were almost the same, i.e., showing the same reflection loss peaks of around -5 db at a frequency of 10.8 ghz. the microwave absorption primarily resulted from magnetic losses caused by magnetization relaxation, domain wall resonance, and natural resonance [14]. this means that all four samples have the same magnetic properties, i.e., as an antiferromagnetic or a paramagnetic materials, because they do not display significant reflection loss, where the previous research [11] showed only manganite with the magnetic ordering of ferromagnetic has the best ferromagnetic properties and therefore display the best characteristic in absorbing an electromagnetic wave. the curves showing the relation between magnetization, m to magnetic field, h, commonly called magnetization curves, for the four samples were shown in figure 4. it was exhibited that s0, s1, and s2 samples displayed a typical pattern for the antiferromagnetic materials, i.e., displaying the linear curve of m vs h. while the m vs. h curve of s3 does not perfectly display a straight line, but slightly curved to form an incomplete s letter. this is in accordance with the results of previous studies [11] which showed that the lbmo compounds, whose the ba occupation factors of gj less than, or greater than 0.2 were antiferromagnetic, or weak ferromagnetic materials, respectively. the presence of a paramagnetic, antiferromagnetic or ferromagnetic phase in lbmo samples was then investigated by neutron diffraction technique using the rietveld analytical methods with the help of fullfrof software. based on the xrd data, the three samples of s0, s1, and s2 have the monoclinic crystal structure, while s3 sample crystallized with hexagonal structure. the analysis of neutron diffraction data, therefore, was performed on s0 only because the three samples are identical. analysis of neutron diffraction data was also carried out on s3 with a purpose besides to confirm the presence of antiferromagnetic or weak ferromagnetic phases also to confirm the presence of foreign phase. first, it was carried out the analysis of nuclear structure with input parameters equal to the input parameters in xrd data analysis using gsas software. the results show that all of the diffraction peaks coincide with the calculation results based on the nuclear peaks (figure 5). this means there are no additional peaks due to scattering from the magnetic phase. so the magnetic structure would have a propagation vector k = (0,0,0). as the propagation vector is k = (0,0,0), the magnetic unit cell is identical to the nuclear cell. weak ferromagnetic property and electromagnetic waves absorption characteristic of la(1-x)baxmno3 102 next, the basirreps program was employed to determine the basis vectors of the irreducible representations (irreps) of the propagation vector group (gk). with the help of this program one can determine the appropriate magnetic symmetry and the magnetic rotation vectors. the output of the calculation for the basic functions of irreps corresponding to the experimental magnetic structure of lamno3 with space group: i12/a1 are a basic function of irreps (1) for antiferromagnetic structures (table 7) and irreps (3) for ferromagnetic structures (table 8). figure 4. the curve for magnetization, m to magnetic field, h from sample lamno3 (s0), la0.9ba0.1mno3 (s1), la0.8ba0.2mno3 (s2), and la0.7ba0.3mno3 (s3). figure 5. neutron diffraction patterns of lamno3 (s0), the rietveld analysis results based on the nuclear phase only without involving magnetic phase, with 2 = 1.9 table 7. basis functions of representation irrep (1) of lamno3, space group: i12/a1, magnetic symmetry (symm), magnetic rotation vector (sk), fractional coordinates (xj, yj, zj) of mn(1), and mn(2) atoms. atoms mn(1) mn(2) (xj, yj, zj) (0.0, 0.0, 0.0) (0.5, 0.0, 0.0) symm (x, y, z) (-x+1/2, y, -z) sk (u, v, w) (-u, v, -w) sukirman et al., (2019): international journal of engineering materials and manufacture, 4(3), 96-106 103 thus, analysis of the magnetic structure on lamno3 was carried out by trial and error, first input the data in table 7 followed by the data in table 8 to determine which data will give the smallest 2. the chi-square of the neutron diffraction patterns of s0 using the irreps(1) and irreps(3) are 1.8 and 2.6, respectively. thus, s0 has a magnetic ordering of antiferromagnetic, where the lattice of magnetic ions in the crystal breaks up into two sublattices along the a-axis having magnetic moments,  = 1.7(5) b in opposite directions (figure 6). this result is in agreement with vsm data and in accord with the previous research indicated by priyo sardjono et. al. [11]. figure 7 is the neutron diffraction patterns of s0 based on two phases, namely the nuclear-, and magnetic phase using basis functions of irreps(1). the s0 sample crystallizes into single phase of lamno3, space group: i12/a1, and the lattice parameters: a = 7.8217(7) å, b = 5.5458(5) å, c = 5.5230(6) å,  =  = 90°, and  = 90.217(7)°. the vertical short lines closest to the horizontal axis indicate the position of the peaks of nuclear scattering, while the vertical short lines below them are the position of the peaks of the magnetic scattering. table 9 was the coordinate of atomic fractions (xj, yj, zj), and atomic occupancy factors (gj) of lamno3 based on the neutron diffraction experiment. table 8. basis functions of representation irrep (3) of lamno3, space group: i12/a1, magnetic symmetry (symm), magnetic rotation vector (sk), fractional coordinates (xj, yj, zj) of mn(1), and mn(2) atoms. atoms mn(1) mn(2) (xj, yj, zj) (0.0, 0.0, 0.0) (0.5, 0.0, 0.0) symm (x, y, z) (-x+1/2, y, -z) sk (u, v, w) (u, -v, w) figure 6. the antiferromagnetic structure of lamno3. figure 7. neutron diffraction patterns of lamno3 (s0), the rietveld analysis results based on the nuclearand magnetic phase using basis functions of irreps (1), with 2 = 1.8. weak ferromagnetic property and electromagnetic waves absorption characteristic of la(1-x)baxmno3 104 table 9. the coordinates of atomic fractions (xj, yj, zj), and atomic occupancy factor (gj) of s0 sample based on neutron diffraction data. atom gj xj yj zj la 0.4(7) 0.25 0.509(2) 0.0 mn 0.6(7) 0.0 0.0 0.0 o(1) 0.2(4) 0.25 0.0 0.0 o(2) 1.0 0.0 0.220(1) 0.267(2) table 10. basis functions of representation irrep (1) of lamno3, space group: r-3c, magnetic symmetry (symm), magnetic rotation vector (sk), fractional coordinates (xj, yj, zj) of mn(1), and mn(2) atoms. atoms mn(1) mn(2) (xj, yj, zj) (0.0, 0.0, 0.0) (0.0, 0.0, 0.5) symm (x, y, z) (y, x, -z+1/2) sk (0, 0, u) (0, 0, -u) table 11. basis functions of representation irrep (3) of lamno3, space group: r-3c, magnetic symmetry (symm), magnetic rotation vector (sk), fractional coordinates (xj, yj, zj) of mn(1), and mn(2) atoms. atoms mn(1) mn(2) (xj, yj, zj) (0.0, 0.0, 0.0) (0.0, 0.0, 0.5) symm (x, y, z) (y, x, -z+1/2) sk (0, 0, u) (0, 0, u) (a) (b) figure 10. the antiferromagnetic structure (a), and ferromagnetic structure (b) of ba-doped lamno3 (s3). furthermore, magnetic structural analysis of s3 was done as for s0 above. the output of the calculation for the basis functions of irreps corresponding to the experimental magnetic structure of lamno3 with space group: r-3c are basis functions of irreps(1) for antiferromagnetic structures (table 10) and irreps(3) for ferromagnetic structures (table 11). the result of observation by means of match software of s3 shows the existence of a new phase of bala2o4. this x-ray diffraction data of the bala2o4 phase could not be analyzed by gsas software, presumably due to its small content. the presence of bala2o4 phase was then observed by hrpd together with the nuclear and magnetic phases. analysis of the magnetic structure on s3 was carried out with the input parameters of table 10 and table 11 simultaneously. this step was carried out because in s3 other than the nuclear phase of lbmo and bala2o4 phase, it is also assumed that there are two magnetic phases, namely antiferromagneticand ferromagnetic phase. the analysis of neutron diffraction data using the rieveld method utilizing fullprof software shows that s3 has two magnetic phases, namely the ferromagnetic and antiferromagnetic phases with the chi-square of the neutron diffraction pattern of s3 is 1.7. the sample of s3 has magnetic ordering of antiferromagnetic and ferromagnetic with the magnetic moment,  = 1.9(2) b (figure 10). the vsm data reveals that the m vs. h curve of s3 does not perfectly display a straight line, but slightly curved to form an incomplete s letter. this means that s3 is not a pure antiferromagnetic material. this material imperfection is apparently still detected by neutron diffraction methode as a material that has a composition of atoms such as sukirman et al., (2019): international journal of engineering materials and manufacture, 4(3), 96-106 105 ferromagnetic order, although weak. this result is in agreement with the results of previous research indicated by priyo sardjono et. al [11] and sukirman et al [15]. figure 11 is the neutron diffraction patterns of s3 based on four phases, namely the nuclear-, antiferromagnetic-, ferromagnetic-, and bala2o4 phase after being analyzed with fullprof software with the goodness of fitting, 2 = 1.7 and the coordinates of the atomic fractions was showed on table 12. rows of the vertical short lines closest to the horizontal axis indicate the position of the peaks of nuclear scattering, while the vertical short lines below them are the position of the peaks of the magnetic scattering, and the third row below is the peak positions of bala2o4 phase. the atomic occupancy factors (gj) on table 12 corresponded to the one on table 4 which showed that the mole fraction of la and ba atoms in the unit cell of the lbmo compound were each smaller than their value when weighed at the time of the synthesis. this was an evidence that some of the atoms of ba and la did not enter into the unit cell of the compound, but form a new compound, i.e., bala2o4, space group: pnam (no. 62), lattice parameters: a = 10.621(2) å, b = 12.466(3) å, c = 3.7191(6) å,  =  =  = 90˚. table 13 were the coordinates of atomic fraction (xj, yj, zj), and atomic occupancy factors (gj) of bala2o4 phase based on neutron diffraction data. it can be concluded that with the support of neutron diffraction data, the reflection loss versus frequency curve (figure 3) and magnetization versus magnetic field curves (figure 4) are both corresponding. figure 11. neutron diffraction patterns of s3, rietveld analysis results based on the nuclearand magnetic phase using basis functions of irreps(3), with 2 = 1.7. table 12. the coordinates of atomic fractions (xj, yj, zj), and atomic occupancy factor (gj) of s3 sample based on neutron diffraction data. atom gj xj yj zj la 0.6(1) 0.0 0.0 0.25 ba 0.23(1) 0.0 0.0 0.25 mn 0.6(2) 0.0 0.0 0.0 o 1.0 0.4731(6) 0.0 0.25 table 13. the coordinates of atomic fractions (xj, yj, zj), and atomic occupancy factor (gj) of bala2o4 phase based on neutron diffraction data. atom gj xj yj zj ba 0.164 0.220(3) 0.660(2) 0.25 la(1) 0.147 0.04(1) 0.44(1) 0.25 la(2) 0.367 0.651(7) 0.584(6) 0.25 o(1) 0.828 0.243(4) 0.253(5) 0.25 o(2) 0.636 0.414(7) 0.032(5) 0.25 o(3) 0.597 0.547(6) 0.764(5) 0.25 o(4) 0.593 0.022(6) 0.123(4) 0.25 weak ferromagnetic property and electromagnetic waves absorption characteristic of la(1-x)baxmno3 106 4 conclusions in this study, the la(1-x)baxmno3 (lbmo) sample’s magnetic ordering dependence on the barium mole fraction has been verified by way of experimental investigation and analysis on its weak ferromagnetic property and its electromagnetic wave absorption characteristic. if the mole fraction of ba in lbmo is smaller than 0.2, the sample is classified as an antiferromagnetics, on the other hand if the mole fraction of ba is greater than 0.2 the material is then classified as having a weak ferromagnetic property. experimental evidence of the formation of weak ferromagnetic property of the lbmo in its unit cell could readily be obtained by using the neutron diffraction technique. however, in the frequency range between 8-12 ghz, the electromagnetic waves absorption of both antiferromagnetic and weak ferromagnetic compounds occurs at around 10.8 ghz with the absorption of around 5 db. the mole fraction of barium has also been found to affect the lbmo phase formation, the magnetic properties, and the electromagnetic waves absorption characteristics of lbmo. acknowledgement the authors thank the management of the center for science and technology of advanced materials, which has provided the research facility. to colleagues in pstbm especially dr. aziz khan jahya, thanks for their kind help. references 1. naji, s., benyoussef, a., el kenz, a., ez-zahraouy, h., loulidi, m. (2012). monte carlo study of phase transitions and magnetic properties of lamno3: heisenberg model. physica, a391, 3885-3894. 2. maria, b., takaki, m., mohammad, s., ho-kwang, m., lorenzo, m., paolo, p., sashi, s., and viktor, v.s. (2015). origin of colossal magnetoresistance in lamno3 manganite. proc. national acad sci usa, 112 (35), 10869– 10872. 3. chul-min, h., min-sook, l., seong-cho, y., kyeongsup, k., jaeyeong, k., and bo wha, l. (2010). magnetocaloric effect of perovskite manganites of la0.8a0.2mno3 (a = ca, sr, ba). journal of the korean physical society, 57(6), 1893-1896. 4. ivan, m., proloy, t.d., max, d., james, g.s., miguel, a.u-l., saikat, d., chennan, w., matthias, r., and christian, b. (2014). influence of la and mn vacancies on the electronic and magnetic properties of lamno3 thin films grown by pulsed laser deposition. physical review, b 89, 174422-1 ̶ 174422-2. 5. korotana, r., mallia, g., gercsi, z., and harrison, n.m. (2013). a hybrid-exchange density functional study of ca-doped lamno3. journal of applied physics, 113, 17a910-1 ̶ 17a910-3. 6. yulan, c., jianming, d., xuebin, z., dajun, w., yuping, s. (2010). preparation, magnetic and microwave absorption properties of la0.5sr0.5mno3/la(oh)3 composites. materials research bulletin, 45, 663–667. 7. kalmykova, t.v., tarapov, s.i., neduch, s.v., krivoruchko, v.n., danilenko, i.a., burchovetckii, v.v., gurtovoj, g.g. peculiarities of electromagnetic waves absorption in polymer magnetic nanocomposites (la,sr)mno3. (2012). functional materials, 19(4), 486-492. 8. wael saad mohamed, a. (2014). optical study of novel perovskitic oxides, with focus on their lattice and electronic properties. ph.d. thesis, sapienza, university of rome, p. 27. 9. vasilii, z. (2010). magnetic and transport properties of lamno3+, la1-xcaxmno3 la1-xcaxmn1-yfeyo3 and la1xsrxmn1-yfeyo3. ph.d thesis, lappeenranta university of technology, lappeenranta, finland, p. 17. 10. alejandra juliette baena, v. (2014). the role of interfaces in heterostructures: strained manganites and silicon for quantum computing. ph.d thesis, facultad de ciencias fisicas, universidad complutense de madrid, madrid, p. 34. 11. priyo, s., and wisnu, a.a. (2013). structural, magnetic and electrical properties of la1-xbaxmno3 (x = 0 – 0.7) for absorber electromagnetic wave. j. basic. appl. sci. res., 3(7), 230-234. 12. sukirman, e., wisnu, a.a., and yustinus, p. (2012). crystal structure and magnetoresistance of la0.7ca0.3mno3 perovskite at room temperature. indonesian journal of nuclear science and technology, 13(2), 61-72. 13. asma, k., saadat, a.s., affia, a. (2013). synthesis and characterization of alkaline-earth metal (ca, sr, and ba) doped nanodimensional lamno3 rare-earth manganites. chin. phys. lett., 30(7), 077501-1– 077501-4. 14. xianguo, l., niandu, w., pingping, z., nannan, b., siu wing, o., caiyun, c., yuping, s. (2015). large scale synthesis of superparamagnetic face-centered cubic co/c nanocapsules by a facile hydrothermal method and their microwave absorbing properties. materials research, 18(4), 756-762. 15. sukirman, e., wisnu, a.a., andon, i., herry, m., teguh y.s. panca, p., aziz khan, j., dani, g. (2017). neutron diffraction studies of the la1-xbaxmno3 magnetic oxide. presented in national seminar on nuclear technology empowerment, national nuclear energy agency, november 21-22, p. 347, puspiptek serpong, indonesia. https://www.ncbi.nlm.nih.gov/pubmed/?term=baldini%20m%5bauthor%5d&cauthor=true&cauthor_uid=26272923 https://www.ncbi.nlm.nih.gov/pubmed/?term=muramatsu%20t%5bauthor%5d&cauthor=true&cauthor_uid=26272923 https://www.ncbi.nlm.nih.gov/pubmed/?term=sherafati%20m%5bauthor%5d&cauthor=true&cauthor_uid=26272923 https://www.ncbi.nlm.nih.gov/pubmed/?term=mao%20hk%5bauthor%5d&cauthor=true&cauthor_uid=26272923 https://www.ncbi.nlm.nih.gov/pubmed/?term=malavasi%20l%5bauthor%5d&cauthor=true&cauthor_uid=26272923 https://www.ncbi.nlm.nih.gov/pubmed/?term=postorino%20p%5bauthor%5d&cauthor=true&cauthor_uid=26272923 https://www.ncbi.nlm.nih.gov/pubmed/?term=satpathy%20s%5bauthor%5d&cauthor=true&cauthor_uid=26272923 https://www.ncbi.nlm.nih.gov/pubmed/?term=struzhkin%20vv%5bauthor%5d&cauthor=true&cauthor_uid=26272923 https://www.ncbi.nlm.nih.gov/pmc/articles/pmc4568232/ international journal of engineering materials and manufacture (2016) 1(1) 3-10 https://doi.org/10.26776/ijemm.01.01.2016.02 a. banu and m. y. ali department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: mmyali@iium.edu.my reference: banu, a. and ali, m. y. (2016). electrical discharge machining: a review. international journal of engineering materials and manufacture, 1(1), 3-10. electrical discharge machining (edm): a review asfana banu and mohammad yeakub ali received: 16 july 2016 accepted: 31 july 2016 published: 05 september 2016 publisher: deer hill publications © 2016 the author(s) creative commons: cc by 4.0 abstract electro discharge machining (edm) process is a non-conventional and non-contact machining operation which is used in industry for high precision products. edm is known for machining hard and brittle conductive materials since it can melt any electrically conductive material regardless of its hardness. the workpiece machined by edm depends on thermal conductivity, electrical resistivity, and melting points of the materials. the tool and the workpiece are adequately both immersed in a dielectric medium, such as, kerosene, deionised water or any other suitable fluid. this paper provides an important review on different types of edm operations. a brief discussion is also done on the machining responses and mathematical modelling. keywords: wedm, micro-edm, non-conductive ceramics, dry edm, dry wedm, mrr, kerf 1 introduction electro discharge machining (edm) process is a non-conventional and non-contact machining operation which is used in industry for high precision products especially in manufacturing industries, aerospace and automotive industries, communication and biotechnology industries [1-7]. edm as shown in figure 1, is known for machining hard and brittle conductive materials since it can melt any electrically conductive material regardless of its hardness [4-5]. edm is a type of thermal machining where the material from the workpiece is removed by the thermal energy created by the electrical spark [5, 8, 9]. the workpiece machined by edm depends on thermal conductivity, electrical resistivity, and melting points of the materials [10-12]. a series of electrical sparks or discharges occur rapidly in a short span of time within a constant spark gap between micro sized tool electrode and workpiece material. the nature of sparks is repetitive and discrete. the tool and the workpiece are adequately both immersed in a dielectric medium, such as, kerosene, deionised water or any other suitable fluid [5, 13, 14]. the non-contact nature of the process with nearly force free machining allows a soft and easy to machine electrode materials to machine a very hard, fragile or thin workpieces [15-17]. thus, due to its non-contact nature; mechanical stresses, chatter, and vibration problems during machining can be eliminated [18]. this paper is reviewed comprehensively on types of edm operation. a brief discussion is also done on the machining responses and mathematical modelling. figure 1: schematic diagram of edm. electrical discharge machining: a review 4 2 types of electro discharge machining (edm) some of the variations of edm process that can be altered for micro fabrication applications are micro-edm, wire edm (wedm), dry edm [4, 19-21]. 2.1 wire edm (wedm) wire electrical discharge machining (wedm) was introduced because it has the ability to cut intricate shapes and extremely tapered geometries with high performance especially in precision, efficiency, and stability [5, 22, 23]. wedm operation has a very similar material removal mechanism as edm process except wedm uses winding wire as an electrode [5, 6, 24]. micro-wedm operation uses a very small diameter wire (ø 20-50 µm) as the electrode to cut a narrow width of cut in the workpiece. the wire is pulled through the workpiece from a supply spool onto a take-up mechanism. discharge occurs between the wire electrode and the workpiece in the presence of a flood of dielectric fluid. the most important control parameters for this process are discharge current, discharge capacitance, pulse duration, pulse frequency, wire speed, wire tension, voltage, and dielectric flushing condition [6, 20, 25]. 2.2 micro-edm edm operation has already been developed in micro scale industries, as delicate micro tools can machine workpiece surface without any deviation or breakage. micro-edm follows the similar principle of conventional edm technology. however, there are some differences between these two machining in terms of circuitry. edm uses resistance capacitance relaxation (rc-relaxation) circuit while micro-edm uses rc-pulse circuit. in rc-relaxation circuit, current and voltage are usually assumed as constant in modelling process. however, in reality, for rcrelaxation circuit, current and voltage are controlled at a predefined level throughout the pulse on-time. in contrast, based on the modelling process and parametric analysis, rc-pulse generator for a single discharge shows that the current and voltage are not maintained to any predefined level. still, the rc-pulse generator depends on capacitor charge state at any instant. the rc-pulse circuit type is known to have low material removal rate (mrr) since it can produce very small amount of discharge energy. micro-edm is particularly developed to manufacture component of sized between 1 and 999 µm. hence, in order to produce high precision and high accuracy micro geometries products, micro-edm is a suitable type of machining [26-29]. 2.3 edm of non-conductive materials materials that are able to provide a minimum electrical conductivity of 0.1 scm -1 can be processed using edm. thus, materials like metals and conductive ceramics are capable to undergo this process [30-32]. researchers are applying edm and micro-edm to machine ceramics since they are difficult to machine using conventional cutting techniques [33, 34]. but, in order to make the machining process to be continuous, the ceramics need to be conductive. so, one of the solutions is to create a composite with dopants such as titanium nitride (tin) or tungsten carbide (wc) onto the ceramic. other alternative is to create a conductive compound by embedding the ceramic particles in a metal matrix. another approach is by using the ultrasonic assisted spark erosion. the ultrasonic energy can assist in creating spark erosion and lead to crack formation that causes spalling [10, 31, 32]. non-conductive ceramics also have been successfully machined by edm using the assisting electrode method (aem) (figure 2) with some modifications done in the process which is one of the commonly method used [31, 32, 35-37]. in aem, a conductive layer is applied on top of the non-conductive ceramic in order to generate spark between the workpiece and the tool electrode. high temperature around the dielectric fluid will degenerate the polymer chains and creates carbon elements from cracked polymer chains. the carbon elements, together with the conductive debris cover the ceramic surface to sustain the conductivity [10, 31, 32, 36, 38-40]. figure 2: schematic diagram of micro-edm of non-conductive zirconia using adhesive copper assisting electrode [38]. banu and ali (2016): international journal of engineering materials and manufacture, 1(1), 3-10 5 2.4 dry edm in edm process, dielectric fluid plays an important role in order to flush away the debris from the machining gap. in addition, the dielectric fluid also helps to improve the efficiency of the machining operation as well as improving the quality and economy of the machined parts. the commonly used dielectric fluids are mineral oil-based liquid or hydrocarbon oils which cause fire hazard and environmental problems. this is because dielectric wastes generated during the machining operation are very toxic and non-recyclable. besides that, during the machining operation, toxic fumes (co and ch4) are produced because of the high temperature chemical breakdown of mineral oils. the toxic fumes also pose a health hazard to the machining operators [24, 41-45]. in order to avoid these problems, researchers introduce dry edm which includes dry wedm, dry micro-edm, and dry micro-wedm [4, 5, 24, 46, 47]. dry edm (figure 3) is a green machining method where the electrode used is in a pipe form and gas or air flows through the pipe instead of the liquid as a dielectric fluid which removes the debris from the gap and cools the machining surface [48-52]. as for dry wedm, also known as the wedm using dry dielectric fluid is a modification of the oil wedm operation where gas is used as dielectric fluid instead of liquid. the flow of gas with high pressure helps to remove the debris and also avoids unnecessary heating of the wire and workpiece at the discharge gap. lower tool wear, better surface quality, lower residual stresses, thinner white layer, and higher precision in machining are the prime outcome of this dry technique [1, 24, 53-56]. this dry technique can be applicable for almost all micro level machining operation [52, 57]. figure 3: schematic diagram of dry edm. there are researchers who do not agreed with the idea of using the gas instead of the liquid as the dielectric fluid. it is because when the sparks happened in the air, the erosion effect would be very small since the electrical discharge loses its energy. moreover, the bubble of vapour expands which resulted from the spark into the dielectric fluid and causes the dynamic plasma pressure to rise. it is due to the surrounding dielectric fluid restricts the plasma growth. the bubble collapses and removes the molten metal out of the crater when the temperature decreases during the off time. even though there are some disagreements among the researchers, the dry edm was first introduced and reported by nasa in 1985 [58]. the commonly used gases as the dielectric fluid are atmospheric air, compressed air, liquid nitrogen, oxygen, argon and helium gas [51, 56, 59]. some research shows that material removal rate (mrr) improves when oxygen is used as the dielectric fluid [60, 61]. it is because the oxidation reaction occurs with the supply of the oxygen gas which increases the work removal volume during one discharge cycle. in addition, there is no corrosion on the machining surface but it may suffer from rusting due to the oxidation [61]. compared to conventional wedm, the vibration of the wire electrode, narrower gap distance, and very negligible process reaction force in dry micro-wedm assists this process to enable high accuracy in finishing of cut. higher machining speed and lower electrode wear ratio are achieved in dry edm milling. three dimensional (3d) machining of cemented carbide can be done by using dry edm milling [53, 62]. higher material removal rate (mrr) can also be achieved in dry edm when the workpiece is added with the ultrasonic vibration. this is because the ultrasonic vibration helps to flush of the molten metal from the craters [19]. polarity is a one of the important factor in machining dry edm. when the polarity of the tool electrode is negative, the tool wear ratio is smaller and the material removal rate is higher compared to the positive polarity [1, 56]. the machining operation stability is maintained when the tool is in rotation or planetary motion [63]. low electrode wear ratio in dry edm is due to the small physical damage of the tool electrode caused by the reactive force. it is because the dry edm is free from the vaporization of liquid dielectric fluid when the discharge occurs. besides that, adhesion of machining debris on the electrode helps to reduce electrode wear [61]. electrical discharge machining: a review 6 3 machining responses 3.1 kerf kerf (figure 4) is a width of the machined slots which is one of the most vital characteristics of wedm [64, 65]. the corner errors and kerf variation are usually caused by the wire tool deflection and vibration in the discharge gap. these are the main factors that affect the wedm machining accuracy. however, the kerf variations have higher influences on dimensional accuracy in micro-wedm compared to the conventional wedm. this is because, the relative error found in miniature parts produce by the micro-wedm are bigger than the corresponding values in conventional wedm [20]. besides that, a stable machining performance in micro-wedm is related to the debris free machined kerf. it is evident from the debris tracking analysis that the most debris are left out from the kerf section under any constant fluid flow rate. more effectively debris can be excluded and high micro-wedm performance is obtainable with the improvement of jet flushing conditions of the working fluid from the nozzles [66]. in another study, the spark locations using the recorded images, and the effects of servo voltage, pulse interval time, and wire running speed on the distribution of spark location were investigated. the spark distribution is found uniform when servo voltage is high, pulse interval time is long, and wire running speed is low when experimental results are clarified [67]. based on the research, the kerf on germanium wafers in micro-wedm process was analysed using different thin wires with various voltage and capacitor settings. up to 57% more wafers can be sliced in microwedm which depends on wafer thickness and the thin wires. the wafer slicing with wedm is suggested for mainly expensive semiconductor materials [68]. a model on lateral vibration of wire is established where co-related microwedm parameters and vibration amplitude of the wire are analysed. the wire vibration is affected by the open voltage which also measures the breakdown distance. kerf width can be controlled and subsequently machining precision can be improved by controlling the parameter [20]. figure 4: sem micrograph of kerf produced by micro-wedm with 70 µm diameter tungsten wire electrode. 3.2 material removal rate (mrr) dimensional accuracy becomes vital when it comes to edm since close tolerance components are required for products like tools, dies, and mold for press works, plastic molding, and die casting. thus, mrr has been one of the main concerns. the mrr is expressed as the weight of material removed from workpiece over a period of machining time. many researchers have attempted to develop empirical models to estimate mrr. the mrr depends on the amount of pulsed current in each discharge, frequency of the discharge, electrode material, work material, polarity, and dielectric flushing condition. [12, 69, 70]. mrr is low when electrode is connected to negative polarity or cathode. this is due to the dissociated carbon element in dielectric fluid tends to remain to anode and formed the recast layer [41]. material removal mechanism in micro-edm is debatable according to some of the researcher. this is because they are certain deviations in fundamental process mechanism. even though they are many uncertainties regarding the mechanism of the material removal in micro-edm, this machining process is still widely being used in industry for high-precision machining for conductive materials. micro-edm has the capability in removing the material in subgrain size range (0.1-10 µm) regardless of their hardness [51]. 4 mathematical modelling there are quite a numbers of studies are found on parametric study and development of empirical model on microwedm parameters. gap voltage, capacitance, and feed rate were considered as the control parameters and material removal rate (mrr), over cut, kerf, and surface roughness as the performance measures. the optimal parametric settings were derived using simulation. some of the modelling are done through central composite design (ccd), response surface method (rsm), neural network method, regression analysis, neural network with back-propagation, kerf banu and ali (2016): international journal of engineering materials and manufacture, 1(1), 3-10 7 neuro-fuzzy inference system (anfis), grey relational analysis, and taguchi l18 orthogonal array method [20, 24, 64, 71, 72]. modelling is a strong tool for the integration of relationships between output performance and controllable input parameters. there are a few examples of mathematical modelling shown in this review. eqn (1) is an example of mathematical model for vibration in micro end milling using taguchi as the design while the analysis is done by the anova [73]. as for eqn (2) and (3), shows the mathematical model of hardness and mrr of nonconductive zirconia using micro-edm [38]. v = 65.94 + 2.13 × 10−3n − 0.99f + 1.73 × 10−3d − 6.84 × 10−5nf − 1.93 × 10−3nd + 1.01fd (1) where; v is average vibration, n is spindle speed (rpm), f is feed rate (mm/min), d is depth of cut (µm). h = 9201.15 − 62n + 16v + 0.15n2 − 0.05nv − 1x10−4n3 (2) where, h = hardness (hv), n = rotational speed (rpm), v = gap voltage (v). mrr = −101.7 + 1.9n − 2.93v − 4.36 × 10−3n2 + 0.012v2 + 1.1 × 10−3nv + 3.1 × 10−6n3 (3) where; mrr = material removal rate (µg/min), n = rotational speed (rpm), v = gap voltage (v). 5 summary edm process is a flexible machining operation which has the capability in producing complex three dimensional (3d) shapes especially in manufacturing industries, aerospace and automotive industries, communication and biotechnology industries. it is known for machining hard and brittle conductive materials. the tool and the workpiece are adequately both immersed in a dielectric medium. this paper provides an important review on different types of edm operations. a brief discussion is also done on the machining responses and mathematical modelling. this reviewed paper summarizes that: 1. wedm has the ability to cut intricate shapes and extremely tapered geometries with high performance. 2. micro-edm is developed to manufacture micro geometries component with high precision and high accuracy. 3. non-conductive ceramics machined by edm using assisting electrode method (aem) which leads to new structuring of advanced ceramic without geometry diversity. 4. dry edm is a process where gas is used as the dielectric fluid instead of the liquid. it is a process where certain modification during the machining operation is needed in order to achieve a stable machining process. 5. machining responses such as kerf and mrr are important in order to achieve maximum material removal with high accuracy and precision components. acknowledgement this research was funded by ministry of science, technology and innovation, malaysia under research grant sf15016-0066. the authors are grateful to those who contributed directly and indirectly in producing this paper. references 1. abbas, m. n., solomon, d. g., & fuad bahari, m. (2007). a review on current research trends in electrical discharge machining (edm). international journal of machine tools and manufacture, 47(7), 1214-1228. 2. liao, y. s., chen, s. t., & lin, c. s. (2005). development of a high precision tabletop versatile cnc wire-edm for making intricate micro parts. journal of micromechanics and microengineering, 15, 245-253 3. yoo, h. k., kwon, w. t., & kang, s. (2014). development of a new electrode for micro-electrical discharge machining (edm) using ti(c,n)-based cermet. international journal of precion engineering and manufacturing, 15 (4), 609-616. 4. hoang, k. t. & yang, s. h. (2013). a study on the effect of different vibration-assisted methods in micro-wedm. journal of materials processing technology, 213, 1616-1622. 5. hoang, k. t. & yang, s. h. (2015). a new approach for micro-wedm control based on real-time estimation of material removal rate. international journal of precision engineering and manufacturing, 16 (2), 241-246. 6. debroy, a. & chakraborty, s. (2013). non-conventional optimization techniques in optimizing non-traditional machining processes: a review. management science letters, 3(1), 23-38. 7. yan, m. t. (2010). an adaptive control system with self-organizing fuzzy sliding mode control strategy for micro wire-edm machines. international journal of advanced manufacturing technology, 50, 315-328. 8. pour, g. t., pour, y. t., & ghoreishi, m. (2014). electro-spark nanomachining process simulation. international journal of materials, mechanics and manufacturing, 2 (1). 9. pour, g. t., pour, y. t., & ghoreishi, m. (2014a). thermal model of the electro-spark nanomachining process. international journal of materials, mechanics and manufacturing, 2 (1), 56-59. electrical discharge machining: a review 8 10. mohri, n., fukuzawa, y., tani. t., saito, n., & furutani, k. (1996). assisting electrode method for machining insulating ceramics. annals of the cirp, 45, 201-204. 11. mohri, n., fukusima, y., fukuzawa, y., tani, t., & sato, n. (2003). layer generation process on work-piece in electrical discharge machining. cirp annals – manufacturing technology, 52 (1), 157-160. doi:10.1016/s00078506(07)60554-x. 12. mahardika, m., tsujimoto, t., & mitsui, k. (2008). a new approach on the determination of ease of machining by edm processes. international journal of machine tools and manufacture, 48, 746-760. doi:10.1016/j.ijmachtools.2007.12.012. 13. chow, h. m., yang, l. d., lin, c. t., & chen,y. f. (2008). the use of sic powder in water as dielectric for microslit edm machining. journal of materials processing technology, 195 (1-3), 160–170. 14. chen, y. f., lin, y. c., chen, s. l., & hsu, l. r. (2009). optimization of electrodischarge machining parameters on zro2 ceramic using the taguchi method. proceeding of the institution of mechanical engineers, part b: journal of engineering manufacture, 224, 195-205. 15. jahan, m. p., wong, y. s., & rahman, m. (2009). a study on the quality micro-hole machining of tungsten carbide by micro-edm process using transistor and rc-type pulse generator. journal of materials processing technology, 209, 1706-1716. doi:10.1016/j.jmatprotec.2008.04.029. 16. masuzawa, t. (2000). state of the art of micromachining. cirp annals – manufacturing technology, 49 (2), 473488. doi:10.1016/s0007-8506(07)63451-9. 17. schubert, a., zeidler, h., hackert, m., schneider, j., & hahn, m. (2013). enhancing micro-edm using ultrasonic vibration and approaches for machining of nonconducting ceramics. journal of mechanical engneering, 59 (3), 156-164. doi:10.5545/sv-jme.2012.442. 18. ho, k. h. & newman, s. t. (2003). state of the art electrical discharge machining (edm). international journal of machine tools and manufacture, 43, 1287-1300. doi:10.1016/s0890-6955(03)00162-7. 19. chakraborty, s., dey, v., & ghosh, s. k. (2015). a review on the use of dielectric fluids and their effects in electrical discharge machining characteristics. precision engineering, 40, 1-6. 20. di, s., chu, x., wei, d., wang, z., chi, g., & liu, y. (2009). analysis of kerf width in micro-wedm. international journal of machine tools and manufacture, 49(10), 788-792. 21. ali, m. y., karim, a. n. m, adesta, e. y. t., ismail, a. f., abdullah, a. a., & idris, m. n. (2010). comparative study of conventional and micro wedm based on machining of meso/micro sized spur gear. international journal of precision engineering and manufacturing, 11 (5), 779-784. 22. chen, z., huang, y., huang, h., zhang, z., & zhang, g. (2015). three-dimensional characteristics analysis of the wire-tool vibration considering spatial temperature field and electromagnetic field in wedm. international journal of machine tools and manufacture, 92, 85-96. 23. patil, p. a. & waghmare, c. a. (2014). a review on advances in wire electrical discharge machining. in proceedings of the international conference on research and innovation in mechanical engineering (pp. 179-189). springer india. 24. azhiri, r. b., teimouri, r., baboly, m. g., & laseman, z. (2014). application of taguchi, anfis and grey relational analysis for studying, modelling and optimization of wire edm process while using gaseous media. international journal of advanced manufacturing technology, 71 (1), 279-295. 25. tosun, n. & cogun, c. (2003). an investigation on wire wear in wedm. journal of materials processing technology, 134, 273-278. 26. schubert, a., ziedler, h., wolf, n., & hackert, m. (2011). micro electro discharge machining of electrically nonconductive ceramics. aip conference proceedings, 1353, (1) 1303-1308. 27. dhanik, s. & joshi, s. s. (2005). modelling of a single resistance capacitance pulse discharge in micro-electro discharge machining. journal of manufacturing science and engineering, 127 (4), 759-767. 28. das, s. & joshi, s. s. (2010). modeling of spark erosion rate in microwire-edm. international journal of advanced manufacturing technology, 48 (5-8), 581-596. 29. pecas, p. & henriques, e. (2008). electrical discharge machining using simple and powder-mixed dielectric: the effect of the electrode area in the surface roughness and topography. journal of materials processing technology, 200, 250-258. 30. asfana, a., ali, m. y., mohamed, a. r., & hung, w. n. p. (2015). material removal rate of zirconia in electro discharge micromachining. advanced materials research, 1115, 20-23. 31. hosel, t., cvancara, t., ganz,t., muller, c., & reinecke, h. (2011). characterization of high aspect ratio nonconductive ceramic microstructures made by spark erosion. microsystem technologies, 17, 313–318. 32. hosel, t., muller, c., & reinecke, h. (2011a). spark erosive structuring of electrically nonconductive zirconia with an assisting electrode. cirp journal of manufacturing science and technology, 4, 357-361. 33. schubert, a. & zeidler, h. (2009). machining of nonconductive zro2 ceramics with micro-edm. in: van brussel, h.; brinksmeier, e.; spaan, h. (ed): proceedings of the 9 th international conference of the european society for precision engineering and nanotechnology, isbn: 978-0-9553082-6-0, s. 6-9 (bd.2). 34. muttamara, a., janmanee, p., & fukuzawa, y. (2010). a study of micro-edm on silicon nitride using electrode materials. international transaction journal of engineering, management, & applied science & technologies, 1 (1), 001-007. http://dx.doi.org/10.1016/s0007-8506(07)60554-x http://dx.doi.org/10.1016/s0007-8506(07)60554-x banu and ali (2016): international journal of engineering materials and manufacture, 1(1), 3-10 9 35. mohamed, a. r., asfana, b., & ali, m. y. (2014). investigation of recast layer of non-conductive ceramic due to micro-edm. advanced materials research, 845, 857-861. 36. muttamara, a., fukuzawa, y., mohri, n., & tani, t. (2009). effect of electrode material on electrical discharge machining of alumina. journal of materials processing technology, 209, 2545-2552. 37. chen, y. f., lin, y. c., chen, s. l., & hsu, l. r. (2009). optimization of electrodischarge machining parameters on zro2 ceramic using the taguchi method. journal of engineering manufacture, 224, 195-205. 38. banu, a., ali, m. y., & rahman, m. a. (2014). micro-electro discharge machining of non-conductive zirconia ceramic: investigation of mrr and recast layer hardness. international journal of advanced manufacturing technology, 75, 257-267. 39. liu, y. h., li, x. p., ji, r. j., yu, l. l., zhang, h. f., & li, q. y. (2008). effect of technological parameter on the process performance for electric discharge milling of insulating al2o3 ceramic. journal of materials processing technology, 208, 245-250. 40. fukuzawa, y., mohri, n., tani, t., & muttamara, a. (2004). electrical discharge machining properties of noble crystals. journal of materials processing technology, 149, 393-397. 41. pandey, a. & singh, s. (2010). current research trends in variants of electrical discharge machining: a review. international journal of engineering science and technology, 2 (6), 2172-2191. 42. kunieda, m. & furudate, c. (2001). high precision finish cutting by dry wedm. cirp annals – manufacturing technology, 50 (1), 121-124. 43. pradeep, g. m. & dani, m. s. h. (2015). a review on the use of pollution free dielectric fluids in wire electrical discharge machining process. journal of chemical and pharmaceutical sciences, (7), 312-315. 44. dhakar, k & dvivedi, a. (2016). parametric evaluation on near-dry electric discharge machining. materials and manufacturing processes, 31, 413-421. 45. zhang, q. h., zhang, j. h., ren, s. f., deng, j. x., & ai, x. (2004). study on technology of ultrasonic vibration aided electrical discharge machining in gas. journal of materials processing technology, 149, 640-644. 46. khatri, b. c., rathod, p., & valaki, j. b. (2015). ultrasonic vibration-assisted electric discharge machining: a research review. proceedings of the institution of mechanical engineers, part b: journal of engineering manufacture, 1-12. doi: 10.1177/0954405415573061. 47. wang, t., xie, s. q., xu, x. c., chen, q., lu, x. c., & zhou, s. h. (2012). application of uniform design in experiments of wedm in gas. advanced materials research, 426, 11-14. 48. mahendran, s. & ramasamy, d. (2010). micro-edm: overview and recent developments. in national conference in mechanical engineering research and postgraduate students (1 st ncmer 2010), 26-27 may 2010, pahang, malaysia, 480-494. 49. fujiki, m., ni, j., & shih, a. j. (2011). tool path planning for near-dry edm milling with lead angle on curved surfaces. journal of manufacturing science and engineering, 133(5), 051005. 50. besliu, i., schulze, h. p., coteata, m., & amarandei, d. (2010). study on the dry electrical discharge machining. international journal of material forming, 3(1), 1107-1110. 51. paul, g., roy, s., sarkar, s., hanumaiah, n., & mitra, s. (2013). investigations on influence of process variables on crater dimensions in micro-edm of titanium aluminide alloy in dry and oil dielectric media. international journal of advanced manufacturing technology, 65, 1009-1017. 52. skrabalak, g. & kozak, j. (2010). study on dry electrical discharge machining. wear, 5, 7. 53. wang, t. & kunieda, m. (2004). dry wedm for finish cut. key engineering materials, 259-260, 562-566. 54. kunieda, m., lauwers, b., rajurkar, k. p., & schumacher, b. m. (2005). advancing edm through fundamental insight into the process. cirp annals-manufacturing technology, 54(2), 64-87. 55. liqing, l. & yingjie, s. (2013). study of dry edm with oxygen-mixed and cryogenic cooling approaches. procedia cirp, 6, 344-350. 56. singh, p., chaudhary, a. k., singh, t., & rana, a. k. (2015). comparison of outputs for dry edm and edm with oil: a review. international journal for research in emerging science and technology, 2(6), 45-49. 57. yu, z. b., takahashi, j., nakajima, n., sano, s., & kunieda, m. (2005). feasibility of 3-d surface machining by dry edm. international journal of electrical machining, 10, 15-20. 58. leao, f. n. & pashby, i. r. (2004). a review on the use of environmentally-friendly dielectric fluids in electrical discharge machining. journal of materials processing technology, 149, 341-346. 59. besliu, i. & coteata, m. (2009). characteristics of the dry electrical discharge machining. nonconventioal technologies, 2, 5-8. 60. teimouri, r. & baseri, h. (2013). experimental study of rotary magnetic field-assisted dry edm with ultrasonic vibration of workpiece. international journal of advanced manufacturing technology, 67(5-8), 1371-1384. 61. jahan, m. p., rahman, m., & wong, y. s. (2011). a review on the conventional and micro-electrodischarge machining of tungsten carbide. international journal of machine tools and manufacture, 51, 837-858. 62. yu, z., jun, t., & masanori, k. (2004). dry electrical discharge machining of cemented carbide. journal of materials processing technology, 149(1), 353-357. 63. chandra, b., singh, h., & garg, j. (2011). a review on emerging areas of interest in electrical discharge machining. international journal of advanced engineering technology, 2(3), 1-9. electrical discharge machining: a review 10 64. hoang, k. t. & yang, s. h. (2015a). kerf analysis and control in dry micro-wire electrical discharge machining. international journal of advanced manufacturing technology, 78, 1803-1812. 65. ghodsiyeh, d., golshan, a., & shirvanehdeh, j. a. (2013). review on current research trends in wire electrical discharge machining (wedm). indian journal of science and technology, 6(2), 4128-4140. 66. okada, a., uno, y., onoda, s., & habib, s. (2009). computational fluid dynamics analysis of working fluid flow and debris movement in wire edmed kerf. cirp annals-manufacturing technology, 58(1), 209-212. 67. okada, a., uno, y., nakazawa, m., & yamauchi, t. (2010). evaluations of spark distribution and wire vibration in wire edm by high-speed observation. cirp annals-manufacturing technology, 59(1), 231-234. 68. rakwal, d. & bamberg, e. (2009). slicing, cleaning and kerf analysis of germanium wafers machined by wire electrical discharge machining. journal of materials processing technology, 209(8), 3740-3751. 69. dave, h. k., desai, k. p., & raval, h. k. (2012). modelling and analysis of material removal rate during electro discharge machining of inconel 718 under orbital tool movement. international journal of manufacturing systems, 2 (1), 12-20. 70. somashekhar, k. p., ramachandran, n., & mathew, j. (2010). optimization of material removal rate in microedm using artificial neural network and genetic algorithms. materials and manufacturing processes, 25, 467-475. 71. yang, r. t., tzeng, c. j., yang, y. k., & hsieh, m. h. (2012). optimization of wire electrical discharge machining process parameters for cutting tungsten. international journal of advanced manufacturing technology, 60(1-4), 135-147. 72. somashekhar, k. p., mathew, j., & ramachandran, n. (2012). a feasibility approach by simulated annealing on optimization of micro-wire electric discharge machining parameters. international journal of advanced manufacturing technology, 61(9-12), 1209-1213. 73. ali, m. y., mohamed, a. r., khan, a. a., asfana, b., lutfi, m., & fahmi, m. i. (2013). empirical modelling of vibration in micro end milling of pmma. world applied sciences journal (mathematical applications in engineering), 21, 73-78. international journal of engineering materials and manufacture (2020) 5(1) 1-1 https://doi.org/10.26776/ijemm.05.01.2020.01 m. y. ali mechanical engineering programme area faculty of engineering, universiti teknologi brunei tungku highway, gadong, bandar seri begawan be1410, brunei darussalam e-mail: yeakub.ali@utb.edu.bn reference: ali, m. y. (2020). an open letter to all ijemm members on covid–19. international journal of engineering materials and manufacture, 5(1), 1-1. an open letter to all ijemm members on covid–19 mohammad yeakub ali received: 24 march 2020 accepted: 26 march 2020 published: 30 march 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 dear ijemm members i wanted to provide an update to the broader community of international journal of engineering materials and manufacture (ijemm) regarding our efforts to alleviate the spread of the covid-19 coronavirus. the editorial board is deeply sympathised with the people suffering worldwide due the outbreak of pandemic covid-19. we are closely monitoring the outbreak and implementing social isolation and other measures, according to world health organisation guidelines, to mitigate the impact on our members, volunteers and customers around the world. as the safety of people is of highest priority, our aim is to continue delivering our services for editors, reviewers, authors, readers, and other members to the highest possible standards using our online web-based platforms. i trust that each of you is doing well and finding ways to cope with this challenging pandemic situation which is a test from god, the almighty. please stay safe, do not panic, heighten your spirituality and seek forgiveness. with thanks and regards, professor ir. dr. mohammad yeakub ali editor-in-chief international journal of engineering materials and manufacture international journal of engineering materials and manufacture (2020) 5(2) 29-39 https://doi.org/10.26776/ijemm.05.02.2020.01 mrityunjoy hazra and satyapal singh defence metallurgical research laboratory (dmrl) p.o. kanchanbagh, hyderabad 500 058, india e-mail: mhazra@dmrl.drdo.in reference: hazra, m. and singh, s. (2020). failures of flexible diaphragm couplings of power take off (pto) shafts of an aircraft by surface discontinuity, controlled by stress concentration or stress intensity factor. international journal of engineering materials and manufacture, 5(2), 29-39. failures of flexible diaphragm couplings of power take off (pto) shafts of an aircraft by surface discontinuity, controlled by stress concentration or stress intensity factor mrityunjoy hazra and satyapal singh received: 24 september 2019 accepted: 15 june 2020 published: 30 june 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 abstract failures of two power take off (pto) shafts of an aircraft have been analysed. two shafts, one each developed by two different manufacturers failed separately during power run endurance test conducted at room temperature and ambient normal atmosphere. in both the cases, cracks were observed on the outer diaphragm disc. one shaft showed cracking in the engine side, while the other one exhibited cracks in the aircraft mounting accessory gearbox (amagb) side. chemical analysis, microstructure and hardness evaluation indicate that the diaphragm material of the shafts is ti-6al-4v alloy used in solution treated and aged condition, as per the desired specification ams 4928. microstructural in-homogeneity, possibly a result of improper forging, was observed in diaphragm material of both the shafts. additionally, surface discontinuities induced by forging and subsequent insufficient machining were noticed on the diaphragms. the diaphragms failed by fatigue with cracks possibly nucleating at surface discontinuities. discontinuities with lower availability in one shaft led to somewhat increased life (466 million cycles) as compared to the life (104 million cycles) of the other shaft. another possible factor contributing to lower life in the later shaft is the presence of higher quantity of nitrogen rich inclusions. controlling factor triggering the failure of diaphragm of shaft with lower life seems to be the available high stress level along the rim periphery, while that for shaft with higher life is presence of few localized sharp surface discontinuities. keywords: failure analysis, power take off (pto) shaft, flexible diaphragm coupling, ti-6al-4v, surface discontinuity, forging defects, nitrogen rich inclusion 1. introduction 1.1 background information two power take off (pto) shafts, one each developed by two different manufacturers separately failed during a power run endurance test carried out at room temperature and ambient normal atmosphere. a noise came out in both the cases and the tests were stopped in each case. failure was detected in form of cracks on diaphragm discs, while inspection was carried out after the test. 1.2 literature survey 1.2.1 flexible couplings a coupling is a tool often used to connect two equipment such as shafts at their ends for purpose of transmitting power. there are various coupling types based on design like sleeve or muff coupling, clamp or split-muff coupling, tapered shaft lock, flexible couplings etc. [1-3]. flexible couplings are those which are used to accommodate slight misalignment to the tune of 1.5 0 (max) and some parallel misalignment. the beauty of this type which differentiates this from other varieties is its superior qualities over others, i.e. in its multipurpose use besides transferring torque [46]. these are often used to drive pumps, fans, compressors, motor generator sets, conveyers, crushers, vibrating screens etc. besides being present in critical aircraft engines. it can be major contributor to performance of two machines being connected. in this regard, construction, installation and maintenance of flexible couplings need serious attention. there are two basic functions of a flexible coupling: (i) transmitting torque between the connected driving and driven equipment, (ii) accommodating all types of misalignments, namely angular, axial (end float) and parallel mailto:*mhazra@dmrl.drdo.in failures of flexible diaphragm couplings of power take off (pto) shafts of an aircraft by surface discontinuity…. 30 (offset) and any of their combinations. in addition to these functions, these couplings are also required to dampen vibration, reduce shock or peak loads, reduce noise, protect the equipment from overload or measure the output torque from the driven equipment, to accommodate thermal expansion of the equipment or any other components etc. these couplings are often classified into following groups depending on various differentiating criteria: (i) general purpose or special purpose (high performance), (ii) lubricated or non-lubricated (dry), (iii) mechanical or metallic/elastomeric etc. a general purpose coupling falls into the special category once it is applied to very critical equipment in a system. the american petroleum institute (api) defines “high performance” in api 671/iso 10441 as those with a “minimum service life of 5 years...without interruption...”. typically, there are two general categories of high performance couplings: lubricated and non-lubricated. high performance gear couplings (a mechanical element) usually require continuous oil lubrication. metallic element types require no lubrication and are typically designed as the disc type or diaphragm type. table 1 gives a glimpse of distinguishing traits of general and high performance couplings based on various differentiating criteria. flexible diaphragm couplings employed in aircraft engine definitely belongs to high performance coupling types, by this definition. 1.2.2 working principle of a flexible diaphragm coupling connecting engine end to aircraft mounting accessory gearbox (amagb) these types of couplings transmit torque from the outside diameter (o.d.) of a flexible disc plate to the inside diameter (i.d.) across the spool, and then from i.d. to o.d. in other words, torque is transferred between i.d. section (rigid hub) and o.d. section (rigid rim) through a disc [4-11]. the disc is of variable thickness having a contoured profile approximating a hyperbola. this shape ensures uniform shear stresses and minimum bending stresses. use of i.d. and o.d. sections of generous radii matching the disc profile reduces local stress concentration significantly and eliminates unexpected and unpredictable fatigue failures. this is also to ensure the maintenance of “infinite life” what is usually rated for a flexible diaphragm coupling by material selection and design under simultaneous actions of specified torque, speed and misalignments. 1.2.3 coupling alignment and misalignments: their importance equipment connected by a flexible coupling should be aligned with the greatest possible accuracy. misalignment has been found to be the major cause of coupling problems [8, 12]. it is the deviation of relative shaft position from a collinear axis of rotation, measured at point of rotation. misalignment occurs through bearing wear, pipe strain, base distortion due to torque, thermal changes, vibrations in the connected equipment etc. the better the initial alignment, the more capacity the system will have to accommodate any operational misalignment. various misalignment conditions are pictorially represented in fig. 1 [5,6,8,11,12]. no specific alignment procedure is applicable on all drives and applicable procedure is worked out individually to suit the conditions at hand. diaphragm couplings accommodate misalignment by material flexure, and its doing so depends upon factors such as number of discs, their sizes and spacing between them. performance of a coupling is significantly influenced by angular as well as axial misalignments [7-11]. both of these conditions are difficult to control in the field. not only that, those also keep on changing with time, equipment, ambient temperature etc. axial misalignment of a coupling is due to differential thermal expansion of the engine and mounting arrangement during operation. occurrence as well as degree of angular misalignment has been found to be quite limited. this (angular) type along with parallel type of misalignments originates from the dynamic operating conditions in an aircraft transmission system. free span of the flexible discs deflects to accommodate angular and minor axial misalignments. nevertheless, angular type of misalignment has been found to be the controlling factor for diaphragm failure and it usually reaches at least three times its rated value before failure is induced. axial and parallel misalignments distort or bend the flexible discs which are designed with thinner cross section to maintain lower bending and axial stresses for a given torque capacity. misalignments in a coupling are often manifested by excessive vibrations. moreover, couplings are also subjected to high cyclic stresses due to occurrence of such misalignments alone only. 1.2.4 coupling failure modes failure of couplings may be due to either faults within the coupling itself (internal conditions) or external conditions [4-7,12,13]. most failures due to internal faults are the result of improper or poor machining. they usually have to do with concentricities, squareness of the mating face, and tolerances on the various piloting or registering diameters. another major cause of failure due to internal faults is improper product design. defective materials and materials with inadequate strength and/or hardness also have contributed too many premature failures and are considered to be internal faults. on the other hand, improper installation, incorrect operation and poor maintenance are some of the external conditions influencing failure. improper design of the flexing-element section, method of attachment to the hubs and rims, and various misalignments has been found to be the main causes of premature fatigue. interestingly, misalignment is usually a result of both internal and external conditions, as we easily understand by this time. all couplings fail primarily because of application of the load levels beyond the capacity for which they were designed, except for rarely occurring material flaws. this is an external condition and usually comes arise out of poor maintenance and/or incorrect operation and/or incorrect installation. hazra and singh (2020): international journal of engineering materials and manufacture, 5(2), 29-39 31 table 1: distinguishing traits of general and high performance couplings differentiating criteria general purpose couplings high performance couplings design types gear, grid, chain, disc and diaphragm gear, disc and diaphragm material and heat treatment flame hardened aisi 1045 nitride hardened aisi 4140 coupling size (inch) 1.5 to 5 3 to 6 horsepower (hp) @ rpm (ranges) 0.1000 @ 3000 rpm, >1000 hp @ 1800 rpm >1000 hp @ 3600+ rpm balancing non balanced balanced configuration sometimes with spacers always with spacers table 2: various types of coupling failures cause of coupling failure examples general cause poor maintenance failure to inspect, poor maintenance of connected equipment leading to excessive loads on the couplings. incorrect operation too frequent starts and stops, improper vibration monitoring, electrical faults incorrect installation poor alignment, over tight or loose fasteners specific cause excessive misalignment poor initial alignment, unaccounted for thermal movements, foundation settling, pipe strain, improper equipment mounting design or loose equipment mounting bolts excessive torque electrical fault (momentary spike), unaccounted for motor induced torque oscillations (synchronous motor – transient start up) other damage bolt failure from too loose or too tight installation torque fig. 1: proper alignment and various misalignment types: (a) alignment, (b) parallel offset misalignment, (c) angular misalignment, (d) combined angular-offset misalignment, (e) end-float. the over stresses so induced often lead to excessive misalignment, excessive torque (either steady state, transient, momentary spike, or oscillating) and other damaging conditions. the over stresses influence differently on different coupling to induce various reaction types and failure modes. table 2 lists the general as well as specific causes for coupling failures and examples of each [4-7]. the most common failure modes for diaphragm couplings are due to either excess misalignment or a torque overload. failure due to misalignment generally means excessive angular or parallel offset misalignment, with or without axial misalignment. angular misalignment causes an alternating stress in the web of the diaphragm as it bends back and forth with each revolution [4-7]. failures occur due to bending fatigue and start with a crack in the flexible element. axial misalignment often stretches the diaphragm, resulting in an additional continuous stress and contributes positively to the failure in addition to the effect of angular misalignments (fig. 2a). on the other hand, excessive torsional oscillations can cause a fatigue crack at a 45 0 angle to rotation (fig. 2b). torque overloads cause distortion of the diaphragm and can cause a rippling effect in the web (fig. 2c). failures of flexible diaphragm couplings of power take off (pto) shafts of an aircraft by surface discontinuity…. 32 fig. 2: various coupling failure types: (a) under zero axial displacement, (b) under angular misalignment and large axial displacement, (c) buckling and and cracking under angular misalignment and large axial displacement. fig. 3: various coupling failure types – influence of stress reversal: (a) under excessive angular misalignment and axial displacement, (b) under excessive torsional oscillation, (c) under torque overload. magnitude of stress reversal is likely to influence the disc failure mode predominantly [13]. in case of a completely reversed stress cycles (zero mean stress), any particle on a disc is subjected to tension and compression alternately. on the other hand, for a tension-tension cycles (positive mean stress), any particle is subjected to various degrees of tension only. likewise, two distinct failure modes are usually noticed, one at zero axial displacement and the other at large axial displacement. fig. 3a and fig. 3b shows diaphragm failure for case of a zero and large axial displacements respectively. distinguishing traits of the crack path in later from that of the former are: traversing of the crack path from thinnest to the thickest portion, severe buckling of the disc in later case, and very importantly very irregular crack path in the later case. fig. 3c shows a crack traversing 270 0 before buckling of the disc took place, indicating that the torque load made a small contribution to the total stress on the disc. 1.2.5 details on the presently investigated flexible diaphragm coupling discs pto shaft of the aircraft is designed to transmit power from engine to aircraft mounting accessory gear box (amagb). the engine is connected to the flange input of the pto shaft, as shown in fig. 4. here, engine mounting accessory gear box (emagb), amagb along with pto shaft assemblies are shown schematically. the flange output of the pto shaft is linked to the amagb. it is a flexible coupling shaft rotating with constant velocity. during power transmission, misalignments (angular, axial and parallel) are encountered at the flange-shaft joints. these are absorbed by the elastic deflection/vibration of the diaphragm assembly. a detailed drawing of the pto shaft is shown in fig. 4b. the shaft consists of a long tube electron beam welded to one diaphragm assembly each on both ends, emagb and amagb. there are provisions for shear bolts (3 nos) in the shear section in order to prevent excess torque that may be transmitted to the drives of the aircraft accessory. this is to ensure the breakage of the bolts, in case the torque exceeds a critical value. each of the diaphragm assemblies is made of four thin circular tapered discs, each with a rim along the periphery and hub around the centre. a pair of discs consists of one thick and one thin disc. these circular discs (thick and thin) are welded along the rim. one such set comprising two welded discs is joined to another set by welding along the hub. the welding is carried out in such a way that the inner discs are thinner and the outer ones thicker. all discs are tapered from centre to periphery. the thickness of each tapered disc (thin or thick) increases from periphery (rim) to hub. the inner diaphragms have more influence on the axial stiffness and less influence on the flexural stiffness of the pto shaft and for the outer diaphragms it is other way round. hence, in order to maintain the flexural stiffness (flexural critical speed) and reduce the axial stiffness (axial critical speed) the inner diaphragms are made thinner than the outer diaphragms. hazra and singh (2020): international journal of engineering materials and manufacture, 5(2), 29-39 33 2. experimental procedure initially, as received failed shaft parts were examined visually by naked eye and under magnifying glass. photographs were recorded in the as-received condition and preserved for future reference. representative cross-sectional samples of the failed diaphragm from locations near and away from the failed region were extracted for detailed microstructural investigation using both optical and scanning electron microscopes (om and sem). the specimens were extracted from 4 locations namely at 12, 3, 6 and 9 o’clock positions of the intact as well as failed circular disc pairs of both engine and amagb side diaphragms. the specimens were examined in both unetched and etched conditions. bulk compositional analysis of the diaphragm material was carried out by inductively coupled plasmaoptical emission spectroscopy (icp-oes) (wet type) as well as leco technique (dry), depending on type of elements analyzed. compositional analyses of each phase in the microstructure were carried out by energy dispersive spectroscopy (eds) attachment of the sem. standard kroll’s reagent (1-3 ml hf + 2-6 ml hno3 + 100 ml h2o) was used for etching all the metallographic sections. vickers microhardness readings at 500 gf were taken on metallographically prepared samples to correlate those with the respective microstructures. 3. results 3.1 visual examination pictures of as-received pto shafts are shown in fig. 5. in case of shaft 1 (fig. 5a), cracks were observed on the diaphragm disc at the engine side, i.e. close to the input end. in shaft 2 (fig. 5b), cracks are observed on the diaphragm disc at the amagb side, i.e. close to the output end. fig. 5c displays position of the crack on the diaphragm discs, schematically for both the shafts. in shaft 1, the crack covers almost 2/3 rd of the circumference of the rim section. in shaft 2, crack propagates almost rectilinearly in the vicinity of hub. it also covers the periphery region near the rim. fig. 4: (a) schematic view of pto shaft, emagb and amagb assemblies of aircraft system, (b) detailed schematic drawing of the flexible diaphragm couplings. fig. 5: as-received failed power take off (pto) shafts – (a) general view, (b) shaft 1, (c) shaft 2, (d) schematic diagram showing the location of crack on diaphragm disc in the failed shafts. failures of flexible diaphragm couplings of power take off (pto) shafts of an aircraft by surface discontinuity…. 34 3.2 fractography 3.2.1 shaft 1 fractographs of the failed pieces of the diaphragm are shown in fig. 6. striations marked by downward arrow in fig. 6a indicate that the component has failed by fatigue. the striations are also associated with micro-cracking (fig. 6b). fracture origin could not be identified due to severe rubbing on major portion of the fracture surfcace. presence of particulate material, spherical and irregular shaped, was seen. the eds results on the said features are given in table 3. particles 1 and 2 (fig. 6b,c) are oxygen enriched base metal with little bit of iron. on the other hand, particle 3 reveal composition of the base metal, while 4 contains na, ca, si and cl in the oxygen enriched base metal. fractographs of other local regions (fig. 6e-g) display ductile overload failure. in this case, the particles (5 and 6) are iron and/or oxygen rich. 3.2.2 shaft 2 fractographs are shown in fig. 7. well defined fracture features were seen in few locations on fracture surfaces, while major parts were severely rubbed. as a result, fracture origin could not be identified. presence of fatigue striations with multiple origins is seen in fig. 7a,b. overload features are shown in fig. 7c. particulate material (1 in fig. 7a) containing na, ca, si, cl with oxygen enriched titanium product was noticed (table 3). however, the fracture surface was quite clean with respect to the presence of particulate material, unlike that was observed in case of shaft 1. fig. 6: fractographs of shaft 1at different locations – (a-d) fatigue fractured regions, (e-g) overload failure. fig. 7: fractographs of shaft 2at different locations – (a,b) fatigue fractured regions, (c) overload failure. 3.3 microstructure representative unetched sem images (secondary and back scattered) of the diaphragm cross sections for both the shafts are shown in fig. 8. this is taken from the rim region and it does represent microstructure of the other regions as well. chain type of defects originating at surface often traversed inside as shown in fig. 8a-c. interior cracks of the same chain type of appearance as well as particle pull out were noticed (fig. 8b-d). both the surface as well as interior chain type of defects revealed composition of base metal, while eds was carried out. si and c have been found to be present in the region of particle pull out (point 1 in fig. 8d, table 3). nitrogen rich inclusions were found in the interior of the sample (points 2 and 3 in fig. 8e, table 3). surface discontinuities were observed throughout the diaphragm cross section, as is shown in fig. 8f,h. products rich in oxygen and titanium along with significant amount of na, ca, k and cl were found within those discontinuities as well as at few sub-surface locations (point 4 in fig. 8f, table 3). etched micrographs are shown in fig. 8g-i. equiaxed α plus transformed β microstructure was observed throughout the base regions (away from the weld), while the weld region revealed presence of transformed β. chain type of feature in the interior as well as on the surface with composition near to the base metal composition was well revealed after etching (fig. 8g,h). in case of shaft 2, frequency of occurrence of both the surface discontinuities as well as nitrogen rich inclusions were quite lower as compared to those in case of shaft 1. bulk elemental composition of the diaphragm disc material for shafts 1 and 2 are as given in table 4. hazra and singh (2020): international journal of engineering materials and manufacture, 5(2), 29-39 35 table 3: eds analysis results on various phases as found in fractographs and microstructures particle no. (fig. no.) elements (wt%), balance = ti c o n na k ca mo cu ba si cl fe v al 1 (fig. 3b) -25.3 ---------2.54 2.17 5.49 2 (fig. 3c) -28.6 ---------5.72 2.35 5.03 3 (fig. 3d) ------------1.28 5.55 4 (fig. 3d) -28.1 4.32 1.87 ---1.9 3.1 -2.40 6.80 5 (fig. 3e) - ---------30.86 3.07 7.04 6 (fig. 3g) -26.4 -------- 27.31 1.9 5.77 1 (fig. 4) -24.1 2.42 bal. 4.63 5.7 -2.5 --0.46 1.26 1 (fig. 5d) 37.7 --------42.1 ---- 2 (fig. 5e) --4.5 ---------4.34 7.79 3 (fig. 5e) --3.1 ----------8.81 4 (fig. 5f) -37.8 -4.5 0.8 1.75 ----6.3 -0.68 4.20 table 4: bulk elemental composition of diaphragm disc of shaft1 and shaft 2 sample id content (wt%) o n h v al ti shaft 1 0.1880 <0.005 0.0015 4.40 6.30 bal shaft 2 0.1665 <0.005 0.0010 4.20 6.10 bal fig. 8: scanning electron micrographs of the rim portion of a typical outer surface cross-section of an outer diaphragm disc in se and bse modes (a-f) unetched micrographs showing various defect types, (g-i) etched micrographs revealing forging laps more clearly. etchant: kroll’s reagent. 3.5 hardness representative hardness values were taken at different locations on transverse thick and thin sections of the diaphragm discs of the shafts. there is no difference in hardness values at different locations on the whole diaphragm cross sections. fig. 9 is the reference figure for hardness evaluation marking typical indentation locations on both thick and thin sections of diaphragms of both the shafts. hardness profiles along random locations like along a-a / , b-b / and c-c / were also taken. average hardness values in diaphragms in both the cases are found to be around 335 hv. failures of flexible diaphragm couplings of power take off (pto) shafts of an aircraft by surface discontinuity…. 36 3.6 stress analysis probable stress patterns developing on the diaphragm discs were determined by the finite element method (fem) of analysis. the pattern developed on the failed diaphragm discs on engine side (for shaft 1) and amagb side (for shaft 2) under the combined action of misalignments, peak operating torque and centrifugal forces are shown in fig. 10. maximum stress level was found to exist along some portions of the rim periphery (covering the periphery around 50%) in both the cases. however, very low stress level is obtained in one location near the hub for the failed diaphragm of shaft 2. it has been also found by fem analysis that the diaphragms are so designed that the evolved stress pattern during a power run endurance test is likely to induce a mean stress of the level of 178 mpa. this leads to the lowering of the maximum allowable stress for infinite life of the diaphragm (ti-6al-4v) material than the usually reported value at zero mean stress level. the said limit becomes 551 mpa instead of 420 mpa. at the same time, alternating stress was also reduced to 343 mpa from 474 mpa by the effect of presence of positive mean stress. in the present case, the maximum stress level and alternating stress values are 262 mpa and 85 mpa respectively. this indicates that the diaphragms under consideration were well designed for achieving the infinite life. fig. 9: cross-sectional profile of inner and outer diaphragms of engine and amagb ends (marked points are for microstructure and hardness evaluation). fig. 10: stress patterns developed on the failed diaphragms of the pto shafts under combined actions of misalignments, peak operating torque and centrifugal forces (a) emagb (engine) end outer failed diaphragms, (b) amagb end failed outer diaphragm. hazra and singh (2020): international journal of engineering materials and manufacture, 5(2), 29-39 37 4. discussion 4.1 suitability of material microstructure of the diaphragm discs of both the shafts was found to be equiaxed α plus transformed β, as expected from solutionizing (at 955 0 c/1hr soaking/water quench) and aging (at 540 0 c/4hrs soaking/air cooled) heat treatment, governed by the intended ams 4928 specification [14]. it is also supported by the chemical composition and hardness level. forging laps or folds of same bulk (ti-6al-4v) composition were observed at surface as well as in the interior. products rich in oxygen and titanium along with significant amount of na, ca, k mo, si and cl were found within surface discontinuities as well as at few sub-surface locations (point 4 in fig. 8f, table 3) on the diaphragms of both the shafts. nitrogen rich inclusions were seen in the interior portion of the diaphragm discs of both the shafts (points 2 and 3, fig. 8e). those inclusions cracked occasionally. the above said surface discontinuities and forging laps are most likely to be the result of high temperature forging. particles with k, ca, mo, si elements sitting within those discontinuities may have originated from the glass coatings used in closed die forging of titanium alloys. subsequent insufficient machining could not remove the mixed coating material oxygen rich layer as well as the forging laps. another possible origin of the defect may be the starting blanks. the characteristics of various defects present on the diaphragms of both the shafts in terms of morphology, composition and location within the disc are given in table 5. table 5: physical characteristics of various defects on diaphragm discs defect type location of occurance morphology composition (wt%), as obtained by eds oxygen-rich inclusions interior in fractographs, surface and sub-surface in microstructures circular/semi-circular shaped 38-40 o, 5-6 al, 2-3 v, ti – bal. nitrogen-rich inclusions interior – in microstructure triangular, rod shaped (gelly fish) type 3-5 n, 7-8 al, 4-5 v, ti – bal forging defects folds/laps starting from surface crack type, appearing dark in microstructure 3-5 o, 7-9 al, 3-4 v, ti – bal. folds/laps embedded in the interior crack type, appearing with same contrast to that of the base alloy in microstructure, but with a clear boundary base material sub-surface product in 5-40 μm distance below the surface circular shaped 37-40 o, 4-5 al, 0.50-1.00 v, 4-5 na, 1-2 ca, 0.50-1.00 k, 6-7 cl, ti – bal. these defects are acting as stress concentrators during testing as the torque is transferred from engine to aircraft mounting accessory gear box (amagb) and have originated the failure. the cracks have preferentially nucleated at those regions and the propagation occurred by fatigue as seen by striations and microcracks. lower frequency of surface discontinuities along with the rare presence of nitrogen rich inclusions in the diaphragm material of shaft 2 might have resulted in its somewhat increased life (466 million cycles) as compared to that of the diaphragm of the shaft 1 (104 million cycles). nevertheless, fatigue failure of the present type is most likely to have initiated from the surface discontinuities, as surface cracks are the most vulnerable locations for fatigue crack initiation. 4.2 influence of mechanical load maximum stress values exist along the rim periphery of both the failed discs, as was shown in fig. 10. this is probably due to the existence of highest stress concentration regions along the rim periphery because of the presence of thinnest diaphragm sections along with sharper (lower) fillet radius. however, failure initiation of only one diaphragm (that of the shaft 1) was along the periphery and it failed along the periphery. on the other hand, failure of the other diaphragm seems to have originated at a region between rim and hub of the diaphragm. this is supported by the (presence of a smooth linear path along major portion of the) crack profile, although origin could not be identified due to severe rubbing. interestingly, there is a region of low stress in between rim and hub of the diaphragm disc of shaft 2, as shown in fig. 10b. probably, different origins of the failure of the diaphragm material of similar microstructure may be attributed to the location of attainment of the critical stress intensity factor (kic, i.e. fracture toughness). failure origin is that region wherein crack of considerable width and length is developed to make the failure event complete by attaining the kic value. now, value of stress intensity factor (k) in presence of a crack and/or discontinuity depends on both the available stress level (σ) and notch dimension (a) by the equation: k = σ√(πa) (1) greater the k value for a notch/crack, greater is its chance to reach kic value quickly. now, by eq. (1), k depends on the product σ√a, not individually on σ and a. thus, even if the available stress level (σ) is quite low, for a sharper dent (i.e. bigger a), the product σ√a and so k value may be quite high approaching to that of kic. thus, the controlling factor triggering the failure of diaphragm of shaft 1 seems to be the available high stress level along the highly stress failures of flexible diaphragm couplings of power take off (pto) shafts of an aircraft by surface discontinuity…. 38 concentrated rim periphery, while that for shaft 2 is presence of few localized sharp surface discontinuities. this indicates that stress concentration effect dominates the failure of shaft 1, while the dimension of surface discontinuity and so time to reach stress intensity factor (sif) controls the failure of shaft 2. 4.3 modification of defect shape five things to be noted: (i) frequency of occurrence of surface discontinuity is lower in the diaphragms of shaft 2 than that of shaft 1, (ii) the average aspect ratio (≈ 2) of the surface discontinuities on diaphragms of both the shafts have been found to be the same (iii) sharpness of the surface discontinuities is the controlling factor in failure of shaft 2 unlike that for shaft 1, (iv) consumed cycles (466 million cycles) of power run endurance test is higher in case of shaft 2 than that (104 million cycles) for shaft 1, (v) only one surface discontinuity is likely to have taken the lead in causing the failure in both the cases. thus, it is most likely that there was a coupling effect of shape (sharpness) of the surface discontinuities and the available stress levels on the diaphragm discs of shaft 2. this has led to the creation of a very sharp surface discontinuity along with a low stress region in the region between rim and hub, and those happenings led to the failure under a combined effect. on the other hand, average sharpness of the discontinuities on diaphragms for both the shafts is similar, probably because of similar and homogenous microstructure in major portion of the diaphragm surfaces of both the shafts and their exposure to similar level of misalignments, peak operating torque and centrifugal forces. however, further investigation needs to be carried out on factors controlling the shape modification of surface discontinuities for both the shafts and also on coupling effect of stress distribution and defect shape modification for shaft 2. 5. conclusions i. surface discontinuities are most likely to have initiated failure of the diaphragm discs of both shafts. ii. lower frequency of occurrence of surface discontinuities in the diaphragm material of shaft 2 might have resulted in its somewhat increased life (466 million cycles) as compared to that of the diaphragm of the shaft 1 (104 million cycles). iii. controlling factor triggering the failure of diaphragm of shaft 1 seems to be the available high stress level along the rim periphery, while that for shaft 2 is presence of few localized sharp surface discontinuities. iv. surface discontinuities causing the failure are result of high temperature forging and subsequent insufficient machining. 6. recommendations i. microstructural characterization of the starting blank should be carried out to detect the presence of surface irregularities, nitrogen/oxygen rich inclusions, forging lap, microstructural banding and chunky alpha. the same should be also done on the forged blanks, before final machining. all forgings as well as finished and ready to assemble discs should undergo ultrasonic flaw detection test as per ams-2631 class a (2mm fbh) and need to be certified by airworthiness certifying authorities [15]. ii. the starting blank for forging the ti-6al-4v diaphragm discs should be judiciously thicker (at least 2 mm thicker than that was used in present case). this is to ensure that those types of undesired defects present on and near to the surface after forging are removed completely during subsequent machining. iii. the product should be free of any oxygen-rich layer such as alpha casing, or other surface contamination, determined by microscopic examination. in this regard, the approved and identified feed stocks may be coated with suitable temporary coatings prior to transit or during storage. acknowledgement the authors would like to thank dr. vikas kumar, distinguished scientist (ds) and the director, dmrl for his constant encouragement to work on the present field. also, funding from drdo is gratefully acknowledged. references 1. https://www.merriam-webster.com coupling, last accessed on 18.03.2020. 2. rivin, e. i. criteria for power transmission couplings: part i, url: https://sdp-si.com/rivin/art1.php, last accessed on 18.03.2020. 3. a review of windsurf universal joint types: http://www.unifiber.net/review-windsurf-uj-types, last accessed on 18.03.2020. 4. ansi/agma 9003-b08, 2008, “flexible couplings – keyless fits”, american gear manufacturers association, alexandria, virginia, last accessed on 18.03.2020. 5. calistrat, m. m. 1994, flexible couplings – their design selection and use, houston, texas: caroline publishing, last accessed on 18.03.2020. 6. “advances in gas turbine couplings”, proceedings of the thirty-sixth turbomachinery symposium, turbomachinery laboratory, texas a&m university, college station, texas, pp. 157-172, last accessed on 18.03.2020. 7. rothfuss, n. b. design and application of flexible diaphragm couplings to industrial-marine gas turbines, 73gt-75, asme, n.y. 10017, last accessed on 18.03.2020. https://www.merriam-webster.com/dictionary/coupling https://sdp-si.com/rivin/art1.php http://www.unifiber.net/2015/blog/2015/03/review-windsurf-uj-types/ hazra and singh (2020): international journal of engineering materials and manufacture, 5(2), 29-39 39 8. flexible shaft couplings maintenance guide, epri, palo alto, ca: 2003. 1007910: www.epri.com, last accessed on 18.03.2020. 9. flender standard couplings (catalog md 10.1 • 2009) by a. friedrich flender ag: www.siemens.com or www.flender.com, last accessed on 18.03.2020. 10. features and applications of flexible disc couplings, url: https://hvhindustrial.com/blog/flexible-disccouplings-features-applications, last accessed on 18.03.2020. 11. flexible couplings, url: http://www.tribology.co.uk/articles-papers/flexible-couplings/, last accessed on 18.03.2020. 12. gibbons, c.b. 1976, “coupling misalignment forces,” proceedings of the fifth turbo machinery symposium gas turbine laboratories\ texas a & m university, college station, texas, pp. 111-116, last accessed on 18.03.2020. 13. calistrat, m.m. verification of metal diaphragm coupling performance in: international conference on flexible couplings for high power and speeds, june 29 th , 1977, michael neale & associates ltd., , last accessed on 18.03.2020. 14. ams 4928: annealed ti-6al-4v alloy bars, wires, forgings, rings, and drawn shapes. 15. sae ams 2631:2017 – ultrasonic inspection, titanium and titanium alloy bar, billet and plate, https://www.sae.org/standards/content/ams2631/, last accessed on 18.03.2020. https://hvhindustrial.com/blog/flexible-disc-couplings-features-applications https://hvhindustrial.com/blog/flexible-disc-couplings-features-applications http://www.tribology.co.uk/articles-papers/flexible-couplings/ https://www.sae.org/standards/content/ams2631/ international journal of engineering materials and manufacture (2022) 7(3) 95-102 https://doi.org/10.26776/ijemm.07.04.2022.02 md abdullah, mohammad zoynal abedin and saddam hossen department of mechanical engineering dhaka university of engineering & technology gazipur 1707, bangladesh e-mail: abedin.mzoynal@duet.ac.bd reference: abdullah, m., abedin, m. z. and hossen, s. (2022). effects of fire hazards due to leakage in gas circulation lines in bangladesh: a comprehensive review. international journal of engineering materials and manufacture, 7(4), 95-102. effects of fire hazards due to leakage in gas circulation lines in bangladesh: a comprehensive review md abdullah, mohammad zoynal abedin and saddam hossen received: 02 july 2022 accepted: 29 september 2022 published: 25 october 2022 publisher: deer hill publications © 2022 the author(s) creative commons: cc by 4.0 abstract fire hazards caused by leakages in gas circulation lines are dangerous and pose a threat that results in a significant loss of wealth, lives, and the environment. by adopting significant precautions, the risks of fire hazards can be reduced effectively through the use of new technologies and preventive measurements of the system. in addition, the effects of fire hazards due to leakage in gas circulation lines in the buildings as well as in the other systems can be assessed to create the context of preventive measures for a fire protection system in a way to overcome the fire hazards in gas circulation lines. the paper aims to review the effects of fire hazards due to leakage in gas circulation lines in bangladesh. it is noted that in bangladesh during 2018-2019, the total gas distribution line in the titas gas system was measured as 13,138 km where the pressure-reducing system or gas riser was found as 1.2 million and the number of customers was found as 2.866 million. in the system, the number of fire accidents that occurred was 208 in the circulation system. because of connecting the illegal gas lines and poor maintenance of the system, bangladesh faces significant fire hazards every year. to avoid this kind of problem, proper maintenance along with the varieties of new technologies incorporating sensors and microcontrollers can be utilized. keywords: fire hazard effect; fire hazards; leakage; gas circulation line; protection. 1. introduction fire is an exothermic chemical reaction that occurs when fuel and oxygen are combined and releases energy, flame, and a number of other results [1]. the transformation of both the sluggish dual link in oxygen molecules to the bonds present in the smoke of both carbon dioxide and water causes the release of energy, resulting in the reason flame is found to be hot [2]. additionally, it is observed that a flame is created, consisting of atmospheric co2, liquid water, air, and nitrogen, which, when heated sufficiently, may be seen to ionize in a way to form plasma [3]. its capacity to support a variety of ecological systems and encourage growth are only two of its numerous advantageous impacts [4]. if a fire kills people, heavy rains may accelerate soil erosion caused by water. additionally, when vegetation is burned, nitrogen is released into the atmosphere as opposed to nitrate and phosphate, which stay in the dust and are quickly regenerated into the soil. even while ammonia vegetation like clover, peas, and beans and lightning may fix atmospheric nitrogen and turn it into ammonia, the nitrogen lost as a result of a fire gradually reduces soil fertility [5]. humans have used fire in a variety of rituals, including cooking to produce heat and clearing land for agriculture. the capacity to manage fire marked a significant shift in the early civilization. people were able to cook food by using fire to provide heat and light, improving the diversity while also minimizing sickness through destroying its micro-organisms [6]. nocturnal predators were also scared off by fire. cooked food has been discovered dating back million years ago, while fire was seen to be used in various ways for the required purposes [7-10]. this efficient approach does have certain drawbacks, though. the earth's surface is becoming more and more susceptible to ever-larger uncontrolled flames as a result of the world's expanding population, fragmenting forests, and warming temperatures. on the other side, this practical strategy damages human infrastructure, ecosystems, and human health. additionally, it generates rings with oxygen and smoke that might fuel new fires and further heating the atmosphere. up to 5 million square kilometers of land can burn worldwide in a single year [11]. modern applications for fire are numerous. almost every human on the earth utilizes fire every day in a controlled setting, to put it broadly. every time a person operates an internal combustion engine vehicle, they employ fire. the vast mailto:abedin.mzoynal@duet.ac.bd abdullah et al. (2022): international journal of engineering materials and manufacture, 7(4), 95-102 96 majority of people on earth get their energy via boilers, which burn fuels before generating steam to turn turbines. the use of fire in combat has a long and illustrious history. fire served as the foundation for all modern thermoelectric devices [12]. usable energy is released when fuel is burned. wood has been used as a power source in the past and the present. fossil fuels including coal, fossil fuels, and petroleum are used to generate the great bulk of the world's energy today; international energy agency estimates that in 2002, these fuels generated nearly 80% of the world's electricity [13]. methods like planned or controlled burns and the use of wildland fires may be used in international efforts to prevent wildfires [14-15]. any natural fiber that is restricted yet permitted to burn is used in wildland fires. fires started by public entities but under dangerous weather conditions are known as forest fires [16]. in the majority of developed locations, firefighting services are available to extinguish or control uncontrolled flames. an extensively trained firefighter is the first and foremost responder and rescuer in firefighting, primarily to extinguish hazardous fires that threaten lives, properties, and the environment as well as to rescue people and in some cases or jurisdictions also animals from the dangerous and deadly situations. limiting sources of ignition is the aim of fire prevention. another aspect of fire protection is fire prevention education [17]. in order to prepare people for a building fire, fire drills are routinely done in buildings, particularly in tall buildings and schools. most jurisdictions consider arson, which is defined as purposefully starting destructive fires, to be a crime [18]. to lessen fire damage, model building regulations contain both passive and proactive fire protection features. sprinkler systems are the most often used sort of active fire defense. most developed nations assess the fire resistance, ignitability, and flash point of construction materials and equipment in order to improve passive fire safety of structures. in cars and ships, flooring, polymers, and upholstery are also put to the test. when damage cannot be avoided by fire prevention and fire protection, fire insurance may be helpful [19]. 2. leakages and fire hazards in gas circulation a sulfur stink is frequently employed to detect leaks early since natural gas is colorless, odorless, and explosive [20, 21]. natural gas is produced as a result of layers of decaying plant and animal waste being subjected to extremely high heat and pressure under the earth's surface over millions of years [22]. chemical bonds in the gas store the energy that the plants received from the sun [23]. a fossil fuel is what natural gas is categorized as. natural gas is a nonrenewable hydrocarbon that is employed in the production of energy, heat, and cooking. additionally, it is used as a chemical feedstock for the production of plastics and other important substances for the economy. natural is used for a multitude of purposes in homes around the nation. after electricity, natural gas is the energy source that is utilized in homes the second most frequently. gas is indirectly used by houses in this way since it is also used to produce electricity. however, natural gas is mostly employed in equipment and systems that are made to run on this type of fuel. the most prevalent forms of this versatile energy source are compressed natural gas (cng) and liquefied natural gas (lng), although the latter is more frequently used for transportation than for heating homes. although natural gas has a better safety record than other main energy sources, it must still be used with caution. explosions, massive fires, and the possibility of suffocation, either from smoke inhalation or carbon monoxide poisoning from badly burned gas, are all potential threats. natural gas, fortunately, does not ignite or explode on its own. to spark combustion, particular conditions and a source are required. here's some advice on how to minimize unnecessary damage, injuries, and even death. there are three main ways to detect a natural gas leak, and combining all three can assist evaluate whether or not a leak is likely. the most crucial is the sense of smell. if we smell something that smells like sulfur or rotten eggs but can't place the source, it could be a gas leak. after then, the simplest way to tell if a leak is occurring is to listen. the following sections deal with gas leakage, gas line leak and fire hazard in the gas circulation line in bangladesh. in bangladesh during 2018-2019, the total gas distribution line in the titas gas system was measured as 13,138 km where the pressure-reducing system or gas riser was found as 1.2 million and the number of customers was found as 2.866 million [24]. in the system, the number of fire accidents that occurred was 208 in the circulation system. because of connecting the illegal gas lines and poor maintenance of the system, bangladesh faces significant fire hazards every year [24]. 2.1 gas leakages a gas leak happens when natural gas or another gaseous product leaks into an unintended location from a pipeline or other containment system. gas leaks pose a threat to the environment and to individuals. over time, even a little gas leak into a structure or other enclosed space can accumulate to explosive or lethal proportions [25]. leaks of natural gas and refrigerant gases into the atmosphere are particularly dangerous since they may result in ozone depletion and global warming [26]. byproducts of gas leaks connected to industrial machinery and operations are fugitive emissions. natural gas leaks brought on by the mining and use of fossil fuels are referred to as fugitive gas emissions. methane, the primary component of natural gas, is colorless and odorless. uncomfortable smells, such as mercaptan residues, are frequently supplied to help find breaches [25]. this smell is like rotting eggs or a moderately repulsive effects of fire hazards due to leakage in gas circulation lines in bangladesh: a comprehensive review. 97 animal odor. to reduce the risk of fire and explosion, anyone who smells the odor should leave the area and avoid using open flames or power connections. the gas company is required to check for gas leaks in gas meters and internal gas lines from the entry point into the structure to the discharge end of the electric meter. as a result, biogas suppliers could need to check individual homes for potential hazards [25]. a grade 1 leak needs immediate repair or continued effort until there is just no risk increase because it poses an immediate or imminent risk to people and assets. here are a few instances of leaks from grade 1 [26] such that—any leak that the operating staff on the site believes to be an immediate threat. any signs that a structure, pipeline, or underground space has experienced gas migration. a measurement that is close to a structure’s exterior wall or that is close to an area where gas is anticipated to flow. a result of 80% or higher lower explosive level (lel) in a tight space. a result of 80 percent of overall lower explosive level or above in minor structures where gas is anticipated to move to a structure beyond the boundary. any leakage that is audible, tactile, and visible could put people or property in danger. a second-grade leak is one that is first determined to be quasi but necessitates scheduled repair owing to the possibility of further dangers [26]. there are a few illustrations of second-grade leakage. defects that demand treatment before bottom chilling and other unfavorable shifts in ventilation circumstances fall under this category. during cold or other unfavorable weather conditions, any leak would probably make its way to the exterior wall of a building. leaks that need to be fixed in 180 days. a result of a 40 percent lower explosive level or higher below a walkway inside a completely surfaced area does not indicate a primary hole [26]. a result of 100 percent lower explosive level or higher below a road inside a masonry walking path to fossil energy movement of people although no primary leak. a result is less than 80 percent lower explosive level in tiny components where gas might possibly move, posing a threat. a result in a specific area that falls between 20 percent and 80 percent lower explosive level. on a pipeline with a required minimum elastic modulus of 30 percent or higher in a category 3 or 4 position that is not a primary leak [23]. a result of 80 percentage lower explosive level or higher in gas-related components. any leak that is large enough, in the opinion of operational staff on the spot, to warrant planned maintenance. a stage iii leak is quasi when discovered and is likely to remain so in the future. some examples of grade 3 leaks can be found [26]. as a result, a result in minor gas-linked components that is less than 80 percent lower explosive level is considered. measurement is taken beneath a roadway where there is no wall-to-wall paving, and the gas is unlikely to travel to buildings beyond the wall. a result that is less than 20 percent lower explosive level in a restricted area [26]. 2.2 gas line leak leaks in gas lines might be harmful. when breathed, natural gas can cause headaches, wooziness, nausea, and vomiting. small leaks frequently go unnoticed, so people get ill without knowing why. however, because domestic natural gas has a sulfur-scented component, major leaks are much more noticeable. if we detect the scent of natural gas within our house, we should leave right once and call for help. the pipe that carries gasoline to our home is called a gas line (usually natural gas or propane). this fuel is necessary for running some appliances in the home, including the water heater, clothes dryer, oven/range, heaters, grill, and pool heaters. the supply pipe is often connected to the device by flexible steel tubing, and gas lines are typically built of black iron or copper pipe that goes through the wall or floor. gas pipes in residences frequently leak. the gas line leaks most frequently at the threaded fitting. the most frequent reasons for leaks include pipe corrosion, poor quality lines and fittings, faulty connection assembly, damaged pipe threads, and outdated valves [28]. here are five ways we may find gas leaks on our own [28]. a) smell: when processed for home use, mercaptan is added to naturally odorless natural gas to give it a strong odor that is frequently compared to sulfur or the smell of rotten eggs. (propane also has a strong smell.) we may occasionally smell natural gas when using our appliances; however, if the smell becomes overpowering, leave the house and call a professional for evaluation and repair. b) bubble test: if we think a gas line is leaking, we should mix water and liquid dish soap and use a sponge or cloth to apply the mixture to the pipe where the leak may be. if suds start to look like soap, we have a little leak. c) inaccurate pilot light: if the pilot light on our appliance keeps going out, there could be a leak in the gas line, which would disrupt the fuel supply. d) dead plants: there might be an underground gas leak if we observe an area of grass or plants in our yard that are dying for no apparent cause. e) in-home testing: online and at home improvement stores, there are many different electrical gas leak testers to choose from. depending on the cause, fixing a gas line leak may include tightening and resealing the fittings’ threads or completely replacing the damaged line. we should get in touch with a qualified plumber if we notice a leak since gas and other fuels are combustible. gas line leaks can be prevented, despite the fact that they could seem terrifying [29]. • hire a professional to install our gas appliances. • gas appliances should not be moved or jostled regularly. • double-check that all fittings are secure and sealed with sealant paste. abdullah et al. (2022): international journal of engineering materials and manufacture, 7(4), 95-102 98 • have a licensed plumber inspect our pipes once a year. due to the potential risk posed by the gases used in houses, it is crucial to seek the advice of experts who can maintain and repair our gas lines in a secure manner. 2.3 fire hazards fire hazards are workplace dangers that entail the presence of a flame, enhance the likelihood of an uncontrolled fire, or increase the severity of a fire if it occurs [28]. fire hazards include [29] flames, sparks, hot objects, flammable chemicals and acceleration of chemicals. the term fire hazards encompass a wide range of potential dangers. it encompasses anything that prevents fire protection materials or equipment from working properly, as well as anything that prevents people from acting in a fire-safe manner. a barrier that prevents safe escape and a malfunctioning sprinkler system, for example, are both considered fire dangers. this is because a facility’s level of risk influences both the likelihood of a fire and the severity of the potential harm caused by a fire if one does occur. our concept of what constitutes a fire danger has evolved through time; in general, cultures around the world have been less tolerant of fire hazards, and as a result, a greater number of situations are now considered hazardous. some common fire hazards include [31]: a) candles and other open flames, chimneys that concentrate creosote, combustible storage areas with insufficient protection, and combustibles near equipment that generates heat, flame, or sparks. b) cooking appliances – stoves, ovens, electrical wiring in poor condition, electrical systems that are overloaded, poorly maintained, or defective. c) electronic and electrical equipment and exterior cooking equipment – barbecue. d) heat-generating devices that use combustible materials. e) wood stove fireplaces, along with flammable liquids and particulates, are not cleaned properly or regularly. f) flammable solvents are placed in enclosed trash cans as well as thermal devices including open fires, bamboo cookers, heaters, water heaters, electric baseboard heaters, and liquid fuel. g) kitchenware, along with household appliances, hair straighteners, clothes dryers, fridges, chillers, heaters, and kitchen fires caused by unattended cooking, grease fires, and chip pan fires. h) leaking/faulty batteries, personal ignition sources such as matches and lighters, as well as cigarettes. statistics from the bangladesh fire service and civil defense (bfscd) directorate, which oversees fire stations, show that in the years 2010, 2011, 2012, and 2013, respectively, 18.17 percent, 15.36 percent, 15.96 percent, and 16.14 percent of all reported fire incidences in bangladesh occurred in the greater dhaka district [31]. table 1 shows economic loss due to fire incidents in the greater dhaka districts [31]. table 1: economic loss due to fire incidents in the greater dhaka districts [31]. year no. of incidents loss (bdt in millions) 2010 2669 1470 2011 2422 960 2012 2794 2400 2013 2891 4070 figure 1 shows the average loss of fire incidents in millions bdt according to location (2011-2013) [31]. it is evident from figure 1 [31] that industrial land use experiences higher economic loss as a result of fire occurrences than any other land use category, with an average loss of bdt 0.6 million, for mixed uses, the loss is 0.5 million bdt, and for commercial, the loss is 0.3 million bdt. according to the graph, the average loss of property for all residential purposes (including both non-slum and slum areas) is bdt 0.15 million. however, the observed average loss is bdt 1.279 million only in slum regions, which is higher than the loss incurred in industrial land usage. slum areas in bangladesh refer to densely populated metropolitan regions marked by subpar housing and squalor. additionally, the study discovered that across all types of land uses, slum areas suffer the most economic losses as a result of fire events. figure 2 shows the distribution of sources of fire incidents according to structure type (2014) [31]. it is seen from the figure that in frequency of fire incidents one, two and three, there are 3%, 3.67% and 9.82% of gas line fire accidents, respectively. in a pacca structure, the two major sources of fire are an electric line and a gas line, however, in a kacha structure, 30 percent of the fire also comes from a cigarette and a stove in addition to an electric short circuit. kutcha constructions, the fire spreads quickly and results in a significant loss of property quickly [31]. 3. prevention of gas leakages in bangladesh the following section deals with the various techniques such as manual technique, algorithmic technique and modelling and simulation technique used for the prevention of gas leakages in bangladesh. https://en.wikipedia.org/wiki/gas_leak#cite_note-3 https://en.wikipedia.org/wiki/fire_safety#cite_note-3 effects of fire hazards due to leakage in gas circulation lines in bangladesh: a comprehensive review. 99 figure 1: average loss of fire incidents in millions according to location (2011-2013) [31]. figure 2: distribution of sources of fire incidents according to structure type (2014) [31]. 3.1 manual technique as a result, basements, particularly those in lower flats, are at risk in the event of a leak. small amounts of smells are added to household gases to help people comprehend how gas leaks. the smells make it simple to detect the gas. because odorants are filtered and the characteristic odor is lost when a gas leak occurs in underground gas piping and the gas rises through the ground to the surface, only a gas analyzer can detect the gas level in the air. the gas explosion is distinguished by the fact that the fire that created the explosion is also dampened at the time of the explosion. this means that after a gas explosion, there is usually no fire [11]. this is due to two factors: first, the explosion occurs quickly, preventing other objects in the room from catching fire, and the burning gas itself quickly dissipates. second, the room’s explosion creates such a high pressure that the flames are suppressed. the ensuing pressure is great enough to cause the weakest buildings to collapse, allowing the gases to escape. doors, windows, and shutters are installed in gas facilities in such a way that they open outwards and expel explosive gases, reducing the impact of explosions. in addition, lightweight panels are used for intermediate ceilings, and the number of glass surfaces is increased. if the same conditions exist in other locations or buildings where gas is used, the explosion’s consequences will be less severe. if there is a gas leak in the room but no contact with the source of ignition, a saturated combination (too much gas and too little oxygen) will form at some point, rendering the room non-flammable. alternatively, if the liquid level falls below the area being heated as a result of repeated venting, the tank construction can be overheated and weakened in that area [11]. if either of these events occurs, the container may explode violently, launching portions of the vessel at high speeds, while the discharged products may burn, posing a threat to anything close, including neighboring containers. lpg is 60.5 72 74.32 3 3.67 9.82 15 11 7 5 5 0.5 17 2 3 0 0 0.1 1 6 2 0 10 20 30 40 50 60 70 80 frequency of fire incidents (%) 1 frequency of fire incidents (%) 2 frequency of fire incidents (%) 3 percentage of fire incidents machine/wielding chemical reaction stove coil/candle cigarette gasline electrical abdullah et al. (2022): international journal of engineering materials and manufacture, 7(4), 95-102 100 a highly flammable gas made up of a mixture of propane and butane. it is an odorless gas to which ethanol has been added as a potent odorant to enable leak detection. lpg is now one of the most often utilized alternative fuels. lpg, lp gas, and autogas are some of the other names for liquefied petroleum gas [12]. this gas is often used to heat appliances, provide hot water, cook, and for a variety of other uses. due to the rising cost of gasoline and diesel, lpg is also employed as an alternative fuel in vehicles. some people with a poor sense of smell may or may not react to low levels of gas leakage. in this circumstance, gas leakage security systems have become vital for preventing gas leakage mishaps. a lot of research articles on gas leakage security systems have been published. in the literature, an embedded system for hazardous gas detection and alerting has been proposed. if the gas concentration exceeds the normal threshold, the alarm is immediately activated. in india, the bhopal gas catastrophe was an example of a gas leaking event. this was the world’s worst industrial gas leakage accident. not only is it critical to detect gas leaks, but it is also critical to halt them. this study presents a low-cost, high-precision system that not only detects gas leaks but also alerts (beeps), shuts down major power and gas supply, and sends an sms. a gsm module is used to deliver an sms to the user as an alert [31]. the mq-6 gas sensor was utilized to offer great accuracy. in industry, heating systems, home appliances, and cars, toxic and flammable gases are commonly used. combustible gases such as propane, ethane, butane, methane, and ethylene fall under this category. liquefied petroleum gas (lpg), commonly known as propane or butane, is often stored in liquid form in pressurized cylinders and vaporizes at room temperature [14]. a leak can produce an explosion if it ignites. as a result, gas leak detection has gotten a lot of attention in recent years, notably in the domains of safety, industry, the environment, and emission control. a traditional gas leak detection system uses on-site alarms to signal the presence of a leak. the typical leakage system has the disadvantage of being ineffective in the absence of a first-responder team on-site. as a result, a system to identify the leak and convey the information to the first response team via wireless media is required. in the absence of employees on-site, a leakage detection system that sends out a warning call or sms is more effective [31]. 3.2 algorithmic technique natural gas sensor, gsm module a microcontroller is connected to the fire sensors and will operate the entire system. two sensors are employed in this system, and four conditions are specified while programming these sensors. a gas sensor and a fire sensor are calibrated in the first and second steps using the reference value provided. if the sensor reading exceeds the setup reference value, the microcontroller will sound an alarm until the gas or fire is detected. the third condition report will be displayed on the lcd screen. in the fourth scenario, the gsm module will send a text message to the fire station advising them of a gas or fire detection on any specific floor. figure 3 shows an algorithm for detecting gas leakage [31]. firstly, gam module is to be started for detecting gas leakage. the system is queried for lpg or fire. if the system is answered as yes then it sends data to microcontroller and shows to display the result [32]. figure 3: algorithm for detecting gas leakage [32]. effects of fire hazards due to leakage in gas circulation lines in bangladesh: a comprehensive review. 101 3.3 modelling and simulation techniques considering the acrylic rectangular vessel in figure 4 that is 100 mm x 30 mm and 2 mm in dimension. a 40 khz ultrasonic sensor with a transmitter and receiver is mounted with a 10 mm gap on the chamber’s left side. both the transmitter and receiver are presumed to be 5 mm in size. the acoustic wave is transmitted by the transmitter, and it travels through the gas-filled chamber [33]. the wave reflects off the wall opposite and is picked up by the receiver. the acoustic wave’s time of flight varies with changes in gas density. utilizing software for finite elements, simulation was performed [33]. the signal needs to fly for 1270 microseconds in normal air to cover a distance of 200 mm across the gas medium. after that, the simulation was carried out by injecting sf6 gas into the vessel. sf6 gas density gradually increased. the signal’s time of flight was calculated for each density value. figure 5 narrates the change in flight time with rising gas density. the time the wave takes to travel rises with density, according to simulation data. the r2 value of 0.9 indicates that the reaction is linear [33]. figure 4: schematic of the proposed method for detection of gas leakage [33]. 4. conclusions the fire hazards caused by leakages in gas circulation lines are of great importance that results in a significant loss of wealth, lives and the environment. the risks of fire hazards can be reduced effectively through the use of new technologies and preventive measurements of the system. the aims of the paper is to review the effects of these fire hazards due to leakage in gas circulation lines in bangladesh. the following findings can be depicted in present research. a) in bangladesh during 2018-2019, the total gas distribution line in the titas gas system was measured as 13,138 km where the pressure-reducing system or gas riser was found as 1.2 million and the number of customers was found as 2.866 million. in the system, the number of fire accidents that occurred was 208 in the circulation system. because of connecting the illegal gas lines and poor maintenance of the system, bangladesh faces significant fire hazards every year. b) a result of 80 percent lower explosive limits (lel) or higher in a confined space is regarded as a grade 1 leak; result of 20 percent to 80 percent lower explosive limits (lel) in a confined space are regarded as grade 2 leaks, and result of less than 20 percent lower explosive limits (lel) in a confined space are regarded as grade 3 leaks. c) the leak can be noticed if an unexpected hissing sound can be heard emerging from just about any pipes or regions that may house gas pipelines. the course of most recent but still not distant, our sense of sight can assist us in identifying if there is a natural gas leak outside our building or around. if we detect bubbling in puddles or dead plants in otherwise favorable positions, there may be an outside leak. if any fuel appliances have quite a yellow flame instead of a blue flame, there may be an inside leak. since any of these leaks could result in an explosion or carbon monoxide poisoning, they have to be corrected quickly and immediately. d) a key undertaking to lessen the risk of fire is the detection of leaks, repairs needed on the gas risers, and measurement of fugitive gas. references [1] https://www.hsdl.org/?view&did=34510 glossary of wildland fire terminology (pdf). national wildfire coordinating group. [accessed on 20 february 2022] [2] 1. schmidt-rohr, k (2015). why combustions are always exothermic, yielding about 418 kj per mole of o2. j. chem. educ. 92 (12): 2094–99. bibcode:2015jched.92.2094s. doi: 10.1021/acs.scheme.5b00333. [3] 2. https://www.thoughtco.com/what-state-of-matter-is-fire-604300. [accessed on 20 february 2022] [4] 3. abedin, m. z., & karim, a. s. m. l. (2022). waste to energy technologies for municipal solid waste management in bangladesh: a comprehensive review. international journal of engineering materials and manufacture, 7(3), 78–88. https://doi.org/10.26776/ijemm.07.03.2022.02. https://www.hsdl.org/?view&did=34510 https://doi.org/10.1021%2facs.jchemed.5b00333 https://doi.org/10.1021%2facs.jchemed.5b00333 https://en.wikipedia.org/wiki/bibcode_(identifier) https://ui.adsabs.harvard.edu/abs/2015jched..92.2094s https://en.wikipedia.org/wiki/doi_(identifier) https://doi.org/10.1021%2facs.jchemed.5b00333 https://www.thoughtco.com/what-state-of-matter-is-fire-604300 https://doi.org/10.26776/ijemm.07.03.2022.02 abdullah et al. (2022): international journal of engineering materials and manufacture, 7(4), 95-102 102 [5] 4. morris, s. e.; moses, t. a. (1987). forest fire and the natural soil erosion regime in the colorado front range. annals of the association of american geographers. 77 (2): 245–54. doi: 10.1111/j.1467-8306. 1987. tb00156.x. [6] 5. j. a. j. gowlett; r. w. wrangham (2013). earliest fire in africa: towards the convergence of archaeological evidence and the cooking hypothesis. azania: archaeological research in africa. 48:1: 5–30. doi: 10.1080/0067270x.2012.756754. s2cid 163033909. [7] 6. kaplan, matt (2012). million-year-old ash hints at the origins of cooking. nature. doi: 10.1038/nature.2012.10372. s2cid 177595396. retrieved 25 august 2020. [8] 7. bowman, d. m. j. s.; et al. (2009). fire in the earth system. science. 324 (5926): 481–84. bibcode:2009sci 324.481b. doi: 10.1126/science.1163886. pmid 19390038. s2cid 22389421. [9] 8. https://abcnews.go.com/technology/early-humans-cooking-food-million-years-ago/story?id=16080804 (accessed on 20 february 2022). [10] 9. francesco berna; et al. (may 15, 2012). microstratigraphic evidence of in situ fire in the acheulean strata of wonderwork cave, northern cape province, south africa. pnas. 109 (20): e1215–e1220. doi: 10.1073/pnas.1117620109. pmc 3356665. pmid 22474385. [11] https://news.climate.columbia.edu/2011/11/16/farmers-flames-and-climate-are-we-entering-an-age-ofmega-fires/[accessed on 20 february 2022] [12] www.napalm.globalsecurity.org. [accessed on 01 october 2022] [13] https://www.iea.org/data-and-statistics/charts/total-primary-energy-supply-by-fuel-2002-and-2015. [accessed on 20 february 2022] [14] https://www.nifc.gov/nicc/administrative/nmac/correspond/fireopsplan.pdf. [accessed on 20 february 2022] [15] https://gfmc.online/iffn/country/gb/gb_1.html. [accessed on 20 february 2022] [16] https://smokeybear.com/en/about-wildland-fire/benefits-of-fire/prescribed-fires. [accessed on 20 february 2022] [17] https://firecomm.gov.mb.ca/safety_education.html. [accessed on 20 february 2022] [18] ward, michael (march 2005). fire ward, michael (march 2005). officer: principles and practice. jones & bartlett learning. isbn 9780763722470. retrieved march 16, 2019. [19] baars, hans; smulders, andre; hintzbergen, kees; hintzbergen, jule (2015-04-15). foundations of information security based on iso27001 and iso27002 (3 rd revised.). van haren. isbn 9789401805414. [20] https://www.cia.gov/the-world-factbook/about/archives/ (accessed on 20 february 2022). [21] http://naturalgas.org/overview/background/[accessed on 20 february 2022] [22] https://www.mudomaha.com/blog/why-does-natural-gas-smell-rotteneggs#:~:text=natural%20gas%20is%20an%20efficient,or%20hydrogen%20sulfide%20like%20odor. [accessed on 20 february 2022] [23] https://www.eia.gov/energyexplained/natural-gas/ [accessed on 20 february 2022] [24] https://www.tbsnews.net/bangladesh/energy/62-titas-gas-risers-leaky-130294. [accessed on 15 october 2022] [25] trevor a. kletz (2001). learning from accidents. gulf professional publishing. isbn 075064883x. [26] stocker, thomas (ed.). climate change 2013: the physical science basis: working group i contribution to the fifth assessment report of the intergovernmental panel on climate change. new york. isbn 978-110741-532-4. oclc 881236891. [27] https://www.govtrack.us/congress/bills/107/hr3609/text. [accessed on 20 february 2022] [28] https://www.premierservicecompany.com/gas-line-leak-heres-what-you-need-to-know/. [accessed on february 20, 2022] [29] https://www.safeopedia.com/definition/739/fire-hazards. [accessed on february 20, 2022] [30] https://en.wikipedia.org/wiki/fire_safety. [accessed on february 20, 2022]. [31] rahman tishi, t., islam, i. urban fire occurrences in the dhaka metropolitan area. geo-journal 84, 1417– 1427 (2019). https://doi.org/10.1007/s10708-018-9923-y. [32] https://www.researchgate.net/publication/316220622_detection_of_fire_and_gas_leakage_in_ industry_to_ensure_safety_condition. [accessed on february 20, 2022] [33] das, s. d., akram, k. j., biswal, g. r., & islam, t. (2021, january). a high precision cost-effective ultrasonic sensor for detection of gas leakage in gas insulated switchgear. in 2021 international conference on sustainable energy and future electric transportation (sefet) (pp. 1-6). ieee. https://en.wikipedia.org/wiki/doi_(identifier) https://doi.org/10.1111%2fj.1467-8306.1987.tb00156.x https://doi.org/10.1111%2fj.1467-8306.1987.tb00156.x https://en.wikipedia.org/wiki/doi_(identifier) https://doi.org/10.1080%2f0067270x.2012.756754 https://en.wikipedia.org/wiki/s2cid_(identifier) https://api.semanticscholar.org/corpusid:163033909 https://www.nature.com/news/million-year-old-ash-hints-at-origins-of-cooking-1.10372 https://en.wikipedia.org/wiki/doi_(identifier) https://doi.org/10.1038%2fnature.2012.10372 https://en.wikipedia.org/wiki/s2cid_(identifier) https://api.semanticscholar.org/corpusid:177595396 https://en.wikipedia.org/wiki/bibcode_(identifier) https://ui.adsabs.harvard.edu/abs/2009sci...324..481b https://ui.adsabs.harvard.edu/abs/2009sci...324..481b https://en.wikipedia.org/wiki/doi_(identifier) https://doi.org/10.1126%2fscience.1163886 https://en.wikipedia.org/wiki/pmid_(identifier) https://pubmed.ncbi.nlm.nih.gov/19390038 https://en.wikipedia.org/wiki/s2cid_(identifier) https://api.semanticscholar.org/corpusid:22389421 https://abcnews.go.com/technology/early-humans-cooking-food-million-years-ago/story?id=16080804 https://www.ncbi.nlm.nih.gov/pmc/articles/pmc3356665 https://www.ncbi.nlm.nih.gov/pmc/articles/pmc3356665 https://en.wikipedia.org/wiki/doi_(identifier) https://doi.org/10.1073%2fpnas.1117620109 https://en.wikipedia.org/wiki/pmc_(identifier) https://www.ncbi.nlm.nih.gov/pmc/articles/pmc3356665 https://en.wikipedia.org/wiki/pmid_(identifier) https://pubmed.ncbi.nlm.nih.gov/22474385 http://www.napalm/ https://www.iea.org/data-and-statistics/charts/total-primary-energy-supply-by-fuel-2002-and-2015 https://www.nifc.gov/nicc/administrative/nmac/correspond/fireopsplan.pdf https://gfmc.online/iffn/country/gb/gb_1.html https://smokeybear.com/en/about-wildland-fire/benefits-of-fire/prescribed-fires https://firecomm.gov.mb.ca/safety_education.html https://books.google.com/books?id=yxt5aw6bjiuc&q=purposely+starting+fire+arson+crime+most+jurisdictions&pg=pa349 https://en.wikipedia.org/wiki/isbn_(identifier) https://en.wikipedia.org/wiki/special:booksources/9780763722470 https://books.google.com/books?id=l6epcgaaqbaj&q=fire+insurance+can+mitigate+the+financial+impact+of+fire&pg=pa33 https://books.google.com/books?id=l6epcgaaqbaj&q=fire+insurance+can+mitigate+the+financial+impact+of+fire&pg=pa33 https://en.wikipedia.org/wiki/isbn_(identifier) https://en.wikipedia.org/wiki/special:booksources/9789401805414 https://www.mudomaha.com/blog/why-does-natural-gas-smell-rotten-eggs#:~:text=natural%20gas%20is%20an%20efficient,or%20hydrogen%20sulfide%20like%20odor https://www.mudomaha.com/blog/why-does-natural-gas-smell-rotten-eggs#:~:text=natural%20gas%20is%20an%20efficient,or%20hydrogen%20sulfide%20like%20odor https://en.wikipedia.org/wiki/isbn_(identifier) https://en.wikipedia.org/wiki/special:booksources/075064883x https://books.google.com/books?id=o4gabqaaqbaj https://books.google.com/books?id=o4gabqaaqbaj https://en.wikipedia.org/wiki/isbn_(identifier) https://en.wikipedia.org/wiki/special:booksources/978-1-10741-532-4 https://en.wikipedia.org/wiki/special:booksources/978-1-10741-532-4 https://en.wikipedia.org/wiki/oclc_(identifier) https://www.worldcat.org/oclc/881236891 https://www.govtrack.us/congress/bills/107/hr3609/text https://www.premierservicecompany.com/gas-line-leak-heres-what-you-need-to-know/ https://www.safeopedia.com/definition/739/fire-hazards https://en.wikipedia.org/wiki/fire_safety https://doi.org/10.1007/s10708-018-9923-y https://www.researchgate.net/publication/316220622_detection_of_fire_and_gas_leakage_in_industry_to_ensure_safety_condition https://www.researchgate.net/publication/316220622_detection_of_fire_and_gas_leakage_in_industry_to_ensure_safety_condition international journal of engineering materials and manufacture (2023) 8(1) 1-12 https://doi.org/10.26776/ijemm.08.01.2023.01 odiwo h. a , bello k.a. a , abdulwahab m. a,b , adebisi a.a. a,b , abdullahi u c , dodo r.m. a , maleque m.a. d and suleiman m.u. a a department of metallurgical and materials engineering, ahmadu bello university, zaria-nigeria. b department of metallurgical and materials engineering, air force institute of technology, kaduna-nigeria. c centre for energy research and training, ahmadu bello university, zaria-nigeria. d department of manufacturing and materials engineering, international islamic university malaysia, kuala lumpur, malaysia e-mail: hammedodiwo@gmail.com reference: odiwo et al. (2023). study on the optimization of surface modification processing of sicp and tribological properties of aa6061-sicp based composites. international journal of engineering materials and manufacture, 8(1), 1-12. study on the optimization of surface modification processing of sicp and tribological properties of aa6061-sicp based composites odiwo h., bello k.a., abdulwahab m., adebisi a.a., abdullahi u., dodo r.m., maleque m.a. and suleiman m.u. received: 23 november 2022 accepted: 04 january 2023 published: 20 january 2023 publisher: deer hill publications © 2023 the author(s) creative commons: cc by 4.0 abstract the unique property combination of al/sicp based composites make them very attractive for applications in automotive and aerospace industries. the choice of composite materials for these applications is directly influenced by their inherent properties which are a function of the processing route employed. like other processing parameters, surface modification treatment of sicp can play a major role in determining the properties of al/sicp composites. in this study, the effects of sic reinforcement (wt%) fractions (srf), surface oxidation temperature (sot) and preheating temperature (pt) parameters on the wear and friction properties of stir-cast al-sicp based composite were investigated. experimental data and models are generated and analyzed based on a three-factors-five-level central composite design (ccd) and analysis of variance (anova). the empirical models developed for wear rate and coefficient of friction (cof) considering the pre-processing parameters adequately predicts the al-sicp properties with the silicon carbide reinforcement (wt%) fraction emerged as the most influencing factor. the goal of the optimization process is to minimize both wear rate and cof. for wear rate, srf at 44.49 % contribution had the most influence on wear rate, while sot and pt had 0.65 % and 1.03 % influence on wear rate respectively. for cof, srf also showed highest influence of 35.48 % on cof, while sot and pt had 0.047% and 2.66% influence on cof respectively. from the optimization analysis, the set of conditions that simultaneously optimizes both wear rate and cof are 10% sic weight (sw), 1234°c surface oxidation temperature (sot), and 376.2°c preheat temperature (pt). the resulting responses at this optimized condition are minimum wear rate of 0.11 mm 3 /m and cof of 0.11 with a confidence and desirability level of 1. keywords: aluminium-silicon carbide composite, surface oxidation, preheat temperature, central composite design. 1 introduction conventional monolithic aluminium alloys fail to meet the rising demand for high performance structural applications due to their low strength and low wear resistance properties (moses et al., 2016). in the last few decades, the use of ceramic particles in the strengthening of aluminium has been gaining significant popularity (alten et al., 2019). ceramic particulates like sic, b4c, tic, wc, zro2 and al2o3 are the commonly used reinforcements to fabricate aluminium matrix composites, (amcs), (nagaral et al., 2016). as a result of its excellent thermal conductivity, good corrosion resistance, high modulus and strength, low cost, availability, and suitable compatibility with aluminium alloys, silicon carbide (sic) is the most commonly used ceramic material for composite reinforcement. they have emerged the most preferred materials for composite production as indicated in figure 1 because they are well suited for excellent heat and wear resistance applications (bobic et al., 2010; adebisi et al., 2016; odiwo et al., 2021). silicon carbide reinforced aluminium matrix composites (amcs) have been widely used in automobile and aerospace applications for production of engine parts such as piston, connecting rod and brake drum where sliding contact is important due to their low density, high strength, high stiffness, good corrosion resistance and high wear resistance properties in comparison with monolithic aluminium alloys. excessive wear of the mating components during operation leads to catastrophic failures (nagaral et al., 2016; verma & khvan, 2019). mailto:hammedodiwo@gmail.com odiwo et al. (2023): international journal of engineering materials and manufacture, 8(1), 1-12 2 figure 1: industrial usage of reinforcement materials (odiwo et al., 2021) many techniques are available for the fabrication of aluminium/silicon carbide particulate composites such as spray deposition, powder metallurgy, infiltration technique, squeeze casting and stir casting. however, stir casting is one of the most commonly used method to fabricate aluminium matrix composites because of its simplicity, ease of production of complex casting, mass production possibility and it is economical (ramesh et al., 2010). the main factors controlling the properties of mmcs fabricated using stir casting techniques include reinforcement distribution, wetting of reinforcement by the matrix aluminium alloy, reactivity at the reinforcement / matrix interface and porosity in the solidified casting. these factors are directly influenced by the casting processing parameters such as processing temperature, stirring time, stirring speed, preheat temperature, blade angle, melt temperature, particle feed rate, etc. when these parameters are well controlled, the factors are significantly improved and al-sicp composites of better properties are produced (adebisi et al., 2017; verma & khvan, 2019; adediran et al., 2021). adebisi and ndaliman (2015) studied the influence of process parameters (reinforcement fraction, stirring speed, processing temperature and processing time) on wear and density properties of aa6061-sicp composites produced using stir casting. stirring speed and processing time are reported as the most influential parameters and were able to obtain a wear mass loss as low as 1 x 10 -3 g and density value achieved as high as 2.780g/mm 3 using the optimum parametric combination of 14 wt.% reinforcement fraction, 460 rpm stirring speed, 820 °c processing temperature and 150 seconds processing time. umanath et al., (2013) studied the wear behavior of al6061/sic/al2o3 hybrid metal matrix composites with volume fraction, applied load, rotational speed and counter-face hardness as the process parameters. among the four parameters, volume fraction and counter-face hardness had the most influence on reduction of wear rate of the hybrid composites. rana et al., (2017) developed a mathematical model to study the influence of process parameters (casting temperature, stirrer speed, and weight percent of reinforcement) on hardness of aa5083/nano-sic composite fabricated by stir casting. optimum hardness of 19.4 hbn was obtained using the optimized process parameters 2wt.% of nano-sic, 760 °c casting temperature and 550 rpm stirrer speed generated from the model. the common practice of evaluating material integrity is done by studying one factor at a time. such practice is unable to evaluate the material effectively since the study did not include the interactions amongst the factors. whether the interaction effect is significant or not, each of the factors contribute to material integrity. along these lines, it is important to utilize the design of experiments (doe) in the investigation because of its capacity in estimating the connections between the factors (ahmad et al., 2020). central composite design (ccd) of response surface methodology (rsm) is a very efficient method in reducing the number of experiments with a large number of factors and levels. it provides high quality predictions in studying linear, quadratic and interaction effects of factors influencing a response. ccd is also capable of achieving the optimum conditions required to attain the best characteristic properties (montgomery, 2013; myers et al., 2016). therefore, the aim of this study is to investigate the influence of particle pre-processing parameters surface oxidation and preheat temperature of varying sicp addition on the tribological properties of al-sicp composites. 2 experimental details 2.1 materials and method aa6061 aluminium alloy used as the matrix was produced using stir casting method and the composition of the ascast alloy is given in table 1. silicon carbide (sicp) powder of 76 µm was employed to reinforce the aluminium alloy. the properties of the matrix aluminium (aa6061) alloy and the silicon carbide (sicp) powder are highlighted in table 2. 1 1 3.5 2 1 19.5 1 2 1 3 1 2 10 0 5 10 15 20 25 sic-gr(ni) si tic tib₂ tib sic sib₆ gr cr₃c₂ c beo b₄c al₂o₃ relative usage of reinforcement materials in mmc industries r e in fo rc e m e n t m a te ri a l study on the optimization of surface modification processing of sicp and tribological properties of aa6061-sicp… 3 table 1: composition of as-cast aa6061 alloy si cu mn mg cr zn ti al 0.62 0.22 0.03 0.84 0.22 0.10 0.10 balance table 2: properties of aa6061 alloy and sicp (adebisi et al., 2017) property unit aa6061 sicp density g/cm 3 2.7 3.22 melting point °c 660 2973 coefficient of thermal expansion µm/m°c 23.4 4 thermal conductivity w/mk 166 126 young’s modulus gpa 70 410 sic particles (sicp) were exposed to surface oxidation and preheating pretreatment operations prior to composite production. for the surface oxidation pretreatment, the sicp are heated to temperatures above 1000 °c so that thin layer of silica (sio2) is formed on its surface. sio2 layer acts as a barrier preventing the direct contact between sicp and aluminium alloy during composite production (khalid et al., 2013). the sicp samples to be oxidized were weighed in alumina crucible using the 0.0001g precision weighing balance and then placed in an electric resistance furnace already set to the temperature required for surface oxidation. five samples of the measured sicp were pretreated at high temperature of 1100 °c, 1150 °c, 1200 °c, 1250 °c and 1300 °c respectively. the furnace was set to heat the samples at a heating rate of 10 °c/min. after attainment of the desired temperatures, sicp samples were held at each temperature for 2hrs and then allowed to cool in air (vantrinh et al., 2018 and lee et al., 2020). preheating of oxidized-sicp at temperatures relatively much lower than the oxidation temperatures is a process performed to assist in obtaining increased wettability between the molten aluminium alloy and the oxidized-sicp during composite production. after weighing the oxidized-sicp samples, the graphite crucible was placed in the electric resistance furnace and heated to temperature of 300 °c, 350 °c, 400 °c, 450 °c and 500 °c based on the experimental requirement in the central composite design matrix. after reaching the required temperature, sample were allowed to homogenize for 30 minutes in the furnace and then added into the molten alloy. melting of the aa6061 alloy was achieved using the copular furnace. the dross (solid mass of impurities floating on molten metal) formed was skimmed off to obtain higher purity of the aa6061 alloy. afterwards, the oxidizedsicp were preheated at the required temperature (300 °c, 350 °c, 400 °c, 450 °c or 500 °c) for 30 minutes and then carefully added into the vortex of the molten alloy created mechanical stirring. the mixture was maintained at a temperature of about 710 °c and further stirred for 2 minutes at a stirring speed of 500 rpm using a stainless steel stirrer before being poured into the ø20 mm by 110 mm prepared cylindrical sand mold. the weight fraction of the sicp was distributed over 5 levels with 0 and 10 % as the minimum and maximum (i.e. 0, 2.5, 5, 7.5 and 10 %). this process is conducted for each of the experimental runs considering the process parameters as suggested by the design plan. after casting, the aa6061/oxidized-sicp composite test specimen were prepared for wear measurement. 2.2 wear and friction test the wear and friction property of the test samples was tested using a ball-on-disk tribometer according to astm g99-95 standard. after machining the as-cast composite samples to ø15 mm x 5 mm dimension, the samples were subjected to metallographic grinding up to p600 grit, cleaned with acetone, dried and weighed using analytical balance with the precision of 0.0001 g. during the wear test, a stainless steel ball of 6 mm diameter was used to as a static partner over a 5 mm radius on the surface of the rotating samples. the load, sliding speed and sliding distance of 8 n, 10 cm/s and 30 m respectively were applied at room temperature, relative humidity of 55 % and a test duration of 30 minutes for all the samples. the value coefficient of friction was automatically generated by the ballon-disk tribometer during the wear test. after the wear test, the samples were cleaned using acetone, dried and weighed. the wear rats was calculated from the weight loss data obtained using the equation below: 𝑤𝑟 = 𝑚𝑎𝑠𝑠 𝑙𝑜𝑠𝑠 𝑠𝑙𝑖𝑑𝑖𝑛𝑔 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒⁄ (1) 2.3 experimental design the experiments were planned based on ccd method in design expert 10 software. it utilized 3-factor-5-level design scheme as shown in table 3. the factors are sic reinforcement fraction (srf), surface oxidation temperature (sot), and preheat temperature (pt). table 3: factors and levels for the ccd experimental design plan factor symbol level -2 -1 0 1 2 sic reinforcement fraction (srf) wt.% 0 2.5 5 7.5 10 surface oxidation temperature (sot) °c 1100 1150 1200 1250 1300 preheat temperature (pt) °c 300 350 400 450 500 odiwo et al. (2023): international journal of engineering materials and manufacture, 8(1), 1-12 4 the ccd experimental design plan consist of 2 k + 2k + 6 runs, where k = 3; that is, the number of input factors. the design has 8 factorial points (2 k ), 6-star points (2k) and 6 central runs to make up a total of 20 experimental runs, i.e. 2 3 + 2(3) + 6 = 8+6+6 = 20 runs. the experimental run involving only the as-cast aa6061 alloy is excluded from the design since the alloy did not require pretreated sic reinforcement particles. the experimental outcome is presented in table 4. table 4: design matrix and responses for oxidized-sicp reinforced aa6061 matrix composite factors responses experimental run a: sic reinforcement fraction (wt.%) b: surface oxidation temperature (°c) c: preheat temperature (°c) wear rate (mm 3 /m) cof (µ) 1 7.5 1150 350 0.0198 0.670 2 2.5 1150 350 0.042 0.787 3 5 1200 400 0.0272 0.713 4 5 1200 300 0.0321 0.754 5 5 1200 400 0.0284 0.715 6 5 1100 400 0.0321 0.748 7 2.5 1250 350 0.0407 0.766 8 2.5 1250 450 0.037 0.763 9 5 1200 400 0.0272 0.698 10 5 1300 400 0.0309 0.731 11 5 1200 400 0.0272 0.690 12 5 1200 400 0.0333 0.762 13 10 1200 400 0.0111 0.339 14 7.5 1250 350 0.0173 0.495 15 5 1200 400 0.0296 0.717 16 5 1200 500 0.0247 0.679 17 2.5 1150 450 0.0432 0.768 18 7.5 1150 450 0.0185 0.629 19 7.5 1250 450 0.016 0.345 3 results and discussion 3.1 characterization of as-cast aa6061 alloy the sem micrograph of the as-cast aa6061alloy in figure 2 (a) reveals the structure of the eutectic phase containing mg2si in α-aluminium matrix. the mg and si in the aa6061 alloy are present as a solid solution phase in the grains and along the grain-boundaries. the prominent peaks corresponding to aluminium, magnesium and silicon in the aa6061 alloy is confirmed by the energy dispersive spectroscopy (eds) spectra shown in figure 2 (b). aluminium is observed to have the highest count than other elements present. (a) (b) figure 2: (a) sem micrograph and (b) eds of as-cast aa6061 alloy study on the optimization of surface modification processing of sicp and tribological properties of aa6061-sicp… 5 3.2 characterization of as-received and oxidized-sicp sem-eds was utilized for the characterization of the as-received sicp. the sem micrograph of the as-received sicp in figure 3 (a) shows the surface of the powder to be very rough with its edges appearing very sharp. eds spectra in figure 3 (b) majorly confirmed the presence of silicon and carbon in the particles. when the as-received sicp is compared to the 1100 °c-oxidized-sicp sample in figure 4, the surface roughness of the 1100 °c-oxidized-sicp is observed to be significantly lower than that of the former. this reduction in surface roughness can be attributed to the thin sio2 layer formed on the surface of the sicp during surface oxidation treatment which resulted in surface refinement. (a) (b) figure 3: (a) sem micrograph and (b) eds of as-received 76 µm sicp figure 4: surface morphology of 1100 °c pre-oxidized sicp the as-received and 1100 °c-oxidized-sicp samples were further characterized using x-ray diffraction (xrd) phase analysis. the xrd spectrum in figure 5 confirmed the presence of sic phases in the as-received sic powder analyzed. the spectrum shows the extensive distribution of sic phases between 30° and 80° with high peaks observed at 35.72°, 53.93°, 57.54° and 60.22° on the 2θ axis. from the xrd analysis of the 1100 °c-oxidized-sicp sample in figure 6, the presence of silicon dioxide (sio2) coating layer on the sicp was further confirmed by the sio2 phases observed at diffraction peaks of 22.20°, 31.04°, 31.83° and 32.50° along the 2θ axis. odiwo et al. (2023): international journal of engineering materials and manufacture, 8(1), 1-12 6 figure 5: xrd spectrum of as-received sicp figure 6: xrd spectrum of 1100 °c-oxidized-sicp 3.3 mathematical model development for model development, the mathematical relationship between the response and the input factors is expressed by the second order polynomial in eqn 2: from the equation, y represents the response, xi and xj are the equation value of the factors, β0 is the constant, βi, βj and βij are linear, interaction and quadratic end coefficient respectively, and k is the number of the factors. the experimental results generated after conducting the runs were analyzed using analysis of variance (anova) to confirm the adequacy and validity of the developed model considering the significant model terms. the adequacy and validity is ascertain by confirming the significant terms with p values < 0.05 while model terms with p values > 0.05 are considered insignificant (di lio et al., 2020: adediran et al., 2021). 𝑌 = 𝛽0 + ∑ 𝛽𝑖 𝑘 𝑖=1 𝑋𝑖 + ∑ 𝛽𝑖𝑖 𝑘 𝑖=1 𝑋𝑖 2 + ∑ ∑ 𝛽𝑖𝑗 𝑘 𝑗≥1 𝑘 𝑖=1 𝑋𝑖 𝑋𝑗 + ∈ (2) study on the optimization of surface modification processing of sicp and tribological properties of aa6061-sicp… 7 3.4 model for wear rate fit summary statistics of the model for wear rate is shown in table 5. the fit summary presents the models to fit experimental data into appropriate model equations which can be first order or linear, second order or quadratic and cubic. from the table, the suggested polynomial for wear rate with f-value of 23.29 at p-value ≤ 0.0001 is significant and quadratic. table 5: fit summary statistics for wear rate source sum of squares df mean square f value p-value (prob > f) mean 30238.63 1 30238.63 linear 4443.25 3 1481.08 39.91 < 0.0001 2fi 22.89 3 7.63 0.17 0.9136 quadratic 472.83 3 157.61 23.29 0.0001 suggested cubic 25.42 4 6.35 0.90 0.5295 aliased residual 35.49 5 7.10 total 35238.51 19 1854.66 analysis of variance (anova) for wear rate carried out at 5 % significance level is presented in table 6. it is observed from the table that the model is significant with a p-value of 0.0001 which is less than 0.05 and f-value of 141.07. values of prob > f less than 0.0500 indicate model terms are significant. in this case, a, b, c and a 2 are statistically significant model terms since their p-values are less than 0.05, while, ab and b 2 are insignificant terms retained in the anova because they help in reducing the model terms of the input factors (a, b & c) to their present p-value. other model terms ac, bc and c 2 were removed for model reduction. furthermore, the p-value of the lack of fit which corresponds to 0.6647 is greater than 0.05 indicating that the lack of fit is non-significant which is desirable for model adequacy. table 6: analysis of variance for wear rate source sum of squares df mean square f value p-value (prob > f) model 4929.99 6 821.66 141.07 < 0.0001 significant a-sic reinforcement fraction 2224.60 1 2224.60 381.94 < 0.0001 b-surface oxidation temp 32.50 1 32.50 5.58 0.0359 c-preheat temp 51.51 1 51.51 8.84 0.0116 ab 15.42 1 15.42 2.65 0.1297 a 2 440.56 1 440.56 75.64 < 0.0001 b 2 17.77 1 17.77 3.05 0.1062 residual 69.89 12 5.82 lack of fit 34.40 7 4.91 0.69 0.6829 not significant pure error 35.49 5 7.10 cor total 4999.88 18 also, the difference between the predicted r 2 (0.9532) and adjusted r 2 (0.9790) of the model is less than 0.2, which establishes the reasonable agreement required for model adequacy. the model equation developed for the prediction of wear rate for any given level of each of the process parameters in the experiment is presented in equations 3. 1 𝑤𝑒𝑎𝑟 𝑟𝑎𝑡𝑒⁄ = − 429.02212 − 16.52776 𝑥 𝑆𝑅𝐹 + 0.76392 𝑥 𝑆𝑂𝑇 + 0.03588 𝑥 𝑃𝑇 + 0.01110 𝑥 𝑆𝑅𝐹 𝑥 𝑆𝑂𝑇 + 0.94905 𝑥 𝑆𝑅𝐹2 − 3.29557𝐸 − 004 𝑥 𝑆𝑂𝑇2 (3) equation 4 is used to identify the relative impact of the processing parameters by comparing their coefficients. from the equation, it is concluded that the process parameter with the most influence on wear rate is sic reinforcement fraction (srf). srf had 44.49 % influence on wear rate, while sot and pt had 0.65 % and 1.03 % influence on wear rate respectively. 1 𝑤𝑒𝑎𝑟 𝑟𝑎𝑡𝑒⁄ = +35.18630 + 15.72190 𝑥 𝐴 + 1.42521 𝑥 𝐵 + 1.79422 𝑥 𝐶 + 1.38812 𝑥 𝐴𝐵 + 5.93159 𝑥 𝐴 2 − 0.82389 𝑥 𝐵2 (4) odiwo et al. (2023): international journal of engineering materials and manufacture, 8(1), 1-12 8 3.4.1 influence of pre-processing parameters on wear rate from the 3-d surface and 2-d contour plots in figure 7 (a) and (b), the influence of srf & sot on wear rate is illustrated. the lowest wear rate was observed at 10 % silicon carbide weight and 1300 °c surface oxidation temperature. wear rate decreased with increasing sic reinforcement fraction (jafari et al., 2018) at all surface oxidation temperatures. at constant silicon carbide weight, the wear rate at high surface oxidation temperature is lower than those at low oxidation temperature. this implies that silicon carbide weight imposes more influence on the wear resistance property of the composites than surface oxidation temperature as described using equation 4. (a) (b) figure 7: (a) 3-d surface plot, and (b) 2-d contour plot showing the variation of wear rate with silicon carbide reinforcement fraction and surface oxidation temperature 3.5 model for coefficient of friction (µ) fit summary statistics of the model for coefficient of friction is shown in table 7. from the table, the suggested quadratic polynomial for coefficient of friction has f-value of 3.54 at significant p-value of ≤ 0.0612. analysis of variance (anova) for coefficient of friction carried out at 5 % significance level is presented in table 8. from the table, it is observed that the model is significant with a p-value of 0.0001 which is less than 0.05 and f-value of 42.42. a, c, ab, a 2 and a 2 b are statistically significant model terms since their p-values are less than 0.05, while, b is an insignificant model term. other model terms ac, bc, b 2 and c 2 were removed for model reduction. furthermore, the p-value of the lack of fit which corresponds to 0.1561 is greater than 0.05 indicating that the lack of fit is nonsignificant which is desirable for model adequacy. also, the difference between the predicted r 2 (0.8179) and adjusted r 2 (0.9325) of the model is less than 0.2, which establishes a reasonable agreement as required for model adequacy. table 7: fit summary statistics for coefficient of friction source sum of squares df mean square f value p-value (prob >f) mean 8.58 1 8.58 linear 0.25 3 0.082 16.13 < 0.0001 2fi 0.028 3 9.362e-003 2.34 0.1244 quadratic 0.026 3 8.646e-003 3.54 0.0612 suggested cubic 0.019 4 4.713e-003 7.54 0.0240 aliased residual 3.127e-003 5 6.254e-004 total 8.90 19 0.47 equation 5 is the model equation developed for the prediction of coefficient of friction (µ) for any given level of each of the process parameters in the experiment. the relative impact of processing parameters on coefficient of friction is identified by comparing their coefficients using equation 6. from the equation, it is concluded that the process parameter with the most influence on cof is silicon carbide reinforcement fraction (srf). srf had 35.48 % influence on cof, while sot and pt had 0.047 % and 2.66 % influence on cof respectively. µ = +3.85180 − 1.61768 𝑥 𝑆𝑅𝐹 − 2.43000e − 003 𝑥 𝑆𝑂𝑇 − 4.53750e − 004 𝑥 𝑃𝑇 + 1.37100e − 003 𝑥 𝑆𝑅𝐹 𝑥 𝑆𝑂𝑇 + 0.20929𝑥 𝑆𝑅𝐹2 − 1.80400e − 004 𝑥 𝑆𝑅𝐹2 𝑥 𝑆𝑂𝑇 (5) µ = +0.71 − 0.11 𝑥 𝐴 − 4.25e − 003 𝑥 𝐵 − 0.023 𝑥 𝐶 − 0.054𝑥 𝐴𝐵 − 0.045 𝑥 𝐴2 − 0.056 𝑥 𝐴2𝐵 (6) study on the optimization of surface modification processing of sicp and tribological properties of aa6061-sicp… 9 table 8: analysis of variance for coefficient of friction source sum of squares df mean square f value p-value (prob > f) model 0.31 6 0.051 42.42 < 0.0001 significant a-sic reinforcement fraction 0.11 1 0.11 92.22 < 0.0001 b-surface oxidation temp 1.445e-004 1 1.445e-004 0.12 0.7351 c-preheat temp 8.236e-003 1 8.236e-003 6.83 0.0226 ab 0.023 1 0.023 19.44 0.0009 a 2 0.025 1 0.025 21.07 0.0006 a 2 b 0.013 1 0.013 10.55 0.0070 residual 0.014 12 1.205e-003 lack of fit 0.011 7 1.619e-003 2.59 0.1561 not significant pure error 3.127e-003 5 6.254e-004 cor total 0.32 18 3.5.1 influence of pre-processing parameters on cof from the 3-d surface and 2-d contour plots shown in figure 8 (a) and (b) respectively, influence of sic reinforcement fraction (srf) & surface oxidation temperature (sot) on coefficient of friction (µ) can be observed. the lowest coefficient of friction was observed at 10 % silicon carbide weight and 1300 °c surface oxidation temperature. at silicon carbide weight above 6.7 % and surface oxidation temperatures above 1150 °c, the coefficient of friction was observed to be decreasing. (a) (b) figure 8: (a) 3-d surface plot, and (b) 2-d contour plot showing the variation of coefficient of friction with silicon carbide weight and surface oxidation temperature 3.6 surface characteristics of worn samples the surface characteristics of worn aa6061/oxidized-sicp composite samples with the minimum and maximum wear rates were investigated with the unreinforced aa6061 alloy using optical microscopy. for the unreinforced aa6061 alloy shown in figure 9 (a), the wear scars reveal extensive plastic deformation producing deeper micro-cutting on the worn surface indicating adhesive wear. this is attributed to the lack of adequate strength by the alloy to overcome the applied load exerted by the static partner (stainless steel ball). figure 9 (b) shows the aa6061/2.5wt.% oxidizedsicp composite (experiment run 17) which had the highest wear loss of all the composite samples tested. from the micrograph, it can be observed that the sample has similar wear surface characteristics to the unreinforced aa6061 alloy but exhibited mild adhesive marks and craters on its worn surface. from the micrograph of aa6061/10wt.% oxidized-sicp composite sample (experiment run 13) which had the least wear rate in figure 9 (c), it can be observed that the sample had continuous scratches on its worn surface suggesting mild abrasive wear with few shallow grooves and craters when compared to other samples. this may be attributed to larger quantity of sicp reinforcement particles present in the composite material which may have improved the load bearing strength of the composite, thereby reducing its plastic deformation. (jafari et al., 2018; vantrinh et al., 2018). odiwo et al. (2023): international journal of engineering materials and manufacture, 8(1), 1-12 10 (a) (b) (c) figure 9: micrograph wear worn surfaces of (a) aa6061 alloy, (b) aa6061/2.5 wt.% oxidized-sicp composite and (c) aa6061/10 wt.% oxidized-sicp 4 multi-objective optimization (moo) analysis the two models obtained in equation 3 and 5 can be used to generate points of desirable results in the design region for wear rate and cof respectively, since the required process condition for one response is different from the other. however, this can be overcome through utilization of multi-objective optimization (moo), a tool in rsm where both responses (wear rate and cof) are simultaneously optimized. for this research, the goal was to minimize both wear rate and cof at a specific combination of input factors being considered. based on the solution analysis in table 9, optimum values of input process parameters is achieved with experiment number 1 and the ramp graph showing the details of the input factors and the corresponding responses is shown in figure 10. from table 9 and figure 10, the optimum influence of pre-processing parameters on the tribological behaviour of al-sicp composites obtained from the moo are 9.907% sic reinforcement fraction, 1233.993 °c surface oxidation temperature, and 376.183 °c preheat temperature. the resulting responses at this optimized condition are 0.110 mm 3 /m for wear rate and 0.110 for cof with a confidence and desirability level of 1. table 9: optimal solution generated for the response solution number sic reinforcement fraction surface oxidation temp. preheat temp. wear rate coefficient of friction desirability 1 9.907 1233.993 376.183 0.011 0.110 1.000 selected 2 9.997 1227.829 345.497 0.011 0.149 1.000 3 10.000 1216.667 436.667 0.011 0.183 1.000 4 9.996 1215.850 476.076 0.011 0.171 1.000 5 9.867 1210.665 496.646 0.011 0.215 1.000 study on the optimization of surface modification processing of sicp and tribological properties of aa6061-sicp… 11 figure 10: ramp graph at optimal solution 5 conclusions based on the results obtained in this research, the following conclusions were drawn: 1. optimum condition for reinforcement pre-processing in al-sicp composite development was successfully achieved using the ccd. 2. based on central composite design of rsm, empirical models capable of evaluating the properties wear rate and cof under various reinforcement pre-processing parameter conditions were developed. 3. analysis of variance (anova) was used test the adequacy of the developed models at 95% confidence level and the models were found to be significant and adequate. from the 3-d & 2-d surface plots for wear rate, the influence of srf & sot on wear rate was analyzed. 4. the wear rate was observed to decrease with increasing silicon carbide weight at all surface oxidation temperatures. at 44.49 %, srf had the most influence on wear rate, while sot and pt had 0.65 % and 1.03 % influence on wear rate respectively. 5. for the surface plots showing the influence of srf & sot on coefficient of friction, the lowest cof was observed at 10% silicon carbide weight and 1300 °c surface oxidation temperature. at silicon carbide weight above 6.7% and surface oxidation temperatures above 1150 °c, the coefficient of friction was observed to be decreasing. at 35.48 %, srf had highest influence of on cof, while sot and pt had 0.047 % and 2.66 % influence on cof respectively. 6. from the optimization analysis, the set of conditions that simultaneously optimizes both wear rate and cof was found as 9.907% sic reinforcement fraction (srf), 1233.993 °c surface oxidation temperature (sot), and 376.183 °c preheat temperature (pt). the resulting responses at this optimized condition are 0.110 mm 3 /m for wear rate and 0.110 for cof with a confidence and desirability level of 1. 7. with result, the aa6061/oxidized-sicp composite with superior wear resistance can be utilized for wear resistant applications such as automobile piston. references 1. adebisi, a. a., maleque, m. a., ali, m. y. & bello, k. a. (2016). effect of variable particle size reinforcement on mechanical and wear properties of 6061al–sicp composite. composite interfaces, 23:6, 533-547. doi:10.1080/09276440.2016.1167414. 2. adebisi, a. a., maleque, m. a., & bello, k. a. (2017). investigation of parametric influence on the properties of al6061-sicp composite. iop conf. series: materials science and engineering 184 (2017) 012019. doi:10.1088/1757-899x/184/1/012019. 3. adebisi, a. a., ndaliman, m. b. (2015). mathematical modelling of stir casting process parameters for al-sicp composite using central composite design. proceedings of the 28th agm and international conference of the nigerian institution for mechanical engineers. hosted by the nigerian institution for mechanical engineers, abuja city, nigeria, october 21-23, 2015. 4. adediran, a. a., akinwande, a. a, balogun, o. a, olorunfemi, b. j, (2021). optimization studies of stir casting parameters and mechanical properties of tio2 reinforced al 7075 composite using response surface methodology. sci rep. 2021 oct 6;11(1):19860. doi: 10.1038/s41598-021-99168-1. pmid: 34615935; pmcid: pmc8494885. odiwo et al. (2023): international journal of engineering materials and manufacture, 8(1), 1-12 12 5. ahmad, a., lajis, m. a., yusuf, n. k. and rahim, s. n. (2020).statistical optimization by the response surface methodology of direct recycled aluminum-alumina metal matrix composite (mmc-alr) employing the metal forming process. processes 2020, 8, 805. 6. alten, a., erzi, e., gürsoy, ö., ağaoğlu, g. h., dispinar, d. and orhan, g. (2019). production and mechanical characterization of ni-coated carbon fibers reinforced al-6063 alloy matrix composites. journal of alloys and compounds (2019). 7. bobić, b., mitrović, s., babić, m., i. bobić, i. (2010). corrosion of metal-matrix composites with aluminium alloy substrate. tribology in industry, volume 32, no. 1, 2010. 8. jafari, f.,·sharifi, h., saeri, m. r. & tayebi, m. (2018). effect of reinforcement volume fraction on the wear behavior of al-sicp composites prepared by spark plasma sintering. silicon. https://doi.org/10.1007/s12633-0189779-2. 9. di leo, g., sardanelli, f. (2020). statistical significance: p value, 0.05 threshold, and applications to radiomics— reasons for a conservative approach. eur radiol exp 4, 18 (2020). https://doi.org/10.1186/s41747-020-0145-y. 10. khalid, m. g., liaqat, a., akhlaq, a., rafiq, a., kashif, m. d., ijaz, a. c. & ramzan, a. k. (2013). synthesis and characterization of al/sic composite made by stir casting method. pak. j. engg. & appl. sci. vol. 12, jan., 2013 (p. 102-110) 102. 11. lee, t., lee, j., lee, d., jo, i., lee, s. k. & ryu, h. j. (2020). effects of particle size and surface modification of sic on the wear behavior of high volume fraction al/sicp composites. journal of alloys and compounds 831 (2020) 154647. 12. montgomery, d. c. (2013). design and analysis of experiments; eighth edition. john wiley & sons, inc., 111 river street, hoboken, new jersey. 13. moses, j. j., dinaharan, i., sekhar, s. j. (2016). prediction of influence of process parameters on tensile strength of aa6061/tic aluminum matrix composites produced using stir casting. trans. nonferrous met. soc. china 26(2016) 1498−1511. 14. myers, r. h., montgomery, d. c. and anderson-cook, c. m. (2016). response surface methodology: process and product optimization using designed experiments; fourth edition. john wiley & sons, inc., hoboken, new jersey 15. nagaral, m., auradi, v., parashivamurthy, k.i. and kori, s.a. (2016). a comparative study on wear behavior of al6061-6% sic and al606 1-6% graphite composites. journal of applied mechanical engineering 2016, 5:6. 16. odiwo, h., bello, k.a., abdulwahab, m., adebisi, a.a. & maleque, m.a. (2021). properties of aluminium/electroless ni-coated sic composites a review. fudma journal of sciences (fjs), vol. 5 no. 1, march, 2021, pp 381 – 394. 17. ramesh, c.s., keshavamurthy, r., channabasappa, b.h. & pramod, s. (2010). friction and wear behavior of nip coated si3n4 reinforced al6061 composites. tribology international 43 (2010), 623 – 634. 18. rana, r. s., purohit, r., mishra, p. m., sahu, p. & dwivedi, s. (2017). optimization of mechanical properties of aa 5083 nano sic composites using design of experiment technique. 5th international conference of materials processing and characterization (icmpc 2016). materials today: proceedings 4 (2017) 3882–3890. 19. umanath, k., palanikumar, k., & selvamani, s.t. (2013). analysis of dry sliding wear behaviour of al6061/sic/al2o3 hybrid metal matrix composites. composites: part b 53 (2013) 159–168. 20. vantrinh, p., lee, j., minh, p. n., phuong, d. d. & hong, s. h. (2018). effect of oxidation of sic particles on mechanical properties and wear behavior of sicp/al6061 composites. journal of alloys and compounds 769 (2018), 282-292. 21. verma, v. and khvan, a. (2019). advances in composite materials development. chapter; a short review on al mmc with reinforcement addition effect on their mechanical and wear behaviour. intechopen.: doi: http://dx.doi.org/10.5772/intechopen.83584 https://doi.org/10.1007/s12633-018-9779-2 https://doi.org/10.1007/s12633-018-9779-2 http://dx.doi.org/10.5772/intechopen.83584 international journal of engineering materials and manufacture (2022) 7(2) 61-70 https://doi.org/10.26776/ijemm.07.02.2022.03 islam m. r. 1 , rashid, m. m. 1 , rahman, m. a. 2 , mohamad, m. h. s 3 . and embang, a. h. 1 1 department of mechatronics engineering 2 department of mechanical engineering 3 department of accounting international islamic university malaysia, po box 10, 5027 kuala lumpur, malaysia e-mail: mahbub@iium.edu.bn reference: islam et al. (2022). a review on blockchain technology for distribution of energy. international journal of engineering materials and manufacture, 7(2), 61-70. a review on blockchain technology for distribution of energy md rafiqul islam, muhammad mahbubur rashid, mohammed ataur rahman, muslin har sani mohamad and abd halim embang received: 18 february 2022 accepted: 19 april 2022 published: 22 april 2022 publisher: deer hill publications © 2022 the author(s) creative commons: cc by 4.0 abstract the alternative energy generation sources have increased drastically from centralized systems to distributed systems which increases the stability of energy distribution management systems and reduces the distribution cost as well. on the other hand, it reduces the probability of major area electricity blackout chances and decreases the energy distribution loss. for proper distribution and management of energy, there are different types of advanced technologies like artificial intelligence, and the internet of things (iot) available, but a blockchain automated system is one of the best choices and is highly recommended. various aspects of blockchain technology and energy management system have been discussed in this review paper where a total number of 423 journal papers, articles, and online information sources have been reviewed in the initial stage, and finally, 63 published research articles have been selected for review. there are several topics, including technology overview in energy management systems, blockchain application of energy trading, blockchain technology implementation challenges, distributed energy management system with ethereum, and a conclusion with some recommendations have been discussed. blockchain and distributed ledger technology (dlt) are highly transparent, authenticate, and secure systems that can be used for distributing the energy between distributor and consumer without an intermediator which increases the overall efficiency of the system. this paper aims to highlight the blockchain and distributed ledger technology and how it works as well as optimize the transaction processing cost among the participants of the consortium network. this paper will make a significant contribution to the new research work and in the field of energy management systems. keywords: blockchain, distributed ledger technology, iot, ethereum, bitcoin. 1 introduction the traditional centralized electricity distribution works vertically and is controlled by a large utility management system [1]. the production and transmission of the electricity into the power grid distribution channels are controlled centrally [2]. the power grid distribution channels then distribute the electricity in the different geographical locations through sub-station and finally, the end-users consume the same from the local sub-stations [3]. the centralized electrical system is very challenging due to the complex network management system, which incurs a significant amount of system losses, increases the production and distribution cost, and ultimately consumers need to pay the high electricity cost which ultimately triggers the national economy [4-5]. the vertical structured system also increases the carbon emission countrywide as well as globally [6]. however, the issues and challenges of the traditional energy system can be improved by implementing the distributed energy management system which may encourage the introduction of the perpetual energy system to generate electricity through using new blockchain and distributed ledger technology [7-9]. in the early days, the traditional energy system was fully controlled by public organizations like power generation, distribution, and commercially selling the electricity to the consumer level. but the distributed energy generation concept can be used to generate electricity in different locations across the country and easily can distribute to the end-user consumer level [10]. the interested private electricity producer company needs to submit their offer and get permission from the government-owned utility body for generating, distributing, and sell the electricity to the a review on blockchain technology for distribution of energy 62 consumers [11]. so, the private companies can minimize the production and distribution cost which will lead to reducing the selling cost on the consumers’ end. therefore, to minimize the production, distribution, and selling cost of electricity; a consortium network called a common distribution power grid need to be established between the private electricity producing companies and the government energy regulatory body where they can share the excess or non-useable electricity with the help of blockchain and distributed ledger technology [12-13]. blockchain can replace the legacy energy distribution system with an economical electrical distribution system that will be more transparent, traceable, and easy to manage the entire system [14]. in this paper, we will focus on the distributed electrical system, the scope, and challenges of blockchain technology, and the specific application of blockchain for the distribution of energy. 2 review methodology google scholar search engine has been used to access the papers including research gate, different types of index journals, and web of science journals. we also have visited different related websites to gather information for our analysis and different keywords have been used for the same. in the initial stage, a total number of 423 papers have selected to download for study purposes by using different keywords, similar topics, and titles. among these 423 papers, the authors have selected 115 papers based on the impact factors of the journals, citations, reviews, conferences, and the quality of the websites. finally, 63 related papers and articles have been selected for the study where most of the papers were published in the last 5 years. the output of this study has been summarized in different steps. first, is the technical overview of the energy management system. the second is the use of blockchain technology in energy trading platforms. third, distributed energy management of ethereum blockchain. finally, recommendations have been suggested to solve the issues. figure 1 displays the methodology of this review. figure 1: research methodology overview 3 technology overview of energy management system this section includes an overview of distributed energy systems, the overview of blockchain and how the technology works, the application of blockchain in the energy sector, and the electricity market. 3.1 centralized energy centralized electricity production is the large-scale electricity generation system that distributes the electricity vertically. the centralized power station is located far from the end-users and connected to the high voltage distribution lines called the power grid [15]. most centralized power plants are based on fossil fuel, nuclear, hydraulic, and wind-based power plants. however, an enormous amount of electricity generates from centralized power plants across the globe [16]. earlier, electricity was generated and distributed independently by each utility company. islam et al. (2022): international journal of engineering materials and manufacture, 7(2), 61-70 63 nowadays, a significant amount of electricity is generated and distributed from different geographical locations which are economically cost-effective and ensure high availability. the local utility companies deliver the electricity to the consumers, and it is generated by centralized power plants located at different locations. 3.2 distributed energy distributed power generation refers to the system which is operated in different locations near the consumers' area. different technologies are used to generate electricity like solar panels, wind turbines, generators, etc. [17]. the distribution channel may be a single structure or connected to the mini-grid. normally, it connects to the low voltage delivery lines which help to generate clean power for the end-users and reduce the electricity losses in the distribution channels [18]. some common distributed power generation systems in residential areas are: • solar based power • generator based power (use gasoline or diesel) • wind-based power • natural gas-based power distributed power generation system is introduced to generate alternative electric power from renewable energy sources. the distributed system like solar power, generators, wind turbine, natural gas-based power generation, etc. systems supply the power in the mini-grid that will reduce the emission of fossil fuels and electricity can be provided to the local communities [19]. the distributed power supply system ensures reliable and uninterrupted power supply to the end-users. the shifting from the traditional centralized power system to a decentralized power system eliminates the long-distance transmission lines for transmitting the electricity which improves the uptime and stability of electricity to the consumers [20]. however, sometimes distributed power system becomes more complex due to improper management and human errors. these issues can be addressed by introducing automation which will provide a better management and monitoring system [21]. distributed energy generation refers to the system which is operated in different locations near the consumers' area. different technologies are used to generate electricity like solar panels, wind turbines, generators, etc. [17]. the distribution channel may be a single structure or connected to the mini-grid. normally, it connects to the low voltage delivery lines which help to generate clean power for the end-users and reduce the electricity losses in the distribution channels [18]. some common distributed power generation systems in residential areas are: • solar-based power • generator-based power (use gasoline or diesel) • wind-based power • natural gas-based power distributed electricity production systems are introduced to produce alternative electricity from renewable energy sources. the distributed system like solar power, generators, wind turbine, natural gas-based power generation, etc. systems supply the electricity in the mini-grid that will reduce the emission of fossil fuels and electricity can be provided to the local communities [19]. the distributed energy supply system ensures reliable and uninterrupted energy supply to the end-users. the shifting from the traditional centralized system to a decentralized system eliminates the long-distance transmission lines for transmitting the electricity which improves the uptime and stability of electricity to the consumers [20]. however, sometimes distributed energy system becomes more complex due to improper management and human errors. these issues can be addressed by introducing automation which will provide a better management and monitoring system [21]. table i: comparison between centralized and distributed energy systems. particulars centralized distributed ownership government bodies (independent energy plants) household, local, government, private firm finance by state or government bodies owner, collaboration, consortium, etc. availability the probability of power outage is high due to long distribution lines. supply volume is low, but availability is high. les power outage. maintenance maintenance is more complicated than the distributed system, due to the large network. maintenance is much easier than a centralized system, due to a small distribution network. capacity large scale production capability and supply the electricity at the national level. production capability is low and supplies the electricity for local communities connection mode connected to the national power grid. connected to the off-grid or mini-grid. a review on blockchain technology for distribution of energy 64 3.3 blockchain and distributed ledger technology in the year 2009, blockchain technology was introduced by the pseudonymous person or a group through a new cryptocurrency called “bitcoin” [22]. people are much familiar with the internet of things (iot), still, iot is dominating for processing the information in different utility sectors [23]. iot is a fully centralized concept to process data. on the other hand, blockchain is a fully decentralized database network platform. blockchain is a trusted, immutable, secured platform where the data is represented as a chain of blocks, and transactions are gathered into the blocks [24]. every block in the blockchain contains data, the hash value of the previous block, time, and other transactional data [25]. blockchain ensures data security and integrity by using distributed ledger where all the transactional information is available in every node in the network [26]. the blocks are connected cryptographically with the preceding blocks which create the chain of blocks. for example, a simple blockchain structure has been presented in figure 2. the purpose of the use of distributed ledger and blockchain technology is the same. it’s a digital system where records are connected to the related assets, and at the same time, all the nodes in the network will be updated accordingly with the same information [27]. cryptocurrency is used for the dlt system, and it verifies the digital transaction into the blockchain network [28]. it is a resilient system that prevents compromising the nodes and keeping the truck records of assets in the network. figure 2: blockchain structure 3.4 types of blockchain the blockchain has been categorized into three different types namely public, private, and consortium blockchain. they have different types of characteristics, but the service nature is almost the same. different types of blockchain are as follows: 3.4.1 public blockchain public blockchain networks incorporate the proof-of-work (pow) consensus protocol. it is an open source-based network where anyone can participate by downloading the relevant code on their computer or any other application-supported device. 3.4.2 private blockchain the private blockchain network is controlled by a single authority and this authority maintains the access right of the participants in the network. only the authorized participants are permitted to do the transaction in the system. in terms of data privacy, it is more secure than other blockchain networks. 3.4.3 consortium blockchain the consortium blockchain network is a combination of private and public blockchains. the users’ access authority is maintained by the authorized users only. it is faster, scalable, and more transparent compared to the public blockchain. 3.5 microgrid system nowadays, renewable energy is one of the major concerns in the energy industry which needs to be incorporated into the power distribution system [29]. though there are various forms of the energy distribution system, the microgrid can play a vital role in the same [30]. maximum production as well as utilization of this renewable energy become a very popular topic from industry to academia. the distribution of renewable energy through the microgrid platforms and policy is one of the key factors which need to be introduced first [31]. a clear policy guideline from the regulators must incorporate for implementing the efficient and cost-effective distributed renewable energy system [32-33]. the scheduling and battery backup systems are highly recommended to introduce in the distributed energy management system [34]. real-time, low-cost pricing policy, transparent, and traceable energy distribution are major concerns that need to be addressed [35]. the participants of the microgrid system and individual stakeholders should islam et al. (2022): international journal of engineering materials and manufacture, 7(2), 61-70 65 be aware of the benefits of using the microgrid system. social-economic development and awareness creation among the consumers and stakeholders are also equally important and need to take into consideration before implementing the renewable energy system [36]. the energy distribution mechanism, microgrid distribution strategy, and supply and demand distribution policy are highly recommended to incorporate before establishing the energy distribution network [37]. 4 blockchain application in energy trading platform the integration of blockchain applications with energy trading systems must have integrated the smart metering system in the network. the consumers, traders, and stakeholders should be connected to this network [38-39]. the smart meters are introduced to the power distribution system through a blockchain network which shows in figure 3. by using this network, it is easier to monitor the energy consumption and production capacity as well. all the data are encrypted and placed in the network through a smart contract [40]. figure 3: power energy trading system 4.1 the scope of blockchain technology for distribution of energy (a) renewable energy certificate and wholesale trading power producing companies should obtain these certificates from the related utility authority and all the companies must install the smart meters at their ends where they will communicate with other participants through the internet. these certificates will permit the energy producer to produce green energy and permission for the distribution of energy. renewable energy certificate (rec) maybe play an important role to increase the investment in the field of distributed energy systems which may reduce the emission of carbon dioxide in the environment [41]. the integrated demand response system (drs) is one of the more effective systems for the distribution of green energy where blockchain technology can be used for doing transactions between supplier and consumer [42]. (b) transparency and security for distribution of electrical energy transparency, privacy, and security are always important aspects to grow the confidence between the consumers and distributors. to solve the privacy and transparency issues, the energy distribution system has been developed through a consortium-based blockchain trading system where all the connected nodes in this consortium received electricity from a large energy distribution grid [43]. resiliency is another important aspect that needs to be addressed parallelly with privacy, especially when the live system goes down. the smart contract mechanism in the blockchain is an outstanding feature that can enhance privacy, transparency, and security issues [44]. a review on blockchain technology for distribution of energy 66 (c) electricity trading latency mostly, the efficacy of the energy distribution system depends on the latency when distributing energy from the main distribution grid to a remote location [45]. to solve this issue and improve the distribution and trading of energy, the blockchain-based application can use as a service platform that is capable to reduce latency and secure the transaction of power [46]. the ethereum-based platform is suitable to support the energy distribution network to manage the local energy market where 600 participants belong to the consortium and the ethereum protocol can process every transaction within 5 minutes and around 99% of computing power can be saved by using proof-ofstake consensus mechanism instead of proof-of-work (pow) algorithm [47]. 5 blockchain technology implementation challenges in energy sector there are several steps have been emerged in the technology sector to address the issues, the researchers and business experts still face some challenges which are the below: (a) scalability tough blockchain and distributed ledger technology is the latest energy distribution platform, the transaction processing time has still become very high. due to the design and the architecture of database sharing nature, the energy consumption for making a transaction is higher than any other centralized system [48]. for example, 0.001 kwh power is required for a transaction of visa, whereas 740 kwh power is required for a bitcoin transaction [49]. although there is a significant number of methods have been proposed to enhance the transactional performance, every solution comes up with some limitations. due to the sharing nature of the database, huge computational power and storage capacity are required to maintain the energy distribution network [48]. sharing of the database is one of the big concerns of security issues which creates operational complexity in the consortium network [49]. (b) regulation though a few numbers of regions like japan and europe have started to work on the regulation of blockchain technology, still it is in the premature stage [50]. the lack of global regulation is one of the main barriers to implementing the blockchain application in the field of distributed energy management systems [51]. a proper energy regulatory guideline is strongly required to maintain the distributed energy system which can assist to resolve the dispute management problem in the energy sector. (c) grid infrastructure to distribute renewable energy through a blockchain consortium network, a smart grid needs to be incorporated into the system. still, maximum power distribution lines depend on the traditional grid. to minimize the electricity distribution cost, the system loses, and maximize the use of renewable energy; a large grid infrastructure setup needs to be established nationwide where the participants can be benefited from this infrastructure setup [52]. (d) 51% attack the 51% attack is another challenge in the blockchain that may interrupt the network operations [53]. through these attacks, the hackers may take control of the network and can manipulate the transaction in their favor. especially it is very risky for a small network where the number of participants is few. however, a 51% hash rate is not always a mandatory requirement to compromise a network, double spending attack can also be capable to comprise the same [54]. 6 distributed energy management with ethereum blockchain distribution of electricity management system through ethereum blockchain application depends on the smart contract algorithm, adaptability, and scalability as well [55]. the ethereum-based blockchain architecture is a container-based model where all the codes are incorporated via a smart contract [56]. the electricity consumers, distributors, and energy producers relate to this ethereum distribution network. by using the ethereum blockchain network, participants can share the data into the network and exchange digital transactions among themselves [57]. the stakeholders and energy distributors are also able to monitor the present status and additional energy requirements if needed. it is a public network where participants can share their information with their peers into the network. distributed ledger system updates all the transactions and any changes in the network to the participants in the consortium which helps to mitigate the risk [58]. ethereum blockchain network not only uses the smart contract but also shares the data through distributed ledger among the participants [59]. ethereum consortium blockchain platform is a reliable and safe network for trading electricity between peer-topeer (p2p) [60]. it is a highly secured network, and all the nodes are assigned with private and public keys, and transactions are encrypted through a cryptographic hashing algorithm [61]. the network also supports the credit type payment method which helps to provide a quick service for energy trading [62]. the identity of the user, electricity consumption, and billing status can easily monitor with incorporation between the smart meter and ethereum blockchain network which will be the unique system in the energy distribution sector [63]. islam et al. (2022): international journal of engineering materials and manufacture, 7(2), 61-70 67 the ethereum blockchain consortium model will encourage the utility regulation sectors, the stakeholders, distributors, and energy consumers to distribute energy, especially for distributed energy trading systems where the network will introduce a secured transactional environment between the users. 7 conclusions blockchain as an emerging technology that is introduced in distributed energy trading systems has been growing attention in the utility sector. there is remarkable scope especially in the energy sector to use this blockchain technology for the distribution of energy with high security, transparency, and privacy as well. the incorporation of smart contracts in the ethereum blockchain network will be able to eliminate the operational complexity of the energy management system. integrated demand response (idr) will be a great example that will encourage to use of this technology for energy consumption and better energy management system with high efficiency. despite the advantages to use this technology, some challenges need to be addressed especially regulatory issues before implementing the blockchain consortium network in the public sector energy platform. centralized and decentralized energy management system, smart microgrid, application of blockchain in energy trading platform, renewable energy, security, and transparency of energy trading are explained for the application of blockchain in distributed energy. to overcome the blockchain implementation challenges in the field of the distributed energy system, a few numbers of important recommendations for future advancement of the blockchain application in the energy sector are highlighted as follows: • energy trading costs will be minimized by around 40% which will potentially reduce the consumers’ billing costs by introducing the blockchain-based application. • the end-users are connected directly to ethereum based blockchain platform which allows them to buy the energy at the desired cost. • to build a secure distributed energy system that is capable to increase the transparency of the stakeholders not compromising privacy. • ethereum blockchain uses proof-of-stake (pos) consensus mechanism instead of a proof-of-work (pow) algorithm which is capable to save around 99% of computing energy and is highly recommended for introduction in the field of efficient energy management systems. however, the case study explains that the proposed system is capable to optimize the allocation of resources for the distribution of energy, reduce the system loss, and reduce the energy consumption cost of the users which means economically viable. references 1. mojumdar, m. r. r, himel, m. s. h, and kayes g. (2015). a distinctive analysis between distributed and centralized power generation. international journal of recent research in electrical and electronics engineering (ijrreee), december 2015, vol 2, issue 4, pp. 1-6. 2. kundankar, r. r., and katti, p. k. (2017). hybrid energy system for remote and rural villages. international journal of engineering technology science and research, vol 4, issue 11, issn 2394-3386. 3. lazari, a. and charalambous, c. (2015). contemplation of transformer loss evaluation methods in vertically integrated and decentralized energy systems. 2015 ieee eindhoven powertech. doi: 10.1109/ptc.2015.7232463. 4. ren, z., wang, w., chen, b., li x., zhang, y., hu, y., and li h. (2021). a power trading mode based on blockchain for prosumers. 3rd international symposium on architecture research frontiers and ecological environment (arfee 2020), zhangjiajie, china, vol 237. 5. denktas, b., pekdemir, s., and soykan, g. (2018). peer to peer business model approach for renewable energy cooperatives. 7th international ieee conference on renewable energy research and applications, icrera 2018, paris, france, 14–17 october 2018; institute of electrical and electronics engineers inc.: new york, ny, usa, 2018; pp. 1336–1339. 6. kingsley, a., shongwe, t., and joseph m. k. (2018). renewable energy integration in ghana: the role of smart grid technology. ieee 2018 international conference on advances in big data, computing and data communication systems (icabcd), pp. 1-7, doi:10.1109.icabcd41997.2018. 7. peter, v. (giz blockchain lab), paredes j. (interamerican development bank, idb), rivial, m., r. (globalgrid), sepúlveda, e. s. (phineal), astorga d. a. h. (phineal). (2019). blockchain meets energy, german-mexican energy partnership (ep) and florence school of regulation (fsr). 8. khalid, r., javaid, n., javaid, s., imran, m., and naseer n. (2020). a blockchain-based decentralized energy management in a p2p trading system. 2020 ieee international conference on communications (icc), dublin, ireland, pp. 1-6. 9. ai, s., hu, d., guo, j., jiang, y., rong c., and cao j. (2020). distributed multi-factor electricity transaction match mechanism based on blockchain. 4th ieee international conference on energy internet, icei 2020, sydney, australia, august 2020, pp. 121-127. 10. mylrea, m. and gourisetti, s. n. g. (2017). blockchain for smart grid resilience: exchanging distributed energy at speed, scale, and security. 2017 resilience week (rws), 2017. a review on blockchain technology for distribution of energy 68 11. calvillo, c.f., sanchez-miralles, a., and villar j. (2015). energy management and planning in smart cities. institute for research in technology (iit) icai school of engineering, comillas pontifical university, santa cruzde marcenado26, madrid, spain, 55 (2016) 273-287. 12. dinh, t. t. a., lui, r., zhang m., chen g, ooi b. c., and wang j. (2018). untangling blockchain: a data processing view of blockchain systems. ieee transactions on knowledge and data engineering, vol. 30, issue 7, pp. 1366–1385, doi: 10.1109/tkde.2017.2781227. 13. dunphy, p. and petitcolas, f. a. (2018). a first look at identity management schemes on the blockchain. ieee security & privacy, vol. 16, issue 4, pp: 20–29. 14. khaqqi, k. n., sikorski j. j., hadinoto k., and kraft m. (2018). incorporating seller/buyer reputation-based system in blockchain-enabled emission trading application,” [online], available: https://doi.org/10.1016/j.apenergy.2017.10.070, vol 209, pp: 8-19. 15. lopes, j. a. p., hatziargyriou, n., mutale, j., djapic, p., and jenkins, n. (2006). integrating distributed generation into electric power systems: a review of drivers, challenges, and opportunities. electric power systems research, vol. 77, pp: (1189-1203). 16. dugan, r. c., price, s. k. (2002). issues for distributed generation in the us. ieee pes winter meeting 2002, new york (usa), vol. 1, pp: (121-126). 17. palensky, p., and dietrich, d., (2011), demand side management: demand response, intelligent energy systems, and smart loads. ieee transactions on industrial informatics, vol 7, issue 3. 18. papaefthymiou, g., and dragoon, k. (2016). towards 100% renewable energy systems: uncapping power system flexibility. energy policy, vol 92, pp: (69–82), doi: 10.1016/j.enpol.2016.01.025 19. hanna, r., ghonima m., kleissl j., tynan g., and victor d. g. (2017). evaluating business models for microgrids: interactions of technology and policy. energy policy 103, vol 103, issue c, pp: (47–61), doi: 10.1016/j.enpol.2017.01.010. 20. dondi, p., bayoumi, d., haederli, c., julian, d., and suter, m. (2021). network integration of distributed power generation. journal of power sources, vol. 106, issue 1-2, pp. 1-9. 21. burgess, p. j., casado, m. r., gavu, j., mead, a., cockerill, t., lord, r., van der horst, d., and howard, d. c. (2011). a framework for reviewing the trade-offs between, renewable energy, food, feed, and wood production at a local level. renewable and sustainable energy reviews. avaiable http://dx.doi.org/10.1016/j.rser.2011.07.142 , doi: 10.1016/j.rser.2011.07.142. 22. nakamoto, s. (2008) bitcoin: (2008), a peer-to-peer electronic cash system. available: https://bitcoin.org/bitcoin.pdf, 2008 23. barman, b. k., yadav, s. n., and kumar, s. (2018). iot-based smart energy meter for efficient energy utilization in smart grid. 2nd international conference on power, energy, and environment: towards smart technology (icepe), doi:10.1109/epetsg.2018.8658501. 24. tama, b. a., kweka, b. j., park y., and rhee h., (2017). a critical review of blockchain and its current applications. in 2017 international conference on electrical engineering and computer science (icecos), 2017, pp:1(09-113). 25. seebacher, s., and sch¨uritz, r., (2017). blockchain technology as an enabler of service systems: a structured literature review. international conference on exploring services science. springer, 2017, pp: (12–23). 26. islam, m. r., rahman, m. m., mahmud, m., rahman, m. a, mohamad, m. h. s. b., and embong, a. h. b. (2021). a review of blockchain security issues and challenges. 2021 ieee 12 th control and system graduate research colloquium (icsgrc), 2021, pp. (227-232), doi: 10.1109/icsgrc53186.2021.9515276. 27. idelberger, f., governatori, g., riveret, r., and sator, g. (2016). evaluation of logic-based smart contracts for blockchain systems. international symposium on rules and rule markup languages for the semantic web, springer, cham, pp. 167-183. 28. kosba, a., miller, a., she e., wen z., and papamanthou, c. (2016). the blockchain model of cryptography and privacy-preserving smart contracts. 2016 ieee symposium on security and privacy (sp), san jose, ca, usa, 2016, pp. 839-858, doi: 10.1109/sp.2016.55. 29. liserre, m., sauter, t., and hung, j. y. (2010). future energy systems: integrating renewable energy sources into the smart power grid through industrial electronics. ieee industrial electronics magazine, vol. 4, no. 1, pp. 18–37. 30. farhangi, h. (2014). a road map to integration: perspectives on smart grid development. ieee power and energy magazine, vol. 12, no. 3, pp:(52–66). 31. strasser, t., siano, p., and ding, y. (2018). methods and systems for a smart energy city. ieee transactions on industrial electronics, vol. 66, no. 2, pp. 1363–1367. 32. hafez, o., and bhattacharya k., (2018). integrating ev charging stations as smart loads for demand response provisions in distribution systems. ieee transactions on smart grid, vol. 9, no. 2, pp. 1096–1106. 33. tsukamoto, o., and morozumi, s. (2014). grid code development in japan. international conference on integration of renewable and distributed resources, kyoto, japan, [online], available: http://www.nedo.go.jp/english/ired2014/program/pdf/s2/s2_2_osami_tsukamoto.pdf; 2014. https://doi.org/10.1016/j.apenergy.2017.10.070 http://dx.doi.org/10.1016/j.rser.2011.07.142 https://bitcoin.org/bitcoin.pdf https://doi.org/10.1109/epetsg.2018.8658501 islam et al. (2022): international journal of engineering materials and manufacture, 7(2), 61-70 69 34. juan l., shiju w., jing x., xuefei z., and peng l. (2017). research on microgrid distribution network and its operation efficiency in the energy internet. 2nd international conference on power and renewable energy, taiwan. 35. di silvestre, m. l., gallo, p., ippolito, m. g., sanseverino e. r, and zizzo g. (2018). a technical approach to the energy blockchain in microgrids. ieee transactions on industrial informatics 2018; doi 10.1109/tii.2018.2806357. 36. jackson, f. (2018). blockchain: downfall or the future of utilities? forbes, [online], available: https://www.forbes.com/sites/feliciajackson/2018/04/10/blockchain-nemesis-or-future-forutilities/#3e6156114f0b. 37. mengelkamp, e., gärttner j., rock k., kessler s., orsini l., and weinhardt c. (2017). designing microgrid energy markets: a case study: the brooklyn microgrid. pp.870–880. doi: 10.1016/j.apenergy.2017.06.054. 38. ferreira, j.c., afonso, j.a., monteiro, v., and afonso, j. l. (2018). an energy management platform for public buildings,” istar-iul, instituto universitário de lisboa (iscte-iul), 1649-026 lisboa, portugal. 39. khalid, r., javaid, n., almogren, a., javed, m.u., javaid, s., and zuair m. (2020). a blockchain-based load balancing in decentralized hybrid p2p energy trading market in smart grid. ieee access 2020, 8, 47047– 47062. 40. gaybullaev, t., kwon, h.-y., kim t., and lee m. k. (2021). efficient and privacy-preserving energy trading on blockchain using dual binary encoding for inner product encryption. [online], available: https://doi.org/10.3390/s21062024, sensors 2021. 41. romano, t., mennel, t., and scatasta, s. (2017). comparing feed-in tariffs and renewable obligation certificates: the case of repowering wind farms,” economia e politica industriale, vol. 44, no. 3, pp. 291–314, 2017. 42. wang, li. y., li, c., wang, g., zhao, j. d., and chen, c. (2020). improving operational flexibility of integrated energy system with uncertain renewable generations considering thermal inertia of buildings. energy convers, manag.207:112526. doi: 10.1016/j.enconman.2020.112526. 43. zhou, z., tan, l., and xu, g. (2018). blockchain and edge computing-based vehicle-to-grid energy trading in energy internet. 2018 2nd ieee conference on energy internet and energy system integration (ei2) (ieee), pp. 1–5). doi: 10.1109/ei2.2018.8582652. 44. tanwar, s., bhatia, q., patel, p., kumari, a., singh, p. k., and hong, w. c. (2018). machine learning adoption in blockchain-based smart applications: the challenges, and a way forward. ieee access 8, 474–488. doi: 10.1109/access.2019.2961372, (2018). 45. qayyum, f., naeem, m., khwaja, a., anpalagan, a., guan, l., and venkatesh b. (2015). appliance scheduling optimization in smart home networks. access, ieee, vol. 3, pp. 2176–2190. 46. liu, s., chen, f., shen, l., hu, y., and ding, y. (2019). a high-performance local energy trading cyber-physical system based on blockchain technology. earth environ, sci. 227:032009, doi: 10.1088/17551315/227/3/032009. 47. vijai, c., elayaraja, m., suriyalakshmi, s. m. and joyce, d. (2019). the blockchain technology and modern ledgers through blockchain accounting,” adalya journal, vol. 8(12). 48. blockchain technology for the energy sector: significant potential but still key challenges to overcome. (2021). energy – environment – mobility. [online], available: https://www.alcimed.com/en/alcim-articles/blockchaintechnology-for-the-energy-sector-significant-potential-but-still-key-challenges-to-overcome/ 49. li, h., xiao, f., yin, l., and wu, f. (2021). application of blockchain technology in energy trading: a review. frontiers in energy research, vol 9. https://doi.org/10.3389/fenrg.2021.671133 50. di silvestre, m. l., favuzza, s., riva sanseverino, e., zizzo, g. (2018). how decarbonization, digitalization, and decentralization are changing key power infrastructures. renewable and sustainable energy reviews, elsevier, vol. 93(c), pages 483-498. https://doi.org/ 10.1016/j.rser.2018.05.068 51. alcarria, r., bordel, b., robles, t., martín, d., and manso-callejo, m. á. (2018). a blockchain-based authorization system for trustworthy resource monitoring and trading in smart communities. sensors 18:3561. https://doi.org/10.3390/s18103561 52. sayeed, s., and marco-gisbert h. “assessing blockchain consensus and security mechanisms against the 51% attack,” applied sciences, vol. 9(9), pp. 1788, 2019. 53. oksiiuk, o., and dmyrieva, i. "security and privacy issues of blockchain technology," 2020 ieee 15th international conference on advanced trends in radioelectronics, telecommunications and computer engineering (tcset), 2020, pp. 1-5. 54. ullah, a., siddiquee, s. m. s., hossain, m. a., ray, s. k. (2020). an ethereum blockchain-based prototype for data security of regulated electricity market. inventions 2020, 5(4), 58; https://doi.org/10.3390/inventions5040058 55. lee, w.m. (2019). using the meta mask chrome extension. beginning ethereum smart contracts programming; springer: new york, ny, usa, 2019; pp. 93–126. ttps://doi.org/10.1007/978-1-4842-5086-0_5 56. wu j, tran n. (2018). application of blockchain technology in sustainable energy systems: an overview. sustainability 2018, 10(9), 3067; https://doi.org/10.3390/su10093067 https://doi.org/10.3390/s21062024 https://www.alcimed.com/en/alcim-articles/blockchain-technology-for-the-energy-sector-significant-potential-but-still-key-challenges-to-overcome/ https://www.alcimed.com/en/alcim-articles/blockchain-technology-for-the-energy-sector-significant-potential-but-still-key-challenges-to-overcome/ https://doi.org/10.3389/fenrg.2021.671133 https://doi.org/10.3390/s18103561 https://doi.org/10.3390/inventions5040058 https://doi.org/10.1007/978-1-4842-5086-0_5 https://doi.org/10.3390/su10093067 a review on blockchain technology for distribution of energy 70 57. van cutsem, o., dac, d. h., boudou, p., and kayal, m. (2020) “cooperative energy management of a community of smart-buildings: a blockchain approach,” international journal of electrical power & energy systems, vol. 117, p. 105643, 2020. 58. pee, s. j., kang, e. s., song, j. g., and jang, j. w. (2019). blockchain-based smart energy trading platform using the smart contract. 2019 international conference on artificial intelligence in information and communication (icaiic) (okinawa: ieee), 322–325. doi: 10.1109/icaiic.2019.8668978 59. yinan, li, wentao, y., ping h., chang c., xiaonan w. (2019). design and management of a distributed hybrid energy system through smart contract and blockchain. applied energy, vol. 248, pp. 390–405, 2019. 60. watanabe, h., fujimura, s., nakadaira, a. (2016). blockchain contract: securing a blockchain applied to smart contracts. in proceedings of the 2016 ieee international conference on consumer electronics (icce), las vegas, nv, usa, 7–11 january 2016; pp. 467–468. 61. zheng, z.b., xie, s.a., dai, h.n., chen, x.p., and wang, h.m. (2017). an overview of blockchain technology: architecture, consensus, and future trends. in proceedings of the 2017 ieee international congress on big data (big data congress), honolulu, hi, usa, 25–30 june 2017; pp. 557–564. 62. iskakova, a., nunna, h. s. v. s.k., and siano, p. (2020). ethereum blockchain-based peer-to-peer energy trading platform. 2020 ieee international conference on power and energy (pecon). doi:10.1109/pecon48942.2020.9314591. 63. albrecht, s, reichert, s., schmid, j., strüker, j., neumann, d., and fridgen, d. (2018). dynamics of blockchain implementation a case study from the energy sector. proceedings of the 51st hawaii international conference on system sciences, 2018. http://dx.doi.org/10.1109/pecon48942.2020.9314591 international journal of engineering materials and manufacture (2022) 7(1) 1-12 https://doi.org/10.26776/ijemm.07.01.2022.01 n. momeni 1 , k. javadifar 1 , m. a. patrick 1 , m. h. hasan 1 and f. m. chowdhury 2 1 department of electrical, computer and biomedical engineering faculty of engineering and architectural sciences m5b2k3, ryerson university, canada 2 formerly department of community medicine marks medical college, dhaka, bangladesh. e-mail: nika.momeni@ryerson.ca reference: momeni, et al. (2022). a review on gold nanoparticles-based biosensors in clinical and non-clinical applications. international journal of engineering materials and manufacture, 7(1), 1-12. a review on gold nanoparticles-based biosensors in clinical and nonclinical applications nika momeni, kayla javadifar, maria a. patrick, muhammad h. hasan and farhana m. chowdhury received: 13 august 2021 accepted: 24 november 2021 published: 01 january 2022 publisher: deer hill publications © 2022 the author(s) creative commons: cc by 4.0 abstract gold nanoparticles (gnp) acquire unique properties that have made significant contributions to clinical and nonclinical fields, specifically in the application of gnp’s for designing biosensor devices in which exhibit novel functional properties. many properties of gnp’s are reviewed in this literature including optical properties, biocompatibility, conductivity, catalytic properties, high surface-to-volume ratio, and high density of the gnps, that make them excellent in the application of constructing gnp-based biosensors. this literature review covers a specific comparison between the optical, electrochemical, and piezoelectric biosensors, as these are the three most common gnp-based biosensors. optical biosensors are optimal due to their ability to cater to surface modification, which then leads to the ability for selective bonding. furthermore, with the use of gnp and the sensor's non-invasive and non-toxic method of use, high-resolution images and signals can be formed. the sensitivity and specificity of electrochemical biosensors with the conductivity of gnps, the electrodes of this stable biosensor can detect tumour markers in the human body. piezoelectric biosensors are mass sensitive sensors and with the use of gnp, it amplifies the changes in mass. through this, these sensors progress to be immunosensors which determine microorganisms and macromolecular compounds. as well, this review will conclude with an outline of present and future research recommendations for real-world application of the three gnp-based biosensors discussed. keywords: gold nanoparticles, biosensors, sensitivity, selectivity 1 introduction in canada, one of the leading causes of high mortality rates for many people is the delay in recognizing symptoms of diseases and seeking necessary medical attention. for certain diseases prevalent in the current day, the longer the patient waits to seek medical attention, the more fatal the consequences are to the patient, their friends, family, and the economy [1]. one of the primary reasons for these consequences is due to the lack of proper health monitoring of the patients during these wait times [1]. the delay in healthcare monitoring has economic consequences such as reduced productivity, reduced ability to work caused by untreated medical conditions, increased absenteeism. as well, the advance of disease during a delay in patient health monitoring can mean having to undergo longer, more complex and intensive treatments than would be required if the problem symptoms were identified sooner. thus, leading to a poorer medical outcome. over 15 years from 1994-2009, changes in wait times for cardiovascular care are associated with approximately 662 potentially avoidable deaths, if patients were monitored during their wait times [1]. through this research and better implementation of cardiovascular care, patients' cardiovascular health has been increasingly monitored during wait times using a plethora of biosensing devices (e.g. halter monitors, etc) before cardiovascular surgery, resulting in a slow reduction in avoidable mortality. cardiovascular health monitoring is only one of many applicable examples of how biosensing devices show promising change for patients, healthcare, and the economy [2]. biosensors have a wide use in clinical and non-clinical applications; they are able to be used for the detection of diseases, diagnosis, treatment, patient health monitoring, and human health management. the earlymomeni et al. (2022): international journal of engineering materials and manufacture, 7(1), 1-12 2 stage detection and diagnosis of disease, with a treatment plan to combat the disease and monitoring of the patient's help, has proven to be the most proactive way to manage the life of a patient [2]. to process early-stage detection, the use of functionality must have properties that are highly sensitive to detect minuscule differences and that are highly responsive. this can be achieved through the use of biosensors. a biosensor is a device that is used for analyzing biological samples which helps to find biomarkers in the sample provided [3]. through the sensor, one can see molecules such as proteins, dna, and rna that are expressed in excess or mutilated [4]. this sensor has the ability to convert chemical, biological, or biochemical responses into electrical signals [5]. the sensors are able to sense biological structures such as cells, and nucleic acids but also have the ability to measure the biological process and any physical changes to the patient [6]. essentially, biosensors consist of 3 essential components where a bioreceptor reads the sample that is provided, which is then passed to the transducer which will be inputted into the electronic unit system which consists of the amplifier, processor, and display. in pairing with the biosensors, various metal nanoparticles and nano dimensional conducting polymers have been used in biosensors [3]. more favourably, gold nanoparticles (gnps) are used in laboratories due to their unique properties, and the roles in which they play in different sensing systems [3]. gnps are favourable because of their unique optical properties and ease of use with various biomarkers in aqueous solutions [3]. additionally, gnps have a more stable immobilization of large amounts of biomolecules retaining their bioactivity and they permit fast and direct electron transfer between a variety of electroactive species and materials [3]. furthermore, the light-scattering properties and extremely large enhancement ability of the local electromagnetic field enables gnps to be used as signal amplification tags in diverse biosensors [3]. in this paper, three types of gold nanoparticles used in biosensors which are optical, electrochemical, and piezoelectric will be compared. furthermore, there will be an analysis on which type of gold nanoparticles is most suitable for different applications. moreover, there is a discussion on the advantages, disadvantages, and limitations each of the gold nanoparticles has for various applications and how it can be applied to be used to the best of its abilities. according to the three types of biosensors, the gnpbased biosensors are discussed separately with images showcasing the characteristics of each sensor. 2 gold-nanoparticle (gnp) biosensors biosensors are increasingly integrating into clinical and non-clinical applications [7]. their general composition consists of a functional bioreceptor, transducer, and an analog-to-digital (a/d) converter [8]. bioreceptors are materials that interact with a bioanalyte, where the transducer transforms a signal that is produced by this interaction into a signal that can be quantified and analyzed, as seen in figure 1 [8]. to generalize, biosensors analyze specific, quantitative information using a bioreceptor. figure 1 displays how a signal is produced when a biological element such as an enzyme, dna, or an antibody, recognizes the analyte it is trying to combine with. examples of an analyte are a substrate, complementing dna, or antigen. the bioreceptor must be sensitive to the target analyte to generate a signal, as clearly shown in figure 1 [8]. applications of biosensors stem anywhere from pathology to pollution monitoring, as seen in figure 2 [9]. as of recently, gold nanoparticles (gnps) have been applied to the production of biosensors. due to their unique properties, they show great potential for the development of these sensors to produce accurate analytics, especially on a molecular scale [10]. gnps increase the sensitivity, reliability, and selectivity of the biosensing process, however, although gnp-based biosensors are rapidly integrating into different sectors, they are still in the early stages of being used in real-world applications [10]. in general, there are three different types of biosensors: optical, electrochemical, and piezo-electric [11]. this journal explores these three types and the application of gnps to these biosensors, and the studies are done to examine their effectiveness. figure 1: visual representation of functionality of biosensors and how they produce a signal [8]. a review on gold nanoparticles-based biosensors in clinical and non-clinical applications 3 3 optical biosensors to put it simply, optical sensors measure the changes in light (photons) [3]. they are the most common type of biosensor and interact with many biological materials, such as enzymes, antibodies, antigens, receptors, or cells/tissues, to produce a signal. the signal they produce is proportional to the concentration of the measured analyte (examples listed above) [12]. figure 3 provides a visual representation of the composition of optical biosensors. it shows that they are analytical devices consisting of a biorecognition sensing element fused with an optical transducer system [12]. 3.1 functionality gnp-based optical biosensors issue a spectrum of possibilities due to the collective oscillation of conduction of band electrons known as plasmons. these oscillations occur as a result of electromagnetic radiation applied externally [13]. of all the optical transducers of these biosensors, the surface plasmon resonance (spr) modality is an attractive choice for experimental investigation because of the interaction between electromagnetic waves and the conduction electrons in metals (in this case gold). sprs are used in the classification of physiochemical changes of thin films on a metal surface, as seen in figure 4 [3]. molecules of the target analyte bind to the surface of the metal film, causing change in the dielectric constant. this also leads to a change in the reflection as a result of the laser and the metal-liquid surface [3]. it is important to note that the gold-nanoparticles (gnps) contain an extremely sensitive dielectric constant due to the gold material, adding to the list of reasons why gnps have been investigated in sprs for more accurate analyses [3]. figure 2: applications of biosensors and the different sectors they are used in [9]. figure 3: flow chart of optical biosensor composition and how a signal is produced [12]. momeni et al. (2022): international journal of engineering materials and manufacture, 7(1), 1-12 4 figure 4: diagram of the oscillation from excited electrons from electromagnetic radiation(resonance). 3.2 properties of gnps in optical biosensors as mentioned, gold-nanoparticles display a range of optical properties that are explained by plasmonic effects, hence the desirability of the surface plasmon resonance (spr) technique. the optical properties of gnps are capable of altering their size, shape, composition, and coupling with other plasmonic nanoparticles in order to display the intensity of colour under light [14]. gold-nanoparticles are also able to amplify other optical signals, which is key in biosensor development [14]. in addition to their optical properties, gnps are advantageous because of their biocompatibility, inertness, easy use, and intense colours [14]. the specific property that gnps possess that cater to the development of biosensors is surface modification. through a variety of biomolecules, such as proteins, the development of biosensor platforms is possible. this is accomplished as the biomolecules form stable bonds leading to the creation of selective bonding [14]. furthermore, there are a variety of biosensing practices (localized surface plasmon (lspr), surface-enhanced raman scattering (sers), fluorescence, etc), but this section focuses specifically on surface plasmon resonance. surface plasmon resonance can be modified into different sizes, shapes, and surface coupling among the nanoparticles, as mentioned above. this is achieved through the excitation of free electrons within gold-nanoparticles once irradiated with light. following non-propagating oscillations of spr. gold surface plasmons are also greatly absorbent (with light) and contain a strong scattering of light; this property makes gnps a focal point in the development of biological sensing and imaging probes [14]. 3.3 applications: optical biosensors in colorimetric bioassays optical biosensors are emerging in the biomedical engineering field at a rapid pace. generally, optical biosensing/imaging is a non-invasive and non-toxic method in developing high-resolution images and signals. through the integration of gold-nanoparticles, these output responses have become significantly more sensitive, specific, contrast, and multi exhibitable. over the development of gnp optical biosensors, scientists have developed a spectrum of gold nanostructures of which each contains its range of optical properties, such as nanospheres, nanorods, and nanoshells, to name a few [15]. figure 5 displays the developing applications of gnp-optical biosensors and the three methods (lspr, sers, and fluorescence) mentioned above with respect to optical biosensing and optical bioimaging [15]. focusing on lspr optical biosensing, colorimetric bioassays are a successful example of these devices. they function as a result of wavelength shift from changes in interparticle distance. through gnps, the selectivity and the sensitivity of the device improve leading to greater control of interparticle forces. another advantage to this device is its simplicity in digital monitoring. the assays can be used with smartphone imaging for convenience and nearpatient testing platforms. figure 6 provides an example of a microfluidic colorimetric bioassay used in e. coli detection [15]. the device is composed of 2 mixing channels: one for separation and the other for detection, the device is based on horseradish peroxidase (hrp), hydrogen peroxide, and tyramine. once the aggregation process has been undergone, the size of the gnps exponentially grows (in terms of wavelength) from ~13 nm to ~670 nm. this colour change is detected through a smartphone app. in conclusion, gnps will continue to integrate into optical biosensing/imaging techniques due to their non-invasive nature, specificity, high sensitivity, and reliability to provide/conduct accurate analyses. a review on gold nanoparticles-based biosensors in clinical and non-clinical applications 5 figure 5: applications of optical biosensing/bioimaging based on gnps [15]. figure 6: smartphone based gnp optical biosensor for colorimetric assays for e. coli. (a) labelled diagram of the biosensor; (b) result of mixing gnps with various cross-linking agents; (c) hues of colour changed; (d) tem image before aggregation; (e) tem image after aggregation; (f) schematic of functionality of biosensor; (g) spr band changes [15]. 4 electrochemical biosensors electrochemical biosensors produce useful signals as a result of the conversion of biological binding events into these signals. they provide fast, simple, and low-cost detection properties. additionally, the biocompatibility, conductivity, and catalytic properties make these types of biosensors, specifically gnp electrochemical biosensors, desirable for further research [3]. 4.1 functionality in electrochemical biosensors, gnps play many possible roles including electron wires, an immobilization platform, and an electrocatalyst. beginning with gnps as electron wires (electron transfer), the fundamental concept of this role revolves around bioelectrochemical reactions, in other words, redox reactions. the electron transfer that occurs momeni et al. (2022): international journal of engineering materials and manufacture, 7(1), 1-12 6 between the electrode surface and the redox protein is the main reaction under scrutiny. a fallback of the interaction between electrodes and the active centres of oxidoreductases in the surrounding thick insulating protein that encompasses these active centres. this protein shell blocks the electron centre for these reactions, which results in a lack of analytics. however, the conductivity of gnps enhances the electron transfer, regardless of the protein shell, and so the gnps act as “electron wires” since they connect and improve the interaction between active centres of proteins and electrodes of the biosensor. electrochemical biosensors function based on bioelectrochemistry. specifically, the bioactivity, stability, and quantity of biological recognition elements that are immobilized on the electrodes of these sensors. this process usually results in denaturation and loss of bioactivity in the absorption of biomolecules that are placed directly on that surface of bulk materials. the benefits of gnps to resolve these losses are their absorption properties. the absorption of biomolecules on the surface of gnps leads to the maintenance of bioactivity and stability as a result of the biocompatibility of gnps and their high surface free energy. as mentioned in varying sections of this review, gnps contain a higher surface area than flat gold surfaces. this allows for a larger protein loading and greater sensitivity. the final role that gnps play in electrochemical biosensors is an electrocatalyst. although gold is chemically inert, gnps showcase great promise for catalytic activity. these catalytic properties stem from the gnp’s quantum scale dimension, large surface-volume ratio, and interface-dominated properties. these qualities are capable of decreasing overpotentials of electrochemical reactions, reverse some redox reactions, and could potentially allow the fabrication of enzyme-free biosensors. it should be noted that the properties listed of each role of gnps in electrochemical biosensors will be explained in the next section, and that quantum scale dimension is beyond the scope of this review and will not be discussed herein. 4.2 properties of gnps in electrochemical biosensors as seen in section 3.1, there are many desirable properties of gnps used for each aspect of electrochemical biosensors. to list the ones above, conductivity, biocompatibility, high surface free energy, sensitivity, selectivity, and high surface-volume ratio. the conductivity of gnps allows and enhances electrochemical reactions to take place, which is essential to the fundamentals of electrochemical biosensors. biocompatibility and the high surface free energy of these special nanoparticles allow for absorption to take place in these sensors to maintain the bioactivity and their stability. the sensitivity and selectiveness allow for selective electrochemical analysis as well as their high surface area that leads to improved sensitivity of these devices. finally, the high surface-volume ratio is among the many properties that cause catalytic behaviours in gnps. these gnp properties advance the electrochemical analytical characteristics and overall enable this biosensor to play many important roles. 4.3 applications: electrochemical biosensors in clinical diagnosis electrochemical biosensors are used to detect tumour markers in the human body. focusing specifically on prostate cancer biomarkers known as prostate-specific antigen, or psa [16]. the electrodes of the electrochemical biosensor used in this biomarker detection are composed of gold nanoparticles/graphene oxide, anti-total psa monoclonal antibody, and anti-free psa antibody. it became evident that this biosensor possesses a high sensitivity toward total and free psa, as well as high selectivity for psa in comparison to other tumour markers. electrochemical biosensors are desirable devices for detecting tumour markers due to their simplicity, fast response, and miniaturization, and the use of gnps has added to this desirability to improve the sensitivity of these biosensors [16]. additionally, since gnps are inert/stable, biocompatibility/less hazardous, and simple, they can enhance catalytic activity, and conductivity [16], as described in section 3.2. evidently, the electrochemical biosensor amplifies the signals received from the tumour markers. figure 7 [16] provides a visual representation of how a biosensor records and amplifies these signals. it is noted that the electrochemical signals that are recorded are directly proportional to the sandwich-like system on the electrode surface. due to the properties of gnps and the loading of anti-free psa antibodies, specific recognition, the antibody’s high binding affinity, and the selectivity and sensitivity of the sensor are improved [16]. figure 8 [16] provides a sideby-side comparison of the gnp/graphene oxide electrochemical biosensor discussed in this paper. the results stem from the analysis of six patients where these graphs indicate that selectivity is an important characteristic to consider in biosensors. 5 piezoelectric biosensors generally, piezoelectric biosensors are capable of measuring the mass changes as a result of the biological recognition process. the principle by which this biosensor functions, stems from the relation between mechanical stress and an electrical charge in a solid, first discovered in 1880 by the curie brothers. it was concluded that when mechanical stress is applied to a crystal, there are electrical changes present with a voltage that is proportional to the stress [3, 17]. there is a diverse range of materials that showcase the piezoelectric principle such as quartz (sio2) due to the quartz crystal microbalance (qcm). since gnps are high in density as well as surface-volume ratios, they can amplify mass changes within crystals, research is being conducted on coupling gnps with the qcm process to improve analytical sensitivity [3]. a review on gold nanoparticles-based biosensors in clinical and non-clinical applications 7 figure 7: (a) synthesis of graphene oxide, gnps and anti-total psa antibody; (b) anti-total psa antibody is attached to the surface of the electrode of the biosensor to capture antigens; (c) following a sandwich-like system, the resulting product from (b) is incubated with graphene oxide and gnps [16]. figure 8: comparison of (a) total and (b) free psa concentration deduction results obtained by electrochemical sensor [16]. 5.1functionality as mentioned above, piezoelectric biosensors are mass-sensitive devices and gnps increase the analytical sensitivity of these devices through the amplification of mass change [3]. it is important to note that the process of a material under mechanical stress produces a voltage, and also works in the opposite direction (a voltage given to the surface of material causes mechanical stress). in biosensors, the alternating voltage is given on a surface by two electrodes. the alternating voltage produces mechanical oscillations of the material and the frequency of the oscillations is measured and recorded as the oscillation circuit processes. the change in frequency is a result of the analyte on the surface of the electrodes (on the crystal) [18]. regarding biosensors specifically, the piezoelectric effect is an ideal platform for the development of these devices. it can record affinity interactions independently through the sensitivity in micrograms that lead to evident changes in oscillations. the principle of affinity interaction is defined as the strength of binding between a molecule and its ligand (or binding partner) [18]. for example, the binding interaction between a protein and an inhibitor. these principles are essential to the piezoelectric effect and development of piezoelectric biosensors [18]. in regard to gnp-based piezoelectric biosensors, the nanoparticle’s ability to enhance the sensitivity of the mechanisms leads to surface and mass enhancement effects [3]. in conclusion, the sensitivity and regeneration ability of biological recognition elements on the electrode surface of these biosensors is determined by the quantity and activity of those elements on the electrode surface [3]. momeni et al. (2022): international journal of engineering materials and manufacture, 7(1), 1-12 8 5.2 properties of gnps in piezoelectric biosensors the main properties of gold nanoparticles that are attractive for the improvement of piezoelectric biosensors are as follows: surface area-volume ratio, biocompatibility, and density [3]. beginning with the first property listed above, the surface area-volume ratio is high in gold nanoparticles. in piezoelectric biosensors, this provides a large number of interaction sites to amplify the sensing surface area, meanwhile maintaining bioactivity. this overall improves the quantity, quality, and activity of biological recognition elements [3]. due to the incredible biocompatibility of gnps, the stability of biological recognition in piezoelectric biosensors is greatly improved [3]. this is a result of elemental gold’s non-harmful effect on living tissue. finally, the high-density gold nanoparticles allow for mass amplification. it is generally applied via the interaction between an analyte and the sensing surface of the gnps. 5.3 applications: piezoelectric biosensors as immunosensors piezoelectric biosensors have been developed into immunosensors. they are analytical devices used to determine macromolecular compounds and microorganisms. these biosensors consist of a biorecognition element, which in this case is an antibody. the specificity of the antibody impacts the specificity of the immunosensor as a whole [18]. generally, the specificity of the immunosensor is indicated by the specificity of the antibody and the electrode, whereas the remaining piezoelectric material will not be sensitive to any non-specific reactions with interfering compounds [18]. the fundamental principle of piezoelectric biosensors indicates that the voltage produced by mechanical stress also works in the opposed situation (mechanical stress produced by a voltage). this same principle applies to immunosensors since the immobilized antibody can recognize antigens, as well as the vice versa, as seen in figure 9 [18]. this is an indication that the device contains an immobilized antigen that can then be used for the recognition of just the antibody as the molecule under analysis, making piezoelectric immunosensors a crucial and attractive tool in diagnosing diseases [18]. the quartz crystal microbalance (qcm) process is used in conjunction with gnps due to qcm’s vast use in electronic devices as well as its commercial availability [18]. an example of gnps and qcm being used in immunosensing is a dendritic amplification immunoassay using gnps. a gnp immunocomplex was able to successfully detect low igg (immunoglobulin g) levels, approximately 3.5 ng/ml in humans [3]. using a gold electrode surface of the qcm via a protein, goat anti-human igg was immobilized. the dendritic amplification process occurs through the interaction of the goat anti-human igg with igg-functionalized gnps. as well, the successive interaction between the immunocomplex of the protein and the igg altered gnps [19]. figure 9: principle of piezoelectric immunosensors [18]. 6 advantages and disadvantages optical biosensors have improved sensitivity for instance in dna sensors with gnps responses 1000 times more sensitive than without [20]. electron transfer rate of 5000 per second with gnps while 700 per second without gnps [21]. this speed of transfer is very advantageous and in pairing with the immunity of the signal to either the electrical or magnetic interference makes optical biosensors extremely favourable to be continued to be integrated into biosensing/imaging techniques. the main disadvantage of the use of optical biosensors is the high cost of instrumentation [21]. within the last decade, there have been great advancements in the use of optical biosensors however, they cannot completely cover the conventional methods of the technology used in many fields such as the biomedical field [21]. some of these drawbacks include the ability for biomaterial immobilization where the material loss of biomolecules is observed [22] in order. furthermore, contamination and uniformity of the biosensors is also a drawback where biomolecules and chemicals leak out of the biosensors causing there to create contamination. moreover, when using optical biosensors, the selection range must be a large selection range in order for the sensor to detect the variety of biomaterials. however, with the substantial use of optical biosensors in not only the biomedical field but also in fields such as environmental monitoring, industrial and food processes, health care, clinical analysis [23], there is an increased array of testing and usage where these drawbacks can be overcome and fixed. a review on gold nanoparticles-based biosensors in clinical and non-clinical applications 9 electrochemical biosensors have improved sensitivity and stability for instance in glucose biosensors with gnps achieving detection limits of 0.18 um [24]. an nadh sensor based on gnps shows a 780 mv overpotential decrease without any electron transfer mediators [3]. furthermore, the electrochemical biosensors require less sample volume and have a cost-effective rapid response output. moreover, electrochemical biosensors enable regions with limited resources to perform healthcare diagnostics without the need for trained professionals [4]. however, with these advantages, there are some disadvantages such as the sensitivity of the electrochemical biosensors to the sample matrix effects and the lower shelf life of the sensor [4]. through future research and collaborations with hospitals, there can be greater fundamental use of the electrochemical biosensor when used for improving disease diagnosis and treatment [4]. piezoelectric biosensors have improved sensitivity for instance in dna sensors using gnps as amplification tags with a detection limit [3]. these sensors have the principle detection of identifying changes in mass [3]. in the gnps, piezoelectric biosensors play a vital role in amplifying specific changes in mass. furthermore, these biosensors are high in density, have a large surface volume ratio and are biocompatible. the advantages of these sensors are that they contain an improved sensitivity, as listed in table 1 [3]. table 1: summary of the gnp based biosensors [3] biosensor principle of detection role of gnps properties of gnps advantages application optical biosensors changes in optical (light) properties enhancement of refractive index changes larger dielectric constant, high density improved sensitivity colorimetric bioassays electrochemica l biosensors changes in electrical characteristics “electron wires”, catalysis, immobilization large area-volume ratio, biocompatibility, high surface energy, conductivity, quantum dimension, interfacedominated properties, large surface area improved sensitivity, selectivity, stability tumour biomarker detection piezoelectric biosensors changes in mass amplification of changes in mass high density, large surface-volume ratio, biocompatibility, high density improved sensitivity immunosenso rs 7 recommendations gold nanoparticle-based biosensors present promising opportunities for advancing and developing analytical systems in many clinical and non-clinical applications. this is due to the unique properties of gnps that show a variety of superior analytical behaviours. this review has demonstrated the many advantages of gnps for the three most common types of biosensors, as well as the role in which the gnps play in the process of biosensing discussed in terms of sensitivity, selectivity, reliability, etc. there are many implementations of gnp-based biosensors in different sectors. the following is a list of recent advances and future applications: 1. intracellular microrna quantification [25]. a. mass-sensitive microrna sensing surface uses a probe, established by gold-nanoparticles. b. the sensing method is to pick up on the frequency shift of qcm (quartz crystal microbalance) sensors (piezoelectric biosensors concept). c. qcm sensors are compatible with different operating conditions (gaseous or liquid mediums) [26] making it a useful technique in health care. d. gold-nanoparticles amplify the signal while coupled with an enzymatic amplification process. the sensor detects microrna-203 in mcf-7 cells (typically seen in tumour growth) with exceptional sensitivity and selectivity. 2. localized surface plasmon field fibre-optic biosensor [27]. a. the benefits of gold-nanoparticles for localized plasmon resonance (lspr) optical sensors is the depth of penetration of surface plasmons affecting the sensitivity. b. the size of the gnp affects the penetration depth of the lspr biosensor. c. ultimately, the greatest diameter exhibited the greatest penetration depth indicating that the size of the gnp directly impacts the functionality of the lspr sensor. 3. enhancement of direct electron transfer of glucose oxidase [28]. a. gold nanoparticles are used with titanite nanotubes (tnt). tnt aids in the direct electron transfer of glucose oxidase. b. combined with the gnp-tnt nanocomposite is an ionic liquid (bromated 1-decyl-3-methyl imidazole) to immobilize the structure and further promote the electron transfer between glucose oxidase and the electrode. volumetric results showed that there is a strong electrocatalytic capability towards glucose electron transfer rate constant of 7.1 s-1 at 180 mvs-1. momeni et al. (2022): international journal of engineering materials and manufacture, 7(1), 1-12 10 c. high sensitivity in the calibration for glucose 5.1a mm-1. d. the measured parameters indicate superior analytical performance of the biosensor compared to those developed with other nanoparticles. as well, increased biocompatibility and electrical conductivity of the nanocomposite became evident. 4. microfluidic-based biosensor [29]. a. one of the fastest-growing technologies among biosensors. b. gold nanoparticles play the main role in their development in order to promote biomolecular detection with higher sensitivity and effectiveness. 5. gold-nanoparticles for biosensors in healthcare [30]. a. scientists define an elite group of nanomaterials, including graphene, cnts (carbon nanotubes), zno, and gold. these nanomaterials are used in the modification of electrodes for electrochemical sensing of analytes. b. in addition to healthcare, these biosensors show promise for on-site detection of explosives. c. development of genosensor, immunosensor, and enzymatic biosensors are in progress using the elite group of nanomaterials. gold shows the greatest promise in the detection of immunological molecules and is more commonly used in immunological sensing. d. the best results are shown when a combination of these materials is used with the electrodes. this promotes great stability, reproducibility, and sensitivity, and signal amplification as a result of electrochemical and electrocatalytic properties of these materials. e. detection of glucose, igg, ige, sequence-specific dna, amino acids, viruses and bacteria. 6. plasmonic biosensors [14]. a. gnps allow for the altercation of size, shape, composition, coupling of intense colours under light, enhance optical signals (i.e. fluorescence and raman scattering, and improve plasmonic properties in specific optical systems. b. patterning gnps on electrodes (lspr). c. controlling gap distance between particles for sers-based biosensor. d. in a fluorescent signal, controlling the distance between a gnp and a fluorophore. as well as the control of the dispersion stability in the development of colorimetric biosensors. e. used in the detection of cancer biomarkers [31]. 8 conclusions 1. gold colloids are becoming a key component to many industries such as health care, food, engineering, etc. 2. gold particles are used in immunochemistry, photothermal therapy agents and detection of cancerous cells these properties are now being applied to engineering and biosensing applications. 3. biosensors are becoming increasingly relevant in the food industry to ensure quality and safety. as well as the fermentation industry for the detection of glucose concentrations, and metabolic engineering in the monitoring of cellular metabolism. in general, the use of biosensors has diverse applications due to their diverse functionality. 4. gold nano-particle properties include biocompatibility, conductivity, catalytic properties, high surface-tovolume ratio, and high density. this makes the nanomaterial grow exceptionally in the bioassay field. 5. it was discussed how these distinct properties can make each kind of biosensor most effective for specific applications, such as colorimetric bioassays, tumour biomarker detection, and immunosensors. 6. the field of research around gnp-based biosensors is still in its infancy in terms of real-world applications, as widespread use is not currently possible since there remain challenges to be addressed before the full potential of applications can be realized. in order to fully exploit the potential applications of gnp-based biosensors, the following research areas should be given attention: a. design of gnp-based biosensors for high throughput and multiplexed identification of biomarkers. b. production of gnps with long-term sustainability in a variety of environments. c. nanostructure and size of the gnps, as this affects various optical and electrical properties. d. improvement for design and synthesis of gnps with better-defined geometrical properties that will promote more applicable uses. e. compositing other nanomaterials with gnps; hybrids of other nanomaterials in combination with gnps have the potential to acquire more distinct, and useful properties. f. improvement for the analytical performance of gnps at the present stage (e.g. preventing non-specific adsorption of biomolecules or shortening the length of analysis time). references 1. b. barua, t. jackson, and n. esmail, “the effect of wait times on mortality in canada,” fraser institute, may2014. [online]. available: https://www.fraserinstitute.org/. [accessed: 19-apr-2021]. 2. p. mohankumar, j. ajayan, t. mohanraj, and r. yasodharan, “recent developments in biosensors for healthcare and biomedical applications: a review,” researchgate, jul-2020. [online]. available: a review on gold nanoparticles-based biosensors in clinical and non-clinical applications 11 https://www.researchgate.net/publication/343356920_recent_developments_in_biosensors_for_healthcare_an d_biomedical_applications_a_review. [accessed: 19-apr-2021]. 3. y. li, h. j. schluesener, and s. xu, “gold nanoparticle-based biosensors,” springerlink, mar-2010. [online]. available: https://link.springer.com/article/10.1007/bf03214964. [accessed: 19-apr-2021]. 4. g. ghosh, “early detection of cancer: focus on antibody coated metal and magnetic nanoparticle-based biosensors,” sensors international, 13-oct-2020. [online]. available: https://www.sciencedirect.com/science/article/pii/s2666351120300504. [accessed: 19-nov-2021]. 5. l. c. clark and c. lyons, “electrode systems for continuous monitoring in cardiovascular surgery,” annals of the new york academy of sciences, 31-oct-1962. [online]. available: https://pubmed.ncbi.nlm.nih.gov/14021529/. [accessed: 19-apr-2021]. 6. v.-d. t and b. callum, “biosensors and biochips: advances in biological and medical diagnostics,” fresenius' journal of analytical chemistry, mar-2000. [online]. available: https://pubmed.ncbi.nlm.nih.gov/11225766/. [accessed: 19-apr-2021]. 7. d. a. giljohann , d. s. seferos, w. l. daniel, m. d. massich, p. c. patel, and c. a. mirkin, “gold nanoparticles for biology and medicine,” angewandte chemie (international ed. in english), 26-apr-2010. [online]. available: https://pubmed.ncbi.nlm.nih.gov/20401880/. [accessed: 19-apr-2021]. 8. h. liu, j. ge, e. ma, and l. yang, “advanced biomaterials for biosensor and theranostics,” researchgate, jan2019. [online]. available: https://www.researchgate.net/publication/330342204_advanced_biomaterials_for_biosensor_and_theranostic s. [accessed: 19-apr-2021]. 9. a. mandal, “biosensor applications,” news, 26-feb-2019. [online]. available: https://www.newsmedical.net/health/biosensor-applications.aspx. [accessed: 19-apr-2021]. 10. s. das, s. mitra, s. m. p. khurana, and n. debnath, “nanomaterials for biomedical applications,” taylor & francis, 23-jan-2014. [online]. available: https://www.tandfonline.com/doi/full/10.1080/21553769.2013.869510. [accessed: 19-apr-2021]. 11. p. jiang, y. wang, l. zhao, c. ji, d. chen, and l. nie, “applications of gold nanoparticles in non-optical biosensors,” nanomaterials (basel, switzerland), 26-nov-2018. [online]. available: https://www.ncbi.nlm.nih.gov/pmc/ahttps://www.ncbi.nlm.nih.gov/pmc/articles/pmc6315477/rticles/pmc63 15477/. [accessed: 19-nov-2021]. 12. p. damborský, j. švitel , and j. katrlík, “optical biosensors,” essays in biochemistry, 30-jun-2016. [online]. available: https://pubmed.ncbi.nlm.nih.gov/27365039/. [accessed: 19-apr-2021]. 13. c. j. murphy, a. m. gole, s. e. hunyadi, j. w. stone, p. n. sisco, a. alkilany, b. e. kinard, and p. hankins, “chemical sensing and imaging with metallic nanorods,” university of illinois urbana-champaign, 19-jun-2015. [online]. available: https://experts.illinois.edu/en/publications/chemical-sensing-and-imaging-with-metallicnanorods. [accessed: 19-apr-2021]. 14. j.-h. lee, h.-y. cho, h. k. choi, j.-y. lee, and j.-w. choi, “application of gold nanoparticle to plasmonic biosensors,” international journal of molecular sciences, 11-jul-2018. [online]. available: https://pubmed.ncbi.nlm.nih.gov/29997363/. [accessed: 19-apr-2021]. 15. p. si, n. razmi, o. nur, s. solanki, c. m. pandey, r. k. gupta, b. d. malhotra, m. willander, and a. de la zerda, “gold nanomaterials for optical biosensing and bioimaging,” nanoscale advances, 14-apr-2021. [online]. available: https://pubs.rsc.org/en/content/articlelanding/2021/na/d0na00961j. [accessed: 19-nov-2021]. 16. z. akbari jonous, j. s. shayeh, f. yazdian, a. yadegari, m. hashemi, and m. omidi, “an electrochemical biosensor for prostate cancer biomarker detection using graphene oxide-gold nanostructures,” engineering in life sciences, 07-feb-2019. [online]. available: https://www.ncbi.nlm.nih.gov/pmc/articles/pmc6999480/. [accessed: 19-apr-2021]. 17. p. mehrotra, “biosensors and their applications a review,” journal of oral biology and craniofacial research, 06-jan-2016. [online]. available: https://www.ncbi.nlm.nih.gov/pmc/articles/pmc4862100/. [accessed: 19apr-2021]. 18. m. pohanka, “overview of piezoelectric biosensors, immunosensors and dna sensors and their applications,” materials (basel,switzerland), 19-mar-2018.[online]. available: https://www.ncbi.nlm.nih.gov/pmc/articles/pmc5873027/. [accessed: 19-apr-2021]. 19. x. chu, z.-l. zhao, g.-l. shen, and r.-q. yu, “quartz crystal microbalance immunoassay with dendritic amplification using colloidal gold immunocomplex,” sensors and actuators b: chemical, vol. 114, no. 2, pp. 696–704, aug. 2005. 20. l. he, m. d. musick, s. r. nicewarner, f. g. salinas, s. j. benkovic, m. j. natan, and c. d. keating, “colloidal au-enhanced surface plasmon resonance for ultrasensitive detection of dna hybridization,” acs publications, 08-sep-2000. [online]. available: https://pubs.acs.org/doi/10.1021/ja001215b. [accessed: 19-apr-2021]. 21. y. weizmann, f. patolsky, e. katz, and i. willner, “amplified dna sensing and immunosensing by the rotation of functional magnetic particles,” acs publications, 04-mar-2003. [online]. available: https://pubs.acs.org/doi/10.1021/ja028850x. [accessed: 19-apr-2021]. momeni et al. (2022): international journal of engineering materials and manufacture, 7(1), 1-12 12 22. d. dey and t. goswami, “optical biosensors: a revolution towards quantum nanoscale electronics device fabrication,” journal of biomedicine & biotechnology, 29-oct-2011. [online]. available: https://pubmed.ncbi.nlm.nih.gov/22131802/. [accessed: 19-apr-2021]. 23. s. a. hussain, p. k. paul, d. dey, d. bhattacharjee, and s. sinha, “immobilization of single strand dna on solid substrate,” chemical physics letters, vol. 450, no. 1-3, pp. 49–54, nov. 2007. 24. d. branton, d. w. deamer, a. marziali, h. bayley, s. a. benner, t. butler, m. di ventra, s. garaj, a. hibbs, x. huang, s. b. jovanovich, p. s. krstic, s. lindsay, x. s. ling, c. h. mastrangelo, a. meller, j. s. oliver, y. v. pershin, j. m. ramsey, r. riehn, g. v. soni, v. tabard-cossa, m. wanunu, m. wiggin, and j. a. schloss, “the potential and challenges of nanopore sequencing,” nature biotechnology, 26-oct-2008. [online]. available: https://pubmed.ncbi.nlm.nih.gov/18846088/. [accessed: 19-apr-2021]. 25. s. andreescu and l. a. luck, “studies of the binding and signaling of surface-immobilized periplasmic glucose receptors on gold nanoparticles: a glucose biosensor application,” analytical biochemistry, vol. 375, no. 2, pp. 282–290, jan. 2008. 26. y. guo, y. wang, g. yang, j.-j. xu, and h.-y. chen, “microrna-mediated signal amplification coupled with gnp/dendrimers on a mass-sensitive biosensor and its applications in intracellular microrna quantification,” biosensors & bioelectronics, 15-nov-2016. [online]. available: https://pubmed.ncbi.nlm.nih.gov/27311115/. [accessed: 19-apr-2021]. 27. a. alassi, m. benammar, and d. brett, “quartz crystal microbalance electronic interfacing systems: a review,” sensors (basel, switzerland), 05-dec-2017. [online]. available: https://pubmed.ncbi.nlm.nih.gov/29206212/. [accessed: 19-apr-2021]. 28. r. bharadwaj, s. mukherji, and s. mukherji, “probing the localized surface plasmon field of a gold ...,” researchgate, jun-2016. [online].available: https://www.researchgate.net/publication/282796834_probing_the_localized_surface_plasmon_field_of_a_g old_nanoparticle-based_fibre_optic_biosensor. [accessed: 19-apr-2021]. 29. r. zhao, x. liu, j. zhang, j. zhu, and d. k. y. wong, “enhancing direct electron transfer of glucose oxidase using a gold nanoparticle: titanate nanotube nanocomposite on a biosensor,” macquarie university, 16-jan-2017. [online]. available: https://researchers.mq.edu.au/en/publications/enhancing-direct-electron-transfer-ofglucose-oxidase-using-a-gol. [accessed: 19-apr-2021]. 30. t. lakshmipriya, u. hashim, s. c. b. gopinath, and n. azizah, “microfluidic-based biosensor: signal enhancement by gold nanoparticle,” microsystem technologies, 16-jul-2016. [online]. available: https://link.springer.com/article/10.1007/s00542-016-3074-1. [accessed: 19-apr-2021]. 31. s. kumar, w. ahlawat, r. kumar, and n. dilbaghi, “graphene, carbon nanotubes, zinc oxide and gold as elite nanomaterials for fabrication of biosensors for healthcare,” biosensors & bioelectronics, 15-aug-2015. [online]. available: https://pubmed.ncbi.nlm.nih.gov/25899923/. [accessed: 19-apr-2021]. 32. l. xiao, a. zhu, q. xu, y. chen, j. xu, and j. weng, “colorimetric biosensor for detection of cancer biomarker by au nanoparticle-decorated bi 2 se 3 nanosheets,” acs applied materials & interfaces, 06-feb-2017. [online]. available: https://pubmed.ncbi.nlm.nih.gov/28164701/. [accessed: 19-apr-2021]. international journal of engineering materials and manufacture (2020) 5(1) 2-11 https://doi.org/10.26776/ijemm.05.01.2020.02 a. mirzajavadkhan, s. rafieian and m. h. hassan department of mechanical engineering ryerson university, canada e-mail: hasibulhasan@ryerson.ca reference: mirzajavadkhan, a., rafieian, s. and hassan, m. h. (2020). toxicity of metal implants and their interactions with stem cells: a review. international journal of engineering materials and manufacture, 5(1), 2-11. toxicity of metal implants and their interactions with stem cells: a review azin mirzajavadkhan, saba rafieian, muhammad hasibul hasan received: 04 february 2020 accepted: 18 march 2020 published: 30 march 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 abstract the development of biomaterials has increased rapidly in order to alter the fate of stem cells and use them in therapeutic applications. currently, many biomaterials are used in the biomedical industry. biomaterials act as a “nitch” which is an environment regulating the development and self-renewal behaviour of stem cells. the stem cells receive signals from the “nitch” and proceeds accordingly. in order to control the behaviour of stem cells, the chemical and physical properties of the biomaterial should be taken into consideration. this review paper focuses on the different type of metals used in biomaterials, identifying their current issues and challenges including fatigue, corrosion resistance, and the toxicity caused by metal ions released in the body. it also provides detailed explanations about the impact of various metal implants such as stainless steel, cobalt-chromium, and titanium on stem cells and the toxicity caused by the interaction of biomaterials and various trace elements with the hostile body environment. keywords: stem cells, biomaterials, toxicity, implants 1 introduction metal implants were first introduced to the medical industry in the 16th century [1,2]. with the development of metals as biomaterials, the implant surgery advanced rapidly over the next few years [3]. efforts continued to make implants with various combinations of metals but not all alloys can be implanted in the body due to corrosive reactions between the implant and the hostile body environment. thus, it is crucial to implant metals that are biocompatible, causing no harm to the host, to prevent corrosion [4-7]. a metal’s corrosion-resistance property determines the success of an implant; however, it is crucial to consider that the body has different ph values in each part so the metal implant can be corrosion resistant in one region but highly corrosive in another region [8]. in order for an implant to mimic the function of a bone in the body, it must have suitable mechanical properties and strong performances. these properties include young’s modulus, toughness, and ultimate tensile strength (uts) which are summarized in the table 1 for the three main groups of stainless-steel, cobalt based, and titanium-based metallic implants [9]. as the table shows the high young’s modulus of the implant triggers the stress-shielding effect causing the bone to bear less force compared to the implant and undergo autophagy [8]. biomaterials can change the fate of stem cells and use them in the therapeutic industry [10]. due to the great proliferation and pluripotency ability of stem cells, they are increasingly being used in wound healing and tissues recovery function using stem cell transplantation. there are two types of stem cells: embryonic stem cells (esc) and adult stem cells. adult stem cells have limited applications due to their low rate of self-renewal but embryonic stem cells are an example of stem cells undergoing osteogenic differentiation obtaining from the inner cell mass of blastocyst-stage embryos [11,12-17]. stem cells with high toxicity rate including metal-based nanoparticles and metal oxides nanoparticles (nps) are demanding in medicine and industry. their use includes cell tracking, drug targeting, coating the medical devices, sunscreens and fuel additive [15]. in order to use stem cells in regenerative medicine some aspects like proliferation, differentiation and self-renewal abilities should be considered [16]. tissue engineers aim to control the rapid increase of stem cells without differentiation and segregate cells in locations with specific lineages. 2 interaction of bone with stem cells due to the great proliferation and pluripotency ability of stem cells, they are increasingly being used in wound healing and tissues recovery function by stem cell transplantation. embryonic stem cells are an example of stem cells undergoing osteogenic differentiation obtaining from the inner cell mass of blastocyst-stage embryos [12,13,14]. bone biomaterials provide support for stem cells by creating a platform for growth and adhesion. the surface properties toxicity of metal implants and their interactions with stem cells: a review 3 directly control the adhesion, proliferation, differentiation, and migration of stem cells while the mechanical properties of the surface which stem cells grow on changes their fate (figure 1). stem cells help the maturation of osteoblasts and secretion of matrix materials and calcification; which would lead to the formation of new bones. new bone formation involves various pathways containing osteogenic differentiation of cells that leads to bone repair [17]. according to recent research great mechanical strength, degradation behaviour, and osteogenic properties are characteristics of biomaterial stem cells [14]. 3 stem cell proliferation in tissue engineering cells, including stem cells, can sense multiple extracellular signals from their microenvironment and simultaneously convert them into coherent environmental signals to regulate cell behaviour. nonspecific adhesion generally occurs through van der waals, ionic, and electrostatic forces [18]. the cell adhesion process consists of a series of cascaded reactions, including the following four steps [19]: 1. cell adhesion 2. cell spreading (proliferation) 3. cytoskeletal organization 4. formation of focal adhesions ionic bonding or van der waals forces are the initial adhesion parameters while this interaction is fast and temporary it promotes a focal adhesion plaque. a series of biological steps shown in figure 2 lead to enabling the signal adaptor proteins with the focal adhesion [20]. in tissue engineering stem cells and nanomaterials have a wide variety of applications such as nanomaterial scaffolds with the ability to resemble the fibrous nanostructure of a natural extracellular matrix (ecm). engaging fresh cells at the bone failure site combined with grafting scaffolds assures bone healing. these nanocomponent scaffolds support the mesenchymal stem cells (mscs) -multipotent cells that can distinguish into a variety of cell typesby helping in adhesion, distribution, proliferation, and differentiation (figure 3). they also allow migration and delivery of nutrients to the cell [21]. based on a research that focused on the impacts of surface roughness (1-150 nm) on embryonic stem cells. the research concluded that undifferentiated stem attached rapidly to the smooth surface (r=1 nm) and the adherence decreased as the surface roughness increased. the rough surfaces caused sudden differentiation while, the smooth surface maintained its production and selfreproduction abilities [22]. nanotopography can simply control the stem cell fate and its self-renewal properties on its own in the absence of differentiating induced agents [15]. table 1: mechanical properties of metal implants and bone [9] materials young’s modulus(gpa) ultimate tensile strength(mpa) fracture toughness (mpa√𝒎) cocrmo alloys 240 900-1540 ~100 316l stainless steel 200 540-1000 ~100 ti alloys 105-125 900 ~80 mg alloys 40-45 100-250 15-40 niti alloys 30-50 1355 30-60 cortical bone 10-30 130-150 2-12 figure 1: a) surface properties b) mechanical properties of stem cells [10]. figure 2: the signalling pathway in the adhesion of stem cells to bone biomaterials [17]. mirzajavadkhan, rafieian, and hassan (2020): international journal of engineering materials and manufacture, 5(1), 2-11 4 figure 3: adhesion, proliferation, and differentiation of bone biomaterials in contact with stem cells [17] table 2: types of neurotoxicity and their impact on individuals [36] types of neurotoxicity impact peripheral neuropathy paraesthesia, weakness, and anaesthesia with blood cobalt concentration of more than 250μg/l. sensorineural hearingloss anxiety, fatigue, headache, vertigo, tinnitus, and depression with blood a decrease of cobalt concentration from 122μg/l. to 14μg/l after revision surgery. visual impairment only able to recognize colours, poor sight, poor recognition of colours in some cases. the greatest concern in using biomedical applications such as scaffolds is biocompatibility and cytotoxicity which can jeopardize the overall health of the patients who are using biomedical implants. in this case in vitro and in vivo assessment of nanoscale materials before the clinical trial should be accomplished. an understanding of the interaction of stem cell with nanomaterial scaffold at the cellular and molecular level could facilitate the rational design of new substrates toward successful stem cell-based therapies. scaffolds possess a variety of characteristics that could activate cellular reactions. these characteristics are consist of the following:  size of nanomaterials that scaffolds are made of can alter the behaviour of stem cells including their proliferation.  surface characteristics such as the roughness effects the interactions of stem cells. nanomaterials on the surface of the scaffolds cause roughness which increases the chance of absorbing proteins and easing the differentiation of stem cells [23].  alignment of nanomaterials that defines the effect of the orientation of nanomaterials inside the substance. it is demonstrated that aligned nanofibers are more potential than randomly oriented substrates to grow collagen fibres on it [24].  chemistry of the surface and nanomaterials used on their surface should also be considered as a key characteristic affecting proliferation and differentiation of stem cells [25]. 4 neurotoxicity, stem cells, and metals stem cells in the brain are involved in many brain functions such as memory, learning, mood, and olfaction [26]. the process of neurogenesis and neuronal development in adults is completed in an environment in the central nervous system (cns). neural stem cells are a type of somatic cells that have the ability to regenerate itself for long periods of time and generate various distinct neural lineages. cns produces neural stem cells in the brain and can encounter extensive damage when exposed to heavy metals. this exposure causes cellular stress regulating autophagy [27]. in metal on metal prosthesis toxicity occurs after few years [28]. the stable part of the prosthesis is mainly made of titanium with a slight amount of vanadium, chromium, aluminium, cobalt, molybdenum or nickel; however, the bearing surface can be made of polyethylene, ceramic, stainless steel or cobalt/chromium combinations [29]. the metal-on-metal (mom) or ceramic-on-metal (com) prosthesis is more durable compared to the polyethylene-onmetal (pom) or polyethylene-on-ceramic prosthesis since the polyethylene cup causes wear in the prosthesis [30]. the mom prosthesis contains chromium/cobalt bearings that can wear and lead to in vitro cytotoxicity [31-32]. the size, shape, and concentration of the wear particles contribute to the damage it causes [33]. in a case of wellfunctioning prosthesis, the concentration of cobalt chromium increases in the hole blood and serum in the first year of implantation of the prosthesis and decreases in the following years [34]. metal ions in the prosthesis can also, contribute to its failure and can be a threat to local tissues [35]. toxicity of metal implants and their interactions with stem cells: a review 5 based on research done on patients neurotoxicity occurs in three ways in patients with prosthesis peripheral neuropathy, sensorineural hearing-loss and visual impairment which are all involved in cobalt intoxication [36]. table 2 summarizes these points and provides examples of such case. 4.1 ferrous metals 1. stainless steel stainless steel is an iron-based alloy that contains 11-30 wt% of chromium and some percentage of nickel. there are four types of stainless steel alloys: martensitic, austenitic, ferritic, and duplex (austenitic and ferritic). however, only austenitic stainless steel is used as implants due to its high corrosion resistance property [37]. stainless-steel implants have suitable mechanical properties, easy production, and low cost [38]. its corrosion resistance property is mainly due to the passivity layer built on top of stainless steel made of chromium oxide. although the passivity layer is strong it does not make the alloy completely corrosion resistant especially in contact with body fluids [8]. mainly pitting corrosion occurs causing metal ions to be released in the body resulting in various allergies [38]; however, crevice, fatigue, and stress corrosion cracking have also been reported (figure 4) [39]. researchers believe that one of the best ways to enhance the metal implants is to introduce nano structuring with various processing techniques. for instance, severe plastic deformation (spd) is the process in which high considerable amount of strain is subjected to a bulk material to produce an ultra-grained metal [41-43]. nanostructure stainless steels have unique mechanical properties due to their small grain size and high-volume boundaries. research indicates that nano-structuring stainless steel results in uniform grain size and distribution [44]. nanostructured stainless steel increases the thickness and density of the passivity layer resulting in better biocompatibility and reducing corrosion [38]. observations revealed that size, depth, and the number of pitting corrosions decreased in the nanostructured stainless steel compared to the conventional stainless steel implant [44]. 2. iron iron oxide nanoparticles are used in mri as a tracking agent for stem cells. the nature of these nanoparticles is to accumulate in a specific region which leads to localized concentrations and causing toxicity with high cytotoxic levels (100 mg/ ml). cytotoxicity depends on the oxidation state of iron, coating and, interactions between particles and proteins. iron (fe) ions are a cofactor for metalloproteins (e.g. heme) and are usually used in oxidation-reduction reaction [45,46]. one of the potential materials for temporary implants in the body is iron-based alloys. fe is predominantly bound in insoluble degradation products whereas a considerable amount of manganese (mn) exists in the solution. mn is a particle which eliminates cytocompatibility of alloys involved in the implant. biodegradable fe-alloy is being used in different medical implants such as cardiovascular stents or osteosynthesis applications. iron acts as a perfect material for degradable stents with no early restenosis caused by thrombosis, inflammation or local toxicity. comparing to stainless steel 316l and cobalt-chromium alloy, iron-based stents remain intact for a longer time inside the veins while a faster degradation rate was expected. furthermore, by adjusting the mn content in solution the degradation rate of iron-based stents would be adjusted as desired [47,46]. in a research using mouse fibroblast 2t3, l929, primary cells from the human umbilical vein endothelial cells, and mouse bone marrow stem cells the cytotoxicity of pure iron and iron-based alloys was investigated. by studying the eluates of twip (fe 21 mn-0.7 c) and twip-1pd (fe-21 mn 0.7c -1pd) on metabolic activity and viability of human umbilical vein endothelial cells (huvecs), it can be obtained that an increase in eluate concentration causes a decrease in both viability and metabolic activity, while an increase in the eluate concentration causes a decrease in these trends. simulated body fluid (spf) is a factor that causes a slight decrease in this trend as well. endothelial cell growth medium (ecgm) as a control factor can enhance the loss of viability and metabolic activity due to increase in volume which is shown in figure 5[45,48]. adding fe2+ slightly reduce the viability a metabolic activity and concentration more than 2 mmol/l causes a significant decrease. adding fe3+ and mn2+ induce an immediate decline in the trend of viability and metabolic activity, while concentration of more than 0.5 mmol/l has a conflicting effect on cells. mn2+ has the least tolerance with the steepest trend among obtained the results. iron is an element in the human body that is kept nontoxic and soluble while bound to transferrin exclusively. this important element that is used for biomedical devices through aerobic conditions known as “reactive oxygen intermediates” (rois) will convert the free fe ions to harmful radicals such as hydroxyl radicals (ho) generated from superoxide (o2 −) and hydroxide peroxide (h2o2). this reaction also can occur accidentally within incomplete mitochondrial reduction-oxidation or intentionally through activated phagocytic cells. during this reaction, electrons are transferred between fe2+ and fe3+. the acidic chloride salts dissolved with fe lowers the ph values of the resulting solution as 3.2 for fecl2 and 1.7 for fecl3. this very low ph leads to immediate sedimentation of insoluble products. neurodegeneration and oxidative stress are the results from an accumulation of iron due to dyshomeostasis while oxidative stress results in an increased rate of autophagy. iron ions released from metal implants increase the concentration of iron in the blood causing toxicity which it usually damages the liver and heart causing coma, shock, liver failure, organ damage, and if not dealt with in some cases death. mirzajavadkhan, rafieian, and hassan (2020): international journal of engineering materials and manufacture, 5(1), 2-11 6 figure 4: a) corrosion scale on a charnley stainless steel stem, and (b) pitting and corrosion of a muller stainless steel stem after implant removal [40]. figure 6: the sources of carbon nanoparticles and the cells that they affect [49] 4.2 non-ferrous metals 1. carbon carbon nanotubes and nano diamonds are known as carbon-based nanomaterials with a variety of medical applications followed by the cellular toxicity on human mesenchymal stem cells (mscs) [49]. the studies are evaluating the toxic effects of engineered nanomaterials on health and environments and developing safe nanomaterials in commercial products [51]. nanoparticles such as carbons released from combustion, automobiles and industrial pollution have an impact on human mscs in vitro model effect on adipocytes, neurons, osteoblasts, chondrocytes, melanocytes, etc (figure 6). carbon nanotubes are hollow tubes containing carbon having high strength, flexibility, electrical and thermal conductivity. they are used in scaffold due to surface characteristic and morphology resulting in effective cell attachment, differentiation, and proliferation [50]. carbon nanotubes have a fibrous-like shape with the similar toxic properties to asbestosis causing lung inflammation and fibrosis [52]. therefore, the health organizations have strict measures of time exposure while being operated. carbon nanotubes are ensured about their biocompatibility in contact with mscs and neural stem cell (nsc) during tissue healing. analysing the cell cycle using flow cytometry shows the effect of carbon nanoparticles on cell cycle progression which is human mscs were arrested by cnp causing morphological and functional changes [49]. the cytotoxicity of carbon nanoparticles is impacted by functionalization that alters the hydrophobicity of the surface and prevents direct contact between cells and carbon nanotubes [53]. still, the long-term toxicity of scaffolds into human body need to be studied. diamonds in nano-size have near-infrared photoluminescence and magnetic properties. they have lower cytotoxicity compared to carbon nanotubes and are well-tolerance in different cell environments. nano diamonds do not cause oxidative stress, however their low cytotoxicity they change the cell morphology [50]. 2. titanium titanium alloys are favoured by most surgeons and clinicians because of its low density compared to other biomaterials (60% density of stainless steel and nearly 50% density of cobalt) [8], high corrosion resistance due to strong passive layer of tio2 which has the ability to reconstruct itself instantly even if the passivity layer is damaged and a better biocompatibility compared to other implants without mutagenicity [54-55]. usually when implants are inserted in the body, the body generates a capsule marking the implant as a foreign object in the body and causing loosening of the prosthesis; however, titanium implants are the only systems that do not react with any surrounding tissue and completely binned with the bone without making any capsule [56] making them useful in the orthopaedic industry. titanium implants are generally used in long-term devices such as hip replacements due to their bonebonding ability [8]. although its advantages the challenge to develop a satisfactory titanium implant with high wear resistance and excellent bending strength still remains [8]. toxicity of metal implants and their interactions with stem cells: a review 7 3. aluminium aluminium in a biological environment has neurological malfunctions such as memory loss. parkinson’s disease and alzheimer’s disease are mainly due to aluminium accumulation in the brain [57]. most aluminium toxicities cause neurological and non-neurological damages [58] such as brain damage, neurotoxicity, digestive disorders, contact dermatitis, breast cancer, anaemia, osteomalacia and encephalopathy [59]. aluminium particles act similar to fe metals while binding to transferrin in the blood and causing toxicity. they act as inhibitors in cell proliferation during progression and expression of regulating cells associated with cell cycle processes and apoptosis [60]. in a research, the cytotoxic effect of aluminium particles was evaluated using human mscs in contact with al2o3 nanoparticles for different times including 48 and 72 hours. the measurement of cell viability of human mscs is a factor that shows the cytotoxicity of al nanoparticles. figure 7 compares the time and dose-dependent manner of al2o3, concluding that in a low concentration of al2o3-nps slight reduction in cell viability is illustrated while in higher concentrations and time of al2o3-nps, cell viability reaches up to 80% of cell death. therefore, it can be concluded that aluminiumbased nanoparticles have a vital effect on human mscs including viability and proliferation [61]. 4. tantalum tantalum-based implants have bone bonding ability, absorbing feature due to high workability and fracture stiffness [62]. the amount of toxicity and biocompatibility of a metal determines how the tissue responds to the implant [63]. an ideal implant has proper mechanical properties, high fatigue and corrosion resistance, proper density and a young’s modulus relatively close to the bone’s young’s modulus to reduce stress accumulations in the prosthesis. ta is a hard material with the features of ductility, high chemical resistivity and proper apposition to bones [64]. the modulus of elasticity is 186 gpa with a density of 16.6 g/cm^3 which makes it a useful metal in orthopedic applications [65]. tantalum metal can naturally form an oxide layer on the implanted tool in the body and facilitate bone growth. ta is corrosion resistance due to the stable protective oxide layer of ta2o5 on the surface. however, any defects in the oxide layer in the surface causes the release of carcinogenic ni2+ ions in the body [66]. comparing to titanium, tantalum-based implants possess higher biocompatibility in bulk form and powder form. according to the research done on animal models, ignoring the position and form of an implant and the tissue type, tantalum demonstrate no inflammatory response. porous tantalum-based implants have been recently developed for total implants in arthroplasty. figure 8 shows a total shoulder implant made of porous tantalum-based material and the structure of the implant ease the possibility of osseointegration. however, the porous structure causes a significant decrease in elastic modulus and the weight of the implant [67]. 5. zinc zinc and zinc-based alloys possess biodegradable properties between the elements used in biomedical devices [69]. the by-product of zinc corrosion (zn 2+ ) in physiological systems controls basic cellular processes. despite the harmful effects of zn 2+ on smooth muscle cells causing restenosis in arteries, it causes stimulation on osteogenesis of bones. zinc in a pure state has a low strength (uts ~30 mpa) with plasticity (e < 0.25%) that are not enough for most medical device applications. developing high strength and ductility zinc with sufficient hardness, while retaining its biocompatibility, is one of the main goals of metallurgical engineering [70]. although it’s poor strength and plasticity zinc provides few benefits as a biomaterial. zinc is a crucial trace element in biological systems and is a necessary metal for fundamental functions of the body such as cell growth and protein metabolism; therefore, degradation of the implant releasing zn 2+ will consolidate into the normal metabolic activity of the patient without having toxic side effects [71]. zinc also possesses high chemical activity with an electrode potential of -0.762 v. thus, performing a steadier rate of degradation in relation to the passive layer of corrosion formed on the surface of the implant [7073]. comparing to other degradable metals, due to its low melting point, low chemical reactivity, and moderate machinability zinc is much easier to caste and process for biomedical implants. the melting point of zinc is such that it can perform easily in the air [69,70]. figure 7: treating human mscs at various doses for 48 and 72 h and studying the cell viability [61] figure 8: the total shoulder implant with the porous tantalum-based material [68] mirzajavadkhan, rafieian, and hassan (2020): international journal of engineering materials and manufacture, 5(1), 2-11 8 table 3: effects of the elements released from co-cr prosthesis overtime element released impact cobalt neurological effects (tinnitus, vision-loss, vertigo), endocrine, haematological, cardiological, contact dermatitis, headaches, memory loss, fatigue, cramps. hypersensitivity to cobalt occurs more frequently in patients with pre-implant osteolysis showing a delayed hypersensitivity reaction [1,75] chromium more genotoxic compared to cobalt [76]. decreases fertility in male and female individuals by reducing sperm production and ova quality [77] molybdenum low levels of molybdenum can cause irritation in eyes and skin. high amounts ingested can cause diarrhea, infertility, damage in liver, kidney, and lungs [77] 4.3 superalloy/ alloy 1. co-cr cocrbased implants are used in dentistry and artificial joints they were first used as implants in the 1930’s. the strength of this alloys can be increased by cold-working. due to cr2o3 passivity layer, it is highly corrosion resistance compared to stainless steel [71]. it is used in applications that require long exposure to hostile body environment without fracture due to high fatigue resistance and high tensile strength [74]. there are serious concerns about elements such as cobalt, chromium, and molybdenum released from the prosthesis over time which directly impacts the dna causing damage, toxicity, and inflammation. the following table summarizes the effects of ions released from a cocr prosthesis in the body over time. 5 conclusions 1. development of stem cells and metal implants has enhanced the field of tissue engineering by studying the neurotoxicity and the side effects of various nanoparticles and trace elements released from implants in the body. it is important to consider that not all alloys can be implanted due to the corrosive reactions between the implant and the hostile body environment. ph values differ in each part of the body causing an implant to be more corrosive in one region compared to another. thus, it is crucial to analyse the environment and characteristics of that region in the body and choose a compatible alloy. 2. stem cells and nanomaterials have a wide variety of applications such as nanomaterial scaffolds which accumulate fresh cells at a bone failure site and combines grafting scaffold to increase bone healing. the main concern is biocompatibility and cytotoxicity of the scaffolds and the body which might jeopardize the health of an individual. in order to design new substrates for stem cell-based therapies, the interaction of nanomaterial scaffold and stem cells should be studied on a molecular and cellular level. 3. interactive interaction of bone and stem cells shows the effectiveness of stem cells in the maturation of osteoblasts that leads to the formation of new bones. in tissue engineering, this behaviour is enhance using scaffolds to support mesenchymal stem cells. various characteristics of scaffolds such as surface roughness, size, and alignment of nanomaterials that the scaffolds are made of controls the interaction of stem cells and bone. 5. physical and chemical properties, application, biocompatibility with stem cells and more importantly the side effects and toxicity of biomaterials are the characteristics considered to choosing a suitable prosthesis. in the case of pitting corrosion of austenitic stainless steel which is an iron-based alloy, the release of metal ions cause various allergies and toxicities in the body. iron released in the blood leads to serious liver and heart damage that could potentially cause death. non-ferrous metal implants such as carbon could be used for tissue healing. this metal is biocompatible in contact with msc and nsc; however, the long-term toxicity of carbon in contact with stem cells should be studied further. aluminium nanoparticles could cause serious neurological malfunctions. for example, the accumulation of aluminium in the brain leads to parkinson’s and alzheimer's disease. likewise, the existence of this non-ferrous metal increases the viability and proliferation of human mesenchymal stem cells. the absorbing feature of tantalum and the non-inflammatory response of this nonferrous metal is impressive, though it can lead to the release of carcinogenic ni2+ ions to the body. using zinc in medical devices shows no side effects but has very low strength. superalloys are the main biomaterials for prosthesis with high fatigue resistance and tensile strength. peripheral neuropathy, sensorineural hearingloss, and visual impairment are the different possible neurotoxicity that occur among patients with cocr prosthesis which are all due to cobalt intoxication. 6. titanium implants are considered long-lasting and most favoured due to its light weight and its ability to repeat loads. titanium has a low young’s modulus compared to the conventional stainless steel, causing it to reduce the amount of stress on the bone. unlike other metals that form a capsule around the newly placed implant claiming it as a foreign object, this implant is the only implant implants that directly bind to bone without forming a capsule around it and decrease the risk of corrosion and implant loosening. toxicity of metal implants and their interactions with stem cells: a review 9 references 1. gotman i. characteristics of metals used in implants. j. endourol. 1997; 11(6): 383-389. 2. park j, lakes rs. biomaterials: an introduction: ssbm; 2007. 3. zardiackas ld, kraay mj, freese hl, editors. titanium, niobium, zirconium, and tantalum for medical and surgical applications. astm, 2006. 4. arnould c, denayer j, planckaert m, delhalle j, mekhalif z. bilayers coating on titanium surface: the impact on the hydroxyapatite initiation. j. colloid interface sci. 2010; 341(1): 75-82. 5. arnould c, volcke c, lamarque c, thiry pa, delhalle j, mekhalif z. titanium modified with layer-by-layer sol– gel tantalum oxide and an organodiphosphonic acid: a coating for hydroxyapatite growth. j. colloid interface sci. 2009; 336(2): 497-503. 6. geetha m, singh ak, asokamani r, gogia ak. ti based biomaterials, the ultimate choice for orthopaedic implants –a review. prog. mater sci. 2009; 54(3): 397-425. 7. heimann rb. structure, properties, and biomedical performance of osteoconductive bioceramic coatings. surf.coat. technol. 2013; 233: 27-38. 8. q. chen and g. a. thouas, "metallic implant biomaterials," materials science & engineering r, 87, 1-57, 2015. 9. h.j.r.m. long, biomaterials 19 (1998) 1621–1639. 10. s. martino et al, "stem cell-biomaterial interactions for regenerative medicine," biotechnology advances, vol. 30, (1), pp. 338-351, 2012. 11. p. kerativitayanan, j. k. carrow and a. k. gaharwar, "nanomaterials for engineering stem cell responses," advanced healthcare materials, vol. 4, (11), pp. 1600-1627, 2015 12. ma ms, kannan v, de vries ae et al. characterization and comparison of osteoblasts derived from mouse embryonic stem cells and induced pluripotent stem cells. j bone miner metab 2017; 35: 21-30 13. kang y, georgiou ai, macfarlane rj et al. fibronectin stimulates the osteogenic differentiation of murine embryonic stem cells. j tissue eng regen med 2015; 11: 1929–1940. 14. yu y, al-mansoori l, opas m. optimized osteogenic differentiation protocol from r1 mouse embryonic stem cells in vitro. differentiation 2015; 89:1 –10. 15. tourinho ps, van gestel ca, lofts s, svendsen c, soares am, loureiro s. metal-based nanoparticles in soil: fate, behavior, and effects on soil invertebrates. environ toxicol chem. 2012; 31(8):1679–1692. [pubmed: 22573562] 16. r. ravichandran, s. liao, c. c. ng, c. k. chan, m. raghunath, s. ramakrishna, world j. stem cells 2009, 1, 55. 17. chengde gao et al, "bone biomaterials and interactions with stem cells," 5, (4), 253-285, 2017. 18. jensen j, kraft dce, lysdahl h et al. functionalization of polycaprolactone scaffolds with hyaluronic acid and β-tcp facilitates migration and osteogenic differentiation of human dental pulp stem cells in vitro. tissue eng part a 2014; 21: 729–739. 19. zhukova y, hiepen c, knaus p et al. the role of titanium surface nanostructuring on preosteoblast morphology, adhesion, and migration. adv healthcare mater 2017, 1601244. 20. aiyelabegan ht, sadroddiny e. fundamentals of protein and cell interactions in biomaterials. biomed pharmacother 2017; 88: 956–970. 21. martins a, pinho ed, correlo vm, faria s, marques ap, reis rl, et al. biodegradable nanofibers-reinforced microfibrous composite scaffolds for bone tissue engineering. tissue eng part a 2010; 16:3599–609. 22. w. chen, l. g. villa-diaz, y. sun, shinuo weng, j. k. kim, r. h. w. lam, l. han, r. fan, p. h. krebsbach, j. fu, acs nano 2012, 6, 4094. 23. lei b, chen x, wang y, zhao n, du c, fang l. surface nanoscale patterning of bioactive glass to support cellular growth and differentiation. j biomed mater res a 2010; 94:1091–9. 24. wangg, zhengl,zhaoh, miaoj, sunc, liuh, etal.construction of a fluorescent nanostructured chitosanhydroxyapatite scaffold by nanocrystallon induced biomimetic mineralization and its cell biocompatibility. acs appl mater interfaces 2011a;3: 1692–701. 25. chen h, fan x, xia j, chen p, zhou x, huang j, et al. electrospun chitosan-graft-poly (varepsiloncaprolactone)/poly (varepsilon-caprolactone) nanofibrous scaffolds for retinal tissue engineering. int j nanomedicine 2011; 6:453–61. 26. zhao c, deng w, gage fh: mechanisms and functional implications of adult neurogenesis. cell 2008, 132:645660. 27. chatterjee s, sarkar s, bhattacharya s (2014) toxic metals and autophagy. chem res toxicol 27:1887–1900 28. s. m. bradberry, j. m. wilkinson and r. e. ferner, "systemic toxicity related to metal hip prostheses," clinical toxicology, vol. 52, (8), pp. 837-847, 2014. 29. labek g, thaler m, janda w, agreiter m, sto ̈ckl b. revision rates after total joint replacement: cumulative results from worldwide joint register datasets. j bone joint surg br 2011; 93-b: 293–297. 30. rising jp, reynolds is, sedrakyan a. delays and difficulties in assessing metal-on-metal hip implants. n engl j med 2012; 367 31. madathil bk, lin q, hew c-l, mohanty m. hypoxia-like effect of cobalt chromium alloy micro particles on fibroblasts in vitro. j orthop res 2010; 28:1360–1367. mirzajavadkhan, rafieian, and hassan (2020): international journal of engineering materials and manufacture, 5(1), 2-11 10 32. v. sansone, d. pagani and m. melato, "the effects on bone cells of metal ions released from orthopaedic implants. a review," clinical cases in mineral and bone metabolism: the official journal of the italian society of osteoporosis, mineral metabolism, and skeletal diseases, vol. 10, (1), pp. 34, 2013. 33. polyzois i, nikolopoulos d, michos i, patsouris e, theocharis s. local and systemic toxicity of nanoscale debris particles in total hip arthroplasty. j appl toxicol 2012; 32:255–269. 34. jantzen c, jorgensen hl, duus br, sporring sl, lauritzen jb. chromium and cobalt ion concentrations in blood and serum following various types of metal-on-metal hip arthroplasties: a literature overview. acta orthop 2013; 84:229–236. 35. andrews re, shah km, wilkinson jm, gartland a. effects of cobalt and chromium ions at clinically equivalent concentrations after metal-on-metal hip replacement on human osteoblasts and osteoclasts: implications for skeletal health. bone 2011; 49:717–723. 36. s. m. bradberry, j. m. wilkinson and r. e. ferner, "systemic toxicity related to metal hip prostheses," clinical toxicology, vol. 52, (8), 837-847, 2014. 37. mettalic materials, j.r. davies (ed.), handbook of materials for medical devices, asm international, materials park, ohio, 2003, 21–50. 38. brown rn, sexton be, chu t-mg, katona tr, stewart kt, kyung h-m, liu ss. comparison of stainless steel and titanium alloy orthodontic miniscrew implants: a mechanical and histologic analysis. 2014; 145(4): 496-504. 39. hajizadeh k, maleki ghaleh h, arabi a, behnamian y, aghaie e, farrokhi a, hosseini mg, fathi mh. corrosion and biological behavior of nanostructured 316l stainless steel processed by severe plastic deformation. surf. interface anal. 2015; 47(10): 978-85. 40. j. walczak, f. shahgaldi, f. heatley, biomaterials 19 (1998) 229–237. 41. azushima a, kopp r, korhonen a, yang d, micari f, lahoti g, groche p, yanagimoto j, tsuji n, rosochowski a, yanagida a. severe plastic deformation (spd) processes for metals. cirp. ann-manuf. techn. 2008; 57(2): 716-735. 42. nie f, zheng y, wei s, hu c, yang g. in vitro corrosion, cytotoxicity and hemocompatibility of bulk nanocrystalline pure iron. biomed. mater. 2010; 5(6): 065015. 43. orlov d, ralston k, birbilis n, estrin y. enhanced corrosion resistance of mg alloy zk60 after processing by integrated extrusion and equal channel angular pressing. acta mater. 2011; 59(15): 6176-6186. 44. p. m. hashemi, e. borhani and m. s. nourbakhsh, "a review on nanostructured stainless steel implants for biomedical application," nanomedicine journal, vol. 3, (4), 202-216, 2016. 45. m. schinhammer et al, "on the cytocompatibility of biodegradable fe-based alloys,"materials science & engineering. c, materials for biological applications, vol. 33, (2), 782-789, 2013. 46. y. yao et al, "cobalt and nickel stabilize stem cell transcription factor oct4 through modulating its sumoylation and ubiquitination," plos one, vol. 9, (1), 86620, 2014. 47. zhang zn, chung sk, xu z, xu y (2013) oct4 maintains the pluripotency of human embryonic stem cells by inactivating p53 through sirt1-mediated deacetylation. stem cells. 48. botquin v, hess h, fuhrmann g, anastassiadis c, gross mk, et al. (1998) new pou dimer configuration mediates antagonistic control of an osteopontin preimplantation enhancer by oct-4 and sox-2. genes dev 12: 2073–2090. 49. periasamy, v. s., athinarayanan, j., alfawaz, m. a., & alshatwi, a. a. (2016). carbon nanoparticle induced cytotoxicity in human mesenchymal stem cells through upregulation of tnf3, nfkbia and bcl2l1 genes. chemosphere, 144(complete), 275-284. doi:10.1016/j.chemosphere. 2015.08.018 50. wei f, scholer hr, atchison ml (2007) sumoylation of oct4 enhances its stability, dna binding, and transactivation. j biol chem 282: 21551–21560. 51. aitken, r.j., hankin, s.m., ross, b., tran, c.l., stone, v., fernandes, t.f., donaldson, k., et al., 2009. emergnano: a review of completed and near completed environment, health and safety research on nanomaterials and nanotechnology defra project cb0409 institute of occupational medicine report. tm/09/01 52. pacurari m, castranova v, vallyathan v. singleand multi-wall carbon nanotubes versus asbestos: are the carbon nanotubes a new health risk to humans? j toxicol environ health a. 2010; 73(5) 53. a. m. schrand, j. johnson, l. dai, saber m. hussain, j. j. schlager, l. zhu, y. hong, e. o. sawa, in safety of nanoparticles, springer, new york 2009. 54. schliephake h, scharnweber d. chemical and biological functionalization of titanium for dental implants. j. mater. chem. 2008; 18(21): 2404-24014. 55. t. kodama, kokubyo gakkai zasshi, j. stomatol. soc. jpn. 56 (1989) 263–288. 56. p.c. ferreira, k.d.a. piai, a.m. magosso takayanagui, s.i. segura-munoz, rev. lat. am. enfermagem 16 (2008) 151–157. 57. savory j, ghribi o. can studies of aluminium toxicity in vivo and in vitro provide relevant information on the pathogenesis and aetiology of alzheimer’s disease? j alzheimer’s dis 2007; 11:429-30; discussion 31-2. 58. s.v. verstraeten, l. aimo, p.i. oteiza, arch. toxicol. 82 (2008) 789–802. toxicity of metal implants and their interactions with stem cells: a review 11 59. nam, s. m., kim, j. w., yoo, d. y., kim, w., jung, h. y., choi, j. h., … yoon, y. s. (2016). effects of aluminum on the reduction of neural stem cells, proliferating cells, and differentiating neuroblasts in the dentate gyrus of d-galactose-treated mice via increasing oxidative stress. journal of veterinary science, 17(2), 127–136. 60. huang, d. m., hsiao, j. k., chen, y. c., chien, l. y., yao, m., chen, y. k., yao, m., chen, y. k., ko, b. s., hsu, s. c., tai, l. a., cheng, h. y., wang, s. w., yang, c. s., and chen, y. c. (2009) biomaterials 30, 3645–3651. 61. v. s. periasamy, j. athinarayanan and a. a. alshatwi, "aluminium oxide nanoparticles alter cell cycle progression through ccnd1 and egr1 gene expression in human mesenchymal stem cells," biotechnology and applied biochemistry, vol. 63, (3), pp. 320-327, 2016. 62. balla vk, bodhak s, bose s, bandyopadhyay a. porous tantalum structures for bone implants: fabrication, mechanical and in vitro biological properties. acta. biomater. 2010; 6(8): 3349-3359. 63. chaturvedi t. allergy related to dental implant and its clinical significance. clin cosmet investig dent. 2013; 5: 57-61. 64. helsen, j.a., missirlis, y.: biomaterials a tantalus experience. springer, 2010 65. tao, l., wen, j., et al.: enhanced osteo-integration on tantalum implanted polyetheretherketone surface with bone-like lastic modulus. biomaterials 51 (2015), 173-183. 66. mcnamara, k., kolaj-robin, o., et al.: surface chemistry and cytotoxicity of reactively sputtered tantalum oxide films on niti plates. in: thin solid films 589 (2015), p. 1-7. 67. liu, y., bao, c., et al.: the physicochemical/biological properties of porous tantalum and the potential surface modification techniques to improve its clinical application in dental implantology. in: materials science and engineering c 49 (2015), 323-329. 68. bobyn, j.d., toh, k.k., et al.: tissue response to porous tantalum acetabular cups: a canine model. in: journal of arthroplasty 14 (1999) 347-354. 69. g. katarivas levy, j. goldman and e. aghion, "the prospects of zinc as a structural material for biodegradable implants—a review paper," metals, vol. 7, (10), pp. 402, 2017. 70. g. katarivas levy, j. goldman and e. aghion, "the prospects of zinc as a structural material for biodegradable implants—a review paper," metals, 7, (10), 402, 2017. 71. liu, x.; sun, j.; qiu, k.; yang, y.; pu, z.; li, l.; zheng, y. effects of alloying elements (ca and sr) on microstructure, mechanical property and in vitro corrosion behavior of biodegradable zn–1.5mg alloy. j. alloys compd. 2016, 664, 444–452. 72. s. pramanik, a.k. agarwal, k.n. rai, trends biomater. artif. organs 19 (2005) 15–26. 73. s. shaham et al, "fast channel estimation and beam tracking for millimeter wave vehicular communications," 2018. 74. park j, lakes rs. biomaterials: an introduction: ssbm; 2007. 75. v. sansone, d. pagani and m. melato, "the effects on bone cells of metal ions released from orthopaedic implants. a review," clinical cases in mineral and bone metabolism: the official journal of the italian society of osteoporosis, mineral metabolism, and skeletal diseases, vol. 10, (1), 34, 2013. 76. papageorgiou i, yin z, ladon d, et al. genotoxic effects of particles of surgical cobalt chrome alloy on human cells of different age in vitro. mutat res 2007; 619:45-58. 77. k. liber, l.e. doig, s.l. white-sobey, ecotoxicol. environ. saf. 74 (2011) 1171–1179. 78. c. delaunay, i. petit, i.d. learmonth, p. oger, p.a. vendittoli, orthop. traumatol. surg. res. 96 (2010) 894– 904. 79. s. shaham et al, "privacy preservation in location-based services: a novel metric and attack model," 2018. 80. j.j. ramsden, d.m. allen, d.j. stephenson, j.r. alcock, g.n. peggs, g. fuller, g. goch, cirp ann. manuf. technol. 56 (2007) 687–711. international journal of engineering materials and manufacture (2021) 6(4) 340-356 https://doi.org/10.26776/ijemm.06.04.2021.11 mustapha ndagi 1 , ajiboye tajudeen kolawole 1 , fabiyi mustapha olawale 2 and abdulkareem sulaiman 1 1 department of mechanical engineering, faculty of engineering & technology university of ilorin, p.m.b. 1515, ilorin, nigeria. 2 department of mechanical engineering, faculty of engineering university of ilorin, p.m.b 1515, ilorin, nigeria e-mail: engrtkajiboye@yahoo.com reference: ndagi et al. (2021). investigation of the thermo-physical and mechanical properties of coir and sugarcane bagasse for low temperature insulation. international journal of engineering materials and manufacture, 6(4), 340-356. investigation of the thermo-physical and mechanical properties of coir and sugarcane bagasse for low temperature insulation mustapha ndagi, ajiboye tajudeen kolawole, fabiyi mustapha olawale and abdulkareem sulaiman received: 02 march 2021 accepted: 29 july 2021 published: 01 october 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract this research reports on the suitability of agricultural bi-products as low temperature thermal insulating materials to replace synthetic insulating materials like polyurethane used in food warmers and ice coolers. coir and sugarcane bagasse chosen for this research was based on literature review and local availability of materials. coir was obtained from badagry, lagos state and sugarcane bagasse obtained from batati, niger state, the materials were washed, sun dried for three days and cut into smaller pieces before being blended into smaller particles using an electric blender. the blended materials (coir and bagasse) were sieved into two different sieve size of 0.5 mm and 1.0 mm respectively. the particles sizes were then combined into blend ratios of 50/50, 60/40, and 70/30 using gum arabic as binder. thermal conductivity test showed that 1.0 mm particle size coir mixed with sugarcane bagasse has the lowest thermal conductivity of 0.01467 w/mk whilst that of 0.5 mm particle size has thermal conductivity of 0.01472 w/mk this is lower compared to the measured thermal conductivity of the polyurethane control sample of 0.01832 w/mk. sample f (1.0 mm particle size,70% coir and 30% bagasse) with a thermal diffusivity of 5.15𝑥10−5 m²/s, water absorption capacity of 410 %, uts of 0.219 mpa, compressive strength of 0.583 mpa, specific heat capacity of 1141.3 j/kgk and thermal resistivity of 68.16 w/m/k is most suitable replacement for polyurethane as low temperature thermal insulator. this is corroborated by the performance evaluation test with carried out between polyurethane lined food warmer and bio-composite lined food warmer. the two test samples have close ice melt rate values and the polyurethane slightly edge the bio-composite insulating material by 1.2 % in efficiency. the edge in efficiency can be accepted as all materials used in the development of the bio-composite insulating material are completely bio-degradable and environmentally friendly. keywords: bio-degradable, composite, thermal insulation, thermal diffusivity, ultimate tensile strength, water absorption capacity. 1 introduction insulation plays a vital role in the general sustainability of life on earth, it has been in existence since the stone ages when early men wore dead animal skin to protect himself from the elements. however, as they advance, they used not only materials that were found in nature, but discovered others which were suitable for insulation. processed organic materials produced the first insulated panels in the 19th century: meanwhile an increasing range of artificial materials were developed (rock wool, fiberglass, foam glass, hollow bricks, and expanded perlite). although plastic production was well-known in the 19th century, the first plastic foam was not produced until 1941 [1]. there are varieties of application ranges of insulation including: sound or acoustic insulation which prevents the permeability of sound and absorb it or try to disperse it. sounds transmit through the air so we can distinguish the different types of voices as well as noise. sounds also travel as a waves through solid objects of the building specially the concrete bodies, so it should be isolated to prevent the transmission of sound from outside to the inside or from one place to another. insulation from radiation energy is also important, rays like ultraviolet rays, gamma rays xrays et c. can be harmful to human body if exposed to for an extended period of time. paper, lead and aluminium in varying thicknesses are some of the insulating materials used to shield the body from harmful radiation energy. investigation of the thermo-physical and mechanical properties of coir and sugarcane bagasse for low temperature insulation 341 some materials do not allow the flow of electric current, such materials are called "electrical insulators" such as: wood, plastic and ceramic. insulations that conserve energy by reducing heat loss or gain, control surface temperatures for personal protection and comfort, facilitate temperature control process and prevent vapour flow and water condensation on cold surfaces are known as thermal insulators.” thermal insulators are those materials that prevent or reduce various forms of heat transfer (conduction, convection and radiation) [2]. insulator resists the heat transfer from outside to inside or in opposite direction whether the environment temperature is high or low. there are many advantages of thermal insulation that isolates the insulated body or object from the heat and reduces the energy consumption as well as the costs of air-conditioning operation or refrigeration. the temperature range, within which the term "thermal insulation" applies, is from -75°c to 815°c. all applications below -75 °c are termed "cryogenic", and those above 815 °c are termed "refractory” [6]. low temperature thermal insulation ranges from -75 °c to 15 °c. applications include; refrigeration of brine, glycol and cold or chilled water. medium temperature thermal insulation ranges from 16 °c to 315 °c. applications include hot water and steam condensate. high temperature thermal insulation ranges from 316 °c to 815 °c. applications include; turbines, stacks, exhausts, incinerators, boilers. [3] thermal insulators used now-a-days are made from synthetic materials such as fiberglass, mineral wool, polyurethane foam, polystyrene, glass wool, rock wool, etc.; these insulations are costly and few of them like glass wool and rock wool are carcinogenic in nature. fiberglass is carcinogenic and while installing this insulator one might feel itching, redness of skin and breathing issues. polyurethane foam is highly flammable whose smoke contains carbon monoxide, benzene et c., which is not good for environment as well as humans [4]. there is an urgent need for more environmentally friendly, renewable and biodegradable low temperature thermal insulation, to replace the environmentally hazardous ones used presently, this can be achieved through the use of bio composite materials gotten from natural replenishing sources or agricultural by-products. bio-composites insulating materials are suitable for low temperature thermal applications. they are renewable, cheap, completely or partially recyclable, and biodegradable. plants, such as flax, cotton, hemp, jute, sisal, pineapple, ramie, bamboo, banana, coconut fibre, sugarcane bagasse, kapok, etc., as well as wood, used from time immemorial as a source of lignocellulose fibres, are more and more often applied as the reinforcement of composites. their availability, renewability, low density, and price as well as satisfactory mechanical properties make them an attractive ecological alternative to glass, polystyrene, polyurethane, carbon and man-made fibres used for the application of low temperature thermal insulation. renewable fibrous thermal insulation materials from trees, plant or animals have the ability to regenerate itself, it requires less energy for production and biodegrade easily when disposed as waste hence have low environmental impact [5]. a cheap reliable and abundant supply of biodegradable fibrous materials can be obtained as by-products from many commercial agricultural processing industries [6]. materials such as kapok, coconut and sugarcane fibre, cotton, wheat straw, palm leaves, oil palm fibre and others consist of lignocellulosic fibres which can be used as alternative insulation materials. this research seeks to study the thermal properties of bio composite formed from different combinations of sugarcane bagasse, and coconut coir. 2 literature review researchers have begun to focus attention on natural fibre composites (i.e., bio-composites), which are composed of natural or synthetic resins, reinforced with natural fibres. natural. fibers exhibit many advantageous properties; they are a low-density material yielding relatively lightweight composites with high specific properties. these fibres also are of significant cost advantages and ease of processing along with being a highly renewable resource, in turn reducing the dependency on foreign and domestic synthetic materials. recent advances in the use of natural fibres (e.g. cellulose, jute, hemp, bagasse, straw, switch grass, kenaf, coir and bamboo) in composites have been reviewed by several authors. in (7) authors used kapok, bagasse and coir to form composites of varying mixture rates and their result shows that kapok had the highest thermal conductivity of 0.0220 w/mk with density of 0.73 g/c3, bagasse had thermal conductivity of 0.0074 w/mk and a density of 0.7780.73 g/c3, while coir had a thermal conductivity of 0.0109w/mk and density of 0.626 g/c3.this shows that while kapok had the lowest density it also has the highest thermal conductivity value, bagasse on the other hand had the lowest thermal conductivity but a higher density compared to the coir. the coir had a low thermal conductivity better than the kapok and low density better than the bagasse. after different mixture combinations of three materials their result show that a combination of 50% kapok and 50% bagasse gave a lower thermal conductivity of 0.0106w /mk though at a higher density of 0.843 g/c³. though the mechanical properties such as tensile strength and compressive strength and physical properties such as water absorption capacity of the samples were not determined, there work shows that bio composite of kapok bagasse and coir is suitable for low temperature insulation application. in (8) authors studied the thermal properties of composite of rice husk, corncob and bagasse for building thermal insulation. they prepared samples of varying percentage constituents and determined the thermal conductivity of the samples using p.a hilton thermal conductivity apparatus. their results show that a combination of 60% rice husk, 20% corncob and 20% bagasse gave the lowest thermal conductivity of 0.1961 w/mk and highest thermal resistivity of 5.0094 w/m/k at a density of 656 kg/m³, they also concluded that there was a steady improvement of thermal properties with the addition of sugarcane bagasse but that after 50% addition the ndagi et al. (2021). international journal of engineering materials and manufacture, 6(4), 340-356 342 improvement in the thermal properties dropped significantly. though, in their research work it was clearly stated that resistant to mold growth is one of the key physical properties required for picking replacement insulating materials. however, there were no results shown for the water absorption capacity of the individual samples prepared. in (9) authors worked on thermal properties of bagasse fly ash reinforced epoxy composite. they observed that the incorporation of bagasse fly ash particles results in decrease in the thermal conductivity compared to that of pure epoxy. a maximum decrease of about 44.25 % in thermal conductivity of epoxy is observed with 50%wt of bagasse fly ash in the composite there by improves its thermal insulation capability. they also observed that the thermal expansion is greatly influenced with the addition of bagasse fly ash particles. coefficient of thermal expansion of pure epoxy is 23.23×108 at temperature range of around 45-75 °c and for composite with 50 % fly ash, thermal expansion is 13.21×10-8 /°c. in practice it shows that with increasing the bagasse ash percentage in epoxy reduces the thermal expansion. the specific heat capacity of composite with bagasse fly ash particles exhibited higher specific heat carrying capacity than composite without fly ash. for pure epoxy it is around 1.000 j/g°c and for epoxy with 50% weight fraction bagasse ash composite it is observed as 2.713 j/g°c. higher fly ash content in composite higher will be the heat carrying capacity of the composite. finally, they concluded that the thermal diffusivity of pure epoxy is observed as 3.324 ×10-7 m2/s. thermal diffusivity decreased with addition of fly ash, thus its ability to store thermal energy will be increased with increase in the bagasse ash percentage. in (10) authors developed insulation from coconut husk using suitable binders and implemented it on fixed volume wall then carried out heat loss analysis. their findings showed that; heat loss calculation done on fixed volume room without insulation will consume over 582.18 kg of fuel which is equivalent to the mass of coal needed to produce electricity for this space closed volume. after implement insulation made from coconut husk on fixed volume room approximately 30 to 40% heat loss was reduced which will reduce the energy consumption by up to 20 to 30 %. total co2 emissions for this closed system was 1385.58 kg yearly and after implementing coconut husk insulation on room wall it reduces the yearly co2 emissions. from the experiment, they concluded that using coconut as insulation on residential building is most efficient and economical way for reducing residential electricity consumption and reduction in co2 emissions to the atmosphere. in (11) authors developed and characterized sugarcane bagasse fibre and nano-silica reinforced epoxy hybrid composites. they prepared composite of bagasse and nanosilica particulates of varying weight ratio. the tensile and flexural values for the samples were obtained and found out that; all the sugarcane short fibre reinforced epoxy composites obtained higher flexural modulus compared to sugarcane fibre particulates reinforced epoxy composites. among all the sugarcane short fibre composites, 1wt% of sugarcane short fibre composite exhibits the highest tensile and flexural properties compared to 2.5 wt%, 3.5 wt% and 5 wt%. sugarcane fibre particulates reinforced composites were shown to have better performance when the wt.% of the fibre increase while compared to short fibre reinforced composites. the sugarcane fibre particulates composites fabricated using ultrasonic processor showed improvement in both tensile and flexural properties due to the de agglomeration of the fibre particulates. in (2) author used coconut coir to fabricate an ice cooler which he compared with commercially available rubber lined ice cooler and polystyrene lined ice cooler. by employing a comparative method to determine the effectiveness of the zinc-coated metal sheet ice-cooler with coconut fibre insulation in relation to standard commercially available rubbermaid and polystyrene ice-cooler. he varied the density of the coconut fibre insulation from 50 kg/m3 to 95 kg/m³ for ice-coolers with wall thickness 38 mm, 51 mm, and 64 mm, respectively. for each density the melt rate was measured and compared with the rubbermaid and polystyrene coolers. the laboratory built ice-coolers were approximately the same volume and similar in shape to the commercial ice-coolers. he concluded that; from the melt rate experimental results of the three laboratory built coconut fibre insulated ice coolers the 64 mm thick 95kg/m3 density ice cooler performed the best. the 51 mm and 64mm thick ice coolers performed consistently better than the rubbermaid cooler. the 51 mm and 64 mm thick ice coolers performance were comparable to that of the polystyrene ice cooler. in (12) authors varied percentages of coconut coir to latex binder from 0% to 60% by weight of the overall sample weight, they carried out mechanical test including tensile and compression, moisture absorption test and heat absorption test on all the prepared samples. their conclusion was that; the mechanical test, physical test, and actual heat test showed that 30 % of latex content in coconut fibre composite is the best composition for heat insulator applications. based on heat absorption test, it shows that the specimen can absorb 95% of the heat, which is better compared to other specimens and the synthetic rubber (actual product). the tensile strength of the specimen is almost the same with other specimens, but it is lower compared to synthetic rubber sample. although there were some differences for young modulus properties, but the gap is small. since the heat insulator application did not require high tensile modulus properties, therefore this difference is acceptable. their research shows that natural fibre composite has very good heat insulating properties and suitable for various applications. in (13) authors prepared two sets of composites using un carbonized (ubp) and carbonized (cbp) bagasse particles by varying the bagasse particles from 10 to 50 wt%. the surface morphology and the mechanical properties of the composites were examined they concluded that the uniform distribution of the bagasse particles in the microstructure of the polymer composites is the major factor responsible for the improvement of the mechanical properties. the bagasse particles added to the rldpe polymer improved its rigidity and the hardness values of the composites. the tensile and bending strengths of the composite increased with increasing percentage of the bagasse investigation of the thermo-physical and mechanical properties of coir and sugarcane bagasse for low temperature insulation 343 to a maximum of 20 wt%ubp and 30 wt%cbp. the impact energy and fracture toughness decreases with wt% bagasse particles. the developed composites have the best properties in the ranges of 30 wt.% bagasse particle additions and for optimum service condition, carbonized bagasse particles addition should not exceed 30 wt%. in (14) authors compared the thermal properties of coconut coir, polystyrene and polyurethane compressed at different densities, the thermal conductivities of the samples were determined and their results showed that coconut coir with a density of 95 kg/m³ had a thermal conductivity of 0.03667 w/mk, polystyrene with a density of 95 kg/m³ had a thermal conductivity of 0.02445 w/mk and polyurethane with density of 95 kg/m³ had a thermal conductivity of 0.01939 w/mk. they concluded that polyurethane had the lowest thermal conductivity, the optimized density and thickness of the polyurethane was analysed and the thermal conductivity was found experimentally by lee dick’s apparatus from all the three materials namely coconut fibre, polystyrene and polyurethane. it is found that polyurethane of density 95 kg/m³ and thickness of 64 mm was the best with the least thermal conductivity of 0.01939 w/mk. in (15) authors studied the thermal properties of sugar cane fibre, saw dust, banana fibres, ash, charcoal dust, clay and kaolin. they determined the thermal conductivity, thermal diffusivity and specific heat capacity of the selected materials. their results showed that; the thermal conductivity w/mk values obtained ranged from 0.086 w/mk to 0.107 w/mk for sugarcane fibres, 0.297 w/mk 0.301 w/mk for ash, 0.276 w/mk0.338 w/mk for banana fibres, 0.185 w/mk0.240 w/mk for saw dust, 0.466 w/mk 0.554 w/mk for kaolin, 0.210 w/mk-0.308 w/mk for clay and 0.1840 w/mk 0.219 w/mk for charcoal dust. this clearly shows that sugarcane fibre has the lowest thermal conductivity and highest thermal resistivity coupled with a relatively high thermal diffusivity of 5.05 x〖10〗^ (-7) m^2⁄s and high specific heat capacity of 1,125 j/kgk making it suitable as an ideal material for thermal energy storage systems (tes). in (16) authors studied the thermal properties of different agricultural by-products, their results showed that agricultural by-products prove to be good thermal insulators. all the reviewed agriculture by-products showed impressive thermal insulation properties as their thermal conductivity is very low as that of artificial insulators, which shows great thermal insulation properties. the highest thermal conductivity is shown by rice husk which is 0.077 w/mk and lowest thermal conductivity is shown by sunflower stalk which is 0.0378 w/mk. the remaining products in increasing order of thermal conductivity are palm fibre, hemp, banana fibre, bagasse, coconut fibre. in (17) authors studied utilization of bagasse waste based materials as improvement for thermal insulation of cement brick. they compared the thermal and mechanical properties of banana based bagasse and sugarcane based bagasse using heat flow meter. they treated the waste bagasse using sodium hydroxide (naoh) and characterized it using sem and xrf. they produced two samples with two different dimensions of 50 mm x 50 mm x 50 mm and 215 mm x 102.5 mm x 6 mm for thermal conductivity test. they tested the compressive strength for 7, 14 and 28 days of water curing. their results showed that banana bagasse has lower thermal conductivity compared to sugarcane bagasse used, with compressive strength of 15.6 mpa with thermal conductivity 0.6 w/mk. 3 materials and materials preparation materials used for this research were sugarcane bagasse obtained from batati, niger state and coconut fibre (coir) obtained from badagry, lagos state. the binder chosen was gum arabic manufactured by nike chemicals india. the gum arabic was obtained in a chemical retail store in ilorin. in addition, polyurethane insulation sample was obtained from a cold room in bida niger state to serve as control sample. 3.1 sugarcane bagasse sugar cane bagasse was obtained from a dump site in batati village, niger state, the obtained bagasse (figure 1) was washed with water and sun dried for 3 days. the dried bagasse was blended using an electrical blender after which the bagasse was sieved (figure 2) (using mechanical shaker to obtain 0.5 mm and 1.0 mm sieve sizes. figure 1: sugarcane bagasse washed and dried ndagi et al. (2021). international journal of engineering materials and manufacture, 6(4), 340-356 344 (a) (b) figure 2: bagasse sieved into (a) 0.5 mm and (b) 1.0 mm sieve size figure 3: coir washed and dried 3.2 coir coconut outer shell was obtained from badagry in lagos state. coir was obtained from the left over of the coconut endocarp. the coir (figure 3) was removed from the outer shell using knife and plier. further processing of the coir is same as that of sugarcane bagasse to obtain different size constituents. 3.3 sample mix coir and bagasse were weighed using an electronic weigh balance (hx-t) with 300 g maximum capacity and sensitivity of 0.01 g. 5 g of coir was mixed with 5 g of bagasse, to give a total of 10 g for each sieve size (table 1). 50 % of the total sample weight which equals 5 g of gum arabic was dissolved in 50 g of water and mixed thoroughly before it was poured into various test mould to make three samples each per sieve size. this process was repeated while varying the (coir/bagasse) constituent with ratios 50/50, 60/40 and 70/30 respectively, for 0.5 mm and 1.0 mm sieve sizes making a total of 18 samples per test. the mould was placed on a testometric universal testing machine (fs 50at) (figure 4 a&b) where a static load of 180n was applied for five minutes, after which they were removed and weighed using the electronic weigh balance. samples were cured in an oven at 105 °c for 9 hours, the samples were then weighed again to determine their dry weight [16] 4 experimental tests 4.1 tensile test the tensile strength of the samples was determined in accordance with astm standard d3039 2014 samples were prepared in dumbbell shape (figure 6) with dimensions of 200 mm x 10 mm x 20 mm (figure 7 a). the test was carried out using the 50 kn testometric universal testing machine fs 50 at in metallurgy laboratory, department of mechanical engineering, university of ilorin. mounting of the samples one at a time was carried out based on their respective sieve sizes and test speed of 2 mm/min was applied until samples failed (figure 7 b). the test was repeated for the various sieve size and constituent ratios. the ultimate tensile strength (uts) were recorded for each size constituent and ratios. investigation of the thermo-physical and mechanical properties of coir and sugarcane bagasse for low temperature insulation 345 (a) (b) figure 4: coir sieved into (a) 0.5 mm and (b) 1.0 mm sieve sizes figure 5: samples under load during molding table 1: sample mix sieve size sample coir bagasse 0.5 mm a b c 50% 60% 70% 50% 40% 30% 1.0 mm d e f 50% 60% 70% 50% 40% 30% 4.2 compressive test the compressive test was determined using a mould of 60 mm diameter in accordance with astm standard d3039 2014. 60 mm x 20 mm (figure 8 a) samples were prepared for different size constituents and mix ratio the compressive strength test was carried out using the 50 kn testometric universal testing machine fs 50 at. samples were mounted one at time based on their respective sieve sizes and test speed of 2 mm/min was applied until samples failed (figure 8 b). the test was repeated for the various sieve size and constituent ratios. 4.3 thermal conductivity test thermal conductivity (k) of a material is a measurement of the material’s effectiveness in conducting heat [7]. the inverse of thermal conductivity is thermal resistivity as such a material with low thermal conductivity will have a high thermal resistivity. thermal conductivity test was determined according to astm e 192.11 2015 using the armfiled ndagi et al. (2021). international journal of engineering materials and manufacture, 6(4), 340-356 346 computer compatible linear heat conduction accessory (figure 9) located in landmark university omu aran. samples were prepared with the following dimensions; 35 mm diameter by 5 mm thickness (figure 10) were prepared for the two size sizes and 6 composition ratios respectively. the temperature difference between the hot and cold thermocouples, cross sectional area and temperature difference dt for each composition were recorded this values were used to determine the thermal conductivity in w/mk of each composition. figure 6: schematic diagram of tensile test sample (a) (b) figure 7: (a) prepared tensile samples and (b) sample under test (a) (b) figure 8: (a) prepared compressive test samples and (b) samples under test investigation of the thermo-physical and mechanical properties of coir and sugarcane bagasse for low temperature insulation 347 4.4 heat capacity test the heat capacity of material is the ability of the material to store heat [11]. the thermal conductivity of a material is directly proportional to the heat carrying capacity and density of the material. this implies that as the thermal conductivity increases so does the heat carrying capacity of the material. the specific heat capacity of each composition was calculated from the heat capacity which was determined according to astm e 192.11 2015, using mettler toledo differential, sequential calorimetry (dsc) apparatus (figure 11) located in csmrd laboratory kaduna polytechnic. samples were prepared in batches of 1.8 mg weight (figure 12) for all the 6 composition ratios in accordance with the specification of the machine. samples were tested for a total time frame of 9 minutes and their individual temperature difference recorded. the heat capacity in milli watts (mw) and specific heat capacity in j/kgk were then recorded. figure 9: thermal conductivity apparatus figure 10: thermal conductivity samples figure 11: prepared dsc samples figure 12: dsc apparatus ndagi et al. (2021). international journal of engineering materials and manufacture, 6(4), 340-356 348 4.5 water absorption capacity test the presence of water or humid air in the insulator reduces the thermal insulation value of the material and it may destruct the material rapidly [11]. the moisture is measured by the effect of moisture absorption and permeability. water absorption capacity was carried out in accordance with astm d570-98(2018) 50 mm diameter x 10 mm thick samples (figure 13) were prepared and allowed to completely dry for 24 hours after which they were weighed and completely immersed in water for 24 hours (figure 14). at the end of the 24 hours, samples were removed and a blotting paper used to remove excess water from the surface of the samples before they were weighed again to determine their green weight. the water absorption capacity of individual samples was calculated by subtracting the dry weight from the wet weight and dividing the answer by the dry weight. 𝑊𝑤−𝑊𝑑 𝑊𝑑 𝑥 100 = wac (1) 4.6 performance evaluation test the performance evaluation of bio-composite filled food warmer was carried out by obtaining two sets of identical coolers of different colour, size and manufacturer (regency and thermolineo) as shown in (figure 15) from (oja oba market in ilorin kwara state). a preliminary test was carried out to ensure that the two sets of coolers operated on the same level of efficiency. one each, from the two set of the coolers was carefully opened to expose the polyurethane insulation inside. the polyurethane was completely removed to leave the internal plastic bare after which it was filled with the bio-composite insulating material (figure 16). the bio-composite filled ice cooler was oven dried at 110 °c for 9 hours after which the inner plastic container was carefully inserted back to cover the insulating the material. two identical stainless steel moulds were filled with water and (allowed to completely freeze after which the ice were weighed and inserted individually into the four separate coolers, marked 1 (control) and 2(biocomposite). the lids of the two sets of coolers were firmly closed and the weight of the frozen block was taken at interval of 10 minutes. a total of five readings were obtained for the control coolers and the coir and bagasse filled coolers figure 13: water absorption capacity sample figure 14: samples under water absorption test. investigation of the thermo-physical and mechanical properties of coir and sugarcane bagasse for low temperature insulation 349 figure 15: coolers to serve as control (a) (b) figure 16: (a) regency cooler filled with coir and bagasse and (b) thermolineo cooler filled with coir and bagasse. 5 results and discussions 5.1 thermal diffusivity thermal diffusivity results calculated are presented in figures 17 and 18. the results showed that samples a, b and c (figure 17) have lower thermal diffusivity of 9.14 x 10−5,8.5 x10−5 and 8.1𝑥10−5 𝑚2/𝑠 respectively as compared with the control sample with a diffusivity value of 19.22𝑥10−5 𝑚2/𝑠. a decrease in the thermal diffusivity at sample b was noticed and further decease in thermal diffusivity was noticed at sample c. this is mainly due to the increase in coir content from sample a to c which increased the density of the samples thereby reducing the corresponding thermal diffusivity. similarly, samples d, e and f (figure 18) also recorded lower thermal diffusivity values compared with the control sample with sample f recording the lowest thermal diffusivity value of 5.1510−5 𝑚2/𝑠 for 1.0mm sieve size, sample f has the highest specific heat capacity of 1141.3 j/kgk and expectantly it has the lowest thermal diffusivity of 5.15× 10−5 𝑚2 𝑠⁄ . sample f has the lowest thermal diffusivity of the six samples tested with sieve size playing an important role as the larger sieve size gave a larger surface area for heat absorption leading to higher specific heat capacity values. ndagi et al. (2021). international journal of engineering materials and manufacture, 6(4), 340-356 350 figure 17: thermal diffusivity against 0.5 mm particle size at different coir:bagasse mix-ratio figure 18: thermal diffusivity against 1.0 mm particle size at different coir:bagasse mix-ratio 5.2 thermal conductivity the thermal conductivity results obtained are shown in table 2. it shows the relationship between the obtained thermal conductivity of the different constituent ratios and density. samples a, b and c had the same thermal conductivity of 0.01472 w/mk which is lower than the thermal conductivity of the control sample while samples d, e and f had thermal conductivities of 0.01467 w/mk also lower than that of the control sample. the samples exhibited the same thermal conductivity at 0.5mm particle size and at 1.0 mm particle size because the material used are the same regardless of the constituent ratio but the difference in their respective thermal conductivities across the two sieve size constituents, i.e, 0.5 mm and 1.0 mm, respectively can be attributed to the difference in sieve size. samples a, b and c are 0.5 mm sieve size while samples d, e and f are 1.0 mm sieve size making samples a, b and c denser as a result of smaller particle size which facilitates faster transfer of heat through conduction since the particles are more closely packed together leaving less room for voids and air compared to samples d, e and f which are 1.0 mm sieve size with bigger particles with more voids and room for air leading to lower conduction of heat. 0 5 10 15 20 25 control a 50:50 b60:40 c 70:30 t h e rm a l d if fu si v it y ( m ²/ s ) mix-ratio 0 5 10 15 20 25 control d 50:50 e 60:40 f 70:30 t h e rm a l d if fu si v it y (m ²/ s ) mix-ratio investigation of the thermo-physical and mechanical properties of coir and sugarcane bagasse for low temperature insulation 351 table 2: thermal conductivity and density 5.3 thermal resistivity the thermal resistivity of the samples can be inferred from the value of the thermal conductivity, since thermal resistivity is defined as the inverse of thermal conductivity. it can be expressed mathematically as: resistivity = 1 𝐾 (2) from equation 4.1 the thermal resistivity of 0.5mm particle size is given by 1 0.01472 = 67.93 w/m/k and that of 1.0mm particle size is given by; 1 0.01467 = 68.16 w/m/k therefore, the thermal resistivity of samples a, b and c is 67.93 w/k/k while samples d, e and f have thermal resistivity of 68.16 w/m/k. 5.4 water absorption capacity the results of water absorption capacity test for 0.5 mm and 1.0 mm sieve size are shown in figures (19 and 20). from (figure 19), sample c had the lowest water absorption capacity followed by sample b and sample a, the results showed that sample c absorbed 393 % of its initial dry weight as water which is high compared to the measured water absorption capacity of the control sample ( polyurethane) (126 %) samples d, e and f (figure 20) did not also fair better in the water absorption test, with sample f having the lowest water absorption capacity of 410 % in the 1.0 mm particle size category which is still higher than the absorption capacity of the control sample. sample d had the highest water absorption capacity of 449 %. the high water absorption capacity of all the samples can be attributed to the hydrophilic nature of coir and sugarcane bagasse which are the main constituents of the biocomposite material. also the binder being water soluble contributed to the high water absorption capacity of the bio-composite materials used. figure 19: water absorption capacity for 0.5 mm particle size at different mix-ratios at different coir/bagasse mixratio 0 50 100 150 200 250 300 350 400 450 control a50:50 b60:40 c-70:30 w a te r a b so rp ti o n c a p a ci ty ( % ) mix-ratio sample ratio sieve size (mm) thermal conductivity (w/m/k) density (g/cm³) control 100% polyurethane 0.01832 0.1670 a 50:50 0.5 0.01472 0.2474 b 60:40 0.01472 0.2765 c 70:30 0.01472 0.2599 d 50:50 0.01467 0.2453 e 60:40 1.0 0.01467 0.2515 f 70:30 0.01467 0.2494 ndagi et al. (2021). international journal of engineering materials and manufacture, 6(4), 340-356 352 figure 20: water absorption capacity for 1.0 mm particle size at different coir/bagasse mix-ratio figure 21: uts for different mix-ratios for 0.5 mm particle size at different coir/bagasse mix-ratio 5.5 ultimate tensile strength (uts) results for the ultimate tensile strength for 0.5 mm and 1.0 mm sieve sizes are shown in figures 21 and 22. samples a, b and c (figure 21) shows a rise in the uts of the samples and subsequent drop. sample a has a uts of 0.22mpa which rose to 0.251 mpa in sample b and eventually peaked at to 0.259 mpa in sample c. samples d, e and f (figure 22) show a steady continuous rise in the uts from 0.153 mpa for sample d to 0.182 mpa for sample e and finally peaking at 0.219 mpa for sample f. the steady continuous rise in the uts for samples d, e and f can be attributed to the increase in the coir percentage from 50% for sample d to 60%for sample e and 70% for sample f. this is due to the high lignin content of coir which aids in the binding process of the composite material thereby giving it higher tensile strength. of the six samples tested sample c had the highest uts of 0.259 mpa and it can be observed that samples b and c had higher uts compared to the control sample. meanwhile the control sample had higher uts compared to samples d, e and f this is due the sieve size of samples d, e and f which is 1.0 mm which gives a lower density and decrease in the cohesive bonding force between individual particles. 0 50 100 150 200 250 300 350 400 450 500 control d 50:50 e 60:40 f 70:30 w a te r a b so rp ti o n c a p a ci ty ( % ) mix-ratio 0 0.05 0.1 0.15 0.2 0.25 0.3 control d50/50 e 60/40 f 70/30 u lt im a te t e n si le s tr e n g th ( m p a ) mix-ratio investigation of the thermo-physical and mechanical properties of coir and sugarcane bagasse for low temperature insulation 353 figure 22: uts for different mix-ratios for 1.0 mm particle size at different coir/bagasse mix-ratio figure 23: compressive strength for 0.5 mm particle size at different mix ratio at different coir/bagasse mix-ratio 5.6 compressive strength the results for the compressive strength test recorded for 0.5 mm and 1.0 mm are shown in figures 23 and 24 respectively. samples a, b and c (figure 23) shows a steady increase in the compressive strength of tested bio composite, sample a had a compressive strength of 0.561 mpa which increased to 0.753 mpa for sample b and finally peaked at 0.876 for sample c which was significantly higher than the recorded compressive strength of the control sample. the steady increase can be attributed to the small sieve size of 0.5 mm and increased constituent effect of smaller sieve size and increase in coir content. samples d, e and f also exhibited similar behaviour as the compressive strength started low at 0.481mpa for sample d and rose to 0.522 mpa for sample e before peaking at 0.583 mpa for sample f. the overall low compressive strength of sample d, e and f as compared to samples a, b and c, can be attributed to the large sieve size of 1.0 mm which reduced the density and in turn affected the effective bonding of the bio-composite particles. 0 0.05 0.1 0.15 0.2 0.25 0.3 control d50:50 e 60:40 f 70:30 u lt im a te t e n si le s tr e n g th ( m p a ) mix-ratio 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 control a 50:50 b 60:40 c 70:30 c o m p re ss iv e s tr e n g th ( m p a ) mix-ratio ndagi et al. (2021). international journal of engineering materials and manufacture, 6(4), 340-356 354 figure 24: compressive strength for 1.0 mm particle size at different coir/bagasse mix-ratio figure 25: melt rate (regency cooler) 5.7 performance evaluation five readings were obtained during the performance evaluation test. the results obtained is shown figures 25 and 26. the results show a very close proximity of ice mass loss of the bio-composite material to that of the control food warmer with the regency food warmer control having a total mass loss of 42.1 g with a melt rate of 1.05 g/min and the bio-composite lined food warmer having a total mass loss of 43.33 g with a melt rate of 1.08 g/min within the time frame of 40 minutes within which the test was conducted. this represents a difference of 1.23 g with the control food warmer performing better than the bio-composite lined food warmer, similarly in figure 4.13 the thermolineo control food warner has total ice mass loss of 18.51 g with a melt rate of 0.46 g/min and the bio-composite filled thermolineo food warmer has a total mass loss of 19.86 g with a melt rate of 0.49 g/min. this shows a difference of 1.35 g with the control food ice cooler again performing better than the bio-composite lined cooler. the better performance of the control coolers over the bio composite food warmers can be attributed to lack of proper compaction during the filling process which led to cracks as the bio-composite coolers were being dried, this led to rapid heat transfer which accelerated the melt rate of the ice. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 control d-50:50 e 60:40 f-70:30 c o m p re ss iv e s tr e n g th ( m p a ) mix-ratio 0 50 100 150 200 250 300 0 1000 2000 3000 m a ss o f ic e ( g ) time (s) r egency control regency bio-composite investigation of the thermo-physical and mechanical properties of coir and sugarcane bagasse for low temperature insulation 355 figure 26: melt rate (thermolineo cooler) 6 conclusions the conclusions derived from the study can be summarised as thus: coconut coir and sugarcane bagasse have lower thermal conductivity and lower thermal diffusivity compared to polyurethane. all samples performed poorly in the water absorption test as compared to the control polyurethane sample. sieve size and density played important roles in the thermo-physical and mechanical performance of the bio-composite materials with particle size of 1.0 mm having higher density as coir percentage increased and performing better than 0.5 mm particle size in mechanical and thermal test ,1.0 mm particle size sample containing 70 % coir and 30 % bagasse is the most favourable for use as low temperature thermal insulating material to replace the synthetic ones presently being used as it performed favourably across the thermo-physical and mechanical tests that all prepared samples were subjected to performance evaluation test proved that the combination of coir and bagasse can be used to replace polyurethane insulating materials in low temperature thermal insulation application. references 1. dávid bozsaky, “the historical development of thermal insulation materials,” ŕ periodica polytechnica architecture 41/2 (2010) 49–56 doi: 10.3311/pp.ar.2010-2.02, 2011 2. krishpersad manohar “biodegradable thermal insulation for ice-coolers,” international journal of modern engineering research 1 2 (2011) 559-563 3. agency for toxic substances and disease registry (atsdr), “toxicological profile for synthetic vitreous fibers,” (atlanta: u.s. department of health and human services, (2004). 4. g. s. kochhar and k. manohar, “effect of moisture on thermal conductivity of fibrous biological insulating materials,” proc. ashrae thermal performance of the exterior envelope of buildings vi, (clearwater beach, florida, usa, 1995), 33-40. 5. p.f. infante, et al “fibrous glass and cancer,” american journal of industrial medicine 26, (1994) 559-584 6. j. pinto et al “characterization of corn cob as a possible raw building material,” construction build mater (2012) 34: 28–33. 7. s. abdulkareem et al, (2016). “investigation of thermal insulation properties of biomass composites,”. international journal of technology. 17 6 (2016) 849-859. 8. kyauta e.e. dauda d.m. and justin e, (2014). investigation on thermal properties of composite of rice husk, corncob and baggasse for building thermal insulation. american journal of engineering research (ajer) e-issn: 2320-0847 p-issn: 2320-0936 volume-03, issue-12, pp-34-40 9. sunil e m, g. manavendra, (2017). experimental investigation on thermal properties of bagasse fly ash reinforced epoxy composite. international research journal of engineering and technology (irjet) volume: 04issue: 09 www.irjet.net. 10. upadhyay a. harshaloza j (2015). investigation on effect of coconut husk as an insulation on primary energy and co2 emissions of residential buildings. international journal of advance engineering and research development volume 2, pp 140-154. 0 20 40 60 80 100 120 140 0 500 1000 1500 2000 2500 3000 m a ss o f ic e ( g ) time (s) thermolineo control thermolineo bio-composite http://www.irjet.net/ ndagi et al. (2021). international journal of engineering materials and manufacture, 6(4), 340-356 356 11. fong a.l, n a n khandoker and s debnath, (2018). development and characterization of sugarcane bagasse fibre and nano-silica reinforced epoxy hybrid composites. iop conf. series: materials science and engineering 12. y., mohd yuhazri, et al “optimization of coconut fibers toward heat insulator applications,” global engineers & technologists review www.getview.org. 13. agunsoye, j.o. aigbodion, v.s (2013). bagasse filled recycled polyethylene bio-composites: morphological and mechanical properties study. 14. suresh babu.r, karthikeyan.v, vigneshkumar.g (2015), investigation of thermal insulation on ice coolers. iosr journal of mechanical and civil engineering (iosr-jmce) e-issn: 2278-1684, volume 12, ver. iv (pp 75-79). 15. ayugi, g e.j.k.b. banda, f.m. d’ujanga (2011). local thermal insulating materials forthermal energy storage. rwanda journal, series c, mathematical sciences, engineering and technology. volume 23 pp 156-165. 16. dhivar, p. s, patil a. s (2017), thermal insulation using agricultural by-product:a review.iosr journal of mechanical and civil engineering (iosr-jmce) pp. 53-61www.iosrjournals.org. 17. eeydzahaminudin, n, khalid a., nor azman, k, mohdfadhilmd d, rozana z, and nurazmira z, (2017). utilization of baggase waste based materials as improvement for thermal insulation of cement brick. matec http://www.getview.org/ international journal of engineering materials and manufacture (2021) 6(3) 170-175 https://doi.org/10.26776/ijemm.06.03.2021.08 m. summers and b. asiabanpour ingram school of engineeringtexas state university san marcos, tx 78666 usa e-mail: ba13@txtstate.edu reference: summers and asiabanpour (2021). improving heat transfer from peltier devices used in an atmospheric water generation. international journal of engineering materials and manufacture, 6(3), 170-175. improving heat transfer from peltier devices used in an atmospheric water generation mark summers and bahram asiabanpour received: 28 february 2021 accepted: 29 april 2021 published: 15 july 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract present atmospheric water generation (awg) systems are useful for providing water in areas with limited water supplies. many industrial awg systems use vcr (vapor-compression refrigeration) to achieve a large amount of cooling to extract liquid water out of the air. these systems require large amounts of energy to operate, usually in the form of diesel or ac-powered generators. the systems also have many moving parts that require maintenance and use refrigerants that can leak and cause problems with the environment. an alternative awg solution is to use dc-powered peltier devices (thermoelectric coolers) to reduce the temperature of condensation plates to extract water from the air. this solution eliminates the issues with traditional industrial awg systems since the peltier devices are solid-state, have very long mean-time between failure (mtbf) performance, and can be powered by solar panels that eliminate the need to burn hydrocarbon-based fuels or have access to a reliable power grid. also eliminated is the need to use chlorofluorocarbon (cfc) or hydrochlorofluorocarbons (hcfc) refrigerants that have been shown to deplete the ozone layer. this paper will present methods to improve the efficiency of the thermoelectric coolers by more efficiently extracting heat from the hot side of the device. this efficiency will be quantified by evaluating the coefficient of performance (cop) of the thermoelectric cooler under the various operating conditions. different combinations of conductive heat transfer using aluminium heatsinks, convection heat transfer using forced airflow, and phase change heat transfer using copper heat pipes filled with distilled water will be investigated and evaluated. keywords: awg, atmospheric water generation, thermoelectric coolers, simulation, modelling, optimization 1 introduction meeting the growing water demand is proving to be one of the most critical challenges of the century [1]. the african wildlife foundation estimates that people need 20 to 50 litres of clean water daily to meet their basic needs and in emerging economies, women spend 40 billion work hours each year walking to collect freshwater [2]. even in developed countries, the increased industrial and agricultural use of water that often comes from freshwater sources has created an urgent demand for other sources of freshwater [3]. unfortunately, the naturally occurring freshwater sources are not replenished at a rate to match the growing demand. the need for water also comes with a high energy demand, which, in turn, comes with its water demand. the water demand cannot be studied or met without also considering the resulting energy demand. energy is required to pump, heat, treat and cool and deliver water [4]. many options exist to help increase the supply of water to these areas in need. desalination of seawater, the building of aqueducts to transport water from areas with more abundant water supplies, and over-the-road transport of water from one region to another are all possible options, but require infrastructure that might not be in place. other options include commercial atmospheric water generation (awg) systems, but these require an infrastructure of reliable power to make it happen. current commercially available awg systems from companies like innovaqua water solutions, quality water treatment, and atmospheric water solutions have products that can produce water, but have two major drawbacks that we want to address in this research: • requirements for uninterrupted reliable access to grid power. • lack of intelligence to determine operating schedule to ensure maximum utilization of available power. since our target audience has neither reliable access to power, nor the ability to efficiently determine when to operate the system, our system is focused on optimization to know when to operate the system based on local improving heat transfer from peltier devices used in an atmospheric water generation 171 atmospheric conditions (dry bulb temperature and relative humidity) and available power (current kw-hr capacity and the forecast for near-term solar generation). 2 awg system description atmospheric water generation (awg) offers a sustainable option to secure freshwater for years to come [5]. awg is expected to be an $8 billion market by 2024 [6]. awg is the process of removing and collecting water vapor from the air. condensation forms when air at the saturation temperature comes in contact with a surface that is below this saturation temperature [7]. awg systems cool a surface and then pass air over it, allowing the moisture to be extracted from the air as it passes [8-9]. awg systems can rely on a wide array of cooling techniques. standard systems use refrigerant-based dehumidification, vapor compression, and vapor absorption refrigeration or desiccant liquid. recently, other methods such as thermo-electric cooling and heat exchange using lower ground temperatures have been studied [10]. all of these cooling techniques that make awg possible require power. current awg systems require a minimum of 6.8 g/m3 water vapor density and operate ideally at the world standard conditions of 26.7 ºc and 60% rh to operate at an efficiency of 0.4 kwh/l [11]. in the meantime, the economic aspects of the awg systems and the feasibility of their usage compared to other sources of freshwater have been studied [12-14]. the techniques and methods that improve the efficiency of such awg systems in produce more water with less energy is an area of interest for scaling these methods from laboratory scale to commercial and widespread use. one of the methods of awg systems is to use dc-powered peltier devices (thermoelectric coolers) (fig. 1) to reduce the temperature of condensation plates to extract water from the air. this solution eliminates the issues with traditional industrial awg systems since the peltier devices are solid-state, have very long mean-time between failure (mtbf) performance, and can be powered by solar panels that eliminate the need to burn hydrocarbon-based fuels or have access to a reliable power grid. also eliminated is the need to use chlorofluorocarbon (cfc) or hydrochlorofluorocarbons (hcfc) refrigerants that have been shown to deplete the ozone layer. however, thermoelectric coolers have relatively low efficiency. vapor-compression refrigeration (vcr) systems as used in many residential and commercial buildings offer much better efficiency. however, they have many moving parts (not solid-state), have lower mtbf, and require reliable sources of alternating current. they also require refrigerants that have been proven to cause damage to the earth’s atmosphere. additionally, the thermoelectric cooler device operates on the peltier effect. the device can accept dc as input and produce a delta temperature as an output (peltier), or can accept a temperature difference as input and produce a dc as output. a major challenge with peltier devices is providing adequate cooling to the hot side of the device. the device can only produce a temperature difference (δt). the idea is to attach a condensation plate to the cold side to condense atmospheric water out of the available air to produce water. to minimize the power needed, the challenge is to remove heat from the hot side in an efficient manner to maximize water generated per watt-hour energy expended. this paper will present methods to improve the efficiency of the thermoelectric coolers by more efficiently extracting heat from the hot side of the device. the rest of this paper is organized as the following. in section 3, method and materials including modelling and manufacturing are presented. section 3 illustrates the results including the simulation model and fabricated test system. conclusions and discussions are presented in section 4. figure 1: the semiconductor thermoelectric cooler with hot and cold sides [15] summers and asiabanpour (2021): international journal of engineering materials and manufacture, 6(3), 170-175. 172 3 methods and materials laws of nature constrain us to the fact that heat will naturally move from hot objects to cold objects. physics provides us with four basic methods to move heat in the opposite direction: convection (solid material as a medium), conduction (gas/fluid as a medium), radiation (via electro-magnetic radiation), and phase change (solid-to-liquidto-gas). this work has employed all but radiation techniques to systematically determine the best combination to optimize the temperature reduction of the hot side of the peltier devices. the approaches used are as follows. • convection: round aluminium finned heat sinks of various lengths. • conduction: dc tube axial fans blow air across these heat sinks. • phase change: copper wicked heat pipes with distilled water under vacuum. an initial awg testbed including a platform with (4) single commercial 40mm x40mm tec assemblies cooled with rectangular aluminium heat sinks (conduction) and dc fans (convection) and the system was tested for its efficiency (fig. 2). the results illustrated that the heatsink mechanism is not efficient enough and the system is not getting cold enough in an energy-efficient fashion to produce water economically. since the peltier devices can only generate a temperature difference between the hot and cold side of the device, when the hot side is not cooled in an efficient manner, the temperature of the cold side rises as well, which causes reduced condensation and also causes the pelter device to operate at a lower cop (fig 3). as a result of this initial testing, two new approaches were implemented. a) increase surface area of the condensation plates. b) improve heat transfer away from the hot side of the tec. to improve the system, parallel modelling/simulation and fabrication/experimentation approaches were pursued to optimize the system. this study focuses solely on the modelling and simulation aspects of the work. figure 2: original 4 tec platform figure 3: tec coefficient of performance improving heat transfer from peltier devices used in an atmospheric water generation 173 3.1 modelling and simulation solidworks software was used to develop a manufacturing computer model of the system (fig.4) including the tec, heatsink, fans, and other mechanical structures. additionally, solidworks built-in flow simulation was used to implement computation fluid dynamics (cfd) modelling. this new improved test platform was about double the size of the original test platform. it contains (4) 8-1/2” x 8-1/2” x 1/8” aluminium condensation plates, (4) 235 cfm cooling fans, and varying arrangements of one, two three, and four tec configurations. also added were spiral ducted air plenums to more efficiently direct the airflow over the new round heat sinks. four different configurations of heat sink/heat pipe assemblies were designed and manufactured to test the hypothesis of using various combinations of multiple heat transfer mechanisms to optimize the water generation results (fig. 5). figure 4: original 4 tec platform (a) (b) figure 5: awg test platform with configurable condensation plate assemblies (a) and hybrid heat sink / heat pipe cooling assembly (b) summers and asiabanpour (2021): international journal of engineering materials and manufacture, 6(3), 170-175. 174 4 results the improved awg test platform proved to be much better than the original. the individually configurable condensation plates will allow multiple arrangements of tecs and consistent test results. the cfd analysis was done closely matches the actual hardware temperature performance, which will allow for much quicker “what-if” simulations without building additional hardware (fig. 6). figure 6: computation fluid dynamics (cfd) simulation of four-way duct design the approach that was used regarding mesh sensitivity was different than our earlier efforts. initially, multiple simulations were run at various mesh sizes and configurations to see if we could identify locations of the simulation that produced different results based on the mesh size. this proved to be a very time-consuming process. therefore, instead we chose to use an initial default mesh and compared the simulation results to measurements from the instrumented hardware. we implemented vernier temperature probes and air flow meters to make these measurements. when the simulation results deviated significantly from the measured results, a finer local mesh in these regions was applied until a satisfactory correlation was achieved. adding the heat pipes offered marginal benefits on the initial testing. however, additional configurations are using larger diameter heat pipes that still need to be manufactured and tested. bluetooth temperature sensors allow temperature probing of the surface of the heatsinks, hot and cold sides of the tecs, and airflow temperature. airflow sensors allow validation of the results of the cfd analysis, which further strengthens the ability to perform “what-if” design changes to the duct geometry for design iteration improvements without the need for time-consuming and costly fabrication of intermediate design improvements. 5 conclusion and discussions cfd simulation and validation results were very close to actual measured values. to quantify these correlations, we utilized a flir c2 thermal camera to capture the transient temperature profile of the four-tec condensation plate configuration [fig. 7] and correlated it the steady-state results of the associated solidworks flow simulation results. this validation model will facilitate a wide range of design of experiments tests and optimizations without the need to fabricate physical models. due to the scalable design of the awg test platform, once the initial design achieves an adequate level of optimization, multiple copies of the test platform can be manufactured into a unit suitable for field tests. a separate optimized solar panel system is also being designed and tested for potential use as a power source for the awg system. the peltier devices are still operating at a sub-optimal coefficient of performance (cop). ideas for increase optimization include heat sinks with a higher number of thinner fins, investigation of additional tec arrangements (new spacings and quantities), incorporation of computer-controlled power inputs based on local atmospheric conditions (dry-bulb temperature, atmospheric pressure, and relative humidity). improving heat transfer from peltier devices used in an atmospheric water generation 175 figure 7: the transient temperature profile of the four-tec condensation plate configuration by thermal camera acknowledgement this work was completed with funding from the us department of agriculture (grant # 2016-38422-25540). the authors would like to thank the usda and texas state university for providing funding and access to both infrastructure and laboratories. the sponsors are not responsible for the content and accuracy of this article. the authors declare that there is no conflict of interest regarding the publication of this paper. reference 1. postel, sandra l. “entering an era of water scarcity: the challenges ahead.” ecological applications, vol. 10, no. 4, 2000, pp. 941–948. jstor, jstor, www.jstor.org/stable/2641009. 2. weil, sydney. “how does water use in the united states compare to that in africa?” african wildlife foundation, 6 sept. 2013, www.awf.org/blog/how-does-water-use-united-states-compare-africa. 3. wilson, lynn. “the costs of fresh water in a changing world (op-ed).” livescience, purch, 22 apr. 2014, www.livescience.com/45049-costs-of-fresh-water.html. 4. “ensuring the resiliency of our future water and energy systems.” department of energy, 2014, www.energy.gov/articles/ensuring-resiliency-our-future-water-and-energy-systems. 5. adeoye, o.o., et al. “atmospheric water generation: a path to net-zero.” 2016 ieee green technologies conference (greentech), 2016, doi:10.1109/greentech.2016.16. 6. "atmospheric water generator market us$8 billion revenue by 2024." pr newswire, 15 nov. 2017. 7. esfahani, j.a., modirkhazeni, s.m. 2012. “modeling of laminar, film-wise condensation.” in ahsan, amimul, water condensation: process, modeling and control, pp 1-70. nova science publishers inc., new york. 8. almusaied, z., asiabanpour, b. atmospheric water generation: technologies and influential factors.”. institute of industrial and systems engineers research conference 2017, pa, 2017. 9. ownby, n., and asiabanpour, b. “reduction of power consumption in atmospheric water generation”, 9th international conference of environmental science and technology, houston, tx, 2018. 10. pontious, k., weidner, b. guerin, n. dates, a. pierrakos, o., and altaii, k., "design of an atmospheric water generator: harvesting water out of thin air," 2016 ieee systems and information engineering design symposium (sieds), charlottesville, va, 2016, pp. 6-11. doi: 10.1109/sieds.2016.7489327 11. wahlgren, ronald v. 2016. “water-from-air quick guide: second edition”. atmoswater research, north vancouver, bc. 12. asiabanpour, b., ownby, n., summers, m., moghimi, f. (2019), "atmospheric water generation and energy consumption: an empirical analysis", ieee texas power and energy conference (tpec), 1-6 13. moghimi, f., ghoddusi, h., asiabanpour, b., behroozikhah, m. (2019), "atmospheric water generation (awg): performance model and economic analysis", ifip international conference on advances in production management systems 14. moghimi, f., ghoddusi, h., asiabanpour, b., behroozikhah, m. (2021), "is atmospheric water generation an economically viable solution?", clean technologies and environmental policy, 1-18. 15. parinov, i. and shun-hsyung-chang (2013), "research opportunity to use mism structures for cooling of light-emitting diodes", edition: nova publisher: nova science publishers, inc, isbn: 978 – 1 – 62618 – 535 – 7, doi: 10.13140/rg.2.1.4082.4162 international journal of engineering materials and manufacture (2021) 6(3) 209-224 https://doi.org/10.26776/ijemm.06.03.2021.13 akash sali 1 , vivek patel 1 , wayne hung 1 , james hyder 2 , david hyder 2 , mike corliss 2 1 texas a&m university, college station, texas 77843, usa 2 knust-godwin llc, katy, texas 77494, usa e-mail: hung@tamu.edu reference: akash et al. (2021). electron beam welding of laser powder bed fused inconel 718. international journal of engineering materials and manufacture, 6(3), 209-224. electron-beam welding of laser powder-bed-fused inconel 718 akash sali, vivek patel, james hyder, david hyder, mike corliss and wayne hung received: 17 april 2021 accepted: 01 may 2021 published: 15 july 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract this study explores the application of electron-beam welding (ebw) for joining laser powder-bed-fused inconel 718 (l-pbf in718) superalloy. three different levels of electron beam speed and beam current were explored to give nine different electron beam heat inputs for experimentation. to define the weld characteristics microhardness, tensile, and fractography analysis using scanning electron microscopy, optical microscopy, and energy dispersive spectroscopy were conducted. typical nail-shaped weld geometry was observed with penetration depth proportional to heat input. most welded samples exceeded the yield strength (600mpa) and tensile strength (920mpa) requirements from the astm f3055 specifications for additively manufactured in718, however, the specimens did not meet the ductility requirements (27%). brittleness of the weld was attributed to the presence of brittle secondary phases in the weld matrix, and unfused metal powder of adjacent l-pbf layers. post-processing heat treatments were recommended to improve the weld quality while improving the ductility of ebw joints. keywords: electron beam welding; inconel 718; laser powder bed fusion; microhardness; mechanical properties; fractography. 1 introduction additive manufacturing has exceeded from being a mere prototyping method to a method of production given its advantage in generating near-net-shaped parts with complex geometries. selective laser melting (slm) or laser powder-bed-fusion (l-pbf) process is additive manufacturing (am) technique in which adjacent layers of fine metal powder are selectively fused with a powerful laser beam. due to this layer-wise method of producing metal components and quality products, l-pbf has gained popularity in the aerospace, defence, energy, medical, and automotive industry. however, due to the limited size of current powdered fusion machines and high costs associated with the production of large parts, l-pbf is not being utilized to its full potential currently and imposes restrictions on the size of the parts that can be printed using this method. thus, there is a need to explore an efficient way to join these parts reliably. nomenclature: am additive manufacturing dta differential thermal analysis ebw electron beam welding edm electrical discharge machining dta differential thermal analysis εf elongation haz heat affected zone in718 inconel 718 l-pbf laser powder bed fusion sem scanning electron microscopy slm selective laser melting tig tungsten inert gas welding uts ultimate tensile strength ys yield strength electron beam welding of laser powder bed fused inconel 718 210 inconel 718 (in718) is a nickel-based superalloy that has an excellent performance in terms of tensile strength, hardness, and corrosion resistance at high temperatures up to 600˚c [1]. due to this advantage, in718 is widely used for high-temperature applications in the energy, defence, and aerospace industries. the strain hardening property of in718 imposes restrictions on the complexity and cost of conventional machining processes [2]. thus, l-pbf has gained popularity as a preferred method of producing complex-shaped in718 parts. although expensive and need complex control systems, electron beam welding (ebw) has proven to be an excellent welding method that produces welds with deep penetrations, minimal heat-affected zones, and high joint strength [3]. this method also imposes minimal thermal impact and prevents excessive deterioration of microstructural and metallurgical properties of a weldment. due to limited published literature on ebw of additive manufactured metals, this research explores the possibility of using ebw to join l-pbf in718 parts, examines the resulted weld quality, and compares mechanical properties of welded specimens against the standard astm material specifications for am in718. 2 literature review microstructures and mechanical properties of l-pbf in718 have been studied; however, a comprehensive study on ebw of l-pbf in718 is yet to be found. background studies of ebw of rolled in718 and aluminium alloys were found together with brazing and arc welding of l-pbf in718. 2.1 microstructure of in718 the in718 is a nickel-based superalloy (ni 50-55%, cr 17-21%, fe 17%, nb 4.75-5.5%, mo 2.8-3.3%, ti 0.651.15%, al 0.2-0.8%, c<0.8%, co<1.0%, cu<0.3%, si<0.35%, mg<0.35% [4]). this alloy exhibits high tensile strength and depicts high creep resistance at higher temperatures owing to the formation and stability of various secondary phases in its microstructure [5]. these phases also cause strain hardening and affect the ductility of the in718. a solidification phase diagram of in718 was prepared using phases formed after a non-equilibrium welding process in a research study [6]. the specimens were heat-treated at 1000˚c for 1hr. differential thermal analysis (dta) was performed to define the solidification phases. heating was conducted in an argon-controlled environment at 10˚c/min up to 1450˚c. the samples were cooled through all significant solidification temperatures at a rate of 10˚c/s. the solidification phase diagram based on the composition of nb at various temperatures is presented in figure 1. molten in718 undergoes solidification in three stages [7]: ─ first, the liquid solidifies to secondary γ phases (γ’ and γ’’) and led to the formation of nb, c, ti, and al precipitate in the interdendritic regions. ─ second, the carbon present in the alloy was consumed by the segregated particles leading to the formation of intermetallic carbides. ─ third, further enrichment of the solute led to laves phase formation. the segregated nb was shared by all the secondary phases δ (incoherent ni3nb), γ’ (ni3al), γ’’ (ni3nb), laves ((ni,cr,fe)2(nb,mo,ti)), and carbides during solidification. thus, a higher percentage of one of the phases meant less percentage of the other. of these phases, the γ’ and γ’’ are the strengthening phases and should be present in the higher percentage. thus, it is necessary to control the formation of the other deteriorating phases like the δ, laves, and carbides. these phases are formed due to fast cooling as found for welding or laser processing. during the l-pbf process, although the metal may reach the specified temperatures since the laser beam moves at a relatively fast feed rate, the exact phases that will be formed doing the process cannot be predicted accurately. however, the phase diagram for equilibrium conditions with a very slow cooling rate only gives a general idea of different secondary phases of the in718 alloy. figure 1: solidification diagram for in718 [6] 1000 1050 1100 1150 1200 1250 1300 1350 1400 0 5 10 15 20 25 t e m p e ra tu re ( ˚c ) nb (wt%) γ γ+liquid liquid laves solubility limit of nb solidus liquidus avg. eutectic constituent composition dendrite solidus avg. eutectic γ avg. eutectic laves γ+laves sali et al. (2021): international journal of engineering materials and manufacture, 6(3), 209-224. 211 2.2 anisotropic properties of l-pbf in718 since l-pbf metals have properties different than the conventionally manufactured counterparts due to the layerwise building followed by quick solidification, localized heating, and cooling which leads to residual stresses, and development of pores due to lack of fusion or shrinkage [8]. the building of l-pbf components layer-by-layer also tends to produce anisotropic mechanical properties. to establish this theory, mechanical properties of the l-pbf in718 samples with (a) building direction parallel to the testing direction (vertical), and (b) building direction perpendicular to the testing direction (horizontal) were compared. it was found that: ─ building direction did not affect the hardness of both samples. ─ the difference in tensile strength and elongation about 100mpa and 3-8% respectively were observed between the horizontal and vertical samples in both as-printed and direct aged samples. this directional variation was due to different residual stresses, accumulated dislocations, and crystallographic orientation in the loading direction. the claim was also supported by another research [9] which associated the observed difference in mechanical properties with a higher number of inter-layer joints in the loading direction and to the different distribution of the γ” phase. 2.3 ebw of rolled in718 since no previously published literature was found for ebw of l-pbf in718, various literature on ebw of rolled in718 was studied to establish the base for this study. the effect of various pre-weld heat treatment conditions on heat-affected zone formation after ebw was studied using microhardness measurements [10]. the sheets of in718 samples were solution treated at 950˚c for 1hr followed by water quenching. some were further treated by precipitation treatment at 760 ˚c for 4hr followed by water quenching. ebw was done with the first pass (50kv, 100ma, 2173mm/min, and 3.46mm focus depth), following with the second pass (50kv, 60ma, 1524mm/min, and 3.42mm focus depth). the hardness test result revealed a lower hardness of the fusion zone/ haz as compared to base metal for precipitation pre-treated samples. the asreceived and solution pre-treated samples had a uniform hardness distribution. the spike in hardness values for precipitation treated samples was associated with their high thermal sensitivity and precipitation of γ’ and γ’’ phases in the haz. an attempt was made to reduce the formation of laves phase and niobium segregation on solution-treated in718 plates to improve the tensile properties of the weld [11]. electron beam oscillations during the welding process were performed: (i) un-oscillated welding: 55kv, 22ma, 1.5m/min, and focus above the sample surface; (ii) elliptical oscillated welding: 15hz frequency, 55kv, 25ma, 1.5m/min, and focus on the sample surface. the welded samples were treated at two different solutionising conditions: 980 ˚c/1h air cooling and 1080 ˚c/1h, air cooling. some samples were further treated using dual aging at 720 ˚c/8h, furnace cooling followed by 620 ˚c/ 8h, air cooling. the elliptical weld oscillations were the most effective in reducing the segregation of niobium and laves formation and achieving a higher tensile test. oscillating welds led to the formation of several small weld pools at any point in time leading to better cooling rate, high fluid flow, and reduced thermal gradients in the weld pool leading to better weld quality. the ebw heat input (equation 1) affects the fusion zone and haz microstructure while controlling liquation cracking and segregation of alloying elements [12]. 𝐻𝑒𝑎𝑡 𝐼𝑛𝑝𝑢𝑡 ( 𝐽 𝑚 ) = 𝐵𝑒𝑎𝑚 𝐶𝑢𝑟𝑟𝑒𝑛𝑡 (𝐴) × 𝐵𝑒𝑎𝑚𝑣𝑜𝑙𝑡𝑎𝑔𝑒 (𝑉) 𝑊𝑒𝑙𝑑𝑖𝑛𝑔 𝑠𝑝𝑒𝑒𝑑 ( 𝑚 𝑠 ) (1) figure 2: weld width versus heat input [12] 0 500 1000 1500 2000 2500 3000 3500 4000 36 72 112 144 180 b e a d w id th ( m m ) heat input (j/mm) bottom middle top electron beam welding of laser powder bed fused inconel 718 212 cold rolled in718 sheets were ebw’ed at 30mm/s feed rate, 60kv voltage, and currents of 18ma, 36ma, 56ma, 72ma, and 90ma. microstructural analysis revealed that the width of the fusion zone increased with increasing heat input. this was due to the higher melting of base metal at a higher beam current. the width of the weld also varied along with the depth of penetration as seen in fig. 2. but heat input variation did influence the formation of microfissures in haz. the lowest heat input sample indicated the presence of haz micro-fissures while all other samples were free from it. this was associated with a higher temperature gradient in haz at lower heat input providing a higher grain boundary area for cracking [12]. pre-weld heat treatments also affect the geometry of the weld [13]. plates of in718 were subjected to various heat treatments: 1100 °c/1 h, air-cooled; 1040 °c/1 h, air-cooled; 950 °c/1 h, air-cooled. ebw parameters were 125kv, 65ma, and speeds of 1270, 1207, and 1143mm/min. weld with a nail-head shape was observed when the sample was treated at 1000˚c for an hour and cooled by air cooling as opposed to the stemless wine glass shape in asreceived condition. the total haz crack length also increased from 40µm to 675µm due to the pre-heating of the base metal. the microstructure analysis also revealed an increase in the laves formation and a decrease in haz cracking as the welding speed was decreased. a variation in mechanical properties of a 12mm thick penetration weld on as-received in718 hot rolled plates with ebw parameters of 60kv, 120ma, and 11mm/s for the first pass and 60kv, 30ma, and 11mm/s for the second pass was observed after tensile testing at 650˚c [14]. the tensile strength was best at the bottom of the weld (1185mpa) and worst at the top (1100mpa). the strength of the base metal was 1240mpa. elongation at fracture also increased from the top (9%) to bottom (18%). this was due to the brittle fracture surface of the weld at the top. the elongation of the base metal was 22%. the ebw was successfully utilized to join as-received 12.7mm-thick rolled in718 plates [15]. ebw parameters were: 50kv constant voltage, current of 65, 60, and 50ma, and speeds of 660.4, 787.4, and 914.4mm/min. weld area and penetration depth increased with increasing heat input. however, root keyhole defects were observed at a heat input higher than 247.6j/mm. samples welded at low heat inputs exhibited higher tensile strength that exceeded base material specification (837mpa) and fractured outside the weld with typical elongation of 57% while those samples that welded at a higher heat input fractured at the welds. in summary, ebw has been successfully utilized to join wrought in718 plates. pre-welding thermal treatment, optimal ebw process parameters, and oscillations of the beam help to achieve a favourable microstructure, therefore, resulting in good mechanical quality. these observations were utilized during the planning of our research. 2.4 defects formation in ebw porosity is found in the welded zone due to (i) the presence of releasing gas in molten metal, (ii) trapping of void due to the dynamic flow of molten metals at certain viscosity, and (iii) shrinkage cavity from molten metal at fast cooling rate. instability of the keyholes in the partial penetration welds, dissolved and trapped gases and solidification shrinkage led to the formation of voids and pores in ebw of rolled cp-titanium alloy [16], [17]. the fast-cooling rates of ebw associated with high welding beam speed and narrow weld area prevented the escape of the gas bubbles, therefore, formed pores in the weld zone. small pores were also seen on the fusion zone boundary due to the poor flow of molten metal over the gases trapped on the solid walls at the fusion zone boundaries. the irregular-shaped voids were formed due to shrinkage caused by the volumetric difference of liquid and solid phases during solidification. an offset between the weld path and joint location was stipulated to cause the melt bubbles to travel sideways and keep growing preventing them from getting released from the melt pool thus giving rise to the porosity at the top of the weld zone. figure 3: schematic of ebw defects [17] active zone void cold shut root void unmelted lump sali et al. (2021): international journal of engineering materials and manufacture, 6(3), 209-224. 213 various weld defects like porosity, un-melted lumps, spiking, and cold shut as seen in fig. 3 were characterized and compared on ebw of eight different metals [18]. the root voids observed towards the tip of the penetration due to the entrapment of gases depended on the chemical composition of each material. the presence of gaseous elements like nitrogen and oxygen, and high vapor pressure elements like magnesium influenced the formation of these voids. active zone voids formed in the vicinity of the beam travel path again depended on the presence of gaseous elements in the material and were directly proportional to beam current, power, and density. un-melted lumps were seen around the active zone porosity. spiking or long chains of porosity on top of the weld was formed due to arcing in the electron gun and formation. 2.5 joining of l-pbf metals varestraint tests conducted on tungsten inert gas (tig) welded joints of l-pbf in718 indicated that the as-printed welds had similar crack susceptibility as that of the wrought in718 samples [19]. cracking was associated with the formation of large grain structures after exposure to high temperatures leading to grain boundaries having higher stress concentration which led to crack initiation. the brazed joint of 4mm thick in718 plate indicated two distinct zones at the joint namely the isothermally solidified zone with a hardness of 460hv and the diffusion affected zone with a hardness of 490hv [20]. the base metal had a hardness of 475hv. the brazed joint had a shear strength equal to 77% of the base metal. ebw of l-pbf alsi10mg alloy was characterized with defects at the overlap of weld pools and had minimal haz [21]. higher welding speeds led to deeper weld penetration but also produced higher porosity in the welds. the use of lower speeds at high heat input was found to produce higher porosity in weld metal than what was present in the base metal. the welds also had a lower hardness (103hv) as compared to the base metal (111hv). the published information is yet to be found for ebw of l-pbf in718 despite a growing demand for such applications. thus, this research studies the l-pbf in718 samples welded by ebw and compares the joint properties with the astm f3044-14a standard for am in718. 3 experiments gas atomized in718 powder with an average particle size of 50μm was used for producing l-pbf test samples. the chemical composition (weight %) of the powder was: 51.99ni, 18.58cr, 19.73fe, 5.17nb, 3.02mo, 0.99ti, 0.49al, 0.024c, 0.14co, 0.12cu, 0.073si, and 0.074mg. the samples (100x12.7x13mm) were printed on a renishaw am400 system with 275w laser power, 0.786m/s scanning speed, 110μm hatching distance, 60μm layer height, and stripe scanning pattern. to represent and simulate an ideal welded condition (i.e., full penetration, precisely machined joint faces and accurately aligned parts), through-thickness ebw beads were produced on the tensile samples to simulate the ideal joining of two separate parts. the as-printed samples were welded using ebw with each combination of three levels of beam current and welding speed giving nine different heat inputs in the range 180 295j/mm necessary for deep weld penetrations (table 1). two repeats were produced to test the repeatability of the results. the electron beam was focused on the surface of the samples with a constant voltage of 50kv and in a vacuum environment of <1μtorr. the samples were arranged as seen in fig. 4 with spacers to thermally insulate adjacent samples. the sciaky ebw system was programmed with a non-oscillating beam moving perpendicular to the l-pbf build direction. all welded samples were stress-relieved at 970˚c for 1hr to mitigate any residual stresses generated during the ebw process. coupons for hardness test (20x12.7x2.5mm) and weld geometry analysis were separated from the welded samples using wire-type electrical discharge machining (wire edm). these coupons were labelled using unique markings and moulded in epoxy using a struers citopress-15 machine for subsequent microhardness testing and microstructural studies. figure 4: ebw process setup electron beam welding of laser powder bed fused inconel 718 214 moulded samples were ground using struers abripol-20 grinding machine at five different grinding wheels emergy-80, piano md – 80, 220, 500, and 1200 grit in that sequence. ground samples were cleaned ultrasonically in isopropyl alcohol for at least 2 minutes. the dremel 3000 hand polisher and diamond pastes of 5-7μm, 1μm, and finally with 0.5μm abrasive size were used for polishing the samples. aqua regia etchant (4-part hcl (33%) + 1-part hno3 (67%)) was swabbed on the polished coupons until the weld profile was visible. wire edm was used to machine the profile of tensile test samples as per astm e8 specification from the ebw samples. the top and bottom of the ebw samples were milled to achieve the required test sample thickness of 6mm. the milling process removed possible defective zones at the top and bottom of a weld. the schematic of the final tensile test samples is shown in fig. 5. the olympus stm6 optical microscope was used to analyse the weld geometry and identify surface defects. highresolution images of the welds and vicinities were enhanced using computer software to measure the weld penetration depth and weld area. the wilson vh1102 vickers hardness tester was used with a 300gf load and 15sec dwell time for hardness testing. multiple indentations were performed at two levels a and b as shown in fig. 6. indentations were also performed at the weld centre between these two levels. the mts 800 universal tester was used for tensile testing (100kn loadcell, 0.5mm/min pulling rate, and 5 hz data acquisition frequency). the resulting stress-strain curves were analysed using computational methods to calculate yield strength, ultimate strength, fracture elongation, and toughness. toughness was calculated based on the area under the stress-strain curve. table 1: ebw parameters sample welding speed (mm/min) beam current (ma) heat input (j/mm) 11a, 11b 65 295.3 12a, 12b 660.4 60 272.6 13a, 13b 55 249.8 14a, 14b 65 247.6 15a, 15b 787.4 60 228.6 16a, 16b 55 209.6 17a, 17b 65 213.2 18a, 18b 914.4 60 196.8 19a, 19b 55 180.4 figure 5: front and top views of the tensile test sample fabricated as per astm e8 standard l-pbf direction(z’) x y sali et al. (2021): international journal of engineering materials and manufacture, 6(3), 209-224. 215 figure 6: microhardness testing across a typical weld 4 results and discussion 4.1 weld geometry electron beam penetrated deep in all specimens and provided excellent weld penetration depths as seen in fig. 7. the weld cross-section had a typical nail-shape: the top of the weld had a wide ‘nail-head’ shape which gradually reduced in width to a ‘nail-tip’ shape at the bottom. longer exposure of the beam, larger effective diameter of the electron beam, and low thermal gradients led to a larger melt pool at the top, therefore, its larger width. such nailshape was consistent within all the welded samples. similar published results were found for electron beam welding of rolled in718 [10], [12], [15]. the l-pbf base metal revealed the presence of defects such as gas-filled spherical pores, and irregularly shaped voids on their surface concentrated on the boundaries of the printed samples. these defects included: partially melted powder particles, shrinkage cavity of the molten pool on scanning surface, denudation of adjacent un-melted particles by the molten metal, scattered spatters along a scanning path, entrapment of environmental gas bubbles within the molten pool, etc. similar defects were also reported for l-pbf metals [22]. when welding at heat inputs larger than 247.6j/mm, root voids were observed (fig. 8) at the bottom of the weld in sample 13a (249.8j/mm). the high energy electron beam led to the violent melting and turbulent flow of the molten metal along its path and formed a crater with molten metal flowing upwards around the beam boundary. as the beam moved forward, the molten metal collapsed and solidified with a void at the weld-bottom that could not be filled owing to the fast cooling of the narrow strip of molten metal. voids and spherical pores were also observed at the top of the weld on the interface of the weld zone and the base metal in some l-pbf samples as shown with sample 12a (272.6j/mm) in fig. 8, and sample 17a (213.2j/mm) in fig. 7. due to the violent melting of metal powder during ebw process, the inert gas trapped in the pores or the voids of the base metal was released in the molten metal. due to the heat of the molten metal, the released gas expanded or coalesced to form larger bubbles in the molten metal pool. the hot and low viscosity of molten metal inside the weld allows liquid metal to fill any shrinkage cavity and void; however, liquid metal with low viscosity of at the cooler junctions with parent material cannot fill the cavities, therefore, forming voids near the heat affected zones. these defects were not observed on the replicate of the sample, thereby, indicating their origin during the l-pbf process and not particularly during the ebw process. a linear dependency of the weld penetration depth on the heat input is observed in fig. 9. the overall weld area also increases with increasing electron beam current and decreasing of welding speed as seen in fig. 10. as the beam voltage was constant at 50kv, the weld area also increased with an increase in the heat input. a slower beam speed, higher beam current, and eventually the higher heat inputs allowed longer interaction time between the beam and the material, forming a larger molten volume, deeper weld penetration, and weld area. similar trends were concluded for ebw of rolled in718 materials in other published articles [13], [15], [23], [24]. however, an opposite trend was reported for ebw of alsi10mg. the authors in this study concluded that a higher welding speed (lower heat input per equation (1)) would result in deeper weld penetration [21]. electron beam welding of laser powder bed fused inconel 718 216 figure 7: typical nail-shape of weld profiles in samples (a) 11a (295j/mm), (b) 17a (213.2j/mm), and (c) 19a(180.4j/mm) figure 8: (a) porosity in the nail head region at the top of the weld of sample 12a (272.6j/mm), (b) root void in the weld of sample 13a (249.8j/mm) figure 9: linear increase in penetration depth with heat input 7 8 9 10 11 12 175 195 215 235 255 275 295 p e n e tr a ti o n d e p th ( m m ) e-beam heat input (j/mm) sali et al. (2021): international journal of engineering materials and manufacture, 6(3), 209-224. 217 figure 10: variation in weld area with beam current at various welding speeds 4.2 microhardness the typical microhardness result is shown in fig. 11 where the origin of the coordinate system xy is located at the top of the weld zone as indicated in fig. 6. the dotted lines in fig. 11 indicate the weld zone width at the respective weld depth. the results show: ─ the top of the weld was softer than the weld zone below for all samples. the nail-head zone, where the beam interacted with metal for a long time, contained larger grains, therefore, was softer than the material below it. a similar trend was observed for ebw of rolled in718 samples [14]. ─ the weld zone was softer than the base metal. this was due to the rapid heating and cooling of the molten weld pool leading to a formation of inter-crystalline delta phases in the grain boundaries and having lesser strengthening phases and resulting in the reduction of the hardness in the fusion zone. the preferential grain structure in the rolled samples was disturbed due to the re-melting of the material during the welding process leading to the reduction in the hardness of these samples [14]. ─ similar hardness trends were observed for samples welded at different heat inputs. figure 11: microhardness test results of sample 19a/b (180.4j/mm) 4.3 tensile properties the results of this research represent tensile properties for an ideal case when the full-penetration joint of two workpieces was precisely machined to make a tensile specimen without any misalignment. fig. 12 represents a typical stress-strain curve for samples 19, 20, and their replicates. all tensile twin pairs have similar trends with reasonable repeatability. the tensile properties derived from the stress-strain curves of all samples are presented in table 2. figures 15-17 summarize the mechanical properties of all samples welded at different heat inputs, and compare them against the astm f3055-14a specifications for am in718. 9 11 13 15 50 55 60 65 70 w e ld a re a ( m m 2 ) beam current (ma) 660.4 mm/min 787.4 mm/min 914.4 mm/min electron beam welding of laser powder bed fused inconel 718 218 figure 12: typical stress-strain curves for ebw’ed samples 19a/b (180.4j/mm) and as-printed sample 20a/b. a slight horizontal shift (0.01 cumulative) of the data for samples 19a, 20a, and 20b was intentionally performed to avoid overlapping of the curves figure 13: effect of heat input on the yield strength of the ebw’ed samples figure 14: effect of heat input on uts of the ebw’ed samples figure 15: effect of heat input on the elongation of the ebw’ed samples 0 100 200 300 400 500 600 700 800 900 1000 1100 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 s tr e ss ( m p a ) strain 19a (l-pbf+ebw) 19b (l-pbf+ebw) 20a (l-pbf as-printed) 20b (l-pbf as-printed) 500 600 700 800 900 1000 1100 1200 170 190 210 230 250 270 290 310 y ie ld s tr e n g th ( m p a ) e-beam heat input (j/mm) l-pbf+ebw l-pbf as-printed astm f3055 − 14a,l-pbf in718 sy= 600 mpa 700 800 900 1000 1100 1200 1300 170 190 210 230 250 270 290 310 u lt im a te t e n si le s tr e n g th (m p a ) e-beam heat input (j/mm) l-pbf+ebw l-pbf as-printed astm f3055-14a, l-pbf in718 su= 920 mpa 10 15 20 25 30 35 170 190 210 230 250 270 290 310 e lo n g a ti o n ( % ) e-beam heat input (j/mm) l-pbf+ebw l-pbf as-printed astm b670-07, rolled in718 sy = 1034 mpa astm b670-07, rolled in718 su= 1241 mpa astm b670-07, rolled in718 %εf = 12% astm f3055-14a, l-pbf in718 %εf = 27% sali et al. (2021): international journal of engineering materials and manufacture, 6(3), 209-224. 219 the data from figs. 13-15 suggest that: ─ the measured yield strengths of all samples exceeded the astm specification for acceptable yield strength (600mpa) and the maximum yield strength of ebw of rolled in718 from the previous study (571mpa)[15] ─ for ultimate tensile strength, at least one replicate of each sample exceeded the astm specification of the acceptable tensile strength (920mpa) except for samples 18a/b (196.8 j/mm). the tensile strengths of l-pbf and ebw samples exceeded those of their rolled counterparts at each corresponding welding parameter [15]. ─ although excellent yield and tensile strengths were obtained, the ebw samples were brittle and could not meet the ductility specification. however, the as-printed l-pbf samples 20a/b did meet the minimum astm specification (27%). both sample types exceeded the astm b670-07 ductility requirements for rolled in718. this was also verified by the higher toughness of the as-printed samples compared to the rest (table 2). the ebw of rolled in718 plates had better ductility (66% max elongation) as compared to the l-pbf counterparts due to the absence of inherent l-pbf defects [15]. 4.4 fractography fractured surfaces provided additional information that complements the tensile test results. fig. 16 shows the coordinate system for the tensile specimen. all samples ─ except sample 16a (209.6j/mm) ─ were fractured at their respective weld zone (figs. 17 (a)&(b)). this indicated the brittle nature of the l-pbf samples and their welds. the as-printed sample 20a fractured at a location within the gage length. although the averaged ductility was high (28.1% in table 2), the fractured surface revealed defects induced by the l-pbf process. figure 16: co-ordinate system for tested samples figure 17: (a) sample 16a (209.6 j/mm) with the fractured surface outside of its weld zone; (b) sample 18b (196.8 j/mm) with the fractured surface inside of its weld (a) (b) electron beam welding of laser powder bed fused inconel 718 220 referring to fig. 18, some un-melted in718 powder particles were observed indicating a need for further optimization of the l-pbf parameters. these un-melted particles acted as weak spots and stress raisers in the material matrix and degraded the mechanical properties. large fractured laves phases were also seen in a ductile matrix. the sample 16a (209.6j/mm) fractured outside the weld with low ductility (15.8% in table 2) due to the presence of multiple defects: porosity on the surface of the sample which could have been inherited from the l-pbf process (fig. 19a), and large brittlely fractured phases (fig. 19 b). those brittle phases were identified as nbc from the eds analysis (figs. 20a, b). table 2: mechanical properties of ebw'ed samples sample label heat input (j/mm) ys (mpa) uts (mpa) young’s modulus (gpa) elongation (%) toughness (j/mm 3 x 10 -3 ) 11a/b 295.3 720, 722 937, 998 10.9, 10.5 16.9, 22.5 102, 155 12 a/b 272.6 715, 724 925, 987 11.0, 10.5 17.0, 20.6 98, 143 13 a/b 249.8 722, 703 951, 1004 10.8, 10.4 19.1, 22.3 117, 161 14 a/b 247.6 714, 724 899, 967 10.9, 10.7 15.1, 18.2 85, 102 15 a/b 228.6 737, 706 976, 932 10.9, 10.6 19.5, 16.8 125, 103 16 a/b 209.6 724, 709 889, 931 10.7, 11.6 15.8, 16.4 87, 102 17 a/b 213.2 719, 712 927, 899 10.9, 10.8 18.8, 13.4 125, 75 18 a/b 196.8 702, 708 891, 888 10.7, 11.2 16.5, 14 88, 77 19 a/b 180.4 735, 710 1004, 953 10.9, 11.1 22.7, 17.5 159, 110 20 a/b --- 741, 745 1045, 1024 10.8, 10.9 28.1, 27.7 210, 198 figure 18: sem fractography of sample 20a (as-printed l-pbf); (a, b): un-melted powder particles (label 1 & 3), unfilled zone (label 2); (c) & (d) brittle laves zones (label 4) sali et al. (2021): international journal of engineering materials and manufacture, 6(3), 209-224. 221 fig. 21 (a) shows a smooth and flat surface indicating a disjointed l-pbf layer formed due to inadequate adhesion between adjacent layers on the ebw sample 17b (213.2j/mm). subsequent eds analysis confirmed the same elements and compositions of this layer and the surrounding matrix. few spherical particles surrounded by a more ductile surface were also observed on the fractured surface of sample 17b (fig. 21b). as this spherical particle was not melted and did not have any bond with the surrounding matrix, it was suspected that it could not be an in718 powder but a possible contaminated powder or being a different material. an eds analysis indicated the presence of a large percentage of aluminium (35.6-37.7%) and oxygen (49-51.4%) followed by titanium (7.3-9.6%) at certain sites (fig. 22) as compared to the surrounding matrix (0% oxygen, 0.6% aluminium, and 1% titanium). figure 19: sem fractography of ebw’ed sample 16a (209.6 j/mm) that fractured in the base metal; (a) spherical pores (label 1) and (b) brittle carbide phases (label 2) (a) (b) figure 20: (a) fractured surface of sample 16a (209.6 j/mm), and (b) eds analysis at different locations showing high carbon content ni cr fe nb al c ti o a 50.1 20.9 16.4 1.1 0.6 7.6 1.4 1.9 b 29 10.6 9.6 7.2 0.4 33 0.8 7.1 c 20 18 13.5 0 3.2 35.6 0 9.7 d 42 25.7 16.2 0 0 13.8 0 2.3 e 5.3 13.7 1.7 2.3 0 59.6 0 13 f 11.5 33.8 3.8 3.1 0 39.4 0 5.8 0 20 40 60 80 c o m p o si ti o n % element a b c d e f electron beam welding of laser powder bed fused inconel 718 222 a study concluded that such phases were the brittle aluminium oxides al2o3 [25]. however, the resulted aluminium composition in the eds analysis of 35.6-37.7 wt% al was lower than the stoichiometric composition of al2o3 (52.925 wt% al + 47.075 wt% o), it was postulated that the contaminant could be al-ti oxide instead. better control of the l-pbf environment was recommended to prevent the formation of such oxides that adversely affect the mechanical properties of the l-pbf products. both the l-pbf and ebw processes melted and solidified the workpiece metal, thereby, affected the microstructure of the base metal alloy. the rapid melting and cooling and later reheating of in718 promoted the precipitation of solute metallic/ceramic compounds of niobium, carbon, titanium, aluminium with oxygen in the inter-dendritic region. this segregation led to the formation of hard and brittle carbides (such as nbc). all or most percentages of carbon in the alloy were consumed in this process. the higher the percentage of carbon in the base alloy matrix, the higher was the tendency of the carbide formation. this explained the presence of brittle carbides on the fractured surfaces of the l-pbf base metal and welded materials as seen in figs. 18-19. figure 21: (a) unfused l-pbf layer (label 1) and (b) delaminated layer between the spherical contaminant and the material matrix (label 2) on the fractured surface of sample 17b (213.2 j/mm). this sample fractured in the weld zone (a) (b) figure 22: (a) fracture of a brittle spherical particle in the ductile matrix of sample 17b (213.2 j/mm), and (b) eds analysis at different locations showing high aluminium, titanium, and oxygen content ni cr fe nb o al c ti mo ba a 0 2.7 0 0 51.4 35.6 0 7.3 0 3 b 0 3.6 0 0 49 37.7 0 9.6 0 0 c 51.3 14.8 14.4 11 0 0.6 3.3 1 3.6 0 d 38.8 26.5 28.4 0 0 0 6.3 0 0 0 0 20 40 60 c o m p o si ti o n ( % ) elements sali et al. (2021): international journal of engineering materials and manufacture, 6(3), 209-224. 223 further enrichment of the solute led to the formation of the laves phase before the solidification process ended. the formation of such laves phases was directly proportional to the presence of segregated niobium. niobium segregation depended majorly on the cooling rate of the molten alloy. the higher the cooling rate, the lower was the segregation of niobium [7]. thus, favourable material characteristics can be observed at high cooling rates during l-pbf or ebw. niobium present in the alloy solution was shared by various secondary phases (δ, γ, γ’, and γ’’) during solidification. thus, a higher percentage of any of these phases led to a reduction in the percentage of the others. in the case of the weld fusion zone, the percentage of strengthening phase γ’ and γ’’ reduced due to high consumption of nb by the δ and γ phases[7], [14]. further, the formation of laves and δ phase in the grain boundaries provided favourable sites for the nucleation of voids and fissures. due non-uniform size of metal powder and coalescence of recycled powder particles, gaps were formed between the adjacent layers during the l-pbf process. this led to inadequate heat distribution and left some metal particles un-melted. the scanning laser beam induced thermal gradients between adjacent layers, thereby, fusing them and leading to a formation of homogenous metal in an ideal case. uneven layer thickness, fluctuation of laser power, or powder contamination can form gaps between the adjacent layers (fig. 21a). this led to inadequate heat distribution and partially melted powder particles in the materials as seen in figs. 18a-b and 21b. in summary, the brittleness of the l-pbf samples after electron beam welding was due to: ─ partially melted powder particles and unfused layers during the l-pbf process. ─ pores and voids due to trapped gas or solidification shrinkage. ─ carbide and oxide contaminants that fractured brittlely while preventing proper adhesion between adjacent layers. ─ delamination between the l-pbf layers. the above defects were absent in wrought materials, therefore, the ductility of the ebw specimens of rolled in718 is higher compared to that from l-pbf in718. eliminating defects with preor post-processes should improve the ductility of final products. 5 conclusions electron beam joining of powder bed fused in718 specimens was performed at different heat input levels. this study showed that: 1. excellent penetration depth was achieved for ebw of l-pbf in718 without beam oscillations. the penetration depth and weld area were directly proportional to the heat input. 2. nail-shaped fusion zones were seen for all welded samples. the fusion zone was found to be softer as compared to the base metal hardness due to the dissolving of the strengthening γ’ and γ’’ precipitates. 3. all samples welded between 180-295 j/mm heat input either met or exceeded the specified tensile and yield strength from astm f3055-14a, however, the ductility of all the welded samples was below the astm specification due to inherent defected generated by l-pbf and ebw processes. 4. fracture analysis revealed the presence of pores, partially melted powders, delaminated layers, brittle laves phase, and other intermetallic/ceramic compounds. these defects contributed to the brittle nature of the ebw’ed samples. 5. thermal induced defects were seen in both ebw of wrought and l-pbf in718; however, additional defects in the latter materials would further degrade the mechanical properties of the welded specimen. 6 future works remedial steps have been implemented to improve the properties of the weldments. 1. optimizing the l-pbf parameters to minimize defects. 2. improving the ductility of the welds by eliminating voids, laves phase, and other brittle phases with postprocessing heat treatment and hot isostatic pressing. acknowledgement the authors thank mr. rodney inmon (materials testing lab, department of aerospace engineering), mr. tom stephens (microscopy and imaging centre), and dr. angie price (materials lab, mechanical and manufacturing engineering technology) of texas a&m university. support from the kgsbo company is much appreciated. references 1. w. bolen, “certified materials test report,” west virginia, 2019. 2. c. slama and m. abdellaoui, “structural characterization of the aged inconel 718,” j. alloys compd., vol. 306, no. 1–2, pp. 277–284, 2000, doi: 10.1016/s0925-8388(00)00789-1. 3. j. norrish, “high-energy density processes,” in advanced welding processes, j. norrish, ed. elsevier, 2006, pp. 136–164. 4. g. vander voort, “inconel 718 (alloy 718) and modified inconel 718,” 1991. 5. h. l. eiselstein, “stp369-eb/apr. 1965 metallurgy of a columbium hardened nickel chromium iron alloy,” 2020. electron beam welding of laser powder bed fused inconel 718 224 6. g. a. knorovsky, m. j. cieslak, t. j. headley, a. d. romig, and w. f. hammetter, “inconel 718: a solidification diagram,” metall. trans. a, vol. 20, no. 10, pp. 2149–2158, 1989, doi: 10.1007/bf02650300. 7. g. d. janaki ram, a. venugopal reddy, k. prasad rao, and g. madhusudhan reddy, “microstructure and mechanical properties of inconel 718 electron beam welds,” mater. sci. technol., vol. 21, no. 10, pp. 1132– 1138, 2005, doi: 10.1179/174328405x62260. 8. d. deng, r. l. peng, h. brodin, and j. moverare, “microstructure and mechanical properties of inconel 718 produced by selective laser melting: sample orientation dependence and effects of post heat treatments,” mater. sci. eng. a, vol. 713, no. december 2017, pp. 294–306, 2018, doi: 10.1016/j.msea.2017.12.043. 9. j. strößner, m. terock, and u. glatzel, “mechanical and microstructural investigation of nickel-based superalloy in718 manufactured by selective laser melting (slm),” adv. eng. mater., vol. 17, no. 8, pp. 1099– 1105, 2015, doi: 10.1002/adem.201500158. 10. c. a. huang, t. h. wang, c. h. lee, and w. c. han, “a study of the heat-affected zone (haz) of an inconel 718 sheet welded with electron-beam welding (ebw),” mater. sci. eng. a, vol. 398, no. 1–2, pp. 275–281, 2005, doi: 10.1016/j.msea.2005.03.029. 11. g. madhusudhana reddy, c. v. srinivasa murthy, k. srinivasa rao, and k. prasad rao, “improvement of mechanical properties of inconel 718 electron beam welds-influence of welding techniques and postweld heat treatment,” int. j. adv. manuf. technol., vol. 43, no. 7-8, pp. 671–680, 2009,doi: 10.1007/s00170-008-17517. 12. m. agilan, t. venkateswaran, d. sivakumar, and b. pant, “effect of heat input on microstructure and mechanical properties of inconel-718 eb welds,” procedia mater. sci., vol. 5, pp. 656–662, 2014, doi: 10.1016/j.mspro.2014.07.312. 13. y. mei et al., “effect of base metal and welding speed on fusion zone microstructure and haz hot-cracking of electron-beam welded inconel 718,” mater. des., vol. 89, pp. 964–977, 2016, doi: 10.1016/j.matdes.2015.10.082. 14. p. gao, k. f. zhang, b. g. zhang, s. s. jiang, and b. w. zhang, “microstructures and high temperature mechanical properties of electron beam welded inconel 718 superalloy thick plate,” trans. nonferrous met. soc. china (english ed., vol. 21, no. suppl. 2, pp. s315–s322, 2011, doi: 10.1016/s1003-6326(11)61598-7. 15. v. patel, a. sali, j. hyder, m. corliss, d. hyder, and w. hung, “electron beam welding of inconel 718 electron beam welding of inconel 718,” in procedia manufacturing, 2020, vol. 48, no. 2019, pp. 428–435, doi: 10.1016/j.promfg.2020.05.065. 16. j. huang, “the characterisation and modelling of porosity formation in electron beam welded titanium alloys,” computer (long. beach. calif)., no. september, p. 207, 2011. 17. j. kar, d. chakrabarti, s. k. roy, and g. g. roy, “beam oscillation, porosity formation and fatigue properties of electron beam welded ti-6al-4v alloy,” j. mater. process. technol., vol. 266, no. june 2018, pp. 165–172, 2019, doi: 10.1016/j.jmatprotec.2018.10.040. 18. y. arata, k. terai, and s. matsuda, “characteristics of a weld defect and its prevention in electron beam welding. pt. 1. characteristics of weld porosities,” trans. jwri, no. report i, 1973. 19. t. raza, j. andersson, and l. e. svensson, “varestraint weldability testing of additive manufactured alloy 718,” sci. technol. weld. join., vol. 23, no. 7, pp. 606–611, 2018, doi: 10.1080/13621718.2018.1437338. 20. c. xia, m. zhao, w. sun, h. li, and p. liu, “microstructure and properties of 3d printed inconel 718 joint brazed with bni-2 amorphous filler metal,” mater. res., vol. 22, no. 1, pp. 1–10, 2018, doi: 10.1590/19805373-mr-2018-0348. 21. m. nahmany, i. rosenthal, i. benishti, n. frage, and a. stern, “electron beam welding of alsi10mg workpieces produced by selected laser melting additive manufacturing technology,” addit. manuf., vol. 8, pp. 63–70, 2015, doi: 10.1016/j.addma.2015.08.002. 22. s. a. khairallah, a. t. anderson, a. rubenchik, and w. e. king, “laser powder-bed fusion additive manufacturing: physics of complex melt flow and formation mechanisms of pores, spatter, and denudation zones,” acta mater., vol. 108, pp. 36–45, apr. 2016, doi: 10.1016/j.actamat.2016.02.014. 23. m. thomas, p. saha, g. namboothiri, g. radhakrishnan, and s. srivastava, “effect of process parameters on weld bead geometry and element segregation in electron beam welding of inconel 718,” pp. 717–722, 2017. 24. a. m. saeed, m. sobih, a. m. youeesf, and a.-m. ei-batahgy, “experimental investigation of laser and electron beam welding of inconel 718,” no. november 2015, 2016. 25. v. a. popovich, e. v. borisov, a. a. popovich, v. s. sufiiarov, d. v. masaylo, and l. alzina, “impact of heat treatment on mechanical behaviour of inconel 718 processed with tailored microstructure by selective laser melting,” mater. des., vol. 131, no. january, pp. 12–22, 2017, doi: 10.1016/j.matdes.2017.05.065. international journal of engineering materials and manufacture (2017) 2(4) 67-85 https://doi.org/10.26776/ijemm.02.04.2017.01 z. feng1, j. m. orona-hinojos2, p. perez-villanueva2, p. lomeli3, and w.n.p. hung1 1texas a&m university, ms 3367, college station, texas 77843, usa 2advanced material research comimsa, coahuila, mexico 3keysight technologies, santa rosa, california, usa e-mail: hung@tamu.edu reference: feng, z., orona-hinojos, j. m., perez-villanueva, p., lomeli, p., and hung, w. n. p. (2017). flushing enhancement with vibration and pulsed current in electrochemical machining. international journal of engineering materials and manufacture, 2(4), 67-85. flushing enhancement with vibration and pulsed current in electrochemical machining zhujian feng1, jesus manuel orona-hinojos2, pedro perez-villanueva2, paul lomeli3, and wayne nguyen hung1 abstract this research aims to understand the flushing of by-products in electrochemical machining (ecm) by modeling and experimentally verifying mechanism of particle transport in inter-electrode gap under low frequency vibration. a series of hole were drilled on steel plates to evaluate the effect of vibration on material removal rate and hole quality. infinite focus optical technique was used to capture and analyze the three-dimensional images of ecm'ed features. experimental results showed that maximum machining depth and minimum taper angle can be achieved when vibrating the workpiece at 40 hz and 10 µm amplitude. simulation results showed that the highest average flushing speed of 0.4 m/s was obtained at this vibration frequency and amplitude. machining depth and material removal rate had a positive correlation with the average flushing speed. sharper ecm’ed profile is obtained since the taper angle is favorably reduced at high average flushing speed. keywords: electrochemical machining, low frequency vibration, pulsed current. nomenclature a electrode area (mm2) a0 initial gap between particle center and workpiece (µm) av vibration amplitude (µm) b constant equals to avf2 c specific removal rate of workpiece (mm3/a/s) cbn cubic boron nitride d workpiece density (g/cm3) dg gap between particle center and workpiece d1, d2 hole diameters at levels 1, 2 (mm) dc direct current e applied voltage (v) ecm electro-chemical machining edm electro-discharging machining f vibration frequency (hz) f faraday constant=96500 coulomb/mole fb buoyance force (n) fd drag force (n) fr total force along radial direction (n) g inter-electrode gape (mm) g gravity force (n) h height between level 1 and level 2 (mm) hsla high strength low alloy i current in ecm operation (a) received: 16 july 2017 accepted: 02 october 2017 published: 10 december 2017 publisher: deer hill publications © 2017 the author(s) creative commons: cc by 4.0 flushing enhancement with vibration and pulsed current in electrochemical machining 68 ivibration current to drive the vibration table (a) ieg inter-electrode gap (mm) m molecular mass of anodic workpiece (g/mole) mrr material removal rate (mm3/min) r resistivity of electrolyte (ω mm) 𝛿𝛿 conicity (%) t machining time (s) v removed volume (mm3) vave average flushing speed (m/s) z valence electron of anode 1 introduction the emphasis on fuel economy and passenger safety have led to a remarkable increase in the usage of high strength low alloy (hsla) steels in automobile application due to their high strength-to-weight ratio, and higher fatigue resistance than carbon steel. engineering components using hsla steels usually have complex geometries and are manufactured by various metal forming techniques. fabrication of holes and slots on hsla steel, for example, is a common work procedure when designing engineering components. drilling, milling, punching, laser cutting and electro-discharging machining (edm) are general processes that applied to shape a component. however, microstructural damages, expensive deburring and time consuming residual stress relieving treatment prompt researchers to consider alternative manufacturing techniques. cubic boron nitride (cbn) and coated carbide tools are required when machining hsla steels due to its high strength and poor machinability. high energy is required to shear the chips which results in thermal-induced defects in the materials and costly tool wear. when punching/stamping hsla steels, it requires high energy, very tough yet hard cutting tool material, high stiffness of tool holder, are pre-requisites for successful punching holes on hsla steels due to work-hardening property of hsla steels. although laser cutting has the advantages of no mechanical cutting forces and tool wear; its high energy-consumption, low mrr, tapering cutting profile, thermally induced residual stress on laser cut surfaces are inherent drawbacks of this process. in the edm process a conductive material can be removed without mechanical contact forces and independent of material hardness. although edm can be used to form features on hsla steels, but a defective edm'ed subsurface and relatively slow mrr limit the application of edm for demanding and high volume applications. a recast layer after edm'ing is under high residual stress and may contain voids and microcracks; heat affected zone beneath recast layer undergoes microstructure morphing; insufficient flushing leads to abnormal discharging and resulting in extensive electrode wear. in all traditional and nontraditional processes, inevitable burrs are formed and must be removed in subsequent operations that further drives up the lead time and manufacturing cost. electrochemical machining has been applied in aerospace, automobile, medical, and, recently, in micro manufacturing. this technique, based on the principle of controlled atomic-level anodic dissolution, has been used to fabricate complex shapes from any electrically conductive components. this is particularly useful to shape engineering alloys that are difficult to be machined such as hsla steels, tool steels, tungsten carbides and super alloys. moreover, ecm does not induce any thermal or mechanical stresses/surface effects on the workpiece, the process generates no burr, has no tool wear, yet can achieve excellent surface quality as in electrochemical polishing. eliminating secondary processes for deburring and stress relieving, the ecm is a promising technique to machine/polish hsla steels if a decent material removal rate can be achieved. ion transport movement is the basic mechanism that controls the material removal rate in ecm. when two electrically conductive materials are closely placed in the presence of an electrolytic fluid that conducts ions, the anodic workpiece releases ions towards the cathodic electrode. if the cathodic electrode (tool) moves at a controlled feed rate and motion toward anode, a desirable shape can be formed on the anodic workpiece. an electrolyte flows between two electrodes to enhance ion transport, maintain the temperature, and flush the resulted debris. if the newly formed by-products in inter-electrode gap (ieg) are not effectively flushed away from an anode surface, cumulative ions would be stagnant and inhibits further ion dissolution, therefore, affecting material removal rate (mrr) and quality of ecm’ed profile. thus, increase the ion transport rate and effective flushing of by-products are keys to improve the material removal rate. the movement of ions is controlled by three processes [1]: i) migration, i.e. movement under the influence of the electric field; ii) diffusion, i.e. movement due to ion concentration gradients in the solution; iii) convection, i.e. bodily movement of the electrolyte solution; this is mainly effected by force agitation of the electrolyte in ecm. therefore, a high mrr requires fast ion and by-product movement rates (i.e. migration rate, diffusion rate and convection rate). researchers have attempted to utilize different techniques to improve these transport rates: by applying a high voltage to increase migration rate, increasing high electrolyte flow rate to increase diffusion rate, vibrating either workpiece or electrode to increase mrr. a study of by-product flushing in ecm to enhance the mrr with pulsed current and low frequency workpiece vibration is the focus of this research. feng et al., (2017): international journal of engineering materials and manufacture, 2(4), 67-85 69 2 literature review 2.1 electrolysis since the major composition of hsla steel is iron (97-99%), during ecm process several possible reactions may occur at the workpiece and electrode. the reaction is the dissolution of iron at anode. 𝐹𝐹𝐹𝐹 → 𝐹𝐹𝐹𝐹2+ + 2𝐹𝐹− (1) at the electrode, hydrogen and hydroxyl ions are produced: 2𝐻𝐻2𝑂𝑂 + 2𝐹𝐹− → 𝐻𝐻2 ↑ +2𝑂𝑂𝐻𝐻− (2) thus, the overall reaction of iron in ecm process is: 𝐹𝐹𝐹𝐹 + 2𝐻𝐻2𝑂𝑂 → 𝐹𝐹𝐹𝐹(𝑂𝑂𝐻𝐻)2 + 𝐻𝐻2 ↑ (3) ferrous hydroxide fe(oh)2 may further react with water and oxygen to form ferric hydroxide fe(oh)3. 𝐹𝐹𝐹𝐹(𝑂𝑂𝐻𝐻)2 + 2𝐻𝐻2𝑂𝑂 + 𝑂𝑂2 → 4𝐹𝐹𝐹𝐹(𝑂𝑂𝐻𝐻)3 (4) the iron dissolution rate (material removal rate) is governed by faraday’s two laws of electrolysis: i) the amount of any substance dissolved or deposited is directly proportional to the amount of electrical charges which has flowed; ii) the amounts of different substances deposited or dissolved by the same quantity of electrical charges are proportional to their chemical equivalent weights. the two laws may be combined to give the equation: 𝑀𝑀𝑀𝑀𝑀𝑀 = 𝑉𝑉 𝑡𝑡 = � 𝑀𝑀 𝑧𝑧𝐹𝐹𝑧𝑧 � 𝐸𝐸𝐸𝐸 𝑔𝑔𝑔𝑔 = 𝐶𝐶 𝐸𝐸𝐸𝐸 𝑔𝑔𝑔𝑔 (5) where; mrr = material removal rate (mm3/s), v = removed volume (mm3), m = molecular mass of anodic workpiece (g/mole), d = workpiece density (g/cm3), e = applied voltage (v), a = effective electrode area (mm2), 𝑔𝑔 = inter-electrode gap (mm), r = resistivity of electrolyte (ω mm), z = valence electron of anode, t = machining time (s), f = faraday constant = 96500 coulomb/mole, and c: specific removal rate of workpiece (mm3/a/s). although equation (5) suggests the mrr is the volume removal rate, some researchers change it to mass removal rate for the convenience of measurement. 2.2 effect of higher voltage the original faraday’s work used direct current for electrolytic plating; it assumed the anodic ion removal rate is the same as the rate for ion depositing on cathode and chemical replenishing rate. from equation (5), a higher applied voltage would result in a higher mrr. ecm using copper electrode with square cross section, 𝜙𝜙20 × 40 mm high carbon alloy steel workpiece, 10% nacl electrolyte with 6 m/s flow rate and 0.2 mm ieg was investigated [3]. when the applied voltage increased from 24v to 32v, the resulted mrr increased 15% from 2.575 mg/min to 2.960 mg/min. similarly, other researchers [4] used copper electrode with square cross section, 𝜙𝜙30 × 6 mm alloy steel workpiece, 20 g/l nano3 electrolyte with 7 l/min electrolyte flow rate and 0.6 mm/min electrode feed rate. when the applied voltage increased from 12 v to 16 v, the authors found that mrr increased 23% from 0.0514 g/min to 0.0634 g/min. the trend was also reconfirmed by other authors [5] who used 𝜙𝜙16 mm solid brass electrode, 𝜙𝜙19 mm en-8 steel workpiece, 45 g/l nacl with 12 l/min electrolyte flow rate and 0.8 mm ieg. when the applied voltage increased from 10 v to 30 v, the mrr increased a significant 204% from 0.33445 g/min to 1.01855 g/min. it has been experimentally verified that mrr increases with applied voltage or current. on an active material that forms a passive film on its surface, a higher current would breakdown the passivated film and facilitate the electrochemical reaction between electrodes [6]. in addition, a higher voltage facilitates the migrating rate which also enhances mrr due to accelerating ion transport. 2.3 effect of pulsed current in a conventional electrochemical machining, a dc power is generally applied, and the electrolyte between interelectrode gap is easily boiled due to the energy dissipation of high current density, which results in a varying local distribution of electrolyte conductivity and hence leads to poor machining accuracy. a higher voltage/current also results in more undesired products and heat which require a higher electrolyte flow rate to remove. pulsed current, flushing enhancement with vibration and pulsed current in electrochemical machining 70 instead of direct current, has been applied in ecm to enhance the process. pulsed ecm leads to higher dimension accuracy, better surface quality, better process stability, and suitability to online process control. these benefits are obtainable due to several factors [7]: i) enhancing localized anodic dissolution, ii) improving electrolyte hydrodynamic uniformity in the ieg by removing undesired by-products and reducing heat during off-time, iii) reducing and stabilizing ieg, and iv) reducing required electrolyte flow rate. when applying pulsed voltage in ecm, the combination of peaked voltage, duty cycle and voltage frequency exert influence on mrr and dimension accuracy. ecm using 𝜙𝜙9.5 mm stainless steel electrodes with teflon coated on both outside and inside, 60 mm × 40 mm × 6.3 mm 1018 steel workpiece, 1 mol/l kbr electrolyte, 13 a average current was studied [8]. when the current frequency was switched from 0 to 60 hz, the mrr increased slightly from 34.3 to 34.9 mm3/min, but when increasing the current frequency to 100 hz, the mrr then increased to 36.4 mm3/min. other authors used 𝜙𝜙200 µm platinum wire electrode, 6 mm × 4 mm × 0.4mm copper plate workpiece, 15 g/l nano3 electrolyte, 10 v peak voltage and 50 hz voltage frequency. when the duty cycle increased from 25% to 75%, the mrr increased 500% from 0.2 mg/min to 1.2 mg/min but the overcut also increased from 0.04 mm to 0.07 mm [9]. some researchers [10] used 𝜙𝜙335 µm stainless wire electrode, 15 mm × 10 mm × 0.15 mm bare copper workpiece, 20 g/l nano3 electrolyte and 3.5 v peak voltage. for a specific value voltage frequency, i.e. at 35 hz, mrr initially increased with an increase of duty cycle to the maximum value, but the mrr then decreased with further increasing in duty cycle at a preset machining parameters. the paper cited that the mrr increased with an increase of duty cycle due to more machining time. with further increased in duty cycle, the mrr decreased in small span of off time due to inefficient removing of by-products from the machining zone that led to improper dissolution of workpiece material. in addition, radial over cut increased with increasing duty cycle. since by-products were inefficiently flushed away from machining zone during shorter off-time (i.e. higher duty cycle), the presence of by-product microparticles between electrodes would increase the chance of micro-sparking when high voltage applied and hence increased the radial over cut. moreover, localized effect diminished with an increasing in duty cycle. for a specific duty cycle, i.e. 60%, when voltage frequency increased from 35 to 55 hz, the mrr increased 12% from 0.821948 to 0.91998 g/min and the radial overcut increased from 0.161 to 0.203 mm. 2.4 effect of electrolyte flow rate diffusion rate is another major factor that affects the ion transport. although an electrolyte can be static in theory, it is commonly pumped at high flow rate to flush away by-products, reduce electrolyte temperature and replenish fresh electrolyte in ieg. ecm with copper electrode with square cross section, 𝜙𝜙30 × 6mm alloy steel workpiece, 20 g/l nano3 electrolyte, 0.6 mm/min electrode feed rate and 14 v applied voltage was investigated [11]. when the flow rate increased from 5 l/min to 9 l/min, the mrr increased 98% from 0.0242 to 0.0478 g/min, and the surface roughness reduced from 3.241 to 2.785 µm. other authors [5] used 𝜙𝜙16 mm solid brass electrode, 𝜙𝜙19mm en-8 steel workpiece, 45 g/l nacl electrolyte, 20 v applied voltage and 0.8mm ieg. when the electrolyte flow rate increased from 10 to 14 l/min, mrr increased 52% from 0.5526 to 0.84095 g/min and overcut is reduced from 0.275 to 0.25 mm. however, a high electrolyte flow rate requires an elaborate pumping system and a heavy machine frame to maintain rigidity. a very high flow rate may introduce two drawbacks: i) non-uniform electrolyte hydrodynamic condition in the ieg result in poor machining dimensional accuracy and ii) cavitation results in poor surface quality. 2.5 effect of ultrasonic vibration in addition to low frequency vibration of workpiece or electrode, some researchers explored the effect of ultrasonic vibration on ecm process. some authors [12] used brass electrode, nc6 steel workpiece, 20-120 w ultrasonic vibration power with 10 µm maximum vibration amplitude at 20 khz. they found a slight improvement in surface finish 𝑀𝑀𝑎𝑎 from 1.5 µm to 1.0 µm, and concluded that specific ultrasonic amplitude for each combination of machining parameters would result in an optimal surface finish. instead of applied ultrasonic vibration on electrode or workpiece, some researchers set up an ecm cell in ultrasonic baths at either 20 khz or 56 khz [13]. the effect of ultrasonic wave was expected by the transmission of high frequency wave through the glass walls of the electrochemical cell. using 10 a current and changing vibration frequencies from 0 to 20 khz, the authors found the mrr increased slightly from 0.194 g/min to 0.197 g/min. when increasing vibration frequency to 50 khz, the mrr increased to 0.207 g/min. the study concluded that insignificant improvement was due to the ineffective transmission of ultrasonic wave through glass wall into the ieg gap of ecm cell. other researchers [14] used ultrasonic probe to send 20 khz ultrasonic wave to workpiece surface via flowing electrolyte. the authors used 6061-t6 aluminum workpieces of 60 mm × 50 mm × 6.3 mm, teflon coated stainless steel tubular electrode with 𝜙𝜙9.5 mm outer diameter and 𝜙𝜙8.9 mm inner diameter, 1 mol/l kbr electrolyte, 22 a feng et al., (2017): international journal of engineering materials and manufacture, 2(4), 67-85 71 peak current. when applying 275 hz current frequency and increasing ultrasonic amplitudes from 0 to 15 µm, the authors found improvement of surface roughness ra from 2.5 to 1.1 µm but at the expense of mrr. the generation and implosion of microbubbles due to cavitation at workpiece surface interfered with ionization mechanism at anode, they concluded. 2.6 effect of low frequency mechanical vibration convection is the most significant factor that affects ion transport mechanism. to improve the convection rate, researchers have attempted to vibrate either electrode or workpiece at different vibration frequency and amplitude to enhance the process. low-frequency vibration of either anode (workpiece) or cathode (electrode) cyclically alters the ieg to enhance flushing of debris while refreshing the anode surface with new electrolyte. assuming perfect synchronization of pulsed current and workpiece vibration, a single vibration cycle can be divided into two individual movements: a downward movement (that reduces ieg) and an upward movement (that increases ieg). a smaller ieg reduces the system resistance, increases the current passing through the electrode, and removes more material from the anode by ionization. on the other hand, a large ieg enhances flushing conditions of by-products and helps to bring in fresh electrolyte for the next cycle. some researchers [15] pointed out that longitudinal vibration in ecm enhanced the circulation of electrolyte. at the maximum ieg, the decreased pressure in ieg generates transient cavitation or micro bubbles of electrolyte vapor. during the next half vibration cycle, the tool moved toward to workpiece. while in the minimum ieg, pressure inside the ieg increased and micro bubbles collapses rapidly. this phenomenon generated electrolyte turbulence which drives out reaction products from the machining zone. fresh electrolyte was forced in ieg when tool moves away from the workpiece in the next oscillate cycle. other investigators [16] used brass tube electrode with 𝜙𝜙8mm outer diameter and 𝜙𝜙3.5mm inner diameter, 20 g/l nacl electrolyte, 6 l/min electrolyte flow rate, 1 mm/min electrode feed rate, 18 v applied voltage and 50 hz voltage frequency. the electrode was externally insulated with a thin layer using epoxy resin to avoid undesired side cutting. experimental results illustrated that significant effect of the tool vibration amplitude on the overcut value was pronounced at the lowest tool amplitude values (20 µm peak-to-peak). the value of the overcut decreased with a ratio of 15% at tool amplitude of 20 µm (peak-to-peak) more than that with zero tool amplitude. the result was due to the fact that a higher tool amplitude value caused a greater stray current during the tool motion, which led to an increase of mrr on the side of workpiece. conicity is defined as: 𝛿𝛿 = 𝐷𝐷1 − 𝐷𝐷2 2𝐻𝐻 × 100 (6) where; 𝛿𝛿 = conicity (%), d1 = hole diameter at level 1 (mm), d2 = hole diameter at level 2 (mm), and h = height between the two level (mm). the conicity decreased with increasing vibration amplitude. the application of low-frequency vibration to the ecm tool reduced workpiece conicity with a ratio about 23% (4.5%-3.5%) than that without vibration. this effect was due to the effectiveness of the pumping action at the frontal zone, intense flushing of the ieg with fresh electrolyte and evacuation of the by-products, which resulted in the decrease of lateral material removal and conicity improvement. other authors [10] used 𝜙𝜙335 µm stainless steel wire electrode, 10 mm×10 mm× 0.15 mm bare copper workpiece, 20 g/l nano3 electrolyte, 3.5 v applied voltage, 45 hz voltage frequency and 60% voltage duty cycle. when the vibration frequency increased from 100 hz to 300 hz, the resulted mrr increased 10% from 0.89469 g/min to 0.98655 g/min. the authors concluded that at higher vibration frequency, the mrr increased from the consequence of proper dissolution of anode material and greater amount of reaction material being flushed away from ieg. others [2] used 𝜙𝜙160 µm tungsten electrode with 5 µm insulate layer, 321 stainless steel workpiece with 0.5 mm thickness, 5wt% nano3+0.8wt% edta-na2 electrolyte, 6 v voltage with 50% duty cycle, 2 khz pulsed voltage and 15.6 µm ieg, 3-14 µm vibration amplitude, and 50-200 hz vibration frequency. these authors applied low frequency vibration on the workpiece instead of electrode, pointed out that a low frequency vibration would help the overall process efficiency by: i) ejecting reaction products away from the electrode faces, and ii) maintaining a stable electrolyte field within ieg, therefore enhancing mrr. at a low vibration frequency of 50 hz, the mrr increased about 5 times to 0.0388 mg/min (when vibration at 12 µm amplitude) from 0.0062 mg/min (without vibration). a peak value of mrr existed at certain amplitude for each vibration frequency, i.e., at 50 hz, 12 µm vibration amplitude generated maximum mrr. on the contrary, at higher vibration frequency of 200 hz, the vibration amplitude had negligible influence on mrr: 0.0066 mg/min at 8 µm vibration amplitude, compared with 0.0062 mg/min without vibration. at constant vibration amplitude, the mrr initially increased then decreased with increasing vibration frequency. for a preset vibration amplitude (4 , 6, and 8 µm), the resulted mrr initially increased as vibration increased, but after obtaining the maximum mrr at 50 hz, then mrr decreased with increasing of vibration frequency. flushing enhancement with vibration and pulsed current in electrochemical machining 72 effect of large range vibration frequency was also studied [17]. the authors used stainless steel electrode, 15 mm ×10 mm × 0.15 mm bare copper plate workpiece, 20 g/l sodium nitrate electrolyte, 3 v voltage, 55 hz voltage frequency, 66% duty cycle and 0.144 mm/min electrode feed rate. a wide range of frequency 50-23,000 hz was selected for electrode vibration. vibration amplitude was 4.5 v-rms. experimental results showed that electrode vibration at khz ranges had no significant influence on mrr (~0.6 mg/min) and overcut (~0.1 mm). however, at lower ranges of electrode vibration, a higher mrr (~1.75 mg/min) and lower overcut (0.04 mm) were obtained. the enhanced mrr and dimension accuracy attributed to the introduction of electrode tool vibration in hz range during ecm process which eliminated the passive layer from the effective machining area of workpiece surface, and thereby improved the ecm actions. to continue improve mrr in vibration-assisted ecm, synchronization of mechanical vibration with pulsed current was introduced. during this process, the electrode feeding toward the anode was overlaid with cathode vibration, which results in two different process phases. during minimize gaps size, a pulse current with a pulse duration applied. the resistance between ieg will decreased due to the tool vibration, which led to more efficient material dissolution. the maximum gap size achieved when electrode moved away from workpiece, which improved the flushing conditions and hence a better removal of the reaction products as compared to the minimum gap size condition [18]. experimental data from literature show that ultrasonic vibration would improve ecm'ed surface finish and low frequency vibration would improve mrr. this research fills the gap by studying vibration-enhanced ecm at low frequencies than 50 hz from both theoretical and experimental approaches. the following sections detail the experimental procedure and steps to simulate the flushing of by-products, and then compare simulation results with experimental data on mrr and quality of ecm'ed features. 3 experiments a horizontal vibration assisted ecm system was developed in this study. referring to figure 1, a workpiece plate (#5) was mounted with workpiece surface in vertical direction and an electrode (#6) traveled horizontally into the workpiece with feed rate controlled by a computer controlled positioner (#7). workpiece vibration was precisely generated by an electrodynamic shaker (#1). a pulsed power supply (#13) and two high-flow-rate pumps (#11, 16) completed the ecm cell. details of the cell components are listed in table 1. stainless steel tubes (𝜙𝜙9.5 mm od, 0.3 mm thick) were selected as electrodes. both 13 mm ends of an electrode were commercially coated with teflon to form a nonconductive layer of 0.02 mm thick on both outside and inside. the coated ends were carefully sanded off using 600-grit abrasive paper to make it electrically conductive. although the main application of this study was for ecm of domex 550mc hsla steel, plain carbon 1018 steel was used in the experiments. by calculating specific material removal rates (the variable c in equation (5)) of each chemical elements of each materials (table 2), it can be shown that the specific material removal rates of both materials are comparable: 𝐶𝐶1018 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 = 3.67 × 10−2 mm3/as and 𝐶𝐶𝐷𝐷𝐷𝐷𝐷𝐷𝑠𝑠𝐷𝐷 = 3.63 × 10−2 mm3/as [8]. workpieces were sawed and ground to rectangular samples (50 × 60 × 3.5 mm). relevant physical and mechanical properties of two materials are shown in table 3. table 1: ecm set-up components 1 labworks et-132 electrodynamic shaker 11 longer wt600-2j peristaltic pump 2 bearing housing 12 positive electric wire (to workpiece) 3 linear bearing 13 everlast 255ext power supply 4 stainless steel shaft 14 negative electric wire (to electrode) 5 workpiece 15 fresh-electrolyte tube 6 electrode 16 longer wt600-2j peristaltic pump 7 3-axis velmex positioner 17 fresh-electrolyte container 8 granite table 18 shaft coupling 9 used-electrolyte container 19 ecm cell with flash guard housing 10 used-electrolyte tube 20 electrode holder table 2: chemical composition of steels materials mass % 1018 steel 98.8-99.3 fe, 0.14-0.2 c, 0.6-0.9 mn domex 550mc 97.5 fe, 1.80 mn, 0.12 c, 0.1 si, 0.15 ti, 0.2 v the everlast 255 ext dc power supply provides either dc or pulsed dc of 3-150 a up to 500 hz pulsed current frequency. since a high peak current may generate sparks that damage the workpiece and electrode, the peak current was set at 26 a, current frequency at 500 hz and 50% duty cycle for all experiments. potassium bromide (kbr, 1 mol/l) was used as electrolyte. each experiment run was started with electrolyte temperature in the range of 21-25 °c. temperature or the electrolyte was measured before each experiment using an omega hh374 data logger thermometer. electrolyte conductivity, measured before each run using the hannah hi 8733 conductivity meter, was in the range of 111-121 ms/cm. although the metallic by-products in used electrolyte could be filtered using centrifugal method in small quantity, the settling method was used for a large quantity of used feng et al., (2017): international journal of engineering materials and manufacture, 2(4), 67-85 73 electrolyte. in the later method, the used electrolyte mixed with metallic by-products was stored in a used electrolyte container overnight so that the heavy metallic and salt by-products would be settled at the container bottom. the clear electrolyte at the top was separated by a peristaltic pump and used for subsequent experiment if its conductivity was still comparable with that of the fresh electrolyte. figure 1: front and top views of the laboratory ecm system table 3: physical and mechanical properties of 1018 steel *estimated values from similar alloys [20] ** estimated values from similar alloys [21] properties 1018 steel domex 550mc density (g/cm3) 7.87 8.13 hardness (brinell) 126 550 melting temperature (°c) 1450-1510 1520 shear strength (mpa) 330 371 tensile strength (mpa) 440 660 specific heat (j/g/°c) 0.486 0.434 *thermal conductivity (w/m°k) 53.6 41 *thermal diffusivity (mm2/s) 14.7 1.6 ** electrical resistivity (ωm) 15.9 × 10−8 17 × 10−8 the labworks et-132-2 electrodynamic shaker was powered by the labworks pa-151 linear power amplifier that in turn controlled by an agilent 33250a waveform generator. the computer controlled positioner included two velmex motorized frames, a rotary plate and a vxm-3 controller system. the system has a load capacity of 15.9 kg horizontally and 4.5 kg vertically with straight-line accuracy of 0.076 mm over a linear distance of 25 cm, feed rate range 2.5-5000 µm/s, and repeatability of 0.0025 mm. a tenma 72-6202 multimeter was used to detect electrical contact between conductive electrode and workpiece. initial inter-electrode gap was set at 0.3 mm for every experiment. electrode feed rate was fixed at 15 µm/s and the electrode travel distance was programmed to be 2.5 mm from the starting position. all experimental conditions are summarized in table 4. flushing enhancement with vibration and pulsed current in electrochemical machining 74 after ecm’ed, all samples were rinsed and clean with water in an ultrasonic bath for 1 minute and then dried with compressed air. all samples were positioned in a glass beaker in the bath with ecm’ed holes facing downward to facilitate removal of residual particles from the hole. the alicona infinite focus 3d profiler was used to analyze ecm’ed machined depths, surface finish, and wall taper angles. table 4: summary of experimental conditions variables values current frequency (hz) 500 electrode feed rate (µm/s) 15 electrode travel distance (mm) 2.5 electrolyte concentration (mol/l) 1 electrolyte conductivity (ms/cm) 111-121 electrolyte flow rate (l/min) 2.5 starting ieg (mm) 0.3 peak current (a) 26 vibration amplitude (µm) 0, 2.50, 4.44, 5.00, 7.50, 10.00 vibration frequency (hz) 0, 20, 30, 40, 60, 80 4 computer simulations recall that ecm on steel would form iron hydroxide by-products that need to be flush away for effective process (equations 3-4). the by-product was assumed to be spherical particles with dimensions to be measured experimentally. the ansys fluent was used to simulate how the particles would move in vibration assisted pulsed ecm. the effects of vibration frequency and vibration amplitude on particle average flushing speed were investigated. figure 2 illustrates the free-body diagram of a particle p in the ieg. the particle, between two electrodes and form and angle θ with the horizontal axis, is subjected to gravity force, buoyance force, and drag force in flowing electrolyte. due to the axisymmetric electrode, the drag force is in radial direction away from the tube center. when projecting all forces in the radial direction: 𝐹𝐹𝑟𝑟 = 𝐹𝐹𝑑𝑑 − (𝐺𝐺 − 𝐹𝐹𝑏𝑏) sin 𝜃𝜃 (7) where; fd = drag force, fr = total force along radial direction, g = gravity force, and fb = buoyance force since the solid particle density is higher than the density of electrolyte, the buoyance force of this particle is always smaller than its gravity force, thus the minimum value of radial direction force equals to 𝐹𝐹𝑑𝑑 − (𝐺𝐺 − 𝐹𝐹𝑏𝑏) when 𝜃𝜃 = 𝜋𝜋 2⁄ , and the maximum value of this force equals 𝐹𝐹𝑑𝑑 + (𝐺𝐺 − 𝐹𝐹𝑏𝑏) when 𝜃𝜃 = 3𝜋𝜋 2⁄ . the location at 𝜃𝜃 = 𝜋𝜋 2⁄ is the hardest location for reaction particle to flush away, as shown in figure 3a (location a). in this study, location a will be taken as simulation cell zone. the thickness of the electrode is 0.3 mm (figure 2) and the initial distance between workpiece and electrode is 0.3 mm, thus the simulation zone is a 0.3 mm × 0.3 mm square box ( figure 3b). figure 2: free-body diagram of particle p in inter-electrode gap figure 3 (a) side view of electrode and workpiece, and (b) enlarged view at the top most position fb feng et al., (2017): international journal of engineering materials and manufacture, 2(4), 67-85 75 electrolyte flow speeds were set to be 2, 3, and 4 m/s. the workpiece vibration follows the sine wave: 𝑥𝑥 = −𝐸𝐸𝐴𝐴𝐴𝐴𝐴𝐴(2𝜋𝜋𝜋𝜋𝑡𝑡) (8) where; x = location of workpiece relative to the fixed origin (the negative sign means the workpiece movement toward the left and away from the origin), a = vibration amplitude, and f = vibration frequency. at beginning, the particle center was located at lower left corner ( figure 3b) with particle initial velocity of 0 m/s. boundary conditions in simulation are listed in table 5. a simulation procedure stopped when the 𝑦𝑦-coordinate of particle center was larger than 0.3 mm, i.e. when the particle was flushed away from the electrode surface. simulation steps are detailed in the appendix. table 5: boundary conditions for first series simulation variables values vibration frequency 𝜋𝜋 (hz) 20, 30, 40 vibration amplitude 𝐸𝐸 (µm) 5.0, 7.5, 10.0 table 6 corresponding vibration amplitude and frequency at maximum vibration input current (7a) vibration frequency (hz) vibration amplitude (µm) 10 160.00 20 40.00 30 17.80 40 10.00 50 6.40 60 4.44 70 3.26 80 2.50 90 1.98 100 1.60 110 1.32 120 1.11 130 0.95 140 0.82 150 0.71 175 0.52 200 0.40 500 0.065 1000 0.016 5000 0.00064 10000 0.00016 to investigate the influence of the vibration frequency and vibration amplitude and electrolyte flow speed on average flushing speed, two series of simulations were conducted: i) the first series simulation was used to build a relationship between experimental results and simulation results. three input levels for each variable were set (table 5). thus, total number of simulation run was 32 = 9. ii) the second series simulation was used to theoretically investigate the maximum flushing speed for the experimental system. the electrolyte flow speed was fixed at 4 m/s, and input current for vibration table was fixed at its maximum value (7 a), the corresponding vibration frequency and vibration amplitude will follow 𝐸𝐸𝜋𝜋2 = constant based on the specifications of system and are listed in iii) table 6. 5 results and discussions the effects of vibration amplitude and vibration amplitude on average flushing speed will illustrated by simulation results. identification of ecm by-product, hole profile, relationship between average flushing speed, and machining depth/taper angle are also demonstrated in the following sections. 5.1 by-products flushing enhancement with vibration and pulsed current in electrochemical machining 76 a sem image of ecm by-products is shown in figure . although the particles are coagulated to different shapes, the single particles have different sizes in the range 0.5-4 µm. it is assumed for simplicity that the particle is spherical with average size of ~2 µm. an edx spectrum on dried particles on carbon tape (figure ) suggests that the by-product is iron hydroxide. elements of the kbr electrolyte are absent after the by-products were repeatedly rinsed in deionized water. figure 8: sem image of dried ecm byproducts on a titanium plate. figure 9: edx spectrum of ecm by-products on carbon tape. iron, carbon, and oxygen are dominating elements. 5.2 simulation of average flushing speeds recall that the simulation cell is 0.3 mm × 0.3 mm ( figure 3b), and a simulation will be terminated if the 𝑦𝑦-coordinate of a particle center is larger than 0.3 mm. a typical particle moves along 𝑦𝑦-direction is shown in figure 4. average flushing speed, 𝑉𝑉𝑎𝑎𝑎𝑎𝑠𝑠, is defined as the secant slope of particle path: 𝑉𝑉𝑎𝑎𝑎𝑎𝑠𝑠 = particle travel distance time (9) in figure 4 a particle takes 831 µs to travel a distance of 300 µm, then its average flushing speed is 0.3610 m/s. figure 4: particle movement in y-direction (f = 20 hz; av = 10 µm; s = 4 m/s) figure 5: effect of vibration frequency on average flushing speed at ivibration = 7a the effect of vibration frequency on average flushing speed at 𝐼𝐼𝑎𝑎𝑣𝑣𝑏𝑏𝑟𝑟𝑎𝑎𝑠𝑠𝑣𝑣𝐷𝐷𝑣𝑣 = 7𝐸𝐸 is shown in figure 5. the average flushing speed decreases with increasing vibration frequency. neglect the effect of the workpiece vibration on the particle movement along electrode direction, the distance between workpiece and the particle center is: 𝑧𝑧𝑔𝑔 = 𝐸𝐸𝑎𝑎 sin(2𝜋𝜋𝜋𝜋𝑡𝑡) + 𝐸𝐸0 (10) where; dg = gap between particle center and workpiece surface (mm), av = vibration amplitude (mm), f = vibration frequency (hz), and a0 = initial gap between particle center and workpiece (mm). 5 µm c o fe fe feng et al., (2017): international journal of engineering materials and manufacture, 2(4), 67-85 77 since 𝐼𝐼𝑎𝑎𝑣𝑣𝑏𝑏𝑟𝑟𝑎𝑎𝑠𝑠𝑣𝑣𝐷𝐷𝑣𝑣 = 7𝐸𝐸, the average flushing speed decreases from 0.5736 m/s (𝜋𝜋 = 10 hz, 𝐸𝐸𝑎𝑎 = 160 µm) to 0.3231 m/s (𝜋𝜋 = 10,000 hz, 𝐸𝐸𝑎𝑎 = 0.000,16 µm) when vibration frequency increases from 10 to 10,000 hz. for fixed vibration current or constant vibration power, the vibration amplitude and vibration frequency follow the relationship 𝐸𝐸𝑎𝑎𝜋𝜋2 = b where b is a constant, then equation (10) becomes: 𝑧𝑧𝑔𝑔 = 𝐵𝐵 sin(2𝜋𝜋𝜋𝜋𝑡𝑡) 𝜋𝜋2 + 𝐸𝐸0 (11) equation (11) suggests that the distance between particle center and workpiece dg decreases drastically with increasing vibration frequency f. therefore, for fixed current on vibration generator a high frequency leads to smaller gap, lesser drag force and lower average flushing speed. 5.3 hole profiles the electrical field strength between a circular electrode and a flat plate can be derived [22] and schematically show in figure 6. the highest field strength is along a circular ring directly below the tubular electrode; the field strength is diminishing outward and away from the tube wall, but is additive to form a pronounced peak at the tubular electrode center. the result is the strong current directly below the electrode, an average current in the central region, and a weaker stray current at positions away from the electrode. the presence of an insulating coating on the electrode side significantly reduces the stray current to improve the ecm efficiency. (a) (b) figure 6: (a) electrical field around a tubular electrode, and (b) resulted profile of an ecm’ed hole the resulted hole profile now can be explained. significant material is removed directly below the electrode while the corner and center position of a hole are rounded off due to weaker stray current. the agglomerated by-product particles, which collected in a small gap between electrode and workpiece, interfere with the ion transport mechanism if they are not effectively flushed away. however, the flushed particles in fast flowing electrolyte would erode and enlarge the overcut of the ecm’ed profile, and round off the sharp entrance corners. figure 7a shows a typical 3d profile measurement of an ecm’ed profile using the alicona system, from which a cross sectional view can be constructed and analyzed (figure 7b). eight locations, 45° apart, were measured for quality assessment and repeatability. the vertical distance ℎ between top and bottom surface (a-d) is the machining depth. neglecting the transitional curves ab and cd, the slope of line bc can be constructed which defines the corresponding hole taper angle α. (a) (b) figure 7: typical 3d profile of an ecm’ed hole. 𝜋𝜋 = 20 hz, 𝐸𝐸𝑎𝑎 = 10 µm, 𝑆𝑆 = 4 m/s flushing enhancement with vibration and pulsed current in electrochemical machining 78 5.3.1 machining depths the effects of vibration amplitude on average flushing speed and machining depth are demonstrated in figure 8. at every vibration frequency (20, 30, and 40 hz), a higher vibration amplitude causes faster average flushing speed and deeper machining depth. when vibration amplitude increases from 5 µm to 10 µm, the average flushing speeds increase by 5.5% (0.3423-0.3610 m/s), 7.8% (0.3517-0.3790 m/s) and 10.0% (0.3608-0.3968 m/s) at respective frequency. consequently, machining depths increase by 4% (1282-1336 µm), 3.7% (1311-1360 µm) and 20% (13191584 µm) at corresponding frequency. (a) 𝜋𝜋 = 20 hz (b) 𝜋𝜋 = 30 hz (c) 𝜋𝜋 = 40 hz figure 8: effect of vibration amplitude on average flushing speed and machining depth (a) 𝐸𝐸 = 5.0 µm (b) 𝐸𝐸 = 7.5 µm (c) 𝐸𝐸 = 10.0 µm figure 9: effect of vibration frequency on average flushing speed and machining the effects of vibration frequency on average flushing speed and machining depth are illustrated in figure 9. at every vibration amplitude (5, 7.5, and 10 µm), a higher vibration frequency leads to faster average flushing speed and deeper machining depth. when vibration frequency increases from 20 to 40 hz, the average flushing speeds increase by 5.4% (0.3423-0.3608 m/s), 7.8% (0.3517-0.3790 m/s) and 9.9% (0.3610-0.3968 m/s), at respective vibration amplitude. improving of flushing speed changes machining depths by 2.9 % (1282-1319 µm), 9.9% (13081437 µm) and 18.6% (1336-1584 µm), respectively. the relationship between average flushing speed and machining depth is shown in figure 10. due to the limitation of power supply to the vibration system, the input current can be adjusted up to 7 a at frequency <40 hz with fixed 10 µm amplitude. this maximum current of 7 a must be maintained at frequency higher than 40 hz with adjustable amplitudes. simulation for frequency below and above 40 hz shows the peak flushing average at 40 hz while similar trend is seen for the hole depth data. there is a clear correlation between average flushing speed and machining depth. low frequency vibration of workpiece enhances flushing speed, enhances ion transport rate and leads to more effective machining rate. similar results were also reported by other researchers [2] who observed that: − at any vibration amplitude (4, 6, and 8 µm), the mrr increased when increasing vibration frequency from 0 to 50 hz. however, the mrr dropped when increasing frequency further to 200 hz. − at any vibration frequency (50 and 100 hz), the mrr increased with increasing vibration amplitude in the range 0-8 µm. the maximum mrr was obtained when vibrating at 8 µm amplitude for any vibration frequency. feng et al., (2017): international journal of engineering materials and manufacture, 2(4), 67-85 79 the maximum machining depth, therefore highest mrr, in this study is when vibrating a workpiece at 40 hz compared to 50 hz in other study [2]. the simulation study indicates that a higher flushing speed is expected at lower frequency (figure 5), therefore, a lower frequency with larger vibration amplitude could lead to optimal mrr. the upper bound for increasing vibration amplitude is the critical inter-electrode distance at which damaging sparks would occur due to electrical discharging. the trends from simulation and experimental data can be explained. − at either higher vibration frequency or vibration amplitude, more ions and by-products particles starting at the workpiece surface would be pushed toward the advancing electrode in the first half cycle, when the workpiece is reversed during the second half cycle, theses ions and particles -physically are away from the solid workpiece surface -are subjected to higher shear and swept away in the electrolyte flow. − when ions and by-products are effectively swept away from the workpiece surface, fresh electrolyte can be replenished to accelerate the electrochemical reactions (equations 1-4) and result in a deeper hole and a faster removal rate. figure 10: relationship between average flushing speed and machining depth 5.3.2 taper angles the effects of vibration amplitude on average flushing speed and taper angle are illustrated in figure 11. at every vibration frequency (20, 30, and 40 hz), a higher vibration amplitude leads to faster flushing speed and smaller taper angle – therefore, straighter and sharper hole profile. when vibration amplitude increases from 5.0 to 10.0 µm, the taper angles decreases by 8.7% (31.92-29.15°), 12.8% (29.32-25.56°) and 43.4% (29.28-16.57°), at respective vibration frequency. the effects of vibration frequency on average flushing speed and taper angle are illustrated in figure 12. at every vibration amplitude (5, 7.5, and 10 µm), a higher vibration frequency leads to a smaller taper angle. when vibration frequency increases from 20 to 40 hz, the taper angles decreases by 3.4% (31.92-29.28°), 27.3% (29.81-21.67°) and 43.2% (29.15-16.57°) at corresponding vibration amplitude. simulation and experimental data suggest a negative correlation between average flushing speed and taper angle (figure 15). authors from a different study [16] reported a similar trend on hole shape after ecm; the conicity (slope of a cone) decreased from 3.95 to 3.25% when vibration amplitude increased from 20 to 100 µm. this trend can also be explained qualitatively: − vibration of workpiece leads to a higher flushing speed that breaks up agglomerated groups of by-products into smaller chunks of particles. − the smaller chunks forming between electrodes then travel up the wall of hole and out (figure 6). the smaller coalesced particles would erode the wall less and result in smaller taper angle and sharper hole profile. flushing enhancement with vibration and pulsed current in electrochemical machining 80 (a) 𝜋𝜋 = 20 hz (b) 𝜋𝜋 = 30 hz (c) 𝜋𝜋 = 40 hz figure 11: effect of vibration amplitude on average flushing speed and taper angle (a) 𝐸𝐸 = 5.0 µm (b) 𝐸𝐸 = 7.5 µm (c) 𝐸𝐸 = 10.0 µm figure 12: effect of vibration frequency on average flushing speed and taper angle figure 13: relationship between average flushing speed and hole taper angle. feng et al., (2017): international journal of engineering materials and manufacture, 2(4), 67-85 81 6 conclusions and recommendations this research simulates how the ion hydroxide by-product being flushing away in electrochemical machining. simulation results and experimental data for ecm’ing 1018 steel with pulsed current and low frequency vibration were performed on a horizontal ecm system. the paper shows that: 1) iron hydroxide particle with an average size of ø2 µm was the resulted by-product.. 2) simulation of the motion of a single particle using computational fluid dynamic is performed to track the particle motion and speed between electrodes. flushing of by-products is characterized by calculating of particle flushing speed when it exits inter-electrode gap. the optimal flushing speed of ~0.4 m/s was calculated for workpiece vibration frequency of 40 hz at 10 µm vibration amplitude. 3) simulation results suggest that a higher flushing speed can be obtained below 40 hz if vibrating amplitude larger than 10 µm is possible without initiating damaging sparks. 4) experimental results suggest high flushing speed of by-product leads to deeper and sharper ecm profiles. more particles are pushed away from the workpiece surface during the first half of a vibrating cycle, and they are swept away by electrolyte flow during the cycle’s second half. future works should (i) explore the effect of vibration at lower than 40 hz yet at higher vibration amplitude without initiating sparks, and (ii) extend the simulation to study the interaction of multiple particles in the inter-electrode gap. acknowledgement this research work was support with grant #1745678 from conacyt (mexico); and grants #512433, #2847 from agilent university research corporation (usa). references 1. mcgeough, j. a. (1974). principles of electrochemical machining. london: chapman and hall. 2. liu, z., zhang, h., chen, h., & zeng, y. (2013). investigation of material removal rate in micro electrochemical machining with lower frequency vibration on workpiece. international journal of machining and machinability of materials, 14(1), 91-104. 3. acharya, b. r., mohanty, c. p., & mahapatra, s. s. (2013). multi-objective optimization of electrochemical machining of hardened steel using nsgaii. procedia engineering, 51, 554-560. 4. senthilkumar, c., ganesan, g., & karthikeyan, r. (2013). influence of input parameters on characteristics of electro chemical machining process international journal of applied science and engineering, 11(1), 13-24. 5. bhattacharyya, b., & sorkhel, s. k. (1999). investigation for controlled ellectrochemical machining through response surface methodology-based approach. journal of materials processing technology, 86(1–3), 200-207. 6. senthilkumar, c., ganesan, g., karthikeyan, r., & srikanth, s. (2010). modelling and analysis of electrochemical machining of cast al/20%sicp composites. materials science and technology, 26(3), 289-296. 7. schuster, r., kirchner, v., allongue, p., & ertl, g. (2000). electrochemical micromachining. science, 289(5476), 98-101. 8. feng, z., granda, e., & hung, w. (2016). experimental investigation of vibration-assisted pulsed electrochemical machining. procedia manufacturing, 5, 798-814. 9. bhattacharyya, b., & munda, j. (2003). experimental investigation on the influence of electrochemical machining parameters on machining rate and accuracy in micromachining domain. international journal of machine tools and manufacture, 43(13), 1301-1310. 10. munda, j., & bhattacharyya, b. (2008). investigation into electrochemical micromachining (emm) through response surface methodology based approach. the international journal of advanced manufacturing technology, 35(7-8), 821-832. 11. senthilkumar, c., ganesan, g., & karthikeyan, r. (2012). ecm of al/15% sicp composites through a response surface methology-based approach. international journal of materials research, 103, 378-382. 12. ruszaj, a., zybura-skrabalak, m., skoczypiec, s., & żurek, r. (2001). electrochemical machining supported by electrode ultrasonic vibrations. paper presented at the 13th international symposium for electromachining, isem, spain, may. 13. nicoară, d., hedeş, a., & şora, i. (2006). ultrasonic enhancement of an electrochemical machining process. paper presented at the proceedings of the 5th wseas international conference on applications of electrical engineering. 14. patel, j. b., feng, z., villanueva, p., & hung, w. n. p. (2017). quality enhancement with ultrasonic wave and pulsed current electrochemical machining. procedia manufacturing, 10, 662-673. 15. ghoshal, b., & bhattacharyya, b. (2015). vibration assisted electrochemical micromachining of high aspect ratio micro features. precision engineering, 42, 231-241. 16. ebeid, s. j., hewidy, m. s., el-taweel, t. a., & youssef, a. h. (2004). towards higher accuracy for ecm hybridized with low-frequency vibrations using the response surface methodology. journal of materials processing technology, 149(1-3), 432-438. flushing enhancement with vibration and pulsed current in electrochemical machining 82 17. bhattacharyya, b., malapati, m., munda, j., & sarkar, a. (2007). influence of tool vibration on machining performance in electrochemical micro-machining of copper. international journal of machine tools and manufacture, 47(2), 335-342. 18. rebschläger, a., kollmannsperger, r., & bähre, d. (2014). video based process observations of the pulse electrochemical machining process at high current densities and small gaps. procedia cirp, 14, 418-423. 19. retrieved from http://www.velmex.com/products/xslide/xslide-motorized.html. 20. kothandaraman, c., & subramanyan, s. (2013). heat and mass transfer data book (8th edition ed.): new academic science. 21. retrieved from http://www.nde-ed.org. 22. serway, r., & jewett, j. (2013). physics for scientists and engineers with modern physics: nelson education. 23. gosman, a., & loannides, e. (1983). aspects of computer simulation of liquid-fueled combustors. journal of energy, 7(6), 482-490. 24. anderson, t., & jackson, r. (1968). a fluid mechanical description of fluidized beds: stability of the uniform state of fluidization. i&ec fundamentals, 7, 12-21. feng et al., (2017): international journal of engineering materials and manufacture, 2(4), 67-85 83 appendix modeling of particle flow this appendix details steps to simulate a particle flow between electrodes in electrochemical machining (ecm). formulas are provided for computational fluid dynamic simulation using ansys fluent software. referring to figures 2 and 3, it is assumed that: − the simulation is simplified to a 2-dimension problem. − the simulation location is the top most part of the horizontal ecm electrode-workpiece area. − the iron hydroxide ecm by-product is assumed to be a spherical particle with ø2 µm diameter. − there is no interaction among particles. − although the electrolyte flow affects the particle, there is negligible effect of the particle to electrolyte flow. for any particle-fluid flow system the dynamic of fluid flow is characterized by (i) the solution of navier-stokes equation for continuum fluid (primary phase), (ii) the solution of newton equation of motion for discrete particles (second phase), and (iii) initial and boundary conditions. in this investigation the computational fluid dynamics discrete element method (cfd-dem) was used to capture the motion of discrete particles. in cfd-dem coupling technique, the flow of primary phase (fluid) was determined by the cfd and the motion of second phase (particles) was obtained by solving newton equations of motion on a computational cell scale. for particle-fluid flow system a particle can have translational and rotational motion. during its movement, the particle may interact with its neighboring particles or walls and interact with its surrounding fluid, through which the momentum and energy are exchanged. such movement is not only by the forces and torques originated from its immediately neighboring particles and vicinal fluid, but is also affected by particles and fluids far away through the propagation of disturbance waves. in the dem approach, we introduce a numerical time step which less than a critical value so that disturbance cannot propagate from the particle and fluid farther than its immediate neighboring particles and vicinal fluid. for a coarse particle system, all the resultant forces on a particle can be determined exclusively from its interaction with the contacting particles and vicinal fluid. however, for a fine particle system, non-contact forces, such as van der waals and electrostatic forces are also considered. since a particle is assumed to be spherical, only translational movement of the particle is considered in this study. the translational motion of discrete particles i with mass 𝑚𝑚𝑣𝑣 follows newton 2nd law: 𝑚𝑚𝑣𝑣 𝑧𝑧𝑣𝑣𝚤𝚤���⃗ 𝑧𝑧𝑡𝑡 = �𝐹𝐹𝚤𝚤𝚤𝚤𝑐𝑐����⃗ 𝑗𝑗 + �𝐹𝐹𝚤𝚤𝚤𝚤 𝑣𝑣𝑐𝑐�������⃗ 𝚤𝚤 + 𝐹𝐹𝚤𝚤 𝑓𝑓�����⃗ + 𝐹𝐹𝚤𝚤 𝑔𝑔�����⃗ (a1) where; mi = mass of particle i, 𝑣𝑣𝚤𝚤���⃗ : translational velocity of particle 𝐴𝐴, 𝐹𝐹𝚤𝚤𝚤𝚤𝑐𝑐����⃗ : contact force acting on particle 𝐴𝐴 by particle j, 𝐹𝐹𝚤𝚤𝚤𝚤 𝑣𝑣𝑐𝑐�������⃗ : noncontact force acting on particle i by particle k or other sources, 𝐹𝐹𝚤𝚤 𝑓𝑓�����⃗ : particle-fluid interaction force on particle i, and 𝐹𝐹𝚤𝚤 𝑔𝑔�����⃗ : gravitational force. non-contact forces, such as van der waals force and capillary force, can be neglected since they have little influence on the flushing time. therefore, equation (a1) can be simplified to: 𝑚𝑚𝑣𝑣 𝑧𝑧𝑣𝑣𝚤𝚤���⃗ 𝑧𝑧𝑡𝑡 = 𝐹𝐹𝚤𝚤 𝑓𝑓�����⃗ + 𝐹𝐹𝚤𝚤 𝑔𝑔�����⃗ (a2) the surrounding fluid will interact with particle by generating various particle-fluid interaction forces (drag force), in addition to the buoyance force. for a single spherical particle in a fluid, the equation to determine the drag resistance force was derived to be [23]: 𝐹𝐹𝚤𝚤 𝑓𝑓�����⃗ = 𝐹𝐹𝑑𝑑����⃗ + 𝐹𝐹𝑏𝑏����⃗ = 𝑚𝑚𝑣𝑣 𝑣𝑣𝐹𝐹����⃗ − 𝑣𝑣𝑝𝑝����⃗ 𝜏𝜏𝑟𝑟 − 𝑉𝑉𝑣𝑣𝜌𝜌�⃗�𝑔 (a3) with 𝜏𝜏𝑟𝑟 = 𝜌𝜌𝑝𝑝𝑧𝑧𝑝𝑝2 18 24 𝐶𝐶𝑑𝑑𝑀𝑀𝑠𝑠 (a4) 𝑀𝑀𝑠𝑠 ≡ 𝜌𝜌𝑧𝑧𝑝𝑝�𝑢𝑢�⃗ 𝑝𝑝 − 𝑢𝑢�⃗ � 𝜇𝜇 (a5) flushing enhancement with vibration and pulsed current in electrochemical machining 84 where; 𝜏𝜏𝑟𝑟 = particle relaxation time, 𝐹𝐹𝑑𝑑����⃗ = drag force, 𝐹𝐹𝑏𝑏����⃗ : buoyance force, 𝑣𝑣𝐹𝐹����⃗ = fluid phase velocity, 𝑣𝑣𝑝𝑝����⃗ = particle velocity, 𝑉𝑉𝑣𝑣: particle volume, 𝜌𝜌: fluid density, 𝜇𝜇: molecular viscosity of the fluid, 𝜌𝜌𝑝𝑝: particle density, 𝑧𝑧𝑝𝑝 = particle diameter, and 𝑀𝑀𝑠𝑠 = relative reynold number. by combining equations (a2 a3), the equation for particle motion becomes: 𝑧𝑧𝑣𝑣𝚤𝚤���⃗ 𝑧𝑧𝑡𝑡 = 𝑣𝑣𝐹𝐹����⃗ − 𝑣𝑣𝑝𝑝����⃗ 𝜏𝜏𝑟𝑟 + �⃗�𝑔�𝜌𝜌𝑝𝑝 − 𝜌𝜌� 𝜌𝜌𝑝𝑝 (a6) during an iteration step in simulation, the source terms applied to the continuous phase equation to the new values are: 𝐹𝐹𝑣𝑣𝑠𝑠𝑛𝑛 = 𝐹𝐹𝐷𝐷𝑠𝑠𝑑𝑑 + 𝛼𝛼(𝐹𝐹𝑐𝑐𝑎𝑎𝑠𝑠𝑐𝑐𝑐𝑐𝑠𝑠𝑎𝑎𝑠𝑠𝑠𝑠𝑑𝑑 − 𝐹𝐹𝐷𝐷𝑠𝑠𝑑𝑑) (a7) 𝑄𝑄𝑣𝑣𝑠𝑠𝑛𝑛 = 𝑄𝑄𝐷𝐷𝑠𝑠𝑑𝑑 + 𝛼𝛼(𝑄𝑄𝑐𝑐𝑎𝑎𝑠𝑠𝑐𝑐𝑐𝑐𝑠𝑠𝑎𝑎𝑠𝑠𝑠𝑠𝑑𝑑 − 𝑄𝑄𝐷𝐷𝑠𝑠𝑑𝑑) (a8) 𝑀𝑀𝑣𝑣𝑠𝑠𝑛𝑛 = 𝑀𝑀𝐷𝐷𝑠𝑠𝑑𝑑 + 𝛼𝛼(𝑀𝑀𝑐𝑐𝑎𝑎𝑠𝑠𝑐𝑐𝑐𝑐𝑠𝑠𝑎𝑎𝑠𝑠𝑠𝑠𝑑𝑑 − 𝑀𝑀𝐷𝐷𝑠𝑠𝑑𝑑) (a9) where; 𝛼𝛼 = under-relaxation factor for particles, default value is 0.9 for transient flow simulation with unsteady particle tracking, otherwise 𝛼𝛼 is 0.5, 𝐹𝐹 = force, 𝑄𝑄 = energy, and 𝑀𝑀= momentum. for fluid phase, the governing equations derived from navier-stoke equation comply with the law of conservation of mass and momentum in terms of local-average variables [24]: 𝜕𝜕𝜀𝜀𝑓𝑓 𝜕𝜕𝑡𝑡 + ∇ ∙ 𝜀𝜀𝑓𝑓𝑢𝑢�⃗ 𝑓𝑓 = 0 (a10) 𝜕𝜕(𝜌𝜌𝑓𝑓𝜀𝜀𝑓𝑓𝑢𝑢�⃗ 𝑓𝑓) 𝜕𝜕𝑡𝑡 + ∇ ∙ �𝜌𝜌𝑓𝑓𝜀𝜀𝑓𝑓𝑢𝑢�⃗ 𝑓𝑓𝑢𝑢�⃗ 𝑓𝑓� = −𝜀𝜀𝑓𝑓∇𝑝𝑝 − 𝐹𝐹𝑃𝑃−𝐹𝐹���������⃗ + ∇ ∙ �𝜀𝜀𝑓𝑓𝜏𝜏� + 𝜌𝜌𝑓𝑓𝜀𝜀𝑓𝑓�⃗�𝑔 (a11) figure a1. simulation boundaries. figure a1, part of figure 3 in the main text, shows the simulation boundaries. a spherical particle p starts at the lower left corner of the two-dimensional 0.3 mm x 0.3 mm simulation area. the vibration of the workpiece (governed by vibration frequency and amplitude) alters the position of this particle. the flow chart in figure a2 show how position and velocity of the particle p are calculated. after each iteration, the position yp of the particle is compared against the vertical boundary; when the particle exits the vertical boundary (yp > 0.3 mm) then the simulation would end. feng et al., (2017): international journal of engineering materials and manufacture, 2(4), 67-85 85 figure a2 flow chart of simulation abstract 1 introduction 2 literature review 2.1 electrolysis 2.2 effect of higher voltage 2.3 effect of pulsed current 2.4 effect of electrolyte flow rate 2.5 effect of ultrasonic vibration 2.6 effect of low frequency mechanical vibration 3 experiments 4 computer simulations 5 results and discussions 5.2 simulation of average flushing speeds 5.3 hole profiles 5.3.1 machining depths 5.3.2 taper angles 6 conclusions and recommendations acknowledgement references international journal of engineering materials and manufacture (2017) 2(4) 103-109 https://doi.org/10.26776/ijemm.02.04.2017.04 a. banu1, m. a. bakar2, m. y. ali1 and y. t. a. erry1 1department of manufacturing and materials engineering, international islamic university malaysia, po box 10, 50728 kuala lumpur, malaysia 2department of mechanical engineering, politeknik sultan haji ahmad shah 25350 semambu, kuantan, pahang, malaysia e-mail: eadesta@iium.edu.my reference: banu, a., bakar, m. a., ali, m. y. and erry y. t. a. (2017). analysis of wedm process parameters on surface roughness and kerf using taguchi method. international journal of engineering materials and manufacture, 2(4), 103-109. analysis of wedm process parameters on surface roughness and kerf using taguchi method asfana banu, mazilah abu bakar, mohammad yeakub ali and erry y. t. adesta received: 12 october 2017 accepted: 13 november 2017 published: 10 december 2017 publisher: deer hill publications © 2017 the author(s) creative commons: cc by 4.0 abstract in obtaining the best quality of engineering parts, the quality of machined surface plays an essential role. the fatigue strength, wear resistance, and corrosion of workpiece are some of the aspects of the qualities that can be improved. this paper investigates the effect of wire electrical discharge machining (wedm) process parameters on surface roughness and kerf on stainless steel using distilled water as dielectric fluid and brass wire as tool electrode. the selected process parameters are voltage open, wire speed, wire tension, voltage gap, and off time. empirical models using taguchi method were developed for the estimation of surface roughness and kerf. the analysis revealed that off time has major influence on surface roughness and kerf. the optimum machining parameters for minimum surface roughness and kerf were found to be 10 v open voltage, 2.84 µs off time, 12 m/min wire speed, 6.3 n wire tension, and 54.91 v voltage gap. keywords: wedm, surface roughness, kerf, process parameters, taguchi method, anova, s/n ratio 1 introduction wire electrical discharge machining (wedm) is a specialized thermal machining process used to machine complex shape components with high accuracy using a thin single-strand metal wire (0.1 or 0.25mm diameter) as an electrode. it is a technique used in industry for high-precision machining of all types of conductive materials such as metals, metallic alloys, graphite [1-3]. it is also known as an electro-erosion machining process. when the gap voltage is sufficiently large (i.e reaches the breakdown voltage of dielectric fluid), high power spark is produced, where the temperature increases up to 10,000 °c and allows the material to be removed from the machining area [3-4]. wedm is particularly valuable for applications involving manufacture of stamping dies, extrusion dies, aerospace parts such as micro gas turbine blades, and electronic components [5-6]. without wedm, the fabrication of precision workpiece requires many hours of manual grinding and polishing [5]. in wedm, the performance measures are the indicators used to observe the quality of the finished parts, whereas, the process parameters are the variables that influence the machining process. the most significant performance measures in wedm are surface finish, material removal rate, and kerf. all of these performance measures are usually affected by the process parameters such as pulse on-time, open voltage, servo voltage, wire feed, dielectric pressure, and wire tension. these parameters have the ability to produce better quality machined surface with less cracks and surface damages [7]. surface roughness is used to control the quality of the finished part while kerf is used to determine the accuracy of dimension. according to previous studies, the surface roughness improves when the pulse duration and the discharge current decreases [8]. kerf is a width of the machined slots, where it also measures the amount of the material that is wasted during machining. it determines the dimensional accuracy of the finishing part. kerf limits the internal corner radius during machining of the workpiece [3, 9-10]. open voltage and wire tension are some of the main parameters that can control the kerf and precision of the machined part [8, 11]. it is because open voltage can control the wire vibration and breakdown distance. the corner errors and kerf variations mainly caused by the wire tool deflection and vibration in the discharge gap, these are the main factors that influence the machining accuracy. a study has been carried out to examine the kerf variations and the discharge gap (25-75 µm) usually achieved in conventional wedm analysis of wedm process parameters on surface roughness and kerf using taguchi method 104 [5]. hence, the objective of this paper is to investigate the effect of wedm process parameters on surface roughness and kerf of stainless steel using distilled water as the dielectric fluid and brass wire as the tool electrode. 2 methodology the experimental investigation was performed using the mitsubishi fx10k cnc wire edm. the workpiece material, which was stainless steel s304, was prepared in desired dimension of 150 mm × 8 mm ×10 mm with flat surface finish. stainless steel is commonly used almost in all industrial applications and it accounts for approximately 50% of the world’s steel production and consumption. this is because of its aesthetic view in architectures, resistance against corrosion and chemicals, high hardenability, and well mechanical property. as a result, it has become the most preferred material [8, 12]. brass wire with 0.2 mm diameter was used as the tool electrode whereas distilled water as the dielectric fluid. the experimental parameters are listed in table 1. the parameters were selected based on the type of machining material, tool material, height of the workpiece, and the capability of the machine. the controlled parameters were voltage open, wire speed, wire tension, voltage gap, and off time. mitutoyo surftest (sv-514) was used to measure the surface roughness (ra). the tester used a cutoff length of 2 mm and evaluation length of 0.8 mm with a surfpak v4.10 (2) software having a resolution of 0.01 μm and stylus speed of 0.10 mm/sec. measurements of ra were repeated three times and the average of ra were calculated. on the other hand, scanning electron microscope, sem (jeol jsm-5600) was used to measure the kerf of the workpiece. the measurements of kerf were taken at three different places and the average of the kerf was calculated. the experiments were based on the taguchi’s l16 orthogonal array design. the experimental results in table 2 are analysed using signal-to-noise (s/n) ratio and analysis of variance (anova) approach. the s/n ratio is used as a measurable value instead of standard deviation. this is because of the fact that as the mean decreases, the standard deviation also will decrease and vice versa. the s/n ratio depends on the type of characteristic, where the higher value that represents a better machining performance such as mrr is known as higher is better. on the other hands, the characteristic that have lower value that represents a better machining performance, such as surface roughness and kerf is called lower is better as shown in eqn. 1 [13-14]. 𝑆𝑆 𝑁𝑁 = −10log (1 𝑛𝑛 ∑ 𝑦𝑦𝑖𝑖 2𝑛𝑛 𝑖𝑖=1 ) (1) where, 𝑛𝑛 is the number of iteration and 𝑦𝑦 is the experimental result. 3 results and discussion 3.1 surface roughness, ra signal-to-noise (s/n) ratio. the s/n ratio according to taguchi method is the ratio of signal to noise where signal represents the desirable value and noise represents the undesirable value. the s/n ratio for the experiments conducted is shown in table 2 meanwhile the mean of s/n ratio for ra is presented for four levels are tabulated in table 3. figure 1 shows the effects of process parameters on mean s/n ratio for ra. according to taguchi method, minimizing average ra would be better for precision manufacturing. hence, “smaller-the better” type problems would give a smaller values for average ra in order to get a better quality of finish parts [15]. based on table 3 and figure 1, it was found that s/n ratio for ra decreases when the wire speed, wire tension, and voltage gap are at level 4. the wire vibration tends to reduce when the wire tension increases which helps the surface roughness to improve [16]. however, the s/n ratio for ra increases when the off time is at level 4 and level 3 for voltage open. voltage open should be kept as low as possible in order to get a better surface roughness. it is to avoid powerful explosion to occur which can cause deep crater on the machined surface and resulting to poor surface quality at the machined area [16]. analysis of variance (anova). an empirical model as expressed in eqn. 2 is developed by anova. based on table 4, the model f-value of 102.38 implies that the model is significant. there is only a 0.14% chance of noise that could occur in the model f-value. the prob>f values less than 0.0500 indicates that the model terms a (voltage open), b (off time), e (voltage gap), ab (voltage open and off time), ac (voltage open and wire speed), bd (off time and wire tension), be (off time and voltage gap), cd (wire speed and wire tension), ce (wire speed and voltage gap), and de (wire tension and voltage gap) are significant. the most significant factor that affects the ra is b (off time) with 77.57 f-value. however, values that are greater than 0.1000 indicates the model terms are not significant. if there are many insignificant model terms, then the model reduction may improve the model. factors c (wire speed) and d (wire tension) are the most uninfluenced factors since their prob>f are 0.5508 and 0.9052 respectively. nevertheless, when factor c (wire speed) interacts with factor a (voltage open), d (wire tension), and e (voltage gap), the model terms becomes significant. hence, it means that factor c (wire speed) cannot be removed from the hierarchy, even though it is not significant if it is stand-alone. similarly for factor d (wire tension), the model terms become significant when it interacts with factor b (off time), c (wire speed), and e (voltage gap). the predicted r2 of 0.8133 is in reasonable agreement with the adjusted r2 of 0.9878. adequate precision measures the s/n ratio, banu et al., (2017): international journal of engineering materials and manufacture, 2(4), 103-109 105 where the ratio greater than 4 is desirable. the ratio of 44.649 indicates that the signal is adequate. this model can be used to navigate the design space. 𝑅𝑅𝑎𝑎 = 3.755 + 0.831𝐴𝐴 − 1.063𝐵𝐵 + 1.949𝐶𝐶 − 2.314𝐷𝐷 − 0.199𝐸𝐸 − 0.096𝐴𝐴𝐵𝐵 − 0.058𝐴𝐴𝐶𝐶 + 0.206𝐵𝐵𝐷𝐷 + 0.011𝐵𝐵𝐸𝐸 − 0.035𝐶𝐶𝐷𝐷 − 0.019𝐶𝐶𝐸𝐸 + 0.044𝐷𝐷𝐸𝐸 (2) where, ra = surface roughness (µm), a = voltage open (v), b = off time (µs), c = wire speed (m/min), d = wire tension (n), and e = voltage gap (v). table 1: experimental parameters of wedm control parameters level factors i ii iii iv voltage open (v) a 10 12 14 16 off time (µs) b 1 2 3 4 wire speed (m/min) c 6 8 10 12 wire tension (n) d 6 7 8 9 voltage gap (v) e 40 45 50 55 fixed parameters: workpiece material stainless steel s304 tool electrode brass wire (ø 0.2 mm) dielectric fluid distilled water table 2: experimental result for average surface roughness and average kerf run process parameters performance measures voltage open (v) off time (µs) wire speed (m/min) wire tension (n) voltage gap (v) average surface roughness ra (µm) s/n value average surface roughness average kerf (mm) s/n value average kerf 1 14.00 3.00 6.00 7.00 55.00 3.22 -10.1571 0.274 11.2450 2 10.00 3.00 10.00 8.00 50.00 3.13 -9.9109 0.268 11.4373 3 14.00 4.00 8.00 6.00 50.00 2.05 -6.2351 0.277 11.1504 4 16.00 3.00 8.00 9.00 40.00 2.79 -8.9121 0.28 11.0568 5 12.00 3.00 12.00 6.00 45.00 3.45 -10.7564 0.245 12.2167 6 12.00 2.00 6.00 9.00 50.00 3.11 -9.8552 0.269 11.4050 7 14.00 2.00 12.00 8.00 40.00 3.44 -10.7312 0.293 10.6626 8 16.00 4.00 6.00 8.00 45.00 2.96 -9.4258 0.272 11.3086 9 16.00 2.00 10.00 6.00 55.00 2.73 -8.7233 0.274 11.2450 10 10.00 2.00 8.00 7.00 45.00 2.72 -8.6914 0.274 11.2450 11 10.00 4.00 12.00 9.00 55.00 3.86 -11.7317 0.278 11.1191 12 16.00 1.00 12.00 7.00 50.00 3.51 -10.9061 0.284 10.9336 13 12.00 4.00 10.00 7.00 40.00 2.97 -9.4551 0.274 11.2450 14 14.00 1.00 10.00 9.00 45.00 3.01 -9.5713 0.192 14.3340 15 10.00 1.00 6.00 6.00 40.00 2.82 -9.0050 0.282 10.9950 16 12.00 1.00 8.00 8.00 55.00 3.09 -9.7992 0.265 11.5351 table 3: s/n ratio means for ra process parameters s/n ratio mean delta rank level 1 level 2 level 3 level 4 voltage open (v) -9.8347 -9.9665 -9.1737 -9.4918 0.7928 4 off time (µs) -9.8204 -9.5003 -9.9341 -9.2119 0.7222 5 wire speed (m/min) -9.6108 -8.4094 -9.4151 -11.0314 2.6220 1 wire tension (n) -8.6799 -9.8024 -9.9668 10.0176 1.3377 2 voltage gap (v) -9.5258 -9.6112 -9.2268 10.1028 0.8760 3 analysis of wedm process parameters on surface roughness and kerf using taguchi method 106 table 4: anova for average ra source sum of square degree of freedom (df) mean square f value prob> f percetage contribution (%) model 2.56 12 0.21 102.38 0.0014 a 0.12 1 0.12 55.36 0.0050 5.82 b 0.16 1 0.16 77.57 0.0031 7.76 c 9.364e-004 1 9.364e-004 0.45 0.5508 0.045 d 3.491e-005 1 3.491e-005 0.017 0.9052 1.69e-3 e 0.026 1 0.026 12.62 0.0380 1.26 ab 0.098 1 0.098 47.14 0.0063 4.75 ac 0.14 1 0.14 69.43 0.0036 6.79 bd 0.54 1 0.54 259.29 0.0005 26.19 be 0.040 1 0.040 19.05 0.0222 1.94 cd 0.061 1 0.061 29.29 0.0124 2.96 ce 0.48 1 0.48 231.98 0.0006 23.28 de 0.39 1 0.39 185.59 0.0009 18.91 residual 6.256e-003 3 2.085e-003 cor total 2.57 15 total 2.062 15 standard deviation 0.046 r2 0.9976 mean 3.05 adjusted r2 0.9878 coefficient of variation 1.50 predicted r2 0.8133 predicted residual error of sum of square (press) 0.48 adequate precision 44.649 figure 1: effects of process parameters on mean s/n ratio for ra -15.00 -10.00 -5.00 0.00 level 1 level 2 level 3 level 4 wire speed banu et al., (2017): international journal of engineering materials and manufacture, 2(4), 103-109 107 3.2 kerf signal-to-noise (s/n) ratio. the equation used to calculate the average kerf is the same used for the average ra in order to attain better accuracy for the finish parts. figure 2 shows the effects of process parameters on mean s/n ration for kerf while table 5 shows the s/n ratio means for kerf. based on table 5 and figure 2, it shows that s/n ratio for kerf decreases when the level of voltage open and wire speed are at level 4 while wire tension is at level 2. however, according to previous research studies, it is inferred that kerf decreases when the wire tension increases. this is because wire vibration is expected to reduce with the increase of wire tension which will lead to reduction of kerf (16). conversely, the s/n ratio for kerf increases when the levels of off time and voltage gap are at level 1 and level 2 respectively. analysis of variance (anova). an empirical model as expressed in eqn. 3 is developed by anova. based on table 6, the model f-value of 68.71 implies the model is significant. there is only a 0.25% chance of noise that could occur in the model f-value. values of prob > f less than 0.0500 indicate model terms are significant. in this case b (off time), c (wire speed), d (wire tension), e (voltage gap), ab (voltage open and off time), ac (voltage open and wire speed), ad (voltage open and wire tension), bd (off time and wire tension), be (off time and voltage gap), ce (wire speed and voltage gap) are significant model terms. values greater than 0.1000 indicate the model terms are not significant. if there are many insignificant model terms (not counting those required to support hierarchy), then the model reduction may improve the model. factor a (voltage open) is the most uninfluenced factor and factor b (off time) is the most influenced factor. however, when factor a (voltage open) interact with factor b (off time), then it is significant. it is the same concept for ac (voltage open and wire speed) and ad (voltage open and wire tension). thus, it means that factor a (voltage open) cannot be removed as it is significant when there is an interaction with b (off time), c (wire speed), and d (wire tension) even though it is not significant if it is stand-alone. the predicted r2 and press are not defined. adequate precision measures the s/n ratio, where the ratio greater than 4 is desirable. the ratio of 36.342 indicates that the signal is adequate. this model can be used to navigate the design space. 𝐾𝐾𝐾𝐾𝐾𝐾𝐾𝐾 = 1.596 − 0.151𝐴𝐴 − 0.193𝐵𝐵 − 0.089𝐶𝐶 − 0.089𝐷𝐷 + 0.015𝐸𝐸 + 0.012𝐴𝐴𝐵𝐵 + 0.010𝐴𝐴𝐶𝐶 + 4.125 × 10−3𝐴𝐴𝐷𝐷 + 0.016𝐵𝐵𝐷𝐷 − 7.547 × 10−4𝐵𝐵𝐸𝐸 + 1.238 × 10−3𝐶𝐶𝐷𝐷 − 8.481 × 10−4𝐶𝐶𝐸𝐸 (3) where, kerf = kerf (mm), a = voltage open (v), b = off time (µs), c = wire speed (m/min), d = wire tension (n), and e = voltage gap (v). figure 2: effects of process parameters on mean s/n ratio for kerf 10.00 11.00 12.00 13.00 level 1 level 2 level 3 level 4 voltage gap 10.50 11.00 11.50 12.00 level 1 level 2 level 3 level 4 voltage open 10.50 11.00 11.50 12.00 12.50 level 1 level 2 level 3 level 4 off time 10.50 11.00 11.50 12.00 12.50 level 1 level 2 level 3 level 4 wire speed 10.50 11.00 11.50 12.00 12.50 level 1 level 2 level 3 level 4 wire tension analysis of wedm process parameters on surface roughness and kerf using taguchi method 108 table 5: s/n ratio means for kerf process parameters s/n ratio mean delta rank level 1 level 2 level 3 level 4 voltage open (vo) 11.1991 11.6004 11.8480 11.1360 0.7120 5 off time (µs) 11.9494 11.1394 11.4890 11.2058 0.8100 4 wire speed (m/min) 11.2384 11.2468 12.0653 11.2330 0.8323 2 wire tension (g) 11.4018 11.1671 11.2359 11.9787 0.8116 3 voltage gap (v) 10.9899 12.2761 11.2316 11.2860 1.2862 1 table 6: anova for average kerf source sum of square degree of freedom (df) mean square f value prob>f percentage contribution (%) model 7.838e-003 12 6.532e-004 68.71 0.0025 a 2.288e-005 1 2.288e-005 2.41 0.2186 0.16 b 2.700e-003 1 2.700e-003 284.05 0.0005 18.37 c 1.031e-003 1 1.031e-003 108.43 0.0019 7.01 d 1.232e-003 1 1.232e-003 129.62 0.0015 8.38 e 9.236e-004 1 9.236e-004 97.16 0.0022 6.28 ab 1.399e-003 1 1.399e-003 147.15 0.0012 9.52 ac 2.641e-003 1 2.641e-003 277.79 0.0005 17.97 ad 1.742e-004 1 1.742e-004 18.33 0.0234 1.19 bd 3.356e-003 1 3.356e-003 353.01 0.0003 22.83 be 1.817e-004 1 1.817e-004 19.12 0.0221 1.24 cd 7.827e-005 1 7.827e-005 8.23 0.0641 0.53 ce 9.407e-004 1 9.407e-004 98.96 0.0022 6.39 residual 2.852e-005 3 9.506e-006 cor total 7.866e-003 15 total 0.0147 15 standard deviation 3.083e-003 r2 0.9964 mean 0.27 adjusted r2 0.9819 coefficient of variation 1.15 predicted r2 n/a predicted residual error of sum of square (press) n/a adequate precision 36.342 4 multiple optimizations the anova-based optimization was done in order to get the optimum values of the process parameters for minimum ra and kerf. minimum ra (2.56 µm) and kerf (0.212 mm) can be achieved at 10 v voltage open, 2.84 µs off time, 12 m/min wire speed, 6.3 n wire tension, and 54.91 v voltage gap. experiments were conducted to validate the results obtained from the optimization. based on the experiment, the actual ra (2.76 µm) and kerf (0.23 mm) were higher compared to the optimize ra and kerf with maximum error of 7.81% and 8.49% respectively. the percentage error for minimum ra and kerf are relatively small which shows the empirical equations are valid. 5 conclusions in this paper, process parameters of wedm on surface roughness and kerf were analysed using stainless steel (s304) as the workpiece, brass wire as the tool electrode, and distilled water as the dielectric fluid. all of the process parameters that have been used for the investigation were found to have influence on the surface roughness and kerf. the following conclusions are drawn from the experimental study: 1. from s/n ratio, it can be inferred that wire speed, wire tension, and voltage gap should be at the highest level, which is level 4 while voltage open and off time should be at level 3 and 4 respectively to obtain low surface roughness. as for the kerf, it can be concluded that to get minimum kerf, voltage open and wire speed should be at level 4 while off time, wire tension, and voltage gap should be at level 2, level 2, and level 1 respectively. 2. based on anova, the most significant factor that influences the surface roughness and kerf is off time. 3. the minimum surface roughness and minimum kerf can be achieved when 2.56 µm at 10 v voltage open, 2.84 µs off time, 12 m/min wire speed, 6.3 n wire tension, and 54.91 v voltage gap are considered as the optimum process parameters for wedm of stainless steel. 4. the predicted value and experimental ra and kerf value are within 7.81% and 8.49% error respectively. banu et al., (2017): international journal of engineering materials and manufacture, 2(4), 103-109 109 references 1. singh, h., & garg, r. (2009). effects of process parameters on material removal rate in wedm. journal of achievements in materials and manufacturing engineering, 32(1), 70-74. 2. ali, m. y., khamarruzaman, s. n. z., & banu, a. (2017). investigation of kerf in micro wire electro discharge machining. in iop conference series: materials science and engineering, 184(1), 012033. 3. ali, m. y., karim, a. m., adesta, e. y. t., ismail, a. f., abdullah, a., & idris, m. n. (2010). comparative study of conventional and micro wedm based on machining of meso/micro sized spur gear. international journal of precision engineering and manufacturing, 11(5), 779-784. 4. durairaj, m., sudharsun, d., & swamynathan, n. (2013). analysis of process parameters in wire edm with stainless steel using single objective taguchi method and multi objective grey relational grade. procedia engineering, 64, 868-877. 5. nihat, t., can, c., & gul, t. (2004). a study on kerf and material removal rate in wire electrical discahrge machining based on taguchi method. journal of materials processing technology, 152(3), 316-322. 6. kumar, k. & ravikumar, r. (2013). modeling and optimization of wire edm process. international journal of modern engineering research, 3(3), 1645-1648. 7. ramli, r., ahmad, r., & ghani, j. a. (2012). kerf width optimization in wire-cut electrical discharge machine by using taguchi method. journal teknologi (sciences and engineering), 59(suppl. 2), 209-213. 8. liao, y. s., huang, j. t., & chen, y. h. (2004). a study to achieve a fine surface finish in wire-edm. journal of materials processing technology, 149(1), 165-171. 9. hoang, k. t. & yang, s. h. (2015). kerf analysis and control in dry micro-wire electrical discharge machining. international journal of advanced manufacturing technology, 78, 1803-1812. 10. ghodsiyeh, d., golshan, a., & shirvanehdeh, j. a. (2013). review on current research trends in wire electrical discharge machining (wedm). indian journal of science and technology, 6(2), 4128-4140. 11. di, s., chu, x., wei, d., wang, z., chi, g., & liu, y. (2009). analysis on kerf width in micro-wedm. international journal of machine tools & manufacture, 49(10), 788-792. 12. akkurt, a. (2009). surface properties of the cut face obtained by different cutting methods from aisi 304 stainless steel materials. indian journak of engineering & materials sciences, 16, 373-384. 13. taguchi, g. (1993). taguchi on robust technology development, bringing quality engineering upstream. new york: asme press. 14. jugulum, r. & samuel, p. (2010). design for lean six sigma: a holistic approach to design and innovation. john wiley & sons. 15. ali, m. y., mohamed, a. r., khan, a. a., asfana, b., lutfi, m., & fahmi, m. i. (2013). empirical modelling of vibration in micro end milling of pmma. world applied sciences journal (mathematical applications in engineering), 21, 73-78. 16. ikram, a., mufti, n. a., saleem, m. q., & khan, a. r. (2013). parametric optimization for surface roughness , kerf and mrr in wire electrical discharge machining (wedm) using taguchi design of experiment. journal of mechanical and science technology, 27(7), 2133-2141. microsoft word research paper 22 oct.docx international journal of engineering materials and manufacture (2019) 4(4) 164-169 https://doi.org/10.26776/ijemm.04.04.2019.04 characterisation of natural oils as carrier fluids for magnetorheological fluids ram rohit vannarth, raj dhake, s vishal kanna and safal sharad saraf received: 16 september 2019 accepted: 14 november 2019 published: 15 december 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract the field of application of magnetorheological fluids (mrf) is widening. the carrier fluids being used now are synthetic, expensive and non-biodegradable. hence, there is a need for looking for better and inexpensive alternatives. this study was intended to uncloak alternatives to the synthetic carrier fluids by taking four natural oils and conducting various tests. the four natural oils, viz, simarouba oil, mahua oil, groundnut oil, flaxseed oil and synthetic silicone oil were taken and tests concerning magnetorheological fluids like density, kinematic viscosity, flash and fire point, pour point, etc., were conducted according to standards in a licensed laboratory. based on the various tests conducted, the four natural oils have shown remarkable potential compared with commonly used silicone oil to be used as carrier fluids. keywords: magnetorheological fluids, carrier fluids, carrier fluid properties, inexpensive alternatives, natural oils 1 introduction magneto-rheology is a genre of rheology which addresses the research of flow behaviour and deformation of materials subjected to magnetic field. in 1949, jacob rabinow found magnetorheological (mr) liquids which are suspensions of non-colloidal (0.05-10 µm), multi-domain, magnetically soft particles in organic or water based liquids known as carrier fluids [1]. they comprise of magnetisable particles, non-magnetisable suspending fluids and additives [2]. the most common mr substances exist in the liquid state [3]. mr fluids conduct similarly, to newtonian fluids in the void of subjected magnetic field; under the influence of the external magnetic field, the behaviour of mr fluids can be outlined by the bingham plastic model [4]. the properties of these fluids (such as viscosity, yield stress, etc.) alter according to the exerted magnetic field. hence, they can be considered as smart materials [5]. the particles of mrfs are magnetically multi-domain, which induces a magnetic dipole in each particle, leading to strong forces being developed between the particles. hence, a network of particles is developed and the mrf changes to semi-solid state or viscoelastic solid from liquid state, temporarily. rheological attributes of magnetorheological fluids, for example, yield stress and apparent viscosity can be promptly monitored by applying a magnetic field [6]. hence, these fluids behaves like non-newtonian fluids under an external magnetic field [7]. for various applications of magnetorheological fluids (such as mr brakes, dampers, etc.), the response time of mrfs is quite significant. this response time has a range of 10–20 milliseconds, which depends on the design of the magnetic circuit. so, mrfs, for mechanical applications can illustrate dynamic yield stress up to 100 kpa, according to its flux density, amplitude and composition [5]. magneto-rheological fluid technology is now impressively applied in various low and high-volume applications, which have turned out to be advantageous commercially. conventional mrfs uses carrier liquids which has certain limitations such as high cost, nonbiodegradable and ease of availability has inspired us to look for alternative natural carrier fluid which is eco-friendly, available in plenty in india and are less expensive. in this paper, the properties of four natural fluidssimarouba oil, mahua oil, groundnut oil, and flaxseed oil as a potential carrier fluid is compared with silicone oil which is a standard carrier fluid. various tests have been conducted as per standards on these oils to compare the desirable properties such as fire point, flash point, etc. the influencing factors for considering natural carrier fluid of mr fluids were systematically discussed and analysed. ram rohit vannarth , raj dhake, s vishal kanna, safal sharad saraf department of mechanical engineering bms college of engineering, bangalore, india e-mail: ramrohit.mech@bmsce.ac.in reference: vannarth, r. r., dhake, r., kanna, v. and saraf, s. s. (2019). characterisation of natural oils as carrier fluids for magnetorheological fluids. international journal of engineering materials and manufacture, 4(4), 164-169. characterisation of natural oils as carrier fluids for magnetorheological fluids 2 materials and preparation 2.1 simarouba oil the seeds from the simarouba glauca tree hold around60 -75% of oil. the main uses of the oil is for the production of biodiesel, being edible it is widely used in preparation of bakery products, vegetable oil vanaspati and/or margarine. upon extraction of the oil, the seeds can be used as a binding agent for waste water treatment processes. for this study, simarouba seeds were collected from different part of karnataka, india from which the oil was extracted by cold-pressing the dried kernel of simarouba. 2.2 mahua oil the oil extracted from the seeds of the mahua tree (madhuca indica) is called mahua oil. the seeds are produced after a 10-11 year growth period of the mahua tree. the derivation of the oil from the sun-dried seeds was done by means of an expeller and the average yield is around 21 – 31 % per kernel. natural mahua oil were yellow in appearance since they are properly stored without any harmful preservatives whereas the commercial mahua oil was also yellow in colour but has a unbearable odour and taste because of the presence of excess fatty acids. 2.3 silicone oil any liquid polymerized siloxane with organic side chains can be acknowledged as silicone oil. the crucial member of the silicone oil structure is polydimethylsiloxane. the most efficient method of producing in which cross linked silicone particles are evenly scattered in amino-modified silicone oil was by the extraction of water from the liquid after mixing an aqueous suspension of cross-linked silicone particulates of mean diameters 0.1 to 500 µm to an aqueous mixture of amino based silicone oil having an mixture particle diameter lying in the range 0.05 to 100 µm [8]. 2.4 flaxseed oil flaxseed oil, also familiar as linseed oil or flax oil, is derived from the parched, matured seeds of the flax plant (linumusitatissimum) [9, 10]. most of the commercially grown flaxseed contains 20–25% protein per weight and 40-45% of oil. the flaxseed oil for comparison had been extracted from the cold pressing industry. flax for commercial use is squeezed and then boiled which is then exposed to a high temperature to commence oxidation and polymerization [11]. the flax obtained is crushed and pressed using a modern steel press to get the oil out. 2.5 groundnut oil groundnut oil, also known as arachis oil, is a bland taste vegetable oil derived from peanuts. the oil possesses an intense peanut flavour and odour [12]. the raw material required for the preparation of groundnut oil is groundnut seed. firstly, groundnut seeds are cleaned so that the oil was not contaminated. removal of the outer episperm was critical because it doesn't contain oil. for grinding processes seeds are not usually pressed whole since oil removal is more effective if the seed is in smaller proportions. heating was the concluding step for preparing the base substance for the extraction of oil. 3 experimental method 3.1 density test density is mass of the liquid per unit volume or it is also the compactness of the molecules of liquid measured at 15°c. a specific gravity bottle was used to measure density [13]. it was washed thoroughly by distilled water and acetone and then dried in the furnace for about 5 – 10 minutes. the weight of empty specific gravity bottle was taken as w1. the cylinder containing the sample in the vertical position was placed in a location free from air and weight of specific gravity bottle with the sample was taken as w3. finally, the weight of an empty specific gravity bottle containing distilled water was taken as w2 [14]. the experimental setup used for this test is as shown in the figure 1. density was measured as per is:1448 (part 16) [15]. density is then calculated by: (1) where, d = density (kg/m3), w1 = weight of empty specific gravity bottle (kg), w2 = the weight of an empty specific gravity bottle containing distilled water (kg), w3 = weight of specific gravity bottle with the sample (kg). 3.2 flash point and fire point the minimal temperature at which the test flame triggers the vapour above the sample to give a momentary distinct flash is called flash point and the temperature at which the oil ignites and continues to combust for no less than 5 seconds is called as fire point. the oil sample was placed in the cup of the pensky martens apparatus, as shown in figure 2, which was used to estimate the flash and fire point of the sample and then heated at a specific rate [16]. in this process, a limited test flame was directed on the cup periodically to ignite the oil sample. initially, the cup and the accessories are cleaned thoroughly for accurate values. thermometer and test fires are placed on the cup and usually, a high range of thermometer was used if the flashpoint of oil will be above 1050c. the temperature was increased gradually and the surface of the oil was checked for the phenomenon of flash and fire point. flash and fire point are measured as per is:1448 (part 66) [17]. 165 vannarth et al. (2019): international journal of engineering materials and manufacture, 4(4), 164-169 figure 1: experimental setup for density test as per is:1448 (part 16) standards. figure 2: experimental setup for flash and fire point test as per is:1448 (part 66) standards. 3.3 kinematic viscosity a device called as a viscometer is used to determine the kinematic viscosity and the principle on which it works is based on the fact that time of flow of a fluid of fixed volume is proportional to its kinematic viscosity at 40°c and 100°c. the viscosity was recorded through viscometer to which paraffin liquid was added to keep a check on the temperature and to evenly circulate the heat. the reading was taken once the particular temperature was reached and the time was taken until it reaches that level was measured using a stop clock in terms of seconds and it is called flow time which is denoted as “t”. the product of flow time and calibration constant (or viscometer constant which has a value of 0.0640) of the viscometer gives the kinematic viscosity [18]. the experimental setup used for this test is as shown in figure 3. kinematic viscosity was calculated as per is:1448 (part-25). kinematic viscosity t (2) where, t = flow time 3.4 viscosity index viscosity index gives how the oil will act at a particular temperature. higher viscosity index indicates a relatively minor change of viscosity with temperature [19]. viscosity index is a broadly employed and recognised criterion of the variability in kinematic viscosity due to changes in the temperature of the oil being used as a carrier fluid between 40°c and 100°c. it was calculated by taking the oils kinematic viscosity at 40oc as u and the oils viscosity at 100oc as l and h [20], the values of which can be obtained from the astm d2270 [21]. 𝑉𝑉𝑉𝑉 = 100 (𝐿𝐿−𝑈𝑈) (𝑙𝑙−𝐻𝐻) (3) where, v.i. = viscosity index, l = kinematic viscosity at 40°c of an oil of 0(zero) viscosity index possessing the same kinematic viscosity at 100°c as the oil whose viscosity index is to be calculated (cst), h = kinematic viscosity at 40°c of an oil of 100 viscosity index possessing the similar kinematic viscosity at 100°c as the oil whose viscosity index is to be computed (cst), u = kinematic viscosity at 40°c of the oil whose viscosity index is to be computed (cst). 3.5 pour point it is the temperature below which the flow characteristics of the liquid are lost. high pour point is usually associated with a high content of paraffin. warm oil sample (50ml) was taken in a 100ml beaker and placed in the refrigerator. in every 5 minutes interval, the beaker is inspected by holding it in a horizontal position for a couple of seconds before cooling back. the pour point was reached when the oil surface stays in a vertical position and when tilted for 5 seconds, does not sag. the thermometer was inserted at this point and the pour point is 3 degree celsius higher than the temperature reading on the thermometer. the experimental used for this test is as shown in figure 4. pour point was measured as per is:1448 (part10) [22]. pour point = x°c + 3°c (4) where, x°c = thermometer reading 166 characterisation of natural oils as carrier fluids for magnetorheological fluids figure 3: experimental setup for kinematic viscosity test as per is:1448 (part-25) standards. figure 4: experimental setup for pour point test as per is: 1448 (part-10) standards. 3.6 water content [karl fischer method] this test was employed to measure the water content in the oil by employing the chemical reaction between water with iodine and sulphur dioxide with methanol and an organic base such as pyridine. volumetric titration was employed for the determination of water content. a karl fischer reagent and methanol are used in the titration; 50 ml of ethanol was added in the titration vessel. the oil to be tested was taken in a syringe. an electromagnetic stirrer was used for thorough mixing and the karl fischer reagent was added till there was sudden and constant deflection for about 30 seconds. the oil in the syringe was introduced into the titration instrument and was titrated versus the karl fischer reagent to find the endpoint of the reaction. the readings noted give the water content. the experimental setup used for this test is as shown in figure 5. water content was measured as per astm d6 304 [23]. karl fischer reaction mechanism: ch3 oh + s o2 + (rn) <=> [rn h]so3 ch3 h2 o + i2 + [rn h] so3 ch3 + 2r n <=> [rn h] so4 ch3 + 2[rn h] i where, rn = base 3.7 sulphur content [advanced bomb calorimeter] this test was used to measure the sulphur content in the oil. the instrument used (bomb instrument) was prepared by cutting an ignition wire of 100mm length and is coiled in the middle. about 5ml of na2co3 solution was added and it was rotated such that the interior surface of the bomb was moistened by the solution. the required quantity of sample and white oil (liquid paraffin) is introduced. it was arranged in such a way that the sample was placed below the bomb. oxygen was then passed into the bomb instrument at the desired pressure. the bomb was submerged in a cold distilled water bath for ignition and the ends are connected to an open electrical circuit. the ignition was carried out by closing the circuit. the interior of the bomb instrument was rinsed thoroughly by a jet of water and the washing obtained is collected in a beaker. the beaker was heated just below the boiling point of the liquid present and to which conc. hcl and bacl2 drops are added and stirred well. the experimental setup used for this test is as shown in figure 6. sulphur content was measured as peris:1448 (part-33) [24]. 𝑆𝑆ulphur weight = (𝐴𝐴−𝐵𝐵)∗13.69 𝑤𝑤 (5) where, a = mass of barium sulphate from sample (g), b = mass of barium sulphate from blank (g), w = weight of the sample. 167 vannarth et al. (2019): international journal of engineering materials and manufacture, 4(4), 164-169 figure 5: experimental setup for water content test as per astm d6 304 standards figure 6: experimental setup for sulphur content test as per is:1448 (part-33) standards. table 1: properties of oils simarouba oil mahua oil silicone oil flaxseed oil groundnut oil test method kinematic viscosity @40°c (cst) 56.2 51.97 54.1 29.59 35.79 is:1448 (part25) kinematic viscosity @100°c (cst) 33.2 30.68 33.8 8.38 8.79 is:1 448 (part25) density@15°c (kg/m3) 968.14 958.85 961.79 924.89 916.92 is:1448 (part16) viscosity index 543.12 546.69 564.64 282.42 196.78 astm d2270 flash point (°c) 144 142 110 124 130 is:1448 (part66) fire point (°c) 150 144 114 126 132 - water content (%) 0.36 0.23 0.67 0.61 0.55 astm d6 304 sulphur content (%) 0.05 0.22 0.53 0.5 0.61 is :1448 (part33) pour point (°c) -15 -18 -12 -14 -10 is:1448 (part10) 4 results and discussions referring to table 1, we can say that the of the four natural carrier oils, mahua oil =958.85kg/m3, groundnut =916.92kg/m3, flaxseed oil=924.89kg/m3 have lower density compared with traditionally used silicone oil which has a slightly higher density, silicone oil=961.79kg/m3; exception being simarouba oil which has a higher density than silicone oil. the viscosity of oil is important for its cooling and lubricant properties. the four natural carrier oils have comparatively lower viscosity (at 40°c and 100°c) than silicone oil which results in faster cooling and better lubrication in mr fluids applications. natural oils have a lower viscosity index which indicates they require a lower temperature to reduce viscosity compared to silicone oil. flashpoint and fire point of oils demonstrates the likely presence of flammable materials in relatively non-flammable materials or non-volatile. the natural oils have a higher flash and fire point which prevents them from undergoing combustion at a lower temperature, which in turn makes them quite safer than silicone oil. water content is the amount of water present in the fluid in terms of the percentage of the composition. the more the water content in the base fluid, the more is the magnetorheological fluid stability but at price of being more corrosive. the natural oils have slightly less water content as compared to the silicone oil. hence, the magnetorheological stability would be slightly more in the case of silicone oil (0.67%). when considering the sulphur content there silicone and groundnut oils have higher values compared with the other oils, hence, the corrosion resistance decreases. pour point of simarouba (15°c) and mahua oils (-18°c) points out the oil's ability to flow in cold conditions. 5 conclusions the characteristics of the natural oils relevant to be used as carrier fluids for mr fluids have been studied in this research. among the four natural oils flaxseed, groundnut, mahua oil have significantly lower viscosity at both 400c and 1000c. since the viscosity of flaxseed oil is least (29.59 cst @40°c and 8.38 cst@100°c) it has the best mr 168 characterisation of natural oils as carrier fluids for magnetorheological fluids response among the five oils tested. the density of simarouba oil is 968.14kg/m3is greater compared to the traditionally used silicone oil which has density of 961.71 kg/m3, hence the sedimentation stability and yield of simarouba oil is more. both simarouba and mahua oils have low percentage of sulphur and water content, indicating they are less corrosive in nature. pour point temperature of simarouba (-15°c) and mahua oils (-18°c) are relatively low, hence they can be stored at such low temperature without them losing their flow ability. the flash and fire point of simarouba and mahua oil is high preventing them from undergoing combustion at a lower temperature, which in turn makes them quite safer than silicone oil. silicone oil is expensive and artificially synthesized oil whereas simarouba oil, mahua oil, groundnut oil and flax seed oil are comparatively inexpensive, easily available and biodegradable. thus, we can say that simarouba oil has the most desirable mr carrier fluid properties among mahua oil, flax seed oil and groundnut oil. hence simarouba oil show good potential as a base oil for mr fluids applications. references [1] a. muhammad, x. yao, and z. deng, “review of magnetorheological (mr) fluids and its applications in vibration control,” j. mar. sci. appl., 5 (3), 17–29, sep. 2006. [2] fernando d g and carlson j d in 10th int. conf. on er fluids, mr suspensions, 2006, 165. [3] m. r. jolly, “properties and applications of magnetorheological fluids,” mrs proc., 604, 167, feb. 1999. [4] j. q. zhang, j. zhang, and q. jing, “effect of seven different additives on the properties of mr fluids,” j. phys. conf. ser., 149, 012086, feb. 2009. [5] b. k. kumbhar, s. r. patil, and s. m. sawant, “synthesis and characterization of magneto-rheological (mr) fluids for mr brake application,” eng. sci. technol. an int. j., 18 (3), 432–438, sep. 2015. [6] m. ashtiani, s. h. hashemabadi, and a. ghaffari, “a review on the magnetorheological fluid preparation and stabilization,” j. magn. magn. mater., 374, 716–730, jan. 2015. [7] r. kciuk, monika and turczyn, “properties and application of magnetorheological fluids,” j. achiev. mater. manuf. eng., 18 (1–2), 2006. [8] a. phuly, “( 12 ) patent application publication ( 10 ) pub . no .: us 2012 / 0047830 a1,” 1, (19), 2012. [9] f. n. jones, “alkyd resins,” in ullmann’s encyclopedia of industrial chemistry, weinheim, germany: wileyvch verlag gmbh and co. kgaa, 2003. [10] s. rwahwire, b. tomkova, a. p. periyasamy, and b. m. kale, “green thermoset reinforced biocomposites,” in green composites for automotive applications, elsevier, 2019, 61–80. [11] p. kolodziejczyk, l. ozimek, and j. kozłowska, “the application of flax and hemp seeds in food, animal feed and cosmetics production,” in handbook of natural fibres, elsevier, 2012, 329–366. [12] x. liu et al., “changes in volatile compounds of peanut oil during the roasting process for production of aromatic roasted peanut oil,” j. food sci., vol. 76, no. 3, pp. c404–c412, apr. 2011. [13] r. ramachandran, s. balasubramanian, g. aridoss, p. parthiban, g. yamuna, and s. kabilan, “synthesis and studies of semiconducting piperazine–aniline copolymer,” eur. polym. j., 42 (8), 1885– 1892, aug. 2006. [14] n. j. john, p. selvarajan, s. b. j. silviya, and c. k. mahadevan, “growth and characterization of disodium hydrogen orthophosphate (dshp) single crystals,” mater. manuf. process., 22 (3), 379–383, mar. 2007. [15] bureau of indian standards, methods of test for petroleum and its products, part 16. 1990. [16] d. ravichandra, r. k. puli, and v. p. chandramohan, “production and comparison of fuel properties for various biodiesels,” 2019, 267–276. [17] bureau of indian standards, methods of test for petroleum and its products, part 66. 1969. [18] bureau of indian standards, methods of test for petroleum and its products, part 25. 1976. [19] j. speight and d. i. exall, refining used lubricating oils. crc press, 2014. [20] d. derawi et al., “palm olein as renewable raw materials for industrial and pharmaceutical products applications: chemical characterization and physicochemical properties studies,” adv. mater. sci. eng., 2014, 1–5, 2014. [21] astm, standard practice for calculating viscosity index from kinematic viscosity at 40 °c and 100 °c. 2016. [22] bureau of indian standards, methods of test for petroleum and its products, part 10. 2012. [23] astm, standard test method for determination of water in petroleum products, lubricating oils, and additives by coulometric karl fischer titration. 2016. [24] bureau of indian standards, methods of test for petroleum and its products, part 33. 1991. 169 international journal of engineering materials and manufacture (2023) 8(2) 36-50 https://doi.org/10.26776/ijemm.08.02.2023.02 a. a. saleh 1 , m. hasanuzaman 2 , h. cassidy 1 , s. h. dayang and m. shahril 1 1 centre for research of innovation and sustainable development, school of engineering and technology, university of technology sarawak, 96000 sibu, sarawak, malaysia 2 universiti malaya power energy dedicated advanced centre (umpedac), 59990 kuala lumpur, malaysia e-mail: abusaleh@uts.edu.my reference: saleh, a. a., hasanuzzaman, m., cassidy, h., dayang, s. h. and shahril, m. (2023). an exploration of modified microwave-assisted rapid hydrothermal liquefaction process for conversion of palm kernel shells to bio-oil. international journal of engineering materials and manufacture, 8(2), 36-50. an exploration of modified microwave-assisted rapid hydrothermal liquefaction process for conversion of palm kernel shells to bio-oil saleh, a. a., hasanuzzaman, m., cassidy, h., dayang, s. h., and shahril, m. received: 12 january 2023 accepted: 23 february 2023 published: 01 april 2023 publisher: deer hill publications © 2023 the author(s) creative commons: cc by 4.0 abstract bio-oil is one of the potential resources to address the sustainable energy development and environmental issues. microwave-assisted rapid hydrothermal liquefaction process is one of the popular techniques that is used to extract bio-oil from biomass. in this paper, the bio-oil has been extracted from palm kernel shells by using microwaveassisted and conventional heating pyrolysis processes. a modified heating mantle apparatus are used to conduct the experiment for extracting the bio-oil. the experiments are conducted by varying the hydrothermal temperature and time for both techniques to achieve the conversion of the bio-oil from the raw material. it is found that the yield of bio-oil for microwave-assisted rapid hydrothermal liquefaction process at 350°c and 400°c are from 10.70 wt% to 25.60 wt% within hydrothermal time 6, 9 and 12 minutes. the ph value of the bio-oil is acidic with the range from 3 to 4. the calorific value of the bio-oil is varied from 24 to 26 mj/kg for both conversion methods. fourier transform infrared spectroscopy (ftir) result reveals that multiple functional groups (alcohol, aldehydes, carboxylic acid and ketones) are present in the pks bio-oil. keywords: biomass; hydrothermal; bio-oil; microwave; heating value 1 introduction energy is one of the basic needs for economic growth, automation and modernization. there have been raising concerns about the world's use of fossil fuels with the increase in energy consumption. in addition to the industrial growth and standard of living, reliance on fossil fuels is gradually increasing. continuous consumption of fossil fuel has direct impact on environment [1]. renewable energy technology is clean and environment friendly. biomass is one of the most abundant and potential resources of energy around the world. biomass energy is defined as the utilization of organic materials to create energy. biomass can be converted to biofuel including bio-oil and biogas [23]. bio-oil is produced from multiple types of feedstock, such as palm kernel shells, karanja seeds, wood sawdust, sewage sludge, sugarcane etc. where the properties of bio-oil depend on feedstock characteristics and parameters of pyrolysis bio oil comprises a complex mixture of over 300 organic materials from aldehydes, esters, ketones, acids, alcohols and oligomers obtained from lignin. such chemical compositions in the oils offer significant characteristics to bio-oil production, which differs from conventional oils obtained from petroleum. some of the properties can lead to undesirable results, especially for certain applications like oil. the existence of these unfavourable properties has a negative impact that restricts bio-oil use in multiple applications. some of the physical properties are the content of oxygen and water, viscosity, corrosively, and ultimately the behaviour of combustion [4]. about 35-40% of oxygen present in the pyrolysis oil reduces the energy densities of the oil which is directly connected to the heating value [5]. water content in the oils has resulted in the feedstock's original moisture due to a dehydration reaction that occurred during the pyrolysis process ranging from 15% to 30%. the presence of water in bio oils lower the heating value and in the same time causes greater ignition delay which decreases the combustion rate especially in the engine [6]. however, the positive effects of water to reduce oil viscosity and leads uniform temperature profile as well as reducing the emission of nitrogen to the air. czernik and bridgewater [5] explained that although the oils are free flowing, its viscosity increases with time especially when it is handled at higher temperature. reactive components in pyrolysis oil such as aldehydes, phenols and ketones are subjected to secondary condensation and polymerization, leading to higher and higher viscosity levels. bio oils have acidic properties which could cause corrosion on materials modified microwave-assisted rapid hydrothermal liquefaction process for conversion of palm kernel shells to bio-oil 37 such as carbon steel and aluminium. at high temperatures, corrosiveness can get severe and increase the water content. high acidity can lead to very unstable bio oil. the ph quality for bio-oil varies from 2-3 and is the product of significant organic acids, mainly acetic acids and formic acids present in the feedstock. bio oil has a higher efficiency energy production compared to conventional biomass fuels, especially for heat and power generation. it is also viewed as carbon dioxide (co2) neutral due to lower sulfur and nitrogen gas content which can lead to lower greenhouse gas emissions [5]. due to growing in multiple types of biomass globally, great interest of research is among different kinds of biomass as renewable energy resources that provide many opportunities for bio-oil conversion for heat and power generation. palm kernel shell (pks) is one of the by-products produced from the palm oil milling operation but however is rapidly becoming an important supply of feedstock for biomass energy generation. although always traditionally used by palm oil mills as a source of energy, pastime from power generators is growing. given its excessive energy content (14-20gj/t) and the reality that it is a waste product. in asean countries such as thailand, malaysia and indonesia, the rapid development of palm oil industries leads to the abundance of these biomass sources increasing. pks is the shell fractions left after the nut has been eliminated and one of the fibrous materials. large and small shell fractions had been mixed with dust-like fractions and small fibres. by comparing pks with other biomass sources, the moisture content in the kernel shells is low suggesting values between 11% and 13%. the rapid hydrothermal process is one of the ways to transform biomass into bioenergy. microwave approach provides instantaneous heat and quick heating to convert agricultural waste into a product with added value. salema & ani, 2011 [7] reported that conventional heating methods has a lot of drawbacks compared to microwave pyrolysis. hydrothermal liquefaction process undergoes thermochemical decomposition in the absence of oxygen to transform biomass with high temperature. through the hydrothermal process, biomass produces biochar, volatile and bio-gas. during hydrothermal liquefaction process, three types of reaction named drying, primary reaction and secondary reaction occur. hydrothermal liquefaction process processing provides the atmosphere with greater efficiencies and less pollution. hydrothermal process is complex where biomass undergo many stages of decomposition which result various change in specific volume [8]. the concept of integrated bio-refinery is the unparalleled solution which comprise the generation of hydrocarbon grade fuels at a time with valuable products from the pyrolysis derived biooil [9]. many types of pyrolysis are practiced based on different condition. one of the modern pyrolysis techniques is the microwave assisted pyrolysis. microwave-assisted pyrolysis (map) is one of the current technologies emerging as one of many ways to turn biomass into high-quality and high market value products due to its emergence. it has become one of the hot topics among researcher that offers vast advantages compared to conventional pyrolysis that uses traditional electrical heating method [10]. problems such as slow heating and the need to minimize particle size in order to increase the heating speed can be solved by microwave pyrolysis. microwave pyrolysis can also help greatly to save energy and increasing the processing time of biomass production while at the same time improving the quality of bio char, bio gas and bio oil. microwave pyrolysis and bioenergy include the conversion of oil palm, wood, microalgae, corn stover and sewage sludge [11]. feedstocks do not need pre-treatment processes in microwave-assisted pyrolysis such as drying and grinding as feedstock heating can be driven through this technique. the moisture content that exists in the feedstock act as an adsorption material especially for irradiation as it can initiate the pyrolysis process [12]. in addition, decrease in feedstock size is always necessary when using conventional pyrolysis as contrast to microwaveassisted pyrolysis which can use feedstock's original size. zhang et al. 2017 [11] stated that conventional pyrolysis is highly dependent with the particle size of the feedstock as larger particle size produces low thermal conductivity and heat transfer thus creates a negative impact on the efficiency of bio-oil production. having the ability to increase the overall heat transfer and high yield of pyrolysis materials, tiny particles in conventional pyrolysis are always favourites given the lengthy pre-treatment process involving testing of biomass feedstock, elimination of moisture and reduction of size. microwave-assisted pyrolysis using microwave radiation as a heat source to transform electromagnetic energy to heat energy. heat can be generated in microwave-assisted pyrolysis due to the ability of the microwave that can penetrate through the feedstock thus providing energy without the need of using external source of energy [13]. the heat interaction would create a temperature gradient that occurred because of the feedstock's poor thermal conductivity, thereby spreading the volatile material from the inside to the outside surface from the higher temperature region to the lower temperature region. using microwave radiation can ensure uniform heat distribution, high heating efficiency with better heat transfer, rapid internal heating and speed up bio-oil production. microwave-assisted pyrolysis shows about 90 percent of the operating efficiency in terms of converting electricity into thermal energy and providing high-powered heat source. microwave-assisted pyrolysis offers more reliable process and are less costly in comparison to conventional heating method [14]. during the pyrolysis process, high heating rates and pyrolysis temperature can always be reached as well as shorter residence time if microwave absorbents are mixed with feedstock for biomass. this is due to the ability of microwave absorbents to absorbs the microwave energy and conveyed it to the poor absorbing material [15]. although microwave absorbents are great material that would help in increasing the pyrolysis end product especially bio-oil, however, the possibility for the volatile matter to enter secondary reactions where the vapour would break down into non-condensable gases are high due to sudden elevated temperature during the process which could reduce the yielding of bio-oil [11]. zhang et al. 2017 [11] stated that there are few methods that can be used in mixing the feedstock with microwave absorbent. the first approach is to mix the absorbent microwave with feedstock of biomass before starting the microwavesaleh, a. a. et al. (2023): international journal of engineering materials and manufacture, 8(2), 36-50 38 assisted pyrolysis because non-uniform mixing might occur throughout the pyrolysis process as both the microwave absorbent and feedstock have different bulk density and also the feedstock of the smaller particles would drop and remain at the bottom of the mixing plate. in order to improve heat transfer, the absorbent bed agitation is required as it facilitates uniform mixing between the absorbent surface of the microwave and the feedstock of biomass. catalyst may be used to boost microwave pyrolysis bio-oil yield. catalytic pyrolysis has been studied to improve the quality of pyrolysis liquid and decrease yield of non-condensable gases [16]. catalyst reaction such as metals (al or cu), metal oxides (cao, mgo, hzsm-5, etc.), metal salts (nacl, kcl, naoh, etc.) and acids can be used for biooil production in microwave pyrolysis. usually, microwave-assisted pyrolysis reaction catalysts are metals (al, fe, cu), metal oxides (cao, mgo and fe2o3), metal salts and acids (h2so4). catalytic microwave-assisted pyrolysis offers a number of benefits over normal microwave-assisted pyrolysis in terms of pyrolysis performance and efficiency. bio oil produced from fast pyrolysis must not contain any oxygen, hence the use of catalyst throughout the process of pyrolysis. catalysts effectively remove oxygen from the feedstock of biomass and thus improve the properties of the bio-oil itself. there approaches when utilize the usage of the catalysts namely catalytic cracking and hydro treating (liu et al., 2014) [6]. to counter these undesirable properties obtained, the process has been modified to fully utilize the used catalyst properties that can be separated into two processes that are both in-situ and ex-situ. in-situ catalytic process involves combining catalysts as well as feedstock in the reactor together. ex-situ catalytic process involves separation of catalyst from the feedstock before being placed onto the secondary reactor generally known as catalytic bed at which the primary pyrolytic vapours pass through it [17]. there are many factors that effect on pyrolysis of biomass feedstock. the yield of the pyrolysis product mainly depends on the characteristic of the biomass feedstock and the procedure parameters of temperature, microwave power, pyrolysis time, biomass feedstock characteristic etc. temperature can have a major impact on the biomass feedstock pyrolysis. temperature influence on bio oil distribution pyrolysis from 500°c to 800°c [18]. nonetheless, the use of microwave-assisted pyrolysis is to ensure that the feedstock of biomass undergoes decomposition at lower temperature faster in order to achieve maximum bio-oil yield compared to conventional heating process. nevertheless, different heating temperatures during microwave-assisted pyrolysis can affect the characteristics of biooil [19]. xie et al. 2014 [20] studied that at temperature between 450°c to 650°c was experimented to determine the percentage of bio-oil yield. the yield of bio char decreased and the yield of biogas increased as the temperature rose. the temperature increase has also resulted in a high yield of pyrolysis oil and the maximum yield of pyrolysis is around 550°c. the increase in the yield of pyrolysis oil is due to solid devolatilization, depolymerisation, and decarboxylation, which has been promoted by high temperatures since more energy has been involved in chemical reactions. the energy increase may break the strong organic bonds as well as release more volatiles to create condensable gas. that is also the reason why bio char decreases and biogas temperature increases. the reduction in bio-oil yield, however, occurs after 550°c. this is due to the process of secondary pyrolysis once the temperature reaches 550°c. too high temperature undergoes a secondary stage of pyrolysis that makes condensable volatile convert to non-condensable gasses and decreases pyrolysis oil yield when the temperature of the pyrolysis reaches 550°c [21]. microwave power is used to adjust the microwave-pyrolysis process temperature. increased microwave power level and increased cavity microwave density, resulting in increased microwave energy absorption by biomass feedstock. the increased microwave energy absorption of biomass feedstock creates a stronger interaction between biomass feedstock and microwave field. song et al. 2017 [22] mentioned that the changes of microwave power level on tire powder using microwave pyrolysis can affect bio oil yield. the result showed that the yield of pyrolysis liquid increased and that high microwave power was attributed to a high temperature of pyrolysis that could produce more liquid pyrolysis. the pyrolysis time for bio-oil production is included in the microwave pyrolysis parameter. it is the contact time between the feedstock of biomass and the region of microwave. the time of pyrolysis is described as the time between the feedstock of biomass starts to decompose and the pyrolysis process is completed. once starting to heat biomass feedstock inside the microwave oven, the time required to achieve the desired temperature of pyrolysis starting from the original time. the difference between the time of pyrolysis and the required time of pyrolysis is called the time of residence. residence time is important because it shows the actual time of pyrolysis in the biomass feedstock microwave pyrolysis. low yield of coal, lower yield of pyrolysis oil and low yield of bio char develop at longer times of residence. wang et al. 2015 [23] studied that utilize calluna vulgaris in microwave pyrolysis to determine bio oil yield at various pyrolysis times. if the time of pyrolysis increases from 1 to 10 minutes, the production of pyrolysis oil increases. it is because longer pyrolysis time can be produced to ensure that biomass raw materials undergo maximum pyrolysis process and high volatility. in fact, if residence time increases more, the yield of bio-oil decreases. because of the residence time increases more; the temperature becomes too high, resulting in condensable vapours being exposed to secondary reactions to form non-condensable gas. for microwave pyrolysis, an optimal residence time must be set, but the optimum residence time must be various by the other parameters. microwave pyrolysis is characteristic of biomass feedstock. moisture content in raw materials from biomass can act as an absorbent microwave because water can act as high absorbents of microwaves. increasing the moisture content also led to high bio-oil yields as microwave absorption of biomass feedstock increased. however, for microwave heating, high moisture content of biomass feedstock is not a fine parameter. throughout microwave heating, the biomass feedstock temperature will increase, and the moisture content would evaporate. loss of moisture content can impact raw materials from biomass, resulting in lower microwave absorption and lower heating levels. higher moisture content modified microwave-assisted rapid hydrothermal liquefaction process for conversion of palm kernel shells to bio-oil 39 can result in high tangent value in the feedstock of biomass. although the content of moisture in biomass raw materials can improve the process of microwave pyrolysis and maximize the production of bio-oil, the bio-oil is diluted due to high content of moisture in pyrolysis oil [24]. the main aim of this research is to analysis the effect of different parameters to extract bio-oils from palm kernel shell, to compare the yield of bio-oil produced and to characterize the bio-oil production by using microwave-assisted rapid hydrothermal liquefaction and conventional heating processes. 2. materials and methodology 2.1 experimental setup 2.1.1 biomass feedstock in this experimental work, the agricultural waste from palm farms, pks, was used as biomass feedstock which is widely found in malaysia and neighbouring regions. the pks samples were collected from ensengei palm oil mill, samarahan, sarawak, malaysia. firstly, to remove the moisture content, the pks samples were dried in a oven (panasonic nn-st342m) for 2 hr at 105 °c and then crushed to a smaller size of particle sizes around 212–300 μm, 300–600 μm, 600μm–1, 18 mm, and 1, 18–2, 36 mm by using a crusher (kenwood multifunction). pks has a high density of energy and solid biofuel of high grade. high calorific value, low sulfur content, excellent year-round availability, simple handling and crushing, minimal biological activity due to the low moisture content and no variety in species are features of pks. 2.1.2 microwave assisted rapid hydrothermal liquefaction process schematic of microwave-assisted experimental set up for pyrolysis was shown in figure.1(a). a panasonic nn-st342m microwave oven (max. power of 800w and frequency of 2450mhz) was modified to allow the drying and pyrolyzing the agricultural waste. at the top-centre of the microwave oven a hole of 40 mm diameter was made. a quartz reactor with tube size of 40 mm diameter, height of 250 mm and the socket size of c24/29 was mounted on the microwave oven and supported using a retort stand. a thermocouple (extech, usa) was employed for measuring the sample temperature. a t-shaped connector with c24/29 socket was used to link the quartz reactor gas outlet to the liebig condenser fitted with water cooling system. the other end of the liebig condenser was connected by l-shaped connector with c24/29 to 3 necks collecting flask. the experiment was conducted by placing samples of small particles in the quartz reactor and then put inside the microwave oven. standard procedures and safety precautions were adopted to prevent leakage of microwave radiation to the surroundings figure 1(b) shows the modified microwave-assisted experimental set up for hydrothermal liquefaction process in the lab. 2.1.3 conventional heating pyrolysis the schematic and set-up for conventional heating pyrolysis was shown in figure 2 (a & b). a 250ml round bottom borosilicate-glass flask was mounted on a 360w heating mantle and was attached to a t-shaped connector. to check the temperature inside the flask, a thermocouple with multimeter (digital, extech, usa) was inserted at the top of the t-shaped connector. further, a liebig condenser was connected to a t-shaped connector. the liebig condenser outlet is connected to an l-shaped connector and a collecting flask as well. similarly, to the modified microwave, the gas vapor which flows from the flask to the liebig condenser is condensed using a water-cooling system. the collecting flask collects oil settle from the condenser and its weight was measured and recorded. figure 1(a): schematic of modified microwave-assisted experimental set up for hydrothermal liquefaction process. (1) microwave oven, (2) quartz reactor, (3) digital multimeter and thermocouple, (4&6) liebig condenser (5) necks collecting flask. saleh, a. a. et al. (2023): international journal of engineering materials and manufacture, 8(2), 36-50 40 figure 1(b): modified microwave-assisted experimental set up for hydrothermal liquefaction process figure 2(a): schematic of conventional heating hydrothermal liquefaction process experimental set-up. (1) heating mantle, (2) round bottom flask, (3) digital multimeter and thermocouple, (4) liebig condenser, (5) three necks collecting flask figure 2(b): experimental set-up of conventional heating hydrothermal liquefaction process modified microwave-assisted rapid hydrothermal liquefaction process for conversion of palm kernel shells to bio-oil 41 2.1.4 microwave assisted rapid hydrothermal liquefaction process the sample of agricultural waste was sewed meshed into a small particles and feed into the quartz reactor. to avoid gas leakage during the pyrolysis process, all holes of equipment was covered by aluminium foil. the experiment was conducted by inserting 20 grams of pks samples in a quartz reactor and inserting them in a modified microwave oven. the optimal microwave oven power level for this experiment is 800 w. the experiment was repeated thrice for three pyrolysis process time 6 min, 9 min and 12 min. the bio oil was collected in a three-neck collecting flask from the volatile substance produced and equipment was washed with dichloromethane. while the carbonaceous residue (char) was directly obtained from the quartz reactor. the yield of bio-char and bio-oil were measured by their weight and the yield of gas was calculated by weight difference. 2.1.5 conventional heating process 20 gr of pks sample feedstock was fed into the 250ml round bottom flask and kept on top of the heating mantle. digital multimeter thermocouple was connected from top to the t-shaped connector and properly sealed to measure the temperature inside the flask. the heating mantle was then set to a maximum level of 10 and can be adjusted according to the desired temperature. in this work temperature for conventional pyrolysis was set at 350°c, 400°c, and 450°c meanwhile the conventional pyrolysis time was set at 30 min, 40 min and 50 min for each of the temperature. volatile substances were collected and condensed in the collecting flask and yielded bio oil weight was measured. 2.1.6 yield calculation of bio oil, bio char and bio gas the mass of pks feedstock samples was measured before starting of the experiment, while the mass of the bio oil yielded at the end. the following eq. (1) (3) [25-27] were adopted to calculate yield of bio oil, bio char and bio gas. bio-oil yield: ybio-oil = mbio-oil/msample ×100% (1) where, mbio-oil = mass of the bio-oil produced after pyrolysis process msample = mass of the biomass feedstock before starting of pyrolysis process bio char yield: ybio char = mbio char/msample ×100% (2) where, mbio char = mass of the bio char obtained from pyrolysis process msample = mass of the biomass feedstock before starting of pyrolysis process bio gas yield: ybio gas = 100% ybio-oil ybio char (3) 2.1.7 characterization of bio oil properties: the bio oil samples obtained from both microwave-assisted and conventional heating methods were analysed to determine their properties. fourier transform infrared spectroscopy (shimadzu, iraffinity-1) was employed to analyse the bio-oil functional groups over a 4000 to 500 cm−1 region. the calorific value of the produced bio-oil was determined using a bomb calorimeter (parr 6400). ph value of the bio-oil was measured by a ph meter (star121, orion). the energy properties of bio oil were determined by measuring bio-oil's heating value through higher heating value (hhv) and lower heating value (lhv) as well. a bomb calorimeter was used measure hhv. heat that is removed during the process of combustion in a condensed state is referred as hhv, whereas lhv is related to the combustion that is based on gaseous water as the product [28]. multiple ways exist to calculate the value of hhv and most of them depend on the composition of c, h, n and s. basically, on how these four composition oxidise into their respective products during combustion process whereas the other correlations mainly assuming that the hhv of bio-oil is directly proportional to oxygen since combustion requires oxygen to ensure complete process [29]. hhv value was calculated following the eq. (4), (5) and (6). hhv = 0.3491ƞc + 1.1783ƞh + 0.1005ƞs – 0.1034ƞo – 0.0151ƞs – 0.0211ƞash (4) hhv = 0.3382ƞc + 1.4428(ƞh – 0.125ƞo) (5) hhv = lhv + 21.978 ƞh (6) where: hhv = high heating value of bio-oil (mj/kg) lhv = low heating value of bio-oil (mj/kg) ƞc = weight percentage of carbon content of bio-oil (%). ƞh = weight percentage of hydrogen content of bio-oil (%). ƞo = weight percentage of oxygen content of bio-oil (%). ƞn = weight percentage of nitrogen content of bio-oil (%). ƞash = weight percentage of ash of bio-oil (%). saleh, a. a. et al. (2023): international journal of engineering materials and manufacture, 8(2), 36-50 42 3 results and discussions impact of hydrothermal process time and temperature on bio oil yield were analysed and illustrated. 3.1 physical appearance bio-oil the bio-oil was extracted from pks by using microwave-assisted hydrothermal liquefaction process and conventional heating. in microwave assisted hydrothermal experiments were conducted at 350°c and 450°c for a period of 6 minutes, 9 minutes. and 12 minutes. while in conventional heating process, 350°c, 400°c and 450°c with pyrolysis time of 30 minutes, 40 minutes and 50 minutes respectively. the bio-oil obtained from both of the conversion method is in light orange colour and bio-char are in black colour. figure 3 shows sample of bio-char and bio-oil obtained from experiment. figure 3: samples of bio-char and bio-oil obtained from experiment 3.2 yield of different fraction 20 grams samples of palm kernel shells (pks) have been used for all the process to occur for each run of the experiment. each of the following discussion will be based on the yield of the product obtained from 20g of the palm kernel shell (pks) and based on their respective methods. palm kernel shell’s total product yield is described and presented in tables 2 and 3. biogas results was a very challenging task to be collected and calculated due to the difficulty to capture the vapour during conversion, so the percentage yield of biogas was determined by the difference of 100 percent with the amount of both bio-oil yield and bio char. while others, it was measured directly in the case of the bio-oil and bio char, as the quantity of raw material is kept constant. apart from that, figure 4 and figure 5 displayed the analysis of the difference fraction performed through microwave-assisted and conventional heating for the product yield. 3.3 hydrothermal under microwave heating assistance the percentage yields of bio-oil from palm kernel shells are presented in table 1 and figure 4. table 1 displays the results collected and measured to calculate the yield of bio-oil at 350°c and 450°c while pyrolyzing the palm kernel shells under microwave heating assistance. the highest percentage yield for bio-oil is 25.60 wt% at 9 minutes with temperature 450°c while the lowest recorded bio-oil yield is around 10.70 wt% during 6 minutes with temperature 350°c. and the other by-product formed through hydrothermal is bio char, which is the carbonaceous residue and biogas as well. each of these products showed a maximum yield of 49.35 wt% and 54.65wt% within 6 and 9 minutes, respectively, at the same temperature of 350°c. and it is clear in figure-4 that the yield for bio-oil slowly increased with an increase in pyrolysis temperature. when pyrolysis temperature is 350°c, the yield ranged from 10.70 wt% to 21.30 wt%, while the yield was 17.65 wt% to 25.60 wt% during hydrothermal temperature 450°c. both temperatures show the highest percentage yield when the raw materials undergo 9 minutes of hydrothermal time, indicating that both temperatures have reached an optimum value at 9 minutes. however, yield dropped after the period goes beyond 9 minutes. this proves that the microwave-assisted pyrolysis needs specific times and temperatures to achieve an optimal bio-oil yield. microwave-assisted pyrolysis at that same temperature of 450°c recorded the highest bio-oil yield for 25.60 wt% and yielded lower bio-char. modified microwave-assisted rapid hydrothermal liquefaction process for conversion of palm kernel shells to bio-oil 43 table 1: product yield of palm kernel shells at different pyrolysis time and temperature using microwave-assisted hydrothermal liquefaction process. temperature (°c) time (min) bio-oil (wt%) bio-char (wt%) bio-gas (wt%) 350 6 10.70 49.35 39.95 9 21.30 24.05 54.65 12 16.30 29.55 54.15 450 6 23.81 27.62 48.57 9 25.60 25.12 49.28 12 17.65 33.45 48.90 3.4 conversion under conventional heating this experiment involving conventional heating pyrolysis, a modified conventional heating method in research methodology is being used to extract bio-oil from palm kernel shells. after that, the yields of the bio-oil and byproduct such as bio-char and bio-gas are being calculated. all 3 different yields from palm kernel shells through conventional heating process are tabulated and presented in table 1 at pyrolysis temperatures of 350°c, 400°c as well as 450°c. figure 5 shows the total product yield obtained via conventional heating pyrolysis. the yields of biooil ranged from 11.13 wt% to 36.07 wt%, referring to table 1. it's also observed that the highest bio-oil yield resulted at 400°c instead of 450°c as the percentage decreases to a range of 11.13 wt% -13.03 wt%. violent reaction to thermal decomposition takes place at a higher temperature which could induce secondary pyrolysis that yielded more biogas than bio-oil. presented in figure 5, result generated and demonstrated here that product yield for bio-oil kept increasing as the temperature and time also increased, but there was a slightly decrease in the bio-oil yield as the pyrolysis temperature exceeded 450°c while the yield for bio-char and bio-gas increased marginally with inconsistencies. it’s recorded that maximum bio char and biogas was 63.97 wt% and 50.45 wt% respectively. on the basis of the tabulated data and the graph, it can be obviously found that the highest bio-oil yield from the palm kernel shell can be obtained when the pyrolysis temperature is 400°c and the pyrolysis time is 40 minutes, as it yields 36.07 wt% of bio-oil. in addition, the yield of the bio-char as well as bio-gas is also low at this pyrolysis temperature, for only 40.62 wt% and 23.31 wt% respectively. figure 4: overall product yield of microwave-assisted pyrolysis saleh, a. a. et al. (2023): international journal of engineering materials and manufacture, 8(2), 36-50 44 table 2: product yield of palm kernel shell at different pyrolysis time and temperature using conventional heating. temperature (°c) time (min) bio-oil (wt%) bio-char (wt%) bio-gas (wt%) 350 30 15.42 46.48 38.1 40 22.47 63.97 13.56 50 29.01 46.8 24.19 400 30 32.09 47.67 20.24 40 36.07 40.62 23.31 50 31.48 42.5 26.02 450 30 11.27 33.28 50.45 40 13.03 55.83 31.14 50 11.13 56.72 32.15 figure 5: overall product yield of conventional heating process 3.5 factors affect different conversion there have been various key parameters that need to be understood in order to obtain optimum conversion of pksinto bio-oil. therefore, the two conversion methods used in this research are being evaluated and analysed using various types of parameters simultaneously to determine the efficiency and optimum parameters for extracting biooil from the palm kernel shells. different parameters are chosen being used for each experiment and the impact of such parameters will then be discussed in detail towards the yield of the product. factors which affect the method of conversion are a) conversion temperature and b) conversion time. 3.5.1 effect of conversion temperature the temperature of conversion is one of the significant parameters that impact bio-oil production. for the biomass feedstock it needed the optimum temperature to decompose and generate its by-product. the experiment was performed at 350°c and 450°c respectively, and its objective is to investigate the bio-oil yields obtained from microwave-assisted pyrolysis at different pyrolysis temperatures. based on figure 6, it could be seen that once the temperature of conversion increased from 350°c to 450°c, the yield of bio-oil increased from 10.70 wt% to 25.60 wt%. apart from that, as the temperature rose to 450°c, a gradual decrease in the yield of the bio char was recorded, while the yield of bio gas slowly increased with high temperatures but was still below the acceptable yield. the experiment proves that the minor decreases in the product yield of bio-char, and it can also be obviously indicated from the graph that bio-gas yield increases due to secondary reactions that favoured the generation of noncondensable gas than bio-oil when temperature rises. this condition was confirmed as zhang at al. 2017 [11] reported that carbon dioxide and water content were in an endothermic reaction, thus enhancing the conversion of condensable vapours to non-condensable gasses during second reactions at higher pyrolysis temperature. modified microwave-assisted rapid hydrothermal liquefaction process for conversion of palm kernel shells to bio-oil 45 figure 6: bio-oil yield for microwave-assisted hydrothermal in different temperature throughout this study, it can be found that it produces maximum bio-oil when the temperature is at 450°c that implies it is within the range of optimum conversion temperature (300°c 600°c). nevertheless, the yield of bio-oil decreases after the optimum temperature has been reached, which indicates that the pyrolysis is affected by temperature. microwave-assisted hydrothermal provides quite consistent thermal distributions, since microwave heating is the energy transfer rather than transfer of heat. during microwave-assisted hydrothermal, the microwave transmitted further into particle of the feedstock and this energy, which is radiated from the microwave, is converted into heat, thereby producing a temperature gradient from the inside to the outside. then the area surrounding is lower than inside of the feedstock particle as heat is continuously stored inside the feedstock until it is transferred to the outside part of the particle. so, mainly as a result of heat loss here on particle surface, the feedstock can decompose and release volatile substances at lower pyrolysis temperature area. referring to figure 6, it illustrates the results of bio-oil yield for conventional heating process in different temperature. it demonstrates similar patterns in conventional heating process, as well as in the microwave-assisted hydrothermal. the production of palm kernel shell pyrolysis product (pks) from different temperatures can be seen in figure 6. as referring to the figure 6, the yield of bio-oil increases as the temperature rises, but it shows a sharp decrease in yield at 450°c. the yield of bio char and biogas display a similar characteristic once the temperature rises from 350°c to 450°c, and both of those products decrease when the temperature rises from 350°c to 400°c but when it reaches its peak temperature of 450 °c, the yield rises to 56.72 wt% and 50.45 wt% respectively. similar with microwaveassisted pyrolysis, it can also be clarified that now the increased yield of bio char and biogas could be due to secondary thermal decomposition, leading to a lower yield of product at 11.13 wt%. bio-oil production was related to the devolatilization and depolymerization of organic matter where higher temperatures were needed to break their organic bonds, and this is claimed that thermal cracking at higher temperatures became more significant [13]. through convection, conduction and radiation, the heat transfer occurs from high temperature gas to the surface of the feedstock particle, thereby further transferring the heat energy into the inner core. because of the low thermal conductivity of the feedstock material during conventional heating, it is therefore possible to transfer volatile matter at a higher temperature region in achieving its desired temperature gradient from inside of the feedstock towards the outside surface. 3.5.2 effect of pyrolysis time one of the most key parameters for transforming biomass into bio-oil, bio-char and bio-gas is conversion time. to achieve a proper and complete conversion cycle, the interaction between the heating and the biomass feedstock must be controlled. different heating times were set for each conversion process in this section to determine the optimum product yield it can obtain throughout the time period that has been set. figure 7 illustrates the product yield of microwave-assisted pyrolysis during the conversion time for each experiment is maintained constant (6, 9, and 12 minutes). figure 8 has shown the product yield for conventional heating process when the conversion period in each experiment run is 30, 40, and 50 minutes. in both figures we can note that the product yield is a similar trend in the result. as the conversion period increased, the yield of the product as well increased until at some stage. based on figure 7, the maximum product yield was observed is during conversion time 9 minutes, which results in a bio-oil yield of 25.60 wt%, but once the microwave heating exceeds 9 minutes, it decreases to 17.65 wt%. the bio char yield increased while the pyrolysis time was 12 minutes (33.45 wt%), but in the case of biogas, it is different to the research results of the bio char since it gives a slightly reduced percentage yield of 48.90 wt% compared to the 9 minutes yield (49.28 wt%). it takes a cycle of pyrolysis to be lengthy enough to allow a complete pyrolysis process and to release more volatiles to form the pyrolysis oil. since the microwave heating is much more efficient and the maximum temperature can be achieved at a faster rate, the pyrolysis times are generally within 6 to 12 minutes. saleh, a. a. et al. (2023): international journal of engineering materials and manufacture, 8(2), 36-50 46 figure 7: bio-oil yield for microwave-assisted hydrothermal in different temperature against time figure 8: bio-oil yield for conventional heating process in different temperature against time corresponding to figure 8, it showing the yield of bio-oil for traditional heating process at different times and temperatures. because conventional heating is an open system, unlike microwave hydrothermal the desired temperature could not be reached in shorter pyrolysis time. it was because the heat loss rate towards the surrounding air is higher than the microwave in an enclosed and regulated device. and so, in conventional heating experiment the pyrolysis time is longer to enable the feedstock to break down into volatile substances. during the pyrolysis time for 400 ° c was risen from 30 minutes to 40 minutes, it could be seen obviously that the bio-oil yield increased from 32.09 wt% to 36.07 wt% but decreased to 31.48 wt% once the time was increased to 50 minutes. the decrease in yield was attributed to occurrence of secondary reaction. non-condensable vapor is generated more than condensable vapour throughout secondary reaction. then it has shown from the figure that the percentage yield for bio char and biogas is steadily increasing when conversion time increases. 3.6 product yield comparison refer to the results obtained in this experiment it can be portrayed that the microwave-assisted hydrothermal offers a benefit over conventional heating. microwave-assisted hydrothermal can generate more efficient bio-oil in a shorter period of time than conventional heating. it was because microwave-assisted hydrothermal provides rapid heating well to feedstock, which are palm kernel shells, and then at the same time increasing the heat distribution in the feedstock sample, thereby creating more bio-oil in a shorter period of time. whereas it is found in conventional heating process that it takes longer pyrolysis time to effectively turn pks into bio-oil. it is not practical to make a direct comparison of the mass percentage yield of each product between the two systems and it is hard to do so because each of these conversion methods has different heating systems. in addition, heat losses to the surrounding environment must also be taken into consideration which can affect the efficiency of the process itself. nonetheless, a consistent pattern of bio-oil yield generated from both microwave-assisted conversion and conventional heating could be described in terms of the conversion temperature and conversion time. for both conversion methods, the bio-oil yield increased as the temperature of pyrolysis and the time of pyrolysis rise before optimum temperature and time were reached. for example, in the microwave-assisted hydrothermal experiment, the lowest yield was 10.70 wt% at 6 minutes, during conversion temperature of 350°c. the yield of bio-oil increased to 25.60 wt% when the temperature rises to 450°c with 9-minute pyrolysis time. since pyrolysis time was beyond 9 minutes, the bio-oil yield declines at both 350°c and 450°c. same pattern in conventional heating indicates that when the temperature rises from 350°c to 450°c, the bio-oil yield also increases from 15.42 wt to 36.07 wt%. microwave-assisted hydrothermal is a favoured method because it gives volumetric heating mechanism modified microwave-assisted rapid hydrothermal liquefaction process for conversion of palm kernel shells to bio-oil 47 for better heating and there is no loss of energy although things were opposed to conventional heating method. the microwave-assisted hydrothermal prevents secondary cracking that could reduce the yield of bio-oil. conventional heating methods also show the inverse temperature profile by transmitting the heat from the surface to the centre of the material. this particular technique often suffers from some drawbacks due to electric heating, such as heat transfer resistance, heat loss to the surrounding area and damage to the reactor can. microwave-assisted hydrothermal is also one of the safe and efficient technologies for biomass, which can be used to efficiently extract bio-oil to produce better results. 3.7 characterization of bio-oil the oil collected from microwave and conventional conversion tested to establish and classify the characteristic inhibits of each of the bio-oil samples. each of the bio oil samples obtained was tested for their calorific value, ph value and functional groups as well. each test was evaluated using different equipment, such as bomb calorimeter to determine the calorific value of the bio oil. whereas, ph paper has been used to classify the ph level of the extracted bio oil of both method, and fourier transform spectroscopy (ft-ir) analysis has been carried out to determine and evaluate the composition of functional groups present in the bio-oil. 3.7.1 ph value bio-oil consists of several organic compounds whose chemical composition had led to some important properties defining the bio-oil itself. since it is a combination of different compounds, the composition of the bio-oil is similar to those of biomass rather than traditional petroleum fuel. it is shown that the ph value of bio-oil is in acidic range 3 and 4 for microwave-assisted and conventional heating respectively. it is reported that the bio-oil from swietenia macrophylla (mahogany) wood possesses the ph value of 5.64 [30]. sutrisno & hidayat, 2016 [31] reported the ph value of pyrolysis raw bio-oil and upgraded bio-oil are in the range of 2.3–4.4. bardalai & mahanta, 2015 [32] found the ph range of 2 to 4 for most bio-oil. and there are few biomasses that give higher ph value to the pyrolysis oil like rice straw, wheat straw etc. furthermore, several other bio-oils seem to be highly acidic, as the ph value of biomass such as eucalyptus wood is located between 1.8-2.9 [33]. bio-oil containing low ph values is due generally to the amounts of organic acid such as acetic acids, carboxylic acid and formic acid. when the ph value of bio-oil drops, the bio-oil becomes more acidic, making it more corrosive to products like aluminum and carbon steel as well. 3.7.2 identification of functional group using ftir the ftir spectrum of the bio-oil obtained from pyrolysis of palm kernel shell for 35g sample at 15 minutes is shown in figure 9. from the ftir result, o-h stretching is observed at range of 3200 3600 cm-1 and contains phenols and alcoholic compound. there are many peaks also at this range which means that bio oil consist of higher oxygen content. the presence of alkanes was found at peak of 2850-3000 cm-1 and 1370-1480 cm-1 when the c-h stretching was occurred. the c=o stretching vibrations between 1628 and 1815 cm-1 represent the presence of ketones, aldehydes, carboxylic acids and their derivatives. the absorbance peaks between 1470 and 1620 cm-1 represent c=c stretching vibrations indicative of alkenes. absorptions possibly due to c-o vibrations from carbonyl components (phenols, esters) occur between 1000 and 1370 cm−1 of the analyzed bio-oil. the absorbance peaks between 669 and 915 cm−1 indicate the possible presence of single, polycyclic and substituted aromatic groups. these results agree with chemical compositions reported in literature consisting of several hundreds of organic compounds, such as acids, alcohols, aldehydes, esters, ketones, phenols and lignin derived oligomers [34]. wavenumbers (cm -1 ) figure 9: functional group of bio-oil for 35g sample at 15 minutes saleh, a. a. et al. (2023): international journal of engineering materials and manufacture, 8(2), 36-50 48 3.7.3 calorific value calorific value is the quantity of heat produced during the entire combustion cycle and then when the product was being cooled toward a room temperature of 25 °c. this is also known as fuel combustion heat and is typically measured by using a calorimeter. bomb calorimeter represents the gross value or high heating value of the oil (hhv) and is expressed in mega-joules per kilogram (mj/kg) whereas the lower heating value (lhv) is the net calorific value and it is obtained from using certain formula and equations. hhv is related to heat that are combusted in a condensed state whereas lhv is the products of combustion that are based on gaseous water and the heat in the vapor is not recovered [28]. the expected calorific values for palm kernel shells (pks) are tabulated in table 3. table 3: expected calorific value result of pyrolysis bio-oil at different conversion temperature pyrolysis temperature (°c) calorific value (mj/kg) microwave-assisted 350 25 450 26 conventional heating 350 23 450 24 based on the table 3, the expected calorific value of the pyrolysis oil based on the microwave and conventional method is in range of 24 – 26 mj/kg which lower than conventional petroleum (40 – 42 mj/kg). abdullah et al. 2011 35] found the calorific value of bio-oil pyrolysis ranging from 20-26 mj kg-1. nanda et al. 2014 [36] indicated that the higher heating value of bio oil is achieved at a higher temperature in the shortest possible time. high calorific value in bio oil was due to a small moisture content of the bio oil sample. composition and ultimate analysis, ash content and calorific value of various biomass feedstock is shown the calorific value for all of the bio-oil from various types of biomass feedstock was in the range of 18.40 mj/kg – 20.07 mj/kg [37]. this range is about half or less to the amount of conventional petroleum calorific value. kawale & kishore 2019 [38] stated that calorific value of biooil produced from a lignocellulosic biomass is evaluated on bomb calorimeter which is 17.093 mj/kg. hence, the expected value of calorific value is made by using the results found from previous research and journal. water content, oxygen content, carbon content, and operating conditions for pyrolysis are among some of the factors that influence the heating efficiency of the bio-oils for pyrolysis. both the content of water and oxygen has had a negative effect on the calorific value. the higher concentrations of oxygen and water in the bio-oil results in a lower calorific value which reduces the heating value than conventional petroleum fuels. using both methods with the same 450°c pyrolysis temperature as an example, the predicted caloric value of microwave pyrolysis is much higher. it is due biooil pyrolysis in microwaves typically produces much lower oxygen content. bardalai & mahanta 2015 [32] stated that oxygen in the bio-oil contributes to increased moisture content, which reduces the amount of hydrocarbon and eventually decreases the heating efficiency. higher water content decreases the bio-oil’s heating value, as it takes evaporation heat during the combustion cycle. additionally, the amount of carbon content in the feedstock often indirectly influences the bio-oil’s calorific value. 4 conclusions bio-oil from palm kernel shells are extracted by using microwave-assisted and conventional heating process. based on results, it is found that there is impact of different parameters on the both conversion methods for bio-oil production. the maximum bio-oil collected in microwave-assisted conversion is 25.60 wt % at 450°c temperature, and 9 minutes time. the maximum biochar obtained in these methods is 350°c and 6 minutes with a yield of 49.35 wt%. the maximum is observed for bio-gas at 350°c during the time of 9 minutes with yield of 54.65 wt%. the highest bio-oil yield produced in conventional heating at 400°c in 40 minutes with a yield of 36.07 wt%. the maximum biochar collected at 350 ° c with a period of 30 minutes with a yield of 63.97 wt% and lastly, the highest yield for bio-gas was at 450°c with a yield of 50.45 wt% in 30 minutes. the ph value for bio-oil obtained from palm kernel shells are 3 and 4 for microwave-assisted and conventional heating pyrolysis process respectively. the calorific value ranges of the bio oil are 25 – 26 mj/kg and 23-24 mj/kg for microwave-assisted and conventional heating process respectively. the ftir results revealed that the bio-oil composition was dominated by oxygen containing compounds and the low ph value indicates the acidic nature of the bio-oil obtained from pks. acknowledgement the author acknowledged the support from yayasan sarawak grant intervention through university of technology sarawak and appreciated the university for providing all the equipment used to conduct this research. references 1. saha, s., ruslan, a. r. m., morshed, a. k. m. m., & hasanuzzaman, m. (2020). global prospects and challenges of latent heat thermal energy storage: a review. clean technologies and environmental policy doi:doi : 10.1007/s10098-020-01997-7 modified microwave-assisted rapid hydrothermal liquefaction process for conversion of palm kernel shells to bio-oil 49 2. malek, a. b. m. a., hasanuzzaman, m., & rahim, n. a. (2020). prospects, progress, challenges and policies for clean power generation from biomass resources. clean technologies and environmental policy, 22(6), 12291253. 3. murray, t., resende, d. f., & luo, g. (2014). fs140e bio-oil: an introductions to fast pyrolysis and its application, 1-8. retrieved from https://research.libraries.wsu.edu:8443/xmlui/handle/2376/5021%5cnhttp://cru.cahe.wsu.edu/cepublications /fs140e/fs140e.pdf. 4. guedes, r. e., luna, a. s., & torres, a. r. (2018). operating parameters for bio-oil production in biomass pyrolysis: a review. journal of analytical and applied pyrolysis, 129, 134-149. 5. czernik, s., & bridgwater, a. v. (2004). overview of applications of biomass fast pyrolysis oil. energy & fuels, 18(2), 590-598. 6. liu, c., wang, h., karim, a. m., sun, j., & wang, y. (2014). catalytic fast pyrolysis of lignocellulosic biomass. chemical society reviews, 43(22), 7594-7623. 7. salema, a. a., & ani, f. n. (2011). microwave induced pyrolysis of oil palm biomass. bioresource technology, 102(3), 3388-3395. 8. nomanbhay, s., salman, b., hussain, r., & ong, m. y. (2017). microwave pyrolysis of lignocellulosic biomass– –a contribution to power africa. energy, sustainability and society, 7(1), 23. 9. gupta, s., mondal, p., borugadda, v. b., & dalai, a. k. (2021). advances in upgradation of pyrolysis bio-oil and biochar towards improvement in bio-refinery economics: a comprehensive review. environmental technology & innovation, 21, 101276. 10. fernandez, y., arenillas, a., & menendez, j. a. (2011). microwave heating applied to pyrolysis. microwave heating applied to pyrolysis, 732-752. 11. zhang, y., chen, p., liu, s., fan, l., zhou, n., min, m., & ruan, r. (2017). microwave-assisted pyrolysis of biomass for bio-oil production. pyrolysis, (july). https://doi.org/10.5772/67442. 12. ingole, p. m., ranveer, a. c., deshmukh, s. m., & deshmukh, s. k. (2016). microwave assisted pyrolysis of biomass: a review. international journal of advanced technology in engineering and science, 4(6), 78-84. 13. lee, x. j., ong, h. c., gan, y. y., chen, w.-h., & mahlia, t. m. i. (2020). state of art review on conventional and advanced pyrolysis of macroalgae and microalgae for biochar, bio-oil and bio-syngas production. energy conversion and management, 210, 112707. 14. lam, s. s., & chase, h. a. (2012). a review on waste to energy processes using microwave pyrolysis. energies 5, 4209-4232. 15. rahman, s. n. f. s. a., rahman, n. a., idris, s. s., bakar, n. f. a., & mokhtar, r. (2015). microwave pyrolysis assisted with carbon based absorbent: an overview. jurnal teknologi (sciences & engineering), 76(10), 17-20. 16. saber, m., nakhshiniev, b., & yoshikawa, k. (2016). a review of production and upgrading of algal bio-oil. renewable and sustainable energy reviews, 58, 918-930. 17. fan, l., chen, p., zhou, n., liu, s., zhang, y., liu, y. ruan, r. (2018). in-situ and ex-situ catalytic upgrading of vapors from microwave-assisted pyrolysis of lignin. bioresource technology, 247, 851-858. 18. huang, f., yu, y., & huang, h. (2018). temperature influence and distribution of bio-oil from pyrolysis of granular sewage sludge. journal of analytical and applied pyrolysis, 130, 36-42. 19. mutsengerere, s., chihobo, c. h., musademba, d., & nhapi, i. (2019). a review of operating parameters affecting bio-oil yield in microwave pyrolysis of lignocellulosic biomass. renewable and sustainable energy reviews, 104, 328-336. doi:https://doi.org/10.1016/j.rser.2019.01.030 20. xie, q., peng, p., liu, s., min, m., cheng, y., wan, y. ruan, r. (2014). fast microwave-assisted catalytic pyrolysis of sewage sludge for bio-oil production. bioresource technology, 172, 162-168. 21. wang, y., dai, l., wang, r., fan, l., liu, y., xie, q., & ruan, r. (2016). hydrocarbon fuel production from soapstone through fast microwave-assisted pyrolysis using microwave absorbent. journal of analytical and applied pyrolysis, 119, 251-258. 22. song, z., yang, y., sun, j., zhao, x., wang, w., mao, y., & ma, c. (2017). effect of power level on the microwave pyrolysis of tire powder. energy, 127, 571-580. 23. wang, n., tahmasebi, a., yu, j., xu, j., huang, f., & mamaeva, a. (2015). a comparative study of microwaveinduced pyrolysis of lignocellulosic and algal biomass. bioresource technology, 190, 89-96. 24. farag, s., fu, d., jessop, p. g., & chaouki, j. (2014). detailed compositional analysis and structural investigation of a bio-oil from microwave pyrolysis of kraft lignin. journal of analytical and applied pyrolysis, 109, 249-257. 25. chen, x., ma, x., zeng, x., zheng, c., & lu, x. (2020). ethanol addition during aqueous phase recirculation for further improving bio-oil yield and quality. applied energy, 262, 114550. 26. fang, j., liu, z., luan, h., liu, f., yuan, x., long, s., xiao, z. (2021). thermochemical liquefaction of cattle manure using ethanol as solvent: effects of temperature on bio-oil yields and chemical compositions. renewable energy, 167, 32-41. 27. zhang, x., wu, k., & yuan, q. (2020). comparative study of microwave and conventional hydrothermal treatment of chicken carcasses: bio-oil yields and properties. energy, 200, 117539. 28. acar, s., & ayanoglu, a. (2012). determination of higher heating values (hhvs) of biomass fuels. energy education science and technology part a: energy science and research 28(2), 749-758. saleh, a. a. et al. (2023): international journal of engineering materials and manufacture, 8(2), 36-50 50 29. rd, m., & md, h. (2017). mass-fraction of oxygen as a predictor of hhv of gaseous, liquid and solid fuels. energy procedia, 142, 4124-4130. 30. chukwuneke, j. l., ewulonu, m. c., chukwujike, i. c., & okolie, p. c. (2019). physico-chemical analysis of pyrolyzed bio-oil from swietenia macrophylla (mahogany) wood. heliyon, 5(6), e01790. 31. sutrisno, b., & hidayat, a. (2016). upgrading of bio-oil from the pyrolysis of biomass over the rice husk ash catalysts. iop conference series: materials science and engineering, 162(1), 012014. 32. bardalai, m., & mahanta, d. k. (2015). a review of physical properties of biomass pyrolysis oil. international journal of renewable energy research, 5(1), 277-286. 33. mohanty, p., pant, k. k., naik, s. n., das, l. m., & vasudevan, p. (2011). fuel production from biomass: indian perspective for pyrolysis oil. journal of scientific & industrial research, 70, 668-674. 34. xiu s, shahbazi a (2012). bio-oil production and upgrading research: a review. renew sustain energy rev 16: 4406–4414. 35. abdullah, n., sulaiman, f., & gerhauser, h. (2011). characterisation of oil palm empty fruit bunches for fuel application. journal of physical science, 22(1), 1-24. 36. nanda, s., mohanty, p., kozinski, j. a., & dalai, a. k. (2014). physico-chemical properties of bio-oils from pyrolysis of lignocellulosic biomass with high and slow heating rate. energy and environment research 4(3), 21-32. 37. rezaei, h., yazdanpanah, f., lim, j. c., lau, a., & sokhansanj, s. (2018). woody feedstock pretreatments to enhance pyrolysis bio-oil quality and produce transportation fuel, biomass for bioenergy recent trends and future challenges, abd el-fatah abomohra, intechopen, doi: 10.5772/intechopen.81818. 38. kawale, h. d., & kishore, n. (2019). bio-oil production from a lignocellulosic biomass and its fuel characteristics. journal of physics: conference series, 1276, 012073. international journal of engineering materials and manufacture (2017) 2(1) 11-15 https://doi.org/10.26776/ijemm.02.01.2017.02 a. h. taha, m. h. f. al-hazza and e. y. t. adesta department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: muataz@iium.edu.my reference: taha, a. h.., al-hazza, m. h. f. and adesta, e. y. t. (2017). modelling and analysing deadlock in flexible manufacturing system using timed petri net. international journal of engineering materials and manufacture, 1(2), 11-6. modelling and analysing deadlock in flexible manufacturing system using timed petri net assem hatem taha, muataz hazza faizi al hazza, erry y. t. adesta received: 21 february 2017 accepted: 15 march 2017 published: 31 march 2017 publisher: deer hill publications © 2017 the author(s) creative commons: cc by 4.0 abstract flexible manufacturing system (fms) has several advantages compared to conventional systems such as higher machine utilization, higher efficiency, less inventory, and less production time. on the other hand, fms is expensive and complicated. one of the main problems that may happen is the deadlock. deadlock is a case that happens when one operation or more are unable to complete their tasks because of waiting of resources that are used by other processes. this may occur due to inappropriate sharing of the resources or improper resource allocation logic which may lead to deadlock occurrence due to the complexity of assigning shared resources to different tasks in an efficient way. one of the most effective tools to model and detect the deadlocks is the petri net. in this research the matlab software was used to detect the deadlock in two parallel lines with one shared machines. the analysis showed that the highest utilization is in transition t4 with 71% and the longest waiting time is in place p4 at 72 seconds. hence, deadlock was located there as parts wait to be processed by machine 1 which is busy to perform processes on parts in both lines. keywords: fms, deadlock, shared resources, petri net 1 introduction the competition of companies in marketplace requires high degree of efficiency and low production time. these companies try to have suitable manufacturing systems that can be flexible to any circumstance as product life cycles are reduced in the continuously changing market. to respond to these demands, the use of a flexible manufacturing system (fms) has been widely applied to attain high productivity and production flexibility [1]. manufacturing process has been improved recently to meet the increasing requirements of the market. one of the very demanding requirements that impacts the development of the manufacturing process is the variability aspect in the market. market needs are changing rapidly, which require more flexibility in the manufacturing process to respond to such changes quickly. one of the main criteria that indicate to the flexibility in the manufacturing process is the degree of resources sharing. fms is a system that has capability to react to any changed condition happen in process. it includes numerically controlled machines with the aid of value-added, automatic and material handling facilities. industrial companies use fms to fulfil the demands for making different kinds of products from small to medium quantity in production [2]. fms includes both material handling devices and machines which are controlled by computer programs to make the processes flow flexibly. it gives operators the chance to load new programs simply when it is necessary to manufacture different kinds of products. fms helps managers to provide customized products, improve equipment utilization to reduce costs and process time [3]. in fms, shared resources with many parts being used in the system may cause a major issue that industries face which is deadlock. deadlock is a common phenomenon in computer integrated systems (cim) such as automated production system. it is an event where the manufacturing system wholly or partially stop and unable to finish a specific task. it occurs when some parts in waiting status as the machines needed to complete their operation are held by other parts in the production line [4]. deadlock issue was ignored in the past by eliminating all parts or some of them that have a role for the deadlock to happen and using their resource with other parts in the operation. yet, flexible manufacturing system forced modelling and analysing deadlock in flexible manufacturing system using timed petri net 12 manufacturers to look for ways to allocate resources without deadlock exist to run the operations efficiently, flexibly and at low cost [5]. consequently, there is a need to study deadlock and find a method to avoid it and prevent it if it’s possible. high degree of resources sharing leads to more flexibility in the production. however, higher degree of resources sharing is also a source of conflicts in accessing the resources by many production processes. one of the main problems of synchronization between multi-processes in accessing shared resources is deadlock. the problem of deadlock causes halt or failure in part or evens the whole manufacturing system unless a human being intervention is performed in order to break the deadlock. the general taxonomy of the approaches of modelling fms consists of three classes of approaches. petri nets have been used widely besides directed graph [6], and finite state automata [7]. petri net modelling techniques is a mathematical tool for modelling different aspects of fms, and for handling all its attributes such as concurrency, causal dependency, and dynamics. 2 types of fms fms has five types and they are sequential, random, dedicated, engineered and modular fmss [8]. in sequential fms, one piece part is manufactured in batch line followed by another product prepared to be processed after the first one and so on for other parts. random fms can make any mix of product types without sequence. dedicated fms can produce regular limited mix of product types. for engineered fms, same mix of part types can be manufactured in the system. modular fms is an advanced system which allows the operator to use any of the four kinds previously mentioned. fms can be classified based on level of flexibility [9]. there are three levels of flexibility: basic flexibility, system flexibility and aggregate flexibility. basic flexibility contains three kinds which are machine flexibility, material handling flexibility and operation flexibility. machine flexibility is the level of easiness that a machine can do several tasks. material handling flexibility is a measure of ability to transfer different part kinds and place them at several machine tools in the manufacturing system. operation flexibility is the ease to make a part type using different process sequences. system flexibility includes volume, expansion, routing, process and product flexibility. volume flexibility is the ability to manufacture efficiently a part type with different volumes. expansion flexibility is to establish a system and do changes for the aim of expanding it. routing flexibility is a measure of available routes that a part can be processed through them in the system. process flexibility is the ability to make amount of parts without need to conduct big changes in setup. product flexibility is the number of parts that system can produce without doing a small change in setup. aggregate flexibility has three types which are program, production and market flexibility. program flexibility is the system capability to perform operations for long duration without any interruption. production flexibility is to make little investment to manufacture specific number of parts and market flexibility is the capacity of system to adjust its process and plan in accordance of market requirements. fms has several advantages such as higher machine utilization than conventional manufacturing system, fewer machines to be used in the process, less space used in the factor, less used inventory, less lead time and higher response to part, tool and production schedule changes. on the other hand, fms is expensive, complicated when compared to transfer lines and requires skilled worker to control the system and fix any problem [10]. 3 deadlock deadlock is a case that happens when processes in the system can’t do their tasks because of waiting of resources held by other processes. it occurs in flexible manufacturing system due to resource sharing, buffer capacity and availability in material handling system. it leads to affect on manufacturing system performance by reducing machine utilization, efficiency in production process, and delay in finishing the operation [11]. there are four cases where deadlock can occur. these conditions are mutual exclusion, hold and wait, no preemption and circular wait [12]. mutual condition means resource can be utilized by one process and no other process can use at a time. hold and wait condition occurs when one is held by a process which at the same time use another resource. this causes a problem in resource utilization as a process might request a resource but use it at end of its task only. this condition also leads to starvation for some processes that wait for resources with no specific time. no pre-emption condition is when it is not possible to interrupt process while it is functioning to give the access of the resources to another process and to resume its work again in later time. circular wait condition exists when a there is a resource requested by a process and this resource is held by the next process in the chain. the deadlock and blocking phenomena may lead to tragic results and intervention from human beings. detecting deadlocks in the manufacturing systems through developing simulating model will help to improve and increase the efficiency of the flexible manufacturing systems. in this paper, timed petri net was used to simulate the manufacturing system and analyse it to determine the deadlocks. 4 petri net petri net (pn) is a tool for modelling and studying systems with parallel, synchronized processes and shared resources. a pn consists of places (p) which denote to conditions, transitions (t) that indicate events and arcs (f) that link places to transitions. this can be represented by n = (p, t, f), where p and t are limited but not equal zero and f ⊆ (p × taha et al., (2017): international journal of engineering materials and manufacture, 1(1), 1-15 13 t) ∪ (t × p) which means that firing tokens (k) can be from place to transition or vice versa. token in a place carries the condition that tells that the resource or item is available in this place. p is circle shape in petri net and t can be bar or box shape. given a node x ∈ p ∪ t, an event has input place (pre-condition x) which is defined as •x = {y ∈ p ∪ t|(y, x) ∈ f}, and output place (post-condition x) that is defined as x• = {y ∈ p ∪ t|(x, y) ∈ f}. a marking is the state of system that is m: p → z+, where z+ = {0, 1, 2,….., n} which is number of integers. given a place p ∈ p and a marking m, m (p) denotes the number of tokens in p at m. let s ⊆ p be a set of places; the sum of tokens in all places of s at m is denoted by m (s), i.e., m(s) = σ p ∈ s p∈ s m (p). a marked pn is the one with an initial marking (m0) is, denoted as (n, m0). a transition t ∈ t is enabled at a marking m, denoted by m [t >, if ∀p ∈ •t, m (p) > 0. an enabled transition t at m can be fired, resulting in a new reachable marking m‵, denoted by m (t > m‵), where m‵ (p) = m (p) − 1, ∀p ∈ •t \ t•, m‵ (p) = m (p) + 1, ∀p ∈ t• \ •t, and, otherwise, m‵ (p) = m (p) [13,14]. 5 scenario a manufacturing system consists of two parallel jobs to make final product from parts a and b. machine 1 is shared between the two lines for parts coming from buffer 1 and 2. this leads to deadlock as the machine will be busy with doing process on one part while the other part waits for its turn. machine 2 and 3 perform a process for part a and b respectively, after being done from machine 1. the last machine assembles part a and part b to make the final product. the process was designed using timed petri net. matlab software has been used to simulate the system as shown in the figures 2 and 3. it was assumed that 15 available parts (represented by tokens) are in each source (represented by part a and part b places). the following elements in the net are: t1, t2: immediate transitions to show movement of parts a & b to buffers 1 and 2. p3, p4: buffers 1 and 2. p5, t3, t4: shared machine 1 with a 10 seconds process. p6, t5: machine 2 performing a process within 12 seconds. p7, t6: machine 3 accomplishing a process at 14 seconds. p8, p9, t7: assembly process for part a and b performed at duration of 6 seconds using machine 4. there is one token in place 5 as a signal for machine 1 to perform process once one token comes from place 3 or place 4. then, it will be available again once token that represents part goes to the next machine in line to be processed. figure 1: scenario of manufacturing system modelling and analysing deadlock in flexible manufacturing system using timed petri net 14 analysis of places was obtained and collected in tables 1. arrival sum is the number of parts that arrives to places or leave them to another one. arrival distance is the mean time between parts to reach to a place or to depart from it. waiting time is the average time that part stays in a place and queue length is average number of parts in a place. place p4 has the longest waiting time at 72 seconds and a queue length of 1.3 part as shared machine (p6) is busy in processing other parts from both lines which leads to delay and more wait for parts in this place. table 2 illustrates the analysis of transitions in the petri net. service sum is the number of executed part in each transition. service distance is the mean time between firing one token and another. utilization is the probability of transition to be busy. transition t4 has the highest utilization at 71% while the lowest utilization is in t7 at 32.3%. deadlock exists where there is a high utilization and a long waiting time. so, it exists in p4 and t4. figure 2: petri net design of the system figure 3: simulation of the system table 1: places analysis place name arrival sum (part) arrival distance (seconds) waiting time (seconds) queue length (part) p3 5 24.8 41 1.2 p4 3 41.3333 72 1.3 p5 5 24.8 10 0.5 p6 4 31 12 0.3 p7 2 62 14 0.2 p8 3 41.3333 23 0.4 p9 2 62 17 0.3 product 2 62 taha et al., (2017): international journal of engineering materials and manufacture, 1(1), 1-15 15 table 2: transitions analysis transition name service sum (part) service distance (seconds) utilization (%) t3 4 31 32.3 t4 2 62 71 t5 3 41.3 37.1 t6 2 62 66.1 t7 2 62 30.6 6 conclusions based on the results, it can be concluded that use of petri net method was an effective tool in detecting the deadlock for parallel machines with shared resources. timed petri net was used to simulate and analyse the manufacturing system. the simulation analysis denoted that the deadlock is in p4 and t4 that have the highest value of utilization and waiting time respectively. a proper planning for the production system is needed to eliminate the deadlock and ensure the flexible flow of the parts in the system. references 1. kaschel c., h., & bernal, l. m. (2006). importance of flexibility in manufacturing systems. international journal of computers, communications & control, vol. i, no. 2, 53-60. 2. qiao, g., lu, r. f., & mclean, c. (2006). flexible manufacturing systems for mass customisation manufacturing. international journal of mass customisation, vol.1, no. 2/3, 374 – 393. 3. heizer, j., & render, b. (2005). operations management, 8th edition. new jersey: pearson prentice hall. 4. xing, k., lin, f., & hu, b. (2001). an optimal deadlock avoidance policy for manufacturing systems with flexible operation sequence and flexible routing. proceedings of the ieee international conference on robotics 8 automation, vol. 4, 3565 – 3570. 5. fanti, m. p., & zhou, m. (2004). deadlock control methods in automated manufacturing systems. ieee transactions on systems, man, and cybernetics, part a: systems and humans, vol. 34, no. 1, 5-22. 6. leibfried, t. f. (1989). a deadlock detection and recovery algorithm using the formalism of a directed graph matrix. sigops operating systems review, vol. 23, issue 2, 45 – 55. 7. yalcin, a., & boucher, t. o. (2000). deadlock avoidance in flexible manufacturing systems using finite automata. ieee transactions on robotics and automation, vol. 16, no. 4, 424 – 429. 8. shivanand, h., benal, m., & koti, v. (2006). flexible manufacturing system. new age international pvt ltd publishers. 9. basak, ö., & albayrak, y. e. (2014). petri net based decision system modeling in real-time scheduling and control of flexible automotive manufacturing systems. computers & industrial engineering, 2-11. 10. chahal, v. (2012). an efficient approach of good manufacturing flexibility by fms and rms with minimizing the overall wastage by jit. proceedings of the national conference on trends and advances in mechanical engineering, faridabad, haryana, 833-838. 11. baruwa, o. t., piera, m. a., & guasch, a. (2014). deadlock-free scheduling method for flexible manufacturing systems based on timed colored petri nets and anytime heuristic search. ieee transactions on systems, man, and cybernetics: systems, issue 99, 1-16. 12. li, z., wu, n., & zhou, m. (2012). deadlock control of automated manufacturing systems based on petri nets— a literature review. ieee transactions on systems, man, and cybernetics—part c: applications and reviews, vol. 42, no. 4, 437-462. 13. david, r., & alla, h. (2010). discrete, continuous, and hybrid petri nets, 2nd edition. berlin: springer. 14. xing, k., han, l., zhou, m., & wang, f. (2012). deadlock-free genetic scheduling algorithm for automated manufacturing systems based on deadlock control policy. transactions on systems, man, and cybernetics—part b: cybernetics, vol. 42, no. 3, 603-615. mathematical modeling of feature conversion international journal of engineering materials and manufacture (2017) 2(1) 1-10 https://doi.org/10.26776/ijemm.02.01.2017.01 h. ullah and a. asiyah mechanical engineering programme faculty of engineering, universiti teknologi brunei jalan tungku link, brunei darussalam e-mail: hamid.ullah@utb.edu.bn reference: ullah, h. and asiyah, a. (2017). design and development of mobile phone using quality function deployment. international journal of engineering materials and manufacture, 2(1), 1-10. design and development of mobile phone using quality function deployment hamid ullah and asiyah ali received: 22 november 2016 accepted: 17 february 2017 published: 31 march 2017 publisher: deer hill publications © 2017 the author(s) creative commons: cc by 4.0 abstract this paper presents design and development of mobile phone where quality function deployment approach is used to convert customer needs into design specifications. customer needs and their relative importance are identified through the analysis of customer survey. technical requirements that could fulfill the customer needs are established and a relationship matrix is developed between the customer needs and the technical requirements. the relationship matrix is then converted into the house of quality matrix. using output from the house of quality, concepts of a mobile phone are generated. concept generation is followed by concept selection where finally an improved model of a new mobile phone is presented. keywords: customer needs, technical requirements, house of quality (hoq), quality function deployment (qfd), concept generation, concept selection. 1. introduction yoji akao is considered as the father of qfd who introduced the concept of qfd in japan in 1966. the japanese phrase “hinshitsu kino tenkai” matches to “quality function deployment”, where “function” corresponds to the analysis of the business process to enhance the quality of products in the development process (akao and mazur, 2003). the first use of qfd was made in 1972 by professor mizuno to mitsubishi’s kobe shipyard site in the design of super tankers (martins and aspinwall 2001). company’s success lies in knowing the customer needs and foreseeing the modifications required in the already available products (soota et al. 2008). innovation-based companies may push a technology into the market by those who design the product to those who produce it and to those who distribute it in the market (d.r. kiran, 2017). therefore, it is very essential for any firm to develop the quality of its product (or service) by bridging the gap between product quality and customer satisfaction (lin 2007). qfd is the best tool to convert the customer preferences into quality attributes. it is a powerful development tool for achieving product development, improving product quality, reducing time to market, and decreasing the cost of production. it is a famous design tool that considers systematically the customer needs and preferences in product planning and therefore has good applications in manufacturing and service organizations (dijkstra and bij, 2002). qfd is a method for developing a quality design by incorporating the consumer demands into design specifications (akao 1990). basically, it is aimed to fulfill customer preferences of the product (kasim et al., 2009). it is a customer driven technique (guinta and praizler, 1993). it is broadly spreading in business organizations because of its wonderful usefulness. qfd is a planning tool that guides the design, manufacturing, and marketing of products (chan and wu, 2003). it uses planning matrices that connect customer requirements, design and target specifications, and competitive performance into one graph. it is a helpful tool that facilitates planning, decision-making, and communication in the product development phase. at its heart is the ‘voice of customer’, which gives it the unified stage throughout the product planning and development process. it takes the ‘voice of customer’ throughout the product development process out into the market place. the resulting new product will delight the customers and outshine the competition provided the qfd is done thoroughly (pun et al., 2000). mailto:hamid.ullah@utb.edu.bn design and development of mobile phone using quality function deployment 2 qfd reduces the gap between organization and its customers. to achieve the objective, it is necessary to know the customer needs so that, these could be considered from the early stages of the planning process. it involves implementing technological solutions, by experts, to determine the customer requirements. qfd provides significant advantages, for example: to reduce design and development time, to spotlight the satisfaction of customers, and to increase communication at all levels of an organization (kasim et al., 2009). it speeds up changes during the various phases of product development. it can assist product designers to identify important design attributes and also provide suggestions for possible improvements in these attributes (liu, h-t and cheng, h-s., 2016). because of these advantages, it has become an accepted support to the product planning and development process (akao and mazur, 2003; chan and wu, 2002; chan and wu, 2003; day, 1993). it is a historically proven means of guiding process development by using technical performance measures for a systematic organization of all independent variables and their interrelationships. it is cited as a key facilitating method in simultaneous engineering (menon et al., 1994), and is the most extensive implementation of total quality management (sage, 1992). the crucial step in qfd is to derive the prioritization of design specifications from customer needs for a product (yan and ma 2015). the successful implementation of qfd lies in the accurate capturing and prioritization of the customer requirements (kamvysi et al. 2014). while the new customer needs have a major effect on the product successfully, the traditional requirements may not be forgotten by the product’s designers (ashtiany, m.s, and alipour, a., 2016). the identification and prioritization of customer needs could also be achieved through integration of kano's model, analytical hierarchy process (ahp) technique and qfd matrix (hosna pakizehkar et al., 2016). qfd therefore has been broadly spreading in the industrial and business organizations because of its wide and diverse usefulness. the key planning part of qfd is the house of quality (hoq). the customer needs are called ‘whats’ while the technical specifications are called ‘hows’ in the hoq matrix. the paper is organized as follows: section 2 describes methodology. section 3 mentions mission statement of the product. it is followed by identifying customer needs and establishing their relative importance in section 4. defining technical requirements is presented in section 5. building house of quality for mobile phone is discussed in section 6. section 7 describes ranking of technical requirements which is followed by concept generation and concept selection presented in sections 8 and 9 respectively. at the end, discussion and conclusion are presented. 2. methodology survey questionnaire is designed to get feedback from the end users’ of mobile phone in brunei darussalam with respect to their preferences from a new mobile phone. the survey questionnaire consists of twenty (20) questions: eleven (11) multiple choice questions, one (1) ranking question and 8 open ended questions. the questionnaire is distributed online to the customers. the web link of the questionnaire is shared through email, social media such as facebook and whatsapp messages. out of 100 mobile phone end users, response is received from 85 respondents. data collected is interpreted in terms of customer needs. relative importance is assigned to the customer needs on a scale of 1 to 5 (where 1 indicates the least important need and 5 indicates the most important need). the customer needs, their relative importance, and technical requirements are used in building hoq for the mobile phone. the input from the hoq is used in concept generation phase of mobile phone. concept generation is followed by concept selection of mobile phone. cad model of the improved mobile phone is presented. 3. mission statement a mission statement provides a basic functional description of the product, identifies its target market, and also specifies its business goals. the mission statement for the mobile phone is provided in table 1. 4. identifying customer needs and establishing their relative importance aim of this phase is to identify the customer needs and requirements and to effectively communicate to the product design and development team. the idea behind the technique is to create high-quality information guide that runs directly between the developers of the product and the customers in the target market. this idea is made on the principle that those responsible for the direct control of the details of the product must interact with customers and also experience the use environment of the product. from the survey questionnaire distributed among the end users, the data collected is compiled into the voice of customer (voc). the voc is converted into customer needs. there are different terminologies used for customer needs. these include customer wants, customer preferences, customer choices, customer wishes, customer expectations, and customer requirements. the customer needs are called ‘whats’ in the hoq matrix and acts as a first building block in building the hoq and is the most important phase of qfd. once the customer needs have been identified, their relative importance is determined. the value of relative importance of the customer need is necessary to obtain the value of the weighted average for the relationship matrix in the hoq. the customer needs and their relative importance are shown in table 2. the average value of relative importance shown in table 2 is assigned on the basis of customer feedback. the features are rated on a scale of 1 to 5. http://www.sciencedirect.com/science/article/pii/s0377221714001775 ullah and asiyah (2016): international journal of engineering materials and manufacture, 2(1), 1-10 3 table 1: mission statement for the mobile phone. product description mobile phone with basic and advanced features key main objectives  product introduced in 1th q of 2017  50% gross margin  10% share of mobile phone market by 2020 primary market  executives  youngsters  students secondary market  middle class  casual users assumptions  water proof  solar chargeable  touch screen  dual sim  light weight stakeholders  users  design department  manufacturing / production department  sale force and service center  legal department 5. defining technical requirements the next step in the qfd technique is to identify a list of suitable technical requirements that could meet the customer needs. these requirements translate the customer needs into quantifiable terms. these requirements define how to respond to the customer needs. the technical requirements need to be measureable so that it could be determined that the customer needs are satisfied. at least one technical requirement is identified for each customer need. other terminologies used for technical requirements are: engineering characteristics, quality attributes, design requirements, and voice of company. the technical requirements are called ‘hows’ in the hoq matrix. technical requirements that could meet the customer needs are provided in table 2. table 2: customer needs (their relative importance) and technical requirements. no. customer needs relative importance of customer needs technical requirements 1 high camera resolution 4.88  high mp camera resolution  led flash  autofocus 2 external memory card slot 4.77  micro sd (secure digital) card slot  pin ejection button 3 high internal memory 5.12  built in storage  high ram 4 battery is removable 4.5  non built in battery  high battery capacity  fast charging battery 5 wireless charger 4.38  fast wireless charging pad  travel adapter  micro usb adapter 6 long lasting battery life 5.31  non built in battery  high battery capacity  fast charging battery 7 fast operating system 5.23  latest os  high ram 8 durable screen 4.36  corning gorilla glass 4  ip 68 material (dust and water resistant)  tempered glass screen protector  design and development of mobile phone using quality function deployment 4 9 large screen 4.12  screen to body ratio 10 waterproof 4.96  ip 68 material  plastic coated speaker  rubber protection usb port 11 dual sim card slot 3.48  single nano sim card slot  dual sim card ( mmc slot)  pin ejection button 12 speaker on the front 4.04  plastic coated speaker  equalizer software 13 stylus pen 3.9  stylus pen 14 fingerprint lock 3.72  fingerprint sensor  home button 15 stand at the back of phone 3.94  ring holder/stand on back cover 16 holder on the phone 2.7  ring holder/stand on back cover 17 radio 3.04  frequency network software  plastic coated speaker 18 different colors of back cover 3.11  ip68 material 19 projector 3.06  built-in digital light processing (dlp) projector 6. building house of quality for mobile phone using the above data (customer needs, their relative importance and technical requirements) a hoq is built. hoq is an important element of qfd. it gives a central part to how well the technical requirements address the customer needs. the hoq is shown in figure 1. the customer needs (whats) are shown in the 2 nd leftmost column of the hoq matrix while the technical requirements (hows) are shown in the topmost row in hoq. the customer needs are followed by their relative importance presented in the 3 rd leftmost column of the matrix. the cells after the column for the relative importance show the interrelationship between the customer needs and the technical requirements. there may be ‘no relationship’, ‘weak relationship’, ‘medium relationship’, or ‘strong relationship’ between the customer needs and the technical requirements. the weights assigned to these relationships are 0, 1, 5, and 10 respectively. the values of 1, 5 and 10 are shown in the hoq matrix by the symbols shown in table 3. a blank cell in the matrix shows ‘no relationship’ between the customer needs and the technical requirements. purpose of the interrelationship is to translate the customer needs into the technical requirements. this interrelationship matrix is a two-dimensional matrix containing cells that relate to the combinations of individual customer need and technical requirement. after all calculations have been made, the top five rankings appears to be ip68 casing, micro sd card slot, nonbuilt-in battery, high battery capacity, and plastic coated speaker respectively. the roof of the hoq shows the correlation among the technical requirements. the plus (+) sign in a cell of the roof shows that improving a particular technical requirement causes improvement in the technical requirements of the corresponding cells. a minus (-) sign could be used in a cell if improving a technical requirement causes deterioration in the technical requirements of the corresponding cells. the symbols used for the interrelationship between the customer needs and the technical requirements are shown in table 3. the correlation among the technical requirements obtained from the roof of hoq is shown in table 4. 7. ranking of technical requirements it is the final element of the hoq. it is achieved from the weighted average of the technical requirements in the interrelationship matrix of the hoq. it provides a summary of the conclusions drawn from the information contained in the entire matrix of the hoq. it presents a priority score and ranks all the technical requirements in the hoq matrix. the ranking of the technical requirements is shown in the hoq matrix. table 3: legend of symbols for house of quality. strong relationship 10 ⃝ medium relationship 5 δ weak relationship 1 ullah and asiyah (2016): international journal of engineering materials and manufacture, 2(1), 1-10 5 figure 1: house of quality design and development of mobile phone using quality function deployment 6 table 4: correlation among technical requirements. high camera resolution  built in storage  high ram  high battery capacity led flash  built in storage micro sd external slot  pin ejection high ram  frequency network  built in projector high battery capacity  fast charging battery  fast wireless charging pad travel adaptor  micro usb adapter corning gorilla glass 4  ip 68  screen ratio ip 68  tempered glass screen protector  plastic coated speaker  rubber protection usb port plastic coated speaker  equalizer software fingerprint lock  home button 8. concept generation mobile phone concepts are generated using the input from the hoq. three concepts of the improved mobile phone are generated. all the three concepts are designed in rectangular shape. based on the input from end users of mobile phone, features such as front and back camera, speaker, switch button, ring holder are included in the concepts. concept 1 shown in figure 2 has the features of home button, screen and front camera. on the right side, there are volume and switch button. on the back side of the mobile phone, the back camera is circular in shape and there is a dual flash and ring holder attached to the back cover. the battery is removable and there is external memory card and sim card slots covered by the back cover of mobile phone. the speaker is designed on the bottom side of the mobile phone together with the usb charging port. on the top side of the mobile phone, there is a hole for earphone plug. in concept 2, shown in figure 3, the back side of the mobile phone is almost the same as that of concept 1. the camera shape is rectangular. the switch button is on the right of the top side. the speaker is at the front of the mobile phone. there are dual flash for both front and back cameras. the home button is rectangular in shape while, it is circular in case of concept 1. the external memory card and sim card slots are at the left side of the mobile phone. concept 3 is shown in figure 4. there are few similarities between concept 2 and concept 3. the difference between concept 3 and concept 2 is that the front camera is larger in size and the ring holder is circular in shape. 9. concept selection final concept is selected based on the criteria shown in table 5. the evaluation matrix provides concept 2 to be the final best concept. the selected concept is modeled using autodesk inventor professional 2015. the design specifications of the final concept are presented in table 6. the final concept could be considered for subsequent development activities. ullah and asiyah (2016): international journal of engineering materials and manufacture, 2(1), 1-10 7 figure 2: concept 1 figure 3: concept 2 design and development of mobile phone using quality function deployment 8 figure 4: concept 3 table 5: evaluation matrix for concept selection. criteria concepts 1 (datum) 2 3 aesthetic + 0 cost weight + user friendliness + 0 durability + 0 easy to manufacture safety 0 0 sum "+" 3 1 sum "-" 3 2 sum "0" 1 4 net score 0 -1 ranking 1 2 ullah and asiyah (2016): international journal of engineering materials and manufacture, 2(1), 1-10 9 table 6: design specifications of the concept selected. dimensions 142 mm x 70 mm x 08 mm body build corning gorilla glass 4: the toughest glass material for mobile phone, ip 68 material screen size 58 mm x 115 mm operating system android os, marshmallow: latest updated operating system cpu quad-core 2.3 ghz memory card slot micro sd up to 200 gb internal storage 128 gb with 4 gb ram camera front camera: 08 mp with dual led flash back camera: 13 mp with autofocus and dual led flash battery removable battery with a capacity of 3000 mah 10. discussion and conclusions mobile phone is designed and developed using qfd technique. customer requirements (voice of customer) of a new mobile phone are identified by conducting a market survey. voc is converted into customer needs. customer needs and their relative importance are identified. hoq for the mobile phone is built. final specifications of the mobile phone are established. in the design specifications, the dimensions of the mobile phone are 142 mm x 70 mm x 08 mm. the screen size is 115 mm x 58 mm which is about 70% of the front side of the mobile phone. the mobile phone is operated with the latest operating system which in android marshmallow version 6.0. quad core 2.3 ghz is chosen for the fastest processor of the mobile phone. to be long lasting or durable, corning gorilla glass 4 is specified for body of the mobile phone. ip 68 material is specified for the mobile phone to make it waterproof. external memory card slot is provided for more efficient storage. micro secure digital (msd) card is specified to fit up to 200 gb, the maximum capacity for external storage. the slot is incorporated with sim card slot. the mobile phone can hold two sim cards at the same time where the memory card slot is used for second sim card. high camera resolution is included. in order to get good resolution, both front and back cameras have their own dual led flash. they have high mega pixel for better resolution. a removable battery in the mobile phone is located at its back covered by the back cover. it has high capacity of 3000 mah so that the mobile phone can function longer. there is a ring holder attached to the back cover of the mobile phone. it acts as a convenient and safe grip to prevent falling of the mobile phone while in use. it can also be used as a stand while watching videos by the mobile phone. in conclusion, qfd is very important method for development of new products according to customer needs. it helps to improve the existing product by taking into account customer requirements and is therefore a very good planning tool. it is worth to mention that the survey questionnaire is distributed within various universities in brunei darussalam. majority of the respondents are students. in future research, diverse users of mobile phone could be considered for taking their input to develop mobile phone. also, instead of relying only on survey questionnaire, other modes of data collection, for example, one-on-one interview, focus groups, and observing the product in use could be considered. references 1. akao, y. (1990). quality function deployment: integrating customer requirements into product design. productivity press, cambridge. 2. akao, y., mazur, g. h. (2003). the leading edge in qfd: past, present and future. international journal of quality &reliability management, 20(1), 20-35. 3. ashtiany, m. s, and alipour, a. (2016). integration axiomatic design with quality function deployment and sustainable design for the satisfaction of an airplane tail stakeholders. procedia cirp 53 (2016), the 10th international conference on axiomatic design, icad 2016, 142 – 150. 4. chan, l., wu, m. (2002). quality function deployment: a literature review. european journal of operational research, 143(3), 463-497. 5. chan, l. k. and wu, m. l. (2003). quality function deployment: a comprehensive review of its concepts and methods. quality engineering, 15(1), 23–35. 6. day, r. g. (1993). quality function deployment: linking a company with its customers. asqc quality press, milwaukee. design and development of mobile phone using quality function deployment 10 7. dijkstra, l. and bij, h. (2002). quality function deployment in healthcare: methods for meeting customer requirements in redesign and renewal. international journal of quality & reliability management, 19(1), 6789. 8. guinta, l. r. and praizler, n. c. (1993). the qfd book: the team approach to solving problems and satisfying customers through quality function deployment. amacom, new york. 9. hosna, p., sadrabadi, m. m., rasool, z. m. & amir, e. e. (2016). the application of integration of kano's model, ahp technique and qfd matrix in prioritizing the bank's substructions, 3rd international conference on new challenges in management and organization: organization and leadership, 2 may 2016, dubai, uae, procedia social and behavioral sciences 230, pp. 159 – 166, doi: 10.1016/j.sbspro.2016.09.020. 10. kamvysi, k., gotzamani, k., andronikidis, a. & georgiouc, a.c. (2014). capturing and prioritizing students’ requirements for course design by embedding fuzzy-ahp and linear programming in qfd. european journal of operational research, 237(3), 1083–1094. 11. kasim, m. daws, zuhair, a. a, amer a. m. (2009). an intelligent quality function deployment (iqfd) for manufacturing process environment. jordan journal of mechanical and industrial engineering, 3(1), 2330. 12. kiran, d.r. (2017). quality function deployment, total quality management: key concepts and case studies, chapter 30, elsevier b.v., 425-437. 13. lin, w.b. (2007). an empirical of service quality model from the viewpoint of management. expert systems with applications, 32, 364-75. 14. liu, h-t and cheng, h-s. (2016). an improved grey quality function deployment approach using the grey triz technique. computers & industrial engineering, 92, 57-71. 15. martins, a. and aspinwall, e.m. (2001). quality function deployment: an empirical study in the uk. total quality management, 12(5), 575-588. 16. menon, u. et al. (1994). quality function deployment: an overview. in c. syan and u. menon (eds.), concurrent engineering—concepts, implementation and practice, london: chapman and hall, 90–99. 17. pun, k.f., chin, k.s., and lau, h. (2000). a qfd/hoshin approach for service quality deployment: a case study. managing service quality, 10(3), 156-169. 18. sage, a. (1992). systems engineering. fairfax, va: george mason university, school of information technology and engineering, 278–284. 19. soota, t., singh, h., and mishra, r. (2000). defining characteristics for product development using quality function deployment: a case study on indian bikes. quality engineering, 20(2), 195 – 208. 20. yan, h-b and ma, t. (2015). a group decision-making approach to uncertain quality function deployment based on fuzzy preference relation and fuzzy majority. european journal of operational research, 241(3), 815829. http://www.emeraldinsight.com/0265-671x.htm http://www.sciencedirect.com/science/article/pii/s0377221714001775 http://www.sciencedirect.com/science/article/pii/s0377221714001775 http://www.sciencedirect.com/science/article/pii/s0377221714001775 http://www.sciencedirect.com/science/article/pii/s0377221714001775 http://www.sciencedirect.com/science/article/pii/s0377221714001775 http://www.sciencedirect.com/science/journal/03772217 http://www.sciencedirect.com/science/journal/03772217 http://www.sciencedirect.com/science/journal/03772217/237/3 http://www.sciencedirect.com/science/article/pii/b9780128110355000301 http://www.sciencedirect.com/science/article/pii/s0360835215004490 http://www.sciencedirect.com/science/article/pii/s0360835215004490 http://www.informaworld.com/smpp/title~db=all~content=t713597292 http://www.informaworld.com/smpp/title~db=all~content=t713597292~tab=issueslist~branches=20#v20 http://econpapers.repec.org/article/eeeejores/ international journal of engineering materials and manufacture (2021) 6(3) 195-201 https://doi.org/10.26776/ijemm.06.03.2021.11 de oliveira, d. , gomes, m.g., dos santos, a. g. and da silva, m.b. department of mechanical engineering, faculty of technology, university of brasilia, brazil. e-mail: oliveira.deborah@unb.br reference: de oliveira et al. (2021) influence of cutting fluid application frequency in micromilling cutting forces. international journal of engineering materials and manufacture, 6(3), 195-201. influence of cutting fluid application frequency in micromilling cutting forces de oliveira, d., gomes, m. g., dos santos, a. g. and da silva, m. b. received: 15 april 2021 accepted: 29 april 2021 published: 15 july 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract micromachining allows the production of parts and components on a micro scale with high precision and has become a key process to meet the growing demand for micro parts and micro components. to meet the quality requirements of the generated surfaces and reduce the cutting forces, strategies have been analysed, such as the use of the cutting fluid. therefore, this research aimed to verify the effect of the frequency of the use of cutting fluid during the micromilling of the inconel 718 alloy. for this purpose, an ultra-refined cemented carbide micro end mill coated with (al, ti) n and 400 µm in diameter was used. a spindle speed of 20,000 rpm, a cutting speed of 13.8 m/min, a feed per tooth of 5 µm/tooth and an axial depth of cut of 40 µm were used as cutting parameters. two frequencies of application of the cutting fluid were evaluated, corresponding to the flow rate of 40.7 and 270.0 ml/ h, in addition to the dry test. to measure the cutting forces, a kistler dynamometer with operating range of -5 kn to +10 kn was used. in addition, the process simulation was performed using the advantedge software by thirdwave systems. the results showed that the higher flow of the cutting fluid provided lower cutting forces and that, in dry machining, the cutting force increased significantly during the machining of a slot. keywords: micromilling, inconel 718, cutting fluid, cutting forces. 1 introduction researches in microfabrication processes are experiencing a rapid evolution due to the growing demand for microproducts with possible applications in optical, mechanical, electrical, medical and biochemical devices [1]. in this scenario, the micro machining process is an important technology to provide micro parts with the required precision [2]. according to saha et al. [3], micromachining allows the production of micro components with complex geometries, by removing material in the form of micro-chips and using a micro-tool with sharp edges. it is noteworthy that one of the characteristics that defines this process is related to the size of the tool. as an example, in micro milling, as exposed by saha et al. [4], the diameter of the micro-cutter usually ranges from 0.01 to 1.0 mm. micromachining has particularities that differentiate it from the conventional machining process due to the size effect. an important difference between the two processes is that, in micro machining, the undeformed chip thickness has a size comparable to the cutting-edge radius, exerting a strong influence on the chip formation mechanism [5]. thus, there is a minimum uncut chip thickness for chip formation and this varies between 0.25 and 0.33 of the tool edge radii [6]. in addition, considering that the reductions that occur in the micro-machining process, such as in the tool size and cutting parameters, do not occur with the workpiece grains, the chip formation can therefore occur through the shearing of a single or a few grains [7,8]. due to the presence of the size effect in the micromachining processes, the reduction of the undeformed chip thickness does not have the same effect on the cutting forces when compared with conventional processes. in this case, the influence of the thickness on the forces is uncertain, while the force is high due to the increase in the chip cross-section, it is reduced since in this condition the effective exit angle of the tool becomes more positive, which decreases the occurrence of ploughing, and consequently, decreases the value of ploughing force [8]. the machining force, as well as its components, are important output variables to be studied both in machining processes on a macro scale, as well as in micromachining, as it estimates the power required for cutting, as well as influence of cutting fluid application frequency in micromilling cutting forces 196 the forces that will act on the elements of the machine-tool. besides, they directly affect the ability to obtain tight tolerances, cutting temperature, and tool wear [9]. the machining force has three basic components that act on the cutting edge: cutting force, feed force, and passive force [10]. in addition to these components, in the micromilling process, there is the presence of the ploughing force. this force will be very present in this process due to the size effect. this is a deformation force that acts at the tip of the cutting tool and at the interface of the chip tool, being responsible for the significant increase in the specific cutting energy [11]. one way to reduce the forces present in the cut is to use cutting fluids, thus guaranteeing less tool wear and higher quality of machined surfaces [12]. according to de oliveira et. al [13] the cutting fluid must be applied at an appropriate rate, to ensure the homogeneous quality of the machined surface. in this work, the variation of the fluid application rate in the inconel 718 micromilling was investigated, and it was observed that by using the highest fluid application rate (200 pulses per minute) it was possible to guarantee its presence on the entire surface of the slot, thus improving its surface finish. ziberov et al. [14] when performing the micromilling of the ti-6al-4v alloy, observed that the application of cutting fluid improves the quality of the machined surfaces, by reducing the wear of the cutting tool. in addition, they noted that the presence of the fluid influenced the size of the burrs formed. demonstrating the great importance of using the cutting fluid in micromachining operations. in view of this, the present work was developed with the aim of evaluating the influence of the frequency of application of the cutting fluid in the micromilling process of the nickel alloy inconel 718. 2 materials and methods 2.1 workpiece material the workpiece material was the refractory nickel alloy inconel 718, its austenitic microstructure can be observed in figure 1. this alloy has high tensile strength, good chemical resistance, and the ability to operate continuously at high temperatures [15], table 1 contain some of the material properties and table 2 its chemical composition. the workpieces were machined to blocks of 15 mm x 20 mm x 15 mm. figure 1: inconel 718 microstructure [16] table 1: mechanical properties of inconel 718 [17] tensile strength yield strength young’s modulus hardness (hrc) room temp density melting range (º c) thermal conductivity (mpa) (mpa) (gpa) (g/cm 3 ) (w/mk) 1275 1034 200 40 8.22 1260 1336 11.4 table 2: chemical composition of inconel 718 [17] element c al ti cr fe ni nb mo percentage 0.04 0.50 0.90 19.00 18.50 50.66 5.10 5.30 de oliveira et al. (2021): international journal of engineering materials and manufacture, 6(3), 195-201. 197 2.2 micro cutting tools and machine tool the tool used in this work is a ultra-refined cemented carbide micro end mill (ms2msd0040) coated with (al, ti)n, 400 µm diameter, 2 flutes, manufactured by mitsubishi. the geometry of the tool is shown in figure 2, with some dimensions in millimetres. the machine-tool was the mini-mill / gx cnc, manufactured by minitech machinery corporation®. it has a maximum spindle speed of 60000 rpm, 4 axes with position resolution of 0.1 μm. this machine is equipped whit an mql system. the system was set to deliver the fluid at an air pressure of 33 psi (0.23mpa), and the cutting fluid selected was the coolube 2210ep, manufactured by unist. figure 2: micromill [18] 2.3 cutting parameters the experiment consisted in machining micro slots of 15 mm in the inconel 718. in order to continue the investigation proposed by de oliveira et al. [13], the same cutting parameters and lubrication conditions were selected, except the cutting speed. the cutting conditions are shown in table 3. the only different parameter from [13] is the cutting speed. this is because limitations of the dynamometer. it is important to mention that the different cutting fluid application frequency will result in different flow rates, with the first being 40.7 ml/h, and the second being 270.0 ml/h, which results in 30 and 200 pulses per minute, respectively. table 3: cutting parameters parameter value spindle speed n (rpm) 20 000 cutting speed vc (m/min) 13.8 feed per tooth fz (µm/tooth) 5 axial depth of cut ap (µm) 40 cutting fluid flow rate (ml/h) 00.0 (dry) 40.7 270.0 2.4 outputs to obtain the force results, a kistler dynamometer, model 9257b was used. this dynamometer has an operating range of -5 kn to +10 kn and can operate dynamically or almost statically [19]. its sensitivity is adjustable, being recommended to 0.02 n. this equipment has a low natural frequency of 3.5 khz [19], which limited its use for experiments with lower cutting speed since the frequency of the phenomenon of cutting is related to the number of teeth of the tool and the spindle rotation. therefore, the cutting speed used in this work was 13.8 m/min. after the signals were generated in the dynamometer, they passed through a kistler 5405a distribution box, later through a kistler conditioner / amplifier, model 504e and finally converted (analogue / digital) by a national instruments board, ni usb-66221, with 16 bits. the signals were acquired using a labview software with a frequency of 100 khz, to achieve an adequate trade-off between the quality of the signal and its intensity [20] subsequently the signals were treated and analysed using the matlab software. in order to verify the force measurements a computational simulation was performed using the advantedge by thirdwave systems. this is a software dedicated to machining operations and uses an explicit dynamic, thermomechanically coupled finite element model specialized. the material properties were obtained by the software library and the tool was modelled based in sem images and the manufacturer specifications. the tool was determined as a rigid body, with elements varying from 10.0 μm to 1.0 μm, the workpiece material was plastically and elastically influence of cutting fluid application frequency in micromilling cutting forces 198 deformable, having initial mesh parameters as 500 – 10 μm, and as the deformations occur the adaptative mesh could generate new smaller elements, reaching 0.4 μm. it is important to comment that the simulation was performed considering the same cutting parameters and for dry cutting. 3 results and discussion to verify the theory presented by de oliveira et al. [13], the cutting forces were obtained in similar conditions. this was selected once the cutting fluid is directly related to the excitations and forces of the system [21, 22]. in figure 3 is possible to observe one of the machined slots in two different regions. the left one in the red square presented worsened surface finish and adhered material in the slot surface, attributed to the lack of cutting fluid in this region during the cut. figure 4 contains the force signals during the cutting, for dry machining, the two different lubrication conditions and a comparison of the three lubricating atmospheres. the force was measured in the cutting direction and the negative values are the forces during cutting and the positive values are due to ploughing. figure 4a shows the rough signal for dry micromachining. the cutting forces increase from about 4.6 n to about 8.7 n during the micromachining, indicating that there was a significant tool wear in the machined length 15 mm. when comparing the force result, figure 4a with figure 4c, dry condition with the test with cutting fluid applied at high frequency, it is possible to observe that the initial force is similar. however, when fluid is applied at 270.0 ml/h flow rate, there is no significant increase in the cutting force with the machined length, and the maximum force was about 6.7 n. this different behaviour indicates that the fluid has reduced the cutting forces and, consequently, the wear rates of the micromill. focusing on the low frequency of cutting fluid application, it is possible to notice in figure 4b that the initial value of the force is high and has peaks of force, which may be related to the lack of cutting fluid at the chip tool interface. the results obtained are in accordance with the literature, which points out that the application of cutting fluid when machining inconel 718 favours the process since the lubrication prevents the material from adhering to the microtool, which also results in less friction which means lower cutting forces [23, 24]. these effects reduce the diffusion of the workpiece material to the microtool material, a common effect when machining inconel 718. the combined reduction of these factors helps not only in the quality of the slot, as presented in figure 3, but in increasing the life of the micromill [25, 26]. as mentioned, computational simulation was performed with the intention to verify the quality of the force signals obtained experimentally. the computational results proved to be robust and the obtained results were similar to the experimental ones. in figure 5 it is possible to observe the results of force for one single revolution of the tool, in which the micromill had not yet fully entered the part, representing the beginning of the slot. however, it is important to remark that this signal is not equivalent to the first contact because a pre-boolean cut was used, so that the simulation started with both edges inside the part. when considering the beginning of the micromilling, it is possible to notice that the cutting forces when the micromill is starting the slot are quite reduced. according to wang et al. [27], for a 100 µm micro-cutter, with a depth of cut of 50 µm, the initial forces vary from 0.2 n for a chip load of 0.5 µm to approximately 0.8 n for chip load 4.0 µm. these results are in accordance with the ones presented here. regarding the application of cutting fluid, it was possible to prove quantitatively the benefits of its use for inconel 718 micromilling operations. figure 3: micromilled slot with different surface finish due to the lack of cutting fluid [13] de oliveira et al. (2021): international journal of engineering materials and manufacture, 6(3), 195-201. 199 a) force signal for dry machining b) force signal for machining with 40.7 ml/h c) force signal for machining with 270.0 ml/h d) comparison of forces for different atmospheres in micromilling figure 4: force signals for different cooling-lubrication conditions figure 5: computational results for cutting force. influence of cutting fluid application frequency in micromilling cutting forces 200 4 conclusions after the experimental and computational trials about micromilling inconel 718 with a 400 μm diameter cemented carbide micromill, the following conclusions can be draw: 1. the computational results presented similar results to the experimental, indicating that the cutting forces were correctly obtained. 2. the cutting force increase within one slot when dry machining, from 4.6 n to 8.7 n, indicating high wear in the microtool. 3. low frequency presented intermediate results and the presence of force pikes can be related to the absence of cutting fluid in some regions of the slot. 4. the higher flow rate resulted in the lower cutting forces with the force in the end of the slot being 6.7 n, which near 25% of reduction when comparing to the dry cut. acknowledgement the authors are thankful to capes, cnpq, fapemig, to faculty of mechanical engineering of federal university of uberlandia and to the department of mechanical engineering, faculty of technology, university of brasilia. references 1. aurich, j.c., reichenbach, i.g. & schuler, g.m. manufacture and application of ultra-small micro end mills. (2012). cirp annals manufacturing technology, 61(1), 83-86. 2. li, w., zhou, z.x., huang, x.m., he, z. w. & du, y. (2014). development of a high-speed and precision microspindle for micro-cutting. international journal of precision engineering and manufacturing, 15(11), 23752383. 3. saha, s., deb, s. & bandyopadhyay, p.p. (2020). an analytical approach to assess the variation of lubricant supply to the cutting tool during mql assisted high speed micromilling. journal of materials processing technology, 285, 116783. 4. saha, s., kumar, a.s., deb, s. & bandyopadhyay, p.p. (2020). an investigation on the top burr formation during minimum quantity lubrication (mql) assisted micromilling of copper. materials today: proceedings, 26, 18091814. 5. aramcharoen, a. & mativenga, p.t. (2009). size effect and tool geometry in micromilling of tool steel. precision engineering, 33, 402–407. 6. de oliveira, f.b., rodrigues, a.r., coelho, r.t. & de souza, a.f. (2015). size effect and minimum chip thickness in micromilling. international journal of machine tools & manufacture, 89, 39-54. 7. câmara, m.a., rubio, j.c.c., abrão, a.m. & davim, j.p. (2012). state of the art on micromilling of materials, a review. journal of materials science & technology, 28(8), 673-685. 8. bissacco, g., hansen, h.n. & chiffre,l.d. (2005). micromilling of hardened tool steel for mould making applications. journal of materials processing technology, 167, 201-207. 9. diniz, a.e., marcondes, f.c & coppini, n.l. (2008). “material machining technology”, artliber. 10. rahman, s. m & liow, j. l. (2010). modelling and simulation of cutting forces in micromachining. in key engineering materials (vol. 443, pp. 652-656). trans tech publications ltd. 11. arif, m & rahman, m. (2014). fundamentals and modeling of micro-end milling operation. 12. irani r.a., bauer, r.j & warkentin, a. (2005). a review of cutting fluid application in the grinding process. international journal of machine tools & manufacture, 45, 1696-1705. 13. de oliveira, d., gomes, m. c & da silva, m. b. (2020). influence of cutting fluid application frequency on the surface quality of micromilled slots on inconel 718 alloy. procedia manufacturing, 48, 553-558. 14. ziberov, m., da silva, m. b., jackson, m., & hung, w. n. (2016). effect of cutting fluid on micromilling of ti6al-4v titanium alloy. procedia manufacturing, 5, 332-347. 15. reed, r. c. the superalloys fundamentals and applications. 1.ed. new york: cambridge university press, 2006. 392p. 16. de oliveira, d., de paiva, r.l., da silva, r.b. & castro, p.h.c. (2020) assessment of the grindability of inconel 718 under different coolant delivery techniques. journal of the brazilian society of mechanical sciences and engineering, 42(20). 17. de oliveira,d., gomes, m.c. & da silva, m.b. (2019) spheroidal chip in micromilling. wear, 426-427, 16721682. 18. mitsubishi, mitsubishi carbide. (2018, september). retrieved from https://www.mitsubishicarbide.com/mmus/catalog/pdf/lj/lj403a.pdf. 19. kistler, multicomponent dynamometer. (209a, july). retrieved from https://www.kistler.com/?type=669&fid=95592&model=document&callee=frontend. 20. abeni, a., lancini, m. & attanasio, a. (2019) characterization of machine tools and measurement system for micromilling, nanotechnology and precision engineering, 2, 23–28. de oliveira et al. (2021): international journal of engineering materials and manufacture, 6(3), 195-201. 201 21. liu, d., wang, g., yu, j. & rong, y. (2017). molecular dynamics simulation on formation mechanism of grain boundary steps in micro-cutting of polycrystalline copper. computational materials science, 126, 418–425. 22. mittal, r.k., kulkarni, s.s. & singh, r. (2017). effect of lubrication on machining response and dynamic instability in high-speed micromilling of ti-6al-4v. journal of manufacturing processes, 28, 413–421. 23. ucun, i., aslantas, k., bedir, f. (2013). an experimental investigation of the effect of coating material on tool wear in micro milling of inconel 718 super alloy. wear, 300, 8-19. 24. zhou, l., peng, f.y., yan, r., yao, p.f., yang, c.c. & li, b. (2015). analytical modeling and experimental validation of micro end-milling cutting forces considering edge radius and material strengthening effects. international journal of machine tools & manufacture, 97, 29-41. 25. dudzinski, d., devillez, a., moufki, a., larrouque`re, d., zerrouki, v. & vigneau, j. (2004). a review of developments towards dry and high speed machining of inconel 718 alloy. international journal of machine tools & manufacture. 44, 439-456. 26. ezugwu, e. o. (2005) key improvements in the machining of difficult-to-cut aerospace superalloys. international journal of machine tools & manufacture, 45, 1353–1367. 27. wang, f., cheng, x., liu, y., yang, x. & meng, f. (2017). micromilling simulation for the hard-to-cut material. 13th global congress on manufacturing and management, gcmm 2016, procedia engineering, 174, 693-699. doi: 10.1016/j.proeng.2017.01.209 international journal of engineering materials and manufacture (2017) 2(3) 37-48 https://doi.org/10.26776/ijemm.02.03.2017.01 m. h. hasan department of mechanical and industrial engineering ryerson university, canada e-mail: hasibulhasan@ryerson.ca s. ahmed department of robotics and mechatronics engineering kazi motahar hossain bhaban university of dhaka, dhaka 1000, bangladesh e-mail: shugataahmed.rme@du.ac.bd reference: hasan, m. h., and ahmed, s. (2017). wear resistance performance of conventional and non-conventional wind turbine blades with tin nano-coating. international journal of engineering materials and manufacture, 2(3), 37-47. wear resistance performance of conventional and non-conventional wind turbine blades with tin nano-coating muhammad hasibul hasan and shugata ahmed received: 13 april 2017 accepted: 08 july 2017 published: 15 september 2017 publisher: deer hill publications © 2017 the author(s) creative commons: cc by 4.0 abstract efficiency and durability are critical issues that affect widely-adopted aerofoil-power generator as a sustainable source of electrical power. even though high wind power density can be achieved; installing wind turbines in desert condition has difficulties including thermal variation, high turbulence and sand storms. sand blasting on turbine blade surface at high velocities causes erosion resulting turbine efficiency drop. damage-induced erosion phenomena and aeroelastic performance of the blades needed to be investigated. suitable coating may prevent erosion to a great extent. a numerical investigation of erosion on naca 4412 wind turbine blade has been performed using commercial computational fluid dynamics software ansys fluent 14.5 release. discrete phase model (dpm) has been used for modelling multi-phase flow of air and sand particles over the turbine blade. governing equations have been solved by finite volume method (fvm). conventional 30-70% glass fibre resin and non-conventional jute fibre composite have been used as turbine blade material. sand particles of 0.3 mm diameter have been injected from 20° , 30°, 45°, 60° and 90° angles at 50℃ temperature. erosion rate, wall shear stress and strain rate have been calculated for different wind velocities and impingement angles. simulation results for higher velocities deviate from the results observed at lower wind velocities. in simulation, erosion rate is highest for 30 0 impingement angle at low wind velocities, which has been validated by experiment with a mean absolute error (mae) of 5.56%. erosion rate and wall shear stress are higher on jute composite fibre than glass fibre resin. developed shear stress on wind turbine blade surface is highest for 20 0 impingement angle at all velocities. on the other hand, exerted pressure on turbine blade surface is found highest for 90° angle of attack. experimental results, with or without titanium nitride(tin) nano-coating, also revealed that surface roughness augments with increasing impingement angles. nano-coating (tin) by rf sputtering technique reduced the surface roughness significantly as oppose to uncoated samples. highest roughness has been observed on uncoated blade surface collided with 0.3-0.69 mm diameter brown aluminium oxide particles. keywords: turbine blade, aerofoil, nano coating, wear, wear resistance, power generation, turbine efficiency, fibre composite turbine blade 1. introduction combustion of bio-fuels generates greenhouse gases. releasing greenhouse gases is one of the major reasons of atmospheric temperature rise. moreover, amount of underground petroleum storage is limited. hence, renewable energy, such as wind, solar, geothermal etc., is becoming popular day by day as alternative sources. wind energy is clean, available and easy to convert to electrical energy. wind turbines are used to generate electrical power from wind energy. however, selecting turbine blade material is a critical issue. moreover, in desert condition air flows with sand particles at relatively high velocities. sand blasting on turbine blade surface results significant erosion. hence, a sharp decrement of turbine efficiency is observed with time. wear resistance performance of conventional and non-conventional wind turbine blades with tin nano-coating 38 nomenclature 𝑎 particle impact angle (°) 𝐴𝑓𝑎𝑐𝑒 surface area of impacted wall boundary cell (𝑚𝑚 2) 𝑑𝑝 particle diameter (𝑚𝑚) �⃗� gravitational acceleration (𝑚𝑠 −2) 𝑘 turbulence kinetic energy (𝑚2𝑠 −2) �̇�𝑝 particle mass flow rate (𝑘𝑔𝑠 −1) 𝑛 material independent index 𝑃 pressure (𝑃𝑎) 𝑅𝑒 reynolds number 𝑅𝑒𝑟𝑜𝑠𝑖𝑜𝑛 erosion rate (𝑘𝑔𝑚 −2𝑠 −1) 𝑇 temperature (℃) �⃗⃗� velocity of air (𝑚𝑠 −1) �⃗⃗�𝑝 particle velocity (𝑚𝑠 −1) 𝑣𝑖 particle impact velocity (𝑚𝑠 −1) 𝛼 volume fraction of air 𝜖 turbulence kinetic energy dissipation rate (𝑚2𝑠 −3) 𝜃 solid domain temperature (℃) 𝜇 dynamic viscosity (𝑁. 𝑠𝑚−2) 𝜌 density of air (𝑘𝑔𝑚−3) 𝜌𝑝 particle density (𝑘𝑔𝑚 −3) numerous trials for selecting proper wind turbine blade materials have been remarked in the literature. mishnaevsky et al. [1] studied the usability of timber as a turbine blade material. their investigation represents a framework for fabrication, testing and installation of timber blades. composite materials are also getting attentions for fabricating wind turbine blades due to their low cost and attractive properties. polymer composites had been considered by researchers to enhance surface resistance to wear such as carbon fibres, short aramids or glass [2-7], polyetheretherketone (peek) [8], polyphenylene sulfide (pps) [9], polyoxymethylene (pom) [10], polyamide (pa) [11] etc. patnaik et al. [12] numerically and experimentally investigated erosion rate on zinc-aluminum alloy metal (za27) filled with titania (tio2) for different particle impact velocity, size, temperature and impingement angle. they observed that highest erosion rate occurs at 60 0 impingement angle. erosion rate on unfilled base metal was found higher than reinforced alloy. erosion on composite material was also investigated experimentally by drensky et al. [13]. it was found that mass loss of the material is highest for 45° impact angle. wind velocity, particle size and fibre orientation also have great influence on mass loss. simulation was carried out by fiore et al. [14] to investigate erosion on wind turbine blade for insects and sand particles impact. maximum erosion rate was detected on blade’s low pressure side. wind tunnel testing was conducted by gaudern et al. [15] to figure out erosion patterns on wind turbine blade surface under varying conditions. hamed et al. [16] also explored surface damage of turbine blade both numerically and experimentally. their results show that erosion and surface roughness enhance with increasing impact angle and particle size. foley et al. [17] studied erosion behaviour of steel aisi 4340 and found that for the same material hardness, the erosion at impact angle of 30 0 was much greater than at 90 0 . on the other hand, hutchings [18] reported erosion peaks at 90° for aisi 52100 steel. e. rodríguez et al. [19] found three different wear regions based on impact angles and hardness. higher amount of wear found for 10° and 20° impact angles at lower hardness value, while, for impact angles of 60°, 75° and 90°, amount of wear is high for higher hardness value. for impact angles of 30° and 40°, wear is almost same for all hardness values. an effective way to prevent erosion on wind turbine blade is to provide coating. rico et al. [20] accomplished low wear on sae-42 steel by depositing al2o3 – 13% tio2 coating. liang et al. [21] substantially improved damping properties of wind turbine blade using carbon nanofibre nanocomposite coating. nano/polymer coating is promising for preventing erosion to a great extent. zhang et al. [22] tested silica filled transparent acrylate-based coatings and remarked that nanosilica particles improve erosion resistance properties. figure 1 illustrates coating with different percentage of nanosilica particles. in this paper, a static naca 4412 single wind turbine blade under desert condition has been simulated by software and laboratory setup. numerical investigation has been carried out by ansys fluent 14.5 release. in software, discrete phase model (dpm) has been used to simulate the multiphase flow of air and sand particles. erosion rate, development of shear stress and strain on wind turbine blade surface have been investigated. aerodynamic performances of turbine blade have also been explored. experiment has been carried out using air jet erosion tester. simulation results show good agreement with experimental data. hasan and ahmed (2017): international journal of engineering materials and manufacture, 2(3), 37-48 39 figure 1: tem micrograph of nano/polymer coating with (a) 10wt% and (b) 40wt% nanosilica particles [22]. 2. mathematical model discrete phase model (dpm) has been used to simulate the flow of air and sand particles. in dpm, the fluid phase is considered as continuum and solid particles are treated as discrete phase. discrete solid particles are tracked in the flow field in a lagrangian frame of reference, where governing equations are solved for a single particle. on the other hand, transport equations for per unit volume of continuum phase is derived, which is eulerian approach for modelling multiphase flow. the force balance equation for a single sand particle is following: 𝑑𝑢𝑝 𝑑𝑡 = 𝐹𝐷 (�⃗⃗� − �⃗⃗�𝑝) + �⃗⃗�(𝜌𝑝−𝜌) 𝜌𝑝 + �⃗� (1) as sand particles are very small, it is considered that no gravitational force is acting on them. hence, gravitational acceleration �⃗� = 0. the term 𝐹𝐷 (�⃗⃗� − �⃗⃗�𝑝) defines the drag force/ unit mass of sand particle where 𝐹𝐷 = 18𝜇𝐶𝐷𝑅𝑒 𝜌𝑝𝑑𝑝 2 24 (2) relative reynolds number is defined as 𝑅𝑒 = 𝜌𝑑𝑝|�⃗⃗⃗�𝑝−�⃗⃗⃗�| 𝜇 (3) the governing equations for air is derived by eulerian method. continuity equation is the following: 𝜕(𝛼𝜌) 𝜕𝑡 + ∇(𝛼𝜌�⃗⃗�) = 0 (4) conservation of momentum equation: 𝜕(𝛼𝜌�⃗⃗⃗�) 𝜕𝑡 + 𝛻(𝛼𝜌�⃗⃗��⃗⃗�) = −𝛼𝛻𝑃 + 𝛻𝜏 (5) standard 𝑘 − 𝜀 turbulence model [12] is used for turbulence flow modelling. equations related to turbulence: 𝜕(𝜌𝑘) 𝜕𝑡 + ∇(𝜌𝑘𝑢) = ∇(𝛼𝑘 𝜇𝑒𝑓𝑓 ∇𝑘) + 𝐺𝑘 + 𝐺𝑏 − 𝜌𝜀 − 𝑌𝑀 + 𝑆𝑘 (6) 𝜕(𝜌𝜀) 𝜕𝑡 + ∇(𝜌𝜀𝑢) = ∇(𝛼𝜀 𝜇𝑒𝑓𝑓 ∇𝑘) + 𝐶1𝜀 𝜀 𝑘 (𝐺𝑘 + 𝐶3𝜀 𝐺𝑏 ) − 𝐶2𝜀 𝜌 𝜀2 𝑘 − 𝑅𝜀 + 𝑆𝜀 (7) in equation (6) and (7) 𝐺𝑘 = generation of turbulence kinetic energy due to the mean velocity gradients 𝐺𝑏 = generation of turbulence kinetic energy due to buoyancy 𝑌𝑀 = contribution of the fluctuating dilatation in compressible turbulence to the overall dissipation rate 𝑆𝑘 = source term for turbulence kinetic energy 𝑆𝜀 = source term for turbulence kinetic energy dissipation rate the erosion model is included in dpm. erosion rate is defined by following equation: 𝑅𝑒𝑟𝑜𝑠𝑖𝑜𝑛 = ∑ �̇�𝑝𝐶(𝑑𝑝)𝐹(𝑎)𝑣𝑖 𝑛 𝐴𝑓𝑎𝑐𝑒 𝑁𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒𝑠 𝑝=1 (8) wear resistance performance of conventional and non-conventional wind turbine blades with tin nano-coating 40 here, 𝐶(𝑑𝑝) is particle diameter function and 𝐹(𝑎) is impact angle function. following boundary conditions are applied in the computational domain to solve the governing equations numerically: inlet: velocity of air at y-direction, 𝑢𝑦 = 𝑢𝑖𝑛; other velocity components, 𝑢𝑥 = 𝑢𝑧 = 0; temperature of air and sand particles, 𝑇𝑖𝑛 = 50℃; mass flow rate of sand particles, �̇� = �̇�𝑖𝑛. outlet: pressure, 𝑝 = 𝑝𝑜𝑢𝑡. atmospheric pressure is defined at domain outlet. walls: fluid velocity adjacent to stationary domain walls, 𝑢 = 0. outer walls are considered thermally insulated. hence, temperature gradient normal to the wall, 𝜕𝜃 𝜕𝑛 = 0. 3. numerical simulation 3.1 meshing and grid independent test a hybrid mesh has been generated by ansys workbench. figure 2 shows meshing of turbine blade surface and the fluid domain with 60° impingement angle. the grid consists of hexahedron elements. minimum number of elements should be considered in the simulation to minimize computational time. to find out optimum number of elements, grid independent test has been carried out. erosion rate has been observed for 1.3 × 105 to 1.5 × 105 number of elements and relative error has been calculated, which are shown in table 1. finally, 144828 number of cells has been selected for simulation with a relative error of 1.36%. 3.2 solution methods governing equations have been solved numerically by finite volume method (fvm). second order upwind scheme has been used for discretization. pressure-velocity coupling equation has been solved by semi-implicit method for pressure linked equations (simple) algorithm, developed by patankar and spalding [13]. (a) (b) (c) figure 2: (a) wind turbine blade surface meshing; meshing of fluid domain with 60° impingement angle (b) crosssectional view, (c) three dimensional view. table 1: grid independence test results no. of elements rerrosion (kg.m -2 .s) relative error (%) 134425 1.31 × 10−7 13.74 137854 1.38 × 10−7 7.97 144828 1.47 × 10−7 1.36 148710 1.44 × 10−7 3.47 153318 1.49 × 10−7 - hasan and ahmed (2017): international journal of engineering materials and manufacture, 2(3), 37-48 41 4. experimental study 4.1 samples and nanocoating glass fibre 6 x 2 cm samples were collected from the 3 mm thick turbine blades and jute reinforced epoxy resin composite samples were prepared in the laboratory. multiple acetone wash removed dusts and gel coat of the turbine blades, if any. rf sputtering technique was adopted for the coating while target material was 99.99% titanium. gas flow rate for argon (ar) was 50 sccm and for nitrogen (n) was 5 sccm. duration of each deposition was 60 minutes. 4.2 sand blasting and roughness analysis sand blasting machine with a blasting pressure of 50 psi (20 m/sec) and 75 psi (35 m/sec) were used to erosion rate calculation. the test rig is shown in figure 3. target samples were kept 20cm away from the nozzle tip and the duration of sand blasting was 10 seconds for each sample. brown aluminium oxide of 0.30 to 0.70 mm particles were used as sand particles. sand blasted samples were analysed by mitutoyo surftest (sj-301) surface roughness analyser. jis b0601(2001) method was adopted and gauss filter was used to calculate the roughness (ra) value. 5. results and discussion 5.1 simulation results 5.1.1 erosion rate figure 4 shows the contour plot of erosion on wind turbine blade surface of glass fibre resin for 60 ms−1 wind velocity and 90° impingement angle. it is observed that highest erosion rate on turbine blade surface is 1.4 × 10−6 kgm−2s−1. in figure 5, highest erosion rate on wind turbine blade surface of glass fibre resin is plotted for different velocities and impingement angles. it is found that erosion rate elevates with increasing wind velocity for all angles. at low wind velocities, erosion rate is highest for 30° impingement angle, which is followed by 90°, 60°, 45° and 20° angles respectively. however, erosion rate at high velocities for 90° and 30° angles are same. exceptionally, at high velocities, erosion rate for 45° angle is higher than 60° impingement angle. at 65 ms−1 wind velocity, erosion rate for 45° angle is 8 × 10−7 kgm−2s−1, while for 60° angle it is 6 × 10−7 kgm−2s−1. in figure 6, erosion rate for 30° impingement angle is plotted for jute fibre composite and 30-70% glass fibre resin. it shows clearly that erosion rate on jute fibre composite blade is higher than glass fibre resin. 5.1.2 wall shear stress in figure 7, development of shear stress on wind turbine blade surface is shown by contour plot. it is visible that shear stress is very high at the edge of the blade. hence, the possible damage from wind flow may occur at the blade edge. similar to erosion rate, shear stress on the blade surface also elevates with increasing wind velocity for all angles, which is observed in figure 8. wall shear stress for 20° impingement angle is much higher than other angles. exceptionally, wall shear stress for 90° angle at 65 ms−1 wind velocity is higher than 30° and 60° angles. however, at other velocities, shear stresses for 30° and 60° angles are found higher than 90° angle. at 40 ms−1 wind velocity, shear stress for 60° impingement angle is about 50 pa which is much higher than 30° angle. however, at higher velocities, shear stresses for 30° and 60° angles are found almost same. lowest shear stress is developed for 45° angle at all velocities. shear stress is also higher on jute fibre composite blade than glass fibre resin as shown in figure 9. figure 3: test facility for sand blasting on wind turbine blade prototype wear resistance performance of conventional and non-conventional wind turbine blades with tin nano-coating 42 figure 4: erosion on wind turbine blade surface of glass fibre-resin for 60 ms−1 wind velocity and 90° impingement angle figure 5: erosion rate vs. wind velocity curve for glass fibre resin at different angle of attacks hasan and ahmed (2017): international journal of engineering materials and manufacture, 2(3), 37-48 43 figure 6: rate of erosion on two different composite materials for 30° angle of attack figure 7: shear stress on wind turbine blade surface of glass fibre-resin for 65 ms−1 wind velocity and sand injection from 90° angle wear resistance performance of conventional and non-conventional wind turbine blades with tin nano-coating 44 figure 8: wall shear stress vs. wind velocity curve for glass fibre resin at different angle of attacks figure 9: development of shear stress on two different composite materials for 30° angle of attack 5.1.3 strain rate in figure 10, alike wall shear stress, strain rate is also high at the edge of the blade. again, from figure 11, it is seen that strain rate rises with the increment of wind velocity. strain rate is found highest for 60° angle of attack at all velocities, which is followed by 30°,20°, 45° and 90° angles respectively. however, at 65 ms−1 wind velocity, same strain rate is observed for 45° and 90° angles. hasan and ahmed (2017): international journal of engineering materials and manufacture, 2(3), 37-48 45 5.1.4 pressure distribution in figure 12, pressure distribution on 30-70% glass fibre resin blade surface are shown for various angle of attacks has been plotted. it is perceived that highest pressure developed on blade surface declines with increasing angle. however, for 90° angle of attack, highest pressure developed on the blade suddenly rises to 29.5 kpa, which is larger than pressures developed at all other angles. figure 10: strain rate on wind turbine blade surface of glass fibre-resin for 65 ms−1 wind velocity and sand injection from 60° angle figure 11: strain rate vs. wind velocity curve for glass fibre resin wear resistance performance of conventional and non-conventional wind turbine blades with tin nano-coating 46 figure 12: highest pressure vs. injection angle curve for glass fibre resin, 35 ms−1 wind velocity, 0.3 mm diameter sand particle injection at 0.5 kgs−1 mass flow rate. 5.2 experimental results 5.2.1 comparison with simulation results in figure 13, both experimental and simulation results of erosion rate for 5⁰, 30⁰ and 60⁰ impingement angles have been plotted. simulation results show good agreement with experimental data for 5⁰ and 60⁰ angles. however, for 30⁰ angle, erosion rate is observed higher in experiment. the mean absolute error (mae) is defined using following equation: 𝑀𝐴𝐸 = 1 𝑀 ∑ |𝑅𝑒𝑟𝑜𝑠𝑖𝑜𝑛,𝑝𝑟𝑒𝑑−𝑅𝑒𝑟𝑜𝑠𝑖𝑜𝑛,𝑒𝑥𝑝| 𝑅𝑒𝑟𝑜𝑠𝑖𝑜𝑛,𝑒𝑥𝑝 × 100% (9) here, m represents number of data points. calculated mae for 30° impingement angle is 5.56%. figure 13: comparison of experimental and simulation results for erosion rate at different angle of attacks hasan and ahmed (2017): international journal of engineering materials and manufacture, 2(3), 37-48 47 5.2.2 surface roughness surface roughness increases almost linearly with increasing impingement angle, which can be apprehended from figure 14. surface roughness on uncoated blade surface collided with 0.3-0.69 mm diameter particles is highest, which is expected. surface roughness is found low for finer particle sizes. figure 14: experimental results of surface roughness vs. angle of attacks for different coated and uncoated surfaces 6. conclusions rate of erosion, development of shear stress and strain rate on wind turbine blade surface in desert conditions have been explored. pressure distribution on wind turbine blade for various injection angles has also been observed. major findings from numerical and experimental investigations are following: 1. in both simulation and experiment, erosion rate from wind turbine blade surface is found highest for 30° impingement angle. 2. shear stress development on wind turbine blade surface is highest for 20° angle and lowest for 45° angle. although strain rate has been found lowest for 90° impingement angle, it is also very low for 45° angle. 3. erosion rate on glass fibre resin has been found lower than jute fibre composite. hence, it is more suitable as a wind turbine blade material from erosion perspective. 4. pressure distribution on turbine blade surface is highest for 90⁰ angle of attack. 5. surface roughness increases linearly with increment of impingement angle. as expected, surface roughness observed on uncoated blade surface is higher than coated surfaces. acknowledgement this research was funded by ministry of higher education, malaysia under research grant frgs 14-131-0372. the authors are grateful to those who contributed directly and indirectly in producing this paper. references 1. mishnaevsky, l., freere, p., sinha, r., acharya, p., shrestha, r., & manandhar, p. (2011). small wind turbines with timber blades for developing countries: materials choice, development, installation and experiences. renewable energy, 36(8), 2128-2138. 2. stachowiak, g.w. and batchelor, a.w. 2001. engineering tribology, 2nd, boston: butterworth-heinemann. wear resistance performance of conventional and non-conventional wind turbine blades with tin nano-coating 48 3. friedrich, k. 1997. wear performance of high temperature polymers and their composites. crc press, : 221– 246. 4. briscoe, b.j. 1993. the tribology of composite materials: a preface. adv. compos. tribol, 8: 3–15. 5. hager, a.m. and davies, m. 1993. short-fibre reinforced, high temperature resistant polymers for a wide field of tribological applications. adv. compos. tribol, 8: 107–157. 6. kong, c., bang, j., & sugiyama, y. (2005). structural investigation of composite wind turbine blade considering various load cases and fatigue life. energy, 30(11), 2101-2114. 7. joosse, p. a., van delft, d. r. v., kensche, c., hahn, f., jacobsen, t., & van den berg, r. (2000, january). economic use of carbon fibres in large wind turbine blades. in proceedings of aiaa/asme wind energy symposium. reno, nv. 8. bahadur, s. and gong, d. 1992. the role of copper compounds as fillers in the transfer and wear behavior of polyetheretherketone. wear, 154: 151–165. 9. schwartz, c.j. and bahadur, s. 2001. the role of filler deformability, filler polymer bonding, and counterface material on the tribological behavior of polyphenylene sulfide (pps). wear, 251: 1532–1540. 10. yu, l., yang, s., wang, h. and xue, q. 2000. an investigation of the friction and wear behaviors of micrometer copper particle-filled polyoxymethylene composites. j. appl. polymer sci, 19: 2404–2410. 11. bahadur, s. and kapoor, a. 1992. the effect of znf2, zns and pbs fillers on the tribological behavior of nylon 11. wear, 155: 49–61. 12. a. patnaik, t. g. mamatha, s. biswas, & p. kumar, (2012). damage assessment of titania filled zinc–aluminum alloy metal matrix composites in erosive environment: a comparative study. materials & design, 36 (2012), 511521. 13. drensky, g., hamed, a., tabakoff, w., & abot, j. (2011). experimental investigation of polymer matrix reinforced composite erosion characteristics. wear, 270(3), 146-151. 14. fiore, g., & selig, m. s. a simulation of operational damage for wind turbine blades. 15. n. gaudern, a practical study of the aerodynamic impact of wind turbine blade leading edge erosion. journal of physics: conference series, 524(1) (2014). 16. a. a. hamed, w. tabakoff, r. b. rivir, k. das & p. arora. turbine blade surface deterioration by erosion. journal of turbomachinery, 127(3) (2005), 445-452. 17. foley, t., & levy, a. (1983). the erosion of heat-treated steels. wear, 91(1), 45-64. 18. hutchings, i. m. (1992). tribology: friction and wear of engineering materials. 19. rodríguez, e., flores, m., pérez, a., mercado-solis, r. d., gonzález, r., rodríguez, j., & valtierra, s. (2009). erosive wear by silica sand on aisi h13 and 4140 steels. wear, 267(11), 2109-2115. 20. rico, a., poza, p., & rodríguez, j. (2013). high temperature tribological behavior of nanostructured and conventional plasma sprayed alumina-titania coatings. vacuum, 88, 149-154. 21. liang, f., gou, j., kapat, j., gu, h., & song, g. (2011). multifunctional nanocomposite coating for wind turbine blades. international journal of smart and nano materials, 2(3), 120-133. 22. zhang, h., tang, l., zhang, z., gu, l., xu, y., & eger, c. (2010). wear-resistant and transparent acrylate-based coating with highly filled nanosilica particles. tribology international, 43(1), 83-91. 23. b. e. launder and d. b. spalding. lectures in mathematical models of turbulence. academic press, london, england. 1972. 24. s. v. patankar and d. b. spalding, a calculation procedure for heat, mass and momentum transfer in threedimensional parabolic flows. international journal of heat and mass transfer, 15(10) (1972), 1787-1806. international journal of engineering materials and manufacture (2022) 7(2) 54-60 https://doi.org/10.26776/ijemm.07.02.2022.02 mohammad yeakub ali 1 , md. abdul mazid 2 , abdus sabur 3 and mohamed abd rahman 4 1 mechanical engineering programme area, universiti teknologi brunie, gadong be 1410, brunei darussalam 2 school of engineering and technology, central queensland university, australia 3 ministry of fisheries and livestock, bangladesh secretariat, dhaka, bangladesh 4 department of manufacturing and materials engineering, international islamic university malaysia, po box 10, 50728 kuala lumpur, malaysia e-mail: yeakub.ali@utb.edu.bn reference: ali et al. (2022). comparative study of material removal rate of single-spark and multi-spark micro-edm of copper. international journal of engineering materials and manufacture, 7(2), 54-60. comparative study of material removal rate of single-spark and multispark micro-edm of copper mohammad yeakub ali 1 , abdul md mazid 2 , abdus sabur 3 and mohamed abd rahman 4 received: 03 april 2022 accepted: 13 april 2022 published: 16 april 2022 publisher: deer hill publications © 2022 the author(s) creative commons: cc by 4.0 abstract micro-electro discharge machining (micro-edm), a noncontact material removal process, is a well-established technique for making mold cavity on any workpiece materials having a minimal electrical conductivity of 0.1 scm -1 . the spark between tool electrode (-ve) and workpiece electrode (+ve) removes materials mostly from workpiece. knowing the time and amount of material removed in a single spark, mrr can be estimated. a number of analytical study have been reported for the estimation of mrr based on the ideal situation single-spark erosion. in case of multi-spark micro-edm, charging and discharging do not always follow the ideal conditions of the circuit and a lot of unwanted pulses such as arching and short circuit are produced which in turn reduce the effective number of pulses per second. moreover, in rc pulse micro-edm, the discharges are not uniform and the current and voltage are not constant with time. as a consequence, the performances estimated based on single-spark erosion formula could be misleading in multi-spark cases. this paper presents an analytical estimation of mrr as a function of machining parameters capacitance and voltage for single spark which is then compared with the multi-spark erosion of rc pulse micro-edm. the single spark erosion rate is estimated using the electro-thermal theories in which charging and discharging duration are derived from the rc pulse time constant and the number of sparks per unit time is counted from the single spark duration. the expression of single spark erosion volume is estimated using heat transfer equations. it is also difficult to conduct single-spark edm experiment and it has very little practical implications. experiments are conducted to investigate the multi-spark erosion rate. it is shown that, theoretically, the number of sparks depends on the capacitance and resistance of the circuit. however, in multi-spark erosion, it is found that the number of effective sparks depend not only the capacitance and voltages but also the conditions of micro-edm such as the workpiece and tool materials, flushing conditions, depth of cut. it is shown that the multi-spark mrr is almost half of the calculated value which is found using the equation of single spark mrr in micro-edm of copper. therefore, the single spark erosion formula needs to be adjusted for each of the workpiece to incorporate with the multi-spark erosion in real conditions. keywords: micro-electro discharge machining, material removal rate, time constant, multi-spark, nonconductive ceramic nomenclature c = capacitance (f) cp = specific heat at constant pressure (j/kgk) e = total circuit energy per spark (j) ew = energy absorbed by workpiece (j) hm = heat of melting (j/kg) hv = heat of vaporization (j/kg) k = fraction of total energy consumed for material removal k1 = fraction of ew used for material removal by melting k2 = fraction of ew used for material removal by vaporization comparative study of material removal rate of single-spark and multi-spark micro-edm of copper 55 lm = latent heat of melting (j/kg) lv = latent heat of vaporization (j/kg) ns = no of sparks per second r = resistance (ω) t = temperature (k) tb = boiling temperature (k) tc = capacitance charging time (s) tdc = capacitance discharging time (s) ti = initial temperature (k) tm = melting temperature (k) v = voltage (v) vc = voltage between capacitance terminals (v) vr = material removed by vaporization and melting (mm 3 ) vr = voltage drop over the resistance (v) ρ = density of the workpiece material (kg/mm3) τ = time constant circuit (s) 1 introduction micro-electro discharge machining (micro-edm), a noncontact material removal process, is a suitable technique for microstructuring of any material having a minimal electrical conductivity of 0.1 scm -1 . a series of electrical sparks or discharges occur rapidly in a short span of time between tool electrode and workpiece during micro-edm [1, 2]. the electrical energy is converted into thermal energy instantaneously in micro-edm and spark energy results in melting and vaporization of both the workpiece and tool materials [3-6]. about 90% of the molten material is removed by vaporization and the material beneath the surface gets less energy which is removed by melting [6]. in micro-edm, the material is removed precisely by low level of input energy [7]. therefore, an rc circuit is used in micro-edm for pulse creation due to its capability of producing very small energy with a significantly short pulse in nanosecond duration [7]. the main process characteristics of micro-edm are material removal rate (mrr), average surface roughness and tool wear ratio. during micro-edm, workpiece material is removed by thermal energy created due to the impingement of ion or electrons. thus, every spark removes specific amount of material. knowing the time and amount of material removed in a single spark, mrr is estimated as micro-edm process characteristics. however, mrr is greatly influenced by the discharge duration and peak current even the same materials of both the electrode and workpiece. longer discharge duration and a higher peak current result in a higher mrr and twr with poor surface finish. on the contrary, a longer discharge duration and lower peak current reduce mrr with better surface roughness and a lower twr [8, 9]. the mrr also depends upon the properties of the workpiece material, the tool material and dielectric fluid. the lower breakdown voltage causes an earlier occurrence of spark, which increases the mrr. since cu has a lower breakdown voltage than cuw, a higher mrr is obtained in micro-edm of al2o3 with a cu electrode [10]. a number of analytical study have been reported for the estimation of micro-edm characteristics [11] which are developed based on amount of material removed in a single spark considering the ideal situations. these models could not include some of the effects that play a vital role in real micro-edm process and it is recommended to consider the effect of multi-spark machining [12, 13]. in multi-spark micro-edm, charging and discharging do not always follow the ideal conditions of the circuit [14], and a lot of unwanted pulses such as arching and short circuit are produced [15] which in turn reduce the effective number of pulses per second. moreover, in rc pulse microedm, the discharges are not uniform and the current and voltage are not constant with time [11]. as a consequence, the performances would not be same as estimated by single spark erosion and should be modified for multi-spark machining conditions. this paper presents a simple analytical estimation of mrr as a function of machining parameters capacitance and voltage for single spark which is then compared with the multi-spark erosion of rc pulse micro-edm. 2 single spark micro-edm to make a comparison between single spark and multi-spark erosion rate, an equation of mrr hence developed considering the ideal conditions in rc pulse micro-edm. for single spark analysis the following assumptions are considered. 1. the workpiece and tool materials are homogeneous in nature. 2. the thermo-physical properties of the workpiece material remain constant during the machining process [3]. 3. a fraction of the total spark energy is absorbed into the workpiece by conduction and rest of the energy is dissipated to the surroundings by convection and radiation [6]. 4. the entire material is removed from the cavity after each discharge [16] and debris is not resolidified inside or around the cavity. 5. the capacitor has no initial voltage and it is charged from a constant voltage source. 6. ignition delay time is negligible compared to total charging and discharging time. ali et al. (2021). international journal of engineering materials and manufacture, 7(2), 54-60. 56 a diagram of a rc pulse micro-edm circuit with the voltages at different parts is shown in fig. 1. it has mainly two parts; the charging part is connected to a high resistor in series and the discharging part has no resistor or is connected to a very low resistor. the energy stored in the capacitor during the charging period is completely released through the gap. the energy discharged (e) in a single spark micro-edm is given by eqn. (1) where c is the capacitance and v is the voltage gap. 2 2 1 cve = (1) thus, charging and discharging time depends on the amount of capacitance and resistances connected to the circuit. to make a very quick discharge, generally the discharge circuit is kept resistance-free in the ideal condition. however, the discharging circuit exerts small resistance from dielectric fluid and the machine system. it is obvious that the smaller the time constant, the more rapidly the voltage gain or decrease that is, the faster the response and the quicker the dissipation of circuit energy [17]. figure 1. schematic diagram of a rc pulse micro-edm circuit showing the voltages in different parts of charging side 2.1 estimation of material removal per spark the single spark energy of a rc micro-edm circuit as expressed by eqn. (1) is not utilized completely for material removal of the workpiece. only a fraction of the spark energy causes melting and vaporization of the material and creates a micro-crater. the remaining energy supplied into the gap is lost to the surroundings. assuming k fraction of e is utilized to remove material by melting and vaporization, thus, the discharged energy used for material removal per spark, ew is given by: 2 2 1 k cve w = (2) the value of k depends upon the thermal properties of the workpiece material. it is observed that the material is removed by vaporization (during the discharge) and melting (during the charging) [6]. assuming, k1 fraction of ew is used to vaporize the material and k2 fraction of ew is used to melt the material only. thus, the volume of material removed per spark can be found using eqn. (3).       += mv r h k h kkcv v  21 2 2 (3) according to equation (3), the crater volume is the function of capacitance, voltage and volumetric heat of vaporization and melting. thus, material removal is controlled by both the electrical parameters and thermal properties of the work material in rc pulse micro-edm. the number of sparks can be found from the rc circuit charging and discharging period estimation. it is observed that each spark has three stages. in the first stage, the discharge circuit is kept off, the charges are stored in the capacitor from the electric source and the capacitor voltage rises to its full capacity from zero while its current decreases to zero. the first stage is called charging or pulse-off time. in the second stage, dielectric breakdown occurs under the electromagnetic field, the resistance between the tool electrode and the workpiece decreases to zero. the second stage is referred to as ignition delay time. in the third stage, when there is virtually no resistance between the tool electrode and the workpiece, spark occurs with high current. the capacitance voltage decreases to zero. this stage is called discharging or pulse-on time. in this study, ignition delay time is assumed negligible compared to the total charging and discharging time. therefore, the total time required for single spark in a rc pulse circuit is the summation of charging and discharging time of capacitor. total number of sparks per second (ns), is the reciprocal of total time required for single spark and it can be expressed by equation (4). )(5 1 55 11 2121 rrccrcrtt n dcc s + = + = + = (4)) comparative study of material removal rate of single-spark and multi-spark micro-edm of copper 57 the total number of sparks in unit time is the function of capacitance and resistances. therefore, ns can be increased or decreased by changing either the capacitance or resistances or both in a rc pulse micro-edm circuit. 2.2 mrr for single spark the material removal rate (mrr) is defined as the volume of material removed per unit time. it is calculated by multiplying the volume of material removed in a single spark by the number of sparks occurring in unit time assuming that each of the sparks removes same amount of materials. thus, the mrr is expressed by eqn. (5) as below.       += mv s h k h kkcv nmrr 21 2 2 (5) this is the expression of mrr for single spark erosion in rc pulse micro-edm which shows that the electrical parameters, number of sparks per unit time and thermal properties of the material directly controls the erosion rate. 3 mrr for multi-spark micro-edm effective spark generation depends on many conditions such as the electrical and physical properties of workpiece and tool electrode, flushing conditions, spark gap, depth of the machining [16, 19, 20]. due to the stochastic nature of micro-edm, it is difficult to estimate the number of effective sparks theoretically. therefore, micro-edm of copper is conducted to investigate the deviation of experimental mrr from the mrr of ideal conditions. experiments were accomplished by a multi-purpose miniature machine tool (dt-110, mikrotools inc., singapore) using the machining conditions as given in table 1. the doe was done based on two parameters capacitance and voltage of four levels as shown in table 2. twelve experiments based on selected parameters (table 2) were designed and conducted. micro-holes were drilled on copper workpiece with 1 mm diameter copper tool electrode using kerosene dielectric fluid. to investigate the material removal mechanism and crater geometry, a sem micrograph of the machined copper workpiece was captured as shown in fig. 2. copper micro-craters are observed to have a clear and identical geometric pattern because of the uniform removal of material by melting and vaporization. the micrograph also showed no cracks on the machined surface and micro-crater is spherical in shape. finally, actual volume of the removed material was found by measuring the depth and diameter of the drilled holes. then mrr was then calculated for each of the experiments. the twelve experiments and their corresponding mrr are listed in table 3. the theoretical mrr (eqn. 5) and experimental actual mrr are compared graphically as shown in fig. 3. it is observed from fig. 3 that the experimental mrr is about half of the theoretical mrr. eqn. (5) has been formulated considering the ideal situation based on a single spark erosion volume. in multi-spark machining, charging and discharging do not follow the estimated time constant and there are many missing sparks among the estimated number of theoretical sparks. as such the number of effective sparks is less than the theoretical number of sparks in micro-edm which reduces the mrr in multi-spark machining condition. therefore, the mrr as expressed by eqn. (5) is found to be valid for single spark machining only and it is not valid for multi-spark machining for real application in making molds and or other products. however, the single-spark mrr expression can be adjusted to use for multi-spark mrr purposes. as such based on experimental study as discussed above, eqn. (5) can be transformed for multi-spark mrr purposes by with a multiplying factor, η as expressed by eqn. (6). the value of the correction factor would be different for different materials and conditions which would be estimated empirically. in this experimental study of copper workpiece material, the value of the multiplying factor was found to be η = 0.5.       += mv sadj h k h kkcv nmrr 21 2 2  (6) table 1. micro-edm conditions for copper material [6] conditions values variable parameter capacitance, c (nf) 10, 1, 0.22, 0.1 voltage, v (v) 100, 90, 80 constant conditions specific heat, cp (j/kg 0 c) 390 melting temperature, tm ( 0 c) 1084 boiling temperature, tb ( 0 c) 2562 room temperature, t0 ( 0 c) 20 latent heat of melting, lm (j/kg) 207000 latent heat of vaporization, lv (j/kg) 4730000 density, ρ (kg/m3) 8960 rc circuit resistance, r1 (ω) 1000 ali et al. (2021). international journal of engineering materials and manufacture, 7(2), 54-60. 58 conditions values fraction of energy consumed for material removal, k (%) 4.35 fraction of energy consumed for material removal by melting, k1 0.11xk fraction of energy consumed for material removal by vaporization, k2 0.89xk dielectric fluid kerosene cylindrical copper rod tool electrode diameter (mm) 1 tool polarity -ve feed rate, f (µm/s) 0.2 speed, n (rpm) 300 table 2. experimental micro-edm parameters for mrr of copper workpiece parameter level i ii iii iv capacitance c (nf) 0.1 0.22 1 10 voltage v (v) 80 90 100 110 table 3. theoretical and experimental mrr in micro-edm c (nf) v (v) mrr (mm 3 /s) (eqn. 5) mrrex (mm 3 /s) mrr mrr ex 1 10 100 0.001586 0.000726 0.458 2 10 90 0.001285 0.000664 0.517 3 10 80 0.001015 0.000523 0.516 4 1.0 100 0.001586 0.000633 0.400 5 1.0 90 0.001285 0.000603 0.470 6 1.0 80 0.001015 0.000503 0.496 7 0.22 100 0.001586 0.000876 0.552 8 0.22 90 0.001285 0.000790 0.615 9 0.22 80 0.001015 0.000669 0.660 10 0.1 100 0.001586 0.000654 0.412 11 0.1 90 0.001285 0.000510 0.397 12 0.1 80 0.001015 0.000458 0.451 figure 2. sem micrograph of surface texture in micro-edm of copper showing a spherical micro-crater. spherical cavity created by single spark 10 µm 1. comparative study of material removal rate of single-spark and multi-spark micro-edm of copper 59 figure 3. comparison of theoretical and experimental mrr of micro-edm of copper 4 conclusions in this study, the mechanism of material removal and the mrr for single-spark and multi-spark micro-edm are compared. mrr due to single spark is formulated based on electro-thermal mechanism. then during real experimental machining number of sparks and total machining time are counted. the volume of material removal was measured and then converted into mrr. the experiments were repeated many times and a significant difference in mrr due to single-spark and multi-spark micro edm was observed. the specific findings of this study are as follows: 1. in ideal conditions, number of spark depends on capacitance and resistance. the number of effective sparks is found to be identical with theoretically calculated values at the initial machining stage. however, the frequency of effective discharges decreases with the progress of the machining due to inability of debris flushing. 2. in micro-edm of copper, it is observed that the experimental mrr in multi-spark is almost half of the theoretical mrr in single spark. this indicates that the mrr reduces by a higher percentage due to the creation of ineffective pulses in multi-spark erosion. therefore, a correction factor is needed to adjust in multi-spark erosion. 3. the mrr in multi-spark micro-edm is the function of effective sparks generated in the specified duration which depends on many factors such as the electrical and physical properties of materials, flushing conditions, spark gap, depth of the machining. as an experimental correction factor, it includes all these conditions in estimation of mrr. 4. in this experimental study it was found that the correction factor is to be 0.5 for coper workpiece and copper tool electrode (i.e.,  = 0.5 in equation 6) acknowledgements the authors would like to thank the ministry of higher education of malaysia (mohe) for financial support under research grant frgs 14-131-0372. references 1. hösel, t., müller, c., & reinecke, h.: ‘spark erosive structuring of electrically nonconductive zirconia with an assisting electrode’, cirp j. manuf. sci. technol., 2011, 4, (4), pp. 357-361 2. maity, k., & singh, r. k.: ‘an optimisation of micro-edm operation for fabrication of micro-hole’, int. j. adv. manuf. technol., 2012, 61, (9-12), pp. 1221-1229 3. wong, y., rahman, m., lim, h., han, h., & ravi, n.: ‘investigation of micro-edm material removal characteristics using single rc-pulse discharges’, j. mater. process. technol. 2003, 140, (1), pp. 303-307 4. yang, x., guo, j., chen, x., & kunieda, m.: ‘molecular dynamics simulation of the material removal mechanism in micro-edm’, precis. eng., 2011, 35, (1), pp. 51-57 5. yoo, b. h., min, b.-k., & lee, s. j.: ‘analysis of the machining characteristics of edm as functions of the mobilities of electrons and ions’, int. j. precis. eng. manuf., 2010, 11, (4), pp. 629-632 6. zahiruddin, m., & kunieda, m.: ‘comparison of energy and removal efficiencies between micro and macro edm’, cirp ann. manuf. technol., 2012, 61, (1), pp. 187-190 ali et al. (2021). international journal of engineering materials and manufacture, 7(2), 54-60. 60 7. shin, h. s., park, m. s., & chu, c. n.: ‘machining characteristics of micro edm in water using high frequency bipolar pulse’, int. j. precis. eng. manuf., 2011, 12, (2), 195-201 8. kunieda, m., lauwers, b., rajurkar, k. p., & schumacher, b. m.: ‘advancing edm through fundamental insight into the process’, cirp ann. manuf. technol., 2005, 54, (2), pp. 64-87 9. salonitis, k., stournaras, a., stavropoulos, p., & chryssolouris, g.: ‘thermal modeling of the material removal rate and surface roughness for die-sinking edm’, int. j. adv. manuf. technol., 2009, 40, (3-4), pp. 316-323 10. muttamara, a., fukuzawa, y., mohri, n., & tani, t.: ‘effect of electrode material on electrical discharge machining of alumina’, j. mater. process. technol., 2009, 209, (5), pp. 2545-2552 11. dhanik, s., & joshi, s. s.: ‘modeling of a single resistance capacitance pulse discharge in micro-electro discharge machining’, j. manuf. sci. eng., 2005, 127, (4), pp. 759-767 12. somashekhar, k., mathew, j., & ramachandran, n.: ‘electrothermal theory approach for numerical approximation of the μ-edm process’, int. j. adv. manuf. technol., 2012, 61(9-12), pp. 1241-1246 13. somashekhar, k., panda, s., mathew, j., & ramachandran, n.: ‘numerical simulation of micro-edm model with multi-spark’, int. j. adv. manuf. technol., 2015, 76, (1), pp. 83-90 14. izquierdo, b., sanchez, j., plaza, s., pombo, i., & ortega, n.: ‘a numerical model of the edm process considering the effect of multiple discharges’, int. j. mach. tools manuf., 2009, 49, (3), pp. 220-229 15. aligiri, e., yeo, s., & tan, p.: ‘a new tool wear compensation method based on real-time estimation of material removal volume in micro-edm’, j. mater. process. technol., 2010, 210, (15), pp. 2292-2303 16. krishna kiran, m. p. s., & joshi, s. s.: ‘modeling of surface roughness and the role of debris in micro-edm’, j. manuf. sci. eng., 2007, 129, (2), pp. 265-273 17. alexander, c. k., sadiku, m. n., & sadiku, m.: ‘fundamentals of electric circuits’ (mcgraw-hill higher education, 2007) 18. kildemo, m., calatroni, s., & taborelli, m.: ‘breakdown and field emission conditioning of cu, mo, and w’, phy. rev. special topics-accelerators and beams, 2004, 7, (9), pp. 092003 19. li, j., yin, g., wang, c., guo, x., & yu, z.: ‘prediction of aspect ratio of a micro hole drilled by edm’, j. mech. sci. technol, 2013, 27, (1), pp. 185-190 20. mahardika, m., & mitsui, k.: ‘a new method for monitoring micro-electric discharge machining processes’, int. j. mach tools manuf., 2008, 48, (3), pp. 446-458 international journal of engineering materials and manufacture (2022) 7(3) 78-88 https://doi.org/10.26776/ijemm.07.03.2022.02 mohammad zoynal abedin and a s m luthful karim department of mechanical engineering dhaka university of engineering & technology gazipur 1707, bangladesh e-mail: abedin.mzoynal@duet.ac.bd reference: abedin, m. z. and karim, a. s. m. l. (2022). waste to energy technologies for municipal solid waste management in bangladesh: a comprehensive review. international journal of engineering materials and manufacture, 7(3), 78-88 waste to energy technologies for municipal solid waste management in bangladesh: a comprehensive review mohammad zoynal abedin and a. s. m. luthful karim received: 14 june 2022 accepted: 14 july 2022 published: 20 july 2022 publisher: deer hill publications © 2022 the author(s) creative commons: cc by 4.0 abstract bangladesh has an impressive track record of development and has been among the fastest growing economies in the world over the past decade, supported by a demographic dividend, strong ready-made garment (rmg) exports, remittance, and stable macroeconomic conditions. with the growth of populace and the living standards, the goods and energy consumption in bangladesh are seen to be increased which rises the waste generation. thus, municipal waste management (msw) and energy supply are becoming the great challenges for bangladesh. waste to energy (wte) conversion technologies would be a very timely solution to an ever-growing problem. these technologies are environment-friendly and cost effective; however, these are not popular within the developing country bangladesh. this paper discusses current waste status, significant progresses and future prospect of solid waste management process as well as evaluates the best possible wte technology suitable for bangladesh. it is found that bangladesh produces approximately 13,332 tons of msw per day in which almost 26% and 12% of total wastes are generated by its capital city, dhaka and chattogram, respectively. the incineration process for electricity production is seen to be the most effective wte technology for chattogram city. for instance, for one ton of msw, the incineration process can provide 0.585 mwh electricity and 1.742 mwh heat with an emission factor of 0.28 ton of co2. with an average plant capacity cost of 2.1 usd which is lower than other wte technologies. therefore, the incineration can be utilized as the most effective wte technology for major cities in bangladesh. keywords: municipal solid waste, waste management, waste to energy, incineration, electricity, bangladesh. 1 introduction with the rapid progress of society, the demand of energy supply and waste management has increased rapidly. this trend will continue as people will strive to improve their living standards. waste management so far has consisted of human excrements and sewage waste. with rapid urbanization, it is now considered as municipal solid waste (msw), which includes other non-hazardous solid waste and other gaseous wastes consisting primarily of carbon dioxide, methane and others. nations those are in lack of natural resources of energies are seen to take necessary attempts to generate energy from alternative sources, particularly from waste and biomass [1]. bangladesh, the seventh most populated country in the world [2], is facing accelerated msw generation with the increase of population and the rapid change of people’s living standard [3]. the demand of domestic electricity in bangladesh is more than the supply. merely 42% of the population can access the electricity of national grid [4]. therefore, the wte conversion technologies could be used to lessen the overload of waste as well as to prevent the environment from pollution. the success of waste management is influenced by several factors like economic growth, urbanization, policy, governance, cultural and socioeconomic aspects, international influences, and institutional issues. various types of live feedstock have been managed by using several well-known wte technologies. for instances, pyrolysis is known for using plastics, gasification uses msw, and anaerobic digestion uses bio wastes such as food and paper [5]. among these, thermal processing of waste is an inviolable a part of each integrated wte waste management system [6]. though it has still very low contribution to countries’ energy generation, it may be increased by enhancing the performances of the plant [7]. generating sufficient electricity to meet the electricity demand and waste management are two of the most challenging factors in bangladesh. hence, various research has been conducted to manage both of them together. this paper discusses the initiatives taken in bangladesh to meet these challenges in a way to propose a suitable wte mailto:abedin.mzoynal@duet.ac.bd abedin and karim (2022): international journal of engineering materials and manufacture, 7(3), 78-88 79 technology. in these circumstances, the waste management system including present condition of waste management system and adverse effects of improper waste management system in bangladesh is discussed in the following section. 2 waste management in bangladesh waste management can be described as the national control of various aspects of its life cycle such as waste collection, various techniques of disposal and assessment of the compositions. effective waste management system plays a major role in controlling the adverse impact of wastes on the environment as well as human health within a country. the projected rate of growth of urban population in bangladesh from 2010 to 2015 was almost 3% [8]. with the population growth, problems of waste management are also increasing in the major cities of bangladesh. dhaka, a rapidly developing metropolitan city, has a major concern regarding msw management [9]. at present, there is hardly any technological advancement in terms of waste management that has been introduced so far in bangladesh. 2.1 present condition of waste management there are total 514 urban areas in bangladesh, these include 11 city corporation, 298 pouroshavas and rest are urban centres [10]. most of these cases, people have very limited access to the proper waste management/disposal services that ultimately leads to increase the problems of waste mismanagement effectively. in addition, total rate of waste collection in major cities of bangladesh like dhaka is only 37%. the majorities of wastes are not collected properly and are unauthorized disposed of, which has the risks of creating serious hazard to the environmental, as well as human health [11]. 2.2 adverse effect of improper management of waste one of the most detrimental effects of improper management of waste particularly msw is that the irruption of diseases such as epidemic of malaria, respiratory diseases, and other water-borne illnesses due to ground water contamination. there are also bio-medical wastes which create grave danger. approximately 20% of the biomedical wastes are highly contagious and hazardous virtually, because these are commonly disposed of into the drains and sewage system [12]. this poor sanitation has some serious concerns for the health of the citizens and is directly responsible for most of the child mortality. besides, msw clogs up the drainage system resulting flooding in the streets. moreover, among the negative effects mosquitoes and bad odour are resulted. in many countries including bangladesh, landfills cause emission of methane which is an agent for climate change. the sanitary landfill at matuail near jatrabari, dhaka releases the methane which is almost equivalent to those released from 190,000 cars [12]. 3 waste to energy technologies to attain the sustainable solid waste management, few options are considered round the world, like thermal treatment, biological treatment, landfilling with energy recovery, and recycling. among them, thermal treatment, biological treatment and landfilling with energy recovery are supported the theme of energy recovery option of msw management hierarchy [13]. the following sections describe the popular wte technologies for msw management. 3.1 incineration incineration is one of the most effective wte technologies employed for conversion of industrial, household and agriculture wastes into energy. wastes are directly burned at high temperatures (800°c) in incineration process. heat from combustion may be used as energy source of steam generation as well as electricity [13]. to mitigate the scarcity of power supply for the city demands and to reduce spaces for new landfills, incineration process can play significant role to produce renewable energy from discarded msw [14]. figure 1 shows a classic incineration wte technology [15]. first, waste is directly burned in the combustion chamber at an adequate temperature (900-950°c) using flue gas and pre-heated air. after the waste incineration process, superheated steam is produced and then it is used within a cogeneration system to produce energy and heat. the electric energy is produced by a turbine connected to a generator and the heat by a district heating system. 3.2 bio-methanation in bio-methanation or anaerobic digestion (ad) procedure, organic components of the solid wastes are segregated and put into a closed container where the wastes are decomposed naturally in the presence of methanogen bacteria and eventually generate biogas (methane rich). the biogas produced by bio-methanation may be used to generate power or electricity [14]. in bio refineries, solid wastes are converted into liquid and gaseous biofuels. these biofuels may be used to generate power in thermal plants, heat in various regional heating systems [15]. figure 2 shows a facility of combined heat and power bio-refinery to treat msw [15]. in this facilities, organic fraction can be converted into biogas while inorganic fraction can be converted into solid recovered fuel (srf) to produce syngas. an integrated gasification system with a fuels synthesis facility can convert syngas to bio-diesel, bio-jet fuel, bio-methanol or bioethanol [15]. waste to energy technologies for municipal solid waste management in bangladesh: a comprehensive review 80 3.3 pyrolysis in the pyrolysis process, organic matters of waste are decomposed by high temperature to become a gas comprising of molecules jointly stated as synthesis gas or syngas. the syngas produced is further combusted in several combustion engine generator sets or turbines that generate electricity. syngas may also be used as source of energy or by product for household use likewise as industrial use [13]. figure 3 shows a typical pyrolysis process of biomass waste to produce energy [15]. figure 1: incineration plant to produce electricity and heat from msw [15]. figure 2: combined heat and power bio-refinery to treat msw [15]. figure 3: representation of a pyrolysis process [15]. abedin and karim (2022): international journal of engineering materials and manufacture, 7(3), 78-88 81 3.4 landfill gas (lfg) collection landfill gas collection processes are of two types: active and passive process [16]. lfg is a natural by-product of the decomposition of organic matters of solid wastes in landfills. landfill gas recovery process can generate 20% to 30% methane. by adopting active gas collection process, significant amount of electrical energy can be generated from solid waste which could meet the electricity scarcity of the country [16]. figure 4 shows a typical flow diagram of electricity generation from landfill biogas [15]. 3.5 plasma arc plasma arc process is considered to be one of the updated technologies for disposing of solid wastes, particularly hazardous wastes and radioactive wastes [15]. in the process, wastes collected from various municipalities are processed through the employment of high-energy plasma torches. hence, many successful experiments have been carried out involving the gasification of msw, fossil fuels, auto shredder residue, industrial wastes in a plasma reactor to produce primarily carbon monoxide and hydrogen. in addition, the inorganic components of the feed are converted to molten and organic wastes which are utilized for the production of power through the combustion/turbine combined cycle at much higher efficiencies [17]. figure 5 shows an artistic drawing of the plasma waste processing plant [17]. 4 waste management and waste to energy status emphasis on waste management and subsequently wte technologies have been developing over the years worldwide. as a highly populous developing country, the implementation of wte technologies in bangladesh will not only help managing the wastes generated but also be able to generate electricity. present waste management systems and wte status of bangladesh particularly of its major cities such as dhaka, chattogram, rajshashi, jessore, rangpur, gazipur, barisal, mymensingh and sylhet are discussed in the subsequent paragraphs. 4.1 dhaka city islam [18] investigated six different scenarios consisting of incineration process and lfg recovery system in dhaka city shown in table 1. energy potential of various wte strategies is assessed using standard energy conversion model and subsequent ghgs emission models. the study tries to seek out the absolute best scenario considering highest economic, energy potential, net ghgs emission and proposes mixed msw incineration process that would be an effective wte strategy for generation of electricity in dhaka city. according to the table 1, it is seen that dhaka city generates wastes approximately 3,550 tons per day and the majority of the generated waste is organic which is 68.30% while other wastes belong to combined as 31.7%. 4.2 chattogram city islam et al. [19] investigated the various wte processes in chattogram city with a view to identify the most suitable process for the city. this study emphasizes on solid waste management of chattogram city and its best application by considering energy production, cost aspect and impact on the environment. according to their research, the daily requirement of electricity is approximately 1000 mw but the power grid can provide electricity up to 700-750 mw which causes an energy deficit of approximately 250 mw. table 2 shows the composition of the generated wastes in chattogram city. the city generates wastes approximately 1550 tons per day. the traditional waste management method known as landfilling causes a negative cost impact up to 76140 usd/day which is also responsible for generating 1000 ton co2/day. to overcome this situation, the study suggests that incineration waste management method would be most suitable for the city [19]. figure 4: flow diagram of electricity generation from landfill biogas [15]. waste to energy technologies for municipal solid waste management in bangladesh: a comprehensive review 82 figure 5: plasma waste processing plant [17]. table 1: waste generation in dhaka city [18] waste type amount (tons/day) amount (%) organic 2,424.65 68.30 plastic 152.65 4.30 paper 379.85 10.70 wood 78.10 2.20 glass 24.85 0.70 metals 71.00 2.00 rubber 49.70 1.40 other 369.20 10.40 total 3,550.00 100.00 table 2: waste composition of chattogram city [19] waste type amount (tons/day) amount (%) organic 1054.00 68.00 plastic 62.00 4.00 paper 170.50 11.00 wood 31.00 2.00 glass 15.50 1.00 metals 31.00 2.00 rubber 31.00 2.00 other 155.00 10.00 total 1550.00 100.00 the parameters considered to compare between the various wte technologies in respect of chattogram city are demonstrated in table 3. it can be seen that by incineration process, generation of electricity is most suitable for chattogram city. in the analysis, for one ton of msw, the incineration process provides an electricity of 0.585 mwh and heat of 1.742 mwh with an emission factor of 0.28 ton of co2. the average plant capacity cost of incineration is 2.1074 usd for one ton of msw which is quite lower than those of other wte technologies [19]. abedin and karim (2022): international journal of engineering materials and manufacture, 7(3), 78-88 83 table 3: parameters considered for various wte technologies in chattogram city [19] parameter method landfilling incineration gasification anaerobic digestion pyrolysis case study information waste feed (ton/day) 958 958 958 958 958 costs average plant capacity cost (usd/ton waste) 14 2.1074 2.522 6.088 8.595 operation and maintenance cost (usd/ton waste) 10 95 115 80 115 msw conversion factor electricity production (mwh/ton msw) 0.585 0.60 0.25 0.66 heat production (mwh/ton msw) 1.742 0.2976 emission factor co2 emission from processing (ton co2/ ton msw) 0.791 0.28 0.2 0.253 1.7 4.3 rajshahi city halder et al. [20] investigated the existing wte practice in rajshahi city. according to their study, the people living in rajshahi city generate wastes approximately 400 tons/day. the generated wastes are from various sources such as residential, institutional, industrial, medical, construction, agricultural and municipal. the study proposed a new waste management system for rajshahi city which is shown in figure 6. furthermore, in waste generation there is a seasonal fluctuation and the average msw generation per capita is 0.40 kg/person/day. high moisture content and low calorific value also characterizes solid waste, which helps to work out the acceptable waste management option. supported these characteristics, an improved waste management system for rajshahi city has been proposed by the study. depending on the characteristics of solid wastes generated in rajshahi city, approximately 4,482 mw/day of electricity has been generated. based on the present solid wastes generation in rajshahi city, the study proposed to install a power plant of 5-10 mw to produce electricity as well as to reduce adverse effect of solid waste on environment [20]. according to table 4, the daily generation of waste in jessore city is 21.49 ton/day and that leads to yearly waste generation of 7,846.50 tons. figure 6: proposed waste management system for rajshahi city [20]. 4.4 jessore city karim et al. [21] investigated the household waste management in a particular area of jessore city where the generated household wastes are characterized significantly in a way to store in a dumping area. according to the study, wastes are not properly managed in that particular area and people are also least concerned. during the survey, various types of household wastes were found such as biodegradable, non-biodegradable, recycling and reusable wastes [21]. table 4 shows the generation of total waste in jessore city. waste to energy technologies for municipal solid waste management in bangladesh: a comprehensive review 84 4.5 rangpur city sarkar et al. [22] investigated the waste disposal process of rangpur city. the study intends to explain present waste management process and present state of the waste dumping points within the specific wards of rangpur city. the prime data has been collected directly from field survey along with gps survey to monitor and assess the dumping points of wastes. the wastes in rangpur city are collected from four key sources: industry, residence, organization, and open street. usually, a major portion of generated wastes are dumped on the street side which is later collected and disposed at the primary dumping points by the local cleaners. from the primary dumping points, the wastes are then collected by rangpur city corporation (rpcc) authority and are either dumped at central dumping point or at land filling sites. according to the study, approximately 236 waste collection points are available all around the city. on an average 16.46 tons of wastes are generated per day by 15 wards of rangpur city. wastes generated in each wards varies with the number of waste collecting points available at the respective ward which is shown as table 5 [22]. based on the table 5, for better waste management of rangpur city, sarkar et al. [22] suggest that geographic information system (gis) may also be used as an effective tool. 4.6 gazipur city shishir et al. [23] investigated about waste management of gazipur city based on 3r (reduce, reuse and recycle) waste management policy. the goal of their research is to assess the waste generation in gazipur city by collecting information from the household waste composition, secondary and final dumping sites in order to find out the amount of wastes that can be reduced, which will ultimately show the probable economic benefits, through the adoption of 3r policy. during the research, whole gazipur city was divided into five zones. 10 household surveys were conducted in each zone and at the final dumping zone. according to mohiuddin et al. [24], recyclable waste contents in gazipur city are seen to be varied during the dry and wet seasons. the recyclable waste contents, as shown in table 6, waste generation varies greatly by seasons which affects the waste generated per day. table 4: generation of waste in jessore city [21] component average waste (g/day) total household total waste (kg/day) total waste (ton/year) vegetable 436 42,793 18,692.21 6,822.66 paper 8.0 358.69 130.92 plastic 6.0 254.93 93.05 grass & wood 21 927.22 338.44 metal 3.5 152.45 55.64 clothes 3.1 136.63 49.87 glass 7.3 315.25 115.07 others 15 659.87 240.85 total wastes 21,497.20 7,846.50 table 5: ward-wise daily waste generation in rangpur city [22] ward waste collecting points (numbers) waste generation approx. (tons/day) 16 12 0.87 17 07 0.80 18 11 0.98 19 30 2.0 20 22 1.5 21 21 1.3 22 19 1.24 23 16 1.12 24 22 1.50 25 15 1.00 26 14 0.98 27 15 0.99 28 12 0.82 29 08 0.50 30 12 0.86 total: 15 236 6.46 abedin and karim (2022): international journal of engineering materials and manufacture, 7(3), 78-88 85 4.7 mymensingh city rahman et al. [25] conducted investigation on mymensingh city to identify the waste generation, waste disposal and management system in order to assess the impacts of these wastes. through a pre-tested questionnaire from 50 industries and a recycling plant divided in categories, relevant data were collected. according to the study, total generation of waste is approximately 9.758 ton/day of which 27.42% from mustard oil industries, 34.52% from puffed rice mills, 8.89% from coconut oil mills and 13.04% from all other industries. industries of small, medium and large category produce 1.223 ton/day, 3.115 ton/day and 5.420 ton/day, respectively. table 7 shows the waste generation of the three categories of industries. table 7 shows that a total of 9.8 tons of wastes are generated every day and more than 50% of these wastes are generated by large category of industry. 4.8 barisal city islam et al. [26] conducted investigation in barisal city to determine the present waste generation rate through identifying the dumping sites and evaluating the environmental effects of solid wastes. the methodologies followed for their study are field observation, collection of information and data from barisal city corporation (bcc), photography and interviews from city dwellers. various sources of waste generation found in barisal city as residential (79.6%), industrial (1.2%), commercial (15.5%), open street (1.5%) and health care facilities (3.8%). total generation of solid wastes in barisal city is approximately 134 tons/day which are indiscriminately dumped in several 3 (three) sites [26]. table 8 demonstrates the waste composition of barisal city. from table 8, it is seen that a total of 134 tons of wastes are generated every day in barisal city and almost 65% of these wastes are of food type. 4.9 sylhet city iqbal et al. [27] investigated the msw of sylhet city by highlighting the status of various kinds of generated wastes along with the negative impacts of poor waste management. total waste generation per day and composition of waste in sylhet city is shown in table 9 and table 10, respectively. table 9 and table 10 show that 67% of total 200-250 tons of waste generated each day are organic waste. table 6: recyclable waste composition of gazipur city [24] cycle average waste generation rate (kg/capita/day) average total waste generation (ton/day) average recyclable waste (%) household secondary dumping site final dumping site dry season 0.2774 693.5 38.16 32.066 47.46 wet season 0.3786 946.5 41.0 27.5 37.479 table 7: waste generation of three categories of industries in mymensingh city [25] category of industry total waste generated (ton/day) percentage (%) small 1.223 12.49 medium 3.115 31.80 large 5.420 55.34 total 9.793 100.00 table 8: waste composition of barisal city [26] types of waste amount (ton/day) percentage (%) food 87.1 65 paper 8.16 6 clothes 4.02 3 polythene 10.72 8 plastic 9.38 7 metals 4.02 3 wood 4.02 3 glass 6.7 5 total 134 100 waste to energy technologies for municipal solid waste management in bangladesh: a comprehensive review 86 table 9: waste generation per day in sylhet city [27] waste types amount (tons/day) clinical waste 5-6 restaurant waste 100-120 household waste 130-150 total 200-250 table 10: waste composition of sylhet city [27] waste types % organic 67 polythene 13 metal 2 plastic 18 5 summary based on the above-mentioned review, the msw management approaches followed by the major cities of bangladesh such as dhaka, chattogram, gazipur, rajshahi, sylhet, barisal, jessore, rangpur and mymensingh have been reviewed according to the recent literatures. it is found that among other technologies, incineration is the most effective wte technology for chattogram city. various research has also been carried out on other major cities to assess the wastes that are being generated but research on wte for those cities yet to be carried out. figure 7 demonstrates the total waste generation in the major cities of bangladesh. figure 7 shows that maximum amount of waste is being generated in dhaka city and chattogram city. dhaka generates around approximately 3,550 tons of waste per day and is followed by chattogram is generating approximately 1550 tons of waste per day. gazipur, rajshahi, sylhet, barisal, jessore, rangpur and mymensingh generate approximately 946, 400, 250, 134, 21.5, 16.5 and 9.8 tons of waste per day respectively. figure7: waste generation in major cities of bangladesh. 6 conclusions the analysis of solid waste management (msw) for the energy production by using waste to energy technologies (wte) has been reviewed for bangladesh perspective in this paper. it is seen that the generation of msw and consumption of energy are increasing continuously with the rapid urbanization and population growth. however, the implementation of sustainable msw management is turning into a great challenge around the globe in terms of environment and human health protection. wte is a never-ending source of energy and more research in this field needs to be carried out on various areas of the country for waste management as well as energy generation. moreover, it is seen by reviewing the relevant literature that among the wte technologies, the incineration process can be predominantly used in the production of energy in bangladesh. the key findings from the present analysis may be summarized as follows: 0 500 1000 1500 2000 2500 3000 3500 4000 w a s t e g e n e r a t i o n , t o n s / d a y abedin and karim (2022): international journal of engineering materials and manufacture, 7(3), 78-88 87 1) bangladesh produces approximately 13,332 tons of waste per day. major cities such as dhaka, chattogram, gazipur, rajshahi, sylhet, barisal, jessore, rangpur and mymensingh generate approximately 3550, 1550, 946, 400, 250, 134, 21.5, 16.5 and 9.8 tons of waste per day respectively. 2) more than 26% of waste is generated in dhaka city which is also the most populated city of bangladesh. on the other hand, chattogram city is seen to be followed secondly by producing almost 12% of total wastes. 3) the incineration process for the generation of electricity is the most effective wte technologies for chattogram city. for instance, for one ton of msw, the incineration process provides an electricity of 0.585 mwh and heat of 1.742 mwh with an emission factor of 0.28 ton of co2. the average plant capacity cost of incineration is 2.1074 usd for one ton of msw which is quite lower than those of other wte technologies. therefore, the incineration can be utilized as the most effective wte technology for bangladesh. references [1] klinghoffer, n. b., castaldi, m. j. (2013). waste to energy conversion technology. oxford uk, woodhead publishing limited. [2] farid, k. s., ahmed, j. u., sarma, p. k., begum, s. (2011). population dynamics in bangladesh: data sources, current facts and past trends. j. of bangladesh agriculture university 9(1), 121-30. [3] minghua, z., xiumin, f., rovetta, a., qichang, h., vicentini, f., bingkai, l., giusti, a., yi, l. (2009). municipal solid waste management in pudong new area, china. waste management, 29(3), 1227-33. [4] rahman, s. m. s., azeem, a., ahammed, f. (2017). selection of an appropriate waste-to-energy conversion technology for dhaka city, bangladesh. international journal of sustainable engineering, 10(2), 99-104. [5] porteous, a. (2005). why energy from waste incineration is an essential component of environmentally responsible waste management. waste management, 25(4), 451-9. [6] ahmed, s. i., fatta, a. a., hossain, m. j., tanvir, m. s. (2018). potential of waste to energy (wte) technologies for efficient management of municipal solid waste in bangladesh. international conference on energy & environment, 28-29 september, 2018, shahjalal university of science and technology, sylhet, bangladesh. [7] lombardi, l., carnevale, e., corti, a. (2015). a review of technologies and performances of thermal treatment systems for energy recovery from waste. waste management, 37, 26-44. [8] http://data.un.org/en/iso/bd.html. [accessed on 15 june 2021] [9] bhuiya, g. m. j. a. (2007). solid-waste management: issues and challenges in asia, edited by the environmental management centre, mumbai, india. published by the asian productivity organization 1-2-10 hirakawacho, chiyoda-ku, tokyo 102-0093, japan. [10] das, s. r., hossain, m. l., talukder, s., hossain, m. k. (2015). solid waste management in commercial city of bangladesh, journal of environmental treatment techniques, 3(1), 60-70. [11] alamgir, m., ahsan, a. (2007). municipal solid waste and recovery potential: bangladesh perspective, iran. j. environ. health. sci. and eng., 4(2), 67-76. [12] clark, a. leaking landfill contributes to world’s mystery methane hotspot. bloomberg, 25 april 2021; available from: https://www.bloomberg.com/news/articles/2021-04-25/leaking-landfill-contributes-toworld-s-mystery-methane-hotspot. [accessed on 17 june 2021] [13] cheng, h., hu, y. (2010). municipal solid waste (msw) as a renewable source of energy: current and future practices in china, bioresource technology, 101(11), 3816-24. [14] hossain, h. m. z., hossain q. h., uddin, m. m., ahmed, m.t. (2014). municipal solid waste (msw) as a source of renewable energy in bangladesh: revisited. renewable and sustainable energy reviews, 39(5), 35-41. [15] moya, d., aldás, c., lópez, g., kaparaju, p. (2017). municipal solid waste as a valuable renewable energy resource: a worldwide opportunity of energy recovery by using waste-to-energy technologies. energy procedia, 134(2), 286-95. [16] uddin, m.m., mojumder, m.s.s. (2011). biogas production from municipal waste: prospect in bangladesh, cyber journals: multidisciplinary journals in science and technology, journal of selected areas in renewable and sustainable energy (jrse), october edition, 1-5. [17] leal-quirós, e. (2004). plasma processing of municipal solid waste. braz. j. phys., 34(4b), 1587-1593. [18] islam, k. m. n. (2016). municipal solid waste to energy generation in bangladesh: possible scenarios to generate renewable electricity in dhaka and chittagong city. journal of renewable energy, 4, 1-16. [19] islam, m. r., rafi j. a., hossain, m. s. (2019). a comparative study on waste-to-energy (wte) technologies for municipal solid waste (msw) management in chittagong, bangladesh, 1st international conference on advances in science, engineering and robotics technology (icasert), 3-5 may 2019, bangladesh, 1-6. [20] halder, p. k., paul, n., hoque, m. e., hoque, a. s. m., parvez, m. s., rahman, m. h., ali, m. (2014). municipal solid waste and its management in rajshahi city, bangladesh: a source of energy, international journal of renewable energy research, 4(1), 168-175. [21] karim, r., nawshin, n. (2014). characteristics of household solid waste and its management options in the urban areas, jessore, bangladesh, international journal of science and research (ijsr), 3(9), 1519-1524. http://data.un.org/en/iso/bd.html https://www.bloomberg.com/news/articles/2021-04-25/leaking-landfill-contributes-to-world-s-mystery-methane-hotspot https://www.bloomberg.com/news/articles/2021-04-25/leaking-landfill-contributes-to-world-s-mystery-methane-hotspot waste to energy technologies for municipal solid waste management in bangladesh: a comprehensive review 88 [22] sarker, m. f., rahman, m. z. (2018). assessment of solid waste management process in rangpur city corporation area, journal of geography, environment and earth science international, 16(3), 1-10. [23] anik, m. a. h., shishir, a. r., islam, p., naila, s. n., chowdhury, i. m. (2018). sustainable solid waste management through 3r strategy in gazipur city, international journal of environment and waste management (ijewm), 22(1-4), 228-238. [24] mohiuddin, m., hossain, s. i., hridoy, f. n. (2015). study on municipal solid waste characterisation and management in gazipur city corporation, b.sc. engineering thesis, department of civil and environmental engineering, islamic university of technology, gazipur, bangladesh. [25] rahman, m. s., datta, s., islam, s. (2015). waste generation and management practices in bscic mymensingh. j. environ. sci. & natural resources, 7(1), 47-51. [26] islam, m. s., islam, m. h. (2015). assessing the environmental effects of solid waste in barishal city of bangladesh, 4th international conference on solid waste management in the developing countries, khulna university of engineering & technology (kuet), bangladesh, 15-17 february 2015, 2(1), 1-10. [27] iqbal, s. a., tasnim, f., chowdhury, a. r., islam, m. a., islam, m. t. (2015). municipal solid waste management in sylhet city corporation, 4th international conference on solid waste management in the developing countries, khulna university of engineering & technology (kuet), bangladesh, 8-10 february 2015. international journal of engineering materials and manufacture (2021) 6(3) 124-131 https://doi.org/10.26776/ijemm.06.03.2021.03 g. barragan 1,2 , f. e. mariani2, and r. t. coelho2 1 grupo de investigación en ingeniería aeroespacial, universidad pontificia bolivariana, circular 1 # 70-01, medellín, colombia. 2 lapras, sao carlos engineering school, university of sao paulo, av. trabalhador são carlense 400, são carlos, brazil. e-mail: german.barragan@upb.edu.co reference: barragan et al. (2021). ti6al4v thin walls production using laser directed energy deposition (l-ded) process. international journal of engineering materials and manufacture, 6(3), 124-132. ti6al4v thin walls production using laser directed energy deposition (lded) process barragan, g. a., mariani, f. e. and coelho, r. t. received: 26 february 2021 accepted: 29 april 2021 published: 15 july 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract one of the main applications of directed energy deposition (ded) is the production of thin-wall structures, where it has significant advantages over traditional milling and machining techniques, or even welded analogues. these kinds of structures are frequently employed in aerospace components, field where titanium alloys have a primary role to play. amongst them, the most employed is the ti6al4v with an alpha + beta alloy containing 6% aluminium (al) and 4% vanadium (v). it has an excellent combination of strength and toughness along with excellent corrosion resistance. for the study hereby, thin-wall structures were constructed employing a laser directed energy deposition machine (l-ded), working with powder material. analyse identified some microstructural and mechanical characteristics, thorough metallographic study, wear test (micro-adhesive) and micro hardness test. finding a grain refined structure with competitive mechanical properties compared to materials manufactured by traditional processes. results positioning ded as an attractive manufacturing technology, with a huge potential to improve costs and material usage, besides almost no restriction on component shape. keywords: directed energy deposition, titanium, hardness, wear test, mechanical properties. 1 introduction the laser directed energy deposition (l-ded) process allows the fabrication of components that can be used in a variety of engineering applications using a layer-by-layer strategy for constructing directly from a cad data [1]. it employs a focused laser beam as heating source to melt in-situ delivered powder. when this occurs, a melt pool is formed on the surface of the substrate, or on a previously deposited layer. therefore, a track is created after solidification and the process is repeated according to the planned path until completing the construction of the desired part. ded is a complicated process with many interconnected variables [2]. however, some of the advantages to justify its use are related to improved mechanical behaviour resulted in the manufactured components and its capacity to fabricate complex geometrical elements overcoming the restrictions imposed by the traditional manufacturing processes [3]. thin wall structures comprise an important and growing proportion of engineering construction with some applications on aircraft, automobiles, turbomachinery, bridges, and machine elements where important benefits in terms of weigh reduction could be achieved [4]. when fabrication by traditional manufacturing methods shows problematical, ded has been seen a promising, advantageous and a competitive approach [5] and has being extensively explored [6-8]. the ti6al4 v is one of the most used alloys [9] with application at the same fields above mentioned, especially in thin-walled structures [10] due to its good mechanical properties even at high temperatures. it is also light in weight and corrosion resistant. considering the laser additive manufacturing (am) process the relationships between the deposition parameters, microstructure, and mechanical properties of that alloy have been studied [11] primarily with the use of unit tracks deposition onto a massive substrate [12] or the fabrication of simple geometric solid bodies. it was found improved behaviour when compared with their wrought counterparts [13] primarily due to fact that the deposited material undergoes rapid cooling enabling some grain refinements. for these study thin wall structures were constructed employed a laser directed energy (l-ded) deposition machine, working with powder material, to identify its microstructural and some mechanical behaviour, thorough ti6al4v thin walls production using laser directed energy deposition (l-ded) process 125 metallographic study, wear test (micro-adhesive) and micro hardness test introducing one step further towards industrial applications. 2 materials, methods and samples analysis 2.1 materials and equipment for the thin wall fabrication, a plate of ti6al4v (substrate) and ti6al4v grade 5 powder supplied by ge, as the additive manufacturing feedstock were employed. the chemical composition of the powder is in accordance with astm f2924 – 14 [14] and is presented in table 1. the fabrication was conducted in magic 250 machine, this 5 axis ded system equipped with a nd:yag laser with a maximum nominal power of one (1) kilowatt [15]. the powder size is between 45-150 µm, with a flow rate of 25s measured in accordance with the astm b213 standard. figure 1 (a) presents an sem image of the powder morphology, where is possible to observe its high sphericity and low satellite formation; in figure 1(b) a metallographic image of the powder is shown, where it is possible to observe that no internal porosities was found in the selected samples. therefore, the powder is considered with a good quality to be used in the l-ded process. table 1: chemical composition w% ti6al4v powder [16]. ti al v fe o c n h 87.6 91 5.5 6.75 3.5 -4.5 ≤ 0.40 ≤ 0.20 ≤ 0.08 ≤ 0.05 ≤ 0.015 figure 1: ti6al4v powder (a) morphology; (b) metallographic image [16]. 2.2 methods for the fabrication of the thin wall structures the process parameters listed in table 2 were employed. these parameters were selected in accordance with the machine, the material employed and previous tests to prove the consistence with an expected bead geometry. as the structure grows higher, some changes, or non-conformities, on the bead topography and geometry usually appear due to heat distribution and catchment efficiency. after selecting the above parameters for one bead deposition, the powder flow rate for wall construction was explored. six different thin wall structures were fabricated employing different powder flow rate as listed in table 3. the geometry, topography and microhardness of the wall were analysed. the condition which shows the better characteristics and more homogenous shape was selected and employed for the other conducted analysis (metallographic and wear test). barragan et al. (2021): international journal of engineering materials and manufacture, 6(3), 124-131. 126 table 2: employed process parameters. process parameters laser power 300 [w] feed speed 2000 [mm/min] standoff distance 3.5 [mm] atmosphere inner condition argon (ar) table 3: powder flow rates tested. condition powder flow rate [g/min] a 4,75 b 4,5 c 4,25 d 4 e 3,75 f 3,5 2.3 sample analysis microstructures of the deposited ti6al4v walls were characterized using the standard metallographic procedure, which involved abrasive cutting, hand sand, polishing, and etching. kroll's reagent (92 ml of distilled water, 6 ml of hno3, and 2 ml of hf) was used as the etching reagent. the cross-sections of the samples were analysed using a 3d laser confocal microscope lext 4100 by olympus. vickers microhardness tests on the specimens were carried out using model 1600 6300 hardness tester by buehler, under astm international standard test method e384. indentations were performed on the cross-section of the substrate and deposited walls. the tests used 3.0 n load and a dwell time of 15 s to obtain the microhardness profiles. micro-adhesive wear tests were performed deposited walls of ti6al4v. the tested surfaces were ground, and polishing. the “calotest” test was then performed using a quenched and tempered aisi 52100 steel ball, with 60 hrc hardness and diameter of 25.4 mm, driven by the driving shaft, sliding against the sample, with 1.7 n load. the sphere rotation speed was 275 rpm. the test times were 5, 10, 15, 20, 30 and 40 min for each condition studied, resulting in sliding distances of 110, 220, 330, 440, 600 and 880 m, respectively. the volume of material removed (v) was calculated according to equation 1: v = πd4/64r; for d << r (eq. 1) where d represents the diameter of worn caps, measured by optical microscope and r represents the radius of the sphere [17]. the wear tests were carried out at 29 ºc and a relative humidity of 49%, under dry sliding friction (in air and without lubrication), to prevent any interfacial element from causing influences on the effect of microstructural features. 3 results and discussion figure 2 shows different walls fabricated, where it is possible to see some topography defects on many of them caused for incorrect selections of the powder flow rate. figure 3 shows the vickers microhardness profiles obtained for the deposited walls. these tests were conducted for all the specimens to identify the influence of powder flow rate on the wall shape. for all walls, it appears that hardness remains constant from the top until the interface with the substrate. values were all close to 400 hv3.0, except condition (a), table 3, which went slightly higher, close to 450 hv3.0. at the interface with substrate, at the dilution region and heat affected zone (haz), the hardness declines abruptly, remaining in the substrate with values close to 330 hv3.0. the average hardness values of the layers were similar, regardless of the deposition parameters. ti6al4v thin walls production using laser directed energy deposition (l-ded) process 127 figure 2: fabricated walls figure 3: vickers microhardness profiles. conditions according to table 3. etching: kroll’s reagent. barragan et al. (2021): international journal of engineering materials and manufacture, 6(3), 124-131. 128 figure 4 shows the image of the wall (f) in table 3, which presents the best resulted shape and was selected to conduct the metallographic and wear test. figure 5 shows the optical micrograph of the ti6al4v substrate, with an average hardness of 330 ± 2 hv3.0. it can be noticed the presence of hexagonal close packed α-phase and bodycentred cubic β-phase structures [18,19]. figure 6 shows the optical micrograph of the longitudinal section of the selected wall (f). the deposition pattern is verified layer by layer, indicated by the deposition trajectory (blue arrows). the distance between boundaries of layers is 200 µm, consistent with the parameters used for deposition. microstructure of columnar dendrites was observed, which grew epitaxially from the substrate (direction z), with growth direction opposite to the direction of heat flow. during ded deposition, the substrate and/or the deposited layer act as heat sinks, which allows the growth of the grains to be against the direction of the heat flow [20]. figure 7 shows the micro-adhesive wear graphs obtained for the ti6al4v substrate of the selected wall (f). compared to the substrate, the wear resistance of the deposited selected wall, condition (f) table 3, initially presented a better performance. during the tests there was a convergence behaviour, and, at the end, the performances were very close. the wall showed wear resistance 1.1x higher when compared to the substrate. the optical micrographs of the worn caps produced by the micro-adhesive wear test are shown in figure 8. the analysed caps refer to the longest sliding distance (test time 40 min 880 m sliding distance). for the substrate and wall, the wear surface indicated two active wear mechanisms. the first type of abrasion is two bodies (indicated by red arrows), with the presence of directional scratches in the direction of sliding of the sphere. this wear mechanism occurred through the particles of the material itself that detach and adhere to the sphere [21]. the second mechanism observed is the adhesive (indicated by yellow arrows), represented by the transferred metal films. the same characteristics were observed throughout other similar tests performed in different places of the same pieces. figure 4: selected wall (f) from table 3 figure 5: optical micrograph of the as-built ti6al4v alloy. α and β phases highlighted with yellow lines. etching: kroll’s reagent. ti6al4v thin walls production using laser directed energy deposition (l-ded) process 129 figure 6: longitudinal section of the wall (f) etching: kroll’s reagent. figure 7: micro-adhesive wear graphics obtained for the substrate wall (f). barragan et al. (2021): international journal of engineering materials and manufacture, 6(3), 124-131. 130 figure 8: optical micrograph of the wear caps and interior of the wear caps from the substrate and wall (f). travelled distance: 880 m (40 min). the yellow and red arrows indicate the mechanisms of adhesive and abrasive wear on two bodies, respectively. 4 conclusions investigation on the characteristics of ti6al4v thin-walled structures with respect to dimensional characteristics, hardness and wear behaviour has been carried out, and based upon the findings from the experimental work the following conclusions can be drawn: 1. the use of the ded process for manufacturing thin walls with ti6al4v showed to be feasibly and presented good results, in terms of shape and geometry of the specimens. 2. due to the nature of the process that involves rapid cooling grain refinement appeared on the deposited walls. 3. for all walls, the hardness remains constant from the top to the interface, with values close to 400 hv3.0. 4. harness values shown an important improvement over wrought material, used as substrate. 5. the wear resistance of the best deposited wall, shown a better performance, during the wear tests with values around 10% higher. acknowledgement the authors would like to appreciate the financial support of the são paulo research foundation (fapesp) – grants 2016/11309-0; 2019/26362-2 and coordenação de aperfeiçoamento de pessoal de nível superior brazil (capes) finance code 001. references 1. ghosal, p., majumber, m. c., & chattopadhyay, a. (2018). study on direct laser metal deposition. materials today: proceedings, 5(5), 12509-12518. doi: 10.1016/j.matpr.2018.02.232 2. mahamood, r. (2018). laser metal deposition of metals and alloys. springer. doi:10.1007/978-3-319-649856_5 3. dass, a., & moridi, a. (2019). state of the art in directed energy deposition: from additive manufacturing to materials design. coatings, 9(7), 418. doi: 10.3390/coatings9070418 4. wang, f., cheng, x., zheng, g. m., yang, x. h., guo, q. j., & sun, q. l. (2019). study of micromilling parameters and processes for thin wall fabrications. precision engineering, 56, 246-254. doi: 10.1016/j.precisioneng.2018.12.005 5. jinoop, a. n., paul, c. p., nayak, s. k., kumar, j. g., & bindra, k. s. (2021). effect of laser energy per unit powder feed on hastelloy-x walls built by laser directed energy deposition based additive manufacturing. optics & laser technology, 138, 106845. doi: https://doi.org/10.1016/j.optlastec.2020.106845 https://doi.org/10.3390/coatings9070418 https://doi.org/10.1016/j.precisioneng.2018.12.005 ti6al4v thin walls production using laser directed energy deposition (l-ded) process 131 6. wu, y., & yang, l. (2021). elastic and failure characteristics of additive manufactured thin wall lattice structures with defects. thin-walled structures, 161, 107493. doi: 10.1016/j.tws.2021.107493 7. jinoop, a. n., paul, c. p., mishra, s. k., & bindra, k. s. (2019). laser additive manufacturing using directed energy deposition of inconel-718 wall structures with tailored characteristics. vacuum, 270-278. doi: 10.1016/j.vacuum.2019.05.027 8. demier, a. g. (2018). micro laser metal wire deposition for additive manufacturing of thin-walled structures. optics and lasers in engineering, 100, 9-17. doi: 10.1016/j.optlaseng.2017.07.003 9. banerjee, d., & williams, j. c. (2013). perspectives on titanium science and technology. acta materialia, 61(3), 844-879. doi: 10.1016/j.actamat.2012.10.043 10. kranz, j., & herzog, d. (2015). design guidelines for laser additive manufacturing of lightweight structures in tial6v4. journal of laser applications, 27, s14001. doi: 10.2351/1.4885235 11. du, f., zhu, j., ding, x., zhang, q., ma, h., yang, j., . . . fan, s. (2019). dimensional characteristics of ti-6al4v thin-walled parts prepared by wire-based multi-laser additive manufacturing in vacuum. rapid prototyping journal. doi: 10.1108/rpj-08-2018-0207 12. niz’ev, v. g., khomenko, m. d., & mirzade, f. k. (2018). process planning and optimisation of laser cladding considering hydrodynamics and heat dissipation geometry of parts. quantum electronics, 48(8), 743-748. doi:10.1070/qel16708 13. ren, y. m., lin, x., yang, h. o., tan, h., chen, j., jian, z. y., . . . huang, w. d. (2021). microstructural features of ti-6al-4v manufactured via high power laser directed energy deposition under low-cycle fatigue. journal of materials science & technology, 83, 18-33. doi: 10.1016/j.jmst.2020.12.026 14. astm international. (2014). standard specification for additive manufacturing titanium-6 aluminum-4 vanadium with powder bed fusion. west conshohocken, pa. doi:10.1520/f2924-14 15. addup. (2021, 1 15). beam machines. retrieved 12 20, 2020, from https://www.beammachines.com/products/modulo250 16. general electric. (2021, 2 25). retrieved from ap&c a ge additive company: https://www.advancedpowders.com/ 17. alfaia, m. a., oliveira, r., lima, t. s., mariani, f. e., casteletti, l. c., cheung, n., & garcia, a. (2020). effects of cooling rate and microstructure scale on wear resistance of unidirectionally solidified al-3.2wt.%bi-(1; 3) wt.%pb alloys. materials today communications, 25, 101659. doi: 10.1016/j.mtcomm.2020.101659 18. patel, p., jamnapara, n. i., zala, a., & kahar, s. d. (2020). investigation of hot-dip aluminized ti6al4v alloy processed by different thermal treatments in an oxidizing atmosphere. surface and coatings technology, 385, 125323. doi: 10.1016/j.surfcoat.2019.125323 19. arrazola, p. j., garay, a., iriarte, l. m., armendia, m., mayra, s., & le maitre, f. (2009). machinability of titanium alloys (ti6al4v and ti555.3). journal of materials processing technology, 209(5), 2223-2230. doi: 10.1016/j.jmatprotec.2008.06.020 20. dinda, g. p., dasgupta, a. k., & mazumder, j. (2009). laser aided direct metal deposition of inconel 625 superalloy: microstructural evolution and thermal stability. materials science and engineering: a, 509(1-2), 98104. doi: 10.1016/j.msea.2009.01.009 21. budinski, k. g. (2013). friction, wear, and erosion atlas. boca raton: crc press. doi: 10.1201/b15984 https://doi.org/10.1016/j.tws.2021.107493 international journal of engineering materials and manufacture (2020) 5(2) 50-54 https://doi.org/10.26776/ijemm.05.02.2020.03 m.h.f.al hazza 1 , k. muhammad 2 1 mechanical and industrial engineering department school of engineering, american university of ras alkhaimah po box 10021, ras al khamiah, uae 2 department of manufacturing and materials engineering international islamic university malysia po box 10, 50728 kuala lumpur, malaysia e-mail: muataz.alhazza@aurak.ac.ae reference: al hazza, m h f and muhammad, k. (2020). flank wear modelling in high speed hard milling of machining aisi d2 steel. international journal of engineering materials and manufacture, 5(2), 50-54. flank wear modelling in high speed hard milling of aisi d2 steel muataz hazza f. al hazza and khadijah muhammad received: 07 march 2020 accepted: 31 may 2020 published: 30 june 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 abstract high speed machining has many advantages in reducing time to the market by increasing the material removal rate. however, final surface quality is one of the main challenges for manufacturers in high speed machining due to the increasing of flank wear rate. in high speed machining, the cutting zone is under high pressure associated with high temperature that lead to increasing of the flank wear rate in which affect the final quality of the machined surface. therefore, one of the main concerns to the manufacturer is to predict the flank wear to estimate and predict the surface roughness as one of the main outputs of the machining processes. the aim of this study is to determine experimentally the optimum cutting parameters: depth of cut, cutting speed (vc) and feed rate (f) that maintaining low flank wear (vb). taguchi method has been applied in this experiment. the taguchi method has been universally used in engineering analysis. jmp statistical analysis software is used to analyse statically the development of flank wear rate during high speed milling of hardened steel aisi d2 to 60 hrd. the experiment was conducted in the following boundaries: cutting speed 200-400 m/min, feed rate of 0.01-0.05 mm/tooth and depth of cut of 0.1-0.2 mm. analysis of variance anova was conducted as one of important tool for statistical analysis. the result showed that cutting speed is the most influential input factors with 70.04% contribution on flank wear. keywords: aisi d2, high speed hard milling, taguchi, flank wear 1 introduction high speed hard milling (hshm) is an advanced machining processes in industry that merges three advanced machining processes: high speed milling, hard milling, and dry milling [1]. machining above 45 hrc are considered hard machining and usually ranging from 58 to 68 hrc [2]. on the other hand, high speed machining is not the same for all materials, high speed for one material is not considered a high speed for others. hshm can reduce manufacturing process cost and reducing time to the market. however, there are many challenges that faces the manufacturer in hshm. one of the main challenges is the increasing of flank wear extremely fast due to the high pressure and high temperature in the cutting zone. increasing the flank wear of the cutting tool will lead to damaging the final surface roughness. therefore, estimating and predicting the flank wear rate before the machining process is an essential issue. tool wear is defined as the amount of volume loss of tool material on the contact surface due to the friction between the cutting tool and workpiece [3]. it will give significant effect on the finished surface, accuracy, manufacturing cost and tool life. flank wear occurs on the flank face of the tool. this type of wear is basically between the tool and the workpiece. kalpakjian and schmid [4] mentioned it happens because the tool is rubbed along the machined surface. tool and machined parts dimensions vary due to the change and progress of flank wear, thus flank wear need to be controlled. the maximum range accepted for cutting hard materials is 0.3-0.5mm [5]. many researchers studied the output responses of hshm such as surface roughness [6][7], temperature [8] and flank wear [9]. they investigated the effect of cutting speed, feed rate and depth of cut on the final surface roughness using d2 as a work piece hardened to 52-56 hrc, and coated carbide as cutting tool with higher cutting speed 120-240 mm/min. they found that the best cutting parameters for minimizing the noise factors were cutting speed of 120 m/min, feed rate of 0.10 mm/tooth and depth of cut of 0.10 mm. and the cutting speed is the most significant factor flank wear modelling in high speed hard milling of machining aisi d2 steel 51 to the flank wear. one of the advantages in high speed hard machining is the power consumption. according to zhang [10], the energy consumption in high speed machining is lower because of low cutting forces and high removal rate. dudzinski [11] stated in his writing, this is an important aspect of advanced manufacturing technology to achieve high productivity and to minimize machining cost as the tool life is longer. in this research, the investigation of the effect of higher cutting speed up to 400m/min on the flank wear rate of hardened steel aisi d2 that hardened to 60-62 hrc and developing a new statistical model based on experimental work that can give valid results to the manufacturer in the boundaries of the research experiment. 2 experimental procedure this experiment was conducted using high speed milling in machining hardened steel aisi d2 60-62hrc. the experiment was conducted under dry machining to reduce thermal shock and cutting tool breakage. the chemical composition of aisi d2 is given in table 1. the machine used in conducting the experiment, the type of material, type of inserts used and other experimental set up is summarized in table 2. the cutting tool used in conducting the experiment is altin coated carbide (mitsubishi vp15tf) and 32 mm diameter tool holder for end milling produced by mitsubishi company. the specific cutting tool has axial rake angle of 5° and radial rake angle of -10°. the thickness of the insert is 3.5 mm, length of 10 mm, 6.35 width and 0.8 mm corner radius. the stated specifications of the insert are provided in mitsubishi materials manuals shown in table 3. the specifications of insert (mitsubishi materials manual, 2015). the experiment has been conducted for three levels and three factors. the experiments were conducted using taguchi’s orthogonal array l9 as a design of experiments.is used in taguchi method. the cutting parameters and cutting levels are shown in table 4. table 1: chemical composition of aisi d2 table 2: experimental set up machine vertical center nexus 410a-ii material aisi d2 dimension of material 150mm x 101 mm x 45 mm inserts mitsubishi vp15tf with altin coating cutting condition dry table 3: specifications of insert (mitsubishi materials manual, 2015) insert material and grade ansi tool dia. (mm) axial rake angle (º) radial rake angle (º) insert thickness (mm) insert length (mm) insert width (mm) corner radius (mm) coated carbide vp15tf aomt 184808peerh 32 5 -10 3.5 10 6.35 0.8 table 4 cutting parameters and levels parameters unit levels 1 2 3 cutting speed m/min 200 300 400 feed rate mm/tooth 0.01 0.03 0.05 depth of cut mm 0.10 0.15 0.20 3 results and discussion the experimental results from table 4 were analyzed with analysis of variance (anova), which used for identifying the most affecting the input factors on the performance measures. figure1 shows images of inserts with wear. the images were captured using nickon optical microscope with 5x magnification. composition c mn si cr ni mo v wt. % 1.40 – 1.60 0.6 0.6 11.0 – 13.0 0.3 0.7 – 1.2 1.1 al hazza and muhammad (2020): international journal of engineering materials and manufacture, 5(2), 50-54 52 table 3: orthogonal array l9 of taguchi experiment design and experimental results run vc (m/min) f (mm/tooth) depth of cut (mm) avg. flank wear (mm) 1 200 0.01 0.1 0.0025 2 200 0.03 0.15 0.0034 3 200 0.05 0.2 0.0069 4 300 0.01 0.15 0.0045 5 300 0.03 0.2 0.0075 6 300 0.05 0.1 0.0063 7 400 0.01 0.2 0.009 8 400 0.03 0.1 0.0126 9 400 0.05 0.15 0.0113 run 1 run 2 run 3 run 4 run 5 run 6 run 7 run 8 run 9 figure 1: optical images of weared insert flank wear modelling in high speed hard milling of machining aisi d2 steel 53 table 5 shows the anova result for flank wear analysis. r-square value for this model is 0.963215. this indicates that the developed model fits and explains 96.32% of the variation in flank wear. the prob > f value shows that there is only 2.32% chance error in the developed model due to noise. the model developed is said to be significant at 95% confidence level as the value of prob > f less than 0.05. f ratio for each cutting parameter is compared to determine the significant cutting parameters. the % contribution indicated that cutting speed affects flank wear the most with 70.04% and followed by the cutting feed with 12.21% of contribution. depth of cut has 0.39% contribution and it is said to be insignificant. feed-depth of cut and speedfeed interaction have a small effect on flank wear rate. the effects are small and not significant to the change of flank wear rate. the statistical model was developed using jmp software has generated the modelling equation for flank wear as follow: 𝐹𝑙𝑎𝑛𝑘 𝑤𝑒𝑎𝑟 = −0.0074 + (0.00004 ∗ 𝑠𝑝𝑒𝑒𝑑) + (0.0713 ∗ 𝑓𝑒𝑒𝑑) + (−0.0067 ∗ 𝑑𝑒𝑝𝑡ℎ 𝑜𝑓 𝑐𝑢𝑡) + (𝑠𝑝𝑒𝑒𝑑 − 300) ∗ [(𝑓𝑒𝑒𝑑 − 0.03) ∗ (−0.0066)] + (𝑓𝑒𝑒𝑑 − 0.03) ∗ [(𝑑𝑒𝑝𝑡ℎ 𝑜𝑓 𝑐𝑢𝑡 − 0.15) ∗ (2.1965)] figure 2 shows the comparison of mean between experimental values and developed model using modelling equation generated by jmp software. run 3 from figure 2 has the minimum difference while run 8 has the maximum difference between experimental and developed model values. the variation in flank wear values in due to the presence of noise during machining process such as vibration and random disturbances. the two graphs in figure 2 show a small deviation between experimental and developed model values. table 4: anova for tool wear source df sum of squares f ratio % contribution remark cutting speed 1 0.00006993 59.909 70.04 significant feed 1 0.00001219 10.4422 12.21 significant depth of cut 1 0.00000039 0.3335 0.39 not significant speed*feed 1 0.00000371 3.1795 3.72 not significant speed*depth of cut 1 0.00001013 8.6796 10.15 not significant error 3 0.0000035 total 8 0.00009985 rsquare = 0.963215 rsquare adj = 0.901907 prob > f = 0.0232 figure 2: comparison of mean between developed model and experimental al hazza and muhammad (2020): international journal of engineering materials and manufacture, 5(2), 50-54 54 4 conclusions the results of this study have been analysed and can be concluded by the following: 1. cutting speed affects flank wear the most. second influential input factor is cutting feed and effect of depth of cut is said to be insignificant. 2. high speed hard milling is an effective process in reducing the total machining time. however, the flank wear length needs to be monitored and estimated before the machining process to avoid the damage of surface roughness. 3. the new model shows a high accuracy as shown in figure 1 acknowledgement the authors are grateful to the department of manufacturing and materials engineering at international islamic university malaysia where this research has been conducted. references 1. al-hazza, m. h. f., & bourini, i. f. (2016). statistical analysis of tooling cost in high speed end milling for hardened steel. electronic journal of applied statistical analysis, 9(3), 530-539. 2. astakhov, v. p. (2011). machining of hard materials–definitions and industrial applications. in machining of hard materials (pp. 1-32). springer, london. 3. zhang, s., li, j. f., sun, j., & jiang, f. (2010). tool wear and cutting forces variation in high-speed end-milling ti6al-4v alloy. the international journal of advanced manufacturing technology, 46(1), 69-78. 4. kalpakjian, s., & schmid, s. r. (2014). manufacturing engineering and technology. k. v. sekar (ed.). upper saddle river, nj, usa: pearson. 5. davim, j. p. (ed.). (2011). machining of hard materials. springer science & business media. 6. cui, x., zhao, j., jia, c., & zhou, y. (2012). surface roughness and chip formation in high-speed face milling aisi h13 steel. the international journal of advanced manufacturing technology, 61(1-4), 1-13. 7. al-hazza, m. h. f., bt ibrahim, n. a., adesta, e. t., khan, a. a., & sidek, a. b. a. (2017, march). surface roughness optimization using taguchi method of high-speed end milling for hardened steel d2. in iop conference series: materials science and engineering (vol. 184, no. 1, p. 012047). iop publishing. 8. zhang, q., zhang, s., & li, j. (2017). three-dimensional finite element simulation of cutting forces and cutting temperature in hard milling of aisi h13 steel. procedia manufacturing, 10, 37-47. 9. al-hazza, m. h. f., bt ibrahim, n. a., adesta, e. t., khan, a. a., & sidek, a. b. a. (2017, march). flank wear analysing of high speed end milling for hardened steel d2 using taguchi method. in iop conference series: materials science and engineering (vol. 184, no. 1, p. 012048). iop publishing. 10. zhang, j. z., chen, j. c., & kirby, e. d. (2007). surface roughness optimization in an end-milling operation using the taguchi design method. journal of materials processing technology, 184(1), 233-239 11. dudzinski, d., devillez, a., moufki, a., larrouquere, d., zerrouki, v., & vigneau, j. (2004). a review of developments towards dry and high-speed machining of inconel 718 alloy. international journal of machine tools and manufacture, 44(4), 439-456. international journal of engineering materials and manufacture (2019) 4(4) 146-153 https://doi.org/10.26776/ijemm.04.04.2019.02 mechanical characteristics of heat-treated medium carbon steel quenched using blending different types of vegetable oils tajudeen kolawole ajiboye and adam olalekan abdulsalam received: 20 september 2019 accepted: 20 november 2019 published: 15 december 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract quenching and tempering are processes that strengthen and harden materials like steel and other iron-based alloys. conventional heat treatment procedures for producing martensitic steels generally involve continuous and rapid cooling of an austenitized specimen in some types of quenching media such as water, oil, or air, in which the properties of steel quenched depends largely on the properties of these quenching media. four vegetable oils: cotton seed oil, neem seed oil, shea butter oil and palm kernel oil, were blended into two different samples, namely blend a: cotton seed oil and neem seed oil and blend b: cotton seed oil, neem seed oil, palm kernel oil and shear butter oil. these were mixed in different ratios. samples of medium carbon steel were heated to 850°c and soaked for 10 minutes inside a muffle furnace before quenching in the prepared quenching media. the microstructure and mechanical properties of the samples were investigated to determine the quenching performance of the vegetable oil blends. the results showed that blend a1 produced best properties for the impact strength and yield strength with values of 0.82 j/mm² and 429.71n/mm² respectively. on the other hands, blend a2 quenched steel had best properties for the hardness and tensile strength with 52.8 hra and 892 n/mm² respectively. microstructure analysis also confirms improved hardness and toughness exhibiting more martensite for blend containing the four oils than blend with only two oils. keywords: blend, martensite, quenchants, medium carbon steel 1 introduction quenching operation belongs to the processes of heat treatment, for which the highly intensive and dynamic heat transfer at the surface of the body occurs. determination of the temperature field in the cooled body requires unity conditions of the heat conduction equation. comparisons of different quenchants in heat treatment processes of steels are of great importance in order to achieve desired hardness, strength or toughness and minimizing the possibility of occurrence of quench cracks due to evolution of residual stresses (totten, howes and maurice, 1997). the choice of effective quenching medium after heat treatment is very critical in ensuring the achievement of desired mechanical properties; hence, selection of a quenchant depends on the quench sensitivity of a particular grade of steel and the severity of quench medium (buczek and telejko, 2004, feng and tahir, 2008). three stages of quenching are vapour blanket, in which vapour film surrounding the component acts as an insulating blanket reducing the heat flow from component subjected to quenching. the second stage is known as the nucleate boiling stage where the vapour film formed collapses and high heat extraction rates are achieved. the third stage known as convective cooling stage begins when the temperature of the metal surface is reduced below the boiling point of the quenching liquid; cooling rate is low during this stage (buczek and telejko, 2004, gorysushin et al, 1991). there are several factors influencing the effectiveness of a quenching medium in its ability to withdraw heat from a quenched part. these factors include: temperature of the medium, degree of agitation, surface conditions of the part and the type of quenching medium (feng and tahir, 2008, boyer, 1984). in addition, the configuration of the quenched part also plays a role in the rate of heat transfer during quenching. the temperature of the medium has a drastic effect on its ability to extract heat from a hot part, hence lowering the bath temperature increases the heat transfer rate (totten, bates and clinton, 1993george and scott, 2003). the heat extraction is still dependent on the t. k. ajiboye and a. o. abduslam department of mechanical engineering faculty of engineering and technology university of ilorin, ilorin, nigeria e-mail: ajitek@unilorin.edu.ng reference: ajiboye, t. k. and abdulsalam, a. o. (2019). mechanical characteristics of heat–treated medium carbon steel quenched using blending different types of vegetable oils. international journal of engineering materials and manufacture, 4(4), 146-153. mailto:ajitek@unilorin.edu.ng mechanical characteristics of heat–treated medium carbon steel quenched using blending different types of vegetable oils characteristics of the medium itself. in general, higher quenchant temperatures lower the temperature at which a total vapour blanket is maintained in the medium. as a result, it will lengthen the duration of the first stage of quenching, which lengthens the time at which the part is cooled at slower cooling rates (mills, 1999, incropera and dewitt, 1996). depending on the medium itself, higher bath temperatures may decrease viscosity, which affects bubble size and therefore, decrease the rate of heat transfer during the third stage of quenching. in the case of water, since it produces the fastest cooling rates, lower temperatures produce high thermal gradients between the bath and the part (feng and tahir, 2008, boyer, 1984). as a result, high thermal stresses will be induced and the risk of distortion or cracking will increase. on the other hand, as the temperature of the water is increased to avoid cracking, the physical properties of the material decrease due to incomplete saturation of the solution during quenching (chaves, 2001, bell and staines, 1983, joseph et al (2016) and singh, v. (2012). agitation plays a vital role in the effectiveness of a particular medium to quench a part, and is one of the factor that determines the success of the quenched products (chaves, 2001). in general, agitation increases the rate of heat transfer throughout the quenching process. during the vapour blanket stage, agitations will breakdown the blanket much earlier in the quench and force the boiling stage to begin. as a result, a stage of slow cooling is cut short and replaced with a stage of rapid heat transfer. overall, the part will be cooled at a faster rate. in addition, it will also produce smaller, more frequent bubbles during the boiling stage, which, in turn, creates faster rates of heat transfer throughout the part (adeyemi and adedayo, 2009 and simencio-otero et al (2017). in terms of its mechanical effects, any solids that have formed on the test piece will be agitated off of the surface and allow for maximum heat transfer since the medium will be in direct contact with the exposed surface. these gels would have acted as an insulating layer to slow down the cooling rate, but with the use of agitation, this layer is mechanically removed and maximum heat transfer can be achieved. finally, agitation forces cool liquid to constantly be circulated to the work piece in place of the hot liquid (feng and tahir, 2008, boyer, 1984). therefore, higher temperature differences will always exist between the medium and the surface, resulting in faster rates of heat dissipation (incropera and dewitt, 1996). lowest cooling rates are observed on surfaces that are newly machined or bright etched, whereas faster rates are obtained by surfaces with oxide films and stains. in addition, surface roughness has a similar relationship regarding cooling rates; the rougher the surface, the faster the cooling rate (fernandes and prabhu, 2008). this phenomenon can be attributed to the stability of the vapour phase on each surface. if the surface is smooth, then the vapour layer becomes uniform and stable, whereas if there are discontinuities on the surface, then it becomes easier to break down the layer and induce the boiling stage (incropera and dewitt, 1996). furthermore, the application of non-reflective coatings will increase heating and affect the quench of the material (kobasko, canale and totten, 2010, odusote, ajiboye and abdulkarim, 2012 and pranesh rao, k.m. and prabhu, k.n. (2015). 2. material and method 2.1 specimen’s preparation the medium carbon steel was cut into eight (8) pieces of equal length, 65mm length by 14mm diameter. four (4) of the samples were machined to 60mm length by 12.5mm diameter for hardness and impact test while the remaining four (4) were machined to a total length of 37.4mm, gauge length of 24.3mm, bigger diameter (d) 7.8mm and smaller diameter (d) 4.9mm for tensile test. these specimens were heat-treated and quenched before the required tests were carried out. before commencing the experiment, the chemical composition of the medium carbon steel was carried out as detailed in table 1. the four vegetable oil, (cotton seed oil, neem seed oil, shea butter oil and palm kernel oil) were sourced from local market in niger and katsina states, nigeria. they were blend into 2 different samples; a and b. after the mixing of the blends, the following physical properties test were carried out on each of the blended oil products for further analysis and for necessary comparison with the available quenchants. blend a: this contains cotton seed oil and neem seed oil mixed in equal volume. blend b: this contains cotton seed oil, neem seed oil, palm kernel oil and shear butter oil mixed in equal volume. 2.2 viscosity test the blended oil was put at the edge of the capillary tube and then allow to drawn to the lower and upper meniscus. when the oil reaches the upper meniscus, it was then allowed to drop under and the time taken for the oil to move from the upper meniscus to the lower meniscus was recorded. the process was also carried out for water at 25°c. the time taken for the water was used as a reference to obtain the viscosity of the blended oil. the process was repeated four times for each of the blended samples to obtain and average value. table 1: chemical composition of the medium carbon steel % element c:0.356, si:0.16, mn:0.75, p:0.032, s:0.041, cr:0.1, mo:0.0, ni:0.11, al:0.5, co:0.037, cu: 0.129, v:0.006, pb:0.005, sn:0.009 and fe:98.2 147 ajiboye and abdulsalam (2019): international journal of engineering materials and manufacture, 4(4), 146-153 2.3 acidic value the mixture of ethanol and toluene in ratio 1:1 by volume was first neutralized prior to use by the application of ethanolic potassium hydroxide solution in the presence of 0.3ml of indicator per 10ml of the mixture. 2g of the oil blend was weighed into a 250ml conical flask, 50ml of previously neutralized mixture of toluene and ethanol was added to the flask. a few drop of phenolphalein indicator was added and the content was titrated against 0.1ml/litre solution of ethanolic potassium hydroxide solution until the indicator changes to pink colour. the procedure was repeated for the second blended oil. 2.4 iodine value one gram (1 g) of the oil blend was weighed into a conical flask. 10 ml of chloroform and 12 ml of dams reagent was added to the flask. stopper was then inserted and the content of the flask was vigorously swirled. the flask was then placed in the dark for 1hour 30minutes after which 10ml of potassium iodide solution and 750ml of water were added. the contents of each flask was titrated with 0.1mol/1 sodium thiosulphate solution until the yellow colour due to iodine has almost disappeared. few drops of starch were then added and titration continued until the blue colour disappeared after vigorous shaking. the process was repeated for the other blend. 2.5 heat treatments and quenching procedure all the eight medium carbon steel samples which were readily prepared for the various test were loaded into a muffle furnace shown in figure 1 and heated to a temperature of 850°c. after attaining this temperature, they were allowed to soak for 13minutes based on the specimen dimension. it was then quenched in the prepared quenching media. 3 mechanical properties test 3.1 tensile test tensile tests were conducted at various strain rates of 200, 500, 1000, 1500 and 1750 mm/min for all the specimens (ndaliman, 2006). each of the specimens was inserted one after another into the machine jaws and having fastened the specimen properly at both ends for tensile test. the arrangement and the specimen are shown in figure 2 and figure 3 respectively. the machine recorded the stress, strain, elongation, yield strength and ultimate tensile strength which were printed for further analysis (smith and hashemi, 2006, thomas, samuel and glenn, 1996). figure 1: muffle furnace figure 2: arrangement of the specimen on the machine chuck figure 3: tensile sample where; ∅out = diameter of gripping heads ∅in = diameter of the gauge length la = minimum gripping length. lo = gauge length 148 mechanical characteristics of heat–treated medium carbon steel quenched using blending different types of vegetable oils the diameter of the test section for the various samples were measured, using vernier calliper. these was repeated on 4 times on similar prepared samples after which an average value was calculated for further analysis. the percentage reduction, the percentage elongation, yield stress and ultimate tensile strength was obtained thus: 4 2d areasectionalcross π = (1) areasectionalcross loadyield stressyield = (2) areasectionalcross loadmaximum stresstensile = (3) 3.2 hardness test the hardness of a material is resistance to penetration under a localized pressure or resistance to abrasion. hardness tests provide an accurate, rapid and economical way of determining the resistance of materials to deformation. the indentec tech universal hardness testing machine shown in figure 4 was used to carry out the hardness test. the type of hardness test was diamond rockwell. the minor load of the machine is 10kg and the major load is 60kg, while the indentor is a diamond cone (120°). a load is applied by pressing the indenter at right angle to the surface being tested. the hardness of the material depends on the resistance which exerts during a small amount of plastic or yielding. the resistance depends on elasticity, viscosity, friction and the intensity and distribution of plastic strain produced by a given tool during indentation. the specimen as shown in figure 5 was place securely upon the anvil, elevated so that it can come in contact with the penetration of the diamond cone indentor. the indention number will display on the digital screen for readings on the scale, which is the indention number of the material. the procedure was repeated 4 times on each sample and the average value was calculated for further analysis. figure 4: indentec tech universal testing machine (model number, 900–331d, unilorin, nig.) figure 5: hardness sample 149 ajiboye and abdulsalam (2019): international journal of engineering materials and manufacture, 4(4), 146-153 3.3 impact test impact test signifies the toughness of a material, i.e., the ability of material to absorb energy during plastic deformation. static tension tests of un-notched specimens do not always reveal the susceptibility of a metal to brittle fracture. this important factor is determined by impact test shown in figure 6. toughness takes into account both the strength and ductility of the material. several engineering materials have to withstand impact or suddenly applied loads while in service. impact strengths are generally lower as compared to strengths achieved under slowly applied loads, of all the types of impact test, the notch bar tests are most extensively used. impact test measures the energy necessary to fracture a standard notch bar by applying an impulse load. the test measures the notch toughness of the material under shock loading. figure 6: izod impact machine figure 7: impact test sample with notch the test sample was shown in figure 7 which was first notched to 1mm. the striking hammer (pendulum) was in safe test position. the weight of the hammer is 162.7 joules. the specimen was firmly held in the impact testing machine vice in such a way that the notch face the hammer and is half inside and half above the top surface of the vice. the striking hammer is place at its top most striking position and was locked at that position. the gauge of the machine was brought to zero. the hammer was released which fall under gravity and break the specimen as its swing. at its topmost height after breaking the specimen, the indicator stops moving, while the pendulum falls back. the indicator at that topmost final position was noted. the hammer was brought back to its idle position. the process was repeated for the other samples. 4 microstructural examination small portions were cut out from the 60mm long specimens to produce a surface which appeared scratch free when viewed with the aid of the microscope. this surface was first grind using hand file and later polished to remove the marks left by grinding. the polishing process caused a very thin layer of amorphous metal to be burnished over the surfaces of the specimens, thus hiding the crystal structure. the specimen was etched with nital to reveal the crystal structure. this etching reagent dissolved the ‘flowed’ or amorphous layer of metal. the microstructural examinations of the etched surfaces of the specimens were viewed under a metallurgical microscope as shown in figure 8. 150 mechanical characteristics of heat–treated medium carbon steel quenched using blending different types of vegetable oils 5 results and discussions the result of the physical properties of the blends were given in table 2 while figure 9 and figure 10 show the plot of load/extension for blend a and b respectively. tables 3, 4 and 5 show the percentage elongation/reduction, yield/tensile stress; hardiness value and impact energy respectively. figure 11 and figure 12 show the microstructure of the steel samples quenched in the blend to reveal the grain structural and their arrangement. figure 8: metallurgical microscope figure 9: graph of load against extension for blend a figure 10: graph of load against extension for blend b table 2: physical properties of the blends s/n blends viscosity (cp) flash point (°c) acidic value iodine value (%) 1 2 blend a blend b 39.75 58.25 270 300 14.59 25.81 2.28 2.17 table 3: percentage elongation/reduction, yield/tensile stress of the samples s/n sample diameter (mm) % elongation % reduction yield stress tensile stress (n-mm2) 1 blend a 4.9 7 20 0.77 2 blend b 4.9 1.06 table 4: hardness value of samples s/n samples average hardness (hra) 1 2 blend a blend b 45.7 54.3 151 ajiboye and abdulsalam (2019): international journal of engineering materials and manufacture, 4(4), 146-153 table 5: impact energy of the samples s/n sample diameter (mm) notch energy (j) 1 2 blend a blend b 12.5 12.5 11.5 11.5 62.34 73.21 figure 11: microstructure of the sample quenched in 500 ml of cottonseed oil and 500 ml of neem seed oil (x400) figure 12: microstructure of the sample quenched in 250 m1 of cottonseed oil, 250 ml of neem seed oil, 250ml of palm kernel oil and 250ml of shea butter oil (x400) from the result obtained, blend a has a lower viscosity, acidic value and flash point compare to blend b, while blend a has a higher iodine value than blend b. the viscosity of blend a and blend b is 39.75 and 58.25 centipoise respectively, the acidic value of blend a and blend b is 14.59 and 25.81 mg/g respectively. the flash point for blend a and blend b is tested to be 270 and 300°c, blend a and blend b possesses an iodine value of 2.28 and 2.17 % respectively. the graph of load against extension shows that blend a produces a strong material which is not ductile while blend b produces a brittle material. it was also noticed that there was a little strain with the increase in stress. with blend a fracture occurs at 14kn while with blend b, there was no fracture under 20kn load which is the maximum load for the tensometer used. the result shows that the tensile stresses produced with blend a and blend b was 0.77 and 1.06 n-mm2 respectively while the percentage elongation and reduction for sample with blend a is 7 and 20% respectively. the hardness value obtained for sample with blend a is lower than that of blend b, this means that the medium carbon steel quenched in 250ml each of cottonseed oil, neem seed oil, palm kernel oil and shea butter oil has high hardness than medium carbon steel quenched in 500ml of cottonseed oil and neem seed oil. the hardness value obtained with blend a is 45.7 hra while that with blend b is 54.3hra. sample quenched with blend a shows high impact strength than of blend b. the impact strength of sample quenched with blend a is 62.4 joules while that quenched with blend b is 41.4 joules. 6 conclusions 1. it was established that vegetable oils can be used as quenching medium for medium carbon steel since the mechanical properties of the samples quenched using the blending of different oil indicates an improved properties which depends on different combination and mixing ratios 2. samples quenched in the blend containing each of the oil i.e. blend b exhibit high tensile strength, hardness and impact energy value compared to the samples quenched in the blend containing only two of oil. this may be due to its high viscosity, acidic and low iodine value, and possibly due to the formation of martensitic structure after quenching. 3. blend a improves the ductility of the steel samples because it produces lower cooling rate compared with blend b. therefore, blend a would be a viable quenching medium in an areas where improved elongation of the sample is very critical 152 mechanical characteristics of heat–treated medium carbon steel quenched using blending different types of vegetable oils reference adeyemi m.b and adebayo s.m (2009). vegetable oils as quenchants for hardening medium carbon steel. journal of applied science and technology, 14 (1-2), 74-78. bell, t. and staines, a. m. (1983). heat treatment techniques applied in manufacturing of tools and dies require for the production of engineering spare parts. united nations industrial development organization; core industries group meeting on the manufacture of cast/forged parts, cairo, egypt. boyer, h. e. (1984). practical heat treating, 1st ed., american buczek, a. and telejko, t. (2004). inverse determination of boundary condition during boiling water heat transfer in quenching operation. journal materials processing technology, 155-156; 1324-1329 chaves, j.c., the effect of surface condition and high temperature oxidation on quenchinh performance of 4140 steel in mineral oil, in manufacturing engineering 2001, worcester polytechnic institute: worcester. 8,9,29 feng, c. and tahir i.k. (2008). the effect of quenching medium on the wear resistance of a ti-6al-4v alloy. journal of material science, 43, 788-792 fernandes, p. and prabhu, k.n. (2008). comparative study of heat transfer and wetting behavior of conventional and bioquenchants for industrial heat treatment. international journal of heat and mass transfer. 51:526-538. george e totten, d scott mackenzie (2003). handbook of aluminum: vol. 1: physical metallurgy and processes, 1, crc press. goryushin, v. v istomin, n. n. ksenofontov, a.g. marsel, a.v. yu shevchenko, s (1991). metal science and heat treatment, 41 (1-2, 3-7). metals handbook desk edition, asm international, materials park, 1989. incropera, f. p., and dewitt, d. p. (1996). fundamentals of heat and mass transfer, wiley, new. joseph babalola agboola*, oladiran kamardeen abubakre, edeki mudiare and michael bolaji adeyemi (2016); performance assessment of vegetable oil and mineral oil blends during heat treatment of medium carbon steel; int. j. microstructure and materials properties, vol. 11, nos. 3/4 kobasko, n.i. carvalho de souza, e, canale l.c.f. totten g.e. (2010). vegetable oil quenchants: calculation and comparison of the cooling properties of a series of vegetable oils, journal of mechanical engineering mills, a. f., heat transfer, prentice hall. ndaliman, m.b. (2006). an assessment of mechanical properties of medium carbon steel under different quenching media. au j.t. 10(2), 100-104. odusote, j. k. ajiboye, t. k. and abdulkarim b. (2012). evaluation of mechanical engineering properties of medium carbon steel quenched in water and oil au j.t. 15 (14), 218-224 pranesh rao, k.m. and prabhu, k.n. (2015) ‘determination of wetting behavior, spread activation energy, and quench severity of bioquenchants’, met. mat. trans. b, vol. 38, pp.631–640. rajan, t.v.; sharma, c.p.; and sharma, a. (1998). heat treatment principles and techniques. prentice-hall of india private limited, new delhi. smith, w.f. and hashemi, j. (2006). foundations of materials science and engineering”, 4thedition; mcgraw’shill book. 28-36. singh, v. (2012) ‘assessment of wetting kinematics and cooling performance of select vegetable oils and mineral vegetable oil blend quench media’, materials science forum, vols. 830–831, pp.160–163. simencio-otero, r.l.; viscaino, j. m., totten, g. e.; meekisho, l.; canale, l. c. f. 29th heat treating society conference and exposition, columbus, oh, october 24-26, 2017. thomas g. diggers, samuel j. rosenberg and glenn w. geil (1966). heat treatment and properties of iron and steel. 10-19 totten, g. e., bates, c. e., and clinton, n. a. handbook of quenchants and quenching technology, materials park, oh: asm international, 1993 totten, g.e., howes, maurice a.h. (1997). steel heat treatment handbook. w.h cuberly, ramon bakerjian tools and manufacturing engineers handbook desk edition 153 http://books.google.com/books?hl=en&lr=&id=wbwv3nt1gp0c&oi=fnd&pg=pr3&dq=info:5ymtkpiyuswj:scholar.google.com&ots=hvs7i22zwi&sig=5zjibrp6hg2v2ebo3rbuth-a6dk international journal of engineering materials and manufacture (2022) 7(2) 47-53 https://doi.org/10.26776/ijemm.07.02.2022.01 dewanti, b. s. d. 1, 2 , adesta, e. y. t. 1, 3 and ismail, a. f. 1 1 department of materials and manufacturing engineering, international islamic university malaysia, po box 10, 50728 kuala lumpur, malaysia. 2 department of agroindustrial technology, universitas brawijaya, jl. veteran, east java, indonesia s 3 universitas indo global mandiri, jl. jendral sudirman, palembang 30129, indonesia e-mail: eadesta@uigm.ac.id reference: dewanti et al. (2021). unsteady heat conduction on the porous media in the gap with heater from below. international journal of engineering materials and manufacture, 7(2), 47-53. conduction heat transfer on the porous media in the gap with heater from below beauty suestining diyah dewanti 1, 2 , erry yulian t. adesta 3 and ahmad faris ismail 1 received: 07 february 2022 accepted: 03 april 2022 published: 15 april 2022 publisher: deer hill publications © 2022 the author(s) creative commons: cc by 4.0 abstract conduction heat transfer in gaps containing many porous objects has not been widely discussed, despite several applications. this study aims to determine the mechanism and calculate conduction heat transfer in porous objects and whether there is a change in the thermal conductivity value. the research started from a mathematical model with a horizontal medium, and the results were matched with the simulation results. porous objects contain water that can evaporate. this study used clove buds stacked with a certain thickness which caused porous between the piles of cloves. so, this research uses several heat transfer formulas related to porous media. the new formula is obtained to get the thickness of cloves pile based on the amount of porosity of objects and the porosity between the piles of objects. keywords: porous objects, conduction, gaps, heat transfer. 1 introduction heat transfer in porous media has become an essential subject in mechanical engineering. this study presents experimental and numerical theory investigations of the effective thermal conductivity in porous media. porous objects are very numerous, especially in agricultural products that need drying. the purpose of drying agricultural products is to get good quality in heat and mass transfer. mining material that will be processed usually needs to be drained so that water is not disturbed in the process. this research is about conduction heat transfer in a set of porous objects in the gap to get an equation that calculates the thickness of the cloves pile based on the amount of porosity of objects and the porosity between the piles of objects. this research starts from the translation of equations related to conduction heat transfer and porous objects. furthermore, conducting research by heating a set of porous objects in the gap to get the value of energy and conduction requirements of porous objects. the success of this study can be used as a basis for the process of porous heating objects based on conduction. research carried out by several researchers, such as research by zilong et al. (deng et al. 2017), with the increase in porosity can lead to a smaller effective thermal conductivity. the ratio of thermal conductivity of the solid matrix to the fluid phase is an essential parameter in determining heat conduction. the theory about average volume was developed to estimate both stagnant thermal conductivity and thermal dispersion conductivity within porous media (yang and nakayama 2010). experimental results relating to heat conduction refer to the situation that conduction with liquid is stagnant, normal toward fluid velocity, and in a diagonal parallel to the fluid velocity (telles and massarani 1974). it was shown that these observations qualitatively agree with the last item's theoretical criteria of conclusions and enough for the determination of parameters in the tensor function. the study determined the effective stagnant thermal conductivity of cu-btc and fe-btc materials and examined the effects of introducing improved heat transfer structures such as aluminium foam or wire (henriksen 2013). simulations and experiments with porous medium (pumice stone) bottom and top of the sample are cooled and heated using heat exchangers unsteady heat conduction on the porous media in the gap with heater from below 48 and hot water baths (salati 2014). the representative base cell of concrete is selected to determine homogenized tensors of heat conductivity numerically. depending on the geometric properties of the cell, sensitivity analysis has enabled us to highlight the effect of moisture content and material porosity on homogenized heat conductivity tensors (bennai et al. 2018). theoretically, predicting the thermal conductivity with the cubic cell model requires the knowledge of the thermal conductivity of the solid particle and the materials atmospheric gas or ice and the porosity of the soil (gori and corasaniti 2004). developed porosity and saturation-dependent thermal conductivity models in porous media using percolation-based effective-medium approximation. models function the properties, e.g., air, solid matrix, saturating fluid thermal conductivities, a scaling exponent, and a percolation threshold (ghanbarian and daigle 2016). when the thermal conductivity of the solid-phase and wet phase is greater than that of the gas phase, the effective thermal conductivity of unsaturated fractal porous media decreases with decreasing degree of and increasing fractal dimension for pore area saturation fractal dimension for tortuosity and porosity (kou et al. 2009). developing a heat transfer model in the rule of a mixture of porous objects is necessary to predict thermal conductivity. the development of this mixing rule is based on particle size distribution data for non-combined porous media. where solid and liquid phases are considered (evgeny skripkin 2015). an experimental study with sintered porous media has been employed on mini heat pipes (mhp) in the capillary transport of working fluid from the condenser to the evaporator section. the thermal resistance of the interface showed to be negligible for the determination of the effective thermal conductivity of the porous media composed of layers (florez et al., 2011). 2 mathematic model this mathematical model is intended for derivatives of conduction equation formulas on porous objects in the gap. conduction that occurs is transient, and the heating temperature remains, but there is a vapor so that there will be a change in the value of the material's heat conductivity. the porosity of a group of materials: pm f v v = the porosity of single material: sp w v v = where vf is a volume of fluid; vpm is a volume of porous media; vw is a volume of water; vsp is a solid volume. figure 1. porosity material the heat conductivity of materials for porous media, according to (adrian 2013). if the heat conduction takes place in series: = pm k 1 s k )1( − + f k  (1) when viewed from the composition of the solid body, the structure drawn in series is taken; subsequently, the series formula is used. the heat conductivity of materials for solid objects (ks) contains water, so this material is also a porous media in which the series is arranged. = s k 1 p k )1( − + w k  (2) this solid material, if exposed to heat energy, the water in the object will evaporate; with water evaporating, the porous media will shrink so that equation (2) will affect equation (1). if equation (2) is entered into equation (1), it will become a series with the series equation: pwf pm kkk k )1)(1()1( 1  −− + − + = (3) when kpm is the thermal conductivity of porous media; ks is the thermal conductivity of solid; kf is the thermal conductivity of fluid; kp is the thermal conductivity of porosity in single material; kw is the thermal conductivity of water. dewanti et al. (2022). international journal of engineering materials and manufacture, 7(2), 47-53 49 the principle of conservation of energy for the porous media, surface area a, and thickness of dy, figure 1, can be stated as follows: the formula for heat transfer of steady conduction is ).(... tatoah dy dts ak −= where, y = 0, t = ti y = l, t = to ).( )( )( tatoh ltlo toti k −= − − ).( .)..( ltlohk tiktaltloh to −+ +− = (4) in a steady-state, to has not changed up and down. with the warming of the porous media, its nature will also change. this change is due to the evaporation of water contained by solid material in the porous media. with the evaporation of water in solid material, there will be changes in the value of heat conductivity, specific heat, and density, the thickness of porous media, the porosity of solid material, and porous media's porosity. with these changes, the value of to will change according to some of these variables' rate of change. basic formula from (kreith, raj m., and mark s. 2011), a simple equation can be based on changes in energy from porous media as follows: change in internal energy of the porous media during dt = heat flow from the porous media to the air during dt dm.cp. dt = h. a dta.dt ρ.dy.a.cp dt = h.a dta.dt ρ.cp ʃʃdy dt = h ʃʃdt dta ρ.dy.cp (tr ta) = h.(to – ta).dt if l = 0 t = ti and l = y t = to, l >> y t = ta ρ.(l-0).cp (tr ta) = h (to – ta)(t1 – to) if t = 0 to = ta t > 0 ti > to > ta if tr = (ti + to)/2 if to = 0 t = t1 )( )}2/).{(.. tatoh tatoticpl t − −+ =  (5) when there is no heating to = ta, after ti temperature is present, the temperature of the to will continue to rise and stop after stability. starting from increasing to to stop time can be calculated by equation (5); the temperature of this to will continue to rise following the change in variables described above. the energy absorbed by the fluid in the gap will decrease, considering the object's volume decreases with time. q = mf.cf.dt (6) please note that the specific heat depends on the porosity of the material. the equation can be made as follows, cpm = ϕcf + (1-ϕ)cs (7) the specific heat of porosity of solid objects can be made as follows: cs = φcw + (1 φ) cp (8) equation (8) substitutes to equation (7) will become cpm = cp + ϕ (cf – cp) + φ (1 – ϕ)(cw – cp) (9) this cpm value continually changes because the water contained in the object evaporates, whereas cf is considered unchanged because the temperature change is not too high. the density also depends on the material porosity ρpm = ϕ.ρf + (1 – ϕ)ρs (10) the density of solids is, ρs = φ.ρw + (1 – φ)ρp (11) equation (11) is entered into equation (10), then it will be: ρpm = ρp + ϕ (ρf – ρp) + φ (1 – ϕ)( ρw – ρp) (12) the porosity of the media is considered unchanged, but the solid object's porosity depends on time. the longer the porosity decreases so the above equation will change. the change in porosity of a solid body depends on the speed of change in porosity. an equation can be made as follows: dφ = vφ.dt (φi – φ(pin)) = vφ.(ti – to) φ(pin) = φi vφ t. (13) reducing the material's porosity depends on the speed of evaporation of the liquid contained in a solid body. the higher the temperature, the faster the evaporation of water. so, the reduction in porosity of a solid object can be calculated by the equation: (φ)n+1 = (φ)n – a.(φ)nb (φ)n+2 = (φ)n+1 – a.(φ)n+1b (14) reduction of porosity of material can be calculated by the equation: unsteady heat conduction on the porous media in the gap with heater from below 50 (ϕ)n+1 = (ϕ)n – c(φ)nd (ϕ)n+2 = (ϕ)n+1 – c(φ)n+1d (15) with the known reduction of porosity of solid objects, the thickness of porosity of the material can be calculated by the equation: l = 𝐿𝑝 (1−∅)(1−𝜑) (16) from the elaboration of these formulas, it is known that the porosity of a single material and the porosity of the media stack can affect the value of l (thickness). it should be noted that the drying of agricultural products is very different from that of non-agricultural products. in the drying process, water evaporation occurs, which causes the cloves to shrink so that the volume decreases and the porosity in the clove decreases. then this causes a reduction in the porosity of the clove pile because the stacked cloves are more tightly arranged so that the air gap narrows. 3 results and discussions the simulation conditions can be arbitrary, but the example here is made with the following conditions: the initial thickness of the porous object is 3 cm. the average rate of decline in the porosity of solids is made a = 0.01 and b = 3. the average rate of decrease in the porosity value of the total object is c = 0.002 and d = 2.5; 3; 3.5. a reduction in average thickness is made. the final temperature at the top of the object depends on the simulation results. the total time required for the drying process depends on the simulation. the constant temperature at the bottom of the porosity material of 70° c. the thermal conductivity of solid materials varies according to the reduced water content in them. the value of the heat conductivity of porous materials varies according to the conductivity of other materials. the effect of the thickness of a porous object on its density, from figure 3, can be seen that the thicker the object, the smaller the density. due to the heating of the porous object and the vaporized tone, shrinkage occurs, resulting in the density decreases. the thickness of the material's porosity will affect the specific heat; as shown in figure 4, the thicker the porous object, the greater the specific heat, but the thicker the specific heat decreases at a certain thickness. figure 2. the effect of solid material porosity on material thickness figure 3. the effect of solid material porosity on density dewanti et al. (2022). international journal of engineering materials and manufacture, 7(2), 47-53 51 figure 4. the effect of the thickness of the porosity of the material on the specific heat thermal conductivity for objects whose arrangement is considered parallel is influenced by the thickness of the material's porosity; as shown in figure 5, the thicker the object, the greater the thermal conductivity. still, the thicker the thermal conductivity will be at a certain thickness, and the line is not linear. the amount of temperature on the upper surface of a porous object is influenced by the object's thickness. as shown in figure 6 shows, the thinner the object, the higher the temperature. the relationship between the object's thickness and the temperature is not linear, approaching a hyperbola. the object's thickness will affect the temperature changes on the object's surface, as shown in figure 7; the thicker the object, the longer the time needed for temperature changes. the relationship between the object's thickness with temperature changes is not linear. figure 5. the effect of solid material porosity on combined thermal conductivity figure 6. the effect of material porosity on the temperature at the top surface of the material unsteady heat conduction on the porous media in the gap with heater from below 52 figure 7. the effect of material porosity on time for temperature change (s) figure 8. total time required to reduce material the thickness of the object influences the shrinkage time of the object. as shown in figure 8, the smaller the object, the longer it takes to shrink. the relationship between the thickness of the object and the time required for shrinkage is not linear. 4 conclusions based on the research and simulation, the following conclusions were down. 1. the porosity of the material (cloves) and the porosity of the clove pile can be used to determine the thickness of the pile during drying process 2. the porosity of the material affects the density, specific heat, heat conductivity, surface temperature of the pile, changes in the surface temperature of the pile, and changes in time during drying process references adrian, bejan. 2013. convection heat transfer. fourth edi. north carolina: john wiley & sons. bennai, fares, kamilia abahri, rafik belarbi, and abdelkader tahakourt. 2018. "convective and conductive thermal homogenization for non-saturated porous building materials application on the thermal conductivity tensor." thermal science 22(6parta):2367–78. doi: 10.2298/tsci160330262b. deng, zilong, xiangdong liu, yongping huang, chengbin zhang, and yongping chen. 2017. "heat conduction in porous media characterized by fractal geometry." energies 10(8). doi: 10.3390/en10081230. evgeny skripkin. 2015. "effective thermal conductivity of porous media: an integrated approach." university of calgary. florez, j. p. m., g. g. v. nuernberg, m. b. h. mantelli, r. s. m. almeida, and a. n. klein. 2011. "effective thermal conductivity of two-dimensional porous media." pp. 61–66 in international heat pipe symposium. taipei, taiwan. ghanbarian, behzad, and hugh daigle. 2016. "thermal conductivity in porous media: percolation-based effectivedewanti et al. (2022). international journal of engineering materials and manufacture, 7(2), 47-53 53 medium approximation." water resources research 52(1):295–314. doi: 10.1002/2015wr017236. gori, f., and s. corasaniti. 2004. "theoretical prediction of the thermal conductivity and temperature variation inside mars soil analogues." planetary and space science 52(1–3):91–99. doi: 10.1016/j.pss.2003.08.009. henriksen, jan georg. 2013. "adsorptive hydrogen storage : experimental investigations on thermal conductivity in porous media." norwegian university of science and technology. kou, jianlong, yang liu, fengmin wu, jintu fan, hangjun lu, and yousheng xu. 2009. "fractal analysis of effective thermal conductivity for three-phase (unsaturated) porous media." journal of applied physics 106(5):1–7. doi: 10.1063/1.3204479. kreith, frank., manglik raj m., and bohn mark s. 2011. principles of heat transfer. 7th ed. edited by h. gowans and t. altieri. stamford usa: cengage learning. salati, hana. 2014. "experimental and numerical investigation of mass transport in porous media." eastern mediterranean university. telles, a. silva, and g. massarani. 1974. “heat conduction in a porous medium.” revista brasileira de física 4(2):249–62. yang, c., and a. nakayama. 2010. "a synthesis of tortuosity and dispersion in effective thermal conductivity of porous media." international journal of heat and mass transfer 53(15–16):3222–30. doi: 10.1016/j.ijheatmasstransfer.2010.03.004. international journal of engineering materials and manufacture 1 department of manufacturing and materials engineering, kulliyyah of engineering, international islamic university malaysia international journal of engineering materials and manufacture (2021) 6(3) 163-169 https://doi.org/10.26776/ijemm.06.03.2021.07 f. t. zohra, m. h. akanda and b. asiabanpour ingram school of engineering texas state university san marcos, tx 78666 usa e-mail: ba13@txtstate.edu reference: zohra et al. (2021). the effect of macroscopic and microscopic patterns of stainless surface on the efficiency of dropwise condensation and precipitation. international journal of engineering materials and manufacture, 6(3), 163-169. the effect of macroscopic and microscopic patterns of stainless steel surface on the efficiency of dropwise condensation and precipitation fatema tuz zohra, md muzaffer hosen akanda and bahram asiabanpour received: 28 february 2021 accepted: 29 april 2021 published: 15 july 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract atmospheric water generator (awg) technologies are considered a potential new source of freshwater. thermoelectric (tec) dehumidifiers are one of this technology where it uses the peltier effect to create a heat flux at the junction of two different materials. this device is well known for its thermoelectric cooling application, from as small as portable beverage coolers to as big as submarines. the problems of using this device are ice buildup and relatively low efficiency. if the surface of the material can be engineered in a way that the dropwise condensation, as well as precipitation from the cooling plate, is enhanced, it is possible to maximize the efficiency of tec-driven awg with minimum energy consumption. this study investigates the effects of macroscopic (bump/dent, patterns that are visible to the human eye) and microscopic patterns (surface finish, quality, grain distribution, etc. visible under a microscope) on industry-grade stainless (ss) surfaces on dropwise condensation and precipitation. the surface contact angle is considered here to understand the hydrophobic/hydrophilic properties of the surfaces before and after applying hydrophobic coating under constant ambient conditions. better droplet nucleation and quicker precipitation have been observed on the surfaces after treating a hydrophilic and hydrophobic surface with hydrophobic spray. it can be inferred that even though the initial surface property of the two samples were different, it was possible to achieve similar level of super hydrophobicity after applying the spray. this proves that surfaces can be modified with appropriate treatment to achieve desired properties. keywords: dropwise condensation, hydrophobic and hydrophilic surface, macroscopic pattern, microscopic pattern. 1 introduction for dropwise condensation to occur, a droplet has to nucleate, grow, merge with surrounding droplets, and finally detach from the surface leaving space for more droplet accumulation (1)(2). the factors that affect this condensation process are many, such as surrounding temperature and relative humidity, surface property (surface energy, contact angles), angle of tilt of the surface relative to gravity, surface chemistry, groove geometry to aid the droplet motion (3), etc. hydrophilic surfaces are the ones that attract water and helps wetting surfaces and the hydrophobic ones repel water so the surface becomes self-cleaning and non-adhesive to water. the contact angle is a useful measure to identify hydrophilic or hydrophobic surfaces by an instrument called a goniometer. the angle of contact between the dispersed liquid drops and the surface indicates this particular surface property as shown in fig. 1 (a) (4). hence, a surface needs to possess the perfect property based on the application. for example, during dropwise condensation, a surface must be hydrophilic enough to be able to attract moisture to initiate droplet formation but hydrophobic enough so that it leaves the surface quickly to leave space for new droplet formation. while the microscopic structure is responsible for a surface to be either hydrophilic or hydrophobic, both the micro and the macroscopic texture (bump, dent, groove, etc. that are visible to the human eye without any microscope) on a surface can be helpful to guide the coalescence and release of the droplets with the aid of gravity (5). the presence of the ripples (fig. 1 (c), (d)) creates geometric confinement, and thus condensed droplets follow the orientation of textured features as shown in fig. 1 (b). numerous studies have been conducted to determine the effect of both chemical and geometric patterns on wetting characteristics and the motion of condensed droplets positioned horizontally. stainless steel (ss), an ironbased alloy is one of the most commonly used materials in a diverse industry because of its superior physical and the effect of macroscopic and microscopic patterns of stainless surface on the efficiency of dropwise condensation 164 mechanical properties as well as excellent anti-bacterial and corrosion resisting qualities (6)(7)(8). this metal is often used as a substrate to create either super hydrophilic or superhydrophobic surfaces based on the application requirements (8). this surface property depends somewhat on the surface finish by manufacturers and is usually found hydrophilic. different procedures, such as plasma, laser, physical & chemical etching, machining, and coatings, etc. are used to alter the wettability of ss to obtain desired properties. aisi 304 (also known as sae 304) ss has the composition of different elements (9) as shown in fig. 2. contact angle and wettability are proven to be impacted greatly by a wide range of roughness introduced to the substrate, such as rain resistance porous clothing (10)(11)(12)(13). other studies show that the wetting properties of stainless steel (ss) plates treated with atmospheric pressure plasma (app) using three different parameters (gap distance, nozzle scan velocity, pass number) can contribute to an improvement of wettability and/or adhesion properties of the surface (14). biphilic surfacea surface topography of a combination of hydrophobic patterns on hydrophilic structures has been developed and proved to be useful for enhancing dropwise condensation (fig. 3 (a-d)) with long-term functionality and possible for large scale production (15). a combination of the hydrophobic surface with super hydrophilic grooves on stainless steel showed better condensation heat transfer than each of them separately (fig. 3(e)) (16). this hybrid surface showed effective control of droplet sizes with an optimum grid spacing of a super hydrophilic network. figure 1: schematic diagram representing (a) water contact angle on hydrophilic, hydrophobic, and superhydrophobic surfaces (4). (b) a proposed mechanism that could explain the droplet relaxation on samples textured with ripples and fixed on vertical support. (c) afm scan (size: 10 x 10 μm2) of ripples replicated at 75% on polycarbonate. (d) a corresponding height profile of the afm scan is presented in (c). source for (b), (c), (d) (5). figure 2: composition of stainless steel (9). figure 3: the comparison of the time evolution of condensation process (a-d) on hydrophobic (left), 2mm biphilic (center), and hydrophilic (right) regions. the images are taken every 10 min. the biphilic substrate shows better droplet nucleation and removal throughout the experiment (15). (e) growth, movement, and sweeping of droplets on hydrophobic ss surface with super hydrophilic grooves. zohra et al. (2021): international journal of engineering materials and manufacture, 6(3), 163-169. 165 2 experimental procedures in this work, we collected industry-grade ss samples that are already being mass-manufactured with diverse patterns (with biggest bumps to smallest) and surface finish and investigated the surface wettability with precipitation experiment. the as-received samples (3” x 3”) were at first cleaned with isopropanol to remove any contamination and visually observed with the help of the naked eye and optical microscope. contact angles were measured using a goniometer and dropwise condensation and precipitation experiments were conducted using a humidifier. the stainless-steel plates were held at a 30° angle to the gravity and 90° to the incoming mist to ensure the maximum amount of mist capture (fig. 4). photographs and videos were taken for future reference during analysis. after this first step, the most hydrophilic and the most hydrophobic samples were identified. in the second stage, these two samples were used to carry out the further experiment. a commercial-grade hydrophobic spray is used to coat these samples instead of any expensive machining or chemical etching and similar procedures were carried out as in the first step. figure 4: experimental setup for condensation, droplet growth, and precipitation. 3 results 3.1 step – 1: in this step, the samples are cleaned and observed under an optical microscope, contact angles were measured, and finally, a precipitation experiment was done using the warm mist from a commercial humidifier. 3.1.1 visual examination the photographs of ss samples in as-received condition, enlarged view of a specific section of the samples, photographed under the optical microscope on the scale of 10 μm, and photographs of measured contact angle of each sample by goniometer with 5 μl droplet are shown in fig. 5. these samples were randomly chosen and organized from the biggest bump two no bump. sample 1 having the biggest and highest diamond-shaped bump to sample 8 that has no macroscopic bump at all. each sample was cleaned with isopropanol and let dry for 30 minutes before use. according to the manufacturer, all the samples had a ‘satin’ surface finish which is a general-purpose bright polish commonly used for architectural applications. for samples 1 to 5, macroscopic patterns are not visible under microscope view since the scale is smaller than each bump. from samples 6 to 8, the microscopic view shows the surface structures and finishes more clearly and distinctively. as shown in this figure, sample-4 having a squareshaped microscopic pattern shows the highest contact angle of 102°, and sample-7 having a tiny oval shaped microscopic pattern shows the lowest contact angle of approximately 38°. for sample-1, the macroscopic bump was visible even under the goniometer, so the surface on which the droplet is sitting doesn't look fairly flat. for sample3, having a circular pyramid-shaped bond on the surface, it was impossible for putting a droplet steady on the surface to be able to measure its exact contact angle. but visual inspection of the droplet shape and non-adhesive nature of the droplet to the surface proves that it is hydrophobic. the effect of macroscopic and microscopic patterns of stainless surface on the efficiency of dropwise condensation 166 figure 5: photograph and enlarged view of the samples, microscopic view, measured contact angle. all the microscopic view has same scale of 10 μm. except for the contact angles that were screen shot directly in computer, all the photographs were taken with the camera of samsung note 2. 3.1.2 precipitation each sample was exposed to warm humidifying mist to acquire condensation, droplet formation, and precipitation under a constant ambient condition (temperature 22° c, relative humidity = 30%). samples that are categorized as hydrophobic (samples1, 3, 4), tends to form droplets and dissipated more often than the hydrophilic ones (samples 2, 5-8). photographs of time-lapse during this experiment for samples 4 (hydrophobic) & 7 (hydrophilic) are presented in fig. 6 for comparison. hydrophilic surfaces tend to form a thin water film on the surface, thus preventing dry space for new droplet nucleation. upon close observation, droplets are seen to be formed along with the macroscopic pattern (red diamond in fig. 6) of the hydrophobic surface (sample-4) and released at once when the surface energy becomes less than the gravitational pull. droplets formed on the hydrophilic surface create a thin film together wetting the surface in a circular pattern (blue circle in fig. 6). figure 6: the comparison of time evolution on the droplet growth, movement, and sweeping process on hydrophobic and hydrophilic ss surface with different macro patterns. all the photographs were taken with the camera of samsung note 2. zohra et al. (2021): international journal of engineering materials and manufacture, 6(3), 163-169. 167 3.2 step – 2: in this step, samples with two extreme contact angles representing hydrophobic (sample-4) and hydrophilic (sample7) are coated with a commercially available superhydrophobic spray (rust-oleum never wet step 2 coat) for further experiments. this coating system creates a moisture repelling barrier on a variety of substrates such as metal, wood, aluminum, galvanized metal, pvc, concrete, masonry, asphalt, vinyl siding, fiberglass, canvas, most plastics and more (17). it also gives the surface a haze finish that slightly alters the color. the sample surfaces are washed with isopropanol to clean any contamination and thoroughly dried. three coats are applied and let dry for 30 minutes according to the instruction before the contact angle measurement and precipitation experiment is performed. after these experiments, observations under the optical microscope were done for a better understanding of the droplet formation. 3.3 results after hydrophobic coating after the samples were treated with a hydrophobic coating, a slight change of colour on the ss surface was visible because of the dried white coloured spray (fig. 7). figure 7: change of color of the surfaces after applying the hydrophobic spray. sample-4 (a) before, (b) after, and sample-7 (c) before, (d) after. the surfaces showed similar droplet growth, coalescence, and release from the surface which is different than before the coat. fig. 8 shows these contrasts, the microscopic view of the sample, and their contact angles. both the surfaces look the same and similar shapes of droplets are found when inspected under a microscope. the contact angle measured for both surfaces is very close and represents a superhydrophobic surface. the adhesion to the surface was so difficult that the droplet size had to be increased from 5 to 15 μl to be able to release it on the surface. because of this superhydrophobic nature, when subjected to the warm mist in the precipitation experiment (at 30° angle to the gravity and perpendicular to the mist incoming direction), droplets started to fall once they were almost the size of 5 μl. a much smaller droplet precipitation occurred than that in step-1. the self-cleaning property of the surface improved greatly in the sense that the droplets did not adhere to the surface to form a thin film of water and also macroscopic pattern did not have any effect at this point for guiding the droplets to the bottom of the plate as it did in step-1 for sample-4. the effect of macroscopic and microscopic patterns of stainless surface on the efficiency of dropwise condensation 168 figure 8: samples showing photographs of the difference in the wetting of surface before/after applying the hydrophobic spray, droplets under microscope, and contact angle with 15 μl. 4 discussion and conclusions many researchers have studied microscopic patterns and their effects on the hydrophobicity and hydrophilicity of the surfaces. however, not much has been done on the macro geometries and patterns and their integration with micro or nano roughness and material properties. additionally, the dynamic process (time-based) of awg may show different results when the system runs long-term. our result of observing super hydrophobic property on the samples after treating with hydrophobic spray are consistent with the findings of many previous literatures such as (1)(8)(18) that a superhydrophobic surface enhances both dropwise condensation and condensate droplet departure from that surface. since the drops in this condensation process are discreet and continually formed and released from the surface, the surface itself gets exposure to facilitate new droplet formation. whereas, in the filmwise condensation process, the water film always covering the surface acts as a thermal resistance to facilitate the condensation process. surfaces with this super hydrophobic property also possess some other useful properties such as self-cleaning, anti-icing, wear resistance of the material, etc. although the coating itself can be easily removed or wiped off clean if needed. future research in this area includes systematic categorization of patterns and geometries for the macro features, variation of materials, dynamic droplet size, and computational fluid dynamics to study the flow and heat distribution of the droplet formation over time. acknowledgement this work was completed with funding from the us department of agriculture (grant # 2016-38422-25540). the authors would like to thank the usda and texas state university for providing funding and access to both infrastructure and laboratories. the sponsors are not responsible for the content and accuracy of this article. the authors declare that there is no conflict of interest regarding the publication of this paper. reference 1. dong j, dong h, jin y, sun l, ye s, dong j, et al. nanograssed micro-v-groove architectures for continuous dropwise condensation and droplet directional movement exploiting such multiscale coupling effects can help us design optimal con-densation surfaces for high performances of phase-change cooling and. adv mater interfaces [internet]. 2018 [cited 2021 apr 10]; available from: https://doi.org/10.1002/admi.201800202. zohra et al. (2021): international journal of engineering materials and manufacture, 6(3), 163-169. 169 2. chen x, wu j, ma r, hua m, koratkar n, yao s, et al. nanograssed micropyramidal architectures for continuous dropwise condensation. adv funct mater [internet]. 2011 [cited 2021 apr 10];21:4617–23. available from: www.materialsviews.com 3. zhong y, jacobi am, georgiadis jg. effects of surface chemistry and groove geometry on wetting characteristics and droplet motion of water condensate on surfaces with rectangular microgrooves. 2012 [cited 2021 apr 1]; available from: http://dx.doi.org/10.1016/j.ijheatmasstransfer.2012.10.056 4. chieng bw, ibrahim na, daud na, talib za. functionalization of graphene oxide via gamma-ray irradiation for hydrophobic materials. in: synthesis, technology and applications of carbon nanomaterials. elsevier; 2018. p. 177–203. 5. pionnier n, vera j, contraires e, benayoun s, berger r, valette s. the effect of the orientation and the height of periodic sub-micrometric texturing on dropwise condensation. 2018 [cited 2021 mar 23]; available from: https://doi.org/10.1016/j.jcis.2018.04.043 6. gupta rk, anandkumar & b, choubey a, george & rp, ganesh & p, upadhyaya & bn, et al. antibacterial and corrosion studies on nanosecond pulse laser textured 304 l stainless steel surfaces. [cited 2021 apr 1]; available from: https://doi.org/10.1007/s40516-019-00097-9 7. pramanik a, basak ak. stainless steel: microstructure, mechanical properties and methods of application. stainless steel: microstructure, mechanical properties and methods of application. nova science publishers, inc.; 2015. 1–281 p. 8. cremaldi j, bhushan b. fabrication of bioinspired, self-cleaning superliquiphilic/phobic stainless steel using different pathways. j colloid interface sci [internet]. 2018 [cited 2021 mar 21]; available from: https://doi.org/10.1016/j.jcis.2018.02.034 9. sae 304 stainless steel wikipedia [internet]. [cited 2021 apr 1]. available from: https://en.wikipedia.org/wiki/sae_304_stainless_steel 10. marmur a. wetting on hydrophobic rough surfaces: to be heterogeneous or not to be? langmuir. 2003 sep 30;19(20):8343–8. 11. cassie abd, baxter s. wettability of porous surfaces. trans faraday soc. 1944;40:546–51. 12. dettre rh, johnson re. contact angle hysteresis. in: advances in chemistry. 1964. p. 136–44. 13. huerta-murillo d, garcía-girón a, romano jm, cardoso jt, cordovilla f, walker m, et al. wettability modification of laser-fabricated hierarchical surface structures in ti-6al-4v titanium alloy. appl surf sci. 2019 jan 1;463:838–46. 14. kurtuldu f, altuncu e. surface wettability properties of 304 stainless steel treated by atmospheric-pressure plasma system. in: 4th international symposium on innovative technologies in engineering and science. 2016. p. 1350–9. 15. alizadeh-birjandi e, alshehri a, kavehpour hp. condensation on surfaces with biphilic topography: experiment and modeling. front mech eng. 2019 jun 25;5. 16. ji x, zhou d, dai c, xu j. dropwise condensation heat transfer on superhydrophilic-hydrophobic network hybrid surface. int j heat mass transf. 2019 apr 1;132:52–67. 17. data t. rust-oleum industrial brands neverwet ® industrial gallons. 18. pandey s. dropwise and filmwise condensation. int j sci eng res [internet]. 2012 [cited 2021 apr 19];3(4). available from: http://www.ijser.org. international journal of engineering materials and manufacture (2022) 7(4) 103-110 https://doi.org/10.26776/ijemm.07.04.2022.03 md. nur salam 1 , mohammad farhan hasan 2 , md rokonuzzaman 3 and md a rahman 1 1 department of nuclear science and engineering military institute of science and technology, dhaka, bangladesh 2 department of process safety and environmental engineering otto-von-guericke university, magdeburg, germany 3 department of nuclear engineering manchester university, united kingdom e-mail: 1016280008@student.mist.ac.bd reference: salam, m. n., hasan, m. f., rokonuzzaman, m. and rahman, m. a. (2022). an analysis of water characteristics of shiddhirganj 210mw steam power plant, sirajganj 225mw combined cycle power plants and rooppur 2400mw nuclear power plant in bangladesh: a comparative study of power plant grade water. international journal of engineering materials and manufacture, 7(4), 103-110. an analysis of water characteristics of shiddhirganj 210mw steam power plant, sirajganj 225mw combined cycle power plants and rooppur 2400mw nuclear power plant in bangladesh: a comparative study of power plant grade water md. nur salam, mohammad farhan hasan, md rokonuzzaman and md a rahman received: 31 august 2022 accepted: 06 october 2022 published: 25 october 2022 publisher: deer hill publications © 2022 the author(s) creative commons: cc by 4.0 abstract water quality has long been an important part of the operation of nuclear and thermal power plants. water is used as a working and cooling fluid in power plants. the quality of source water to be used in the power plants after treatment should conform to the prescribed values of physico-chemical properties like ph, ec, tds, alkalinity, hardness, presence of chloride content, silica, and heavy metals as recommended by technical guidelines. to analyze the water characteristics, water samples were collected from various sources. two river water samples and a groundwater sample (marked as pp1, pp2, and npp site) were tested to determine the water properties. the physicochemical properties of the water samples were determined using various analytical tests. heavy metals were also investigated using the atomic absorption spectrophotometric (aas) process. the physico-chemical properties of investigated samples were so good as to the recommended values of the world health organization (who), united states of public health (usph), and bangladesh environmental department. but the values were very far from the recommended values for thermal power plants operation. so, it needs to treat to use in the boilers. gravitation, carbon filtration, ion exchange method, and reverse osmosis (ro) are good ways to treat the water before use in power plants. the padma river water is better than the other two samples when the physico-chemical characteristics of the sample waters were analyzed to the prescribed levels for the boiler water of a thermal power plant and the secondary water circuit of a third-generation nuclear pwr reactor. the aim of this work is to explore the difference between the source water quality parameters values and those of the recommended values of technical guidelines. to minimize the water treatment cost, a new site for the installation of a power plant project in bangladesh can be advocated depending on the availability of good quality water. keywords: water quality, thermal power plant, nuclear power plant, analysis of water. 1 introduction in bangladesh, 133 power plants are installed around the country. the present power generation capacity per capita in the country is 300 kwh. to ensure proper energy, two nuclear power plants of capacity (2×1200mw) are in the process of installation and extensive civil work is going on [1-2]. water quality has long been an important factor in the operation of thermal and nuclear power plants [3-4]. a proper water chemistry program is essential for the safe operation of power plants. it guarantees consistency with the design's assumptions and intents regarding the key plant structures, systems, and components. sufficient information/data on water characteristics of the thermal power plants (shiddhirganj 210 mw and sirajganj 135 mw northwest power generation company bangladesh limited (nwpgcbl) are not available in bangladesh. this work has been undertaken to analyze the water characteristics in salam et al. (2022): international journal of engineering materials and manufacture, 7(4), 103-110 104 conventional type thermal and under construction rooppur nuclear power plants (rnpp). for the safe and reliable operation of thermal and nuclear power plants, difficulties with corrosion and the chemistry of water coolant play an important role [5-7] and the water regime for commercial water-cooled components must be improved to have the recommended value of water quality parameters, such as turbidity, ph, electrical conductivity (ec), total hardness (th) and presence of heavy metals proved to be satisfactory. [8-9]. 2 material and method 2.1 sample collection the sample was collected from different source waters. to analyze the water characteristics two river waters and a groundwater sample were analyzed to study the water characteristics. the water sample was collected from the river of shitalakkha near shiddhirganj 210 mw steam turbine power station (marked as pp1) and was analyzed in their laboratory. the groundwater sample sirajganj 225mw combined cycle power plant near jamuna river (marked as pp2) at sirajganj district was analyzed by the nwpgcbl lab. another surface water sample was collected from the padma river near the under-construction roopppur nuclear power plant (npp) site at rooppur, pabna, bangladesh, and analyzed in environmental engineering laboratory, mist, dhaka. 2.2 sample analysis the quality of water of various source water was analyzed and compared with the standard values of boiler waters of conventional type thermal power plants and secondary circuit of vver-1200, pwr reactor. a digital ph meter (hanna instrument ht 2002-0, s/n co316002) was used to calculate the ph, digital tds and ec meters (hanna -2003-02, s/n: co1271a1) were used to measure total dissolved solids (tds) and electrical conductivity (ec), respectively. heavy metals were estimated by the aas process and the chemical properties of the samples of waters were determined by various analytical methods [10-12]. 3 water quality parameters 3.3.1 ph the ph meter first needs to be calibrated, setting the temperature control knob to 25°c when choosing the ph mode. the ph meter was calibrated twice. a clean 400 ml beaker was used to hold the 250 ml of the sample while the ph meter was submerged within. the ph of the solution is calculated correctly and displayed [13–14]. ph, which is defined as the negative logarithm of the hydrogen-ion concentration, is the most common way to express the hydrogen-ion concentration. ph= -log10[h+] 3.3.2 electrical conductivity (ec), total dissolve solids (tds), salinity and temperature first, distilled water was used to clean the electrode on the conductivity meter. the electrode was inserted into a 400 ml beaker containing a 250 ml sample, and the beaker was then filled with water while signal counting was performed. using a ph and ec meter, measurements of ec, tds, salinity, and temperature were taken. 3.3.4 atomic absorption spectrophotometer (aas) atomic absorption by using the absorption of optical radiation (light) by free atoms in the gaseous or liquid form, spectrometry is a spectro-analytical method for the qualitative and quantitative determination of chemical elements as shown in figure 1. the method makes use of absorption spectrometry to evaluate the analysis concentration in a sample. the beer-lambert law is used to identify the relationship between the observed absorbance and, consequently, the analyte concentration when standards with known analytical content are not available. in fact, by absorbing a certain amount of energy, the electrons of the atoms in the atomizer are frequently moved to higher orbitals (exciting state) for a brief amount of time (nanoseconds) (radiation of a given wavelength). this level of energy, or wavelength, is only available during a certain electron transfer in a specific element. since each wavelength typically corresponds to only one element, the length of an optical system is only a few picometers (pm), giving the method its elemental selectivity. a detector is used to monitor the radiation flux with and without a sample inside the atomizer, and beer is then used to translate the difference between the two readings (the absorbance) to analyte concentration or mass. lambert law [15-17]. figure 1: schematic diagram of atomic absorption experiment (adapted) [17]. an analysis of water characteristics of power plant in bangladesh: a comparative study of power plant grade water 105 3.4 analytical techniques 3.4.1 total hardness (th) in a conical flask, 10 ml of the sample solution and 1 ml of the ammonia buffer solution were added, followed by 23 drops of the erithochrome black-t (ebt) indicator, which caused the solution to turn wine red. the volume was then determined by titration with 0.01 m edta solution until the wine-red hue changed to blue, indicating the point at which the titration was complete. th (mg/l) = ml edta used x 1000 / ml sample obtained is the formula. 3.4.2 total alkalinity (ta) 20 ml of the sample was taken, and then 2-3 drops of the phenolphthalein indicator were added, titrated, and added until a pink hue was seen. the permanent pink tint was then eliminated by titrating the solution with 0.02n sulfuric acid. this shows the alkalinity of phenolphthalein. the solution in which phenolphthalein had just been identified was now mixed with a couple of drops of methyl orange indicator. sulfuric acid 0.02n was then added to the solution and titrated. pink replaced the previous yellow shade. the pink color is back, which denotes ta. ta (as caco3, mg/l) is calculated using the following formula: (u+v) n100050 / ml sample collected where; u=volume of h2so4 used with phenolphthalein indicator v=volume of h2so4 used with methyl orange indicator (u+v) = total vol. of h2so4 used with both indicators n=normality of h2so4; 1 g of equivalent acid = 1g of equivalent caco3 3.4.3 chloride content a 20 ml sample was collected in a conical flask, and 1 ml of a 5% k2cro4 solution was placed as an indicator. the solution was titrated with 0.02n agno3 solution until a permanent brick red color emerged, which is the indicator of the endpoint. formula: chloride (mg/l) = (a-b) n-35.51000/ml sample taken where; a= volume of agno3 used for sample titration b= volume of agno3 used for blank titration 1 g eq. of agno3 = 1 g eq. cl = 35.5 g cl 4 result and discussion 4.1 experimental result of the water sources we present all the experimental observations obtained in the present analysis are presented in tabular form, respective to the individual sample used in the current experiments. the water qualities of the source waters and the recommended values of boiler water of thermal power plant and secondary circuit of vver-1200 pwr reactor [1820] are shown in table 1. the deviations in the result are briefly discussed below. table 1: raw water quality parameter of pp1, pp2 & npp site with the standard. 4.2 discussion on experimental result water quality metrics from the source waters, including ph, electrical conductivity (ec), total dissolved solids (tds), chloride content, total hardness (th), alkalinity, silica, and heavy metals, were carefully measured both before and after the treatment. then, we selected the ideal circumstances for the best source of water to be used in the production of electricity. 4.2.1 ph analysis a sample's ph value of any liquids indicates whether it is acidic or basic. demineralized (dm) and purified water should have a ph of 7, which is neutral. water has a ph between 7 and >7, falls between 7, and is acidic. bangladesh's specified ph range for drinking water quality is 6.5 to 8.5. the ph level will be lower the more hydrogen no. parameter unit pp1 (river water) pp2 (ground water) standard value of dm water npp site standard value pwr secondary circuit 1 ph 7.34 6.51 9.0-9.5 7.53 4.5-10 2 electrical conductivity (ec) at 25ºc µs/cm 681 433 ≤ 1.5 429 00 3 tds ppm 312 404 00 212 00 4 chloride ppm 11 7 < 0.1 10.6 < 0.1 5 total hardness ppm 3.6 248 00 143 00 6 total alkalinity ppm 5.1 10 00 0.03 00 7 silica (sio2) ppm 28.8 10 ≤ 0.03 15 --- salam et al. (2022): international journal of engineering materials and manufacture, 7(4), 103-110 106 ions are contained in the solution. like this, a solution's ph value will increase the more hydroxyl ions are present in the solution. the standard range of ph of boiler water in the thermal power plant is from 9.0-9.5 and in the nuclear vver pwr reactor, the value is from 4.5-10. the ph values of the different power plants are graphically presented in figure 2 along with the recommended values. are shown in table 1. water had an average ph of 8.02. surface water has a standard value that falls between 6.5 and 8.5. the study area's ph was excellent and suited for both thermal and nuclear power facilities. the secondary circuit's suggested value is 4.5–10. [21-23]. figure 2: analysis of ph quality gap between raw water and dm water. 4.2.2 electrical conductivity pure water is a poor conductor of electricity. electrical conductivity depends on the concentration of dissolved salt in water. it can be dissolved most of the salts are soluble in water. the acceptable level of conductivity in drinking water recommended by the united states public health (usph) is 300 micro-siemens/cm. the presence of different salts in the water body and oh and h + ions enhance conductivity. the comparison of ec among the source water of thermal power plants and the quality of npp water has shown in table 1 and figure 3 with standard values [2425]. from the gained values it is executed that in terms of electrical conductivity of the source waters required chemical treatment to use in the power plant grade water. ion exchange method is used to remove ions, present in the water body and produce dm water. the ec of dm water must be zero. figure 3: analysis ec gap between raw water and dm water 4.2.3. total dissolved solids (tds) the inorganic salts and trace amounts of organic materials found in water bodies are explained by total dissolved solids (tds). the primary components are typically hydrogen, carbonate sulfate, chloride, and nitrate anions, as well as calcium, magnesium, sodium, and potassium cations and anions. particles that are completely dissolved are not charged. in a solution, it might be in a colloidal form. table 1 displays the tds values for several samples. the world health organization (who), united states public health (usph), and bangladesh all have standard tds standards for drinking water quality that is 1000, 500, and 500 ppm respectively as shown in figure 4 [26-27]. 7.34 6.52 7.53 6.5 9 4.5 8.5 9.5 10 0 2 4 6 8 10 12 pp1(river water) pp2(ground water) npp site bangladeshi standard dm plant standard secondary circuit water quality p h sample name 600 433 429 1.5 1.5 1.5 0 100 200 300 400 500 600 pp1 pp2 npp site pp1 standard pp2 standard npp standard e c i n µ s / c m sample name an analysis of water characteristics of power plant in bangladesh: a comparative study of power plant grade water 107 figure 4: analysis of tds gap between raw water and dm water. the tds values of three source glasses of water were found in the range of 212 ppm to 404 ppm. the permissible limit of tds is 500 ppm for potable water. for dm water tds must be zero. otherwise, the ions will make corrosion and will produce damage to the power plant instruments. these ions are removed from the water body by using ion exchange methods. 4.2.4 chloride content chloride is a sign of water's salinity. significantly chloride-rich surface water suggests a greater diversity of marine life. chloride is a conservative characteristic from an environmental aspect and can be used as an indicator of contamination coming from primary sources like industrial and municipal outputs in natural waters. the value of chloride contents in pp1, pp2, and npp sites 11, 7, and 10.6 ppm respectively as shown in figure 5 where the recommended values of chloride content in dm water is < 0.1 ppm. figure 5: analysis of chloride content between raw water and dm water. 4.2.5 total hardness (th) caco3 in ppm has been computed as the samples' hardness. divalent metallic cations, of which ca & mg are the most prevalent in pp2 water, are the cause of hardness. the lowest value of th was found at 3.6 ppm in pp1 and the highest level at 248 in pp2. so, the result shows that the pp1 sample is the best quality according to the parameter. the dm plant refers the th to 00 ppm for power generation. the standard values of total hardness of drinking water quality in bangladesh, the world health organization (who), and the united states public health (usph) are 250, 500, and 500 ppm, respectively [27-28]. however, certain ranges can be delineated, and these are shown in table 2. 312 404 212 1000 500 500 0 0 0 200 400 600 800 1000 t d s i n p p m sample name salam et al. (2022): international journal of engineering materials and manufacture, 7(4), 103-110 108 table 2: total hardness range and the quality of water total hardness (th) range in ppm description 0-40 soft 40-100 moderately hard 100-300 hard 300-500 very hard 500-up extremely hard 4.2.6 alkalinity a water sample is titrated with a standard acid to a predetermined ph to determine alkalinity, which is then recorded as p, m, or t alkalinity. p alkalinity is titrated to ph 8.3, m alkalinity to ph 4.6, and t alkalinity to ph 4.5 using phenolphthalein, methyl orange indicator, and total alkalinity indicator, respectively. the t-alkalinity were found in the sample of pp, pp2, and npp sites were 5.1, 10, and 0.03, respectively. the recommended values of dm plant water are 00 ppm. according to other parameters, it is saying that the source water quality is good to use after simple treatment. 4.2.7 silica (sio2) after silica enters the boiler water, the usual corrosive action increase in boiler instruments and decreases the lifetime of boiler instruments. to decrease the boiler water silica to acceptable levels and then to effect of the condition caused by the silica contamination must be proved recommended limit. the silica found in the source water sample of pp1, pp2, and the npp site were 28.8, 10, and 15 ppm respectively as shown in figure 6 where the dm plant and the secondary circuit require relatively zero. reverse osmosis, carbon filtration, and gravitation are good ways to remove silica from the water body [29-30]. figure 6: analysis of the quality of sio2 between raw water and dm water with standard 4.2.8 heavy metal heavy metals are most of the important parameters for boiler water it makes corrosion with the power plant components and damage to the power plant accessories. so, it is very important to control the heavy metal in boiler water as well as the secondary circuit of npp. after analysis, the heavy metals found in water collected from the source water appear in increasing order given below, co < mn < ni < cd < cr < pb <as < fe iron is typically the element that is most prevalent and abundant in both the earth's crust and its surface. this can be one of the reasons why iron was obtained at the highest levels in water samples especially. a high concentration of iron was observed in water samples. it is well known that the fe presence in the water body is in terms of fe 2+ and fe 3+ ions. to reduce corrosion and make the longevity of power plant boiler instruments, the concentration of heavy metals in dm water must be proved satisfactory [31-32]. the existence of heavy metals in dm water and boiler water must be zero. 0 5 10 15 20 25 30 35 s i o 2 i n p p m sample name an analysis of water characteristics of power plant in bangladesh: a comparative study of power plant grade water 109 5 conclusions the aim of this research work was to detect the physico-chemical characteristics of padma river water at the npp site, shitalakkha river water, and nwpgcl groundwater near the jamuna river. the quality of source waters to be used in the power plants after treatment should conform to the prescribed values of physico-chemical properties like ph, ec, tds, alkalinity, presence of chloride content, silica, and heavy metals as recommended by technical guidelines. the padma river water was found better than the other two samples after analyzing and comparing the physicochemical parameters of samples waters with the recommended values of the secondary water circuit of a thirdgeneration nuclear pwr reactor. padma river water is suggested for secondary circuits for the safe operation of the rooppur nuclear power plant, except for the value of electrical conductivity (ec). to standardize the quality of padma river water, proper water treatment is required, and then padma river water can be used as secondary circuit water. gravitation, reverse osmosis (ro), carbon filtration, and ion exchange method are good ways to treat the raw waters used in thermal power plants. the mission in the incoming days will be to raise the coolant heat, enhance the heat flux, and extend the burnup extension time in the reactor core. corrosion, corrosion product accumulation, and deposition can be liable to an increased risk of fuel failure. more resistant cladding alloys should be used, or the water chemistry should be improved, avoid cladding failures in new conditions in thermal and nuclear power plants. to comprehend the corrosion product behavior process and construct a grand pattern of the physico-chemical system in reactor circuits, more study and research is required. the difference between the source waters quality parameters values and those of the values of technical guidelines, the physico-chemical properties should be as small as possible for the minimization of the water treatment cost. depending on the availability of good quality water new site for the installation of a power plant project in bangladesh can be advocated. acknowledgment the authors would like to express their sincere appreciation to the department of nuclear science and engineering at military institute of science and technology for their unflagging support and encouragement. my sincere appreciation to bangladesh power development board, dhaka for their guidance to make the researcher successful. references [1] b.m. larin, e. n. bushuev, a.b. larin, e. a. karpychev, and a.v. zhadan, “improvement of water treatment at thermal power plants," journal of thermal engineering, vol. 62, no. 4, pp. 286–292, 2015. [2] b. buecker. power plant water chemistry: a practical guide. usa: pennwell books. 1997. [3] l. wei and l. jianfeng, “analysis on control operating conditions of the water chemistry of nuclear power unit,” applied mechanics and materials, vol. 178-181, pp. 553-556, 2012. [4] s. m. sonawane, “effect of wastewater and ash of thermal power station on hydrological features of river tapi at bhusawal district jalgaon maharashtra,” journal of environmental science, toxicology and food technology, vol. 9, no. 7, july, pp. 19-24, 2015. [5] s. vidojkovic, a. onjia, b. matovic, n. grahovac, v. maksimovic and a. nastasovic, “extensive feedwater quality control and monitoring concept for preventing chemistry-related failures of boiler tubes in a subcritical thermal power plant,” applied thermal engineering, vol. 59, pp. 683-694. 2013. [6] l.wei and l. jianfeng, “analysis on control operating conditions of water chemistry of nuclear power unit,” applied mechanics and materials, vol. 178-181, pp. 553-556, 2012. [7] d. zenghui, “design and study of water supply system for supercritical unit boiler in thermal power station”. aip conference proceedings, baoding hebei, china, pp.1-5. 2018 [8] d. lister, shunsuke uchida, “determining water chemistry conditions in nuclear reactor coolants, “journal of nuclear science and technology, vol. 52, no. 4, pp. 451–466, 2015. [9] peavy, h.s. rowe, d.r. and g.tchobanoglou, “environmental engineering” mcgraw-hill inc, new york, 1985. [10] kotz, j.c, treichel, p, & weaver, g.c, “chemistry & chemical reactivity” thomson brooks/cole. isbn 053439597x [11] "world health organization. safe water and global health". who.int. 2008-06-25. http://www.who.int/features/qa/70/en/. retrieved 2010. [12] an international source book, “environmentally sound technology for wastewater and stormwater management” iwa publishing. isbn 1843390086. oclc 49204666. 2002 [13] food and nutrition board, “national academy of sciences. recommended dietary allowances” national research council, reprint and circular series, no. 122. pp. 3–18. 1945. [14] j.m. montogomery, “water treatment principles and design,” consulting new york 75, 2nd edition, 1985. [15] black, a.p. and christman, r.f., “characteristics of colored surface waters”. am. water works assoc., 55: 753. 1963. [16] n.gupta, r.s.khoiyangbam, and n. jain “environmental chemistry”, new dhelhi, january, 2015. salam et al. (2022): international journal of engineering materials and manufacture, 7(4), 103-110 110 [17] s.tsubakizaki, t. wada, t.tokomoto, “water quality control technology for thermal power plants (current situation and future prospects,” mitsubishi heavy industries technical review. vol. 50 no. 3, 2013. [18] v.f. tyapkov, i.yu. chudakova, and o. a. alekseenko, “achieving more reliable operation of turbine generators at nuclear power plants by improving the water chemistry of the generator stator cooling system,” thermal engineering, vol. 58, no. 8, pp. 655–659, 2011. [19] j. b alam, m.r.islam, m. r., muyen, z.; mamun, m. and islam, s. “water quality parameters along rivers.” int. j. environ. sci. tech., vol.no.4 (1). pp. 159-167. 2007. [20] a. k.tripathi, m. k. bhatnagar , p.bhatnagar, n. vyash, “physico-chemical assessment of surface water quality with respect to seasonal variation around amarkantak thermal power plant, chachai, madhya pradesh, india” journal of applied chemistry (iosr-jac).vol 7, no. pp 28-33, 2014. [21] m. adlan, a.h, wan maznah,y. khairun, c.chuah, m.h. shahril, m.noh, “tropical marine phytoplankton assemblages and water quality characteristics associated with thermal discharge from a coastal power station,” journal of natural sciences research. vol.2, no.10, 2012. [22] p.m, nalawade, a.d. bholay, and m. b. mule, “assessment of groundwater and surface water quality indices for heavy metals nearby area of parli thermal power plant,” universal journal of environmental research and technology. volume 2, no.1, pp. 47-51, 2012. [23] md. galal uddin, md. moniruzzaman and mala khan, “evaluation of groundwater quality using ccme water quality index in the rooppur nuclear power plant area, ishwardi, pabna, bangladesh”. american journal of environmental protection, vol. 5, no. 2, pp. 33-43, 2017. [24] r. s. lucy, m. e. huda and s. m. d. islam, “comparative study on physicochemical and biological parameters of water among fish culture and reconstructed pond at jahangirnagar university campus, bangladesh,” j. environ. sci. & natural resources, vol.no. 9(1): pp. 1-7, 2016. [25] abida.b. and harikrishna. “study on the quality of water in some streams of cauvery river,” e-journal of chemistry, vol. no. 5 (2), pp. 377-384. 2008. [26] m. v. ahipathi, and puttaiah, e. t, “ecological characteristics of vrishabhavathi river in bangalore (india),” environmental geology, vol.49, pp. 1217-1222, 2006. [27] q. li, g. wang, yao pi, bo li, and x. yang, “study on standards applicable for primary and secondary water chemical analysis in the third-genaration pwr,” proceedings of the 20th pacific basin nuclear conference 2017. [28] a. v. gavrilov, n. a. prokhorov, and v. g. kritskii, “accounting for environmental aspect in water-chemistry optimization of the second loop of npp with vver,” atomic energy, vol. 124, no. 4, 2018. [29] v.g. asmolova, i.n. gusevb, v.r. kazanskiyb, v.p. povarovb, d.b. statsura, “new generation first-of-the kind unit – vver-1200 design features,” nuclear energy and technology, v3, issue 4, pp. 260-269, 2017. [30] v. f. tyapkov, and s. f. erpyleva, “water chemistry of the secondary circuit at a nuclear power station with a vver power reactor,” thermal engineering, vol. 64, no. 5, pp. 357–36, 2017. [31] h. kawamuraa, y.shodab, t.terachic , y.katsumurad, s.uchidae , t.mizunof, y.muroyag , y.tsuzukih, r.umeharai , h.hiranoj, t.nishimura, “pwr secondary water chemistry guidelines in japan purpose and technical background,” progress in nuclear energy, vol.114, pp.121-137, 2019 [32] iaea-ner2008, water chemistry of wwer nuclear power plants iaea, vienna, 2008. https://www.sciencedirect.com/science/journal/24523038 https://www.sciencedirect.com/science/journal/24523038/3/4 https://www.sciencedirect.com/science/journal/01491970 https://www.sciencedirect.com/science/journal/01491970/114/supp/c international journal of engineering materials and manufacture (2023) 8(1) 13-20 https://doi.org/10.26776/ijemm.08.01.2023.02 s. a. r sharifah nadhirah, j. s. mohamed ali , m. s. i shaik dawood, r. adib hamdani department of mechanical and aerospace engineering, kulliyyah of engineering, international islamic university malaysia. email: jaffar@iium.edu.my reference: sharifah nadhirah, s. a. r., mohamed ali, j. s., shaik dawood, m. s. i., adib hamdani, r. (2023) influence of composite skin on the energy absorption characteristics of an aircraft fuselage. international journal of engineering materials and manufacture, 8(1), 13-20. influence of composite skin on the energy absorption characteristics of an aircraft fuselage s. a. r. sharifah nadhirah, j. s. mohamed ali, m. s. i. shaik dawood, r. adib hamdani received: 08 january 2023 accepted: 12 january 2023 published: 20 january 2023 publisher: deer hill publications © 2023 the author(s) creative commons: cc by 4.0 abstract in aviation history, accidents during landing are more frequent compared to other phases of flight and in most cases the aircraft is forced to make an emergency belly landing when landing gear malfunctions. this study aims to analyse the energy absorption of a typical composite aircraft fuselage section under such crash belly landing. a finite element model of this composite fuselage section was created and analyzed using ls-dyna finite element software and the effects of different composite materials on the energy absorption of fuselage section were studied. four different composite materials that are commonly used in aerospace application were selected for the purpose of the present study namely glass/epoxy, graphite/epoxy, kevlar/epoxy, and boron/epoxy. an impact velocity of 7 m/s against rigid ground was considered. results showed that frames and skin contribute the most in energy absorption while the passenger floor and strut contribute the least. moreover, it was found that fuselage skin made of glass/epoxy absorbed more energy compared to other materials and it had the highest specific energy absorption. keywords: crashworthiness, belly landing, energy absorption, composite materials, ls-dyna 1 introduction in the aircraft design, crashworthiness is a major concern, especially for civil aircraft. crashworthiness is the ability of the aircraft structure to protect passengers from injury during a crash. in aviation history, belly landing crashes have been reported as one of the most frequent accidents. belly landing mainly occurs due to landing gear failure or when pilots forget to deploy the landing gear. there are many risks in performing belly landing as the impact energy can be transferred to the passenger cabin and this can cause injuries or even fatalities. crash survivability of these types of events can be significantly improved by designing the aircraft structures for crashworthiness. since it is expensive to do a full-scale drop test, finite element analysis (fea) is used to perform crash analysis. however, a real fuselage is a complex structure as it consists of many parts, so to ease analysis process, the fuselage model can be simplified according to the simplified principles proposed by adams and lankarini [1]. the most common materials used for fuselage is aluminium alloys while laminated composites are used in military aircraft [2]. the usage of composite materials has dramatically increased in commercial aircraft since 2005 [3]. laminated composites such as glass/epoxy, graphite/epoxy, kevlar/epoxy, and boron/epoxy are commonly used in aerospace applications. the current state of the art regarding the relationships between failure mode and energy absorption, the primary material, geometrical and physical parameters relevant to crashworthiness design, and methods for evaluating the energy absorption capacity of polymer composites have been reviewed by carrythers et al. [4]. a study on the relationship between material property variables, geometrical variables and testing variables and energy absorbing characteristics of composite material was conducted in 1998 [5]. another study was conducted to investigate the effect of lamination scheme and angle variations to the displacements and failure behavior of two most common composite laminated plates, which are glass/epoxy and graphite/epoxy laminates [6]. a study on the effects of high strain rate (hsr) loadings on the glass fiber failure process in epoxy matrix during tensile loading was carried out in 2019 [7]. abdewi et al. examined the effect of corrugation geometry on the crushing behavior, energy absorption, failure mechanism and failure mode of woven roving glass fibre/epoxy laminated composite tube and found that there is no effect of corrugation geometry observed for lateral crushing [8]. in 2014, xue et al. studied the crashworthiness characteristics of aluminium fuselage [9]. mou haolei et al. studied the influences of composite skin of a fuselage section and the results showed that the crashworthiness can be influence of composite skin on the energy absorption characteristics of an aircraft fuselage 14 effectively improved by selecting appropriate composite ply numbers and ply angles [10]. yidris et. al performed a quasi-static crash analysis of a woven c-glass/epoxy fuselage section of an unmanned aerial vehicle (uav) to investigate energy absorbing capability [11]. with a wide-bodied aircraft made primarily of composites, yu and xue simulate drop tests and compared the responses of t800/qy8911 composite and glare [12]. in 2017, crash analysis of a metallic fuselage on land and water was investigated [13]. in a recent study, riccio et al. investigated the influence of material toughness on the capability of a composite fuselage barrel to tolerate an impact on a rigid surface [14]. a comparative study by experimental, numerical, and analytical methods on oblique lateral crashworthy characteristics of thin-walled circular tubes with aluminium, gfrp and cfrp materials was carried out [15]. from the literature survey, no work has been reported on the effects of different composite materials on the energy absorption characteristics of a fuselage. thus, this paper aims to investigate the effects of different composite materials on energy absorption of a fuselage section using ls-dyna. 2 finite element modelling 2.1 fuselage modelling in this study, ls-prepost was used to model a typical fuselage section while the finite element analysis was done using ls-dyna explicit finite element code. the geometry of the fuselage was kept simple which consists of five parts; skin, z-shaped frames, u-shaped stringers, passenger floor and u-shaped struts. the length and the diameter of the fuselage are 1 m and 2 m, respectively. the thickness of the skin is 0.5 cm and the thickness for the rest of the fuselage components is 0.2 cm. all the fuselage components were meshed using shell elements. based on the conducted convergence study, the finite element model consists of 42945 nodes and 39736 elements. the impact velocity used is 7 m/s and the rigid ground was modelled using rigidwall_planar. the total simulation time was set to 150 ms. figure 1a: fuselage components figure 1b: fuselage dimension figure 1: fuselage components with dimension figure 2: fe model of the fuselage and ground sharifah nadirah et al. (2023): international journal of engineering materials and manufacture, 8(1), 13-20 15 2.2 materials selection all the five parts were modelled with aluminium, and for the parametric study, only the skin material was changed to composite. in modelling the parts made of aluminium, mat_098 (simplified johnson cook) were used while in modelling the part made of composite materials – which is the skin, mat_054 (enhance composite damage) was used. the skin when replaced by composite laminates, consists of 40 layers with each lamina having a thickness of 0.125mm. the laminate fibre angle is measured with respect to the axis of the fuselage. tables 1 and 2 show the material properties of the aluminium and composite respectively used in the analysis. table 1: aluminium material properties [16] density [kg/m 3 ] elastic modulus [gpa] poisson’s ratio al 7075 2796 71 0.34 table 2: composite materials properties [17, 18] properties glass/epoxy graphite/epoxy kevlar/epoxy boron/epoxy density [kg/m 3 ] 1900 1600 1380 2000 young’s modulus (longitudinal), e1 [gpa] 38.6 181 80 204 young’s modulus (transverse), e2 [gpa] 8.27 10.3 5.5 18.5 poisson’s ratio, µ12 0.26 0.28 0.34 0.23 shear modulus of elasticity, g12 [gpa] 4.14 7.17 2.2 5.59 longitudinal tensile strength, xt [gpa] 1.062 1.5 1.4 1.26 longitudinal compressive strength, xc [gpa] 0.61 1.5 0.335 2.5 transverse tensile strength, yt [gpa] 0.031 0.04 0.03 0.061 transverse compressive strength, yc [gpa] 0.118 0.246 0.158 0.202 shear strength, s12 [gpa] 0.072 0.068 0.049 0.067 3 results and discussions 3.1 validation on aluminium fuselage crash test since experimental benchmark results are not available in the literature, only a qualitative validation was carried out. for the validation, the work of xue et al. [9] was used in which an aluminium fuselage crash on ground at an impact velocity of 9 m/s was studied and the energy absorption of each element of a fuselage is reported. comparing the internal energy graph of the present study (fig 3.) with that of [9] shown in fig 4., it is observed that the trend is similar where frames absorbed the most of impact energy followed by the skin, struts, stringers, and the passenger floor. figure 3: internal energy absorbed by each component of aluminium fuselage influence of composite skin on the energy absorption characteristics of an aircraft fuselage 16 figure 4: energy vs time curve of each component (p. xue et al., 2014) 9 3.2 energy absorption of different composite materials the structural behaviour of each part during impact is depicted in the figure 6-10 below. it can be seen in figure 610 that upon impact, lower part of the fuselage sustained damage. in all the cases studied, the frames absorbed more energy than other elements. comparing the damage pattern of various materials, aluminium fuselage has less damage compared to other materials as aluminium is less brittle than composite. it is known that aluminium material absorb energy in plastic and elastic region while composite materials mostly absorb energy in elastic deformation, making it more brittle than aluminium. hence, the damages on composite fuselage are greater than the aluminium ones. figure 5: before the impact figure 6: aluminium fuselage after impact sharifah nadirah et al. (2023): international journal of engineering materials and manufacture, 8(1), 13-20 17 figure 7: glass/epoxy skin fuselage figure 8: graphite/epoxy skin fuselage figure 9: kevlar/epoxy skin fuselage figure 10: boron/epoxy skin fuselage figure 11 shows the internal energy of different fuselage components made of aluminium at an impact velocity of 7 m/s. the trend of the graphs is the same as shown in figure 3. figure 11: internal energy plot for aluminium fuselage at 7 m/s influence of composite skin on the energy absorption characteristics of an aircraft fuselage 18 figure 12 shows the comparison of energy absorption of the skin using different materials. at 150 ms, the energy absorbed by graphite/epoxy is 1.35 kj, glass/epoxy (1.77 kj), kevlar/epoxy (1.25 kj) boron/epoxy (1.19 kj), and aluminium (0.27 kj). glass/epoxy absorbed higher energy compared to other materials while aluminium absorbed the least. figure 13 shows the overall internal energy absorbed by the whole structure and it can be seen that glass/epoxy absorbs higher amount of total energy followed by boron/epoxy, graphite/epoxy, kevlar/epoxy and lastly, aluminium. figure 12: energy absorption of the skin of different materials figure 13: total internal energy of fuselage made of different composite materials with unidirectional laminate 3.3 energy absorption of quasi-isotropic laminate for quasi-isotropic laminate, a layup of [905/455/05/-455]s was used. comparing figure 13 and figure 14, when the skin is made with quasi-isotropic laminate, the energy absorbed reduced as compared to unidirectional laminate. this 0 200 400 600 800 1000 1200 1400 1600 1800 2000 0 20 40 60 80 100 120 140 in te rn a l e n e rg y ( j) time (ms) energy absorption of the skin of different materials aluminium glass/epoxy graphite/epoxy kevlar/epoxy boron/epoxy 0 1000 2000 3000 4000 5000 6000 7000 0 20 40 60 80 100 120 140 e n e rg y ( j) time (ms) total internal energy of different materials aluminium glass/epoxy graphite/epoxy kevlar/epoxy boron/epoxy sharifah nadirah et al. (2023): international journal of engineering materials and manufacture, 8(1), 13-20 19 is because with quasi-isotropic laminate skin, the fuselage becomes stiffer as quasi-isotropic is known to have a laminate with 0°, ±45° and 90°. thus, it absorbed less energy and have lesser damage. however, in this case glass/epoxy absorbed the highest energy followed by boron/epoxy, kevlar/epoxy and lastly, graphite/epoxy. figure 14: total internal energy of fuselage made of different composite materials with quasi-isotropic laminate table 3: specific energy for different materials materials mass of the structure (kg) specific energy (j/kg) (unidirectional) specific energy (j/kg) (quasi-isotropic) aluminium 282.791 17.692 17.692 glass/epoxy 257.679 22.704 20.891 graphite/epoxy 245.182 22.130 19.202 kevlar/epoxy 238.363 22.046 20.143 boron/epoxy 257.816 21.716 19.149 as the advantage of composites is on weight savings, it is important to compare the specific energy absorption. the mass of the structure can be computed directly from ls-dyna and it is included in the table 3 above for comparison. it can be noted from table 3 that fuselage made of unidirectional glass-epoxy laminate proved to be the best in absorbing energy with the least mass. similarly, fuselage made of kevlar/epoxy with least mass, has higher specific energy as compared to boron/epoxy. the specific energy absorbed by aluminium fuselage is also included here for comparison. fuselage made completely of aluminium has the lowest specific energy as compared to any other composite laminates. 4 conclusions this study simulates fuselage crash tests on rigid ground using ls-dyna. the aluminium fuselage skin was replaced with different materials to study the effect of different materials on energy absorption characteristics of a fuselage. it was noticed that the lower part of fuselage deformed the most due to the impact and the results showed that frames and skin contribute the most in energy absorption while passenger floor and strut contribute the least, regardless of any material. as for the effect of different materials on energy absorbing capability, it is found that glass/epoxy absorbs more energy than any other composite materials as well as aluminium. finally, it was found that fuselage made of glass-epoxy laminate with highest specific energy proved to be the best laminate in absorbing energy with the least mass. 0 1000 2000 3000 4000 5000 6000 7000 0 20 40 60 80 100 120 140 e n e rg y ( j) time (ms) internal energy of different materials for quasi-isotropic laminate glass/epoxy graphite/epoxy kevlar/epoxy boron/epoxy influence of composite skin on the energy absorption characteristics of an aircraft fuselage 20 references 1. adams, a., & lankarani, h. m. (2003). a modern aerospace modeling approach for evaluation of aircraft fuselage crashworthiness. international journal of crashworthiness, 8(4), 401–413. https://doi.org/10.1533/ijcr.2003.0234 2. adrian p. mouritz (2012). materials and material requirements for aerospace structures and engines. (2012). introduction to aerospace materials, 39–56. https://doi.org/10.1533/9780857095152.39 3. smith, f. (2013). the use of composites in aerospace: past, present, and future challenges. avalon consultancy services ltd, 1–40. https://avaloncsl.files.wordpress.com/2013/01/avalon-the-use-of-composites-in-aerospaces.pdf 4. carruthers, j. j., kettle, a. p., & robinson, a. m. (1998). energy absorption capability and crashworthiness of composite material structures: a review. http://appliedmechanicsreviews.asmedigitalcollection.asme.org/ 5. ramakrishna, s., & hamada, h. (1998). energy absorption characteristics of crash worthy structural composite materials. key engineering materials, 143 part ii, 585–620. https://doi.org/10.4028/www.scientific.net/kem.141-143.585 6. noh, n. n., samsudin, a. h., & mahmud, j. (2017). failure analysis of glass/epoxy and graphite/epoxy laminates due to the effect of variation in lamination scheme and angle of fibre orientation. materials science forum, 889 msf, 36–44. https://doi.org/10.4028/www.scientific.net/msf.889.36 7. kim, j. h., mates, s. p., heckert, n. a., woodcock, j. w., & holmes, g. a. (2019). effect of strain rate on glass fiber failure process in a glass fiberepoxy model composite. https://doi.org/10.6028/nist.tn.2057 8. abdewi, e. f., sulaiman, s., hamouda, a. m. s., & mahdi, e. (2008). quasi-static axial and lateral crushing of radial corrugated composite tubes. thin-walled structures, 46(3), 320–332. https://doi.org/10.1016/j.tws.2007.07.018 9. xue, p., ding, m. l., qiao, c. f., & yu, t. x. (2014). crashworthiness study of a civil aircraft fuselage section. latin american journal of solids and structures, 11(9), 1615–1627. https://doi.org/10.1590/s167978252014000900007 10. mou, h., zou, t., feng, z., & ren, j. (2014). crashworthiness simulation research of fuselage section with composite skin. procedia engineering, 80, 59–65. https://doi.org/10.1016/j.proeng.2014.09.060 11. yidris, n., zahari, r., majid, d. l., mustapha, f., sultan, m. t. h., & rafie, a. s. m. (2010). crush simulation of woven c-glass/epoxy unmanned ariel vehicle fuselage section flapping wing micro-air-vehicle. in international journal of mechanical and materials engineering (ijmme) (vol. 5, issue 2). https://www.researchgate.net/publication/266597778 12. yu, z. l., & xue, p. (2017). crashworthiness study of composite fuselage section. key engineering materials, 725 kem, 94–98. https://doi.org/10.4028/www.scientific.net/kem.725.94 13. ali, j. s. m., & hasfareeza, m. y. (2017). crash analysis of an aircraft fuselage under belly landing. international journal of recent research aspects issn: 2349-7688, 4(4), 75–78. 14. riccio, a., saputo, s., sellitto, a., & di caprio, f. (2020). a numerical assessment on the influences of material toughness on the crashworthiness of a composite fuselage barrel. applied sciences (switzerland), 10(6). https://doi.org/10.3390/app10062019 15. sun, g., guo, x., li, s., ruan, d., & li, q. (2020). comparative study on aluminum/gfrp/cfrp tubes for oblique lateral crushing. thin-walled structures, 152. https://doi.org/10.1016/j.tws.2019.106420 16. liu, x., guo, j., bai, c., sun, x., & mou, r. (2015). drop test and crash simulation of a civil airplane fuselage section. in chinese journal of aeronautics (vol. 28, issue 2, pp. 447–456). chinese journal of aeronautics. https://doi.org/10.1016/j.cja.2015.01.007 17. autar k. kaw. (2006). mechanics of composite materials. taylor & francis. 18. wang, j., olortegui-yume, j., & müller, n. (2010). stress and vibraiton analysis for woven composite axial impeller. http://www.asme.org/about-asme/terms-of-use international journal of engineering materials and manufacture (2021) 6(2) 95-101 https://doi.org/10.26776/ijemm.06.02.2021.02 n. abidah 1 , m. hazza 2 1 department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia 2 mechanical and industrial engineering department school of engineering, american university of ras al khaimah united arab emirates e-mail: muataz.alhazza@aurak.ac.ae reference: n. abidah and m. hazza (2021). influence of buffer size change in critical chain scheduling: case study. international journal of engineering materials and manufacture, 6(2), 95-101. influence of buffer size change in critical chain scheduling: case study n. abidah and m.h. al hazza received: 17 martch 2021 accepted: 04 april 2021 published: 15 april 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract performing the critical chain scheduling (ccs) and buffer management (bm) in project management has recently risen as one of the most popular project management approaches. the critical chain scheduling (ccs) approach is replacing the traditional scheduling method to reduce the uncertainty associated with time schedules. the research highlights the importance of critical chain scheduling in project execution by investigating using buffers in the critical paths and the feeding baths in project management using a real case study. the case study was studied by analyzing the schedule provided and then implementing ccs and bm using four different methods. the methods are cut and paste (c&pm), the root square method (rsem), the adaptive procedure with resource tightness, and the adaptive procedure with network density (apnd). the buffer size obtained for each method was determined. from the result got, for project buffer in adaptive approach with network density method yields a larger buffer size compared to the adaptive procedure with resource tightness method. while for feeding buffer also show that apnd resulted in a larger buffer size than aprt. finally, the proposed buffer size was investigated and simulated using the what if approach. keywords: project management, critical chain, buffer, buffer sizing. 1 introduction the project manager's leading role is to achieve the project objectives on time within the budget. one of the challenges of this role is the critical activities with zero or low time tolerances. the project activities in the critical chain are the activities that have zero lead time. these dependent activities and activities close to the critical chain with low lead time need to be managed effectively and beneficially because any delay in those activities will delay the project completion time. from 1956 until 1997, project managers used two main scheduling tools: the critical path method (cpm) and the project management review technique (pert). cpm was developed from 1956 to 1958 by dupont de nemours and company in conjunction with the univac applications research center of remington rand [1]. in 1957, pert was developed by the u.s. navy special projects office on the polaris missile system to support the nuclear submarine projects [2]. cpm is based on focusing on the float or the time each activity can delay without affecting the project's total completion time. however, pert is considering the probability of finishing the project on time scheduled. finally, pert and cpm integrated to take both methods' advantages to be valuable tools and techniques in project scheduling named cpm/pert. in 1997, a new improvement was introduced by goldratt 1997 [3], known as critical chain project management (ccpm). the fundamental principle of ccpm is by using the critical chain instead of the critical path [4]. leach [5] said that ccpm is improving by aggregating the uncertainties at the end of paths that protect the overall project completion on the critical chain path and protect the feeding buffers by protecting the critical chain from path merging. however, the critical chain technique for overcoming uncertainty in a project offers that buffers are added at the end of the critical chain and feed chains [6]. zhao et al. [4] proposed improving a two-stage approach focusing on the feeding buffer. they suggest solving the conflict that may happen. the precedence conflict or source conflict can be solved by rescheduling that will lead to a noncritical chain that may start earlier than a critical chain in critical chain activities. bhattacharjee [7] lists the benefit of applying critical chain scheduling (ccs) instead of the critical path method (cpm) or pert. firstly, avoid influence of buffer size change in critical chain scheduling: case study 96 uncertainties that may occur within the project duration. the due dateline for each activity is not fixed and emphasizes the project's completion date. secondly, more assured activity duration estimation– two measures, which are realistic 90% confidence and aggressive estimation 50 % confidence. aggressive activity estimation is used in ccs to avoid excessive activity's working time. thirdly, if the schedule completion date of 50% estimation is not met, it will protect the project. reduce the bottleneck's impact in the schedule-feeding buffer to protect the critical chain from variation in the noncritical chain. in another paper, chuan & gershwing [8] share the buffering concept in manufacturing to ensure the production line runs smoothly by maintaining enough supplies even if there are variations or fluctuations in the production process or demand chain, production capacities, and lead time. buffer often supplies the raw material and inventories of the finished products waiting for the shipment. for instance, if there is a delay in suppliers' lead time, the raw material buffer can compensate the shortage for the following production process. thus, this can contribute to the minimization of loss and can maximize the efficiency of the process. according to büchmann [9], the buffers can be material buffers, resource buffers, equipment buffers, or some entity to protect the production flow. however, this is limited to study about time buffer in the project schedule. in his paper, büchmann stated there two types of time buffer for scheduling: a) activity buffers: applied to each activity in the schedule to protect the variability in production, such as incidents and fluctuation in demand. b) stage buffer – to protect unexpected occasions that might happen between activities. thus, to prevent delays happen, the buffers are allocated to a specific position with different functions. categories of the buffers are divided into three types that according to their positions. project buffer is the time buffer added to the end of the chain to protect project delivery time. feeding buffers is the time buffer allocated at every noncritical path and feed the critical chain to prevent the slack on a critical task. lastly, resource buffers are the alert used to indicate that the resource is needed to perform an activity. project buffer plays the most crucial role in production scheduling. as it is located at the end of critical path, the project buffer size affects most the whole project's duration, so the project buffer must be determined reasonably. as a result, determining the buffer size is a crucial for project success. tukel et al., [10] addressed five different simulation methods for determining feeding buffer sizes in ccs: cut and paste method, root square error method, adaptive procedure with resource tightness, adaptive procedure with density, and adaptive procedure with resource tightness. 2 case study the case study is named 'schedule the chocolate production for xyz brand. the project network diagram is presented in figure 1, representing the project activities according to their precedence, duration, and resources. the activity durations are shown in days while the respective resources are presented in the alphabet. the renewable resource required to perform the activity is identified as a, b, c, d, e, and f at the respective nodes. the availability of each resource is different is a, b, c, d e, f, and g availability is one in applying a critical chain, each task's duration must be estimated almost to half of the expected duration. the schedule duration shortened after the activity duration is estimated aggressively. from 196 days of project duration, the time was reduced to 99 days only. the critical chain also can be identified as the longest chain. in figure 2, the red box indicates the chain of critical activities. figure 1: project network abidah and muataz (2021): international journal of engineering materials and manufacture, 6(2), 95-101 97 project critical chain consists of the sequences of task 1-2-3-8-9-11-14-16-19-21-22-23-24-25, and the essential length of the chain is equal to 99 days. project buffer is placed at the end of the critical chain. while feeding buffer is placed at the end of the noncritical chain that feeds to the critical chain. figure 3 shows the buffer in a blue box. there are 3 feeding buffers, and 1 project buffer are placed. using the data in table 1, the calculation is being done using two method of calculation. figure 2: critical chain figure 3: buffer location influence of buffer size change in critical chain scheduling: case study 98 table 1: project data activity normal duration aggressive duration differences 50% of differences 1 14 7 7 3.5 2 14 7 7 3.5 3 28 14 14 7 4 21 11 10 5 5 7 4 3 1.5 6 21 11 10 5 7 7 4 3 1.5 8 14 7 7 3.5 9 14 7 7 3.5 10 7 4 3 1.5 11 14 7 7 3.5 12 14 7 7 3.5 13 14 7 7 3.5 14 14 7 7 3.5 15 7 4 3 1.5 16 7 4 3 1.5 17 7 4 3 1.5 18 7 4 3 1.5 19 14 7 7 3.5 20 14 7 7 3.5 21 14 7 7 3.5 22 14 7 7 3.5 23 7 4 3 1.5 24 14 7 7 3.5 25 14 7 7 3.5 3 results and discussions the calculation for each buffer size method is started by calculating the standard deviation. the standard deviation for each activity is computed by 50% of the difference between normal duration and aggressive estimation (d). then, the buffer size can be calculated using equation 1. where k(scale parameter) is different based on adaptive procedure with network density method or adaptive approach with resource tightness. (1) (2) (3) after calculation, the buffer sizes of each method are listed below 1. adaptive procedure with network density project buffer 1-2-3-8-9-13-14-16-19-21-22-23-24-25 = (1.9) (13.72) = 26 days feeding buffer 6-10-17-18 = (1.75) (5.63) = 9 days feeding buffer 7-17-18 = (1.6) (2.59) = 4 days feeding buffer 5-11-12-15 = (1.75) (6.24) = 10. ays feeding buffer 5-11-20 = 8 days 2. adaptive procedure with resource tightness project buffer 1-2-3-8-9-13-14-16-19-21-22-23-24-25 = (1.9) (13.72) = 20 days feeding buffer 6-10-17-18 = (1.75) (5.63) = 9 days feeding buffer 7-17-18 = (1.6) (2.59) = 4 days feeding buffer 5-11-12-15 = (1.75) (6.24) = 8 days feeding buffer 5-11-20 = 7 days abidah and muataz (2021): international journal of engineering materials and manufacture, 6(2), 95-101 99 the buffer size obtained for each method is summarized in the table below. from the result got, for project buffer, the adaptive procedure with network density method yields a larger buffer size than the adaptive approach with the resource tightness method. while for feeding buffer also show that apnd resulted in a larger buffer size than aprt. the project buffer is placed at the end of the critical chain and resulted in additional 26 days. the 26 days is the time buffer to cope with any delays that might happen in the schedule. the yellow box indicated the buffer. the project buffer is placed at the end of the critical chain and resulted to additional 20 days. the 20 days is the time buffer to cope with any delays might happen in schedule. table 2: buffer size result method p.b. f.b. 7-17-18 f.b. 5-11-20 fb 5-11-12-15 fb 6-10-17-18 adaptive procedure network density 26 4 8 10 9 adaptive procedure resource tightness 20 4 7 8 9 figure 4: buffer (apnd figure 5: buffer (aprt) influence of buffer size change in critical chain scheduling: case study 100 table 3: result of simulation remaining duration project completion (%) buffer penetration 0 100% -380.77% 12 87.88% -334.62% 30 69.70% -265.38% 60 39.39% -150% 120 -21.21% 80.77% from the figure above, the differences between overall duration can be seen. the duration of the project using adaptive procedure with network density method is longer than adaptive procedure with resource tightness. a simulation that considers the possible scenario might happen in the project can evaluate the critical chain schedule. a project manager can determine the health of buffer or buffer consumption in the project schedule by using the whatif simulation. the simulation to calculate buffer penetration is being done. the project manager reviewed the project progress on the fifth day of project execution. first, the project manager predicts that based on the planned project schedule. if the remaining duration to complete the project is 12 days left, the project is completed by 87.88 % and penetrates the time buffer at -334.62. the negative sign indicates that the buffer is not consumed yet. so the project is at no risk of being delayed and contrasted with estimating the remaining 120 days. in reviewing some uncertainty and problem might happen, the project manager estimate that the remaining days or possibility to complete the project is 120 days. so the project acts to be delayed and consume 80.77% of a time buffer. a negative sign of percentage of project completion shows that the project is delayed for 21 days. so the project finishes 21 days of 26 allocated project time buffer. table 4 shows the result of the simulation generated from microsoft excel. after implementing and applying all necessary steps for the critical chain and buffer approach method, it is now possible to conclude which buffer location and sizing method should be proposed in the project. in selecting the buffer, the size method is depending on how risk-averse the project manager is. if the project manager is a risk-seeker who prefers a more extended deadline, an adaptive procedure with a network density method is suggested to determine the buffer size as the apnd yields a larger time buffer than adaptive procedure with the resource tightness method. the buffer size generated from the adaptive procedure with resource tightness is preferable to high risk seeker. high risk seeker is the project manager who is planning to be competitive to finish the project earlier. 4 conclusions the actual life case study acquired from a local company is the project for production schedule being studied to apply the critical chain approach. starting from review the provided schedule, the critical chain approach is implemented to the schedule and buffer management. there are six steps to be followed to achieve the aim of implementation. the results of each buffer sizing method are compared to select the suitable buffer size in the schedule. due to lack of professional software to simulate and validate the efficiency of buffer size. using microsoft project, one of the tools in project management, we can monitor the project. the microsoft project feature such as tracking gantt, report in progress, and resource overview assists the project manager. to simulate how buffer effect the schedule, the what-if concept simulation is designed using microsoft excel. this simulation can help the project manager identify the project completion percentage and buffer penetration in the project schedule. a fever chart is also a tool used to check the time buffer's health in the schedule. acknowledgement the authors would like to acknowledge that the work have been conducted in the department of manufacturing and materials engineering, international islamic university malaysia. the authors are grateful to those who contributed directly and indirectly in producing this paper. references 1. wickwire, j. m., & smith, r. f. (1974). the use of critical path method techniques in contract claims. public contract law journal, 1-45. 2. aziz, r. f. (2014). rpert: repetitive-projects evaluation and review technique. alexandria engineering journal, 53(1), 81-93. 3. goldratt, e.h., "critical chain", great barrington, ma: north river press. 1997 4. zhao, y., cui, n., & tian, w. (2020). a two-stage approach for the critical chain project rescheduling. annals of operations research, 285(1), 67-95. 5. leach, l. p. (1999). critical chain project management improves project performance. project management journal, 30(2), 39-51. abidah and muataz (2021): international journal of engineering materials and manufacture, 6(2), 95-101 101 6. iranmanesh, h., mansourian, f., & kouchaki, s. (2016). critical chain scheduling: a new approach for feeding buffer sizing. international journal of operational research, 25(1), 114-130. 7. bhattacharjee s. k. (2011) fundamentals of pert/cpm & project management. khanna publishers 8. shi, c., & gershwin, s. b. (2009). an efficient buffer design algorithm for production line profit maximization. international journal of production economics, 122(2), 725-740. 9. büchmann-slorup, r. (2014). applying critical chain buffer management theory in location-based management. construction management and economics, 32(6), 506-519. 10. tukel, o. i., rom, w. o., & eksioglu, s. d. (2006). an investigation of buffer sizing techniques in critical chain scheduling. european journal of operational research, 172(2), 401-416. https://www.kopykitab.com/index.php?route=product/search&q=s.+k.+bhattacharjee https://www.kopykitab.com/khanna-publishers international journal of engineering materials and manufacture (2021) 6(3) 176-186 https://doi.org/10.26776/ijemm.06.03.2021.09 ochuokpa e. o 1 , yawas, d. s. 2 , sumaila, m. 2 and adebisi a.a 1,3 1 department of metallurgical and materials engineering, ahmadu bello university, zaria, nigeria 2 department of mechanical engineering, ahmadu bello university, zaria, nigeria 3department of metallurgical and materials engineering, air force institute of technology, kaduna, nigeria e-mail: dyawas@yahoo.com reference: ochuokpa et al. (2021). development of aluminium based mango seed mangiferaindica shell ash (mssa) particulate metal matrix composite. international journal of engineering materials and manufacture, 6(3), 176-186. development of aluminium based mango seed mangiferaindica shell ash (mssa) particulate metal matrix composite ochuokpa e. o, yawas, d. s., sumaila, m. and adebisi a. a. received: 11 march 2021 accepted: 11 may 2021 published: 15 july 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract a composite material is a combination of two or more chemically distinct and insoluble phases; its properties and structural performance are superior to those of the constituents acting independently. mmcs are made by dispersing a reinforcing material into a metal matrix to improve their properties. they are prepared by powder metallurgy and casting, although several technical challenges exist with casting technology. achieving a homogeneous distribution of reinforcement within the matrix is one such challenge, and this affects directly on the properties and quality of composite. in this work a composite is developed by adding mango seed shell ash (mssa) particulate in alsi-mg alloy by mass ratio 5%, 10%, 15% and 20%. the composite was prepared by stir casting technique. it is proposed to use this material for production of motorcycle wheel hub which are subjected to continuous wear as the hubs are in direct contact with the brakes and rotating sprockets. the mssa, was characterized using xray fluorescent (xrf). the result reveals sio2, has the highest percentage composition followed by cao, al2o3, fe2o3 and mg2o as major phases. the presents of these hard constituent compounds suggests that the mango seed shell ash can be used as particulate reinforcement in various metal matrices since the chemical composition has similarity with the xrf analysis of periwinkle shell ash, rice husk, fly ash, and bagasse ash currently used in metal matrix composite. mechanical tests such as hardness test and impact test were conducted. the results revealed that increase in the percentage of mssa progressively increased the hardness of the material from 5% wt to a maximum hardness of 43.2 hv at 15% addition of mssa. this represents a 26.16% improvement over the unreinforced alloy. however, the impact energy progressively decreases of the material from 5%wt of mssa and later increased to optimum energy at 15% addition of mssa. from the results it is concluded that composite material such as alsi-mg/ mssa is one of the options as a material for production of motorcycle hub. the wear test of the composite was then carried out using taguchi design to optimize the range of mssa from 5% wt -15% wt., sliding speed of 5cm/s -20cm/s, sliding distance from 50m to 200m, and the load of 2n, 4n, 6n, & 8n respectively. analysis of the result of sn ratio for wear rate shows the optimum wear resistant value is in the combination of load=4n, sliding speed = 10cm/s sliding distance=200m and mssa=15 wt% these also correspond with the analysis of wear maps & wear rate presented in the diagrams of dynamic friction coefficient (cof) for al-simg/ mssa composite. keywords: aluminium metal matrix composite, stir casting, mango seed shell ash, motorcycle hub. 1 introduction the desire to develop a composite material using mango seed shell ash (mssa) to reinforce the conventional motorcycle hub was prompted by the fact that the motorcycles usually referred to as "okada" in nigeria have become a popular mode of transportation, the hubs are in direct contact with the brakes and rotating sprockets hence they are subject to frequent mechanical failure due to wear as a result bad road. they are therefore in high demand for replacement. similarly, there are large quantities of mango seeds discarded as waste on the streets across nigerian rural communities after consumption of the mango fruits constituting environmental hazards to the public. the local content policy of nigerian government in recent times has stimulated great interest in the utilization of abundant agricultural waste for in production of engineering materials. agricultural waste products such as mellon shell, eggshell, sugarcane, bagasse, rice husk, coconut shell, bamboo leaf, ground nutshell and other organic waste have been successfully used for aluminium alloy particulate composite reinforcement [1], this is in line with the global development of aluminium based mango seed mangiferaindica shell ash (mssa) particulate metal matrix composite 177 demand for the development of advanced engineering materials for various engineering applications in modern times [2]. however, to the best of our knowledge, no work has been done on the use of abundant mango ‘mangiferaindica’ seed shell ash (mssa) as reinforcement for aluminium matrix. this research therefore provides pioneering knowledge on the possibility of using mango seed shell as reinforcement for aluminium matrix composites (amcs) for production of automobile component and other engineering applications. it is expected to reduce the high cost of the synthetic reinforcements of amcs such as silicon carbide (sic) and alumina (al2o3) which are imported at high foreign currency exchange rate in nigeria leading to high cost of production of motorcycle wheel hubs. there are some micro structural features that limit mechanical properties of cast alsimg alloys such as porosity, coarse acicular si particles and coarse primary aluminium dendrites [3]. similarly, the presence of mg and fe in the alloy gives an opportunity for the formation of eutectic α + mg2si and platelets of fe2si2al9 in addition to the si platelets. these plate-shaped phases provide easy crack nucleation sites and propagation paths, resulting in relative low strengths and ductility [4]. motorcycle hub is in direct contact with the brakes and rotating sprockets hence it is subject to frequent mechanical failure. the main extent and reason for their failures include surface fatigue wear caused by fracture and breakages as a result of direct contact with the brakes and rotating sprockets, bad road and gallops, and poor quality of spares. after consumption of the mango fruits, a large quantity of mango seeds is discarded as waste in nigeria constituting environmental hazards to the general public. this research is aimed at developing aluminium based mango seed mangiferaindica shell ash (mssa) particulate metal matrix composite for engineering application. to the best of our knowledge, no previous work has been done on the use of abundant mango seed shell as in the reinforcement of al matrix composites (amcs) for engineering applications. this study will therefore provide pioneering knowledge on the possibility of using mango seed shell ash (mssa) as reinforcement for amcs for spare parts production. it will also succeed in creating employment opportunities in nigeria by converting agro-waste product to wealth and positively influence the economy. it will help solve the environmental problems caused by the overwhelming quantity of agro-waste disposal challenges in nigeria. 2 literature review 2.1 aluminium alloying elements the typical alloying elements added to aluminium are zinc (zn), copper (cu), silicon (si), iron (fe), magnesium (mg), lithium (li). manganese (mn), nickel (ni) and tin (ti) [5]. because of their varying solid solubility, some are used as solid solution while others are added to form various desirable intermetallic compounds. 2.2 materials for motorcycle hubs mostly, aluminium motorcycle hubs are products of aluminiummagnesium alloys because of their unique casting properties, good resistance to corrosion, easy to cast into thin or thick sections, excellent machinability, and good strength to weight ratio [6]. 2.2.1 al-si-mg alloy an alloy of al-si-mg has wide application in automotive and aerospace industry due to their excellent castability and a high strength-to-weight ratio [7]. 2.2.2 aluminium oxide al2o3, is known to be stable in aluminium, but it reacts with magnesium in aluminium alloys containing mg to form mgo and mgal2o4. (spinel) as shown in the following equations. mgo may form at high magnesium level and lower temperature whereas the spinel will form even at very low magnesium levels [8]. this explains why al2o3 is not thermodynamically stable in most aluminium alloys. 3mg + al2o3 = 3mgo + 2al (∆g= -117kj at 1000k)----------------------------------------------------------------(2.1) and 3mg + 4al2o3 = 3mgal2o4 + 2al (∆g = 215.1kj at 1000k)-----------------------------------------------------------(2.2) 2.3 the role of magnesium improvement of wettability between the al-mg-si alloy and the reinforcements. magnesium and magnesium alloys are amongst the lightest materials for practical use as the matrix phase in metal matrix composites. when compared to other available structural materials, magnesium is attractive because of its unique combination of low density and excellent machinability. the role of silicon alloy; the role of silicon is for casting flowability. for foundry production of castings, contain amounts of silicon far more than the amount that is soluble or needed for strengthening alone are required [9]. the function here is chiefly to improve casting soundness and freedom from cracking, but the excess silicon also serves to increase wear resistance. aluminium alloys that are used for wear resistance application base on aluminium silicon alloy system [10]. aluminium casting alloys must contain enough amount of silicon which is a eutecticforming element, this is to enhance adequate fluidity to fill the shrinkage that usually occur during casting. ochuokpa et al. (2021). international journal of engineering materials and manufacture, 6(3), 176-186. 178 2.4 defects in al-si-mg alloy the coarse acicular si particles and coarse primary aluminium dendrites are bound to negatively affect the hardness properties of al-si-mg alloy in production of motorcycle hub [11]. there is possibility of improving the properties of this alloy by the use of agro waste ’mango seed shell ash’ as reinforcement hence the need to study the use of mango seed shell ash. there are three micro structural features that limit mechanical properties of cast alalloys such as ductility, toughness and fatigue resistance: porosity, coarse acicular si particles and coarse primary aluminium dendrites [9]. 2.5 description of motorcycle wheel hub the wheel rims are usually steel or aluminium generally with steel spokes and an aluminium hub. the rear motorcycle hub is at the central part of a motorcycle wheel that rotates on or with the axle and from which spokes radiates. it is in direct contact with the brakes and rotating sprockets hence it is subject to frequent mechanical failure. figure 1: the rear motorcycle wheel hub 2.6 classification of composite materials based on the type of matrix, composites are classified into the followings: metal matrix composites, polymer matrix composites, ceramic matrix composites, carbon-carbon composites, and hybrid composites. 2.7 benefits of composite materials in the recent past, materials development has shifted from monolithic to composite materials for adjusting to the global need for reduced weight, low cost, quality, and high performance in structural materials. driving force for the utilization of aluminium matrix composites (amcs) in areas of aerospace and automotive industries include performance, economic and environmental benefits [12]. the conventional monolithic materials have limitations in achieving good combinations of strength, stiffness, toughness and density. metal matrix composites (mmcs) possess significantly improved properties including high specific strength; specific modulus, damping capacity and good wear resistance compared to unreinforced alloys. aluminium-metal matrix composite (amc) materials having a lower density and higher thermal conductivity as compared to the traditionally used grey cast irons are expected to result in weight reduction of up to 60-65 % in automotive parts [13]. several works have been carried out on development aluminium matrix composites (amcs) in nigeria. adebisi et al [14] studied the effect of particle size of sio2 on the properties of al-si particulates. their results show that the use of fine particles have a higher degree of strengthening than the use of coarse reinforcement particles. maleque et al [15] stated that in composites, materials are combined in such a way as to enable one to make better use of their parent material while minimizing to some extent the effects of their deficiencies. aigbodion [16] studied the possibility of using kankara clay found in abundance in kankara village in kastina state nigeria as reinforcement for al-si-alloy. the result shows that kankara clay can serve as potential reinforcement for aluminium alloy up to a maximum of 20wt% of this clay body in the alloy. amaren & aku [17] carried out an xrf analysis on periwinkle shell ash and confirmed that sio2, cao, mgo, cr2 o3. and fe2o3 were found to be major constituents of periwinkle ash. the presence of hard elements like sio2, cao, mgo, cr2 o3. and fe2o3 suggested that periwinkle shell ash particles can be used as reinforcement material. development of aluminium based mango seed mangiferaindica shell ash (mssa) particulate metal matrix composite 179 madakson et al [18] characterized coconut ash as a constituent of metal matrix composite for potential application in automobile sector. microscopic (particle size, sem and xrf) and spectroscopic analysis (xrd and ftir) were carried out for characterization of the coconut shell ash. mostly, aluminium motorcycle hubs are products of alloys of al-si-mg because of their unique casting properties, good resistance to corrosion, easy to cast into thin or thick sections, excellent machinability, and a high strength-toweight ratio as compared to cast iron hub. ezatpour & sajjadi [19] revealed that the addition of al2o3-mgo reinforcement to aluminium resulted to enhancement of hardness and strength of material. li et al [20] studied a production planning model for make-to-order foundry flow shop with capacity constraint. the results shows that the proposed approach can achieve better profit rate of orders in actual foundry industry more effectively. 3 materials and methods the materials used in this research includes: • 5kg of waste mango seed were obtained from palladan and samara zaria kaduna state nigeria. • the scrapped of convectional motorcycle hub containing al-si-mg, 3.1 methodology determine the chemical composition min pal compact energy dispersive x-ray spectrometer was used for elemental analysis of mango seed shell ash and the powder from the conventional motorcycle hub. carbonization of mango seed shell ash was carried the following steps, • the mango seeds shells collected were dried in the sun for three days, • decorticated manually to remove the seed from the shell and grinded into powder. • the powder of mssa was packed in a steel box and carbonized in an air tightened condition using a furnace at 600°c for four hours. • sieved & the particle size analysis carried out from 250цm to 106 µm development of the composite through stir casting is a suitable way for manufacturing composites with up to 30% volume fractions. the stir casting was carried out according to standard casting procedures as shown in figure.2 below. figure.2: casting procedures. table 1: charging of matrix and reinforcement into crucible furnace casting runs % al-si-mg alloy % mssa samples no 8 1 100 control c 2 95 5 a 3 90 10 b 4 85 15 d 5 80 20 e ochuokpa et al. (2021). international journal of engineering materials and manufacture, 6(3), 176-186. 180 3.2 stir casting process a sand mold was prepared with diameter 30mm and the length 80mm and used to produce the test bars. the scrap motorcycle hub to be melted was first charged into the furnace and temperature was raised to 750 o c to superheat the aluminium alloy melt. the 15%wt. of mssa particle was pre-heated to 650 o c to enhance wettability with the matrix. the pre-heated mssa particles were added and stirred continuously for 60 seconds to achieve uniform distribution of the reinforcement by manual process at a stirring speed 100 rpm. the pouring temperature was controlled at about 720 o c. the crucible was removed from the furnace with special tongs was used as a ladle to pour into the prepared molds directly. after casting, the bars were machined to standard samples for mechanical tests. 3.3 determination of hardness value the hardness values of the cast samples were determined using a vickers hardness testing machine according to astm; e18-15 standards. the cast bars were machined to standard dimensional specifications of the test samples. the average reading of three different locations on the sample surfaces were taken in each case. 3.4 determination of impact strength the impact strength was determined using the charpy universal impact testing machine with specifications hounsfield balance impact machine serial no 3203, total force capacity 48ib in the department of mechanical engineering, ahmadu bello university zaria. the sample were prepared with diameter of 8 mm, vnotched to 0,5 mm depth from the middle with the total length of 46 mm according to standard of iso 8256 (2004) for dent specified. the sample was fixed parallel between the stationary clamp and at a cross head of the pendulum hammer set to hit the cross head at the lowest point of the circular motion. the hammer speed was set at 1.5m/s which corresponded to the falling angle of 60. the specimen was broken by a single overload event due to the impact of the pendulum. a stop pointer is used to record how far the pendulum swings back up after fracturing the specimen. the impact toughness of a metal is determined by measuring the energy absorbed in the fracture of the specimen. this is simply obtained by noting the height at which the pendulum is released and the height to which the pendulum swings after it has struck the specimen. the height of the pendulum times the weight of the pendulum produces the potential energy and the difference in potential energy of the pendulum at the start and the end of the test is equal to the absorbed energy [15]. 3.5 taguchi experimental design (wear test & tribological analysis) taguchi experimental design was used to optimize the range of reinforcement of mssa from 5%wt-15%wt in the alalloy matrix. standard formula according to astm d 6079-97/en 590 standards was used in examining the abrasive wear. the test samples were fabricated with a length of 35mm and a diameter of 10mm and were subjected to abrasive wear condition. the wear test of the composite was carried out using 0%wt, 5%wt.10%wt, & 15%wt of mssa, sliding speed of 5cm/s -20cm/s, sliding distance from 50m to 200m, and the load of 2n, 4n, 6n & 8n respectively. the wear testing machine used was anton paar gmbh anton paar strasse 208054 graz – austria in the faculty of engineering ahmadu bello university multi-user laboratory. taguchi design l16 (4^4) factors: 4 runs: 16; the result of taguchi orthogonal array design l16 (4^4) factors is shown in table 3. evaluation of the impute process parameters based on based on taguchi design. the result of evaluation of the impute process parameters based on based on taguchi l16 design. is shown in table. table 2 and table 3 above provides adequate data required for tribological (wear & friction) analysis. table 2: taguchi l16 orthogonal array design factors 1 2 3 4 1 load (n) a 2 4 6 8 2 sliding speed (m/s) b 5 10 15 20 3 sliding distance (m) c 50 100 150 200 4 mssa reinforcement (wt%) d 0 (c) 5(a) 10(b) 15 (d) development of aluminium based mango seed mangiferaindica shell ash (mssa) particulate metal matrix composite 181 4 results and discussions 4.1 analysis of sn ratio for wear rate from table 4. the input functions with higher delta values have higher ranking and have more influence on the wear rate. load. mssa, sliding speed and sliding distance. (adbc). (mssa). a2=4n, b2= 10cm/s c4=200m d4=15 wt%. the optimum wear value will be obtained from the combination of load=4n, sliding speed = 10cm/s sliding distance=200m and mssa=15 wt%. the analysis of the result shows the optimum value is in the combination of load=4n, sliding speed = 10cm/s sliding distance=200m and mssa=15 wt% these also correspond with the analysis of wear maps & wear rate diagrams displayed below. table 3: evaluation of the impute process parameters based on based on taguchi l16 design a b c d wear rate (mm 3 /n/m) sample load (n) sliding speed (cm/s) sliding distance (m) mssa reinforcement (wt%) c1 2 5 50 0 0.04499 a2 2 10 100 5 0.02248 b3 2 15 150 10 0.01538 d4 2 20 200 15 0.02036 b5 4 5 100 10 0.03131 d6 4 10 50 15 0.01348 c7 4 15 200 0 0.01783 a8 4 20 150 5 0.02371 d9 6 5 150 15 0.01788 b10 6 10 200 10 0.01628 a11 6 15 50 5 0.05062 c12 6 20 100 0 0.03671 a13 8 5 200 5 0.01318 c14 8 10 150 0 0.01614 d15 8 15 100 15 0.02452 b16 8 20 50 10 0.04225 d17 4 1o 200 15 0.01532 figure 3: the sn ratio for the data means load, sliding speed, sliding distance and the mango seed shell ash ochuokpa et al. (2021). international journal of engineering materials and manufacture, 6(3), 176-186. 182 table 4: analysis of sn ratio for wear rate input function symbols s/n ratio max-min (delta) rank l1 l2 l3 l4 load a 32.5 33.8 31.5 33.5 2.3 4 s/s b 32.4 35.5 32.2 30.5 5 2 s/d c 29.5 31.0 35.1 35.8 6.3 1 mssa d 31.2 32.0 32.1 34.9 3.7 3 a= load (n) b=sliding speed (cm/s) c= sliding distance (m) d= mango seed shell ash wt% 4.2 analysis of wear maps & wear rate sliding distance (m) lo ad ( n ) 2001 751 501 251 007550 8 7 6 5 4 3 2 > – – – < 0.02 0.02 0.03 0.03 0.04 0.04 0.05 0.05 wear rate contour plot of wear rate vs load (n), sliding distance (m) figure 4: wear map 1 shows the lowest wear rate at sliding distance, 200m/s and the load of 4n mssa sl id in g sp ee d (c m /s ) 1 41 21 086420 20.0 1 7.5 1 5.0 1 2.5 1 0.0 7.5 5.0 > – – – < 0.02 0.02 0.03 0.03 0.04 0.04 0.05 0.05 wear rate contour plot of wear rate vs sliding speed (cm/s), mssa figure 5: wear map 2 shows the lowest wear rate at sliding speed of 10cm/s and 15 wt% mssa development of aluminium based mango seed mangiferaindica shell ash (mssa) particulate metal matrix composite 183 sliding distance (m) sl id in g sp ee d (c m /s ) 2001 751 501 251 007550 20.0 1 7.5 1 5.0 1 2.5 1 0.0 7.5 5.0 > – – – < 0.02 0.02 0.03 0.03 0.04 0.04 0.05 0.05 wear rate contour plot of wear rate vs sliding speed (c, sliding distance figure 6: wear map 3 shows the lowest wear rate at sliding speed, 10cm/s and sliding distance, 200m. 4.3 morphology of mango seed shell ash (mssa) table 5 shows the result of xray fluorescent (xrf) pattern of mango shell ash (mssa) which reveals that sio2, has the highest percentage composition followed by cao, al2o3, fe2o3, mg2o, k2o, zno, na2o and tio2, as major phases. the presences of these hard constituent compounds suggests that the mango seed shell ash can be used as particulate reinforcement in various metal matrices since the chemical composition has similarity with the xrf analysis of periwinkle shell ash, rice husk, fly ash, and bagasse ash currently used in metal matrix composite. amaren & aku [17], aigbodion, and hassan [1]. si and mg, enhances wettability and formation of mg2si and eutectic si α-al matrix with mssa particles. therefore, they are attractive material for reinforcement of amc for wear applications. 4.4 characterize of the convectional motorcycle hub table 6 shows the xrf pattern and elemental composition of the convectional motorcycle hub. it reveals al2o3, sio2, fe2o3 and mgo as major phases. the elemental composition of silicon content is 6. 55 wt% as reflected in table 6. this is below the standard requirement for the aluminium alloy 356 (7% si) which is the popular alloy used for sand casting. this may account for the frequent wear and failure of the conventional motorcycle hub. the addition of mssa which has content of silicon as particulate composite reinforcement may help address the problem of wear of the conventional motorcycle hub. 4.5 hardness test hardness values of al-si-mg/ mssa particulate composite with various percentage weight of mssa loading is shown in table 7. there is increasing trend of hardness strength with increase in weight percentage of mssa up to 15% weight fraction. beyond this weight fraction the hardness trend started decreasing as mssa particles interact with each other leading to clustering of particles and consequently settling down. it is observed that the unreinforced alloy has the least hardness value of 31.9 hv while at 15% mssa addition had the highest hardness value of 43.2 hv. this represents a 26.16% improvement over the convectional alloy. this indicates that there was good interfacial bonding between the matrix and the reinforcement. therefore, the optimized 15% wt of mssa reinforcement which has the best mechanical properties was selected for production of the hub. the increase in hardness is due to the presence of silicon particles formed because of reaction between the reinforcement mssa particles and the molten alalloy matrix as well as other processing parameters. factors such as non-uniform distribution of particles, cooling rate of the casting has affected the hardness value negatively hence there is no uniform hardness. the result of impact energy of al-si-mg/ mssa particulate composite with various percentage weight of mssa loading is shown in table4.4. it is observed that the impact energy is lowest at 5% mssa while at 15% mssa addition had the highest hardness value of impact energy this indicates that there was good interfacial bonding between the matrix and the reinforcement. beyond this weight fraction the impact energy trend started decreasing as mssa particles interact with each other leading to clustering of particles and consequently settling down. ochuokpa et al. (2021). international journal of engineering materials and manufacture, 6(3), 176-186. 184 table 5: elemental composition of mssa using (xrf) s/no element concentration of oxide (wt%). elemental composition (wt%) 1 na20 2.302 1.708 2 mgo 3.173 1.904 3 al2o3 13.847 7.331 4 sio2 43.574 20.334 5 p2o5 4.173 1.854 6 so3 1.797 0.719 7 cl 0.467 0.464 8 k2o 4.559 3.783 9 cao 14.895 10.639 10 tio2 2.129 1.277 11 cr2o3 0.005 0.003 12 mn2o3 0.130 0.091 13 fe2o3 6.211 4.348 14 zno 2.653 2.129 15 sro 0.089 0.075 table 6: elemental composition of sample (motorcycle hub) using (xrf) s/no element concentration of oxide (wt%) converted to element (wt%) 1 na20 0.419 0.310 2 mgo 1.014 0.608 3 al2o3 82.117 43.474 4 sio2 14.034 6. 55 5 p2o5 0.000 0.053 6 so3 0.133 0.455 7 cl 0.013 0.017 8 k2o 0.024 0.089 9 cao 0.124 0.03 10 tio2 0.050 0.018 11 cr2o3 0.026 0.115 12 mn2o3 0.165 0.801 13 fe2o3 1.144 0.59 14 zno 0.736 47.323 15 sro 0.000 0.00 table 7: variation of hardness property of the composite % mssa hardness value (hv) control c 0% mssa 31.9 a 5% mssa 33.63 b 10% mssa 42.9 d 15% mssa 43.2 e 20% mssa 36.5 development of aluminium based mango seed mangiferaindica shell ash (mssa) particulate metal matrix composite 185 table 8: impact test results samples diameter (mm) notch (mm) energy (ib. pounds) average en (pounds) average (joules) control c. 0% mssa 10.3 10.4 10.0 9.8 9.4 9.3 2.2 1.3 1.5 1.66 2.251 a. 5% mssa 10.0 10.3 10.5 9.0 9.4 9.7 0.5 1.5 1.0 1.0 1.356 b 10% mssa 10.5 10.5 10.2 9.9 10.0 9.6 1.6 2.0 1.5 1.7 2.305 d 15% mssa 10.4 9.8 10.4 9.8xvvg 9.7 9.6 2.0 1.5 1.9 1.80 2.440 e 20% mssa 10.0 10.0 10.0 9.3 9.0 9.4 1.3 1.0 1.0 1.1 1.491 1ib = 1.356j 5 conclusions the following conclusions can be drawn: 1. the result of xrf pattern of mango shell ash reveals the presence of hard constituent compounds like sio2, cao, al2o3, fe2o3, mg2o. this suggests the possibility of mango seed shell ash particulate in metal matrix composite since the chemical composition has similarity with the xrf analysis of rice husk, fly ash, and bagasse ash currently used in metal matrix composite. 2. addition of mango shall ash particles to a conventional al alloy used for production of motorcycle has resulted in micro-structural changes, it shows an increase of 26.16% hardness value over the ascast al-si-mg alloy used for conventional motorcycle hub which confirms that it can be used as a reinforcement material for aluminium matrix composite. 3. the optimum hardness value was obtained at 15% wt of mssa as particulate reinforcement, similarly, the wear rate of the alloy was significantly improved at 15% wt of mssa, load of 4n, sliding speed = 10cm/s sliding distance=200m. 4. by these results, it can be concluded that mango seed shell ash can be successfully added at 15wt% as reinforcement to al-si-mg alloy for production of motorcycle hub hence providing the desired light weight, good mechanical, tribological and wear resistant properties and reducing the environmental problems created by them. references 1. aigbodion, v. s. & hassan, s. b. (2010). experimental correlations between wear rate and wear parameter of al-cu-mg/baggasse ash particulate composites. material and design, 31(4), 2177-2180. 2. adebisi, a. a., maleque, m. a. & rahman, m. m. (2011). metal matrix composite brake rotors: historical development and product life cycle analysis. international journal of automotive and mechanical engineering, 4, 471-480. 3. panchiwa, j. a., desai, d. a., & shah, p. (2015). review on quality and productivity improvement in small scale foundry industry. international journal of innovative research in science engineering and technology, 4(12), 11859-11867. 4. omotoyinbo, j. a., & oladele, i. o. (2010) effect of plastic deformation and magnesium content on mechanical property of 6063 aluminium alloys. journal of minerals and materials characterization and engineering, 9(6), 539-546. 5. kumar, s. a., & goud, r. r. (2021). processing and characterization of 6061 aluminium alloy with nickel (ni) and zirconium (zr). recent trends in mechanical engineering, 353-361. springer. 6. sears, k. (1997). automotive engineering: strategic overview. 2(1): 55–68 sumeet wadibhasme, amit ladekar and roshan paunikar hub centre steering. discovery, 24(82), 29-32. 535 (2014). ochuokpa et al. (2021). international journal of engineering materials and manufacture, 6(3), 176-186. 186 7. zhu, l., qui, f., zou, q., han, x., shu, s., yang, h., & jiang, q. (2021). multiscale design of αal, eutectic silicon and mg2si phases in al-si-mg alloy manipulated by insitu nanosized crystals. materials science and engineering, a 802, 140627. 8. ikechukwuka, n. a. (1997). characterization of aluminium alloy 2618 and its composites containing alumina particles. phd thesis, department of mechanical engineering, university of saskatchewan, saskatoon; 1-24 unpublished. 9. padmanaban, s., subramanian, r., anburaj, j, thillairajan, k. (2020). rheo-die-casting of al-si-mg/sicp composite: microstructure and wear behaviour. materials research, 23(2), 1-11. 10. adebisi, a. a., maleque, m. a. & ali, m. y. (2015). wear characteristics of multiple particle size silicon carbide reinforced aluminium composite. advanced materials research, 1115, 174-177. 11. surappa, m. k. (2003). aluminium matrix composites: challenges and opportunities, sadhana 28, parts 1 & 2, 319–334. 12. nturanabo, f., masu, l., & kirabira, j. b. (2019). novel applications of aluminium metal matrix composites. aluminium alloys and composites. 71-92. intechopen. edited by kavian omar cooke. 13. adebisi, a. a., maleque, m. a. & shah, q. h. (2014). performance assessment of aluminium composite material for automotive brake rotor. international journal of vehicle systems modelling and testing, 9(3-4), 207-217. 14. adebisi, a. a., maleque, m. a., ali, m. y. & bello, k. a. (2016). effect of variable particle size reinforcement on mechanical and wear properties of 6061 al-sicp composites. composite interfaces, 23(6), 533-547. 15. maleque, m. a., adebisi, a. a., & izzati, n. (2017). analysis of fracture mechanism for al-mg/sicp composite materials. iop conf. series: journal of materials science and engineering, 184, 012031. 16. aigbodion, v. s. (2007). particulate-strengthened of al-si alloy/alumino-silicate composite. materials science and engineering: a, 460-461, 574-578. 17. amaren, s. g. & aku, s. y. (2013). effect of periwinkle shell particle size on the wear behaviour of asbestos free brake pad. results in physics, 3, 109-114. 18. madakson p.b, yawas d.s, & apasi a. (2012). characterization of coconut shell ash for potential utilization in metal matrix composite for automobile applications. international journal of engineering science and technology, 4(3) 1190-1198. 19. ezatpour, h. r. & sajjadi, s. a. (2013). microstructure and mechanical properties of extruded al/al2o3 composite fabricated by stir casting process. transaction of nonferrous metals society of china, 23(5), 1262-1268. 20. li, x., guo, s., liu, y., du, b., & wang, l. (2017). a production planning model for make-to-order foundry flow shop with capacity constraint. mathematical problems in engineering, 6315613. https://doi.org/10.1155/2017/6315613. https://doi.org/10.1155/2017/6315613 international journal of engineering materials and manufacture (2021) 6(3) 202-208 https://doi.org/10.26776/ijemm.06.03.2021.12 s. taiga1, a. s. m. bakibillah2, k. hashikura, m. a. s. kamal1 and k. yamada1 1 graduate school of science and technology, gunma university, kiryu, japan 2 school of engineering, monash university, bandar sunway, malaysia e-mail: maskamal@gunma-u.ac.jp reference: taiga et al. (2021). a user-oriented adaptive-optimal car parking management system towards smart livings. international journal of engineering materials and manufacture, 6(3), 202-208. a user-oriented adaptive-optimal car parking management system towards smart livings sato taiga, a. s. m. bakibillah, kotaro hashikura, md abdus samad kamal and kou yamada received: 17 april 2021 accepted: 12 may 2021 published: 15 july 2020 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract existing parking management approaches do not consider specific requirements, priorities, user comfort, or modes of use when allocating a parking spot in a large park. as a result, vehicles carrying multiple passengers but staying for a limited period often have to drive further, searching for a parking spot, which increases fuel consumption, emissions, waste of time, and discomfort of users due to extra walking distance. in this paper, we consider the need for both sustainability and comfortable livings in a future smart city and propose an adaptive-optimal scheme that takes advantage of parking efficiency based on the passenger information and flexibly provides the optimal parking spot to the individual. we presume that the management system has information about the number of users, user priority, and expected stay time when a car arrives or a parking request is made. the best parking slot is assigned based on the available parking slots and the given objectives, such as the shortest travel distance inside the parking zone for a low pollution, the shortest walking distance per user, or a combination of both with some trade-off. the decision process is fine-tuned using parking data obtained from a model of a large car park of a shopping complex, and the results of the proposed scheme are compared with other schemes. the findings indicate that overall time spent in the parking lot, as well as individual walking and travel distances, have significantly improved. keywords: smart car parking, cloud computing, adaptive optimization, dynamic parking allocation, smart livings. 1 introduction in the last few decades, private cars have been the most popular mode of urban transportation. the number of cars in the world is projected to rise significantly from 841 million in 2008 to over 1.6 billion in 2035 [1]. the growing number of personal cars on the road leads to increased traffic congestion, fuel consumption, emissions, and time wastage. in addition, drivers looking for parking spaces account for about 30% of total traffic [2]. according to a global parking survey conducted by ibm in 2011, the average time spent looking for a desirable parking spot is 20 minutes [3]. in most modern cities, finding unoccupied parking spaces is a common issue as individuals arrive by car and need to visually check for vacant spaces, resulting in a large number of vehicles competing for a few available parking spaces, which causes traffic congestion in parking lots. in such situations, it becomes more difficult for vehicles to locate a vacant parking lot in a timely manner, and they are often unable to pass, even though they wish to leave the congested area. specifically, large parking lots, such as those found in shopping centres, hospitals, airports, and stadiums, are sources of time-wasting, fuel consumption, and pollution, all of which have an effect on individual users and their social lives. one of the major problems is the mismanagement of available parking spaces, which makes it difficult for users to find a parking spot in a timely manner. therefore, it is highly desirable to develop a smart car parking management system that considers individual needs and usage while providing optimal services. the primary objective of a smart car parking management system is to identify, assign, and reserve the optimal accessible car parking lot for a user driving in a specific location. in recent years, the idea of a smart city for smart livings has gained popularity in many countries. car parking facilities and traffic management systems are two of the most important concerns in smart cities [4-5], which can be resolved by intelligent transport systems (its). recent advancements in inter-vehicle communication, internet of things (iot), and sensing technologies, which share information between vehicles and roads, have allowed for improvements in parking lot navigation performance, such as comprehensive entry route guidance in large parking lots and driving route guidance before entering the parking lot [6]. inline, the cloud is an ideal partner for iot because a user-oriented adaptive-optimal car parking management system towards smart livings 203 it serves as a platform for storing and accessing sensor data from remote locations [7]. if parking information is given to drivers or cars can be dispatched automatically by interacting with them, these efforts are supposed to save a lot of time, driving distance, and walking distance. for the future smart society, various iot-based car parking systems have been proposed in the literature. in [8], an iot-based cloud-integrated smart parking system is proposed, which includes installing an iot module on-site, and tracking and communicating each parking space's availability. in [9], a cloud-based intelligent car paring service is developed for smart cities, which consists of sensors, communication systems, and devices. in [10], an automated thresholding algorithm-based approach for detecting car parking lots is proposed. due to the high cost of image processing algorithms, a hardware approach is developed. another research developed an innovative smart carparking system based on intelligent resource allocation, reservation, and pricing [11]. the new system is based on mathematical modelling using mixed-integer linear programming (milp), with the goal of lowering overall monetary costs for drivers while increasing parking resource usage. a multiagent agent system based on infostation is proposed to facilitate a car parking locator service [12]; users are provided with customized services based on their location and mobile device capabilities. some researchers suggested a new scheme that included a parking assistance service [13]. the assigned parking space will be shown on a small map using wireless transmission for cars using the dedicated short-range communication protocol dsrc when entering the car park. the car is directed to the allocated space using an inertial navigation system (ins). some other work proposed a multi-layer architecture for smart parking systems consisting of multi-parametric parking slot sensor nodes, the latest long-range low-power wireless communication technology, and edge-cloud computation [14]. the developed scheme facilitates dynamic parking management for broad areas via near real-time vehicle tracking, while providing valuable information to drivers about available parking spaces and related services. the above works did not consider individual needs, preferences, user convenience, or modes of use when allocating a parking spot in a large park. hence, vehicles carrying many passengers but staying for a limited period of time often have to drive further in search of a parking spot. consequently, parking increases fuel consumption and pollution, as well as the additional walking distance per person. in this paper, we recognize the need for both sustainability and comfortable living in a future smart city, and we propose a scheme that takes advantage of parking efficiency based on passenger information and flexibly provides the person with the best parking spot. we assume that when a car arrives or a parking request is made, the management system has details about the number of users, their priority, and the duration of their expected stay. based on the available parking slots and the given goals, the best parking slot is allocated. the findings indicate a substantial reduction in overall fuel consumption and person walking distance in the parking lot. the rest of the paper is organized as follows. section ii presents the proposed smart car parking management system, including the concept and system architecture, modelling of smart car parking, schemes for parking allocation, and car parking simulation model. section iii describes the simulation results. section iv concludes the paper. 2 smart car parking management system 2.1 concept and system architecture figure 1 illustrates the basic concept and architecture of the proposed smart car parking management system. the parking lot management system includes a system for interacting with cars as well as sensors for monitoring parking lot conditions. in order to support vehicles that do not have a communication facility, a camera for image processing and a display for guidance are installed. in this manner, the status of the parking lot is always updated on the cloud. before a car enters the parking lot from the road, the number of people in the car, the intent of their visit, the time of stay, and other information is sent to the cloud-based management system, which utilizes the information to decide optimal car parking in real-time. note that the implementation of an adaptive optimization scheme, as described in the next section, is the most important aspect of the architecture. after computation, the car near the entrance is given the id of the parking space through communication or display. the status of the parking space is transmitted to the management system via sensors when a car enters and parks in the parking lot. taiga et al. (2021): international journal of engineering materials and manufacture, 6(3), 202-208. 204 figure 1: concept and architecture of the proposed smart car parking management system. 2.2 modelling of smart car parking for the necessity of modelling the smart car parking system, we consider the parking space has a capacity of 𝑁𝑃. for each parking slot 𝑝 = 1,2, … … , 𝑁𝑃 , the optimal driving distance 𝑑𝑃 (𝑝) between the car entrance and parking point, and the optimal exit distance 𝑑𝐸 (𝑝) from the parking point to the exit are known. the walking distance 𝑑𝑊𝑎𝑙𝑘 (𝑝) from the parking point to the shopping mall entrance is also known. such information is stored in a static database of the proposed cloud-based management system. note that from the parking lot, there could be several customer entrances to the shopping center. however, we believe that people will always walk to and from their cars along the best walkway, e.g., minimum distance. on the other hand, the necessary information of each parking at time 𝑡 are stored in a dynamic database, which includes the status of the parking point given by a binary variable 𝛿𝑃 (𝑡, 𝑝) ∈ {0,1}, where 0 denotes empty and 1 denotes occupied, and the remaining expected occupancy time 𝜏𝐸 {𝑡, 𝑝} by the car. customers usually choose to park their car near the shop entrance to reduce the amount of time they have to walk and the pressure of carrying their belongings. this could be one of the objectives of the proposed system. however, assigning all cars to be parked near the shopping entrance is not feasible, and such a strategy may often result in a hotspot of pollution. to minimize pollution in a closed parking area, it is better to park in a location that decreases the travel distance inside the parking area. furthermore, cars arriving within a certain time frame should not be directed to the same parking area because they could take longer to complete the parking and waste more fuel. allocating the best spot for a car that will be parked for a long time might not be the best option for a car that will be parked for a short period of time. it is important to find appropriate parking places for each car that provide the best overall service to all, taking into account vehicle arrival trends and parking occupancy. thus, it is presumed that each car's stay period is approximately known. considering the above facts, preferences, and constraints, we minimize the following objective function by selecting the appropriate 𝑝 for each car 𝑐. 𝐽 = ∑ ∑ 𝛼𝑓𝑐𝑜𝑚𝑓𝑜𝑟𝑡 (𝑡, 𝑐, 𝑝) + (1 − 𝛼)𝑓𝑒𝑛𝑣𝑖𝑟𝑜𝑛𝑚𝑒𝑛𝑡 (𝑡, 𝑐, 𝑝), (1) 𝑁𝑐𝑎𝑟𝑠 𝑐=1 𝑁𝑑𝑎𝑦 𝑑=1 where 𝛼 is the tuning factor, 𝑓𝑐𝑜𝑚𝑓𝑜𝑟𝑡 is the cost related to the comfort of the user, and 𝑓𝑒𝑛𝑣𝑖𝑟𝑜𝑛𝑚𝑒𝑛𝑡 is the cost related to environmental aspects. the factor 𝛼 should be correctly selected by observation and fine-tuning of the parameters. in traditional optimization, factor 𝛼 is usually kept constant for all cars. however, it is preferable to find a different value of 𝛼 for each passenger, and hence, we choose an adaptive factor 𝛼 for each car that varies depending on the car users, stay time, and occupancy trends of the parking lots. the costs 𝑓𝑐𝑜𝑚𝑓𝑜𝑟𝑡 and 𝑓𝑒𝑛𝑣𝑖𝑟𝑜𝑛𝑚𝑒𝑛𝑡 are given as 𝑓𝑐𝑜𝑚𝑓𝑜𝑟𝑡 = 𝑤c2𝑑𝑊𝑎𝑙𝑘 , (2) 𝑓𝑒𝑛𝑣𝑖𝑟𝑜𝑛𝑚𝑒𝑛𝑡 = 𝑤𝑒1(𝑑𝑃 + 𝑑𝐸 ) + 𝑤𝑒2𝜌(𝑡) + 𝑤𝑒3, (3) where 𝑤c denotes the multiplying factor, 𝑤𝑒1, 𝑤𝑒2, and 𝑤𝑒3 are constant weights, and 𝜌(𝑡) is the extra complexity depending on the occupancy rate of the park. the reduction of 𝑓𝑐𝑜𝑚𝑓𝑜𝑟𝑡 may result in the least amount of walking time or distance between the car and the shop entrance, which is highly desired by users. the reduction of 𝑓𝑒𝑛𝑣𝑖𝑟𝑜𝑛𝑚𝑒𝑛𝑡 means that the car's engine runs for the shortest possible time, reducing emissions and fuel waste in the parking and a user-oriented adaptive-optimal car parking management system towards smart livings 205 contributing to clean air. therefore, the above optimization problem can be tuned for different objectives of parking management by choosing suitable 𝛼. 2.3 schemes for parking allocation for the parking allocation task, we consider several schemes with different objectives as follows. • uncontrolled scheme: as one of the baseline schemes, a parking point is randomly selected by each car. the cars are distributed at random among the available parking spaces. this approach is used as the foundation for evaluating the rest of the schemes based on the above optimization problem. • least-walk scheme: the system looks for available parking spaces near the store's entrance. this can be considered a greedy selection scheme of parking points by the users in an uncontrolled scenario. the same results can be obtained from (1) if 𝛼 is set to 1, i.e., the user's comfort is the only factor considered in the objective function. • least-travel scheme: all cars are looking for a parking spot in an available parking lot that is near to the car's entrance/exit and dispatched without regard for the user's comfort, i.e., 𝛼 is set to 0 in the objective function. since the total travel distance by a car in the parking lot can be minimum, it is also called a minimum emission parking scheme. • optimal scheme: with the trade-off for user comforts and emission reduction, the objective function is taken at a balanced condition by setting 𝛼 at 0.5. • adaptive-optimal scheme: under this scheme, the balancing factor 𝛼 is tuned dynamically, considering several factors for each car. specifically, the number of passengers of a car, intended stay time, and trend of the congestion are used to tune 𝛼 for improving the user comforts, parking utilization beyond the optimal scheme in a conventional sense while keeping the environmental aspect the same. particularly, in this scheme for each car according to its arrival context, 𝛼 is tuned as 𝛼 = { 0 for 𝜏𝐸 {𝑡, 𝑝} > 2 hr, and 𝜃(𝑡 + 𝜏𝐸 ) = 1 min(0.5 + (𝜂(𝑐) − 1)/3,1) otherwise, (4) where 𝜂(𝑐) denotes the number of passengers in car 𝑐 and 𝜃(𝑡, 𝜏𝐸 ) denotes the trend of the congestion level with 1 means peak congestion (with above 85% occupancy) is expected within the stay time of the car. if the peak times of the user arrival are known from the past data, and covering that time when a vehicle intends to stay for more than 2 hr, then 𝛼 is set to 0 according to (4). in the other cases, 𝛼 varies from 0.5 to 1.0 depending on the number of passengers in the car. in this way, the proposed adaptive optimization scheme provides the least walking park to the cars with a higher number of passengers while avoids blocking the most favourable parking point by the long-staying cars. 2.4 car parking simulation model we develop a two-dimensional model of a real parking lot, as shown in figure 2. it refers to the fourth floor of a multilevel car park with four levels. the parking lot is approximately 150 meters long and 71 meters wide, with 248 parking spaces. each parking space is assigned an id and details about its location, including the shortest distance between the car and human entrances and exits. there is one entrance and exit for cars and two entrances and exits for people. the parking space is 6.0 meters long and 2.5 meters wide, with a road width of 7 meters. there are two types of roads: one-way and two-way, which is a reference to the design standards for parking spaces in japan. buildings and other structures are shown in orange. figure 3 shows the distributions of car parks for different walking distance and driving distances. we collected approximate parking usage data for several days from 7:00 am to 11:00 pm and created a trend model for parked cars, as shown in figure 4. in the study area, the stores operate from 9:00 am to 11:00 pm. customers and store employees are the two categories of consumers, and the amount of time spent in the store, the amount of time spent in the parking lot, and the number of cars vary. figure 5 shows the histograms of cars with varying users and their stay time. though most cars come with a single user, a significant number of cars have more than one passenger. the cars stay for several hours are usually belong to the shop employees or staffs. most customer cars stay less than 1 hour, and it is expected that providing the best parking point to them could improve the overall usage of the parking lot. taiga et al. (2021): international journal of engineering materials and manufacture, 6(3), 202-208. 206 figure 2: a simulation model using a real parking lot in japan contains 248 parking points. the small yellow squares indicate an occupied parking point. (a) (b) (c) figure 3: histograms of car parks vs (a) walking distance from a parking point to the building entrance, (b) driving distance from the parking lot entrance to a parking point, and (c) driving distance from the parking point to the parking lot exit. figure 4: average car arrival patterns over hours in a day. the parking data model for several days from 7:00 am to 11:00 pm. a user-oriented adaptive-optimal car parking management system towards smart livings 207 figure 5: histograms of average users over a day, (a) the average number of passengers per car, and (b) the average stay time of the cars. 3 simulation results we consider a real parking lot as a model for implementing and evaluating the smart parking system, as illustrated in fig. 3. the simulator is built in matlab and solved a nonlinear optimization problem (described in (1)) in discrete time. the maximum walking and driving distances are about 200 m and 400 m, respectively, according to the parking area. the weight 𝑤c of cost related to the comfort of user 𝑓𝑐𝑜𝑚𝑓𝑜𝑟𝑡 is normalized by the maximum walking distance and the weight 𝑤𝑒1 of environmental cost 𝑓𝑒𝑛𝑣𝑖𝑟𝑜𝑛𝑚𝑒𝑛𝑡 is normalized by the maximum driving distance. for simplicity, weights 𝑤𝑒2 and 𝑤𝑒3 are set to zero in this study. the tuning factor 𝛼 is varied between 0 and 1. the results of each of the previously described schemes are shown. the simulation results of different control schemes are shown in figure 6(a), (b), (c), and (d). in fig. 6(a), the least-travel scheme gives the shortest driving distance, while the least-walk scheme gives the longest driving distance. the adaptive-optimal scheme has a shorter driving distance than both the optimal and uncontrolled schemes, whereas the optimal scheme has a shorter driving distance than the uncontrolled scheme. in figure 6(b), the adaptive-optimal scheme gives the shortest walking distance, while the least-travel scheme gives the longest walking distance. the optimal scheme has a shorter walking distance than the uncontrolled scheme but is longer than the least-walk scheme. the least-walk scheme in figure 6(c) provides the shortest distance between the car and building entry, while the least-travel scheme provides the longest distance. the adaptive-optimal scheme has a shorter distance between car and building entry than the uncontrolled scheme but is longer than the optimal scheme. the adaptive-optimal scheme in figure 6(d) spends the least amount of time in the park, while the uncontrolled scheme spends the most. the time spent by the optimal and least-travel schemes is equal, whereas the time spent by the least-walk scheme and the uncontrolled scheme is similar. hence, the adaptive-optimal scheme significantly improves the overall time spent in the parking lot, as well as individual walking and travel distances, compared to other schemes. figure 6: comparison of the parking schemes. taiga et al. (2021): international journal of engineering materials and manufacture, 6(3), 202-208. 208 4 conclusions in this paper, we have developed an adaptive-optimal car parking management system that takes advantage of parking efficiency based on passenger data and dynamically assigns the best parking spot to each person. we assumed that the parking management system has details about the number of users, user priority, and estimated stay time when a car arrives or a parking request is made. based on the available parking slots and the given objectives, the best parking slot is allocated. the decision-making process is fine-tuned using parking data collected over several days from a model of a large shopping complex car park, and the results are evaluated using several schemes with different objectives. the adaptive-optimal scheme is found to be successful in reducing the distance travelled and distance walked in accordance with their goals. in the future, we will consider using machine learning to forecast usage conditions, as well as data on patterns on the roads leading up to the parking lot and data on advance reservations. acknowledgement this research is partly supported by japan society of the promotion of science (jsps) grant-in-aid for scientific research (c) 20k04531. references 1. turner, b. (2011). organization of the petroleum exporting countries (opec). the statesmans yearbook: the politics, cultures and economies of the world 2012, 70-71. 2. shoup, d.c. (2006). cruising for parking. transport policy, 13(6), 479-486. 3. gallivan, s. (2011). ibm global parking survey: drivers share worldwide parking woes. technical report, ibm, new york, ny, usa. 4. barone, r. e., giuffrè, t., siniscalchi, s. m., morgano, m. a., & tesoriere, g. (2013). architecture for parking management in smart cities. iet intelligent transport systems, 8(5). 445-452. 5. bakibillah, a. s. m., paw, y. f., kamal, m. a. s., susilawati, s., & tan, c. p. (2021). an incentive based dynamic ride-sharing system for smart cities. smart cities, 4(2), 532-547. 6. handte, m., foell, s., wagner, s., kortuem, g., & marrón, p. j. (2016). an internet-of-things enabled connected navigation system for urban bus riders. ieee internet of things journal, 3(5), 735-744. 7. fox, g. c., kamburugamuve, s., & hartman, r. d. (2012). architecture and measured characteristics of a cloudbased internet of things. in proc. ieee international conference on collaboration technologies and systems (cts), 6-12. 8. khanna, a., & anand, r. (2016). iot based smart parking system. in proc. ieee international conference on internet of things and applications (iota), 266-270. 9. ji, z., ganchev, i., o'droma, m., & zhang, x. (2014). a cloud-based intelligent car parking services for smart cities. in ieee xxxith ursi general assembly and scientific symposium (ursi gass), 1-4. 10. choeychuen, k. (2013). automatic parking lot mapping for available parking space detection, in proc. ieee 5th international conference on knowledge and smart technology (kst), 117-121. 11. kotb, a. o., shen, y. c., zhu, x., & huang, y. (2015). iparker—a new smart car-parking system based on dynamic resource allocation and pricing. ieee transactions on intelligent transportation systems, 17(9), 26372647. 12. ganchev, i., o’droma, m., & meere, d. (2008). intelligent car parking locator service. international journal itk, 2, 166-173. 13. hsu, c. w., shih, m. h., huang, h. y., shiue, y. c., & huang, s. c. (2012). verification of smart guiding system to search for parking space via dsrc communication. in proc. 12th international conference on its telecommunications, 77-81. 14. sarker, v. k., gia, t. n., ben dhaou, i., & westerlund, t. (2020). smart parking system with dynamic pricing, edge-cloud computing and lora. sensors, 20(17), 4669. https://www.sciencedirect.com/science/article/abs/pii/s0013794415001149#! international journal of engineering materials and manufacture (2017) 2(4) 110-122 https://doi.org/10.26776/ijemm.02.04.2017.05 a. p. yong and m. a. islam physical and geological sciences programme faculty of science, universiti brunei darussalam jalan tungku link, gadong be1410, negara brunei darussalam n. hasan petroleum and chemical engineering programme area universiti teknologi brunei, tungku highway, gadong be1410 negara brunei darussalam e-mail: nurulhasan@asme.org reference: yong, a. p., islam, m. a., and hasan, n. (2017). the effect of ph and high-pressure homogenization on droplet size. international journal of engineering materials and manufacture, 2(4), 110-122. the effect of ph and high-pressure homogenization on droplet size ah pis yong, md. aminul islam and nurul hasan received: 20 october 2017 accepted: 13 november 2017 published: 10 december 2017 publisher: deer hill publications © 2017 the author(s) creative commons: cc by 4.0 abstract this study aims to revisit the effect of high pressure on homogenization and the influence of ph on the emulsion droplet sizes. the high-pressure homogenization (hph) involves two stages of processing, where the first stage involves in blending the coarse emulsion by a blender, and the second stage requires disruption of the coarse emulsion into smaller droplets by a high-pressure homogenizer. the pressure range in this review is in between 10-500 mpa. the homogenised droplet sizes can be reduced by increasing the homogenization recirculation, and there is a threshold point beyond that by applying pressure only, the size cannot be further reduced. normally, homogenised emulsions are classified by their degree of kinetic stability. dispersed phase present in the form of droplets while continuous phase also known as suspended droplets. with a proper homogenization recirculation and pressure, a more kinetically stable emulsion can be produced. the side effects of increasing homogenization pressure are that it can cause overprocessing of the emulsion droplets where the droplet sizes become larger rather than the expected smaller size. this can cause kinetic instability in the emulsion. the droplet size is usually measured by dynamic light scattering or by laser light scattering technique. the type of samples used in this reviews are such as chocolate and vanilla based powders; mean droplet sizes samples; basil oil; tomato; lupin protein; oil; skim milk, soymilk; coconut milk; tomato homogenate; corn; egg-yolk, rapeseed and sunflower; poly(4-vinylpyridine)/silica; and complex 1 until complex 4 approaches from author case study. a relationship is developed between emulsion size and ph. results clearly show that lower ph offers smaller droplet of emulsion and the opposite occurs when the ph is increased. keywords: high-pressure homogenization, the effect of ph, stable emulsion. 1 introduction homogenizer has been used in the industry such as for pharmaceuticals, food and dairy industry, petroleum and chemical [1, 2]. one of the reasons why a homogenizer has become very popular is due to its recent improvements in the design of using high pressure to improve the emulsion characteristics such as improved stability and smaller droplet sizes. a piston pump in hph can create pressure up to 500 mpa, and the emulsion from hph is usually allowed to accelerate to high velocities through a narrow-gap valve which then can help to increases velocity of the fluid and may result in depressurization with consequent high shear stress and cavitation [3-5]. in other words, the emulsions that are passing through hph are going to become twisted and deformed due to high mechanical stress exposure [6-8]. in comparison with conventional homogenization (pressure: 20 to 50 mpa), hph allows room for improvement where hph helps to improve the quality aspects, such as improved the stability of the emulsion and microbial and enzymatic inactivation [5, 9, 10]. the increased pressure level can help to improve the products by reducing creaming rate and become more stable [11]. also, peng, dong [12] stated that either surfactant or high energy are needed for the emulsion to have a narrow size distribution and very small droplet sizes. usually, hph can reduce the size of globules to less than 1 μm and recently, hph can achieve pressures that exceeding more than 200 mpa [2]. for example, as the study made by park, min [5], the author is using a laboratory-scale hph (m-110y, yong et al., (2017): international journal of engineering materials and manufacture, 2(4), 110-122 111 microfluidics, usa) on the chocolate and vanilla powder emulsions with processing pressure ranging from 20 to 150 mpa. the average droplet sizes for the chocolate and vanilla-powder emulsions at a low homogenising pressure of 20 mpa are 5.91 and 2.44 μm , respectively [5]. the average droplet sizes for the chocolate and vanilla-powder emulsions at a medium homogenising pressure of 60 mpa are 5.52 and 2.38 μm , respectively [5]. the average droplet sizes for the chocolate and vanilla-powder emulsions at a high homogenising pressure of 100 mpa are 5.11 and 2.48 μm , respectively [5]. another example which is made by kubo, augusto [4] where the author is using hph (panda plus, gea niro soavi, italy) on tomato juice emulsions at pressures ranging from 0 to 100 mpa. the average droplet sizes for the tomato juice emulsion at a low homogenizing pressure of 25 mpa is 74.1 μm , while at a medium homogenizing pressure of 50 mpa is 41.1 μm , and lastly, at the high homogenizing pressure of 100 mpa, the average droplet sizes for tomato juice emulsion is 41.1 μm [4]. from both of the examples describes above which uses different homogenizer types shows that at different homogenising pressure, the average droplet sizes for different emulsion are different but still the droplet sizes did reduce much further when very high homogenising pressure is applied. however, for the tomato juice emulsion at medium (50 mpa) and high (100 mpa), homogenising pressure show that the average droplet sizes are the same which is probably due to overpressure (overprocessing) applied on the tomato juice. this effects still need to be considered in the study. in an emulsion, the size of the droplet and the size distribution of the droplet must be improved by reducing its size and distribution where this can enhance stability, solubility, reaction intensity and mouthfeel [1, 5]. the emulsions that have smaller particles with higher protein solubility in dairy products can efficiently be created by using hph [1, 5]. hph also offers a smaller size of emulsions when the homogenizing time is increased. using the homogenising pressure of 100 mpa for 90 minutes can provide nano-sized emulsions [13]. hph mechanically reduces the size of globules to less than 1 μm and is used to produce an emulsion of uniform composition and higher stability [2]. for processing using hph, as stated it usually involves two stages. the first stage is by using a blender such as rotor-stator blender to blend the coarse emulsions and then the second stage is to disrupt the coarse emulsions into smaller droplet sizes. to reduce the droplet size much further, the homogenization process or recirculation can be increased. thus it depends on the characteristics of the materials and machines used. usually, the samples which are homogenised will be passed through a coil that is cooled by an ice mixture, and this can help it to cool down [5]. the droplet sizes of the emulsion can be measured by using the dynamic light scattering (dls) or by laser-light scattering technique [14, 15]. other techniques that can be used to measure the droplet sizes are such as optical microscopy [1], photon correlation spectroscopy [2] and direct video imaging [16]. the droplet size of the emulsion also can be stated as the volume-weighted diameter by eq (1) and as droplet size distribution, where in is the number of particles of diameter id [5]. the sauter mean diameter also can be used to calculate the droplet size [17]. it can be defined as eq (2), where n is the number of droplets between two consecutive diameters and id is the droplet diameter. the polydispersity index (pi) as defined as the ratio of weight average molecular weight to number average molecular weight (eq (3)). the state of emulsion size distribution can be indicated by using pi, and usually a particle size distribution of the emulsion which is more concentrated can be indicated from smaller pi [12]. both the average droplet sizes and pi are required to reflect the average emulsion particle size [12]. pi also can be expressed as eq (3), where pi is defined as the ratio of w n m /m [18]. w m is the molecular weight distribution that places a greater emphasis on larger molecules than that of smaller molecules in the distribution. n m refers to the average molecular weight of the molecules in the polymer. with the addition of ph and emulsifiers in the emulsions can help to affect the droplet sizes of the emulsions too. based on the study made by yin, zhang [19] by using four complex approaches used indicating a change in ph affects the droplet sizes. the four complex approaches will be explained later in the discussion. at lower ph (acidic), the four complex approaches for the emulsion have longer stability against the changes of different nacl concentration and ph due to smaller droplet sizes [19]. the equipment involves the homogenization process are such as ultra turraxx model [20], laboratory-scale hph (microfluidics) [5], niro-soavi panda two-stage homogenizer [21] and some others. in this study, the model used to measure the droplet sizes are such as mastersizer instrument [22] and zetasizer nano-zs90 [19]. the materials covered are soybean oil, medium chain triglyceride (mct) [12]; chocolate and vanilla-based products [5]; basil oil [23]; coconut milk [24]; soy milk [9]; lupin protein [1]; tomato [6]; and skim milk [25]. to control the ph, the materials used are pea protein isolate (ppi), soybean soluble polysaccharide (ssps) [19]; poly(4-vinylpyridine)/silica (p4vp/ 2sio ) nanocomposite microgel [20]; sunflower, rapeseed and egg-yolk lecithin [26]; corn o/w emulsion stabilized with silk fibroin [27]; and whey protein microgels (wpm) [28]. generally, the samples used in this reviews are such as chocolate and vanilla based powders; mean droplet sizes samples; basil oil; tomato; lupin protein; oil; skim milk, soymilk; coconut milk; tomato homogenate; corn; egg-yolk, rapeseed and sunflower; poly(4-vinylpyridine)/silica; and complex 1 until complex 4 approaches from author case study. this review is carried out to understand the effect of the different pressure of hph on droplet sizes on different materials and the influence of different ph value on the droplet sizes which can affect its sizes. some related issue like the stability of emulsions and temperature effect on emulsion will not be covered here. the storage time which can the effect of ph and high-pressure homogenization on droplet size 112 affect the droplet size is mentioned here in brief. also, the relationship between viscosity and shear rate will be discussed here in relation with the hph on droplet sizes. this outcome can be used for the industries for references. 2 models ∑ = ∑ 4 43 3 i i i i i i n d d n d (1) ∑ = ∑ 3 32 2 i i i i nd d nd (2) w n m pi= m (3) − − =3 4 (pa) ( ) 10 (s) p e wm (4) > 12 -310 wme (5) τ γ= nk (6) γµ (a log( )+b)=e (7) ( ) ( ) ( )2 3d =a+b +c +dh h hi p p p (8) 3 results and discussions figure 1 shows emulsion droplet size with pressure for four emulsions, namely, chocolate, vanilla, mds and basil oil studied by [5, 12, 23]. as can be seen from the figure 1, the particle size in chocolate-based emulsion decreases as the pressure increases. at 100 mpa, the chocolate-based emulsion has 5.12 µm mean particle size, which decreases from 29.01 µm [5]. majzoobi et al. (2013) stated that hph creates a high turbulence and shear, united with compression, acceleration, pressure drop and impact, broke down the particles and dispersed them all over the product [5]. it is efficient for the droplet sizes to be reduced at an elevated pressure of hph [5, 29-31]. the vanilla-based emulsion droplet size also decreased by hph from 4.18 μm (control) to 2.44 μm (20 mpa) as shown in figure 1. increasing the pressure higher is unable to decrease the particle size due to its tiny initial particle which is smaller than chocolate-based emulsion (figure 1). while for the mds, the initial data already has the smallest particle size compare to chocolateand vanilla-based. the mds has shown that as the hph increased from 40 to 130 mpa, the particle size remains smaller without a noticeable change in size. for the basil oil (figure 1), it shows that increasing the hph up to 50 mpa will decrease the emulsion droplet size. figure 1: mean particle size of chocolateand vanilla-based products subjected to high-pressure homogenization (20– 100 mpa), mds value subjected to 40-130 mpa hph and basil oil subjected to 0-100 mpa hph [5, 12, 23]. yong et al., (2017): international journal of engineering materials and manufacture, 2(4), 110-122 113 this is probably due to the amount of energy used is quite high which then helps to break the emulsion droplets. however, as the use of pressure increased above 85 mpa, it causes the droplets formations with the larger size. this phenomenon is the same as previous study before for mds where it is because of over processing. figure 2 shows the particle size distribution of the control products which is before the hph treatment applied. based on the volume distribution shown (figure 2), the tomato has the highest peak of the volume distribution followed by lupin protein, chocolate, and vanilla-based products. for tomato, the highest volume distribution is between 210 and 310 μm . lupin protein has the highest distribution between 110 and 210 μm . in the chocolate and vanilla-based emulsion, the control products have from small to large size distribution. for the lupin protein, it has a unimodal distribution of the unprocessed solution with aggregates of proteins bigger than 1 μm . after hph treatment had applied (figure 3) at the smaller droplet sizes with a bimodal distribution of chocolate and vanilla-based products, peaks were observed. this means that hph causes a smaller particle sizes distribution. overall, at the different pressure, the particle size distributions were not significantly different. for the tomato-based products, as 25 mpa hph applied, there is an increasing particle size distribution between 750 to 900 μm (figure 3). this means that for tomato-based products, as the pressure increases, the droplet sizes also reduced. for lupin protein (figure 3), an increase up to 50 mpa homogenization pressure causing the movement in the size distribution on the way to smaller groups of 0.1 to 10 μm. at 100 mpa, for lupin protein (figure 4) the particle size distribution was similar to that at 50 mpa (figure 3). at 150 mpa, the combinations of bigger formations with sizes of up to 100 μm was stimulated. figure 5 shows that emulsions that have a high percentage of oil will have larger mean droplet sizes for the same homogenising conditions. this occurrence may be due to the limitations of the surface-active agents in the oil concentrated emulsions. the proteins decrease when the oil content increases, causing in reducing stability in the proteins, which can cause coalescence in the oil droplets and larger droplet sizes [11]. figure 5 shows the particle size distribution of skim milk measured using integrated light scattering [25]. it shows that raw skim milk that is not homogenised shows a monomodal distribution of sizes around 0.120 μm of the average diameter. this is likely as casein micelles are present in skim milk [25]. for the homogenised skim milk and homogenised skim milk with added tween samples show a bimodal distribution curve, with fat globules sizes of about 1.2 μm of diameter [25]. in the presence of tween, the sizes of the particles reduced. for the skim milk, after homogenization pressure is applied, it shows a reduction in droplet sizes. figure 6 shows the mean droplet diameter measured as 32d against oil mass fraction or concentration for the emulsion containing whey protein concentrates and sunflower oil. from figure 6, oil concentrations increase, a greater mean droplet diameter found for similar homogenising conditions. figure 6 also shows the changes in mean droplet size 32d and 43d of emulsions as a function of supercritical fluid extracts (sfe) concentrations. the line for each data was drawn based on the power fit curved line [11, 33]. as the oil concentration increases (figure 6), a high pressure is needed to reduce the droplet size. in this study, 300 mpa is an ideal pressure for higher oil concentration of 50 %. figure 2: particle size distribution of the control (0 mpa) based products of chocolateand vanilla-based products, tomato and lupin protein [1, 5, 6]. the effect of ph and high-pressure homogenization on droplet size 114 figure 3: particle size distribution of chocolateand vanilla-based products, tomato and lupin protein subjected to 20-50 mpa [1, 5, 6]. figure 4: particle size distribution of chocolateand vanilla-based products, tomato and lupin protein subjected to 70-150 mpa [1, 5, 6]. in figure 6, it also shows the changes in mean droplet size ( )32 43d , d of emulsions containing 0.1 to 0.9 weight % of sfe extracts, 10 weight % of oil and 20 mm bis-tris with ph =7.0 against sfe concentration. [33]. for this emulsion, it was homogenised at 20.7 mpa, and then the final emulsion was homogenised at 3.4 mpa. the droplet particle size for 32 43d and d also can be expressed as eq (1) and eq (2). according to figure 6, the 32d mean droplet sizes were reduced from 0.90 μm (0.1 weight %) to 0.47 μm (0.9 weight %) as the sfe concentrations increase. when adding more than 0.5 weight % emulsion ( )43d , the size of the fat globules did not show significant changes compare with 32d except that their droplet size becomes a bit larger. yong et al., (2017): international journal of engineering materials and manufacture, 2(4), 110-122 115 figure 5: effect of oil concentration (10% and 50%) on o/w emulsion homogenized at 150 mpa and skim milk (raw, homogenized and homogenized with tween at 34.5 mpa) on their droplet size distribution [11, 25]. figure 6: mean droplet size in emulsions homogenized at 20, 150 and 300 mpa against oil concentration in percentage (%) [11, 33]. however as the concentration of sfe increased, the droplet sizes for 43d is also reduced. for this study, as the emulsion concentration increases, the droplet sizes reduce even though the emulsion is homogenised at 20.7 mpa. for the study of an emulsion containing whey protein concentrates and sunflower oil, as the oil concentrations increase, the droplet sizes are larger with lower homogenising pressure (20 mpa). however, if the 300 mpa homogenising pressure was used, the emulsion droplet size containing more than 50 % oil concentrations can be reduced. figure 7 shows the volume % of the various size of droplets vs. droplet size for few emulsions namely, chocolate, vanila, oil, and tomato. as can be seen in figure 7, the mean droplet diameters and the droplet size distributions are different for all the emulsions considered. the peak volume percentage for oil decreases as the oil % drops from 50 to 10 and same goes for peak particle diameter. compared to different materials from tomato, chocolate and vanilla based products subjected to 25 and 20 mpa respectively, oil with 50 % concentration has the highest volume distribution peak. this is followed by vanilla based with its peak at the smallest diameter range in between 20 and 80 μm and tomato with its peak distribution at 800 μm . figure 8 shows the particle size distribution of oil with 10 and 50 % concentration subjected to 150 and 300 mpa compared with other materials, namely, lupin protein, tomato and soymilk subjected to 150, 200 and 300 mpa respectively. at 300 mpa homogenization pressure, the effect of ph and high-pressure homogenization on droplet size 116 a broad tail appears in the particle size distribution. this is probably due to the emulsion created has very small droplet sizes, and then recoalescence may occur in the homogenization chamber. since 300 mpa is a very high pressure, it may cause a very great impact on the rheology of the emulsions. at 300 mpa hph for oil with a concentration of 10 and 50% (figure 8), the emulsion usually gets exposed to shear stress which is high and temperature in the homogenizing valve, where this can cause the emulsified proteins become too denatured to play their stabilizing role, [11]. while for the soymilk products homogenized at 200 and 300 mpa (figure 8) shows that the samples homogenized at 300 mpa showed a larger mean diameter compared to 200 mpa, which indicates that there is a presence of droplets aggregates. in general, a 200 mpa treatment for soymilk samples gave the narrower range in the size distribution of particles compared with a 300 mpa treatment of oil concentration and soymilk samples. viscosities vs. shear rate for various materials are shown in figure 9 on a log-log scale. also, the investigation has confirmed that at hph at very high pressure can help to reduce the viscosity of the solutions (figure 9). in figure 9 data is mostly fitted to power fit curve and it can be defined by eq (7), with the value of a and b coefficients are different with different homogenizing pressure and materials (table 1). this relationship would offer a thumb rule for industrial application. in the rheometer, at high shear rates, the apparent viscosity can reach a constant value either because only single droplets persist or the number of flocculated droplets remains constant since the rate of floc formation is equal to that of floc disruption as mentioned by [34] stated in [11]. figure 7: effect of homogenizing pressure conditions of 20 mpa on droplet size distributions of 10% and 50% oil concentration of o/w emulsions, tomato based at 25 mpa, chocolate and vanilla based products at 20 mpa [5, 6, 11]. table 1: sample of coconut milk, oil with 50% mass fraction and tomato homogenate with different pressure and a and b coefficients obtained from equation (7) and data obtained from [11, 24, 36]. sample name mpa a coefficient b coefficient tomato homogenate 0.1 -9.0630e-001 1.8094e+000 coconut milk 15 -1.3839e-001 -2.8813e+000 oil (50% concentration) 20 -6.2336e-001 1.3023+000 coconut milk 21 -2.0559e-001 -2.3158e+000 coconut milk 27 -1.8732e-001 -1.9518e+000 tomato homogenate 100 -8.2382e-001 1.5560e+000 oil (50% concentration) 150 -6.0674e-001 9.1073e-001 oil (50% concentration) 300 -1.3103e-001 -3.2675e+000 tomato homogenate 300 -8.2851e-001 1.3619e+000 tomato homogenate 500 -8.9900e-001 2.2522e+000 yong et al., (2017): international journal of engineering materials and manufacture, 2(4), 110-122 117 figure 8: effect of homogenizing pressure conditions of 50-300 mpa on droplet size distributions of 10% and 50% oil concentration of o/w emulsions, tomato based, lupin protein and soymilk products [1, 6, 9, 11]. figure 9: effect of homogenizing pressure on rheological properties of emulsions: viscosity vs. shear rate of 50% mass fraction of o/w emulsions homogenized at three different pressures: 20, 150 and 300 mpa, the coconut milk at three different pressures: 15, 21 and 27 mpa and tomato homogenate after treatment for 15 min at 30 ºc combined with four different pressures: 0.1, 100, 300 and 500 mpa [11, 24, 36]. with high pressure, lowest viscosity can be achieved. this is due to in the homogenising valve, it has high shear stress and energy density, where at high pressure, the flocculation droplet will not be able to occur at the homogenizer exit, so a smaller and fine droplet size can be produced. the energy can be expressed as eq (4) and eq (5). as can be seen from figure 9, with high pressure, lowest viscosity can be achieved. figure 9 shows the plot of homogenised coconut milk which contains apparent viscosity against shear rate at five levels pressure different [24]. power law model was used on the samples to define the rheological behaviour [24]. the model was defined in the eq (6) where τ is the shear stress, γ is the shear rate, k is the consistency index (pa sn ) and n is the flow behaviour index. the the effect of ph and high-pressure homogenization on droplet size 118 apparent viscosity decreases with increasing shear rate for the homogenised coconut milk during the early stage. the apparent viscosity changed slightly after a sharp reduction to become steady at rates of higher shear. as the pressure level increased, it allows the droplets size reduction (figure 9). this means that in the colloidal system, there are large numbers of droplet presented and blocked the flow. the increase of apparent viscosity is due to high pressure. after passing thru higher pressure, the emulsion becomes more viscous. at all homogenising pressures, coconut milk which is characterised by n values less than 1 showed power-law pseudoplastic behaviour. there is no communication between particles as the emulsions display low viscosity with newtonian flow behaviour at low homogenising pressure [24]. torres et al., (2007) stated that the k values are related to the viscosity, and the flow behaviour index ( n ) provided information about the effects of shear on the system [35]. also, the effects of applying different homogenising pressures obtained with rheometer after treatment on the tomato homogenate for 15 min at 30 ºc are also shown in figure 9. the curves for tomato homogenate at atmospheric pressure (0.1 mpa) shows that the value of viscosity decreased with shear rate getting higher which indicate that tomato homogenate displays pseudoplastic flow behaviour [36]. this result is the same with all other given pressures (100, 300 and 500 mpa) of tomato homogenate. for the tomato homogenate treated at 500 mpa showed the highest viscosity and the sample treated at 300 mpa have the lowest viscosity. the ph can have a significant effect on the size of the emulsion droplets. table 2 shows the pea protein isolate (ppi) in preparation condition which is utilised to build complexes of soluble soybean polysaccharide (ssps) [19]. the homogenization pressure used for ppi study is 85 mpa. as can be seen from table 2, in the ppi study, there are four complex approaches that were used. the complex 1 is the mixture of ppi and ssps at ph 3.25 [19]. complex 2 is by mixing centrifuged ppi at 6800 g with ssps at ph 3.25 [19]. complex 3 is the mixture of centrifuged ppi at 2790 g and ssps at neutral ph and then adjusting to ph 3.75 [19]. lastly for complex 4 is the mixture of ppi and ssps at neutral ph and then modifying to ph 3.75 [19]. for the ppi and ssps study, there are four complex approaches that were used; they are complex1 until complex4 [19]. the preparation condition can be seen in table 2. for the study based on 2 p4vp/sio , out of three protocol in the study, only one is used that is protocol 1. equivalent quantities of oil and an aqueous dispersion of different ph values are found in a batch of an emulsion of protocol 1, which are place at room temperature [20]. in a thermostat bath of 20 °c, the two phases were kept to be homogenised at 13000 rpm with ultra turrax t25 homogenizer for two minutes at 20 °c [20]. in table 3, after homogenization treatment, the four complex approaches in this study display similar particle size of about 200 nm (measured as hd , hydrodynamic diameter), which size is much smaller compared to the particles prior homogenization. the diameter for the mixed ppi at ph 3.25 (complex 1) shows the largest droplet sizes before homogenization treatment was applied with the pi also highest among the other three complexes. after homogenization treatment was applied, roughly the droplet sizes are almost the same as about 200 nm, but the pi values are different. based on the result in table 3 above, it might indicate that with hph applied within the range of ph in between 3.0 and 4.0, it can cause the droplet sizes to be reduced. for the egg-yolk lecithin, rapeseed, and sunflower, the ph value for each substance was adjusted to ph =8.0 [26] (table 3). as demonstrated in table 3, hph reduced the droplet sizes in nanoemulsions comprising rapeseed (296 ± 18 nm), sunflower lecithin (417 ± 25 nm) and the control egg-yolk lecithin emulsions (243 ± 12 nm). these emulsions were visually ph stable for at least one months [26]. table 2: preparation conditions of materials used [19, 20, 26, 27]. sample preparation condition ssps ph 7.0 or ph 3.25 ppi ph 6.8 ppi1 adjusting ppi to ph 3.25 ppi2 centrifuging ppi1 at 6800 g ppi3 centrifuging ppi at 2790 g and then adjusting ph to 7.0 ppi4 adjusting ppi to ph 7.0 complex1 mixing ppi1 with ssps at ph 3.25 complex2 mixing ppi2 with ssps at ph 3.25 complex3 mixing ppi3 with ssps at ph 7.0 and then adjusting ph to 3.5 complex4 mixing ppi4 with ssps at ph 7.0 and then adjusting ph to 3.5 corn silk fibroin was used to prepare 10 % (by mass) corn o/w emulsions at ambient temperature by adjusting the ph to 7.0 using 1 m hcl or 1 m naoh 2p4vp/sio prepared by using batch emulsion containing equal volumes (5.0 ml) of oil and aqueous dispersion at different ph values or salt concentrations egg-yolk lecithin, rapeseed, sunflower the samples prepared by hph and the ph value of all formulations was adjusted to ph 8.0 with 0.01 -1moll naoh solution. yong et al., (2017): international journal of engineering materials and manufacture, 2(4), 110-122 119 in table 3 also shows the results of corn o/w emulsions droplet sizes decreased about 470 nm as the mass fraction of silk fibroin increased up to 1 % (by mass). the corn oil emulsion was acclimatised to ph 7.0 [27]. figure 10 can be obtained by using eq (8). the data in figure 10 was fitted to polynomial curve fitting with third order. the a, b, c, and d are constant, and the value is different from each material (table 4). homogenised egg-yolk lecithin, rapeseed, and sunflower with the added of 1 m nacl solution at various ph values are shown. it is shown that silk fibroin (1% by mass) stabilized with corn o/w emulsion of mean particle size. figure 10 shows the average drop diameters arithmetic mean and median diameter for o/w emulsion of p4vp/sio2 particles (freshly set emulsion) as a function of ph using batch emulsion where sizes are determined using light diffraction. in the ranges of 3-5 μm is the mean standard deviation. at around ph 5-6, a different narrow minimum happens. at around ph 5-6, the droplet sizes are smaller compared to the others. the apparently measured diameter is greater than the individual drops if in dilution the flow is stable. for the corn o/w emulsions, the mean particle diameter ( 32 d ) continued moderately small (<1 mm) from ph = 2.0 to 8.0 except at ph =4.0, representing that tiny aggregation of droplet happened during packing. silk fibroin-stabilized emulsions suggested being remained stable to droplet aggregation [27]. in figure 10, the study of egg-yolk lecithin, rapeseed, and sunflower by [26] are also shown. figure 10 shows that among the three samples, egg-yolk lecithin has the smallest sizes. in general, the samples for egg-yolk lecithin does not have any significant changes in droplet sizes as the ph value moves from ph 2.0 to ph 8.0. for the rapeseed samples, it shows droplet sizes change from about 300 nm or 0.300 μm to about 400 nm or 0.400 μm from ph 2.0 to ph 8.0 respectively. for the rapeseed, samples homogenised with ph above 7.0 show larger droplet sizes. while for the sunflower samples, the smallest droplet sizes about 500 nm or 0.500 μm were observed at ph 2.0 and 5. at ph 4.0, it shows the largest droplet sizes for sunflower samples about 620 nm or 0.620 μm . in general, different ph media will give different droplet sizes, and it also depends on the materials of the homogenised samples. freshly prepared complex 1 (mixed ppi at ph 3.25) and complex 2 (mixed centrifuged ppi at ph 3.25) emulsions, which have 285 and 269 nm of droplet sizes(figure 10), correspondingly, were accustomed to ph 5 and 6, and to 0.2 m nacl concentration was added, and to investigate the long-term stability the emulsions were stored at 4 °c [19]. after 85 days of storage (figure 10), at ph 3.25, in emulsions kept at ph 5 and 6, an increase of droplet sizes and a whey layer were discovered. meanwhile, emulsions reserved at ph 5 and six which contains 0.2 m nacl shows creaming. complex 2 emulsions (figure 10) stay homogeneous with or without the involvement of 0.2 m nacl after 87 days of storage suggests that compared to complex 1 emulsions, complex 2 emulsions are more stabilised. based on this result, it can be assumed that the change of ph value can affect the droplet size, but it also depends on the characteristics of the materials. table 3: droplet sizes after homogenization of different samples [19, 26, 37]. sample without homogenization after homogenization droplet size (nm) pi droplet size (nm) pi complex 1 1555 ± 455 1.0 213 ± 9 0.65 ± 0.04 complex 2 412 ± 18 0.48 ± 0.04 192 ± 4 0.44 ± 0.03 complex 3 580 ± 42 0.36 ± 0.03 195 ± 8 0.49 ± 0.03 complex 4 744 ± 88 0.57 ± 0.03 218 ± 9 0.72 ± 0.02 egg-yolk lecithin 243 ± 12 0.08 ± 0.04 rapeseed 296 ± 8 0.28 ± 0.08 sunflower 417 ± 25 0.44 ± 0.14 corn 470 ± 50 table 4: list of various a, b, c and d coefficients for eq (8) and the data obtained from [20, 26, 27]. samples a-coeffiecient b-coefficient c-coefficient d-coefficient 2p4vp/sio (median diameter) 1.08e+002 -9.01e+000 1.51e-001 8.37e-002 2p4vp/sio (arithmetic mean diameter) 1.06e+002 -3.99e+000 -9.58e-001 1.57e-001 corn -5.17e+000 4.2775e+000 -8.45e-001 4.97e-002 egg-yolk 3.02e-002 -2.58e-003 5.93e-004 -3.81e-005 rapeseed 8.73e-003 4.77e-003 -6.0e-004 -5.17e-011 sunflower 1.01e-002 -5.22e-003 1.0e-003 -6.53e-005 fresh prepared complex 1 2.31e-001 3.77e-002 -9.16e-003 8.91e-004 fresh prepared complex 2 3.58e-001 -3.57e-002 3.43e-003 1.63e-004 the effect of ph and high-pressure homogenization on droplet size 120 figure 10: average drop diameters of the arithmetic mean and median diameter for o/w emulsions as a function of ph for freshly prepared emulsions using batch emulsion [20, 26, 27]. 4 conclusions 1. based on the reviewed study, a high-pressure homogenization can effectively reduce the droplet sizes of the emulsions from coarse emulsion into smaller droplets. this indicates that with proper homogenization recirculation and pressure, a stable emulsion with reduced droplet size can be produced. however, at some point this depends on the emulsion characteristics, with increased high pressure too, some emulsion will not be able to be reduced any further sizes. the side effects of increasing homogenization pressure are that it can cause overprocessing of the emulsion droplets where the droplets size become larger rather than the smaller expected size. this can cause instability in the emulsion. 2. there are few solid contributions to this investigation: 3. the diameter of emulsions can be expressed as a fourth order polynomial of ph ( ( ) ( ) ( )2 3d =a+b +c +dh h hi p p p ) the coefficients of seven emulsions are derived from the experimental data. 4. viscosity can be expressed as a logarithmic function of shear rate ( γµ (a log( )+b)=e ) and shear rate is dependent on the shear stress. the coefficients for few emulsions are calculated from the experimental results. acknowledgement this research was funded by moe for the scholarship of the postgrad student. the authors are grateful to the utb library and ubd laboratory, yong et al., (2017): international journal of engineering materials and manufacture, 2(4), 110-122 121 list of symbols symbols meaning ni id 32 d 43 d h d dls e hph k mct mds n o/w p p4vp/sio2 pi ppi sfe ssps τ tem tw-20 γ µ number of particles of diameter diameter ( μm ) sauter mean diameter ( μm ) volume weighted diameter ( μm ) hydrodynamic diameter (nm) dynamic light scattering energy ( -3wm ) high-pressure homogenization consistency index ( )npa.s medium chain triglyceride mean droplet size flow behaviour index oil in water pressure (pa) poly(4-vinylpyridine)/silica polydispersity index pea protein isolate supercritical fluid extracts soybean soluble polysaccharide shear stress (n/m2) transmission electron microscopy tween 20 shear rate (1/s) viscosity (kg/m/s) references 1. bader, s., bez, j. & eisner, p. (2011). can protein functionalities be enhanced by high-pressure homogenization?– a study on functional properties of lupin proteins. procedia food science, 1:1359-366. 2. lee, s-h., lefèvre. t., subirade, m. & paquin, p. (2009). effects of ultra-high pressure homogenization on the properties and structure of interfacial protein layer in whey protein-stabilized emulsion. food chemistry, 113, 191-195. 3. innings, f. & trägårdh, c. (2007). analysis of the flow field in a high-pressure homogenizer. experimental thermal and fluid science, 32,345-354. 4. kubo, m.t.k., augusto, p. e. & cristianini, m. (2013). effect of high pressure homogenization (hph) on the physical stability of tomato juice. food research international, 51,170-179. 5. park, s. h., min, s. g., jo, y. j. & chun, j. y. (2015). effect of high pressure homogenization on the physicochemical properties of natural plant-based model emulsion applicable for dairy products. korean j food sci anim resour, 35, 630-637. 6. augusto, p. e., ibarz, a. & cristianini, m. (2012). effect of high pressure homogenization (hph) on the rheological properties of tomato juice: time-dependent and steady-state shear. journal of food engineering, 111,570-579. 7. floury, j., bellettre, j., legrand, j. & desrumaux, a. (2004). analysis of a new type of high pressure homogeniser: a study of the flow pattern. chemical engineering science, 59, 843-853. 8. pinho, c. r. g., franchi, m. a., augusto, p. e. d. & cristianini, m. (2011). evaluation of skimmed milk flow during high pressure homogenization (hph) using computational fluid dynamics (cfd). brazilian journal of food technology, 14, 232-240. 9. cruz, n., capellas, m,. hernández, m., trujillo, a., guamis, b. & ferragut, v. (2007). ultra high pressure homogenization of soymilk: microbiological, physicochemical and microstructural characteristics. food research international, 40, 725-732. 10. poliseli-scopel, f. h., hernández-herrero, m., guamis, b. & ferragut, v. (2013). characteristics of soymilk pasteurized by ultra high pressure homogenization (uhph) (2013). innovative food science & emerging technologies, 20,73-80. 11. floury, j., desrumaux, a. & lardieres, j. (2000). effect of high-pressure homogenization on droplet size distributions and rheological properties of model oil-in-water emulsions. innovative food science & emerging technologies, 1, 127-134. the effect of ph and high-pressure homogenization on droplet size 122 12. peng, j., dong, w-j., li, l., xu, j-m., jin, d-j., xia, x-j. & liu, y-l. (2015). effect of high-pressure homogenization preparation on mean globule size and large-diameter tail of oil-in-water injectable emulsions. journal of food and drug analysis, 23, 828-835. 13. burapapadh,k., takeuchi, h., sriamornsak p. (2012). pectin-based nano-sized emulsions prepared by highpressure homogenization. advanced materials research; 506, 286-289. 14. farshchi, a., ettelaie, r. & holmes, m. (2013). influence of ph value and locust bean gum concentration on the stability of sodium caseinate-stabilized emulsions. food hydrocolloids, 32,402-411. 15. ishikawa, a., fujii, m., morimoto, k., yamada, t., koizumi, n., kondoh, m. & watanabe, y. (2012). oil-inwater emulsion lotion providing controlled release using 2-methacryloyloxyethyl phosphorylcholine n-butyl methacrylate copolymer as emulsifier. results in pharma sciences, 2, 16-22. 16. hacıoğlu, r., genç, a. & bakırcı, b. (2013). evaluation of droplet sizes from video images for metal working fluids. international journal of environmental and ecological engineering, 7, 757-761. 17. jurado, e., bravo, v., camacho, f. & vicaria, j. m. & fernández-arteaga, a. (2007). estimation of the distribution of droplet size, interfacial area and volume in emulsions. colloids and surfaces a: physicochemical and engineering aspects, 295,91-98. 18. medoff, m., & masterman, t. (2011). processing biomass. inventors, google patents. 19. yin, b., zhang, r. & yao, p. (2015). influence of pea protein aggregates on the structure and stability of pea protein/soybean polysaccharide complex emulsions. molecules, 20, 5165-83. 20. binks, b. p., murakami, r., armes, s. p. & fujii, s. (2006). effects of ph and salt concentration on oil-in-water emulsions stabilized solely by nanocomposite microgel particles. langmuir : the acs journal of surfaces and colloids, 22, 2050-2057. 21. mao, l., xu, d., yang, j., yuan, f., gao, y. & zhao, j. (2009). effects of small and large molecule emulsifiers on the characteristics of b-carotene nanoemulsions prepared by high pressure homogenization. food technology and biotechnology;47, 336-42. 22. leong, t., wooster, t., kentish, s. & ashokkumar, m. (2009). minimising oil droplet size using ultrasonic emulsification. ultrasonics sonochemistry,16:721-727. 23. garciaa, l. c., tonona, r. v. & hubingera, m. d. (2012). effect of oil in emulsion and homogenization pressure on the microencapsulation of basil oil. embrapa agroindústria de alimentos-artigo em anais de congresso (alice); 1413-1421. 24. chiewchan, n., phungamngoen, c. & siriwattanayothin, s. (2006). effect of homogenizing pressure and sterilizing condition on quality of canned high fat coconut milk. journal of food engineering, 73, 38-44. 25. titapiccolo, g. i., alexander, m. & corredig, m. (2010). rennet-induced aggregation of homogenized milk: impact of the presence of fat globules on the structure of casein gels. dairy science & technology, 90,623-639. 26. schuh, r. s., bruxel, f. & teixeira, h. f. (2014). physicochemical properties of lecithin-based nanoemulsions obtained by spontaneous emulsification or high-pressure homogenization. química nova;37, 1193-1198. 27. rao, j-j., chen, z-m. & chen, b-c. (2009). modulation and stabilization of silk fibroin-coated oil-in-water emulsions. food technology & biotechnology, 47, 413-420. 28. destribats, m., rouvet, m., gehin-delval, c., schmitt, c. & binks, b. p. (2014). emulsions stabilised by whey protein microgel particles: towards food-grade pickering emulsions. soft matter, 10, 6941-6954. 29. qian, c. & mcclements, d. j. (2011). formation of nanoemulsions stabilized by model food-grade emulsifiers using high-pressure homogenization: factors affecting particle size. food hydrocolloids, 25, 1000-1008. 30. tan, c. p. & nakajima, m. (2005). β-carotene nanodispersions: preparation, characterization and stability evaluation. food chemistry, 92, 661-671. 31. tcholakova, s., denkov, n. d., sidzhakova, d., ivanov, i. b. & campbell, b. (2003). interrelation between drop size and protein adsorption at various emulsification conditions. langmuir, 19, 5640-5649. 32. kuhn, k. & cunha, r. (2012). flaxseed oil–whey protein isolate emulsions: effect of high pressure homogenization. journal of food engineering, 111,449-457. 33. soon-taek, h., jeong-won, k., yong-seon, j., eui-seok, l., na-young, g., san-seong, k., hyun-hyo, k., taeyoung, k., yong-hwa, l., young-seok, j. & ki-teak, l. (2013). emulsifying properties of surface-active substances from defatted rapeseed cake by supercritical carbon dioxide extraction. journal of the korean oil chemists' society, 30, 635-48. 34. campanella, o., dorward, n. & singh, h. (1995). a study of the rheological properties of concentrated food emulsions. journal of food engineering, 25, 427-440. 35. perrechil, fda., santana, rdc., fasolin, l. h., silva, casd. & cunha, rld. (2010). rheological and structural evaluations of commercial italian salad dressings. food science and technology (campinas), 30,477-482. 36. verlent, i., hendrick, m., rovere, p., moldenaers, p. & loey, a. v. rheological properties of tomato‐based products after thermal and high‐pressure treatment. journal of food science, 71, s243-s248. 37. rao, j. & mcclements, d. j. (2011). formation of flavor oil microemulsions, nanoemulsions and emulsions: influence of composition and preparation method. journal of agricultural and food chemistry, 59, 5026-5035. international journal of engineering materials and manufacture (2019) 4(4) 154-163 https://doi.org/10.26776/ijemm.04.04.2019.03 m. r. awall 1 , m. s. azad 2 , m. o. rahman 1 , s, sarker 3 , g. m. s. i. azad 4 1 department of civil engineering, rajshahi university of engineering & technology, bangladesh 2 department of civil engineering, university of creative technology chittagong, bangladesh 3 department of civil engineering, kunsan national university, s. korea 4 disha engineering ltd., bangladesh e-mail: samdani@uctc.edu.bd reference: awall, m. r., azad, m. s., rahman, m. o., sarker, s. and azad, m.s. i. (2019). strengthening of traditional mud houses on response to earthquake. international journal of engineering materials and manufacture, 4(4), 154-163. strengthening of traditional mud houses on response to earthquake md robiul awall, md samdani azad, md oli-ur-rahman, sajib sarker and gazi md sharfaraz imam azad received: 03 october 2019 accepted: 11 november 2019 published: 15 december 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract earthquake is an unexpected natural disaster that is unforeseeable and several earthquakes have been faced in bangladesh with a magnitude of more than 6 in richter scale in recent years. non engineered houses are very common in rural area. mudhouse is a typical house pattern among the non-engineered houses. the earthquake effect in conventional mud houses is a great concern. these houses are susceptible to earthquake damage due to some attributes of materials consisting of less stiffness, brittleness and poor bonding between the units. the present study deals with the strengthening of such houses using timber reinforcement with definite proportion contemplating the mud wall sizes and strengthening the walls by allowing some additional materials as reinforcements. arrangements of reinforcement were followed in such a way that they would not require skilled labour and much cost. a finite element application staad-pro was adopted to execute the required analysis of unreinforced and reinforced models considering both single story and double story. a series of analyses incorporating linear static and linear dynamic analyses were conducted to comprehend the actual response of models. investigations from analyses depict that timber reinforcements impart greater stiffness and strength against overturning which increases the frequency of the structure and diminishes the lateral displacements to a good extent. the output from analyses includes lateral displacements, frequency, time-dependent displacements and time-dependent acceleration which depict the positive behaviour of reinforced mud houses. such an arrangement of reinforcement can be a good choice to subside the detrimental effect of the earthquake. keywords: mud house, timber, staad. pro, earthquake, reinforcement 1 introduction construction of mud houses is a very common phenomenon among developing countries like bangladesh. from the economic and social point of view, mud houses were considered a better choice in bangladesh for centuries. mud is one of the oldest and widely used building materials due to its advantage comprising of environmental friendliness, easy construction, and good thermal and acoustic properties. it is evident that about 30% of the world population still use mud houses as a residence and about 50-60% of houses are made of mud/adobe in the northern part of bangladesh (islam and iwashita, 2010 [1]). there are variations in practices of making mud houses. like using jute, straw, cow-dung, grass, iron sheets. practicing of construction of mud houses has been continuing since the last few centuries. these houses are mainly of one, two or three-story houses. a two-story typical mud house is shown in figure 1. consideration of the story depends upon the family members and economic point of view. these houses are vulnerable to earthquakes and suffer serious structural damages or collapse. these problems include brittleness, weak joints, lack of structural integrity. once yielding occurs, cracks development occurs in the adobe and results from a complete loss of tensile strength which may cause severe damage to the structure. on the contrary, unreinforced mortar is much weak and the connections between mud blocks become very sensitive against lateral loads induced from the earthquake. with a few shaking of earthquake vibration, this result partial or full disintegration of materials. furthermore, for safety purposes, larger thickness mud walls are used to increase the seismic weight of the structure. strengthening of traditional mud houses on response to earthquake 155 figure 1: two-story mud house in manda, naogaon previous researches define that using reinforcements, different materials can improve the performances of traditional mud houses. islam and iwashita [1] discussed the adobe or mud materials which were reinforced by low-cost materials. a series of lab experiments were carried out in the research. straw, jute, cement were added to the mud block to improve the performance of such houses. in the case of straw, several facts were taken into consideration like as straw content, length of the straw, crushed straw and scale effect test of straw. in the case of jute, jute content, the length was the features of reflection. furthermore, the effect of gypsum and clay content were considered. finally, the effect of cement was also inspected. the outcome of the research deliberates that straw and jute increase the ductility while gypsum and cement improve the bonding. meli et al. [2] represented the strengthening of adobe houses for seismic actions. an experimental shaking table test was regulated in this study. only a part of the structure was considered in the test due to the table size requirements. three strengthening method was adopted in the research consisting of using a concrete bond beam, using steel ties and using wire mesh and mortar. the output of the study delivered that strengthening methods cover the essential aspects of using reinforcements. ottazzi et al. [3] delineated the shaking table tests to improved adobe masonry houses. a full-scale model was tested using a shaking table for assessing the performance of improved adobe masonry house. the reinforcement technique comprising of interior cane mesh and a crowning tie beam was adopted in the research. research outcome illustrated that using such reinforcements improves the quality of structures against earthquakes. further study on earthquake-resistant nonengineered building construction for a rural area in bangladesh was narrated by alam et al. [4] a vast study on damage analysis was carried out in this research. new techniques for strengthening mud, masonry and nonengineered reinforced cement concrete (rcc) house were adopted in this paper. conversely, economic consideration was also given priority. for mud house consideration, bamboo bracing in cross-orientation was considered. the denouement of the research gave a better idea for the present practice of non-engineered houses. arya [5] studied on non–engineered construction in developing countries. earthquake risks, its management, damages due to previous earthquakes, damage risks for non-engineered houses and some techniques for strengthening such houses were represented in this investigation. various types of retrofitting schemes in earthen houses were studied. in addition to saving existing and future buildings, the schemes in this might be some good options. uddin [6] reviewed on traditional housing technology in bangladesh. this paper highlights the mud made house technology in bangladesh. this paper explored the traditional housing technology, local’s interpretation against disasters. vargas et al. [7] explored the seismic strength of adobe masonry. they discussed the factors controlling the strength of adobe masonry, the effect of additives, improvements of adobe masonries by adding sands, straws. several practical recommendations were delivered from this study. bariola and sozen [8] inspected seismic tests of adobe walls. comprehensive research consisting of nine specimens and two types of ground motion was conducted. performing shaking table tests, the base motion at failure were investigated. besides, this failure types and response from shaking table tests were also noted. rahman et al. [9] illustrated the seismic effects of the mud house. they analysed the crack pattern and made a comparison before using and after using reinforcement. some studies on experimental and numerical analysis with improvement techniques are delineated in references [10-14] the aim of this research includes a proposal for providing timber reinforcements in the mud wall following a particular manner. the proposed reinforcement arrangement is the simplest one which doesn't require skilled labour and techniques. four different models have been taken into consideration. model-1 is the unreinforced while model2 is the reinforced single story model. similarly, model-3 is the unreinforced and model-4 is the reinforced double story building. the main issue for considering two different stories is to get a comprehensive idea about the response of seismic forces. for maintaining practical provisions, seismic parameters of naogaon district from the seismic zoning map of bnbc [15] have been taken into consideration. analyses results are indicating that the arrangements of reinforcements in the mud houses can be a decent option if the material quality is properly maintained. awall et al. (2019): international journal of engineering materials and manufacture, 4(4), 154-163 156 2 modeling 2.1 modelling of mud house modelling of mud house was conducted using a finite element package staad-pro v8i. the structure was discredited by 8-noded solid elements as shown in figure 2. the solid elements used in staad-pro [16] have three translational and three rotational degrees of freedoms per node. solid elements enable the solution of structural problems involving general three-dimensional stresses. for the present study, a typical mud house has been chosen with a door and three windows in case of a single-story and a door and seven windows for two-story mud houses. two different levels have been incorporated to comprehend the actual response of mud houses against seismic loading. a squareshaped plan has been adopted for the research purpose which stipulates it as a single room. the mud walls have been generated through mud blocks which are designated as solid elements. for modelling single-story mud houses, firstly a solid node has been generated. then the node is translated along the x-direction. after performing this, the total line translated again along the z-direction. a floor plane can be observed after this operation. then the mud wall has generated by maintaining clearance. in the case of modelling of double story, an additional story is added to the single story. the whole modelling process is illustrated in figure 3. figure 2: eight node solid element in staad-pro v8i figure 3: step by step formation of mud house model strengthening of traditional mud houses on response to earthquake 157 figure 4: arrangement of timber reinforcement in each mud block table 1: relevant properties of used materials property us customary unit si unit mud timber mud timber young's modulus (psi, kn/m 2 ) 12500 1332800 86184.4 9.18933 poisson' ratio 0.45 0.15 0.45 0.15 density (pcf, kn/m 3 ) 100 25 15.69 3.92 shear modulus (psi, kn/m 2 ) 4310.35 579478 29718.8 316552 2.2 modelling of timber reinforcement timber splices were used as reinforcement through the mud wall to gain sufficient stiffness. this research aims to strengthen the mud house by providing timber reinforcement at the centre of the walls. the used timber splices are 25mm in thickness. the section of the wall is provided as mud element and timber element as the 8-noded solid element is added further at the centre of the wall section. thus, the timber reinforcement is provided although the walls excepting the openings. a single unit of the wall providing the mud element and timber reinforcement is shown in figure 4. the relevant properties of materials have been considered from the research of rahman et al. [9]. these properties have been represented in table 1. 3 seismic analyses bangladesh national building code [15] has specifications for seismic analysis and zone coefficients that are adopted from the earthquake zoning map of bangladesh. other parameters, in which earthquake forces are dependent like structural importance factor, soil profile type, response modification factor are considered as per ubc1997 [17]. both static and dynamic analyses of mud houses were incorporated into this study. 3.1 static analysis in the case of static analysis, the seismic force is assumed to be acted as static forces. there are provisions in different codes for static analysis. as a rule, regular-shaped buildings with a height below 75 m are in the range in which engineers can adopt a static method of analysis. on the contrary, irregular buildings with a height below 20 m can be taken in such consideration as per ubc1997 [17]. irregularity of structures based on different criteria and assumptions. 3.2 equivalent static force analysis in this research, the equivalent static force method has been adopted for static analysis. if equivalent static force method is selected for seismic analysis of a building, the design seismic forces, their vertical distribution over the height of the building, and the corresponding internal forces will be calculated and determined as per ubc [17] code provisions to which are given in equations (1-4). from the static analysis, some attributes have been noted. the outcome from this analysis comprehends lateral displacements and developed stresses in the mud wall. 𝑉 = cvi rt w (1) 𝑉 = 2.5cai r w (2) v= 0.11caiw (3) t= ct(hn)3/4 (4) where, ct = 0.020 (0.0488) for all other buildings; w = total seismic weight of the building; cv = 0.32 and ca = 0.24; r= response modification factor = 2.9; soil profile = sc; t = structural period, which can be calculated from equation (4); i = structural importance factor = 1. awall et al. (2019): international journal of engineering materials and manufacture, 4(4), 154-163 158 table 2 shows the differences in lateral displacements of different models. the unreinforced models face greater displacements considering the reinforced models. considering a single-story mud house, the unreinforced one is with a displacement of 6.35 mm and 5.72 mm along x and z directions. on the contrary, the reinforced samples are susceptible to less deflection with 4.14 mm and 3.41 mm along with the corresponding directions. the percentages of lessening due to using reinforcement are 34.8% and 40.38%. contemplating the double story mud houses, substantial differences can also be observed. unreinforced one is with displacements of 20.26 mm and 19.46 mm while the reinforced one is 7.09 mm and 6.9 mm along x and z directions. the percentages of reducing displacements are 65% and 64.54% which defies the use of unreinforced models. 3.3 dynamic analysis in the case of dynamic analysis, the seismic force is assumed as dynamic loads. response spectrum analysis and time history analysis are considered in this study. 3.3.1 response spectrum analysis dynamic analysis using the response spectrum method is the method of calculating peak modal responses for sufficient modes to capture at least 90% of the participating modal mass of the building. a particular damping ratio is taken considering the property of structure materials. normalized response spectra considering the soil profile and relevant co-efficient is to be made for the analysis purpose. displacements, story forces, story shears, and base reactions for each mode of response can be combined following two methods consisting of square root sum of squares (srss) rule or the complete quadratic combination (cqc). this method of analysis is to be done by using normalized response spectra as dynamic loads [17]. these parameters can be deduced from the inputs consisting of the soil profile and seismic coefficient (ca and cv). soil type= sc, ca= 0.24, cv= 0.32, short period, ts= cv/2.5ca = 0.53s, fundamental period, t0= 0.2ts = 0.1067s. the response spectra used in this research are represented in figure 5. it has been observed from table 3 that the lateral displacements from response spectrum analysis exhibit a similar behaviour like the static analysis. but the numerical values are not alike at all. the dynamic analysis was incorporated by considering normalized response spectra. table 2: displacements from equivalent static force analysis single story un-reinforced single story reinforced % decreasing double story un-reinforced double story reinforced % decreasing along x (mm) 6.35 4.14 34.80% 20.26 7.09 65.00% along z (mm) 5.72 3.41 40.38% 19.46 6.90 64.54% table 3: displacements from response spectrum analysis single story unreinforced single story reinforced % decreasing double story unreinforced double story reinforced % decreasing along x(mm) 9.64 6.66 30.91% 35.40 13.12 62.93% along z(mm) 9.18 5.59 39.10% 33.88 13.01 61.59% figure 5: response spectrum graph as per ubc1997 strengthening of traditional mud houses on response to earthquake 159 the displacement values are almost double concerning the values of static analysis. but there is a reduction of displacements while using timber splices as reinforcements. the percentages of reducing displacements in single-story models are 30.91% and 39.10% to the corresponding directions. on the other hand, the reduction percentages for the double story are 62.93% and 61.59%. the percentages of reduction of displacements are nearly the same in both static and response spectrum analysis. table 4 defines the differences in frequencies of different models due to dynamic loading. it is understandable from the result that the reinforced samples are with greater values of frequencies considering the unreinforced ones. the greater values of frequencies define greater stiffness of the above structures. it is observed from the mode shape analysis that, the first torsion mode is found in the third mode for the unreinforced case and the reinforced case, the first torsion mode is found in the fourth mode. this phenomenon can be observed for both single story and double story houses which are represented in figures 6-7. the vulnerability of unreinforced models can be predicted from this mode shape observation. the modal analysis results are obtained from staad.pro software package [16]. figure 6 demonstrates the 1st torsion mode for the single story building (unreinforced and reinforced). for unreinforced condition, the first torsion mode is found at third mode: 6.293 hz. besides, the torsion mode shifts to fourth mode: 9.166 hz. this phenomenon illustrates the added stiffness through the timber reinforcements. figure 7 depicts the first torsion modes of two story mud houses that include unreinforced and reinforced condition. for unreinforced condition, the first torsion mode is developed at third mode: 4.021 hz. in addition, this torsion mode shifts to fourth mode: 7.11 hz. it is evident that the reinforcement imparts additional stiffness which influences the modal response of the structures. 3.3.2 time history analysis el centro [18] earthquake acceleration data are shown in figure 8 is considered as an input parameter of time history analysis. table 5 conveys the maximum lateral displacements from linear time history analysis. it defines that the use of timber reinforcement reduces the lateral displacements to a good extent. a reduction of lateral displacement of more than 60% ensures the affectivity of using timber reinforcements. table 4: frequency analysis frequencies (hz) mode single story unreinforced single story reinforced double story unreinforced double story reinforced 1 5.195 6.678 2.516 4.443 2 5.686 6.806 2.598 4.852 3 6.293 7.709 4.021 6.665 4 6.772 9.266 5.178 7.111 5 7.831 11.013 6.588 7.674 (a) (b) figure 6. first torsion mode shape model of (a) unreinforced (mode 3, 6.293 hz) single story and (b) reinforced single story (mode 4, 9.166 hz) awall et al. (2019): international journal of engineering materials and manufacture, 4(4), 154-163 160 (a) (b) figure 7. first torsion mode shape model of (a) unreinforced (mode 3, 4.021 hz) double story and (b) reinforced double story (mode 4, 7.11 hz) figure 8: el centro earthquake acceleration data figure 9: time-dependent peak-to-peak displacements along x-direction for single story (a) unreinforced (17.93 mm) and (b) reinforced (8.25 mm) structure. (a) (b) strengthening of traditional mud houses on response to earthquake 161 table 5: displacements from time history analysis single story unreinforced single story reinforced percentage decreasing double story unreinforced double story reinforced percentage decreasing alongx (mm) -15.04 -7.84 47.83 -45.21 -13.8 69.48 along z (mm) -13.16 -6.36 51.67 -41.91 -16.4 60.87 figure 10: time-dependent peak-to-peak acceleration along x-direction for single story (a) unreinforced (18.94 m/s2) and (b) reinforced (12.82 m/s2) structure figure 9 depicts the peak to peak lateral displacements for the time of unreinforced and reinforced single-story models along the x-direction. the unreinforced sample shows displacements of 8.47 mm at 4.88s and -9.46 mm at 4.97s with a peak to peak displacement of 17.93 mm along the x-direction. on the contrary, the reinforced sample displacements are 4.07 mm at 4.82s and -4.18 mm at 3.54s with a peak to peak displacement of 8.25 mm along the x-direction. the reduction of peak to peak displacement using reinforcement is 53.98% to the x-direction. figure 10 illustrates the time-dependent acceleration of the following single-story models. these accelerations are the accelerations of the identical nodes of both models. from the figures, it is clear that the reinforced one is susceptible to less acceleration compared with the unreinforced one. the unreinforced one accelerates 9.62 m/s2 at 4.97s and 9.32 m/s2 at 4.7s while the reinforced one accelerates at an acceleration of 6.73 m/s2 at 4.75s and -6.09 m/s2 at 3.61s along x-direction. the peak of peak acceleration is reduced by 32.31% in an identical direction. figure 11 deliberates the time-dependent displacements of the double story mud house. explicit differences can be observed in the graphs which denote that the use of timber splice minimizes the seismic load effect to a considerable extent. the peak to peak displacement reduces more than 70% along the x-direction. the timedependent accelerations of the double story mud house are shown in figure 12. substantial differences can be observed in the graphs which portray that the use of timber splice minimizes the seismic load effect to a considerable extent. the peak to peak acceleration is reduced by more than 20% along the x-direction. (a) (b) awall et al. (2019): international journal of engineering materials and manufacture, 4(4), 154-163 162 figure 11: time-dependent peak-to-peak displacements along x-direction for (a) unreinforced (80.4 mm) and (b) reinforced (20.11 mm) structure figure 12: time dependent peak-to-peak accelerations along x-direction for double story structure (a) unreinforced (24.7 ms-2) and (b) reinforced (18.91 ms-2) structure. 4 conclusions from the investigation and results obtained from numerical analysis, it is evident that using timber splices can be a good choice in mud houses. considering the outcomes, some conclusions can be made. 1. seismic analysis has been incorporated following three methods: equivalent static analysis, response spectrum analysis. the results from each method have good agreements, stated through the lateral displacements. reinforced samples are susceptible to less lateral displacements compared to the unreinforced one. it demonstrates the improvement of resistance of the structures. (a) (b) (a) (b) strengthening of traditional mud houses on response to earthquake 163 2. free vibration analysis is incorporated and the mode shapes are obtained. it is substantial from the modal analysis that the stiffness of models is increased significantly by using timber reinforcement. the proposed timber reinforcement imparts added stiffness that improves the modal frequency. the torsion mode shifts to higher frequency which delineates the safety of reinforced models. 3. from time history analysis, the time-dependent displacement and acceleration from time history analysis also show a decent result that has good agreements with equivalent static analysis and response spectrum analysis. peak to peak displacements and accelerations are reduced considerably. 4. present research deals with the linear analysis of structures. pushover analysis and non-linear time history analysis can be accomplished to apprehend the non-linear response of structures. acknowledgement the authors would like to thank md. saiful alam saif, lecturer, english language and literature, university of creative technology chittagong, for grammatical accuracy and english language standard used in this manuscript. references 1. islam, m.s., and iwashita, k. (2010). earthquake resistance of adobe reinforced by low-cost traditional materials. j. nat. disast. sci., 32:1-21. 2. meli, r., hernandez, o., and padilla, m. (1980). strengthening of adobe houses for seismic actions. proceedings of the 7th world conference on earthquake engineering, istanbul, turkey, 465-472. 3. ottazzi, g., yep, j., and blondet, m. (1988). shaking table tests of improved adobe masonry houses. proceedings of the 9th world conference on earthquake engineering, tokyo-kyoto, japan. p. 1123-1128. 4. alam, d.m.j., ahsan, r., akhter, f., and paul. a. (2014). earthquake resistant non-engineered building construction for rural area in bangladesh. http://www.iitk.ac.in/nicee/wcee/article/14_09-02-0006.pdf 5. arya, a. (2000). non-engineered constructions in developing countries an approach towards earthquake risk prediction. bulletin of the new zealand national society for earthquake engineering, 33(3):187-208. 6. uddin, n. (2008). a study on traditional housing technology of bangladesh. indian j. tradit. know., 7:494500. 7. vargas, j., bariola, j., and blondet, m. (1984). seismic strength of adobe masonry. u.s. agency for international development (aid) research project di-84. 01. 8. bariola, j. and sozen, m.a. (1990). seismic tests of adobe walls. earthquake spectra. 6:37-56. 9. rahman, m., hassan m.r., and hossain, m.t. (2013). seismic performance analysis of mud house in the context of bangladesh. int. j. sci. eng. res., 4:1612-1617. 10. illampas, r., ioannou, i., & charmpis, d. c. (2013). overview of the pathology, repair and strengthening of adobe structures. int. j. archit. herit., 7(2): 165-188. 11. illampas, r., charmpis, d. c., & ioannou, i. (2014). laboratory testing and finite element simulation of the structural response of an adobe masonry building under horizontal loading. eng. struct., 80: 362-376. 12. illampas, r., ioannou, i., & charmpis, d. c. (2017). experimental assessment of adobe masonry assemblages under monotonic and loading–unloading compression. mater. struct, 50(1): 79. 13. illampas, r., silva, r. a., charmpis, d. c., lourenço, p. b., & ioannou, i. (2017). validation of the repair effectiveness of clay-based grout injections by lateral load testing of an adobe model building. constr. build. mater., 153: 174-184. 14. illampas, r., charmpis, d. c., & ioannou, i. (2014). finite element simulation of the structural response of adobe masonry buildings subjected to lateral loading. proceedings of 9th international conference on structural analysis of historical constructions, mexico city, mexico, 1-12. 15. housing and building research institute. (2014). bangladesh national building code. 16. bentley sustaining infrastructure (2006). staad-pro technical references. international conference of building officials 17. 1997. uniform building code. 18. vibrationdata el centro earthquake page, (1940). el centro earthquake data. http://www.vibrationdata.com/elcentro.htm international journal of engineering materials and manufacture (2017) 2(4) 94-102 https://doi.org/10.26776/ijemm.02.04.2017.03 m. r. hossain graduate school of industrial engineering & management khulna university of engineering & technology, khulna 9203, bangladesh e-mail: rudrorahat50@gmail.com m. h. ali department of industrial and production engineering bangladesh army university of science and technology, saidpur 5310, bangladesh e-mail: hasankuet38@gmail.com m. a. amin1 and m. g. kibria2 department of industrial engineering & management khulna university of engineering & technology, khulna 9203, bangladesh 1e-mail: alaminkuet01@gmail.com 2e-mail: kibria05_ruet@yahoo.com m. s. ferdous department of mechanical engineering bangladesh army university of science and technology, saidpur 5310, bangladesh e-mail: munazeer_218@yahoo.com reference: hossain, m. r., ali, m. h., amin, m. a., kibria, m. g., and ferdous, m. s. (2017). fabrication and performance test of aluminium alloyrice husk ash hybrid metal matrix composite as industrial and construction material. international journal of engineering materials and manufacture, 2(4), 94-102. fabrication and performance test of aluminium alloy-rice husk ash hybrid metal matrix composite as industrial and construction material md. rahat hossain, md. hasan ali, md. al amin, md. golam kibria, and md. shafiul ferdous abstract aluminium matrix composites (amcs) used extensively in various engineering fields due to their exceptional mechanical properties. in this present study, aluminium matrix composites (amcs) such as aluminium alloy (a356) reinforced with rice husk ash particles (rha) are made to explore the possibilities of reinforcing aluminium alloy. the stir casting method was applied to produce aluminium alloy (a356) reinforced with various amounts of (2%, 4%, and 6%) rice husk ash (rha) particles. physical treatment was carried out before the rice husk ash manufacturing process. the effect of mechanical strength of the fabricated hybrid composite was investigated. therefore, impact test, tensile stress, compressive stress, and some other tests were carried out to analyse the mechanical properties. from the experimental results, it was found that maximum tensile, and compressive stress were found at 6% rice husk ash (rha) and aluminium matrix composites (amcs). in future, the optimum percentages of rice husk ash (rha) to fabricate the hybrid composites will be determined. also, simulation by finite element method (fem) will be applied for further investigation. keywords: rice husk ash (rha), aluminium matrix composites (amcs), stress. 1 introduction composites has become the most widely used materials because of their adaptability in different conditions. also, the relative ease of combination with other materials to show exhibit exceptional properties to serve different purpose. the development of low cost aluminium matrix composites reinforced with environmentally friendly material has been one of the major innovations in the field of materials to curtail environmental pollution. aluminium matrix composites (amcs) were developed to improve the performance of conventional aluminium alloys which cannot meet the requirement of modern engineering products. aluminium matrix composites (amcs) exhibit high strength, high elastic modulus and good wear resistance compared to the without reinforced aluminium alloys. aluminium matrix composites (amcs) are increasingly used to produce several components in aerospace, automotive, marine and nuclear industries [1-3]. aluminium matrix composites (amcs) have emerged as a class of received: 23 october 2017 accepted: 29 november 2017 published: 10 december 2017 publisher: deer hill publications © 2017 the author(s) creative commons: cc by 4.0 fabrication and performance test of aluminium alloy-rice husk ash hybrid metal matrix composite… 95 materials capable of advanced structural, aerospace, automotive, electronics, thermal management, and wear applications. rice husk ash is one of the most inexpensive, and low-density reinforcement that contain sic, al2o3 etc. also, available in large quantities as solid waste by-product. therefore, its efficient utilization is urgently needed to avoid environmental pollution. rice husk is an agricultural residue from the rice milling process. a huge amount of rice husk ash (rha) are produced every year across the world. therefore, the effective utilization of this agricultural waste will protect the environment. nowadays, aluminium is being widely used in construction, household purpose like windows and doorframe, automobiles, electronic equipment, and other devices. the cost of effective production, improving the strength, and its feasibility analysis is the ultimate goal of this research. in this study, our main approach is to fabricate a hybrid composite that enhances the various physical properties rather than normal metal alloy. itskos et al. investigated that a356 alloy or its similar alloy is used as a matrix for obtaining composites, which have an enhanced wear resistance, promising mechanical properties at room temperature. also, have enhanced mechanical properties at elevated temperatures [4]. prasad et al. shows the damping performance of hybrid composites using dynamic mechanical analyzer (dma) [5]. the composites were fabricated with 2%, 4%, 6%, and 8% by weight of rice husk ash (rha), and sic in equal proportions using two stages to stir casting process. it was observed that the dislocation density, which results from the thermal mismatch between the reinforcement, matrix, and the porosity of composites, has a great influence on the damping capacity of hybrid composites. sahoo et al. studied the tribological studies performed in recent one and a half decades on different aluminium matrix composites for their suitability and potentiality for tribological applications [6]. uvaraja et al. using taguchi technique reinforced with mixtures of silicon carbide (sic) and boron carbide (b4c) particles, known as hybrid composites have fabricated by stir casting technique (liquid metallurgy route), and optimized at different parameters like sliding speed, applied load, sliding time, and percentage of reinforcement by taguchi method [7]. shivaraja et al. evaluated the impact strength of al 356 alloy matrix hybrid composites reinforced with zirconium silicate and silicon carbide particles has been successfully synthesized by the stir casting method. the results from the study reveal that there is considerable increase in the fracture toughness in the presence of both silicon carbide and zirconium silicate reinforcement in the matrix alloy. the matrix alloy with 2% sic and 6% zrsio reinforcement has shown high toughness for fracture [8]. alaneme et al. carried out an investigation on the fabrication characteristics and mechanical behaviour of rice husk ash–alumina reinforced al-mg-si alloy matrix hybrid composites. they found that specific strength, percent elongation and fracture toughness of the 2wt% rha containing hybrid composite was higher than that of the single al2o3 reinforced and other hybrid composite compositions worked on [9]. with this background, in the present work an attempt has been made to fabricate aluminium alloy and rha hybrid metal matrix composites by stir casting process. also, examine the mechanical characterization to investigate whether it could be used in the door-window frame, roof components like beam or column, automobiles, and other construction purposes with economic feasibility. 2 materials preparation and fabrication procedure aluminium alloy a356 was used to make the hybrid composites with 2%, 4%, and 6% rice husk ash, respectively. stir sand mold casting process was applied to fabricate the specimen. figure 1 shows the geometry of specimens to analyse the mechanical properties of fabricated hybrid composites. wooden pattern was used during the casting process. the length, width, and thickness of the specimen are 250mm, 60mm, and 3mm, respectively. the chemical compositions, and mechanical properties of a356 material shown in table 1, and 2, respectively. table 1: chemical compositions of aluminium alloy, a356 al si fe mn mg zn ti cu others 91.2-93.1 6.5-7.5 0.13 0.05 30-0.45 0.50 0.20 0.10 0.20 table 2: mechanical properties of aluminium alloy, a356 ultimate stress σ t (mpa) compressive strength σ c (mpa) elongation φ (%) 234 195 2 hossain et al., (2017): international journal of engineering materials and manufacture, 2(4), 94-102 96 2.1 pattern preparation as the main implementation would be in the window, doorframe, and roof components as a beam or column, the pattern has made like window frame components. window frame which is fixed with the wall contain three parts: (i) top part, (ii) side part, and (iii) bottom part. hence, for a rectangular shape frame, two side parts are same. therefore, three patterns are enough for the experiment. all the patterns are 250mm in length, 60mm in width, and 3mm in thickness. figure 2(a), (b), and (c) show isometric view of top, side, and bottom part, of a window frame, respectively. 2.2 physical treatment of rice husk in the present study, rice husk procured from local sources was collected, and has thoroughly washed with water to remove the dust and dried. in order to sustain for further operations, the rice husk is usually dries at room temperature. after the physical treatment, no chemical properties changed normally [10]. dust, dirt, and other unnecessary substances removed from it for further actions. this treatment was done due to avoid the unwanted foreign piratical in rice husk. figure 3 shows the rice husk before and after the physical treatment. figure 1: geometry and dimensions (in millimetre) of the specimens of fabricated hybrid composites (a) for tensile, compressive, and hardness test, (b) notched specimen for impact test and (c) geometry of v-notch. (a) (b) (c) figure 2: window frame fabrication by stir casting process of hybrid composites (a) top part, (b) side part and (c) bottom part. fabrication and performance test of aluminium alloy-rice husk ash hybrid metal matrix composite… 97 (a) (b) figure 3: rice husk (a) before physical treatment and (b) after physical treatment. 2.3 heat treatment process of rice husk ash after the physical treatment of dry rice husk, it was taken to graphite crucible. by the proper arrangement of furnace and graphite crucible, dried rice husk was then heated up to 150°c for one hour. this operation helps to remove the moisture and organic matter. during this operation, the colour of the husk changed from yellowish to black because of charring of organic matter. after that the ash again heated up to 500°c to 650°c for 6 hours, to remove the carbonaceous material [11]. in this operation, the rice husk completely burns. for obtaining desired properties, the ash is further heated in the electric furnace at 700°c for 12 hours. here, the rice husk ash was used as a filler material. after finalizing this operation and after cooling the ash’s colour is completely changed from black to grey or slightly greyish white. the burning process of rice husk is shown in the figure 4. after the heat treatment the white rice husk ash (rha) has observed. for the sake of having proper composite material only the white rice husk ash (rha) had collected from the mixed specimen by separating the black part and other associated particles. figure 5 shows the flowchart of rice husk ash preparation. (a) (b) (c) (d) figure 4: preparation of rice husk ash (a) rice husk burning in furnace, (b) rice husk ash, (c) rice husk is being moved to electric furnace and (d) heated in electric furnace. hossain et al., (2017): international journal of engineering materials and manufacture, 2(4), 94-102 98 figure 5: flow chart representing the process of making rice husk ash sequentially. 2.4 preparation of aluminium alloy initially, a356 aluminium-alloy has charged into the graphite crucible. at first the aluminium alloy heated at about 750°c till the entire alloy in the crucible melted. once the molten metal has fully melted, it has stirred manually by the stirrer made up of stainless steel to remove porosity, bubbles inside the melted aluminium alloy [12]. 2.5 mixing of rice husk ash with aluminium alloy (a356) in another crucible the rice husk ash (rha) were preheated to 800°c for 1 hour before incorporation into the melt. the molten metal was added into the preheated rice husk ash (rha) particles at a constant rate during the stirring time. constant stir has arranged to get a uniform mixture. in this case, manual stir casting done where a leader was used to mix the aluminium with rice husk ash (rha). continuous rotation of the leader maintained to mix the aluminium with rice husk ash (rha) [12]. 2.6 preparation of stir casting the sand mold is mainly prepared by green sand which is also known as molding sand. the mold mainly prepared with the help of drag and cope. in order to get uniform solidification, the mold was preheated at 5000c in furnace for about 30 minutes. the mixture poured slowly into the mold. using this process 2%, 4%, and 6% by weight rice husk ash (rha) particle reinforced composites fabricated. the casted metal matrix composite (mmc) samples examined by different types of destructive and nondestructive testing procedure for further actions. type 1: aluminium alloy a356 with 2% rice husk ash, rha type 2: aluminium alloy a356 with 4% rice husk ash, rha type 3: aluminium alloy a356 with 6% rice husk ash, rha the arrangements of drag part, cope part, and two parts was attached for pouring. the state of mold after pouring shown in figure 6(a). after the molten metal was poured, the mold was kept at room temperature to solidify. then the metal which had poured through the runner, and riser removed by cutting operation. some grinding operation applied for proper finishing. figure 6(b) shows the casted window frame. in similar way, specimens for the testing of mechanical properties was also casted. figure 1 shows the geometry of specimens of hybrid composites to analyse the mechanical properties. v-notch cut in some cases to get the impact strength. 2.7 experimental procedure the tensile and compressive test was performed by using an electro-mechanical universal testing machine (utm) equipped with the maximum capacity of the load cell at 3kn. the specimens were placed in the grip of the universal testing machine (utm) machine, and the test was performed by applying tensile load during tensile test, and compressive load during compressive stress test, respectively until failure at room temperature. the corresponding load, strain was plotted. then tensile stress, compressive stress, and reduction of area were calculated from the experimental data. impact testing was carried out on tinius olse machine as per procedure mentioned in astm d256. fabricated hybrid composites specimens were placed in vertical position (izod test), and hammer was released to make impact on specimen, and crt reader gives the reading of impact strength. the hardness of the hybrid composites was measured using a brinell hardness tester machine. rice husk from rice mills (in average from 100kg of paddy can be found in 20kg of husk) washed by water to remove dust and dried at room temperature heated at 200℃ in crucible for 1 hour in order to remove the moisture and organic matter (colour will turn from yellow to black) heated to 600℃ to 750℃ in crucible for 6 hours in order to remove carbonaceous material heated to 800℃ in crucible for 12 hours in order to obtain desired properties (colour will turn from black to greyish white). fabrication and performance test of aluminium alloy-rice husk ash hybrid metal matrix composite… 99 (a) (b) figure 6: fabrication of hybrid composites (a) stir sand mold casting process and (b) window frame after casting. (a) (b) (c) figure 7: evaluation process of (a) izod impact, (b) bhn and (c) tensile stress. 3 experimental results and discussion 3.1 tensile test every composites and alloys have a great impact on its mechanical properties. even the effect of their loading imposes great influence on their mechanical properties. a series of investigation were carried out to evaluate the mechanical properties of fabricated hybrid composites. the results of the mechanical properties are shown in figure 8. in this study, it has been found that the tensile stress is increased due to the increased percentage of rice husk ash (rha) in aluminium alloy as shown in figure 8(a). in the experimental work piece, it has been found that during tensile operation the elongation of different composites increased due to the increased percentage of rice husk ash (rha) in aluminium alloy. 3.2 compressive test the variations of compressive strength with the addition of rice husk was shown in figure 8(a). from the experimental results, it was observed that the compressive strength was also increased with an increase in the weight percentage of rice husk particles. due to the hardening of the base alloy by rice husk particles, the compressive strength increased, and the maximum compressive strength was found when 6% rice husk ash was used in the hybrid composites. 3.3 impact test an impact tester can observe the toughness of a material. generally, notch type specimens are used for impact tests. the purpose of the notch is to serve as a stress concentrator. izod impact testing machine and one-sided v-notched specimens were used to evaluate the impact energy of this hybrid composite. the specimen’s length was 120mm, notch depth was 3mm, and the angle was 60°. impact test identifies how much energy a material can absorb. the testing specimens are mainly made of aluminium alloy, which has low hardness and high ductility properties. therefore, to evaluate the absorbed energy, pendulum was set at the lowest position to get accurate values. corresponding impact stress is shown in figure 8(b). hossain et al., (2017): international journal of engineering materials and manufacture, 2(4), 94-102 100 3.4 hardness test the variation of hardness of different combinations of aluminium and rice husk ash reinforcements in the fabricated metal matrix composites (mmcs) was evaluated. specimens were placed at universal hardness testing machine (uhtm) for testing hardness which was usually consists of a hydraulic system diamond ball indenter. the brinell hardness number, (bhn) is the ratio of load in kilograms to the impressed area in square millimetres, and is calculated by the following equation (1), where, l= applied load, d= diameter of load in mm, d= diameter of impression: bhn = 𝐿𝐿 𝜋𝜋𝜋𝜋 2 (𝐷𝐷−�(𝐷𝐷2−𝑑𝑑2)) (1) it is observed that the optimum hardness is achieved for aluminium, and 6% rice husk ash combination. this occurs due to increases in surface area of the matrix, and the reduced grain sizes. the presence of such hard surface area offers more resistance to plastic deformation, which leads to increase in hardness. in our experimental work piece, it has been found that the hardness is increased when the percentage of rice husk ash (rha) in fabricated hybrid composites was increased. figure 8(c) shows the hardness number of 2%, 4%, and 6% rice husk ash (rha) mixed aluminium metal matrix hybrid composites. figure 8: mechanical properties of hybrid composites (a) tensile and compressive test, (b) impact test, (c) hardness test and (d) area reduction test. 3.5 area reduction test figure 8(d) shows the effect of percentage reinforcement of rice husk ash (rha) on percentage elongation of composites. it was observed that percentage of the area of the composites decreases with the increase of rice husk ash particles. this is due to the increase in hardness of the rice husk ash particles or clustering of the particles. in the experimental work piece, it has been found that during tension operation the cross-sectional area of fabricated hybrid composites increased due to the increasing percentage of rice husk ash (rha) in aluminium alloy. the reduction in area was determined by using following equation (2), where, ao = original cross section area, af = final cross section area: reduction in area (%) = 𝐴𝐴0−𝐴𝐴𝑓𝑓 𝐴𝐴0 × 100 (2) fabrication and performance test of aluminium alloy-rice husk ash hybrid metal matrix composite… 101 3.6 microscopic analysis the microstructure of hybrid composites with rice husk ash was examined by using optical microscope and shown in figure 9. from the microstructure analysis, it is clearly reveals minimal micro porosities in the casting, and the rice husk ash particles are clearly visible. also, there is a good bonding between metal matrix and rice husk ash (rha) reinforcements which indicates good bonding strength. due to these reasons, the mechanical properties such as tensile-compressive stress, impact stress, hardness are increased, and the area reduction rate decreased. 4 economic feasibility it was found that after mixing rice husk ash (rha), the weight of the hybrid composites was reduced significantly. aluminium is being highly used where light weight is very important. as the strength, and weight was improved in this experimental study, the aptness of the final composite for other applications will be widespread. the main implementation of the experimented hybrid composites is in window frame, doorframe and roof components as a beam or column, and from the result it was found that a356/rha is comparatively better than mere a356. according to the cost calculation comparison between raw aluminium, and rice husk ash (rha) with metal matrix composite (mmc), it was found that total cost was reduced 13% when 6% rice husk ash (rha) was used to fabricate the aluminium-rice husk ash hybrid composites. this calculation was done for 1000kg of hybrid composites production. 5 swot analysis swot analysis usually performed for evaluating strength, weakness, opportunities, threats and is a structured planning method that evaluates those four elements of any projects or research. for our fabricated aluminium alloy and rice husk ash hybrid composites the swot analysis has been done. figure 10 shows the result of our swot analysis. it could be a great opportunity in the light industrial sectors and construction area to use aluminium alloy and rice husk ash hybrid composites with some improved mechanical properties comparing with the pure aluminium alloy. but the drawback is with the increase in tensile strength and hardness the area reduction rate decreases. (a) (b) figure 9: microstructure of aluminium alloyvarious percentages of rice husk ash (rha) hybrid composites (a) 6% and (b) 2%. figure 10: swot analysis of aluminium alloy-rice husk ash hybrid composites. hossain et al., (2017): international journal of engineering materials and manufacture, 2(4), 94-102 102 6 conclusions in this study, rice husk ash particles were successfully incorporated in a356 alloy by using stir casting techniques. the use of rice husk ash (rha) for the fabrication of hybrid composites can turn agricultural waste into industrial assets. a series of tests were conducted to investigate the mechanical properties of fabricated aluminium alloy-rice husk ash metal matrix hybrid composites. also, fabricated window frame using this hybrid composites shows the application feasibility, and improve mechanical properties. therefore, it could be used in the door-window frame, roof components like beam or column, automobiles, and other construction purposes. experimental results showed that the mechanical properties of aluminium metal matrix hybrid composites have increased with the increasing percentages of rice husk ash (rha) in the hybrid metal matrix composites except the area reduction property due to the elongation decreases with the increase in rice husk ash content. production of cost effective aluminium composites could have incorporated by using rice husk ash to get improved hardness, and strength. acknowledgement the authors are grateful to professor tarapada bhowmick for his valuable suggestions in this study. references 1. itskos, g., rohatgi, p. k., moutsatsou, a., defouw, j. d., koukouzas, n., vasilators, c. & schultz, b. f. (2012). synthesis of a356 al-high-ca fly ash composites by pressure infiltration technique and their characterization. journal of materials science, 47(9), 4042-4052. 2. rohatgi, p. k. (1993). metal matrix composites. defence science journal, 43(4), 323-349. 3. zahi, s. & daud, a. r. (2011). fly ash characterization and application in al-based mg alloys. materials and design, 32(3), 1337-1346. 4. mišković, z., bobić, i., tripković, s., rac, a. & vencl, a. (2006). the structure and mechanical properties of an aluminium a356 alloy base composite with al2o3 particle additions. tribology in industry, 28(3-4), 23-27. 5. prasad, d. s. & shoba, c. (2016). experimental evaluation onto the damping behavior of al/sic/rha hybrid composites. journal of materials research and technology, 5(2), 123-130. 6. sahoo, p. & ghosh, s. (2011). tribological behavior of aluminium metal matrix composites–a review. journal of tribology research, 2(1), 1-14. 7. uvaraja, v. c. & natarajan, n. (2012). optimization of friction and wear behavior in hybrid metal matrix composites using taguchi technique. journal of minerals and materials characterization and engineering, 11(8), 757-768. 8. shivaraja, h. b. & parveen, k. b. s. (2017). experimental determination and analysis of fracture toughness of mmc. international journal of science and research, 2319-7064. 9. alaneme, k. k., akintunde, i. b. & olubambi, p. a. (2013). fabrication characteristics and mechanical behaviour of rice husk ash – alumina reinforced al-mg-si alloy matrix hybrid composites. journals of materials research and technology, 2, 60-67. 10. prasad, d. s. & krishna, a. r. (2011). production and mechanical properties of a356.2/rha composites. international journal of advanced science and technology, 33, 51-58. 11. das, s., dan, t. k., prasad, s. v. & rohatgi p. k. (1986). aluminium alloy-rice husk ash particle composites. journal of materials science letters, 5(5), 562-564. 12. peter a. o. & kenneth k. a. (2013). corrosion and wear behaviour of rice husk ash alumina reinforced al-mgsi alloy matrix hybrid composites. journal of materials research and technology, 2(2), 188-194. international journal of engineering materials and manufacture (2022) 7(3) 89-94 https://doi.org/10.26776/ijemm.07.04.2022.01 umma abdullahi centre for energy research and training, ahmadu bello university zaria post code: 810261, kaduna state nigeria mechanical engineering department, faculty of engineering bayero university, kano, pmb 3011 kano state, nigeria e-mail: ummaabdullahi@abu.edu.ng reference: abdullahi, u. (2022). effect of tempering treatment on the post-weld properties and chemical compositions of arcwelded alloy steels. international journal of engineering materials and manufacture, 7(4), 89-94. effect of tempering treatment on the post-weld properties and chemical compositions of arc-welded alloy steels umma abdullahi received: 18 august 2022 accepted: 28 august 2022 published: 25 october 2022 publisher: deer hill publications © 2022 the author(s) creative commons: cc by 4.0 abstract the effect of heat treatment on welded joints using the shielded metal arc welding (smaw) on three different types of steel with different carbon ratios under constant conditions such as the welding current 120a, voltage 80v, diameter 10 mm and angle 60 degree. hardness tests chemical composition analysis were carried out and it was observed that, high carbon steel has the highest hardness of about 459 on maximum hv value, followed by the low carbon steel with the hardness of 316hv maximum and medium carbon experience the least value of 208hv. hardness increases with low carbon content as shown in the experimental results which deduced that the low carbon steel used was confirmed to be the high-strength-low-alloy steel of grade 8620-hsla-nickel-chromium-molybdenum steel. the microstructure of the base metal was analysed before heating to support the results of chemical analysis. nickel percentage of up to 0.147% and chromium 0.083%. molybdenum was just 0.030% which contributed in affecting the mechanical properties of the steel. keyword: heat treatments, welded joints, chemical compositions, microstructure, micro hardness 1 introduction alloy steels as engineering material become an essential class for diverse applications like construction of large ships, oil and gas transmission lines, offshore oil drilling platforms, pressure vessels, building construction, bridges, storage tanks [1]. with the technological development in advanced industries such as oil, automotive, aviation, piping networks, metallic bridges and other important industries, the need for a high-quality welding splice has increased [1][2][4]. many studies have shown that the welding joints are fractured when subjected to dynamic loads that start in the transition zones from the weld line. basic metal has been verified through several tests conducted in the field of fatigue tests [5]. the shape, dimension and reinforcement amount of the welded druse in welding line affect the extent of withstand of the different welding joints (whether these joints are spherical, perpendicular or otherwise) [6]. it is noticeable that whenever the values of transition angle increase between the welding line and the base metal, the values of extent withstand increases for spherical joints treated using this method. the mechanical methods varied to improve the sudden transition between the weld line and the base metal [7]. the grinding and rolling methods were used to make a smooth transition between the welding line and the base metal, and then reduce the concentration of the remaining stresses in this region [8]. the purpose of heat-treating carbon steel is to change the mechanical properties of steel, usually ductility, hardness, yield strength tensile strength and impact resistance. the electrical, corrosion and thermal conductivity are also slightly altered during heat treatment process [9]. the most common reasons that metals undergo heat treatment are to improve their strength, hardness, toughness, ductility, and corrosion resistance etc. annealing is a form of heat treatment that brings a metal closer to its equilibrium state. it softens metal, making it more workable and providing for greater ductility. the heat treatment develops hardness, softness, and improves the mechanical properties such as tensile strength, yield strength, ductility, corrosion resistance and creep rupture. these processes also help to improve machining effect and make them versatile. in the welding process, a high temperature is generated to melt the welding metal, the conditional interface between the welding metal and the welding zone is called fusion limits [9]. the temperature and cooling rate of the heat-affected area varies depending on the distance from the fusion line between the weld mailto:ummaabdullahi@abu.edu.ng abdullahi (2022): international journal of engineering materials and manufacture, 7(4), 89-94 90 metal and the heat-affected area. as a result of this difference, the microstructure varies, although the chemical structure is not different [10]. various mechanic and heat treatments are conducted on some metals that lead to reduce the stresses and distortions of the welded metals, these treatments include heating, pre-pressing, and heat treatment after the welding process [11]. these treatments reduce or remove the stresses and cracking, change the metallic properties of welded joints and to get the precise structure of the basic metal and metal fillers. the heat treatments affect (the temperature at which the metal is exposed, fixing period, the chemical composition of the metal, and cooling rate) [12]. adjusting the carbon content is the simplest way to change the mechanical properties of steel. additional changes are made possible by heat-treating, for instance, by accelerating the rate of cooling through the austenite-to-ferrite transformation point. the reason for this increasing hardness is the formation of a finer pearlite and ferrite microstructure that can be obtained during slow cooling in ambient air. in principle, when steel cools quickly, there is less time for carbon atoms to move through the lattices and form larger carbides. cooling even faster, for instance, by quenching the steel at about 1,000°c per minute, results in a complete depression of carbide formation and forces the undercooled ferrite to hold a large amount of carbon atoms in solution for which it actually has no room. tempering martensitic steel i.e., raising its temperature to a point such as 400°c and holding it for a time decreases the hardness and brittleness and produces a strong and tough steel. quench-and-temper heat treatments are applied at many different cooling rates, holding times, and temperatures; they constitute a very important means of controlling steel’s properties. large number of researchers work on this area but consider the thickness of the alloy steel tested to be constant. in this work, we are to study the influence of heat treatments on the chemical compositions and hardness property on welded joints after welding process using arc welding, where three samples of steel were used with different carbon ratios in constant conditions of current and voltages with varying thickness of the metal. 2 experimental works 2.1 sample preparation the three alloy steels of different carbon content were prepared by cleaning and grinding to remove the oil stains and other unwanted materials like dust and rust. 2.2 welding process the parts to be welded were brushed with stainless steel brush and finished with sandpaper and observed that all the oxidation layer were removed. a heat source was used, to heat the base metal to at least 387°c. when hot enough, the flame was moved aside but was kept on the part to maintain the temperature, and then the welding rod was applied and melted on contact with the hot metal part. test samples were prepared according to the standards to achieve an accurate result. figure 1: dimensions of the sample used in welding process figure 2: sample of welded steel picture https://www.britannica.com/science/carbon-chemical-element https://www.britannica.com/technology/quenching-materials-processing https://www.britannica.com/technology/tempering-metallurgy https://www.britannica.com/technology/martensitic-steel https://www.merriam-webster.com/dictionary/constitute effect of tempering treatment on the post-weld properties and chemical compositions of arc-welded alloy steels. 91 3 experimental results three different types of alloy steel were used in this work as low, medium and high carbon steel. the classification was based on the carbon content, but according to the level of main mechanical properties of practical importance as low carbon steels having carbon up to 0.25%, medium carbon steels having carbon between 0.25% to 0.55% and high carbon steels has carbon from 0.55% to ideally a maximum of 2.11% but commonly up to 1.5% max. in commercial steels. and this is the most commonly used commercial classification. table 1, 2 and 3 present the results of chemical composition of the three selected carbon steel. table 1: chemical composition of low carbon alloy steel c % 0.095 si % 0.235 mn % 0.90 p % 0.011 s % 0.013 cr % 0.0083 ni % 0.147 mo % 0.030 al % 0.039 cu % 0.208 co % 0.019 ti % ≤ 0.0010 nb % ≤ 0.0040 v % ≤0.0010 w % ≤0.010 pb % ≤0.0030 mg % ≤0.0010 b % 0.0008 sn % 0.012 zn % ≤0.0020 as % 0.020 bi % ≤0.0020 ca % 0.00003 ce % ≤0.0030 zr % ≤0.0015 la % ≤0.0010 fe % 98.2 table 2: chemical composition of medium carbon alloy steel c % 0.272 si % 0.108 mn % 0.449 p % 0.00089 s % 0.014 cr % 0.0027 ni % 0.029 mo % ≤ 0.0020 al % 0.042 cu % 0.016 co % 0.013 ti % ≤ 0.0010 nb % ≤ 0.0040 v % ≤0.0010 w % ≤0.010 pb % ≤0.0030 mg % ≤0.0010 b % ≤0.0005 sn % ≤0.010 zn % ≤0.0020 as % ≤0.0010 bi % 0.0046 ca % 0.011 ce % 0.0051 zr % ≤0.0015 la % 0.0017 fe % 99.0 table 3: chemical composition of high carbon alloy steel c % 0.99 si % 0.407 mn % 0.79 p % 0.046 s % 0.227 cr % 0.127 ni % 0.132 mo % 0.049 al % 0.127 cu % 0.065 co % 0.050 ti % 0.014 nb % 0.023 v % 0.0023 w % 0.414 pb % 0.132 mg % 0.175 b % 0.028 sn % 0.022 zn % ≥ 0.036 as % 0.036 bi % 0.0048 ca % ≥ 0.015 ce % 0.180 zr % ≤ 0.0015 la % -0.261 fe % ≤ 94.6 table 4: chemical composition & mechanical properties of welding electrode c % ≤ 0.12 si % ≤ 0.35 mn % 0.30-0.60 p % ≤ 0.040 s % ≤ 0.035 cr % 0.127 v % 0.132 mo % 0.049 mechanical properties of deposition metal δb (mpa) ≥ 420 δs (mpa) ≥330 δ5 (mpa) ≥17 a kv (j) 0 o c ≥ 47 3.1 effects of alloying elements and weldability it was confirmed from the experimental results that, alloying elements can alter carbon steel in several ways. alloying can affect micro-structures, heat-treatment conditions and mechanical properties. today’s technology with high-speed computers can foresee the properties and micro-structures of steel when it is cold-formed, heat treated, hot-rolled or alloyed. it was also proven that, improved properties such as high strength and weldability required in steel for certain engineering applications can only be achieved by adding other alloying elements as carbon steel alone will not serve the purpose because carbon’s inherent brittleness will make the weld brittle which is desirable. the solution is to reduce carbon and add other elements such as manganese or nickel. this is one way of making high strength steel with required weldability. fig. 3, 4 and 5 presents the metallography of high, medium and low carbon steel respectively. abdullahi (2022): international journal of engineering materials and manufacture, 7(4), 89-94 92 figure 3: optical micrograph of high carbon steel at (a) lower and (b) higher magnification for the base metal before tempering. figure 4: optical micrograph of medium carbon steel at (a) lower and (b) higher magnification for the base metal before tempering. figure 5: optical micrograph of low carbon steel at (a) lower and (b) higher magnification for the base metal before tempering. 3.2 hardness test base metal was tested to serve as a reference point and it was observed that, high carbon steel has the highest hardness of about 459 and 226.6 on maximum and minimum hv value respectively, followed by the low carbon steel with the hardness of 316 and 290.8 maximum and minimum hv respectively. medium carbon experience the least value of 208.1 and 183.1 maximum and minimum hv respectively. hardness increases with low carbon content as shown b effect of tempering treatment on the post-weld properties and chemical compositions of arc-welded alloy steels. 93 in the used low carbon steel. this deduced that the low carbon steel used was confirmed to be the high-strengthlow-alloy steel of grade 8620-hsla-nickel-chromium-molybdenum steel. this is as a result of having high percentage of nickel of up to 0.147% and it has the ability to increase corrosion, oxidation resistance and strength of the steel. however, chromium was found to be 0.083% in this particular steel and it has the capacity to affect the property of the steel by increasing its toughness, hardness and wear resistance. molybdenum was just 0.030% which can also play an important role in affecting any of the mechanical properties of the steel. in all the images of the microstructure, a fine pearlite structure was obtained for welded sample normalized at the selected temperature for all the steel grades. this leads to a consequential increase in hardness values. heat affected zone, contains evolution of grains with typical martensitic and pearlite phase within the interface. most area with haz contains lower hardness in the weld region with tendency of initial failure occurrence in service under the application of high load or severe stress. table 5: hardness value of the samples at different zone steel sample process fusion zone wm hv(kn/mm 2 ) heat affected zone haz hv(kn/mm 2 ) base metal bm hv(kn/mm 2 ) low carbon hardness before heat treatment 300 315 304 hardness after heat treatment at 550 o c 310 324 290 medium carbon hardness before heat treatment 190 200 196 hardness after heat treatment at 550 o c 230 200 207 high carbon hardness before heat treatment 355 310 343 hardness after heat treatment at 550 o c 370 345 330 3.3 micro-hardness test the welding samples were examined for accurate readings of the whole weld joint starting from the welding metal, the heat-affected area, then the base metal, and on both welding sides, at a distance of one mm between reading and another of the three welded joints (samples with performing heat treatments on which and samples without performing heat treatments). figure 6 presents a plot of hardness values of welded joints in different zones under the same working conditions for the high, medium and low carbon steel respectively. as the microstructure of weldment (wm) and the base metal has undergoes considerable changes because of the heating and cooling cycle of the welding process and is expected to have greater value of hardness than in the heat affected zone when the percentage of carbon increases as shown in table 3 and fig. 6 [8]. the reason behind the high hardness in the welding area when using steel (steel 321) is due to the union of chromium with carbon constituting chromium carbide (cr23c6) which has property of high hardness in the hardening line due to the spread of carbon from the base metal to the welding metal. (a) (b) (c) figure 6: plot of hardness values of welded joints in different zones under the same working conditions for (a) high carbon steel, (b) medium carbon steel, and (c) low carbon steel. 550 o c abdullahi (2022): international journal of engineering materials and manufacture, 7(4), 89-94 94 it was observed from fig. 6.0 that the variation in hardness value is because of the microstructural effect of carbon in terms of its volume fractions. hardness increases with increase in carbon content which has been controlled to prevent the steel from been brittle in nature. the reason for this increase in hardness leads to the formation of a finer pearlite and ferrite microstructure that was obtained during controlled cooling. 4 conclusions it was concluded that, heat treatment has a clear and significant effect on the chemical and mechanical properties of steel. the highest hardness is achieved in the haz and the average value is in the fusion zone for a welded joint of low-alloy steels. whereas, in high-alloy steels, the highest hardness is achieved in the fusion zone and the average value in the haz. the highest hardness values can be obtained in the heat affect zone, then the hardness values start relatively decrease in the base metal in contrast to the steel (steel 321), the highest hardness value is in the welding zone. heating and cooling of the welding line zone is expected to change the crystalline volume of the metal and the formation of a hard and fragile zone. acknowledgement the author acknowledged the support from tet fund ibr 2021 intervention through ahmadu bello university, zaria and appreciated the university for providing all the equipment used to conduct this research. rererences [1] hamid m. m. (2019). effect of heat treatments on the mechanical properties of welded joints of alloy steel by arc welding. diyala journal of engineering sciences, 12(02), 44-53. [2] erding w., renbo, s. and wenming x., (2019). effect of tempering temperature on microstructures and wear behavior of a 500 hb grade wear-resistant steel. metals 9(45), 1-14. [3] panel x. w., changbo, l., yuman, q., yanguo, l., zhinan, y., xiaoyan, l., mingming w. and fucheng z., (2022). effect of tempering temperature on microstructure and mechanical properties of nanostructured bainitic steel. material science and engineering: a, 832. [4] ragu, n. s., balasubramanian, v., malarvizhi, s., rao, a. g., (2015). effect of welding processes on mechanical and microstructural characteristics of high strength low alloy naval grade steel joints. defence technology 11, 308-317. [5] hakan, a. (2014). relationship between a bainitic structure and the hardness in the weld zone of the friction stir welded x80 api grade pipe-line steel. mater technol, 48 (1), 15802949. [6] jeshvaghani, r. a. and mirzaei, r. m. (2013). study of welding velocity and pulse frequency on microstructure and mechanical properties of pulsed gas metal arc welded high strength low alloy steel. materials & design, 51, 709-713. [7] salman, h. k., abbass m. k. and mohammed, a. h., (2015). effect of shot peening on the mechanical properties for welded joints of aluminium alloy 6061 -t6. ndmrp, 2, 43-56. [8] armentani, e. r. (2007). the effect of thermal properties and weld efficiency on residual stresses in welding. journal of achievements in materials and manufacturing engineering, 20(1-2), 319-322. [9] frost n. e., dugdale d. e. (1991). the propagation of fatigue cracks in sheet specimens. journal of sound & vibration, 69(4). [10] boumerzoug, z., raouache, e., delaunois, f. (2011). thermal cycle simulation of welding process in low carbon steel. materials science and engineering: a, 530, 191-195. [11] hastuhiko, o. tatsuya, s. and tadashi (2007). weld ability of high strength steel, (hss) sheets for automobiles, nippon steel technical, 95. [12] razzak, m. a. (2011). heat treatment and effects of cr and ni in low alloy steel. bulletin of materials science, 34, 1439-1445. international journal of engineering materials and manufacture (2021) 6(3) 141-151 https://doi.org/10.26776/ijemm.06.03.2021.05 f. g. natalino 1 , rusnaldy 2 , w. achmad 2 and s. arif 3 1 department of mechanical engineering, dili institute of technology, aimeti laran street, dili timor leste 1 doctorate program, department of mechanical engineering, diponegoro university, tembalang, semarang 50275, indonesia 2 department of mechanical engineering, diponegoro university, tembalang, semarang 50275, indonesia 3 politeknik manufacture ceper-jawa tengah indonesia e-mail: natalinofonseca81@gmail.com reference: natalino et al. (2021). investigate temperature preheating on the chill plate to identify surface characteristic on the ductile iron by sand casting. international journal of engineering materials and manufacture, 6(3), 141-151. investigate temperature preheating on the chill plate to identify surface characteristic on the ductile iron by sand casting f. g. natalino, rusnaldy, w. achmad and s. arif received: 27 february 2021 accepted: 30 april 2021 published: 15 july 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract the chilled casting method is widely used in the metal casting industry to accelerate the mold's cooling rate. this method is very suitable for surface hardening by depositing the elements contained in the chill material onto the surface of the object being cast. one of the factors that influence surface hardness characteristics is the diffusion temperature. this study aims to determine the microhardness, surface layer thickness, and the element contained on the surface. the main material produced into y-block is ductile cast iron, the chill material is ss 304 plate with a thickness of 0.2mm. however, before the liquid material is poured into a mold, the chill plate is inserted into the surface of the pattern in the mold, then the plate was preheated. the result showed that the highest preheating temperature has produced microstructure around the surface area namely eutectic carbide of (fecr)7c3, and (fecr)3c. sem-edx analysis shows that 7.13%cr is contained on the coating layer at a thickness of 0.020 mm and an average hardness of 700-900 hv. keywords: chill, casting, surface hardening, diffusion, preheating. 1 introduction in the metal foundry industry, the chilled casting method is used to harden the specimen surface hence it is resistant to high wear. chill is a high thermal conductivity material or component used to accelerate the cooling of metal in the mold. its use also increases productivity level, improves product defects in the surface area, and enhances the casted product's mechanical properties [1, 2]. the important factor to consider when using the chill for the surface hardening process is the composition structure in the material deposited onto the surface of the object being cast. therefore, to understand the formation of a deposited crystal structure that forms on the surface of the object, it is necessary to consider several phenomena, such as thermal, hydrodynamic, and physico-chemical [3]. until now, the chill has been widely used in aluminium, steel, and cast-iron casting. in aluminium casting, it is used to increase the rate of heat transfer from the surface of the chill to the object being cast and increase high hardness and smooth grain structures. the thicker the chill used, the greater the heat absorbed to the surface. therefore, in the solidification step, the casting material tends to cool more slowly at the centre area but quickly cools in the surface area [4-7]. cantavel et al. applied the chill method to steel casting. it is also used to characterize the surface of grey cast iron to make it hard. hardness is formed due to the diffusion of cr, ni, cu granular structures and other element content, thereby leading to the formation of white iron on the surface through very fast cooling [8-10]. chill can also be applied to camshaft casting using grey cast iron materials and ductile cast iron type gjs-400 used to increase cooling speed and the nodule count, thereby improving the microstructural properties [11, 12] and forming a eutectic carbide structure based on the alloying of the elements cr, mo, and ti through fast cooling rates [13-15]. manganese elements can also be used to make chills in ductile iron castings; however, they are unable to overcome the high hardness of the component surfaces to wear-resistant [1]. one of the materials commonly used for made the chill is copper or cast iron. the chill is placed on the surface of the pattern hole in the mold to adjust the fast-cooling rate on the surface of the specimen to be cast [16]. chill is made of copper material and combined with 1.5% cr to produce ferro carbide, thereby making it to wear and abrasion resistant. chill is usually used to coat the mold walls, hence the investigate temperature preheating on the chill plate to identify surface characteristic on the ductile iron by sand casting 142 liquid poured into the mold tends to rapidly transform the cooling process until there is fast solidification in the outer layer of the specimen. in this way, a dendritic granule structure easily forms in the skin layer due to the touch between the chill-coated mold wall and the solid specimen at high temperatures [17]. this is similar to the method used by ma qian et al, [18] whereby the mold walls were coated with ss 304 plate with the melted material poured into the mold. the result is the formation of eutectic carbides, namely (fecr)7c3, (fecr)3c, m3c, and m7 7c3. this eutectic carbide alloys formed are dependent on the chemical composition and cooling rate during solidification [19, 20]. the principle for the formation of iron carbide on the surface due to chill casting occurs towing to diffusion, which is a change in the composition of the deposited interfaces in the absence of the compound. factors that greatly influence the diffusion process are temperature and chemical bonding, where the higher of diffusion temperature, the better the binding ability of the deposited structure. low diffusion temperatures tend to have an adverse effect on hardened surfaces, thereby leading to surface morphology. furthermore, morphological characterization occurs by compacting and creating a needle-shaped hole in the surface. an atom's mobility on a surface depends on its energy, atom-surface interactions (chemical bonding), and surface temperature [21, 22]. as research conducted by m. ramadan, the annealing temperature above 700°c and holding time of 180min will diffuse the cr-ni-c element on the surface of the ductile iron, thereby increasing the hardness of the outer skin layer [23]. as for research from shi, z et al, using fe-cr-c as a hardfacing alloy then doped with ce elements to increase the ductility and toughness of materials, but it still did not increase the high hardness on the surface [24]. also, the element chromium is commonly used to bond preferentially to other elements to increase the hardness of the material [25, 26]. therefore, based on these reasons, the authors tried to perform surface hardening of the martensitic ductile cast iron material using the chilled casting method. the application of chilled cast iron focuses on the diffusion system between the chill material and the object surface. moreover, the atomic structure's attachment diffused from the chill material is influenced by the temperature in the area of interaction between the chill and the object surface. but there is also a research question that does the use of preheating on chill affect the hardness of the material, the thickness of the deposited atomic layer, and the formation of the microstructure? then the researchers decided the purpose of this study is to determine the microhardness, surface layer thickness, and the element contained on the surface with the difference in preheating temperature parameters that are distributed to the chill plate before the pouring process. 2 materials preparation and experimental procedure 2.1 material preparation the melting materials used to form martensitic ductile iron are scrap steel and iron. the ductile iron utilized in this study has a grade of 120-90-02 according to astm a536 standards, which is recommended for users to make wearresistant components such as gears, crankshafts, and others [27, 28]. furthermore, the shape of the casted sample is y-block, as shown in figures 1a and 1b, coded from s1 to s4. the material used to design the chill is austenitic stainlesssteel ss 304 plate with chemical composition, as shown in table 1. this composition material has according to standard astm a240 [29]. table 1: chemical composition of the stainless steel 304 sheet, astm a 240 [29]. c si mn ni cr fe 0.059 0.27 1,37 4,9 19,34 72,78 2.2 chill design process and its use the chill size and shape, according to the casted specimen as show in figure 1. the chill plate to be inserted into each specimen is one sheet, and the total number prepared for the 4 y-block specimens to be produced is 4 sheets. the chill manufacturing process is ss 304 plate cut into rectangles with a length and width of 270mm and 25mm and bent according to the specimen shape. the number of chill plates according to the variation of the preheating temperature, is shown in table 2. figure 1: pattern and chill plate; (a) the type and dimension of pattern; (b) 3d view of the pattern and position chill plate on the pattern; (c) chill plate. natalino et al. (2021): international journal of engineering materials and manufacture, 6(3), 141-151. 143 table 2: preheating parameters to identify different sample group. code of sample the thickness of the ss 304 plats preheating to surface of chill plate ( o c) s1 0.2 mm 500 o c s2 0.2 mm 700 o c s3 0.2 mm 900 o c s4 0.2 mm not preheating 2.3 mold preparation the mold is made of wooden slabs with a thickness of 20mm then formed into a box model with width, length and depth of 200mm, 300mm and 300mm respectively as show in figure 2. furthermore, the mold box is filled with high mesh class silica sand, mixed with water glass and methanol liquid, and stirred to homogeneity. in the next process, silica sand is poured into a box to create a hole trace pattern in accordance with the planned specimen shape and dried with co2 gas. however, before the silica sand is poured into the mold, the chill plate, y-block pattern, and thermocouple cable were first attached to the surface and positioned in the mold as show in figures 2a and 2b. this research made use of the ht-9815 thermocouple thermometer with 4 cables embedded into the sand and touched the surface of the chill plate. the function is used to detect the preheating temperature on the surface of the chill plate. figure 2: model of molding and specimen adjustment procedure. a) thermocouple cable installation touched to the chill plate; b) the sample arranged in the mold; c) plate chill condition on the surface of a tracing pattern. 2.4 preheating technique and pouring process the pouring process is carried out after the chill plate is preheated according to the sample code given as show in the table 2. it comprises three lpg gas cylinders and one o2 tube. the flow of gas and oxygen is sprayed through the four torch gas blenders that have been provided to point to the chill plate surface. hence the flame emitted to the plate surface needs to reach the target temperature. furthermore, nodular cast iron material, which has been melted at a temperature of 1500°c and was inoculated with 0.3-0.7% fe-si alloy then poured into the mold simultaneously. 3 testing and analysis 3.1 microstructure and mechanical properties examination the microstructure analysis is based on the astm 247 procedure, using an olympus bx41m optical microscope. after cutting, the specimen is polished with sandpaper (400, 800, 1500, and 2000), then etched with nital 98ml ethanol and 2ml nitric acid (hno3) based on the test guide on asm handbook vol. 9. the sample is cut without being exposed to high heat. furthermore, the sample size for the microstructure analysis and microhardness vickers test is 10 x 10 x 6mm [30, 31]. the test point areas are taken from each y-block specimen of six products as show in the table 2, and it has been given the codes of d1, d2, d3, and d4 and are cut in different areas as shown in figure 3a. these points are carried out on two sides, namely right site a and left site b, and each zone for each test sample has 9 test points, as shown in figure 3b. figure 3b shows that there are three group test focus locations, and each has three points. therefore, the total number of test points of microhardness vickers for each of all specimens (s1, s2, s3, and s4) is 72, then the results are summed to take the average value. testing for microhardness vickers using the mitutoyo hm-200, a vickers indenter and a 200gf load is used to determine the diffusion area's hardness layer. the test area in each sample for microhardness testing is the same as the microstructure. however, the distance between one test point and another is according to investigate temperature preheating on the chill plate to identify surface characteristic on the ductile iron by sand casting 144 standard astm e92 [32] about standard test method for vickers hardness of metallic materials, the microhardness test point starts from the edge towards the centre, and the number of indenter focus is three. figure 3: microstructure and microhardness vickers testing zone for every specimen y-block (a) location for focus analysis point (b) total of analysis point for each site zone (right site zone and left site zone) and for all sample testing after cutting. 3.2 coating and chemical distribution analysis the chemical composition of the ductile iron material that has been analyzed is in the middle area of the specimen. one y-block sample was taken to represent the entire specimen. the type of machine used is the arl optic emission spectrometer and types switzerland qtd-17. sem-edx is used to identify contaminated or unknown particle interactions between two materials from ductile cast iron and austenitic stainless steel (ss 304). the expected results are the percentage of element content deposited in the surface area will be detected by edx, and the coating layer's thickness on the surface measured by cross-section proses. furthermore, the measurement process for the diffusion thickness layer was processed by imagej, then measurements were taken ten times to take the average value. semedx type used is jeol jsm-6510la under a voltage of 20kv and a working distance of 16mm. analysis samples for cross-section and target diffusion are taken in the same area as the microhardness test as show in figure 3b. 4 results and discussion 4.1 the result of chemical composition on the ductile iron the chemical composition contained in the y-block ductile iron material includes 3.75%c, 0.47%mn, 2.03%si, 0.04%cr, 0.17%ni, 0.07%mo, 0.15%cu, 0.02%p, 0.15%ce, 0.06%mg and the other is fe. the results of this chemical composition analysis have responded to the material specifications for ductile cast iron according to standard of astm a 536 [27], which is recommended for the manufacture of wear-resistant components such as wheel pinions, gears, rollers and slides, these components are hard and wear-resistant on the surface but in the middle area must be ductile. 4.2 the formation of microstructure at the centre zone the microstructure analysis process associated with this research was carried out on the surface and the center zone. the microstructure found in the center zone for all samples (s1, s2, s3 and s4) shows that graphite nodules are uniformly and roundly formed, with a ferrite and perlite structure phase, as shown in figure 4. this graphite structure is under the specifications of the nodular cast iron material according to the astm a 536 standard [27] which is carried out through an inoculation process. in this nodularization process, magnesium (mg) alloy elements will be added to get a round of the graphite nodule so that the ductile iron base material can withstand tensile loads and impact loads according to researchs sasaki et al. [33] and yamamoto s et al. [34]. natalino et al. (2021): international journal of engineering materials and manufacture, 6(3), 141-151. 145 figure 4: (a) uniformity of graphite nodules before etched; (b) graphite nodule growth uniformly after etched and microscopic magnification 50x, (c) uniformity of graphite nodules with microscopic magnification 200x (g: graphite nodule, p: perlite and f: α-ferrite). the microstructure found in the surface and the centre area is different. figure 5 shows that the microstructure formation on specimen s4 is average and consists of a fully ferritic-matrix microstructure. therefore, with the rapid cooling process, eutectic carbide formation and a microstructure containing cementite, ferrite, and pearlite are very uniform and compact on the surface area. the use of fast cooling leads to the formation of graphite flakes, also known as martensite, in the surface area. the formation of this matrix structure is due to rapid cooling with the use of chill, therefore cementite occurs as a separate constituent in the matrix. in other cases, no diffusion layer was seen between the chill and the ductile iron interface. 4.3 the formation of microstructure at the surface the microstructure found in the surface and the center area is different. figure 5 show that the microstructure formation on specimen s4 is average and consists of a fully ferritic-matrix microstructure. therefore, with the rapid cooling process, eutectic carbide formation and a microstructure containing cementite, ferrite, and pearlite are very uniform and compact on the surface area, as explained by riposan l. et al. [25] that the graphite carbide structure is formed at the end of the solidification step in the ductile iron casting process [35, 36]. this occurs due to the rapid cooling of the interface through contraction between the cast liquid and the mold wall. the use of fast cooling leads to the formation of graphite flakes, also known as martensite, in the surface area. the formation of this matrix structure is due to rapid cooling with the use of chill, therefore cementite occurs as a separate constituent in the matrix. in other cases, no diffusion layer was seen between the chill and the ductile iron interface. the microstructure results for sample s1 are shown in figure 6, using a preheating temperature of 500°c, with very uniform ferro carbide in the edge area. also, the phase structure is randomly formed around the graphite nodule, which is visible because the main material used for all cast specimens is ductile iron. therefore, chill uses ss 304 material dominated by the composition elements of 19.34%cr and 4.9%ni (table 1). furthermore, at the interfacial austenite temperature, the chill and ductile iron succeeded in depositing cr and ni elements onto the ductile iron surface. the coating area is found to be a primary eutectic carbide or cr-carbide structure and is defined as (fecr)3c, where more details are explained in the edx analysis results. according to vander voort and baldwin, chromium carbide is formed with the cooling rate of solidification and the 5%cr composition. this carbide structure characteristic is very good for high wear-resistant [37]. figures 7 describe the sample s2 and the parameters using a preheating temperature of 700°c. the type of microstructure formed in the edge area is similar to the s1 sample, which is dominated by ferro carbide. the phase structure found near the coating area, and the perlite phase around the graphite nodule was acicular ferrite. a ledeburite phase forms in areas far from the diffusion region, while a structure eutectic carbide, also known as a white cast iron layer, is formed in the coating area. the eutectic carbide structure is called (fecr)7c3, and this structure is formed due to the diffusion of the cr and ni structures contained in the chill material at a preheating temperature of 700°c. the higher preheating temperature used in the chilled casting process has minimized the cooling rate at the chill and ductile iron interface, thereby preventing the formation of the iron carbide structure over low surface areas. the microstructure formation on the surface of the s3 specimen using the preheating temperature of 900°c as shown in figure 8, that the average microstructure consists of ferrous carbide and acicular ferrite near the diffusion zone with the small number of martensite phases. the microstructure growth in the diffusion zone is a very large eutectic carbide called (fecr)7c3 because the element cr diffuses too much to the surface. meanwhile, figure 8c shows that the diffusion layer formed on the surface has been shifting inward, this layer is the ledeburite phase or the socalled white cast iron layer which is dominant in the surface layer. these results as discussed by elorz p-sanz et al. [38]. diffusion element and layer thickness is discussed in the edx analysis. investigate temperature preheating on the chill plate to identify surface characteristic on the ductile iron by sand casting 146 figure 5: average microstructure formation on the surface of the samples (s4). (a. microscopic magnification 50x; b. microscopic magnification 100x, c. microscopic magnification 200x). (p=perlite; c=cementite; ec=eutectic carbide; m=martensite; l=ledeburite; f=ferrite; sg=spheroidal graphite). figure 6: average microstructure formation on the surface of the samples (s1). (a. sample s1 microscopic magnification 50x; b. microscopic magnification 100x; c. microscopic magnification 200x). p=perlite; l=ledeburite; f=ferrite; sg=spheroidal graphite). figure 7: average microstructure formation on the surface of the s2 samples. (a. sample s1 microscopic magnification 50x; b. microscopic magnification 100x; c. microscopic magnification 200x). (af=acicular ferrite, ec=eutectic carbide; l=ledeburite. figure 8: average microstructure formation on the surface of the s3 samples. (a. sample s1 microscopic magnification 50x; b. microscopic magnification 100x; c. microscopic magnification 200x). (af = acicular ferrite, ec=eutectic carbide; m=martensite; f=ferrite). natalino et al. (2021): international journal of engineering materials and manufacture, 6(3), 141-151. 147 4.4 edx and microhardness vickers test the results of sem-edx are taken from different temperature parameters, then they will be compared between the use of low and high temperatures preheating. also, samples using the preheating will be compared with samples that do not use the preheating. during the edx measurement, different areas were focused and the corresponding peaks are shown in figure 9 and 10. the results of samples that did not use preheating (s4) on the plate chill before the pouring process were elements of chromium and nickel which diffused onto the surface of the ductile iron is 0.08% cr and 0.06% ni as show in figures 9a and 10a). in the surface area, there are few cr and ni elements because these elements are mixed in the original ductile cast iron based on the astm 536 standard. it can be seen that cr and ni elements dominate all specimens in the centre and surface area. solidification temperature and elemental content affect the formation of ferro carbide in the matrix, besides that the cr and carbon content affect the atomic diffusion process in the m7c3 carbide matrix as described by li p. et al. [39]. the result of the diffusion contains 2.04%cr and a little 0.26%ni formed on the local of the surface of sample s1, quantify by edx as shown in figures 10b and 9b. the formation of the alloy composition elements is caused by the diffusion of the chill material elements when the preheating temperature distribution is 500°c to the surface of the chill plate. also, the average amount of microhardness achieved is 500hv. but there were also some test zones where the hardness value was found to be 700hv. the sample for use preheating temperature 700°c (s2), that the element diffusion formed on the surface layer consists of the content of 3.23%cr and 0.97%ni as shown in figures 10c and 9c. the alloy formation of the composition elements is higher than using a temperature of 500°c. after several microhardness tests were carried out that the average hardness value was 500 and certain areas had the highest hardness randomly reaching 800hv. sample s3 shows that the result of diffusion formed a cr content of 7.13% and 0.21%ni as shown in figures 10d and 9d. the alloy formation of the composition elements is higher than using temperatures of 700°c and 500°c. diffusion of cr and ni elements by using preheating temperature of 900°c to the chill face and ductile iron has an average microhardness is 900hv. the highest hardness values found in the few areas reached 939.3hv. by using the higher diffusion temperatures will increase higher hardness, as research conducted by ali günen et al [40]. details of the three edx spectra and different temperature preheating of the element formed on the surface zone are listed in table 3. edx weight ratio of elements deposition (cr, ni, and c) using three spectrums focused on three distinct areas then the average will be taken for comparison. edx detects the chromium value shown in table 3, that is for the s3 sample by using a preheating temperature of 900°c, the diffused chromium element is 7.13%, edx analysis results show that, in the surface area of nodular cast iron, iron carbide has been formed which is white mixed with grey colour as show in figure 9d, the type of the structure matrix is (fecr)7c3, as described by lagos m. a. et al [41] that iron-chromium carbide is very hard and good for wear, abrasion, corrosion and oxidation resistance. high chromium alloys will have an impact on the formation of chromium carbide with high hardness but depending on the content of carbon and other elements, the lower carbon value will reduce the formation of m7c3, m23c6, and m3c, in the coating area, as research conducted by jillah, a. et al. and li, y et al. [42, 43]. besides that, there is also a nickel (ni) content, its function is to extend the austenite field. nickel has no impact on the carbide formation process because the nickel content in the diffusion layer is very small. table 3: edx weight ratio of elements deposition (crni) using three spectrums focused on three distinct areas of surface for all specimens. temperature preheating carbon (c) silicon (si) chromium (cr) nickel (ni) weight (%) atomic (%) weight (%) atomic (%) weight (%) atomic (%) weight (%) atomic (%) not using preheating 18.67 47.53 1.98 2.16 0.13 0.08 0.11 0.06 500°c 26.01 57.93 1.65 1.57 3.93 2.04 0.56 0.26 700°c 14.77 40.83 1.79 2.11 5.06 3.23 1.72 0.97 900°c 27.88 46.58 0.78 0.87 11.85 7.13 0.40 0.21 investigate temperature preheating on the chill plate to identify surface characteristic on the ductile iron by sand casting 148 figure 9: energy dispersive x-ray (edx) analysis to quantify the deposition of atom on the diffusion zone. (a) sample s4, (b) sample s1, (c) sample s2, (d) sample s3. (m: martensite, mc: metal carbide). figure 10: energy dispersive x-ray (edx) analysis to quantify the deposition of atom on the surface. (a) sample s4, (b) sample s1, (c) sample s2, (d) sample s3. (m: martensite, mc: metal carbide). natalino et al. (2021): international journal of engineering materials and manufacture, 6(3), 141-151. 149 4.4 the thickness layer measurement the measurement process using sem cross-section for sample s4 were not using preheating before the pouring process, although not using preheating, the casting process still uses plate chill, so that the results can be compared with other parameters. the results obtained are an average thickness value of 0.011mm from ten measurements, while the deviation value was 1.72mm as show in figure 11a). sem cross-section analysis results for s1 samples using 500°c preheating temperature is an analysis of the position of the cross-section with an average thickness distance of 0.012mm from 10 measurements and a deviation value of 0.001mm. measurements were made on the white layer area, as shown in figure 11b. the results for s2 samples with a preheating temperature of 700°c obtained an average thickness of coating layer of 0.015mm from 10 measurements and a deviation value of 1.165mm. measurements were made on the white layer area as show in figure 11c). meanwhile, there is a deposition of cr and ni elements on the surface, resulting in high hardness. things related to the research of silva leandro j. da l et al. [44] and janicki d. et al. [45] that the good bonding of the elements and the number of coated particles on the surface largely determine wear performance. the results for sample s3 using a preheating temperature of 900°c obtained an average layer thickness on the white layer at the edge of the surface areas, reaching 0.020mm from 10 measurements to obtain the average value. the deviation value is 0.001mm, as shown in figure 11d. by using a preheating temperature of 900 has produced a high thickness of the iron carbide layer when compared to using a lower preheating temperature. these results will predict resistance to contact fatigue loads on components, based on the research of li w. et al. [46] and rajinikanth v. et al. [47] that the elements that diffuse to the surface are deeper or thicker, this will be occurring resistant to contact fatigue loads. figure 11: the thickness layer analysis by cross-section testing. (a) thickness layer of sample not using preheating process (s4), (b) thickness layer of the sample by using temperatur preheating 500°c (s1), (c) the thickness layer of the sample by using temperatur preheating 700°c (s2), (d) the thickness layer of the sample by using temperatur preheating 900°c (s3). 5 conclusions this research described investigations related to variations in preheating temperature on chill plates against hardness values, surface layer thickness, and chemical diffusion on ductile cast iron surfaces. therefore, the following conclusions were drawn: 1. by using the preheating method for the chill plate before the pouring process, it has resulted in a different surface layer by not using preheating. 2. compared with do not use preheating proses on the chill plate, the formation of a carbide eutectic structure on the surface of y-block specimens with a thickness of 0.012mm to 0.020mm, increases the hardness up to 900hv. furthermore, by preheating, it can diffuse chromium elements onto the ductile iron surface to form (fecr)3 c and (fecr)7c3 structures called ledeburite structures, which are categorized as white cast iron with a high hardness. investigate temperature preheating on the chill plate to identify surface characteristic on the ductile iron by sand casting 150 3. high preheating temperatures increase the thickness of the hardness layer on the ductile iron surface and raise the high hardness value on the surface. the higher preheating temperature used, the greater the chromium element's ability that diffuses to the ductile iron surface to reach 7.13%. furthermore, the increase in the chromium element's value leads to the formation of a(fecr)7c3 structure, thereby increasing the high hardness value on the surface. 4. the results obtained, this method can be applied to surface hardening of components that require high wear resistance such as gears, hot rolling mills, crankshafts, bearings, cylinder blocks, and others. acknowledgement the study was carried out with partial financial support provided by the dili institute of technology timor leste and fundo de desenvolvimento do capital humano (fdch) timor leste. we also thank to diponegoro university and politeknik manufacture ceper for supporting the laboratory of testing. references 1. lyle r. jenkins. properties and selection: irons, steels, and high-performance alloys, 10th edition. asm international the materials information company, united state of america, 1992, pp. 224-238. 2. wang, ben l., morris, dallin s., farshid, s., lortz, s., ma, q., wang, c., chen, yong-ching., sanders, p.: rolling contact fatigue study of chilled and quenched/tempered ductile iron compared with aisi 1080 steel, wear. elsevier, 2021, 478–479, p. 203890. 3. durand-charre, m. microstructure of steels and cast irons. springerverlag berlin heidelberg new york cataloging-in-publication, germany, 2004, pp. 419. 4. wankhede, d.m. narkhede, b.e., and mahajan, s.k. investigation of casting parameters and external chills performance on mechanical properties of aluminum silicon alloy (lm6) castings 4–8, 2017. 5. wankhede, d.m. narkhede, b.e., mahajan, s.k., and choudhari, c.m. influence of pouring temperature and external chills on mechanical properties of aluminum silicon alloy castings. mater. today proc. 5, 2018, pp. 17627–17635. 6. pavithra, h.s. and anantha prasad, m.g. study on microstructure and mechanical properties of al/sio2/c hybrid metal matrix composite, with the influence of chills. mater. today proc. 5, 2018, pp. 6053–6058. 7. gafur, m.a., haque, m.n. and prabhu, k.n. effect of chill thickness and superheat on casting/chill interfacial heat transfer during solidification of commercially pure aluminium. j. mater. process. technol. 133, 2003, pp. 257–265. 8. kanthavel, k., arunkumar, k. and vivek, s. investigation of chill performance in steel casting process using response surface methodology. procedia eng. 97, 2014, pp. 329–337. 9. fischer, s.f., muschna, s., bührig-polaczek, a. and bünck, m. in-situ surface hardening of cast iron by surface layer metallurgy. mater. sci. eng. a 615, 2014, pp. 61–69. 10. oloyede, o., cochrane, r.f. and mullis, a.m. effect of rapid solidification on the microstructure and microhardness of bs1452 grade 250 hypoeutectic grey cast iron. j. alloys compd. 707, 2017, pp. 347–350. 11. kumruoǧlu, l.c. mechanical and microstructure properties of chilled cast iron camshaft: experimental and computer aided evaluation. mater. des. 30, 2009, pp. 927–938. 12. sonne, m.r., frandsen, j.o. and hattel, j.h. comparison of residual stresses in sandand chill casting of ductile cast iron wind turbine main shafts. iop conf. ser. mater. sci. eng. 2015 pp. 84. 13. dobrovska, j., kavicka, f., stransky, k., sekanina, b., and stetina, j. numerical optimization of the method of cooling of a massive casting of ductile cast-iron. aip conf. proc. 1252, 2010, pp. 578–585. 14. hayrynen, k.l. and brandenberg, k.r. carbidic austempered ductile iron (cadi). trans. am. foundry soc. 111, 2003, pp. 1–6. 15. labrecque, c., gagné, m., javaid, a. and sahoo, m. production and properties of thin-wall ductile iron castings. int. j. cast met. res. 16, 2003, pp. 313–317. 16. hurst s. metal casting appropriate technology in the small foundry. intermediate technology publications ltd, london-uk, 1996, pp.240. 17. laino, s., sikora, j.a. and dommarco, r.c. development of wear resistant carbidic austempered ductile iron (cadi). wear 265, 2008, pp. 1–7. 18. qian, m., harada, s., kuroshima, y., shoji harada and h. nagayoshi. surface hardening of ductile cast iron using stainless steel. mater. sci. eng. a 208, 1996, pp. 88–92. 19. radzikowska, j.m. and foundry, t. metallography and microstructures of cast iron, asm handbook, volume metallography and microstructures. asm international, kingdom, 2004, pp 565-587. 20. könig, mathias, ingvar l svensson, and wessén m. the influence of alloying elements on chill formation in cgi. 457, 2011, pp. 126–31. 21. mattox, d.m. asm handbook vol. 5 surface engineering, 9th edition. asm international, united state of america 1994, pp. 1538-1539. natalino et al. (2021): international journal of engineering materials and manufacture, 6(3), 141-151. 151 22. gao, x., jiang, z., wei, d., jiao, s., chen, d., xu, j., zhang, x. and gong, d. effects of temperature and strain rate on microstructure and mechanical properties of high chromium cast iron/low carbon steel bimetal prepared by hot diffusion-compression bonding. mater. des. 63, 2014, pp. 650–657. 23. ramadan, m. interface structure and elements diffusion of as-cast and annealed ductile iron/stainless steel bimetal castings. engineering, technology & applied science research 8 (2): 2018, pp. 2709–14. 24. shi z., shao, w., rao, l., hu, t., xing, x., zhou, y., liu, s. and yang q. effects of ce doping on mechanical properties of m7c3 carbides in hypereutectic fe–cr–c hardfacing alloy. journal of alloys and compounds 850: 156656, 2021. 25. riposan l., stan s., chisamera m., neacsu l., maria cojocaru a., stefan e., and stan i. simultaneous thermal and contraction/expansion curves analysis for solidification control of cast irons. china foundry 17 (2): 2020, 96–110. 26. smita g. rao, rui shu, robert boyd, grzgorz greczynski, arnaud le febvrier, per eklund. phase formation and structural evolution of multicomponent (crfeco)ny film. building and environment 184 (august): 107229, 2021. 27. astm a 536. standard specification for ductile iron casting, 2004. 28. william d. callister and david g. rethwisch. materials science and engineering an intruduction, eighth edition, jhon wiley and sons, inc, united states of america, 2010, pp. 403. 29. astm a240. standard specification for chromium and chromium-nickel stainless steel plate, sheet, and strip for pressure vessels and for general applications. astm international, united state of america, 2015. 30. radzikowska, janina m. and the foundry. metallography and microstructures of cast iron. asm handbook, volume 9: metallography and microstructures. kingdom: asm internasional 2004, pp. 565-587. 31. astm a247 03a. standard test method for evaluating the microstructure of graphite in iron castings 1, american society for testing and materials, 1998. 32. astm-e92. standard test method for vickers hardness of metallic materials. astm international 82 (reapproved): 1997, 1–10. 33. gou, j., wang, y., sun, j. and li, x. bending strength and wear behavior of fe-cr-c-b hardfacing alloys with and without rare earth oxide nanoparticles. surf. coatings technol. 311, 2017, pp. 113–126. 34. yamamoto, s., chang, b., kawano, y., ozaki, r., murakami, y. mechanism of nodularization of graphite in cast irons treated with magnesium. metal science 12 (5), 1978, 239–46. 35. sasaki, hideaki, matsumoto, m. nodulization of graphite in cast iron by addition of plastic resin.” materials letters 270: 127708, 2020. 36. liu j. h., jian s. y., xue b. z., bin g. f., hai t. x., gui x. z., and peng h. y. precipitation and evolution of nodular graphite during solidification process of ductile iron. china foundry 17 (4): 2020, 260–71. 37. voort, v., baldwin, w. metallography and microstructures asm handbook, asm international. asm international, united state of america, 2004, pp. 565-568. 38. pero-sanz elorz, josé antonio, daniel fernández gonzález, and luis felipe verdeja. physical metallurgy of cast irons. physical metallurgy of cast irons, springer international publishing ag, p. 153-190, 2020. 39. li p., yang, y., shen, d., gong, m., tian, c. and tong, w. mechanical behavior and microstructure of hypereutectic high chromium cast iron: the combined effects of tungsten, manganese and molybdenum additions. journal of materials research and technology 9 (3), 2020. 40. günen, a., kalkandelen, m. karahan, i. h., kurt, b., kanca, e., gök, m. s. and karakaş, m. s. properties and corrosion behavior of chromium and vanadium carbide composite coatings produced on ductile cast iron by thermoreactive diffusion technique. journal of engineering materials and technology, transactions of the asme 142 (4), 2020. 41. lagos, m. a. et al.: fabrication of chromium carbide cermets by electric resistance sintering process: processing, microstructure and mechanical properties’, international journal of refractory metals and hard materials. elsevier ltd, 95 (october 2020), p. 105417, 2021. 42. jilleh, a., babu, n. k., thota, v., anis, a. l., harun, m. k. and talari, m. k. microstructural and wear investigation of high chromium white cast iron hardfacing alloys deposited on carbon steel. journal of alloys and compounds 857: 157472, 2021. 43. li, y., shen, d., xu, n. and tong, w. cladding high chromium cast irons on low carbon steel: microstructure and mechanical properties. journal of materials research and technology 9 (3), 2020, 3856–64. 44. silva, leandro j. da, cristiano j. scheuer, and ana sofia c.m. d’oliveira. effect of microstructure on wear performance of nicrsibc coatings. wear 428–429 (march), 2019, 387–94. 45. janicki, d.: the friction and wear behaviour of in-situ titanium carbide reinforced composite layers manufactured on ductile cast iron by laser surface alloying, surface and coatings technology. elsevier b.v., 406 (november), 2021, p. 126634. 46. li, w., deng, s. and liu, b.: experimental study on the influence of different carburized layer depth on gear contact fatigue strength, engineering failure analysis. elsevier ltd, 107, p. 104225, 2020. 47. rajinikanth, v. et al. (2021) ‘microstructural investigation of rolling contact fatigue (rcf) on a failed planetary gear of a windmill gearbox’, engineering failure analysis. elsevier ltd, 121(october 2020), p. 105167. international journal of engineering materials and manufacture (2019) 4(4) 137-145 https://doi.org/10.26776/ijemm.04.04.2019.01 abdul md mazid 1 , md. shahanur hasan 2 and kazi badrul ahsan 3 school of engineering and technology, central queensland university, australia e-mails: 1 a.mazid@cqu.edu.au; 2 m.hasan@cqu.edu.au; 3 kazi.badrul@yahoo.com reference: mazid, m. a., hasan, m. s. and ahsan, k. b. (2019). an investigation on optimum process parameters in terms of surface roughness for turning titanium alloy ti-6al-4v using coated carbide. international journal of engineering materials and manufacture, 4(4), 137-145. an investigation on optimum process parameters in terms of surface roughness for turning titanium alloy ti-6al-4v using coated carbide abdul md mazid, md shahanur hasan and kazi badrul ahsan received: 20 september 2019 accepted: 20 november 2019 published: 15 december 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract the quality of machined parts and the productivity of machining that leads to economic sustainability. these factors are also vital for machinability improvement for materials, as well as, for economically sustainable manufacturing. due to their poor machinability titanium alloys (ti-alloys) are categorised as difficult-to-machine materials. for the same reason products made of ti-alloys are highly expensive and are used only in strategic and sophisticated industries. a series of real-life experimental investigations was carried out to reveal the economic optimal zones of machining parameters that can produce the best possible surface roughness in machining ti-6al-4v alloy, using the coated carbide cutting tools, in shortest period of operation time. as the output of the research, for using the coated carbide tools for machining the investigated ti-alloy, optimal zones of cutting speed, feed rate and depth of cut have been proposed and presented in graphical format. the current research revealed that all three groups (with nose radius nr = 0.4, 0.8, and 1.2 mm) of coated carbide tools are capable to produce best surface finish, ranging between ra = 0.5 1.0 µm, with cutting speed starting at v = 60 m/min and beyond at least up to v = 250 m/min while keeping the feed rate and depth of cut as constants as f = 0.1 mm/rev and d = 0.5 mm. the data on the graphs may help researchers, engineers and manufacturers to select optimal economic cutting speed, feed rate and depth of cut to achieve a certain level of surface roughness of machined components as assigned by the product designer on the part drawing. this reduces the production cost substantially, reduces number of defect products and improves product quality for machined parts. keywords: titanium alloy, machining parameters, optimisation, surface roughness, carbide tools. 1 introduction and literature review titanium (ti) and ti-alloys are non-ferrous metals possessing high “strength-versus-mass” ratio and high strength properties and toughness which are maintained even at very high temperature. the ti-alloys possess exceptional wear and corrosion resistance in all possible hostile environments. titanium products are expensive due to their poor machinability, as well as, extraction processes of titanium (ti) are more complex than many other widely used metals. the major reason of applicability of ti-alloys using in aircraft and aerospace machine building is that, the ti-alloys have approximately one-third higher “strength-versus-mass” ratio than any other potential materials (veiga and davim, 2012). but it is extremely difficult to achieve desirable surface finish (ra), machining accuracy, as well as, surface quality due to the poor machinability of ti-alloys. machinability of materials is assessed by various factors such as the cutting tool life used for machining a material, surface roughness, surface integrity (sub-layer residual stresses, microhardness, and metallographic phase stability), part geometry and dimensional accuracy obtained, amount of heat generated in the cutting zone, cutting forces developed and material removal rate (mrr) and amount of electrical energy required for machining (machado and walbank, 1990; rahman et al., 2003; ezugwu and wang, 1997; davim, 2010; yang and liu, 2007; ogedengbe, 2019). mechanical and metallurgical properties of materials largely contribute to their machinability (davim, 2010). during machining of ti-alloys using conventional cutting tools at the range of cutting speed v = 60 – 75 m/min it demonstrates very high cutting tool wear rate. some researchers suggested, using carbide, ceramic, and diamond cutters for cutting ti-alloys, higher cutting speeds can be achieved (gatto and iuliano, 1997). but at higher cutting speed and under high temperature growth at the cutting zone, several researchers (machado and walbank, 1990; rahman et al., 2003; ezugwu and wang, 1997; yang and liu, 2007; hua and shivpuri, 2004) expressed opinion that these tool materials exhibit increased chemical reactivity with titanium atoms. as stated by veiga et al (2012) and other researchers low heat transition rate (varying in the an investigation on optimum process parameters in terms of surface roughness for turning titanium alloy ti-6al-4v 138 range of 5.5 w/mk to 19.0 w/mk in variation of temperature ranging from room temperature to 800c, while that is approximately 43 w/mk for carbon steels) of ti-alloys causes the high heat generation in cutting zone, which in turn adversely affects the surface finish, residual stress growth and phase transformation in the sub-layer machined surface. due to its very high cost (manufacturing and material), ti-alloys have limited applications only within aircraft, spacecraft, medical devices and surgery, motorsport, premium sports equipment, consumer electronics and defence industries (rahman et al., 2003; ezugwu and wang, 1997). manufacturing cost can be reduced substantially if optimal economic machining parameters are used for machining. poor machinability of ti and ti-alloys was noted in europe, america and russia starting from their early applications after the world war ii. due to several disadvantages and complexities in all phases of processing application of ti-alloys for general purpose machine building is still a luxurious topic. high reactivity with sulphur, carbon, oxygen, and nitrogen, forming insoluble compounds and sequestering them in slag makes the machinability of ti and ti-alloys poorer. poor machinability of ti and ti-alloys is now a global problem that worth to study, in depth, with a notion to develop optimal economic cutting parameters/regimes/conditions and machining processes, adequate cutting tool materials, adequate machine tools selection and jigs-fixtures that can yield cheaper and more affordable ti and ti-alloys products. although applications of ti-alloys started in europe, america and russia just after world war ii, unfortunately not significant achievement in their machining has been achieved. that is why ti-alloys are not widely used in general machine building and many other engineering purposes. the major goal of the current research project was set to establish optimal economic cutting regimes/parameters (optimal zones of cutting speed (v m/min), feed rates (f mm/rev) and optimal depth of cut (d mm)) for the most commonly used in aerospace machine building α-β ti-alloy, ti-6al-4v, using widely available coated carbide cutting tools with variable nose radius. this works was performed by the way of physical experimentation. the series of experiments is supposed to be repeated several times until the stable data are achieved. the advantage of this method is that the results obtained are purely physical (and not simulation based) taking into account all real-life scenario of machining process and the method is reliable though a bit laborious and time consuming. the method does not use any assumed or accepted data but all of the physical situation of the cutting process, the workpiece material, machine tool and the cutting tool conditions. the optimal cutting regimes will certainly help manufacturing industries to produce parts with least possible manufacturing cost and to reduce number of defect products, thus leading to economic sustainability. 2 relevant background 2.1 titanium alloys a briefing pure titanium (ti) is not suitable for using it in machine building purposes because it changes rapidly its microstructural phase with the change of temperature; the process is called allotropic transformation. at about 882°c temperature ti undergoes an allotropic transformation changing from alpha-phase (α-phase) to beta-phase (β-phase) that affects the overall physio-mechanical properties of materials (rahman et al., 2003; ezugwu and wang, 1997; yang and liu, 2007). some additional inclusions to pure ti allow manipulating the allotropic temperature towards positive side of its applications. these inclusions are called stabilisers and the stabilisers for ti-alloys are classified according to phase as follows (veiga and vadim, 2012; machado and walbank, 1990): • alpha (α) stabilising elements: al, o, n, and c; these inclusions help to increase the temperature of allotropic transformation preventing phase transformation which in turn improves the usability of ti-alloys; • beta (β) stabilising elements: mo, cr, mn, ni, v, fe, nb, cu, and si; these elements help to decrease temperature of phase transformation; • neutral stabilisers/elements: sn and zr and these do not have much influence on temperature transformation. accordingly, ti and ti-alloys are classified into following four main groups: • unalloyed ti that has excellent corrosion resistance but lower strength properties. • alpha (α) and near-alpha alloys: these alloys contain α-stabiliser and it produces excellent creep resistance. • alpha-beta (α-β) alloys: these alloys contain mixture of both alpha and beta stabilisers and have the largest application in aerospace machine building; ti-6al-4v is the most common and popular alloy in this group. • beta alloys (β): these alloys contain significant quantities of beta-stabilisers and produce high density accordingly high hardness. among all titanium alloys, α-β alloy ti-6al-4v has higher application (about 60% of all titanium products) in aircrafts, jet engines, racing cars, high performance reciprocating engines, compressor disks, gas turbine engines, casing, etc (ezugwu et al., 2003; ezugwu and wang, 1997). on top of the mentioned properties, the important one of these alloys, suitable in these applications, is high fatigue strength. titanium parts manufactured by turning operations are often shafts subjected to cyclic loading, for which fatigue and pulsating fatigue strength is vital. titanium is also often used for high temperature applications, at which the fatigue strength of the materials drops significantly (davim, 2010). it is therefore important that appropriate manufacturing processes are utilised that do not significantly reduce the fatigue properties of the parts. the surface roughness of a component affects its fatigue strength (ataollah j., et al., 2008). higher surface roughness increases crack initiation which eventually decreases fatigue strength. http://en.wikipedia.org/wiki/slag mazid, hasan and ahsan (2019): international journal of engineering materials and manufacture, 4(4), 137-145 139 2.2 parameters for quality machined products in machine manufacturing industry the quality of machined parts is assessed by the three major physical parameters which are surface roughness, sub-surface integrity, and geometric and dimensional accuracy. all these parameters must have to be satisfied for a part to be accepted as good. deviation of any of these parameters makes the part to be rejected and not to be used in assembly of a machine unit. from early ages of machine manufacturing it has been well accepted that the surface quality (surface roughness and sub-surface integrity) plays a vital role in the industry. this has been again stated recently by ancio et al. (2015) proficiently. required surface roughness values or class of surface roughness is assigned by the designer on the part/detail drawings. assigning unnecessary higher class of surface roughness makes a product unnecessary costly; this may increase the production cost of a machine and may hinder sustainability of a company. similarly, it is also essential to select a suitable machine tool for machining a part that is capable to achieve the designed surface roughness with cost effectiveness. the level of sub-surface residual stresses developed by the action of cutting forces and generated heat decide the surface integrity of machined parts. these may cause dislocation in crystal lattice of metal causing eventually micro-crack development which in turn adversely affects the fatigue life of a part. phase transfer in crystal structure is also possible in some cases due to the same reasons, which affects the microstructure of metal affecting the surface integrity of machine parts (schneider, f. et al., 2016). required geometric shape and dimensional accuracy are essential for assembly purposes for functionality of the machine unit. functional dimensions of a part are designed with necessary tolerances for fit and suitable class of surface roughness. again, it is mentionable that unnecessary lower level of tolerances or better surface roughness makes it difficult to achieve the assigned level. certainly, this increases the production cost unnecessary and unwisely and companies may need to compromise with economic sustainability. 3 experimental methodology it has been indicated by astakhov (1999) in his book metal cutting mechanics so appropriately that manufacturing industries rely completely on the thumb-rule empirical machining parameters provided by the cutting tool manufacturers. and they must rely on them because they are not supposed to have enough opportunity of scientific support for the better way out which could provide best possible quality and least possible manufacturing cost. these provided data cover a wider range of applications of their products for their larger commercial interest. but experience and observations have shown that these data barely satisfy the exactly required machining parameters (for a certain material using a certain cutting tool) which can yield the best possible machining quality (surface roughness and surface integrity) and least possible machining time and manufacturing cost. as the literature survey shows that a huge amount of works has been dedicated to the machinability assessment of various metals and alloys during the past twenty to thirty years, but not much concentration has been deployed on optimal economic machining parameters (in the sense of both better machining quality and lower machining costs) unfortunately. again, there have been a good amount of research works on optimisation of machining parameters published but most of them are simulation (kuttolmadom m., et al., 2017) or empirical and statistical model based and these do barely present the real case scenario of physical machining process of a material using a certain cutting tool with certain geometry. out of others, the repetitive physical machining methodology can provide more accurate and proficient results for determining optimal economic machining parameters for individual cutting tool for machining a certain material. this involves a series of time consuming and laborious experimental investigation that carries on a series of real-life machining experiments with many samples. the major advantage of this methodology is that this takes into consideration all involved details, properties, scenario and parameters of the machining process and thus it is possible to avoid unknown effects of the system. in brief, this methodology involves machining of samples with a set of cutting parameters (v, f, d). in each machining operation, for a batch of samples, one of the parameters (such as v) is varied in a large range (covering all possible values) but keeping the rest two parameters (f and d) constant for the first instant. the obtained surface roughness values (ra or rz) for each of the machined samples should be measured in three lines (approximately at an equal distance and in reality, it is at every 120c around the circumference) along the axis of a sample around the cylindrical machined surface. the average of the three values of ra (or rz) is the acceptable value for surface roughness obtained for the investigated sample. the several experimented values of v and obtained respectable values of ra should be plotted on a graph. this graph should show a zone of acceptable optimal values of v. in the second stage, the next batch of samples is machined varying a second parameter (such as f) while the rest two parameters (v and d) are kept constant. but this time the value of the constant v should be accepted from the previously obtained from the zone of optimal values of v. similarly, the cycle of experimentation process should continue repeatedly a number of times until a satisfactory range of optimal cutting parameters (v, f, d) is achieved. despite it is a laborious and long process, the output obtained should be a reasonably perfect one, because every influential factor participating in the machining process is considered naturally. the practicality of the methodology and the essence of it have been recently demonstrated in the research output of a final year mechanical engineering student's project supervised by the first author. in his project the student investigated the variation of production cost for machining of a mild steel stepped shaft. the shaft was machined using the optimal economic machining parameters developed by the proposed physical machining method and that produced in local manufacturing an investigation on optimum process parameters in terms of surface roughness for turning titanium alloy ti-6al-4v 140 companies. the student stated in his project report: “the production costing process and comparisons determined that the resulting cost of the specified component was on average $161.11 for production at the university engineering workshop using optimised cutting parameters compared to an average of $226.36 for local engineering manufacturing companies." the above example clearly evidenced the financial benefit of the stated physical machining methodology for machining parameter optimisation. procedures of the methodology are described in the following sections of experimentation. 4 experimental investigation to accomplish the planned experiments using the real-life physical machining methodology the resources used are in-home available lathe harrison m400 for turning operations and taylor hobson surtronic 3+ instrument – hb 103 for surface roughness assessment. these resources, in performances, are shown in figures 1 and 2 respectively. the 3-jaw self-centred chuck for universal lathes was used to clamp the 50 mm diameter ti-6al-4v shaft of length 450 mm on the harrison m400 lathe for turning operations as shown in figure 1. the lathe is driven by 7.5 kw motor which provides 1500 rpm. this lathe has a wide scope to set up cutting parameters, including eighteen different rotational speeds which range from 40 to 2000 rpm, and fifteen feed rate options ranging from 0.04 to 2.84 mm/rev. as it is usually used for ti-alloys machining in the industry and easily available, seco ts2000 coated carbide inserts have been used for experiments. the specifications of these coated carbide inserts are cnmg 120404-mf1, ts2000 (8 cutting edge), cnmg 120408-mf1, ts2000 (8 cutting edge, and cnmg 120412-mf4, ts2000 (8 cutting edge) with nose radii 0.4 mm, 0.8 mm and 1.2 mm respectively. the tool holder used (figure 3) for mounting the cutting insert was of seco model pclnr2525m12jet. geometry of the inserts used, mentioned above, was as rake angle -6°, inclination angle -6°, lead angle 95°, clearance angle 0°, nose angle 80° and nose radius 0.4 mm, 0.8 mm and 1.2 mm with chip breaker. during the machining process a cutting fluid of caltex (trusol gp), as available, has been applied to keep the cutting zone free from excessive heat and to reduce friction and easy swarf removal. the ti-6al-4v 50 mm diameter bar under investigation was marked to divide it into samples of 25 mm length (figure 4) and the samples were given arbitrary sample numbers. the surtronic 3+ instrument was used for measuring values of surface roughness (ra) on each machined surface of the ti-alloy bar (figure 2). this instrument uses stylus type technology and it is a portable and self-contained machine for use in both workshop and laboratory and is able to measure the surface finish of machined components with high enough accuracy. technical specifications of the surtronic 3+ instrument are: maximum traverse length: 25.4 mm, cut-off values (mm): 0.25, 0.8, 2.5 mm, evaluation lengths are x1, x3, x5, x10 cut-off length, parameters available: ra, rq, rz (din), ry, sm; filter types: iso-2cr or gaussian selectable, traverse speed: 1 mm/sec. as planned, three series of experiments have been conducted, one for each of the accepted nose radii 0.4 mm, 0.8 mm, and 1.2 mm. figure 1: machining experiment on harrison m400 figure 2: surface roughness assessment using surtronic 3+ figure 3: a coated carbide inserts clamped in the tool holder figure 4: one half of the ti-6al-4v specimen bar mazid, hasan and ahsan (2019): international journal of engineering materials and manufacture, 4(4), 137-145 141 4.1 experiment for economic cutting speed zone for variable nose radius for the first series of experiments the samples (8 samples x 3 groups) of the ti-6al-4v bar were machined with various cutting speeds ranging within v = 12 – 250 m/min using the coated carbide inserts with nose radii nr = 0.4 mm, nr = 0.8 mm, and nr = 1.2 mm while keeping the feed rate (f = 0.1 mm/rev) constant and the constant depth of cut (d = 0.5 mm) for all of the samples. as the draft tabulated data (not included in this paper) display there been twenty-four samples machined for three groups of experiments. three surface roughness values (ra) around the circumference for each of the samples were measured using the mentioned surtronic 3+ instrument (figure 2). the average of these ra values was calculated for each of the machined samples and accepted as the effective value of ra in µm. the graphs in figure. 5 show the relationship of obtained values of surface roughness (ra) for various cutting speeds (v) used. as the graphs reveal, the optimal cutting speed zone (vopt) for ti-6al-4v samples ranges roughly between the values of v = 60-160 m/min for the coated carbide cutter with all three different nose radii. the parameters for this series of experiments are presented below in the following table 1 for easy and comprehensive understanding. 4.2 experiment for optimal feed rate zone for variable nose radius for the second series of experiments the samples (6 samples x 3 groups) of the ti-6al-4v bar were machined similarly with coated carbide inserts with variable nose radius (nr = 0.4 mm, 0.8 mm and 1.2 mm). but this time the feed rates were varied ranging within f = 0.04–0.28 mm/rev since optimal feed rates were seeking this time. the cutting speed (v = 80 m/min) was kept constant for the cutter with nr = 0.4 mm since in the first stage of experiments it was revealed that v = 80 m/min (within the zone) was the speed providing the best surface roughness (figure 5a) amongst all of the investigated speeds and the constant depth of cut (d = 0.5 mm) as in the previous case. similarly cutting speeds v = 50 m/min and v = 60 m/min were kept constant for the machining operations performed using coated carbide cutters with nose radii nr = 0.8 mm and nr = 1.2 mm respectively. note that depth of cut was kept constant (d = 0.5 mm) for all of these three groups of samples for turning operations. figure 5: the trend of average surface roughness (ra) with cutting speed (v) for constant feed rate (0.1 mm/rev), constant depth of cut (0.5 mm) and tool nose radius (a) 0.4 mm, (b) 0.8 mm and (c) 1.2 mm table 1: operational data for cutting speed optimisation nose radius nr (mm) depth of cut (d) (mm) feed rate (f) (mm/rev) cutting speed (v) variable, (m/min) surface roughness (ra) (µm) comments 0.4 0.5 0.1 variable values in the range v = 25250 m/min as in fig 5 measured values showed in fig. 5 v = 50-160 m/min provide better ra 0.8 0.5 0.1 v = 50 m/min provides better ra 1.2 0.5 0.1 v = 50-250 m/min provide better ra 0 25 50 75 100 125 150 175 200 225 250 0.8 1.1 1.4 1.7 2 2.3 2.6 2.9 cutting speed, v (m/min) s u rf ac e r o u g h n es s, r a (µ m ) speed optimisation f = 0.1mm/rev d = 0.5 mm nr = 0.4 mm insert= carbide 0 50 100 150 200 250 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 cutting speed, v (m/min) s u rf ac e r o u g h n es s, r a (µ m ) speed optimisation f = 0.1 mm/rev d = 0.5 mm nr = 0.8 mm insert = carbide 0 50 100 150 200 250 0.5 1 1.5 2 2.5 3 3.5 4 cutting speed, v (m/min) s u rf ac e r o u g h n es s, r a (µ m ) speed optimisation d = 0.5 mm f = 0.1 mm/rev nr = 1.2 mm insert = carbide a c b an investigation on optimum process parameters in terms of surface roughness for turning titanium alloy ti-6al-4v 142 similarly, the average surface roughness data (ra) for each of the eighteen samples were measured using the taylor hobson surtronic 3+ instrument and the average data were accepted for ra. the graphs in figure 6 shows the relationship of obtained values of surface roughness (ra) for various feed rates (f) for machining ti-6al-4v using the coated carbide cutters with several nose radii (nr = 0.4 mm, 0.8 mm and 1.2 mm). the parameters for this series of experiments are summarised below in the following table 2 for easy and comprehensive understanding. 4.3 experiment for optimal depth of cut with variable nose radius in the third series of experiments, in the similar way as above described, machining of ti-6al-4v samples were carried out using the coated carbide inserts with nose radius nr = 0.4 mm, but this time keeping the cutting speed (v) and feed rate (f) values constant. these constant values were v = 80 m/min and f = 0.1 mm/rev (figures 5a and 6a respectively) since these were established to be the top parameters providing the best surface finish in stage one and stage two of experiments for the cutting tool nose radius nr = 0.4 mm. in this case the depth of cut was varied within possible values ranging d = 0.08-1.6 mm. the surface roughness data were measured, similarly as earlier, for the investigated samples using the taylor hobson surtronic 3+ instrument and the average ra data were calculated for each of the samples. exactly in the same manner another two groups of experiments were carried out, one for the coated carbide inserts with nr = 0.8 mm using v = 50 m/min (optimal as revealed, referring to figure 6) and another for using the coated carbide inserts with nr = 1.2 mm while the cutting speed was v = 60 m/min as optimal referring to figure 5c. all the obtained data from the experiments were carefully tabulated and graphs have been produced for visual and comprehensive understanding. figure 6: the trend of average surface roughness (ra) with feed rate (f) for constant depth of cut (0.5 mm) and (a) nose radius 0.4 mm and cutting speed 80 m/min, , (b) nose radius 0.8 mm and cutting speed 50 m/min, and (c) nose radius 0.1.2 mm and cutting speed 60 m/min table 2: operational data for feed rate optimisation nose radius nr (mm) cutting speed (v) (m/min) depth of cut (d) (mm) feed rate (f) (mm/rev) surface roughness (ra) (µm) comments 0.4 80 0.5 variable, as shown in fig. 6) measured values (fig.6) ra stays same up-to f = 0.1, then increases linearly 0.8 50 ra decreases up-to f = 0.1, then increases linearly 1.2 60 f = 0.1 provides the best ra 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.5 1 1.5 2 2.5 3 3.5 4 4.5 feed rate,f (mm/rev) s u rf a c e r o u g h n e ss , r a ( µ m ) feed optimisation d = 0.5 mm v = 80 m/min nr = 0.4 mm insert = carbide 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 feed rate, f (mm/rev) s u rf ac e r o u g h n es s, r a (µ m ) feed optimisation v = 50 m/min d = 0.5 mm nr = 0.8 mm insert = carbide 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.5 0.8 1.1 1.4 1.7 2 2.3 2.6 2.9 feed rate, f (mm/rev) s u rf ac e r o u g h n es s, r a (µ m ) feed optimisation v = 60 m/min d = 0.5 mm nr = 1.2 mm insert = carbide a c b mazid, hasan and ahsan (2019): international journal of engineering materials and manufacture, 4(4), 137-145 143 figure 7: the trend of average surface roughness (ra) with depth of cut (d) for constant feed rate (0.1 mm/rev) and (a) nose radius 0.4 mm and cutting speed 80 m/min, , (b) nose radius 0.8 mm and cutting speed 50 m/min, and (c) nose radius 0.1.2 mm and cutting speed 60 m/min table 3: operational data for feed rate optimisation nose radius nr (mm) cutting speeds (v) (m/min) feed rates (f) (mm/rev) depth of cut (d) (mm) surface roughness ra (µm) comments 0.4 80 0.1 0.08-1.6 measured parameter (fig. 7) d = 0.1-0.6 mm provide ra = 1.02 m 0.8 50 d = 0.2-1 mm provide ra = 0.8-1.05 m 1.2 60 d = 0.2-1 mm; ra increases linearly from 0.2 to 1.01 m the graphs in figure 7 show the relationship of obtained values of surface roughness (ra) for several depth of cut for machining ti-6al-4v using the coated carbide cutters with several nose radii as nr = 0.4 mm, 0.8 mm, and 1.2 mm. the parameters for this series of experiments are given in table 3 for easy and comprehensive understanding. the cumulative results of real-life experiments for cutting speed optimisation of ti-alloy, using popular coated carbide tools, are discussed in the following section. 5 experimental results and discussions as mentioned earlier that there are so many known and unknown factors influencing cutting processes that it is only possible to achieve the best results if the research is carried out by real-life experiments in metal machining in real environment. because it is only possible to take into account all influencing factors with natural appearances in the case of real-life experiments. in any other way it is certain that many influencing factors on metal machining processes may be disregarded leading to less accurate outcomes. as described in the procedures of experiments in previous section that a series of real-life turning operations have been carried out with variable cutting parameters (v, f, d) using coated carbide inserts (cnmg 120404-mf1, ts2000 (8 cutting edge), cnmg 120408-mf1, ts2000 (8 cutting edge, and cnmg 120412-mf4, ts2000 (8 cutting edge) with nose radii 0.4 mm, 0.8 mm and 1.2 mm respectively on the universal harrison m400 lathe machine. the surface roughness (ra) values of machined samples, prepared with several cutting parameters/regimes, were measured using the precision taylor hobson surtronic 3+ equipment at room temperature. all of the data such as parameters of cutting regimes and the obtained surface roughness values were scrupulously tabulated in a number of tables. the obtained data were plotted in graphical forms as displayed in figures 5-13, each group of three graphs belonging to each of the three nose radii (nr = 0.4 mm, nr = 0.8 mm and nr = 1.2 mm) were investigated. graphs on figures 5, exhibiting the output of experiments with nose radii nr = 0.4 mm, nr = 0.8 mm, and nr = 1.2 mm respectively, 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 depth of cut, d (mm) s u rf a c e r o u g h n e ss , r a ( µ m ) depth of cut optimisation v = 80 m/min f = 0.1 mm/rev nr = 0.4 mm insert = carbide 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0.5 1 1.5 2 2.5 depth of cut, d (mm) s u rf a c e r o u g h n e ss , r a ( µ m ) depth of cut optimisation v = 50 m/min f = 0.1 mm/rev nr = 0.8 mm insert = carbide 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0.8 1 1.2 1.4 1.6 1.8 2 depth of cut, d (mm) s u rf a c e r o u g h n e ss , r a ( µ m ) depth of cut optimisation v = 60 m/min f = 0.1 mm/rev nr = 1.2 mm insert = carbide a c b an investigation on optimum process parameters in terms of surface roughness for turning titanium alloy ti-6al-4v 144 demonstrate the results of surface roughness (ra) obtained in terms of variable cutting speeds (v) while keeping the feed rates (f) and depths (d) of cut constant throughout these experiments. the graphs reveal that the coated carbide inserts with nr = 1.2 mm produces better surface finish in relation to coated carbide inserts with nr = 0.4 mm and nr = 0.8 mm. the insert with nr = 0.4 mm produces the roughest surface finish out of these three options. overall, it has been found that all of these three inserts of coated carbide produce much rougher surface finish for machining ti-6al-4v at lower, somewhere below 75m/min, cutting speeds, as the cutting speeds go lower and lower it produced rougher and rougher surfaces on machined ti-6al-4v alloy samples. there is some unexpected result in the near zone of cutting speed v = 100 m/min, unusually surface roughness has gone higher for the coated carbide inserts with nose radius nr = 0.8 mm and nr = 1.2 mm (figure 6). at this stage of research unlikely any explanation of this phenomenon can be given, but this can be postulated to be related to the reactivity of ti atoms with atoms of materials of the carbide inserts, as was stated by some researchers (machado and walbank, 1990; rahman et al., 2003). the graphs on figure 6 exhibits the results of machining experiments with variable feed rates while depth of cut and the cutting speeds were kept constants. these graphs evidenced that, for all three investigated nose radii of coated carbide inserts, it has produced more and more rough surfaces as the feed rates grow larger and larger. it has also been observed that the coated carbide insert with nr = 0.8 mm exhibited a little worse result than the other two groups of inserts. using insert with nr = 0.8 mm, with the other conditions as used, we can expect the best ra = 1 µm keeping the feed rate is very low as low as f = 0.05 0.1 mm/rev. the surface finish is crucially getting worse after the feed rate f = 0.15 mm/rev for uses of all three categories inserts for machining. the above-mentioned rougher surface finish in ti-6al-4v alloy machining at higher feed rates can be explained by the rise of cutting forces causing increased level of vibrations in mftw dynamic system of the machining processes and higher heat generation in the cutting zone. in relation to depth of cut (d) variation while keeping the cutting speeds and feed rates as constants, the surface roughness obtained in machining ti-6al-4v alloy, as depicted in graphs of figure 7, using coated carbide cutting tools with several investigated nose radii, exhibited similar nature as the depth of cut. that means with the increment of depth of cut in each of the cases, the surface finish quality deteriorated, particularly crucial deterioration was observed beyond the depth of cut d = 1.2 mm. the increased cutting forces with the increase of depth of cut may be responsible for increased vibration level in the mftw dynamic system causing rougher surface finish. 6 conclusions an attempt to the roadmap of the cutting parameters (v, f, d) optimisation for machining ti-alloy ti-6al-4v using coated carbide tools with several cutting nose radii has been made successfully and valuable information on ti-alloy cutting parameters has been revealed. the well-known real-life physical machining method has been re-introduced and used efficiently. the method provides more sensible and realistic outcomes in machining parameter optimisation in comparison to simulation-based optimisation. the results of real-life experiments in real-life situation for machining ti-6al-4v using coated carbide inserts with mentioned geometry and three different nose radii have revealed the following valuable data. regardless of nose radius (nr = 0.4, 0.8, and 1.2 mm) investigated all three groups of coated carbide tools are capable to produce best surface finish, ranging between ra = 0.5 1.0µm, with cutting speed starting at v = 60 m/min and beyond at least up to v = 250 m/min, as has been investigated, while keeping the feed rate and depth of cut as constants as f = 0.1 mm/rev and d = 0.5 mm. the most important phenomenon has been observed that, though maximum cutting speed has been used was v = 250 m/min, but the statistical tendency of the graphs (figures 5–7) do not show any intention of worsening surface finish, it looks it would simply keep growing through a horizontal near-straight line. this phenomenon strongly suggests that high speed machining would be the most favourable way to machine ti-6al-4v using coated carbide tools for better productivity and cost effectiveness. this needs further research and experimentations on cutting tool materials and their physical properties. also, studies on acceptable surface integrity obtained using higher cutting speed are equally essential. as the cutting speed goes lower these investigated tools have produced more and more rough surface finish for the ti-alloy. the graphs in figures 5–7 evidenced that the cutting speeds little below v = 50 m/min the surface roughness values produced have gone as high as ra = 1.4 – 3.5 µm for the coated carbide tools with nose radii nr = 0.4 and 1.2 mm, while the insert with nr = 0.8 mm has produced rough surface no worse than ra = 1.5 µm. therefore, it is not suggested to use cutting speeds below 50 m/min for all types of investigated cutting inserts of coated carbide. as the graphs in figures 8-10 suggest, the best surface finish is possible to achieve using the feed rate f = 0.2 mm/rev or lower; using feed rates beyond f = 0.2 mm/rev surface roughness values go crucially worse, as up to ra = 4.5 µm for two of the cutting inserts (nr = 0.4 and 0.8 mm). similarly, surface roughness is highly affected by the increase of depth of cut beyond d = 1.2 mm. the graphs in figures 11-13 suggest that using the values of depth of cut below d = 1 mm the best surface finish can be expected, as good as ra = 1.0–1.2 µm for all three cutting tools with nr = 0.4 mm, 0.8 mm, and 1.2 mm. hence, for the further research and industry practices it can be suggested that knowing the designated surface roughness given on the detail/part drawing of a component, the process designer have the wider liberty to choose the most suitable machining parameters to achieve the required surface finish for the product. thus, the process design is the valuable mazid, hasan and ahsan (2019): international journal of engineering materials and manufacture, 4(4), 137-145 145 and decisive stage of manufacturing to produce parts within the least possible production cost with the best possible product quality. the quality of post-machined parts is assessed not only by the surface roughness but also by the surface integrity and geometric accuracy of the machined parts. as well, the scientific research on machinability of materials can only be sensible/profitable if the samples for experimentation are produced using the optimal cutting regimes. more research is essential for sub-layer residual stresses analysis and the microhardness of the machined sub-layer portions of the machined parts. a compromised set of machining conditions can only be drawn analysing the data obtained by the cutting parameters optimisation, sub-layer residual stress level and microhardness analytical data. while this compromised set of machining conditions is supposed to yield fruitful solutions for ti-alloys machining. references ancio, f., gamez, a.z., marcos, m. (2015). factors influencing the generation of machined surface. application to turned pieces. journal of materials processing technology, 215, 50 61. aspinwall, d.k., dewes, r.c., mantle, a.l. (2005). the machining of γ-tial intermetallic alloy. cirp annals: manufacturing technology, 54 (1), 99-104. astakhov, p.v. (1999). metal cutting mechanics. crc press llc. ataollah j., ulfried r., wilfried e. (2008). the effect of machining on surface integrity and fatigue life. international journal of fatigue, 30, 2050 2055. che-haron, h., jawaid, a. (2005). the effect of machining on surface integrity of titanium alloy ti-6%al-4%v. journal of materials processing technology, 166, 188 192. davim, j.p. (editor) (2010). surface integrity in machining. springer, london. ezugwu, e.o., bonney, j., yamane, y. (2003). an overview of machinability of aeroengine alloys. journal of materials processing technology, 134, 233 253. ezugwu, e.o., wang, z.m. (1997). titanium alloys and their machinability – a review. journal of materials processing technology, 68, 262-274. gatto, a., iuliano, l. (1997). advanced coated ceramic tools for machining superalloys. international journal of machine tools and manufacture, vl. 37 (5), 591605. hua, j., shivpuri, r. (2004). prediction of chip morphology and segmentation during the machining of titanium alloys. journal of materials processing technology, 150, 124 -133. lei, s., liu, w. (2002). high-speed machining of titanium alloys using driven rotary tool. international journal of machine tools and manufacture, 42, 653 661. machado, r., walbank, j. (1990). machining of titanium and its alloys – a review. part b: journal of engineering manufacture, 204 (b1), 53 60. nabhani, f. (2001). machining of aerospace titanium alloys. robotics and computer integrated manufacturing, vol. 17, pp. 99 106. ogedengbe, t. s. (2019). sustainable machining processes through optimisation of process parameters. international journal of engineering materials and manufacture, 4(1), 22 26. pervaiz, s., rashid, a., deiab, i., nicolescu, m. (2014). influence of tool materials on machinability of titaniumand nickel-based alloys: a review. materials and manufacturing processes, 29, 219 252. kuttolamadom, m., jones, j., mears, l., oehsen, j. v., kurfess, t., ziegart, j. (2017). high performance computing simulation to identify process parameter designs for profitable titanium machining. journal of manufacturing systems, 43, 235 – 247. rahman, m., wong, y.s., zareena, a.r. (2003). machinability of titanium alloys. jsme international journal. series c, 46 (1), 107-115. ribeiro, m.v., moreira, m.r.v., ferreira, j.r. (2003). optimisation of titanium alloy machining. journal of materials processing technology, 458 463. schneider, f., bischof, r., kirsch, b., kuhn, c., muller, r., aurich, j. c. (2016). investigation of chip formation and surface integrity when micro-cutting cp-titanium with ultra-fine grain cemented carbide. procedia cirp, 45, 115–118. ulutan, d., ozel, t. (2011). machining induced surface integrity in titanium and nickel alloys: a review. international journal of machine tools and manufacture, 51, 250-280. veiga, c., davim j.p., loureiro, a.j.r. (2012). properties and applications of titanium alloys: a brief review. reviews on advanced materials science, 32, 133 148. villeta m., rubio e.m., saenz de pipaon j.m., sebastian m.a. (2011). surface finish optimization of magnesium pieces obtained by dry turning based on taguchi techniques and statistical tests. materials and manufacturing processes, 26, 1503 1510. yang, x., liu, r. (2007). machining titanium and its alloys. machining science and technology: an international journal, 3 (1), 107-139. international journal of engineering materials and manufacture (2019) 4(3) 107-115 https://doi.org/10.26776/ijemm.04.03.2019.03 solar electrification in desert: a case of kuwait abdullah al mutairi, mohammad yeakub ali and mohd radzi che daud received: 18 june 2019 accepted: 11 september 2019 published: 27 september 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract solar energy creates a new lifestyle for mankind, and takes society and human into an era of energy conservation to reduce pollution. it is radiant light and heat from the sun harnessed using a range of ever-evolving technologies such as photovoltaic panel. in this research it is aimed to design and implement pv solar energy home system for electrification in the kuwaiti dessert during eco-tourism in winter. eco-tourism is a cultural and unavoidable event in arab countries with no exception of kuwait. eco-tourism is done in remote dessert where urban electricity connections are not possible. as people accustomed in using electrical appliances such as television, room heater, water heater, water pump, they cannot live in the dessert without these amenities. as the weather of kuwait is sunny and hot during days and cool at night, solar panel based off-grid power cell can be an alternative for electrification of dessert home. this research addressed several critical issues which are appropriate design of pv solar system, estimation of power generation and implementation as solar home system. keywords: eco-tourism, renewable energy, solar energy, photovoltaic cell, off-grid, shagaya, kuwait 1 introduction eco-tourism during winter in kuwait is a cultural and unavoidable event where urban electricity connections are not possible (mahgoub, 2007). as people accustomed in using electrical appliances such as television, room heater, water heater, water pump, they cannot live in the dessert without these amenities. as the weather of kuwait is sunny and hot during days and cool at night, solar panel based off-grid power cell can be an alternative. in this case, appropriate design, implementation of solar panel and estimated power generation are critical issues. solar energy, a kind of renewable energy, has become an important subject of energy research. it is rich in resources, free and no pollution to the environment. solar energy is radiant light and heat from the sun harnessed using a range of ever-evolving technologies such as photovoltaic panel. solar energy creates a new lifestyle for humankind, and takes society and human into an era of energy conservation to reduce pollution (alhouli, 2017). eco-tourism during winter in kuwait is a cultural and unavoidable event. under this programme people spent time in the dessert especially at night for about 2-3 months. as people accustomed in using electrical appliances such as television, room heater, water heater, water pump, they cannot live in the dessert without these amenities. as there is no electricity supply from national power grid, people use oil fired international combustion engine, power bank charged by direct electricity in urban areas. however, as the weather of kuwait is sunny and hot during days and cool at night, solar panel based off-grid power cell can be an alternative. in this case appropriate design, implementation of solar panel and estimated power generation are critical issues. the primary concern of this research is to design an off-grid solar photovoltaic electrification system for kuwait eco-tourism. firstly, the feasibility report from this research will have a huge impact for the advancement of solar photovoltaic electrification in kuwait. plus, the successful designed photovoltaic system will significantly benefit the homes in the dessert of kuwait mainly during winter eco-tourism season. finally, the proposed guidelines and implementation strategy from this research will be useful in producing solar power system for individual house with high efficiency in larger scale for kuwait. the main scope of this project is to study the weather and identification of a. a. mutairi1, m. y. ali2 and m. r. c. daud1 1department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia 2mechanical engineering programme area, faculty of engineering universiti teknologi brunei, jalan tungku link gadong be1410, brunei darussalam e-mail: yeakub.ali@utb.edu.bn reference: mutairi, a. a., ali, m. y. and daud, m. r. c. (2019). solar electrification in dessert: a case of kuwait. international journal of engineering materials and manufacture, 4(3), 107-115. solar electrification for dessert: a case of kuwait solar panel parameters to generate solar home system (10-130 watt peaks) for lighting, television, battery charging, at individual home. the details of the scope include the following: 1. small houses in desert of kuwait as the area for the study and investigation for the implementation of the solar photovoltaic system. 2. the design and selection of an off-grid photovoltaic system to generate the required amount of power needed. 3. assessment and safety and reliability issues in power generation and application for the individual home in the kuwait dessert. 2 literature review in this section, the literatures related to renewable energy especially in the arabian gulf countries are discussed. it includes energy crisis and planning, harvesting solar energy and distribution of solar energy in remote and rural areas. 2.1 renewable energy planning in the gulf countries the middle east and north africa (mena) has, for most of its modern-day history, been known for its energy wealth. home to more than half of the world’s proven crude oil and more than a third of its natural gas reserves, the dominant story of the mena region has for the past fifty years been that of a global energy supplier. consequently, the mena region’s domestic energy market has been seen for decades as marginal in the global picture, supplied with amply available, regionally produced, low-cost fossil fuels. with some of the world’s lowest domestic prices for both primary energy and electricity, the mena region has appeared to lack the kind of economic incentive needed for alternative energy sources, such as renewable energy and nuclear power, to enter its markets (irena, 2013). panarab renewable energy strategy goals are the followings (irena, 2014): 1. utilising the abundance of renewable energy resources; 2. enhancing future energy security through diversification of energy resources; 3. meeting the requirements of national and regional development; 4. keeping indigenous oil and natural gas as strategic reserves for as long as possible; and 5. contributing to resolving environmental issues associated with oil and gas exploration, transportation and use. overall, the arab region enjoys a rich endowment of renewable energy resources, particularly solar and wind energies. in fact, the region’s conditions are very much favourable to produce renewable power system economically. this is more feasible and more attractive than in most other regions of the world (irena, 2014). among all the countries of the world, kuwait can be said to have one of the greatest demand for electrical power. its per capita rate of energy consumption is quite high owing to four major factors. first and foremost, kuwait has a combination of weather conditions that are very extreme. second, the government of kuwait offers its citizens high subsidies in so far as electricity is concerned. third, the general population of kuwait has been constantly growing over the years and hence, the great demand. last, the plants available in kuwait for desalination of water make use of a lot of energy and as such, their energy-intensive status can only allow them to function properly if there is a lot of electricity (alhouli, 2017). the investment and project on solar energy in gcc are shown in figure 1 and figure 2 respectively. kuwait witnessed an increase in the demand for electrical power up to two times its normal demand between the years 2003 and 2013. to cater for this demand kuwait established an energy park of 70 megawatts to be completed in 2016. in the second and third phases, the country intended to establish projects to generate 930 megawatts and 1000 megawatts of electrical energy, respectively. plans are underway to ensure that solar projects are completed. figure 1: investment in gcc renewable energy (masud et al., 2018) 108 almutairi, ali and daud (2019): international journal of engineering materials and manufacture, 4(3), 107-115 figure 2: current and future solar project in gcc (masud et al., 2018) figure 3: solar thermal electricity generation 2.2 harvesting solar energy the abundant of radiation in kuwait country is the main reason why the harvesting of solar energy is considered as very promising. however, the implementation of solar photovoltaic system in kuwait is different depending on the region it is installed. rather than the knowledge of basic solar thermal electricity is needed, the differences of radiation in remote, urban and dessert area in kuwait is also critical and is discussed in the next subtopic. 2.2.1 solar thermal electricity a solar thermal power system collects and concentrates sun energy to generate high temperature heat that is necessary to create electrical power. the system contains two main devices: reflectors and receivers. a reflector is basically utilized in capturing and focusing the sunlight into a given receiver. there is also a heat transfer fluid which is put under heat and then distributed in the receiver for the purpose of producing steam. the steam is later transformed into mechanical energy with the aid of turbines that power generators to create electricity as it is shown in figure 3. it is important to note that there exists a tracking system that basically focuses the sun energy onto the receiver during the day, keeping in mind the changes in the position of the sun. a storage system known as thermal energy can also be utilized to store excess energy during hot days so as to be used during the night or cloudy days (alhouli, 2017). 2.2.2 solar energy electricity in remote areas access to energy offers great benefits to development through the provision of reliable and efficient lighting, heating, cooking, mechanical power, transport and telecommunication services. additionally, access to power has proven economic welfare, as productivity increases with businesses, substituting manual work by automated processes and finally leading to a positive virtuous growth cycle (halabi, al-qattan and al-qataibi, 2015). one of these off-grid technologies is photovoltaic (pv) systems, which have been installed in many developing countries (dcs) aiming to provide people with electricity who would otherwise have to wait for years to get connected to the national power. it is well-known that solar pv produces electricity from sunlight through an electronic mechanism in a specific type of semiconductor material, commonly silicon. the sunrays induce free electrons from these materials to travel in an electrical circuit in order to power electrical systems or conveying the 109 solar electrification for dessert: a case of kuwait electricity to the grid. the pv panels can be installed on the ground, on rooftops or standing structures. the solar pv can contribute immensely to the socio-economic development of the gcc region. according to an international renewable energy agency (irena) report, the gcc countries could gain numerous benefits from re implementation. 2.2.3 photovoltaic electrification in urban area of kuwait it is a well-known fact that the gcc countries depend on oil as the major energy source, especially for power generation, which is non-renewable. the environmental impact from non-renewable energy (re) sources such as gas and oil are enormous and can cause a major challenge for these countries. for example, an increase in high-carbon dioxide (co2) emissions that pollute the atmosphere and subsequently affect global warming (mas’ud et al., 2018). kuwait’s annual solar radiation is predicted to be between 2100 and 2200 kw/m2. the average daily sunshine hours/year for kuwait range from 7 to 12. according to 2015 kuwait energy policy, laws and regulations, the maximum solar radiation and the peak electricity demand in the country occurs at the same time of the year, making the solar pv the most useful re source for the country. the primary energy source of kuwait is 100% from fossil fuel with oil supplying 52.8% and natural gas 47.2%. the energy consumption in kuwait varies according to the following vectors: 33% industrial, 19% transport, 23% residential and 25% non-energy uses and other consumption (alazemi, 2017). kuwait energy resources are managed by the kuwait petroleum corporation and its subsidiaries are responsible for oil and gas production, exporting, importing and distribution. the acceptance of the kyoto protocol by kuwait in march 2005 allowed the country to rethink a plan for re policy in agreement with the climate change mitigation objectives. since then, there are research and development (r&d) initiatives by the government aimed at promoting the application of solar pv and solar thermal systems in both public and private institutions. an environmental and social impact assessment carried out in 2012 to examine the solar pv in the north africa and the middle east showed that solar pv could be cost-competitive with oil-fired power generation (al-enezi et al., 2011; bou_rabee, 2015). 2.2.4 photovoltaic electrification in dessert area of kuwait geography plays an integral role in determining what forms of renewable energy will be the most useful. hydroelectric energy is the primary source of electricity for the countries of canada and brazil. denmark, germany, and the united states are increasing the number of wind turbines and offshore wind farms to meet the increasing energy demands. other european nations are moving towards a renewable energy stance with increased photovoltaic and wind energy projects that will make up a large portion of their future infrastructure. austin et al, (2005) concluded that australia, japan, and third world african five countries use solar energy in isolated regions and cities to harness the sun’s energy. bollinger (2007) discussed that in the united states, the use of wind energy centres around the west coast and small to large wind farms scattered across the nation. the southwest united states benefits from abundant sunlight and moderate weather during the winter. the midwest is not known for employing renewable energy due to the lower cost of producing power from coal plants. also, the conditions of the land makes implementing hydroelectric dams difficult, the lack of mountain ranges and water sources reduce the average speed of the wind, and the high percentage of clouds in the winter hampers the use of solar panels (feron, 2016). the implementation of solar energy has come from individual home owners that accept the cost involved and the number of consumers will continue to increase with a reduction in equipment cost and utility rate hikes. photovoltaic energy has only been around a few decades, and came about through advancements in the space program. the performances of the individual cells of a solar panel are steadily improving with newer advancements with semiconductor material (ramadhan and naseeb, 2011; ramadhan et al., 2013). 2.3 solar photovoltaic cell a photovoltaic solar cell is generally a device used in the direct conversion of light energy into electricity with the aid of semi-conductors of electricity that unveil a photoelectric impact. a characteristic system of a photovoltaic utilizes solar panels, each made up of various solar cells that generate electricity. the installations of photovoltaic cells can be mounted on the rooftop, ground or the wall of buildings. the mounting can be done through fixation or simply through the employment of a solar tracker that follows the direction of the sun. no form of pollution is produced into the environment with the use of solar photovoltaic cells as there are no moving parts. two most common type of pv cells are crystalline silicon (c-si) pv cells and amorphous silicon (a-si) pv cells. the elements and components of pv cells are briefly discussed here (alhouli, 2017; nuralam, et al., 2015). a sample of pv solar system is shown in figure 4. 2.3.1 the inverter the electric current generated from the solar energy is basically direct current. hence, for it to be used domestically in homes, it has to be converted into alternating current using an inverter. the inverter uses a series of solid-state switches to generate alternating current. a special type of inverter known as a grid-tie inverter is required if the electricity generated is to be utilized by the grid. its main purpose is to match the electricity phase generated to the grid phase in order to avoid possible mismatches of the phases and hence, cancellation. in addition, the grid-tie inverter works as a safety measure. for instance, in the event there is a power blackout, it immediately switches off the supply line to the solar panel so as to avoid causing any harm to persons working on the power lines. 110 almutairi, ali and daud (2019): international journal of engineering materials and manufacture, 4(3), 107-115 figure 4: pv solar panel system to produce electricity (rimstar, 2019) 2.3.2 the battery some of the photovoltaic solar cells have an installed battery that is used to store the excess electric energy generated from the sun. this energy is put into use when the solar panels do not provide sufficient energy; for instance, during rainy or dark days. hence, the battery is generally utilized off-grid. the connection of the battery system can be either serial or parallel. the flooded battery, which is a lead-acid battery system, is the most preferred in photovoltaic cells as they neither require distilled water nor electrolytes. 2.3.3 the distributor the distributor is used to distribute the ac power that has been generated by the inverter into the electric grid. at times, it can be used to distribute the electric energy generated not only to the grid but also the home that has been fitted with the solar system. 2.3.4 pv generator pv generator is used to convert the energy obtained from the sun into electrical energy. its efficiency is currently estimated to be 15 percent. the device requires optimum conditions and environment so as to work efficiently and effectively. 2.3.5 charge regulator the charge regulator offers protection to the battery system by monitoring the charging process to either slow down or halt the process to avoid overcharging. it increases the life of the batteries to effectively store the energy generated. however, if the solar panel does not use batteries, then there is no need for a battery regulator. the charge regulators are of different types and sizes depending on the photovoltaic system in use. it is important to note that the stability of the regulator should be reached at the maximum current. since, in most countries of the world solar pv is the most commonly used, this paper will focus on the solar pv. 3 research methodology the research initiative starts with relevant technical and government enforcement literature review in the field. based on state of the arts literature review, problem statement, research objective, and scope are established. research methodology is developed to carry out the research. then experimental design and setup were prepared to conduct experiment and measurement of data. this research targeted to propose high efficiency off-grid photovoltaic system for kuwait eco-tourism. the research started with the collection of weather data which includes the radiation, temperature and wind speed for a monthly basis. next, the information regarding the electrical usage of kuwait desert houses is needed. by having these weather data and electrical usage calculation, the simulation was done using pvsyst software. this software was used to design and analyse the photovoltaic system. the results of these analyses were the predicted performance of the annual solar energy production. finally, the analysis will depict the suitability of the photovoltaic design for the houses in the desert. 4 weather data and information collection the first stage in this research was to select the available sites in kuwait that is located in the desert which is suitable for eco-tourism activity. kuwait consist of six governorates; jahra, al asimah, farwaniya, hawalli, mubarak al-kabeer and ahmadi. among these governorates, jahra which is at the western part of kuwait have one of the highest amount of solar radiation. an area called shagaya which located at 29.2° latitude (n) and 47.1° longitude € as shown in figure 5 is selected as the location of interest due to the availability of the required data. in photovoltaic research, the most important data that is needed is the average monthly solar irradiation of the location. the irradiation data was collected from kuwait institute of scientific research (kisr). other than irradiation data, the average duration 111 solar electrification for dessert: a case of kuwait of sunshine also is considered as important. this is important due to the photovoltaic performance is directly affected by the number of hours of sunshine. the data for the sunshine hours in shagaya, as shown in figure 5, is shown in table 1. by having this information, it is still not sufficient in designing an off-grid solar photovoltaic system. thus, the selection of photovoltaic type is discussed in the next subsection. 4.1 photovoltaic type selection there are three different types of solar panels that is available in the market; monocrystalline silicon, thin film silicon and polycrystalline silicon solar panel. thin film silicon is considered as very versatile due to its flexibility. however, this type of solar panel has large drawbacks which its efficiency percentage decreases over time, not durable and have toxicity concern. therefore, only monocrystalline and polycrystalline silicon solar panels as shown in figure 6 is available in the market of kuwait. the comparison between both of the solar panels showed that monocrystalline is the best choice as it has higher quality number. furthermore, this type of solar panel is very durable, have low maintenance, high heat resistance, high efficiency and environmentally friendly. 4.2 the simulation of the designed off-grid solar photovoltaic system the simulation of the electricity generated by the designed photovoltaic system was done using pvsyst software. this software capable to simulate grid-connected, stand-alone, pumping and dc-grid photovoltaic system. in this research, the selected mode is the stand-alone photovoltaic system. this software capable of performing a thorough system design using detailed hourly simulations under the ‘project design’ option as shown in figure 7. different simulation runs can be made with combinations of plane orientations, specific system components, number of pv array, inverter model, and battery pack. detailed parameters can also be specified and analysed such as thermal behaviours, wiring, module quality, incidence angle losses, horizon, and partial shading. table 1: monthly sunshine hours for shagaya, kuwait month sunlight (hours) january 8 february 8.55 march 9 april 8 may 10 june 10 july 10 august 11 september 10 october 10 november 8 december 7 yearly average 9.1 figure 5: shagaya on kuwait solar map 112 almutairi, ali and daud (2019): international journal of engineering materials and manufacture, 4(3), 107-115 figure 6: monocrysttaline and polycrysttaline solar panel figure 7: pvsyst v6.40 software interface the reports generated by the simulations can be displayed in terms of monthly, daily or hourly values. the most important ‘loss diagram’ is particularly useful in identifying the weaknesses of the system design. other than that, the detailed economic evaluations can be performed using real component prices, additional costs and investment conditions. furthermore, the performance ratio graph, daily input/output diagram, and daily array output diagram is also available. in terms of useful tables, pvsyst software provides balances and main results, incident energy tables, as well as losses in pv system. by incorporating all of these figures and tables, a comprehensive report of the designed pv system can be made without hassles. 4.3 electrical usage calculation in order to conduct a simulation of an off-grid solar photovoltaic system, an example of calculation of electrical usage of typical house in kuwait is needed. table 2 shows an electrical usage of a typical house in kuwait. from table 4.1, it can be seen that the power consumption per month is 14,261.46 kwh. thus, using eqn 1 the daily consumption load of the house is 475.38 kwh/day. 𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷 𝐷𝐷𝑙𝑙𝐷𝐷𝑙𝑙 = 𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚ℎ𝑙𝑙𝑙𝑙 𝑝𝑝𝑚𝑚𝑝𝑝𝑝𝑝𝑝𝑝 𝑐𝑐𝑚𝑚𝑚𝑚𝑐𝑐𝑐𝑐𝑚𝑚𝑝𝑝𝑚𝑚𝑐𝑐𝑚𝑚𝑚𝑚 30 𝑑𝑑𝑑𝑑𝑙𝑙𝑐𝑐 (1) as the proposed monocrystalline pv system requires batteries to store the collected electricity, a 20% factor of inefficiency is needed to compensate the power loss of the battery charge/discharge. thus, eqn 2 shows the daily power consumption needed by the house after considering the battery inefficiency. the calculated daily power consumption needed is 570.46 kwh/day. 𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷 𝑝𝑝𝑙𝑙𝑝𝑝𝑝𝑝𝑝𝑝 𝑐𝑐𝑙𝑙𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑝𝑝𝑐𝑐𝐷𝐷𝑙𝑙𝑐𝑐 = 𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷 𝐷𝐷𝑙𝑙𝐷𝐷𝑙𝑙 × 1.2 (2) 113 solar electrification for dessert: a case of kuwait table 2: electrical usage in kuwait house application qty power (kw) total power (kw) duration of use (h/day) power consumption (kwh/month) light (40 w) 13 0.04 0.52 6 93.60 light (30 w) 9 0.03 0.27 6 48.60 tv 5 0.20 1.00 2 60.00 washing machine 3 0.42 1.26 1 37.80 microwave 3 1.30 3.90 1 117.00 outdoor lights 13 0.06 0.78 6 140.40 neon light 12 0.02 0.24 6 43.20 indoor light 62 0.06 3.72 2 223.20 wansa air condition unit (small) 2 3.35 6.70 2 402.00 wansa air condition unit (large) 1 13.00 13.00 2 780.00 central boiler 1 9.00 9.00 3 810.00 water pump 1 0.60 0.60 1 18.00 a/c central unit 4 tons 4 14.10 56.40 4 6,768.00 a/c central unit 5 tons 2 17.60 35.20 4 4,224.00 refrigerator 4 1.41 5.64 3 507.60 total 61.19 138.23 14,261.46 next, the pv system voltage is rated at 12 volts, hence eqn 3 was used to calculate the total current per hour needed in a day. the calculated value was 47538.2 a-h/day. 𝑇𝑇𝑙𝑙𝑐𝑐𝐷𝐷𝐷𝐷 𝑐𝑐𝑐𝑐𝑝𝑝𝑝𝑝𝑝𝑝𝑐𝑐𝑐𝑐 𝑝𝑝𝑝𝑝𝑝𝑝 ℎ𝑙𝑙𝑐𝑐𝑝𝑝 = 𝐷𝐷𝑑𝑑𝑐𝑐𝑙𝑙𝑙𝑙 𝑝𝑝𝑚𝑚𝑝𝑝𝑝𝑝𝑝𝑝 𝑐𝑐𝑚𝑚𝑚𝑚𝑐𝑐𝑐𝑐𝑚𝑚𝑝𝑝𝑚𝑚𝑐𝑐𝑚𝑚𝑚𝑚 12 𝑉𝑉 (3) based on table 1, it can be noted that the sunshine in the targeted area, shagaya is approximately 9.1 hours. this also means that the effective time of charging the pv is 9.1 hours per month throughout the year. thus, the calculation of the power produced by the pv cells per hour is shown in eqn 4. 𝑃𝑃𝑙𝑙𝑝𝑝𝑝𝑝𝑝𝑝 𝑝𝑝𝑝𝑝𝑙𝑙𝑙𝑙𝑐𝑐𝑐𝑐𝑝𝑝𝑙𝑙 𝑏𝑏𝐷𝐷 𝑃𝑃𝑃𝑃 𝑐𝑐𝑝𝑝𝐷𝐷𝐷𝐷𝑐𝑐 = 𝐷𝐷𝑑𝑑𝑐𝑐𝑙𝑙𝑙𝑙 𝑝𝑝𝑚𝑚𝑝𝑝𝑝𝑝𝑝𝑝 𝑐𝑐𝑚𝑚𝑚𝑚𝑐𝑐𝑐𝑐𝑚𝑚𝑝𝑝𝑚𝑚𝑐𝑐𝑚𝑚𝑚𝑚 𝐴𝐴𝐴𝐴𝑝𝑝𝑝𝑝𝑑𝑑𝐴𝐴𝑝𝑝 𝑐𝑐𝑐𝑐𝑚𝑚𝑙𝑙𝑐𝑐𝐴𝐴ℎ𝑚𝑚 ℎ𝑚𝑚𝑐𝑐𝑝𝑝 (4) by using eqn 4, it is found that the pv system arrays should produce 63.38 kw of electrical power per hour. however, a 10% power loss factor have to be added in order to compensate the inefficiency of the photovoltaic system. the calculation is shown in eqn 5. 𝐻𝐻𝑙𝑙𝑐𝑐𝑝𝑝𝐷𝐷𝐷𝐷 𝑝𝑝𝑝𝑝𝐷𝐷𝑝𝑝 𝑝𝑝𝑙𝑙𝑝𝑝𝑝𝑝𝑝𝑝 𝑐𝑐𝑝𝑝𝑝𝑝𝑙𝑙𝑝𝑝𝑙𝑙 = 𝑃𝑃𝑙𝑙𝑝𝑝𝑝𝑝𝑝𝑝 𝑝𝑝𝑝𝑝𝑙𝑙𝑙𝑙𝑐𝑐𝑐𝑐𝑝𝑝𝑙𝑙 𝑏𝑏𝐷𝐷 𝑃𝑃𝑃𝑃 𝑐𝑐𝑝𝑝𝐷𝐷𝐷𝐷𝑐𝑐 × 1.1 (5) using eqn 5, the hourly power produced by the pv arrays is 69.723 kw. furthermore, based on the selection of monocrystalline pv type, it is known that a cell of monocrystalline pv type produces an average of 300 w of power. thus, to calculate the amount of pv cells needed, eqn 6 is used. 𝑁𝑁𝑐𝑐𝑐𝑐𝑏𝑏𝑝𝑝𝑝𝑝 𝑙𝑙𝑜𝑜 𝑃𝑃𝑃𝑃 𝑐𝑐𝑝𝑝𝐷𝐷𝐷𝐷 𝑐𝑐𝑝𝑝𝑝𝑝𝑙𝑙𝑝𝑝𝑙𝑙 = 𝐻𝐻𝑚𝑚𝑐𝑐𝑝𝑝𝑙𝑙𝑙𝑙 𝑝𝑝𝑝𝑝𝑑𝑑𝑝𝑝 𝑝𝑝𝑚𝑚𝑝𝑝𝑝𝑝𝑝𝑝 𝑚𝑚𝑝𝑝𝑝𝑝𝑑𝑑𝑝𝑝𝑑𝑑 𝐴𝐴𝐴𝐴𝑝𝑝𝑝𝑝𝑑𝑑𝐴𝐴𝑝𝑝 𝑝𝑝𝑝𝑝𝑚𝑚𝑑𝑑𝑐𝑐𝑐𝑐𝑚𝑚𝑐𝑐𝑚𝑚𝑚𝑚 𝑚𝑚𝑜𝑜 𝑝𝑝𝑚𝑚𝑝𝑝𝑝𝑝𝑝𝑝 𝑐𝑐𝑚𝑚 𝑚𝑚𝑚𝑚𝑝𝑝 𝑃𝑃𝑉𝑉 𝑐𝑐𝑝𝑝𝑙𝑙𝑙𝑙 (6) finally, the calculated number of pv cells required for a house in kuwait is approximately 233 cells with the total cost is $6,764.50 usd. this is an example of calculation for the common houses in kuwait. the suggested electrical usage is discussed in the next subsection. 5 suggested electrical usage for eco-tourism by comparing the electrical usage in a regular residence, the usage for eco-tourism is considerably lesser due to less electrical applications. therefore, a new electrical usage calculation is needed. the suggested electrical usage to be used in eco-tourism houses is shown in table 3. it can be seen that the power consumption for the suggested electrical usage for eco-tourism houses per month is 274.32 kwh. thus, using eqn 1, the daily consumption load of the house is 9.144 kwh/day. adding a 20% factor of inefficiency due to monocrystalline photovoltaic type as stated in eqn 2 the load for daily usage is 10.9728 kwh/day. next, the house for eco-tourism also uses the same system voltage at 12 volts, hence using eqn 3 the total current per hour needed in a day is 0.9144 a-h/day. 114 almutairi, ali and daud (2019): international journal of engineering materials and manufacture, 4(3), 107-115 table 3: suggested electrical usage in eco-tourism houses application qty power (w) total power (w) duration of use (h/day) power consumption (wh/day) power consumption (kwh/month) lamps 6 10 60 5 300 9.00 television 1 100 100 5 500 15.00 domestic appliances 1 500 500 4 2000 60.00 refrigerator 1 34 34 24 800 24.00 ventilation 1 100 100 24 2400 72.00 air conditioning 1 1000 1000 3 3000 90.00 stand-by consumers 1 6 6 24 144 4.32 total 12 1,750 1,800 9,143 274.32 4 conclusions and recommendations a solar photovoltaic system has been designed for dessert eco-tourism in kuwait. some insight on the kuwait capabilities and future hopes for the design implementation is also shared for the recommendation purposes. 1. it was found that the solar renewable energy is feasible to be supplied towards the houses in the dessert for eco-tourism by stand-alone photovoltaic system. the suggested site for the photovoltaic research is shagaya which is located at the western part of kuwait. 2. a pv system was designed using a 60 cells monocrystalline type of pv module, 24 units of battery, and an mppt converter controller. this design pv system is suitable to be used as the stand-alone system for the ecotourism houses. references absi halabi, m., al-qattan, a., & al-otaibi, a. (2015). application of solar energy in the oil industry current status and future prospects. renewable and sustainable energy reviews, 43, 296–314. alazemi, f. k. (2017). photovoltaic energy in kuwait : a financial and environmental analysis. (unpublished doctoral dissertation). university of bath, united kingdom. al-enezi, f. q., sykulski, j. k., & ahmed, n. a. (2011). visibility and potential of solar energy on horizontal surface at kuwait area. energy procedia, 12, 862–872. alhouli, o. j. m. a. (2014) using solar energy in kuwait to generate electricity instead of natural gas. (unpublished master’s thesis). kansas state university, united state. alrashidi, a. (2017) investigating the feasibility of solar photovoltaic systems in kuwait. (unpublished doctoral dissertation). loughborough university, united kingdom. bou-rabee, m. a., sulaiman, s. a., choe, g., han, d., saeed, t., & marafie, s. (2015). characteristics of solar energy radiation on typical summer and winter days in kuwait, 12 (december), 2944–2953. bryden, j., riahi, l., & zissler, r. (2013). mena renewables status report, 21. el-katiri, l. (2014). a roadmap for renewable energy in the middle east and north africa. oxford institute for energy studies. feron, s. (2016). sustainability of off-grid photovoltaic systems for rural electrification in developing countries: a review. sustainability (switzerland), 8 (12), 1–26. irena. (2016). renewable energy in the arab region: overview of developments, (march). retrieved from www.rcreee.org karim, r., & islam, m. r. (2016). a comparative study on installation of solar pv system at garments roof top proceedings of 11th global engineering , science and technology conference a comparative study on installation of solar pv system at garments roof top, (february). mahgoub, y. (2014). towards sustainable desert eco-tourism in kuwait : learning from the regional experience (january). mas’ud, a. a., wirba, a. v., alshammari, s. j., muhammad-sukki, f., abdullahi, m. m., albarracín, r., & hoq, m. z. (2018). solar energy potentials and benefits in the gulf cooperation council countries: a review of substantial issues. energies, 11(2), 1–20. mezher, t., dawelbait, g., & abbas, z. (2011). renewable energy policies implementation drivers and barriers for abu dhabi. proceedings of the world renewable energy congress – sweden, 8–13 may, 2011, linköping, sweden, 57, 2501–2508. mohammadi, y., & ahmadi, k. (2019). frequency domain analysis of regenerative chatter in machine tools with linear time periodic dynamics. mechanical systems and signal processing, 120, 378–391. ramadhan, m., hussain, a., & behbehani, d. (2012). the prospect of solar energy in the development of power stations in the state of kuwait. journal of renewable energy, 2013(ii), 1–6. ramadhan, m., & naseeb, a. (2011). the cost benefit analysis of implementing photovoltaic solar system in the state of kuwait. renewable energy, 36(4), 1272–1276. rimstar (2019). off-grid solar panel system, rimstar.org (11 august 2019) https://rimstar.org/renewnrg/off_grid_solar_power_systems.htm 115 https://rimstar.org/renewnrg/off_grid_solar_power_systems.htm abstract 1 introduction 2 literature review 2.1 renewable energy planning in the gulf countries 2.2 harvesting solar energy 2.2.1 solar thermal electricity 2.2.2 solar energy electricity in remote areas 2.2.3 photovoltaic electrification in urban area of kuwait 2.2.4 photovoltaic electrification in dessert area of kuwait 2.3 solar photovoltaic cell 2.3.1 the inverter 2.3.2 the battery 2.3.3 the distributor 2.3.4 pv generator 2.3.5 charge regulator 4.1 photovoltaic type selection 4.2 the simulation of the designed off-grid solar photovoltaic system 5 suggested electrical usage for eco-tourism 4 conclusions and recommendations references international journal of engineering materials and manufacture (2022) 7(1) 35-46 https://doi.org/10.26776/ijemm.07.01.2022.04 md. jahangir alam, mohammad washim dewan , sojib kummer paul and khurshida sharmin department of mechanical engineering, dhaka university of engineering & technology, gazipur, bangladesh. e-mail: washim0179@duet.ac.bd reference: alam et al. (2022). investigation of jute and glass fibre reinforced hybrid composites manufactured through compression molding process. international journal of engineering materials and manufacture, 7(1), 35-46. investigation of jute and glass fibre reinforced hybrid composites manufactured through compression molding process md. jahangir alam, mohammad washim dewan, sojib kummer paul and khurshida sharmin received: 06 september 2021 accepted: 05 december 2021 published: 01 january 2022 publisher: deer hill publications © 2022 the author(s) creative commons: cc by 4.0 abstract expensive and non-biodegradable synthetic fibres are commonly utilized as reinforcement in composites for better mechanical properties. the eco-friendly and low-cost properties of natural fibres are promising alternative reinforcement for composites. in this study epoxy-based glass and jute fibres reinforced hybrid composites are fabricated varying fibre stacking sequences, 1jute-1glass alternatively (j-g-j-) and 4glass-9jute-4glass (4g-9j-4g). hybridization of jute and glass fibre results better tensile, flexural and water absorption properties than only jute fibre reinforced composites but inferior to only glass fibre reinforced composites. the 4g-9j-4g stacking sequence resulted in better mechanical and water absorption properties than j-g-j-stacking sequence. the effect of chemical treatment and glass microfiber infusion are also investigated. chemically treated jute fibre and 2 wt.% microfiber infused hybrid composite shows about 42% improvements in flexural strength as compared to untreated and without microfiber infused composites. however, fibre chemical treatment and microfiber do not have a positive impact on tensile strength. keywords: hybrid composites; compression molding; chemical treatment; micro-filler infusion; mechanical properties. 1 introduction fibre reinforced polymer (frp) composites have been extensively utilized for many structural applications like automotive parts, airplanes interior parts, household appliances, and construction materials [1]. the environmental concerns have led to substantial attention in the development of new composite materials with addition of more than one reinforcement that is derive from biodegradable resources, such as natural lignocellulosic fibres (i.e., jute, kenaf, hemp, bamboo, wood, etc.) [2]. the adaptation of natural lignocellulosic fibres as reinforcement for different applications has been gaining attention by research communities. according to science direct, the number of publications on “natural fibre composites” since 1995 has been growing exponentially every year [3]. natural fibre reinforced composites exhibit lower mechanical properties than synthetic fibre reinforced polymer composites. however, natural fibre reinforced composites properties can be extended by hybridization with synthetic fibres and can provide a sustainable alternative to existing engineering materials in many structural applications. hybrid fibre reinforced polymers use two or more reinforcements with a single matrix giving rise to a more favourable balance between advantages and disadvantages of two different types of reinforcement [4, 5]. hybrid composite materials offer a range of properties that cannot be obtained with a single type of reinforcement. the fibre reinforced polymer composites can be manufactured by adopting various manufacturing techniques such ashand lay-up, compression molding, injection molding, auto-clave, and vacuum assisted resin transfer molding (vartm) processes [6]. the combination of a high strength fibre such as glass or carbon with natural fibres can yield a favourable combination of performance, cost and environmental attributes. glass fibre epoxy composites have been hybridized with jute [7], sisal [8] and bamboo [9] fibres. there are some studies reported on jute fibre reinforced hybrid composites. ramesh et al. [10] investigated the randomly oriented jute/glass fibre (gf) reinforced polyester composites fabricated with hand lay-up technique. another research group studied on jute/gf reinforced-epoxy composites with 14% weight content jute fibres [11]. they utilized hand lay-up and compression molding techniques. sabeel ahmed et al. [12] explored the effects of hybridization of glass fibre on low velocity impact behaviour and damage tolerance capability alam et al. (2022): international journal of engineering materials and manufacture, 7(1) 35-46 36 of woven jute fabric reinforced composite. the gf content increased the peak load and decreased the energy absorption. the deflection of the specimen was decreased with increasing the gf content. the hydrophilic natural fibres and hydrophobic polymeric materials when brought together may lead to undesirable mechanical properties due to inadequate interfacial adhesion between them [13]. to improve bonding between natural lignocellulosic fibres and matrix one approach is to treat natural lignocellulosic fibres with some chemicals such as alkali prior using them as reinforcement [14, 15, 16]. in frp composites the weak properties of matrix and interphase zone is another critical issue that can lead to undesirable characteristics of composites such as interfacial cracking, delamination and decreased fatigue resistance, which in turns severely limits the applications of frp composites. infusion of nano / micro-fillers in the frp that will enhance interfacial bonding by creating bridges between fibre layers that results in improved mechanical properties of the hybrid composite material [17]. there are many researchers around the globe is working on natural fibre reinforced as well as hybrid fibre reinforced composite materials. for the replacement of synthetic fibre reinforced composites with hybrid composites, it requires more research to improve mechanical, thermal and physical properties. as per literature survey, no study reported the effect of fibre stacking sequence, chemical treatment of jute and micro fibre infusion altogether on mechanical and water absorption properties of jute-glass reinforced hybrid composite. in this study, bi-directional woven jute and glass fibre reinforced hybrid composite panels are fabricated through hand layout followed by compression molding techniques. different fibre stacking sequences are used for analyzing its effect on mechanical and water absorption properties. jute fibres are chemically treated and chopped glass microfibers are infused for further improvement of mechanical and water absorption properties. figure 1: left) jute fabric, right) glass fabric 2 experimental procedures 2.1 composite fabrication in this research, bi-directional woven mats of jute fibre and glass fibre were used as reinforcement and thermosetting polymer epoxy resin was used as matrix. curing reaction of epoxy resin took place at room temperature after mixing a curing agent called hardener at a ratio of 10:1. the composites panels were manufactured by hand lay-up followed by a compression molding process. during the fabrication process a releasing agent was first sprayed onto the mold surface. then a layer of the bidirectional woven fibre was laid down, followed by a quantity of liquid epoxy resin poured onto it. the process was repeated until the required number of layers was built up. finally, these specimens were taken to the compression molding setup to apply force and remove air gap and excess resin. the panels were cured at pressurized (5000-6000psi) condition at room temperature for 24 hours. thickness of fabricated were in the range of 5.2-6.5 mm. figure 2 shows fabricated composite panels id along with their fibre stacking sequences. different fibre stacking sequences as well as manually chopped micro glass fibres (20-50 µm length; 2 wt.% of total fibre weight) were used to observe the variation of mechanical and water absorption properties of the fabricated composite panels. chopped micro glass fibre first mixed with only epoxy before adding any hardener and stirred manually vigorously to make a proper mixture. to manufacture chemically treated jute fibre and glass reinforced hybrid composite panels, jute fibres were cleaned and immersed into a 5% naoh solution for 2 hours at room temperature [14, 16]. after that, the jute fibres were filtered and thoroughly washed with distilled water. finally, the naoh treated fibres were dried in an oven at 100°c for 2 hours. figure 2: different fibre sequence and composite id. right side composites are with micro filler infused investigation of jute and glass fibre reinforced hybrid composites manufactured through compression molding process 37 figure 3: universal testing machine with tensile testing grip and sample. 2.2 tensile test tensile testing is a destructive test process that provides information about the tensile strength, yield strength, and ductility of the materials. the tensile strength of a composite material is very high in the direction parallel to the fibre orientation, while the tensile strength is much lower if tested in any other direction. the fabricated composites were cut for tensile testing as per the astm d3039 standard. uniaxial tensile test was performed at a cross head speed of 1.2 mm/min with shimadzu 300 knew utm (figure 3). at least three samples were tested from each category. 2.3 bending test flexural strength, also known as mod bend strength, or transverse rupture strength is a material property, defined as the stress in a material just before it yields in a flexure test. the transverse bending test is most frequently employed, in which a specimen having either a circular or rectangular cross-section is bent until fracture or yielding using a threepoint flexural test technique. the flexural strength represents the highest stress experienced within the material at its moment of yield. in this work, bending test was carried out by using shimadzu 300kn universal testing machine at a cross head speed of 2 mm/min. support span to depth ratio of 16:1 was maintained. flexural strength test was conducted as per astm d790 standard. three samples were tested from each category. 2.4 interlaminar shear strength (ilss) test the interlaminar shear strength (ilss) test is used to find out the strength inter laminar shear of multi lamina composite. it is usually determined by the short beam shear (sbs) test. ilss testing was carried out using a shimadzu 300 kin universal testing machine under three-point bending mode according to the astm d 2344-00 standard at a crosshead speed of 1.3 mm/min. the span length to depth ratio of the specimen was 6 and the width of the specimen was almost double the thickness. the ilss was calculated using the eq. (i). 𝐼𝐿𝑆𝑆 = (0.75× p)/(b×h) (i) where, p is the maximum load (n), b and h are the width and thickness of the specimen, respectively, in mm. 2.5 water absorption test for the water absorption test, the astm d5229 standard was followed. three specimens (150 mm×20mm×t) from each category were dried in an oven at 100°c temperature for 1 hour followed by cooling to room temperature in desiccators. immediately upon cooling the specimens were weighed (i.e. dry weight, 𝑊1). the weighted specimens were then immersed into distilled water at room temperature (25 °c) for 24 hours. immersed specimens were removed, patted dry with a dried cloth paper and weighed (i.e. wet weight, 𝑊2). water absorption is expressed as an increase in weight percent (eq. ii). percentages of water absorption (%) = (𝑊2 − 𝑊1)/ (𝑊1 × 100)% (ii) 2.6 morphological test morphological characterization of the fractured composite surface was analysed through a scanning electron microscope (sem). composite samples are cleaned properly and cut at the fractured region according to the allowable specimen size of sem finally observed at the sem at 1-2kv. 3 results and discussions 3.1 fibre volume fraction the fraction of fibre reinforcement is very important in determining the overall mechanical properties of fibre reinforced composites. a higher fibre volume fraction typically results in better mechanical properties of the composites. the fibre volume fraction can be calculated using a combination of weights, densities and volume of the matrix and fibres. the fibre volume fraction can be calculated utilizing following three equations (eq. iii-v). the experimented data and calculated fibre volume fraction are shown in table 1. alam et al. (2022): international journal of engineering materials and manufacture, 7(1) 35-46 38 table 1: fibre volume fractions of the fabricated composite panels sample id jute fibre mass (𝑚𝐽𝑓), gm glass fibre mass (𝑚𝐺𝑓), gm matrix mass (𝑚𝑚), gm fibre volume fraction (𝑉𝑓 ) s1 99.85 155.30 121.65 0.61 s2 117.68 165.15 121.31 0.64 s3 90.05 181.96 125.02 0.61 s4 110.54 181.06 108.54 0.66 s5 96.63 170.55 133.14 0.60 s6 89.00 198.40 98.44 0.67 s7 95.33 200.21 133.32 0.61 s8 91.04 195.88 109.51 0.65 s9 216.00 0.00 300.50 0.44 s10 0.00 482.00 150.35 0.63 only jute fibre reinforced composite panels had the lowest fibre volume fraction which is about 44% and the fibre volume fraction of hybrid composite having different fibre stacking sequences varies between 60% 67%. even though same number of glass and jute fibre lamina were used for composites s1 to s8 but the total weights of glass and jute fibres were not exactly the same. this is because each fibre lamina's cutting dimension was meant to be 200 mm by 200 mm, but the actual dimensions varied somewhat when we manually cut them. 𝑉𝑓 = 𝑣𝑓 𝑣𝑐 × 100% (iii) 𝑣𝑐 = 𝑚𝐽𝑓 𝜌𝐽𝑓 + 𝑚𝐺𝑓 𝜌𝐺𝑓 + 𝑚𝑚 𝜌𝑚 (iv) 𝑣𝑓 = 𝑚𝐽𝑓 𝜌𝐽𝑓 + 𝑚𝐺𝑓 𝜌𝐺𝑓 (v) were, 𝑉𝑓 = fiber volume fraction. 𝑣𝑓 = volume of fiber. 𝑣𝑐 = volume of composite panel. 𝑚𝐽𝑓 , 𝑚𝐺𝑓 , 𝑚𝑚 = mass of jute fiber, glass fiber and matrix in the composite panel, respectively. 𝜌𝐽𝑓 , 𝜌𝐺𝑓 , 𝜌𝑚 = density of jute fiber (1.3 g/cm³), e-glass fiber (2.62 g/cm³) and matrix (1.4 g/cm³), respectively. 3.2 ultimate tensile strength for the tensile test, at least three specimens from each panel were tested on the universal testing machine (utm). tensile stress-strain curves of the fabricated composite panels are presented in figure 4. all the curves show a similar pattern. average ultimate tensile strength (uts) values with standard deviation are presented with a bar graph shown in figure 5. only glass fibre reinforced epoxy composites (s10) showed highest average ultimate tensile strength (uts) value of 391 mpa whereas only jute fibre (untreated) reinforced composite samples (s9) showed lowest average uts value of 37 mpa. jute fibre is mostly consisting of cellulose which is inherently weaker than synthetic glass fibres made from silicate glass or phosphate-based glass. as a result, in terms of mechanical properties utilizing simply jute fibre as reinforcement is not worthwhile [21]. the hybridization of jute and glass fibres (s1 to s8) resulted in average uts values much higher as compared to only jute fibre reinforced composite samples (s9). the higher tensile strength values of the hybrid composite panels illustrate the potentiality of the use of hybrid composite material in different structural applications. the average uts values of hybridized composite samples also depend on the fibre stacking sequences, chemical treatment of jute fibre and micro-filler reinforcement (figure 6). two different types of fibre stacking sequences (4g9j-4g and g-j-g-j—alternatively) were investigated in the current study. the untreated jute fibre reinforced 4g-9j-4g stacking sequence hybrid composite samples (s1) showed an average uts value of 191.55 mpa whereas j-g-j-alternatively stacked sequence samples (s6) resulted in uts value of 219.82 mpa. the chemical treatment of the jute fibre did not improve tensile strength of the hybrid composite samples (s2 and s4). the micro-filler infusion (i.e., 2% chopped glass fibre) also had no significant effect on the tensile strength of hybridized composite samples (s3, s5, s7 and s8). micro-filler infusion in the hybrid composite panels might cause a reduction of the overall fibre volume content in the fabricated composite panels which in turns may affect adversely on the uts values. on the otherhand, micro-fillers usually enhance the flexural strength of the composite panels by making bridging between laminas. for morphological analysis of the tensile tested samples, scanning electron microscopic (sem) images are analysed. when tensile load is applied most of the composite failed due to fibre breakage and debonding (figure 7). due to the uneven distribution of chopped micro fibre agglomeration is seen in the micrographs which explain the reason behind having low tensile strength when micro fibre is added to the composite. this agglomeration acts as a stress concentration point. investigation of jute and glass fibre reinforced hybrid composites manufactured through compression molding process 39 figure 4: tensile stress strain curves for hybrid composite panels: (a) s1, (b) s2, (c) s3, (d) s4, (e) s5, (f) s6, (g) s7 and (h) s8 alam et al. (2022): international journal of engineering materials and manufacture, 7(1) 35-46 40 figure 5: bar graph showing average uts values of the different composite panels. figure 6: average tensile strength comparisons of fabricated hybrid composite panels. figure 7: sem micrographs of fractured tensile samples having 4g-9j-4g stacking sequence with 2% chopped microfiller: a) untreated jute and glass (s8); b) treated jute and glass (s3) 3.3 bending strength three-point bending test was performed on fabricated hybrid composite samples. flexural or bending strengths are calculated from the bending test. failure due to the three-point bending test mainly occurs due to compression, shear, and tension [18]. flexural stress-strain curves of the fabricated hybrid composite panels are presented in figure 8. all the curves show a similar pattern. the average bending strength values are shown in the bar graphs in figure 9. from the bar graph, it is clearly remarked that the 4g-9j-4g stacked sequence samples (s1, s2, s3 and s8) possess higher bending strength as compared to j-g-j—alternatively stacked sequence samples (s4, s5, s6, s7). chemical treatment as well as chopped glass microfiber infusion resulted in higher bending strength of the hybrid composite panels. about 42% bending strength increased due to chemical treatment of jute fibre and microfiber infusion (s3). the higher bending strength might be related to the higher percentage of cellulose exposure in treated fibres [16] and interlocking action of chopped microfibers [17, 19]. investigation of jute and glass fibre reinforced hybrid composites manufactured through compression molding process 41 bending test fractured samples sem micrographs were also analysed. almost all composite samples under flexural loading were failed due to fibre breakage and delamination (figure 10). figure 10(a) & figure 10(b) show micrographs of ruptured bending samples were linking of micro glass fibre is seen. in figure 10(c) resin adhesion to fibre is visible which indicates the better bonding resulted due to chemical treatment of jute fibre. figure 8: bending stress strain curves for hybrid composite panels: (a) s1, (b) s2, (c) s3, (d) s4, (e) s5, (f) s6, (g) s7, and (h) s8 alam et al. (2022): international journal of engineering materials and manufacture, 7(1) 35-46 42 figure 9: average bending strength comparisons of fabricated hybrid composite panels. figure 10: sem micrographs of fractured bending sample with 2% chopped micro-filler: a) 4g-9j-4g untreated jute and glass (s8); b) 4g-9j-4g treated jute and glass (s3); c) g-j-g-alternatively treated jute and glass (s5) 3.4 effect of stacking sequences on tensile and bending strength tensile strength and bending strength of the fabricated composite panels with 17layer jute and glass fibres with fibre stacking sequence 4g-9j-4g are shown in figure 11 and j-g-j-(alternatively) are shown in figure 12. it is observed that 4g-9j-4g stacked composites lead to improved bending strength than tensile strength while j-g-j-(alternatively) stacked composites do not have any significant difference. in the 4g-9j-4gstacking sequence composites, the top four and bottom four glass fibres act as a shield to the core jute fibres and bear most of the applied flexural load hence the superior bending strength was observed (figure 13). however, under tensile strain, the entire core of weak and brittle jute layers cracked simultaneously, leaving the outer glass layers delaminated [21]. this explains the reason for having lower tensile strength than bending in 4g-9j-4g stacking sequence composites. this result is consistent with other researchers [20]. the chemical treatment of jute fibre and chopped microfiber infusion do not have a significant effect on tensile strength of the fabricated composite panels. however, both chemical treatment of jute fibre and microfiber infusion has a significant effect on bending strength of fabricated hybrid composite panels. investigation of jute and glass fibre reinforced hybrid composites manufactured through compression molding process 43 figure 11: average tensile and bending strength comparisons of fabricated hybrid composite panels having 4g-9j-4g stacking sequence. figure 12: average tensile and bending strength comparisons of fabricated hybrid composite panels having g-j-g-j- (one by one) stacking sequence. figure 13: optical images of tensile and bending tests fractured samples having different fibre stacking sequences. 3.5 inter laminar shear strength (ilss) interlaminar shear strength test results of cm composites are figure 14. ilss properties of cm composite panels show a similar pattern just as like as flexural properties of cm composite panels. from the bar graph, it is clearly remarked that the 4g-9j-4g stacked sequence composite panels (s1, s2, s3, and s8) possess higher ilss as compared to g-j-g-j— alternatively stacked sequence composite samples (s4, s5, s6, s7). chemical treatments, as well as chopped glass microfiber infusion, resulted in higher ilss of the hybrid composite panels for enhancing interlocking action. 3.6 water absorption test results jute fibres have a high water absorption rate, but glass fibres are less prone to absorb water. each cell wall of jute fibre is made up of three main components which are cellulose (slender rod like crystalline microfibrils that are alam et al. (2022): international journal of engineering materials and manufacture, 7(1) 35-46 44 resistant to hydrolysis), hemicelluloses (hydrophilic polysaccharides that act as a cementing matrix between cellulose microfibrils and can be easily hydrolyzed by dilute acids and bases) and lignin (complex hydrocarbon polymer that assists on the transportation of water). hydrophilic properties of jute fibres and other natural fibres are attributed to the presence of these hydroxyl and other polar groups [22]. due to this hydrophilicity sample s9 (only jute) composites absorbs maximum water (2.73%) than any other hybrid combination of jute and glass fibre. whereas only glass fibre reinforced composite sample (s10) absorbs lowest amount water (0.63%) (figure 15) hybrid composite panels absorb around 1.5% water. there is a slight decrement in water absorption observed in chemically treated jute fibre reinforced and chopped glass microfiber infused hybrid composite panels. water is absorbed due to the capillary action of fibres through micro cracks [23,16]. microcracks were more prevalent in untreated fibre reinforced composites. treated fibre reinforced and chopped micro fibre infused samples had lower microcracks, resulting in lower water absorption. chemical treatment also reduces the amount of hydrophilic hemicelluloses from the jute fibre and washes away lignin content which limits water transportation inside composite. these two factors contributed to the lower water uptake in chemically treated fibre reinforced composite. moreover, infused chopped glass microfiber provided additional resistance to water uptake. as a result, among the hybrid composites panels, sample s3 (4g-9j-4g stacking sequence treated and micro-filler infused) has the lowest water absorption capacity which is about 1.48%. the comparison in water absorption capability of 4g-9j-4g and j-g-j-alternatively stacking sequences in fabricated hybrid composite panels are shown in figure 16. samples having 4g-4j-4g stacking sequence have lower water absorption as compared to j-g-j-alternatively stacking sequence. stacked hydrophobic glass fibre at the top and bottom in 4g-9j-4g composites significantly reduce water absorption by acting as a barrier to prevent water from being absorbed by inner hydrophilic jute fibre that gives 4g-9j-4g stacking sequence composites the water resistance superiority. similar results are obtained by another research group for different fibre reinforced composite [20]. figure 14: inter laminar shear strength (ilss) of hybrid composite panels figure 15: average water absorption of fabricated composite panels. investigation of jute and glass fibre reinforced hybrid composites manufactured through compression molding process 45 figure 16: effect of stacking sequence on water absorption of fabricated composite panels. 4 conclusions this work is based on fabrications of hybrid composites with different combination of natural fibre (i. e. jute fibre) and synthetic fibre (i.e. e-glass fibre) as a reinforcement and epoxy resin as matrix utilizing compression molding method. the fabricated composite panels were analysed by comparing different mechanical and physical properties. 1. only glass fibre reinforced composite resulted in better tensile, bending and water absorption properties compared to other panels which is obvious. then again only jute fibre reinforced composite panels have lowest tensile and flexural properties and highest water absorption as compared to other fabricated samples. hybridization of jute and glass fibre resulted in tensile, flexural and waters absorption properties in between only natural and only synthetic fibre reinforced composites. 2. the variations of tensile strength, bending strength and water absorption was observed due to variation of fibre stacking sequences (i.e., positions of lamina). the 4g-9j-4g stacking sequences resulted in better mechanical properties as compared to the j-g-j--(alternatively) stacking sequence. 3. the effect of chemical treatment of jute fibre and infusion of chopped glass microfiber are also investigated in this study. both the chemical treatment of jute fibre and infusion of microfiber resulted in higher bending strength in the fabricated hybrid composite panels. but the chemical treatment of fibre and microfiber infusion does have insignificant effect on tensile strength and water absorption properties of hybrid composite panels. 4. the fabricated composite hybrid composite panels can be utilized as a replacement of conventional materials in different structural applications. acknowledgement the author gratefully acknowledges the funding received from university grant commission (ugc) and duet, gazipur. bangladesh. the author would also like to acknowledge the department of mechanical engineering, duet, gazipur for permitting to use their testing facilities. references 1. sanjay mr, madhu p, jawaid m, senthamaraikannan p, senthil s, pradeep s. characterization, and properties of natural fibre polymer composites: a comprehensive review. journal of cleaner production. 2018;172;566-81. 2. shahzad a. hemp fibre and its composites – a review. journal of composite materials.2012;46(8);973-86. 3. costa u, nascimento l, garcia j, bezerra w, da costag, daluzf.. mechanical properties of composites with graphene oxide functionalization of either epoxy matrix or curaua fibre reinforcement. journal of materials research and technology. 2020. 9(6);13390-401. 4. jawaid m, abdul khalil hps. cellulosic/synthetic fibre reinforced polymer hybrid composites: a review. carbohydrate polymers. 2011;86(1);1-18. 5. dhakal hn, zhang zy, guthrie r, macmullen j, bennett n. development of flax/carbon fibre hybrid composites for enhanced properties. carbohydrate polymers.2013;96(1);1-8. 6. sathish k. t, naveen j, satheesh k. s. hybrid fibre reinforced polymer composites – a review. journal of reinforced plastics and composites. 2014;33(5);454-71. 7. koradiya sb, patel jp, parsania ph. the preparation and physicochemical study of glass, jute and hybrid glass-jute bisphenol-c-based epoxy resin composites. polymer-plastics technology and engineering. 2010; 49(14);1445-49. alam et al. (2022): international journal of engineering materials and manufacture, 7(1) 35-46 46 8. kumar m, reddy g, bharathi y, naidu s, naidu v. frictional coefficient, hardness, impact strength, and chemical resistance of reinforced sisal-glass fibre epoxy hybrid composites. journal of composite material. 2010; 44(26); 3195-202. 9. kushwaha pk, kumar r. the studies on performance of epoxy and polyester-based composites reinforced with bamboo and glass fibres. journal of reinforced plastics and composites. 2010; 29(13);1952-62. 10. ramesh m, palanikumar k, reddy kh. mechanical property evaluation of sisal–jute–glass fibre reinforced polyester composites. composites part b: engineering. 2013;48;1-9. 11. ramesh m, palanikumar k, reddy kh. comparative evaluation on properties of hybrid glass fibresisal/jute reinforced epoxy composites. procedia engineering. 2013; 51; 745-50. 12. ahmed ks, vijayarangan s, kumar a. low velocity impact damage characterization of woven jute—glass fabric reinforced isothalic polyester hybrid composites. journal of cleaner production. 2007; 26(10); 959-76. 13. filho f, da luz f, oliveira m, pereira a, costa u, monteiro s. thermal behavior of graphene oxide-coated piassava fibre and their epoxy composites. journal of materials research and technology. 2020; 9(3); 5343-51. 14. hossain mk, dewan mw, hosur m, jeelani s. mechanical performances of surface modified jute fibre reinforced biopol nanophased green composites. composites part b: engineering. 2011; 42(6); 1701 –7. 15. hamidon mh, sultan m, ariffin a, shah a. effects of fibre treatment on mechanical properties of kenaf fibre reinforced composites: a review. journal of materials research and technology. 2019; 8(3); 3327-37. 16. dewan mw, hossain mk, hosur m, jeelani s. thermomechanical properties of alkali treated jutepolyester/nanoclay biocomposites fabricated by vartm process. journal of applied polymer science. 2013; 128(6); 4110-23. 17. hossain mk, hossain me, dewan mw, hosur m, jeelani s. effects of carbon nanofibers (cnfs) on thermal and interlaminar shear responses of e-glass/polyester composites. composites part b: engineering. 2013; 44(1); 31320. 18. nurazzi nm, khalina a, chandrasekar m, aisyah ha, rafiqah sa, ilyas ra,hanafee zm. effect of fiber orientation and fiber loading on the mechanical and thermal properties of sugar palm yarn fiber reinforced unsaturated polyester resin composites. polimery. 2020; 65(02);115-24. 19. gibson rf, yau a. complex moduli of chopped fibre and continuous fibre composites: comparison of measurements with estimated bounds. journal of composite materials. 1980; 14(2); 155-67. 20. sujon mas, habib ma, abedin mz. experimental investigation of the mechanical and water absorption properties on fibre stacking sequence and orientation of jute/carbon epoxy hybrid composites. journal of materials research and technology. 2020; 9(5); 10970-81. 21. singh h, preet singh ji, singh s, dhawan v, tiwari sk. a brief review of jute fibre and its composites, materials today: proceedings. 2018; 5(14); 28427-28437. 22. azwa zn, yousif bf, manalo ac, karunasena w. a review on the degradability of polymeric composites based on natural fibres, materials & design. 2013; 47; 424-442. 23. dhakal hn, zhang zy, richardson mow. effect of water absorption on the mechanical properties of hemp fibre reinforced unsaturated polyester composites, composites science and technology. 2007; 67(7-8); 1674-1683. international journal of engineering materials and manufacture (2020) 5(1) 12-18 https://doi.org/10.26776/ijemm.05.01.2020.03 m. rakib uddin and muhammad faiz bin haji ya’akub electrical and electronics engineering programme area, faculty of engineering universiti teknologi brunei, brunei darussalam email: rakib.uddin@utb.edu.bn reference: rakib uddin, m. and ya’akub, m. f. (2020). parked car interior temperature investigation in brunei darussalam. international journal of engineering materials and manufacture, 5(1), 12-18. parked car interior temperature investigation in brunei darussalam m. rakib uddin, and muhammad faiz bin haji ya’akub received: 04 february 2020 accepted: 26 march 2020 published: 30 march 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 abstract when a car is parked under the sunlight for a long period of time, solar radiation enters the vehicle through the car glass and becomes trapped inside the car. this causes the cabin interior air temperature to increase and this is especially noticeable in tropical countries with hot and humid climates that are situated near the equator like brunei darussalam. aside from causing thermal discomfort to the passengers inside the car, degradation of the surfaces of the car interior may also be accelerated. this paper aims to demonstrate the severity of the heat by recording a number of temperature measurements in a certain period of time for two different types of cars, under three different conditions for each car and comparing them to the ambient temperature. it is observed that the interior temperature depends on the design of the car. we experimented temperature measurements for two types of car models, i.e., saloon and suv models. saloon car is design such as way that its interior volumes space is smaller than the suv designed car. the smaller interior volume spaced saloon car exhibits higher maximum temperature of 68.7°c whereas the larger interior volume spaced suv car exhibits maximum temperature of 59.4°c under fully exposed to sun with same environmental conditions. keywords: car interior air temperature; ambient temperature; thermal discomfort 1 introduction prolong exposure to sunlight can significantly increase the temperature inside a parked car when the car’s engine is off. this is due to the solar radiation that enters the vehicle through the window panels and becomes partially trapped within the cabin of the car. this causes the temperature to rise substantially when the occupants get back into the parked car. the main issue that comes from the highly elevated temperature is thermal discomfort to the passengers. aside from that, it may also accelerate the degradation of the surfaces of the car interior after being exposed to sunlight for so long and are subjected to stress from the increasing heat. the main purpose of this investigation is to find out the variation of interior air temperature in relation to the ambient temperature with respect to time. to prove that the interior air temperature of the vehicle does indeed rise significantly, a series of tests has been devised to monitor and gather some data from inside two different types of cars, under three different conditions of each car. the objectives of this paper are to; take multiple measurements of the interior air temperature of the car within certain period of time of the day; repeat the process for different types of sunlight exposure and for different types of cars; investigate the relationship of the interior air temperature variation in relation to the ambient temperature outside the car by graphically showing the characteristics. in may 2014, w. a. a. fadeel et al, has made a journal about temperature variations in a parked car exposed to direct sun during hot and dry climates in aswan, egypt [1]. they have concluded that the temperature levels inside a parked car can increase to as much as 80 °c. in a similar study, m.s.f. mansor et al. [2] concluded that the trapped and accumulated heat causes the temperature inside a car to reach up to 50 ̊c. this has caused many fatalities being reported as a result of internal car heat. russell manning and john ewing had also made a report about temperature in cars survey [3]. their report touches on several ways of investigating the temperature of inside a car. on vehicles having different paint colours, they have concluded that the rate of temperature increase inside the cabin is similar, regardless of paint colour. on having the windows slightly open versus having it fully closed, it was concluded that the peak temperature was still dangerously high for both cases but the one with windows slightly open has a slower temperature rise inside the cabin of the car. lastly, their temperature investigation also include the use of sunshades and tinted films inside the test car, which both results in only an insignificant difference to the rate of temperature rise with only a marginal difference to the final peak cabin temperatures. m. pešek, brno university of technology has made an article about the temperature field’s measurement of air in rakib uddin and ya’akub (2020): international journal of engineering materials and manufacture, 5(1), 12-18 13 the car cabin by infrared camera [4]. in october 2013, sudhir chitrapady vishweshwara et al. made a journal about the study of excessive cabin temperatures of the car parked in oman and its mitigation [5]. their study has concluded that on a bright sunny day, the vehicles cabin temperature rises to about 22°c above ambient temperature. however, upon installing the mitigation, the difference between cabin and outside temperature was greatly reduced. in august 2015, an independent test was carried out by doug demuro on the impact of car colour to the interior temperature [6]. in the heat, the colour of the car can have an impact: with black cars heating up quicker and cooling down slower than white ones. the black car's cabin measured a scorching 130 ̊f (54°c), while the white car's interior registered only 113 ̊f (45°c). he discovered that the interior of the white car cooled to 84 ̊f (29°c) after 10 minutes of turning the air-conditioning back on, while the black car was still at 91 ̊f (27°c). another study by h. h. al-kayiem et al [7], mentioned that the thermal condition inside the car forces the car user to wait 2-5 minutes to cool down the hot interior air and this increases fuel consumption. several studies also found that the heat inside the car can cause health concerns as mentioned in the findings by c. mclaren et al [8] and a. grundstein et al. [9]. in this paper, we aim to demonstrate the severity of the heat by recording a number of temperature measurements in a certain period of time for two different types of cars, under three different conditions for each car and comparing them to the ambient temperature in brunei darussalam. we found that the interior air temperature can reach a maximum of 68.7°c when the car is fully exposed to sunlight. even when the car is fully shaded from the top, the temperature can reach a high of 43°c. the rest of the paper is organized as below: in section 2, the temperature measurement investigation setup is described. in section 3 of this paper, the analysis of temperature investigation data was explained. lastly, section 4 describes the conclusion of this paper. 2 temperature investigation setup to investigate the temperature characteristics, specialised equipment and proper steps and procedure is needed. 2.1 device under testing the test cars used were a black coloured 2010 ford fiesta for the saloon experiment and a light-green coloured 2004 ssangyong rexton for the suv experiment. the ford fiesta is a compact saloon/sedan type of car that can accommodate 5 people, while the ssangyong rexton is a large-size 7-seater suv that has a very large cabin size, as shown in fig 1 and 2. figure 1. schematic of a 2010 ford fiesta saloon (dimensions are in mm) figure 2. schematic of a 2004 ssangyong rexton suv (dimensions are in mm) 2489 4291 1 4 9 6 1722 all measurements in millimetres. 2830 4730 1 7 7 0 1880 all measurements in millimetres. parked car interior temperature investigation in brunei darussalam 14 2.2 measuring equipment the test was carried out using a temperature data logger made by the company elitech. officially called the elitech usb temperature data logger rc-5, it has a wide measuring range of -30°c to 70°c, with a resolution of 0.1°c and an accuracy of ±0.5°c. it uses an internal ntc thermal resistor as its sensor as the unit itself is ip67 rated water resistance. the rc-5 can automatically gather temperature data over a set amount of time and can be transferred using the built-in usb connection. the main reason for using this specific equipment is due to its wide temperature range and robust hardware, which makes it very suitable for this application. the data logger is also specialised for measuring temperature inside a confined or enclosed space such as a room or a car. 2.3 test area and period the cars were tested at a private and open land area in located in bandar seri begawan, brunei darussalam. the location has a very large open space that can ensure that the tested cars are not shaded when the temperature is logged. the test was carried out at random days where there was generally sunlight throughout the day from 9 am to 5 pm for each day, from december of 2017 until the march of 2018. 3 experimental method before carrying out the temperature measurements, the rc-5 data logger’s parameters must be set using a computer through the given proprietary software by elitech. first, both the rc-5 data loggers must be calibrated properly. although they are claimed to be pre-calibrated by elitech from the factory, sometimes they have some little tolerance that can cause some discrepancy. in this case, the data logger was then calibrated using the given proprietary software using a known already calibrated shtc1 sensor as a basis of control. this is shown in fig 4 and 5. next, the measuring parameters are then set using the same software. in this case, the real-time clock was synced with the correct time on the computer and the time interval was then set for 5 minutes. this means that the data logger will automatically record and save the current temperature every 5 minutes. the rc-5 data logger was then put inside the car and was suspended by a small rope in the approximate centre of the interior between the font seats of the car as to avoid contact with the interior surfaces. this is shown in fig 6. the purpose of this is for measuring only the interior air temperature of the vehicle, rather than surface temperature of the car interior. it was placed inside the car for at least 10 to 15 minutes before 9am to ensure that the air temperature inside the car settles down after the door was being opened for the installation of the data logger. the data logger was kept inside the car for the total duration of 8 hours. it was important to ensure that none of the door or windows were open throughout the whole duration. the tests were carried out in three different conditions for each types of cars. on condition 1; the car was parked in an open area, more than 25 metres from any buildings or trees to ensure that the car will not be shaded in any way at any time from 9 am to 5 pm, as shown in fig 7. on condition 2; the car was parked relatively near to a building, around less than 10 metres to the nearest building, as shown in fig 8. in this case, the car was partially shaded at certain time of day, except for mid-day where the car was fully exposed and not shaded because the sun is directly above the car. on condition 3; the car was parked under an open type garage or shed where the car is only fully shaded from the top but not from the sides or the front, as shown in fig 9. for each condition, at least five days’ worth of measurements were taken for each car for each conditions to make a sizeable sample of data. 4 experimental results and analyses to compare the temperature data obtained from the rc-5 temperature data logger, there must also be data for the ambient temperature during the same period of time in the day. the samples for ambient temperature were taken from the weather underground website for the hourly forecast temperatures for each day. condition 1 can be considered as the worst case scenario for temperature increase because the car is fully exposed for the total duration of 8 hours in direct sunlight and the graph in figure 10 reflects that. after just 1 hour from 9:00am, the interior air temperature already rose by about 18.6°c (from 32ºc to 50.6ºc) which is respresents a sizable 58.1% increase. figure 3. rc-5 temperature data logger figure 4. calibrating and setting the time interval parameter setting the record interval calibrating function rakib uddin and ya’akub (2020): international journal of engineering materials and manufacture, 5(1), 12-18 15 figure 5. calibrated data logger figure 6. placement of equipment inside the car figure 7. condition 1, car is fully exposed to sunlight and located more than 25 m from any buildings figure 8. condition 2, car is partially shaded at certain times and located less than 10 m from any buildings figure 9. condition 3, car is shaded under open type shed also by observing the graph, the interior air temperature usually reached within 10% of the maximum at around 1:00pm and stays about constant until around 4:00pm where the temperature starts to fall off because the decrease in sunlight intensity. the highest interior air temperature of 68.7°c obtained was on march 23 and 24 at exactly 2:30 pm. at that exact time, the ambient temperature was 31°c and when compared with the interior air temperature of 68.7°c, the percentage difference was a significant 45.1%. as for the case of the suv type car for condition 1 as shown in fig 11, the initial interior air temperature seems to start of higher than that from the saloon type car. this may be due to the bigger surface area of the windows of the suv which leads to more sunlight entering the car especially during the morning since the data logger may be subjected from direct sunlight. the interior temperature generally reached maximum at around 2:00pm, which was similar to that of the saloon. however, the maximum temperature of 59.4°c was much lower than that from the saloon (68.7°c). as for condition 2 as shown in fig 12, the interior air temperature was very close to the outside ambient temperature even after 2 hours, from 9:00am to 11:00am. only after 11:00am does the interior air temperature saw a sharp increase as the car was being directly exposed to the sun approaching midday. the maximum interior air temperature was usually reached at around 1:00pm to 2:00pm. from then onwards, the temperature starts to slowly decrease and then at around 4:00pm, the interior temperature starts to cool down quickly. the maximum interior air temperature reached was 57.6°c. buildings or trees >25m buildings or trees <10m parked car interior temperature investigation in brunei darussalam 16 figure 10. condition 1 for saloon type figure 11. condition 1 for suv type figure 12. condition 2 for saloon type rakib uddin and ya’akub (2020): international journal of engineering materials and manufacture, 5(1), 12-18 17 for the suv type in condition 2, the characteristic was similar to that of the saloon but generally reaches its maximum interior air temperature a little later at around past 2:00pm. again the interior temperature saw a sharp decrease in temperature after 4:00pm. the maximum interior air temperature reached was 57.1ºc, about the same with the saloon. this is shown in fig 13. for condition 3, the rise in interior air temperature was significantly slower when compared to condition 1 and 2. in some cases, it could take up to 2 hours to even exceed 30ºc as seen in figure 14. looking at the graphs for january 17, the interior air temperature reached its maximum at the same time as the ambient temperature, but even at its peak there was only a mere 6.2% difference. the maximum interior air temperature reached was 34.1ºc. as for the suv in condition 3 as shown in fig 15, the initial rise has similar characteristics to that of the saloon, however the interior air temperature inside the suv kept on rising and generally hits the peak around after 3:00pm. the continued rise in temperature might be caused by the bigger surface area of the window panels of the suv, which allows reflected sunlight to enter the car from the sides even when the car is fully shaded from the top. then as with all the other conditions, the temperature drops significantly after 4:00pm, the same can be said for the ambient temperature as well. when compared to the saloon in the same conditions, while the saloon’s interior air temperature stays generally constant after 1:00pm, the suv’s interior temperature kept on rising, reaching a maximum of 43ºc, which is a significant 28% percentage difference compared to the ambient temperature. figure 13. condition 2 for suv type figure 14. condition 3 for saloon type parked car interior temperature investigation in brunei darussalam 18 figure15. condition 3 for suv type 5 conclusions the temperature investigation has been performed in three different conditions; fully shaded from the top, partially shaded and fully exposed to sunlight. when the cars were fully shaded from the top, the saloon and the suv reached 34.1ºc and 43ºc respectively. the reason of the suv having a higher maximum temperature might be due to the bigger surface area of the windows of the suv which leads to more sunlight entering the car especially around afternoon since the data logger was subjected to direct sunlight. when the car was partially shaded, the saloon and the suv reached 57.6ºc and 57.1ºc respectively. while they both achieved similar maximum temperature when being partially shaded, it should be noted that the rate of increase of interior air temperature was lower for the suv. lastly, when the car is fully exposed to sunlight, the saloon and the suv reached 68.7ºc and 59.4ºc respectively. both the maximum temperature was very high, but the maximum temperature of the saloon was significantly higher. this may be due to the saloon having less volume of air in the cabin, which makes it less insulated from heat. however, it should be noted that the suv started off with a higher interior air temperature due to it being exposed to direct sunlight in the morning. addtionally, for all the conditions, it was observed that after exactly 4:00pm the interior air temperature showed a sharp decrease on temperature. this may suggest that the sunlight intensity decreases around this time. after observing the cars under all the different conditions, it is very clear that as long as there is presence of sunlight, the interior air temperature of the car increases well past the thermal comfort level (28ºc) for humans. in our next research, we are developing a mitigation technology for this problem. acknowledgement we would like to thanks universiti teknologi brunei for financial support through final year project. references 1. w. a. a. fadeel (2013). temperature variations, inside a parked car in hot and dry climates. international journal of automobile engineering, 3(1), 75-80. 2. m. mansor et al. (2014). variation of car cabin temperature influenced by ventilation under direct sun exposure. journal of mechanical engineering and sciences, 6, 1014-1023. 3. r. manning and j. ewing (2009). temperature of cars study. february 2009. [accessed: 04-may-2018]. 4. m. pešek (2013). the temperature fields measurement of air in the car cabin by infrared camera. epj web of conferences, 45, 01073. 5. s. c. vishweshwara and j. m. a. dhali (2013). study of excessive cabin temperatures of the car parked in oman and its mitigation. international journal of multidisciplinary sciences and engineering, 4(9). 6. d. demuro (2015). car color test: are black cars really hotter in the sun?. autotrader, august 2015, http://www.autotrader.com/car-video/car-color-test-are-black-cars-really-hotter-in-the-sun-video-242940 [accessed: 04-may-2018]. 7. h. h al-kayiem, et al. (2010). study on the thermal accumulation and distribution inside a parked car cabin. american journal of applied sciences, 7(6), 784-789. 8. c. mclaren et al. (2005). heat stress from enclosed vehicles: moderate ambient temperatures cause significant temperature rise in enclosed vehicles, pediatrics, 116(1), 109-112. 9. grundstein et al. (2009). maximum vehicle cabin temperatures under different meteorological conditions. international journal of biometeorology, 53(3), 255-261. interior air temperature ambient temperature international journal of engineering materials and manufacture (2021) 6(4) 299-304 https://doi.org/10.26776/ijemm.06.04.2021.05 anis, s. m. s. 1 , ramesh, s. 1,2 , lee, k. y. s. 3 and wu t. 4 1 center of advanced manufacturing and material processing, department of mechanical engineering faculty of engineering, university of malaya, 50603 kuala lumpur, malaysia 2 department of mechanical engineering, faculty of engineering, universiti teknologi brunei be1410 brunei darussalam. 3 center of systematic innovation research, department of mechanical engineering, faculty of engineering and technology, tunku abdul rahman university college, 53300 kuala lumpur, malaysia. 4 school of mechanics, civil engineering and architecture, northwestern polytechnical university xi’an 710072, china e-mail: syufina.saufi@gmail.com reference: anis et al. (2021). densification and mechanical properties of alumina ceramics via two-step sintering with different holding times. international journal of engineering materials and manufacture, 6(4), 209-304. densification and mechanical properties of alumina ceramics via two-step sintering with different holding times anis syufina hj. mohammad saufi, ramesh singh, k. y. sara lee and tao wu received: 24 april 2021 accepted: 08 july 2021 published: 01 october 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract the densification and mechanical properties of alumina ceramics were investigated via two-step sintering (tss) with different holding time. the alumina ceramics were sintered at 1450 °c for 1 min during the first stage, followed by sintering at 1350 °c with different holding times (2-24h). conventional sintering (cs) was also performed on the alumina ceramics at 1450 °c for 2 h for comparison purpose. it was found that dense alumina with a relative density above 98% could be attained when tss with a holding time of more than 12 h. the samples exhibited vickers hardness between 5-8 gpa and fracture toughness of about 6 mpa.m 1/2 . in contrast, conventional sintered alumina yielded low relative density (85%), large grain size (2 μm), low vickers hardness (4.23 gpa) and fracture toughness (4.73 mpa.m 1/2 ). this study revealed that tss is a viable approach in aiding densification, suppressing grain growth, and improving the mechanical properties of alumina ceramics. keywords: two-step sintering, alumina, grain size, mechanical properties. 1 introduction alumina (al2o3) is one of the widely used engineering ceramics in biomedical and aerospace industries owing to its excellent biocompatibility, strength, hardness, and stability in physiological environment [1-2]. however, the sintering of alumina using the conventional method at lower temperatures frequently resulted in lower density, fracture toughness and flexural strength. as such, various sintering techniques and approaches have been employed to enhance its mechanical properties, such as addition of dopants [3], microwave sintering [4], spark plasma sintering [5] and two-step sintering [6]. since high sintering temperatures (>1450 °c) were generally required to produce high-density alumina ceramics using pressureless sintering [7], two-step sintering has been experimented to lower the densification temperatures and suppressing abnormal grain growth in order to retain a fine microstructure [8]. two-step sintering (tss) is a sintering method that consists of two stages sintering. at the first stage, the green sample is heated to a high temperature of t1 and holding at this temperature for a very short period. this is followed by the second stage, where the temperature is lowered to t2 and holding at this temperature for a longer holding time to allow densification to proceed without grain coarsening. based on the literatures, the intermediate relative density of about 70% should be attained at the first stage before proceeding to the second stage of sintering [9]. numerous studies have been examined the effect of various sintering parameters such as t1, t2 and holding time to achieve better densification. it was revealed that the densification rate of alumina was enhanced when t1 was selected between 1400-1450 °c, with a relative density of 72-88%. when t1 was higher than 1450 °c, the densification rate has been found to decrease rapidly [10]. in another study, it was found that t1 ≤ 1450 °c could avoid rapid alumina grain growth. the researchers reported that sintering at 1450 °c for an hour and further cooled down to 1350 °c for 34 h yielded alumina ceramics with relative density above 96% with no grain growth observed [11]. as for the second sintering temperature t2, it was proposed to be lower than 1400 °c to suppress grain growth. by employing t1 at anis et al. (2021): international journal of engineering materials and manufacture, 6(4), 299-304 300 1450 °c, the authors revealed that a flatter grain size-density slope was evidenced when t2 was set at 1350 °c (4, 8 and 12 h holding time), as compared to 1400 °c (4 and 8 h holding time). besides, fully dense alumina has been reported within 12 h of holding time at t2 of 1350 °c [10]. based on the research works, it was proposed that the two-step sintering temperatures t1 and t2 be set at 1450 °c and 1350 °c, respectively. however, documented works on detailed mechanical properties are rarely available. thus, this work aimed to evaluate densification and mechanical properties of alumina via conventional and two-step sintering. with the recommended sintering temperatures, different holding time was employed in the second stage of sintering. the results obtained were then compared with the conventional sintered alumina. 2 methods and materials commercially available pure alumina (kyoritsu co. ltd., japan; 99.8% al2o3 content, 150 nm mean particle size), was used in this study. the alumina powder was uniaxially pressed and cold isostatic pressed at 200 mpa (riken seiki, japan) to form solid samples. the alumina samples were first sintered at 1450 °c (t1), with a heating rate of 10 °c/min and hold for 1 min. the temperature was then lowered to 1350 °c (t2) and hold at this temperature at different holding times of 2, 4, 6, 8, 10, 12 and 24 h. conventional sintering (cs) was also carried out for the alumina sample at 1450 °c / 2 h hold for comparison purpose. detailed sintering stages of cs and tss are listed in table 1. the sintered samples were then ground using sic papers with grit sizes ranging from 120 to 1200, before polished with diamond paste of 6 μm and 1 μm to achieve reflective surfaces (imtech grinder-polisher). phase analysis was conducted using x-ray diffraction (xrd; rigaku geiger-flex diffractometer, japan), operated with a 2θ scanning range from 20° to 50°. the xrd patterns were identified using standard joint committee for powder diffraction standard (jcpds) files no. pdf#42-1468. according to archimedes’ principle, the bulk density was measured using water immersion method (densi-meter, ag204 mettler toledo, switzerland). the relative density of the sintered alumina was calculated by taking the theoretical density as 3.98 g/cm 3 . vickers hardness and fracture toughness were determined using vickers indentation technique. vickers hardness was performed using a pyramidal diamond indenter (wolpert wilson instruments, usa), with an applied load of 10 kgf, according to astm e384-99 and iso 14705. fracture toughness was evaluated using the formula proposed by shetty et al. [12]. microstructure analysis was analysed via the scanning electron microscope (sem) (philips xl30 sem, the netherlands). the average alumina grain size was then measured using the line-intercept method. table 1: sintering stages of conventional (cs) and two-step (tss) sintering sintering method sintering stage (temperature/holding time) cs 1450 °c/2 h tss1 1450 °c/1 min → 1350 °c/2 h tss2 1450 °c/1 min → 1350 °c/4 h tss3 1450 °c/1 min → 1350 °c/6 h tss4 1450 °c/1 min → 1350 °c/8 h tss5 1450 °c/1 min → 1350 °c/10 h tss6 1450 °c/1 min → 1350 °c/12 h tss7 1450 °c/1 min → 1350 °c/24 h 3 results and discussion 3.1 phase analysis, densification and microstructure evolution the xrd phase analysis revealed the presences of alumina phases for conventional and two-step sintered alumina samples, as shown in figure 1. alumina traces were detected at the angles of 25.5°, 35.2°, 37.8° and 43.4°, respectively. all the conventional and two-step sintered samples exhibited highly crystalline structures, regardless of the sintering holding time up to 24 h. the relative density and grain size of sintered alumina with different sintering holding time are presented in figure 2. for two-step sintered samples, it was observed that the relative density linearly increased with sintering holding time up to 8 h, followed by a significant increment from 92.8% (8 h) to 95.8% (10 h), with no abnormal grain growth observed. with the further increased of holding time, the relative density increased gradually and achieved highly dense samples with a relative density of about 98% (12 and 24 h). this was also accompanied by minor grain growth from 1.35 μm (12 h) to 1.65 μm (24 h). on the other hand, conventional sintered alumina showed a low relative density of 85.6% and a large average grain size of 1.93 μm, as compared with all the two-step sintered samples. figure 3 shows the correlation between grains size and relative density of the sintered samples. the results showed that there were two grain size-densification trajectory which represents the densification rate as depicted by the slope of the linear line in figure 3 could be observed for the alumina ceramic. comparison between the two trajectory slopes, indicated that rapid grain growth was observed when relative density reached 95.8% and above, where the grain size grew rapidly from 1.15 μm to 1.65 μm. li & ye [11] also reported similar findings, where fast densification and mechanical properties of alumina ceramics via two-step sintering with different holding times 301 grain growth was noticeable when relative density of alumina exceeded 90%. also, they found that two-step sintered alumina ceramics (1450 °c/1 h → 1350 °c/34 h and 1380 °c/1 h → 1330 °c/50 h) resulted in better densification and smaller grain size. sem micrographs of the conventional (cs) and two-step (tss) sintered alumina samples are shown in figure 4, which were generally comprised of equiaxed alumina grains. figure 4(b-c) shows the two-step sintered alumina at different holding time of 6 h, 10 h and 24 h, where the grain size gradually grew with the increase of holding time. it was observed that all the tss samples (with holding time up to 24 h) exhibited smaller grain size (≤ 1.65 μm), as compared to the cs samples (1.93 μm). this suggested that tss has the potential to suppress alumina grain growth when compared to cs method although there was a substantial reduction in grain size for tss3 (0.98 μm) as compared to the cs samples, there were some porosities observed among the grains as shown in figure 4(b). when the sintering holding time was increased from 6 to 10 h, the grain size grew to 1.15 μm and was accompanied by a reduction in porosities (figure 4(c)). this observation shows that the densification was still incomplete at the holding time of 10 h. however, as the holding time was increased to 24 h, a densified and homogeneous microstructure was attained as depicted in figure 4(d). tss7 successfully demonstrated the effectiveness of two-step sintering in suppressing grain growth coupled with improved densification as compared to cs technique. loh et al. [6] have also reported smaller grain size with limited grain growth for two-step sintered alumina ceramics as compared to conventional sintered sample. figure 1: x-ray diffraction patterns of conventional (cs) and two-step sintered alumina samples at different holding time figure 2: the relative density and grain size of conventional and two-step sintered alumina with different sintering holding time on the. key: cs – conventional sintering, tss – two-step sintering anis et al. (2021): international journal of engineering materials and manufacture, 6(4), 299-304 302 figure 3: the grain size as a function of relative density for two-step sintered alumina figure 4: sem micrograph of sintered alumina: (a) cs, (b) tss3, (c) tss5, (d) tss7 densification and mechanical properties of alumina ceramics via two-step sintering with different holding times 303 3.2 vickers hardness and fracture toughness figure 5 shows the vickers hardness and fracture toughness of sintered alumina with different holding time. the twostep sintered samples demonstrated a gradual increased in hardness with the holding time, from 5.12 gpa (2 h) to 6.3 gpa (10 h). this was followed by a steep increase in hardness with the further increment of holding time and reached hardness of about 8.13 gpa for holding time of 24 h. there was a substantial improvement in hardness for all the two-step sintered samples as compared to the conventional sintered sample (4.23 gpa). the vickers hardness of the alumina was found to be strongly dependent on the relative density as shown in figure 6. the fracture toughness of the two-step sintered alumina ceramics was found to vary in the range of 5.5-5.9 mpa.m 1/2 when held at different duration. in general, fracture toughness of the alumina did not change very much for holding times of 8 h and above, indicating that the holding time did not have significantly affected the toughness of the ceramic. nevertheless, the fracture toughness obtained for the tss was higher than that of the cs sample (4.73 mpa.m 1/2 ). loh et al. [6] found that two-step sintering (1550 °c/0 min → 1450 °c/8 h) did not enhance the densification, vickers hardness and fracture toughness of alumina ceramics, despite obtaining a lower grain size as compared to conventional sintered sample. this discrepancy could be associated with the different starting material used as well as the different tss regime employed. figure 5: the vickers hardness and fracture toughness of conventional and two-step sintered alumina with different sintering holding time. key: cs – conventional sintering, tss – two-step sintering figure 6: the relationship between vickers hardness and relative density of sintered alumina anis et al. (2021): international journal of engineering materials and manufacture, 6(4), 299-304 304 4 conclusions based on the current study, the effect of second stage sintering holding time (2 to 24 h) on the densification and mechanical properties of two-step and conventional sintered alumina ceramics were investigated. it was found that two-step sintered alumina (1450 °c/1 min → 1350 °c/24 h) yielded a highly dense sample (>98%), small grain size (1.65 μm), high vickers hardness of 8.13 gpa and fracture toughness of 5.91 mpam1/2. it was also found that the fracture toughness of two-step sintered alumina ceramics was not significantly affected by the sintering holding time duration. a linear relationship between vickers hardness and densification of alumina was also identified. this work revealed that two-step sintering method was beneficial in suppressing alumina grain growth and resulted in improved densification and mechanical properties when compared to conventional sintering method. acknowledgement the authors are grateful to utb and um for providing the facilities to undertake this research. references 1. katti, k. s. (2004). biomaterials in total joint replacement. colloids and surfaces b: biointerfaces, 39(3), 133142. 2. khodaii, j., adibi, h., barazandeh, f., rezaei, m., & sarhan, a. a. d. (2021). investigation of the surface integrity, flexural strength on the grinding of alumina for biomedical applications. precision engineering, 67,110122. 3. dhuban, s. b., ramesh, s., tan, c. y., wong, y. h., johnson alengaram, u., ramesh, s., et al. (2019). sintering behaviour and properties of manganese-doped alumina. ceramics international, 45(6), 7049-7054. 4. abbas, m. k. g., ramesh, s., lee, k. y. s., wong, y. h., ganesan, p., ramesh, s., et al. (2020). effects of sintering additives on the densification and properties of alumina-toughened zirconia ceramic composites. ceramics international, 46(17), 27539-27549. 5. vukšić, m., žmak, i., ćurković, l., & kocjan, a. (2021). spark plasma sintering of dense alumina ceramics from industrial waste scraps. open ceramics, 5, 100076. 6. lóh, n. j., simão, l., jiusti, j., arcaro, s., raupp-pereira, f., de noni, a., et al. (2020). densified alumina obtained by two-step sintering: impact of the microstructure on mechanical properties. ceramics international, 46(8), 12740-12743. 7. li, h., xi, x., ma, j., hua, k., & shui, a. (2017). low-temperature sintering of coarse alumina powder compact with sufficient mechanical strength. ceramics international, 43(6), 5108-5114. 8. yin, z., yuan, j., cheng, y., wang, c., wang, z., & hu, x. (2016). microstructure and mechanical properties of al2o3/ti(c, n) ceramic tool materials by one-step and two-step microwave sintering. materials science and engineering: a, 670, 159-165. 9. chen, i. w.& wang, x. h. (2000). sintering dense nanocrystalline ceramics without final-stage grain growth. nature, 404(6774), 168-171. 10. wang, c.-j., huang, c.-y., & wu, y.-c. (2009). two-step sintering of fine alumina–zirconia ceramics. ceramics international, 35(4), 1467-1472. 11. li, j.& ye, y. (2006). densification and grain growth of al2o3 nanoceramics during pressureless sintering. journal of the american ceramic society, 89(1), 139-143. 12. shetty, d. k., wright, i. g., mincer, p. n., & clauer, a. h. (1985). indentation fracture of wc-co cermets. journal of materials science, 20(5), 1873-1882. international journal of engineering materials and manufacture (2018) 3(1) 63-67 https://doi.org/10.26776/ijemm.03.01.2018.08 umma abdullahi1, md abdul maleque2 and mohammad yeakub ali2 1center for energy research and training ahmadu bello university, zaria kaduna state, 810261 nigeria e-mail: ummaabdullahi@abu.edu.ng 2department of manufacturing and materials engineering, international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: maleque@iium.edu.my reference: umma, a., maleque, m. a. and ali, m. y. (2018). characterization of carbon nanotube reinforced aluminium nanocomposite using field emission scanning electron microscope. international journal of engineering materials and manufacture, 3(1), 63-67. characterization of carbon nanotube reinforced aluminium nanocomposite using field emission scanning electron microscope umma abdullahi, md abdul maleque and mohammad yeakub ali received: 21 march 2018 accepted: 27 march 2018 published: 30 march 2018 publisher: deer hill publications creative commons: cc by 4.0 abstract carbon nanotubes (cnt) is a promising fibrous materials for development of nanocomposite especially aluminium (al) matrix nanocomposites as cnt exhibited extraordinary mechanical properties and high aspect ratios. the dispersion is the main factor for a quality cnt-al nanocomposite that affects the uniformity in mixture leading to the enhanced mechanical and wear behaviour. the present study emphasizes on the characterization of carbon nanotube dispersion by means of field emission scanning electron microscope after synthetization of new nanocomposite. the mixing of the reinforcement and matrix powders was performed in ball mill for 2 hours at 250 rpm. the result shows the homogeneous distribution of cnt in al-matrix. the morphological characterization under fesem provides insight features of cnt-al nano-composite with the ball milling parameter on the sintering. keywords: carbon nanotube; aluminium powder; dispersion; characterisation; fesem 1 introduction aluminium (al) matrix composite can be used for many applications including aviation, aircraft and automotive industries due to the lower density as many components require weight reduction for less fuel consumption which in turn can save the environment. advancement of the research in the carbon nanotube was embarked after finding of carbon nanotubes (cnts) by rolling a graphene sheets [1]. a multiwalled carbon nanotube (mwcnt) is consisting of multiple rolled layers or concentric tubes of carbon or graphite material. past research revealed that mwcnts have extraordinary properties compared to carbon fibres, such as rigidity is approximately 1000 gpa and thermal conductivity of up to 6000 w mk [2]. different processing routes are available for development of carbon nanotube reinforced metal matrix composites (cnt-mmc). powder metallurgy (pm) is cost-effective, robust and energy saving process. hot deformation behavior of a 2.0 wt% cnt/2024al nanocomposite was studied via high-temperature compression over a temperature and strain rate range of 200–400 °c and 0.001–0.1 s−1, respectively [3]. they found that microstructural examinations at a high strain rate, within the upper and lower temperature limits, revealed the occurrence of second-phase particle shearing, refinement, re-precipitation, and re-orientation. mahmood et al. [4] have studied the time-dependent formulation of slightly weakened interface (swi) model for an embedded carbon nanotube (cnt) in a polymer matrix with the aim to predict viscoelastic properties of cnt/polymer nanocomposites. in generally, the viscoelastic properties of cnt/polymer are lower than cnt-metal nanocomposites. ball milling is a technique to mix up the reinforcement and matrix materials before it goes through powder metallurgy process for nanocomposite development. in order to achieve targeted properties of nanocomposite, different combination of materials is formulated [5], [6], [7]. thermal conductivity, mechanical and tribological property enhance significantly with different graphite shape. it is very important to successfully dispersed cnts with the matrix material to attain desirable properties [6], [7]. previous works done on the ball milling of cnt and aluminium abdullahi, maleque and ali (2018): international journal of engineering materials and manufacture, 3(1), 63-67 64 mixtures with different speed and time for dispersion and homogenization of the cnt and aluminium. the effect of process variable such as milling time, control agent and cnt wt % on the morphology of alloy powder was investigated by esawi and borady [8]. another study was done by others on the cnt particle size and milling time and they concluded that the particle size and morphology changed significantly due to the parameter [9]. they also found that the addition of methanol as process control agent affect the mechanically alloyed powder mixture characteristic. however, no information is available in literature on the characterisation of cnt dispersion with wide range of cnt into al matrix in terms of mapping and line analysis. therefore, this research studied and characterised carbon nanotube dispersion in ball milled cnt-al nano-composite which was performed in a planetary ball mill equipment using fesem. 2 features of fesem a field emission scanning electron microscope (fesem) is microscope that works with electrons (particles with a negative charge) instead of light. these electrons are liberated by a field emission source having the smallest probe diameters (~ 1.2 nm) and with higher resolution. a fesem is used to visualize very small topographic details on the surface or entire or fractioned objects. researchers in materials, biology, chemistry and physics apply this technique to observe structures that may be as small as 1 nanometer. the main advantage of the fesem is that high resolution imaging can be performed with very low accelerating voltages [10]. by using fesem, topography, morphology, composition, mapping, crystallographic information, higher lateral resolution, onset field strength and investigation of the long-term stability can be measured. the fesem can be classified as a high vacuum instrument (less than 1x10-7 pa or 10-10 mbar). the vacuum allows electron movement along the column without scattering and helps to prevent discharges inside the instrument. under vacuum, electrons generated by a field emission source (electron gun) are accelerated in a field gradient. the electron beam passes through electromagnetic lenses, focusing onto the specimen. as a result of the electrons bombardment, different types of electrons or signals (such as secondary electrons (se), backscattered electrons (bse), ae, x-rays, light) are emitted from the specimen. the image is formed based on the detection and intensity of the secondary electrons. the applications of fesem are semiconductor device cross section analyses for gate widths, gate oxides, film thicknesses, and construction details; advanced coating thickness and structure uniformity determination and small contamination feature geometry and elemental composition measurement [11]. 3 materials and method the matrix material in this investigation was al powder (99.7% purity) and the particle size was 78 µm with the spherical shape. the reinforced material was multi-walled carbon nanotubes (mwcnts) with a nominal diameter of 10nm, length of 5-15µm and surface area of 40-300 m2g-1. the morphology of al powder and mwcnt was investigated using fesem and shown in figure 1. there are four formulations with, 1, 1.5, 2 and 2.5 wt% cnt for development of cnt-al nanocomposite. initially, cnt-al powders were mixed by hand shaking inside the tube using 10 mm diameter stainless steel ball for 10-15 mins. then, this hand shacked mixture was placed in a stainless steel jars with the same ball. the ball milling was performed using high energy planetary ball mill equipment at a constant speed of 250 rpm for 2 hours in presence of argon gas.the sample was compacted at a pressure of 2500 psi and sintered using hot isostatic press (hip) machine (hp630) at 500oc and the argon gas was supplied at the pressure of 2500psi for 60mins to control the atmosphere in the process. the cnts dispersion was analysed using fesem. (a) (b) figure1: photo-micrograph of (a) aluminium powder and (b) cnt [3]. characterization of carbon nanotube reinforced aluminium nano-composite using field emission scanning electron microscope 65 4 results and discussions from the fesem image at higher magnification, the cnt was observed to be a long and thin tube like structure and appeared as individual molecules as expected. figure 2 to 5 shows that the particles are plastically deformed due to effect of ball milling parameters resulting a typical flake structures of the nanocomposite. with the increasing the milling time, the flake structure nanocomposite start changing to the sandwich structure up to the first few minutes of the milling time followed by welding of the particles together, and finally turns to the rough surface with course particle size. this is happen due to collision during grinding of the particles. the progressive welding of the particles continued due to effect of the milling time. fig. 3 shows the microstructure of 1.5 wt% cnt at 250 rpm for different ball milling time. from the figure, it can be seen that both reinforcement and matrix particles are flattened because of the collision during ball milling. spherical shape of cnt and al mixtures was observed with increasing milling time. similar observation was made from fig. 2 and 4 for 1 and 2 wt% cnt respectively; while for 2.5 wt% some cluster was observed on the morphology (fig. 5). however, similar result was observed by others but with different and higher milling time [6]. in terms of homogenization 1.5 wt% cnt was assume to have better and uniform cnt dispersion and it was attained in a short time at 250 rpm milling speed. higher cnt percentage into al matrix demanded more milling time to homogeneously dispersed the mixture compared to when using a lower cnt percentage mixture. uniform and homogeneously dispersed cnt has a significant effect in a light weight cnt-al nanocomposite. hence, the dispersion and homogenous distribution of cnt in al can significantly affected by the ball milling time and preliminary mixing of the powders. it can be said that the appropriate amount of bonding agent like process control agent and hand mixing of cnt and al powder before ball milling are the main contributing factors toward the uniform dispersion and distribution of cnt powder in al matrix. (a) (b) (c) figure 2: microstructure of 1 wt% of cnt at 250 rpm for different ball milling time. (a) (b) (c) figure 3: microstructure of 1.5 wt% of cnt at 250 rpm for different ball milling time. 1 wt%, 1hr 1 wt%, 2hr 1 wt%, 3hr 1.5 wt%, 1hr 1.5 wt%, 2hr 1.5 wt%, 3hr abdullahi, maleque and ali (2018): international journal of engineering materials and manufacture, 3(1), 63-67 66 (a) (b) (c) figure 4: microstructure and morphology of 2 wt% cnt at 250 rpm for different ball milling time (a) (b) (c) figure 3: microstructure of 2.5 wt% of cnt at 250 rpm for different ball milling time. 5 conclusion the morphological characterization of the developed nanocomposite using different cnt weight percentage are presented and compared while the choice of the best cnt percentage in the development of cnt-al nanocomposite was made based on the analysis of fesem and the results showed homogeneous dispersion and distribution of cnts in aluminium matrix. ball milling time during the mixing of the powder and controlled atmosphere with argon in the furnace play important role on the sintered product of the cnt-al nano-composite. acknowledgements the authors would like to express their thanks to the department of manufacturing and materials engineering, iium for the support to carry out this research work. references [1] iijima, s. (1991). helical microtubules of graphitic carbon. nature, 354(6348), 56-58. [2] bakshi, s. r., & agarwal, a. (2011). an analysis of the factors affecting strengthening in carbon nanotube reinforced aluminum composites. carbon, 49(2), 533-544. [3] f. mokdad, d.l. chen, z.y. liu, d.r. ni, b.l. xiao, z.y. ma, hot deformation and activation energy of a cntreinforced aluminum matrix nanocomposite, materials science and engineering: a, volume 695, 2017, 322-331. [4] mahmood m. shokrieh, rahmatollah ghajar, ali r. shajari, the effect of time-dependent slightly weakened interface on the viscoelastic properties of cnt/polymer nanocomposites, composite structures, 146, 2016, 122131. [5] maleque, m. a., abdullah,u., i i yaacob and ali, m y. (2016). characterization of ball-milled carbon nanotube dispersed aluminium mixed powders. iop conf. series: materials science and engineering, 123, 1-6. [6] camargo, p. h. c., satyanarayana, k. g., & wypych, f. (2009). nanocomposites: synthesis, structure, properties and new application opportunities. materials research, 12(1), 1-39. [7] esawi, a., morsi, k., sayed, a., taher, m., & lanka, s. (2010). effect of carbon nanotube (cnt) content on the mechanical properties of cnt-reinforced aluminium composites. composites science and technology, 70(16), 2237-2241. 2 wt%, 1hr 2 wt%, 2hr 2 wt%, 3hr 2.5 wt%, 1hr 2.5 wt%, 2hr 2.5 wt%, 3hr characterization of carbon nanotube reinforced aluminium nano-composite using field emission scanning electron microscope 67 [8] esawi, a. m., & el borady, m. a. (2008). carbon nanotube-reinforced aluminium strips. composites science and technology, 68(2), 486-492. [9] maleque, m a., umma, a. and n omar p. (2013). wear mechanisms map of cnt-al nano-composite. procedia engineering, 12, 247-253. [10] https://www.mee-inc.com/laboratory-expertise/field-emission-sem-fesem/ [11] http://photometrics.net/field-emission-scanning-electron-microscopy-fesem/ [12] umma, a., maleque, m a., and mohammad y. a., (2012). carbon nano tube reinforced aluminium matrix nano-composite: a critical review. australian journal of basic and applied sciences, 6 (12), 69-75. http://photometrics.net/fieldinternational journal of engineering materials and manufacture (2021) 6(4) 305-311 https://doi.org/10.26776/ijemm.06.04.2021.06 a. a. adebisi, a. a. 1,2 , mojisola, t. 2 , shehu, u 1 , adam, s. m. 2 and abdulaziz, y 1 1 department of metallurgical and materials engineering, ahmadu bello university, zaria, nigeria 2 metallurgical and materials engineering department, air force institute of technology, kaduna, nigeria e-mail: aaadebisi@abu.edu.ng a.adebisi@afit.edu.ng references: adebisi et al. (2021). in-situ synthesis and property evaluation of high-density polyethylene reinforced groundnut shell particulate composite. international journal of engineering materials and manufacture, 6(4), 305-311. in-situ synthesis and property evaluation of high-density polyethylene reinforced groundnut shell particulate composite adetayo abdulmumin adebisi, tajudeen mojisola, umar shehu, muhammed sani adam and yusuf abdulaziz received: 09 march 2021 accepted: 24 july 2021 published:01 october 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract in-situ synthesis of high-density polyethylene (hdpe) reinforced groundnut shell particulate (gsp) composite with treated gsp within the range of 10-30 wt% at 10 wt% has been achieved. the adopted technique used in the production of the composite is melt mixing and compounding using two roll mills with a compression moulding machine. properties such as hardness, tensile strength, impact energy and water absorption analysis were examined. the result revealed that addition of gsp increases the hardness value from 22.3 to 87 hv. however, the tensile strength progressively decreased as the gsp increases in the hdpe. this trend arises due to the interaction between neighbouring reinforced particulate which appears to influence the matrix flow, thereby inducing embrittlement of the polymer matrix. it was also observed that water absorption rate steadily increased with an increase in the exposure time and the absorbed amount of water increases by increasing the wt% of the gsp. analysing the obtained results, it was concluded that there were improvements in the hardness, tensile strength, impact energy and water absorption properties of the hdpe-gsp polymer composite when compared to unreinforced hdpe. on these premises, gsp was found as a promising reinforcement which can positively influence the hdpe properties of modern composites. keywords: high density polyethylene (hdpe), groundnut shell particulate (gsp), melt mixing, compounding, compression moulding machine. 1 introduction in recent years, natural fibre reinforced polymers have started emerging as new eco-friendly polymeric composite materials with superior engineering properties such as low density, acceptable specific strength and specific stiffness, reduced tool wear and non-abrasiveness [1]. they are also commercially cost effective, environmentally friendly, reduce dependence on non-renewable sources, reduce pollutant and greenhouse gas emissions and offer enhanced energy recovery. the easy availability and presence of cellulose imparts good mechanical properties to natural fibres which makes it viable for promoting natural fibre reinforced polymer composites. the presence of cellulose makes natural fibres hydrophilic, however, the adhesion with hydrophobic polymer matrix reduces load transfer from matrix to fibre in the composite thereby limiting the mechanical properties [2]. this limitation can be overcome by improving the fibre-matrix interfacial adhesion through surface modification of the natural fibre through chemical or physical treatment, use of coupling agent and chemically functionalized matrix. these naturally occurring fibres have been extensively used as reinforcements in polymer matrices as compared to the non-degradable synthetic fibres such as carbon, glass or aramid. they have shown to be invaluable when used as reinforcing filler in the polymer matrix. several natural fibres have been investigated and they include coir fibre [3], wood fibre [4], rice straw fibre [5], sisal fibre [6], hemp fibre [7], kenaf fibre [8] and chitosan [9]. groundnut shell is a waste product obtained after the removal of groundnut seed from its pod, and there has not been substantial demand for the utilization of groundnut shell for economic and commercial purpose. it is one of such natural agro waste filler with potential to be used as reinforcement as it contains cellulose, hemicellulose and lignin. it is a valuable product in composite production process due to its high availability in northern nigeria and scarce interest in other in-situ synthesis and property evaluation of high-density polyethylene reinforced groundnut shell particulate composite 306 industrial sectors [10]. on the other hand, high density polyethylene (hdpe) is one of the important grades of polyethylene (pe) that exhibits excellent properties such as chemical stability barrier, good thermal resistance and mechanical strength. these properties make hdpe a versatile material in the manufacture of many products and packaging such as milk jugs, detergent bottles, margarine tubes, and garbage containers [11]. in their study, jacob et al., [12] reported the dynamic mechanical characterization of groundnut shell powder filled recycled high-density polyethylene composite. the experiments were conducted using treated and untreated groundnut shell powder. dynamic mechanical properties such as storage modulus, loss modulus and damping parameter were found to improve with the incorporation of treated groundnut shell powder. the inherent properties of the groundnut shell powder have made it a good reinforcing material in the development of composite. similarly, olaitan et al., [13] investigated the comparative assessment of mechanical properties of groundnut shell and rice husk reinforced epoxy composite. this investigation considered two different reinforcement groundnut shell and rice husk. after comparing the mechanical properties of the two reinforcements, it was revealed that groundnut shell epoxy composite displayed higher mechanical properties as compared to the rice husk epoxy composite. musa et al., [14] studied on the mechanical and morphological properties of high-density polyethylene (hdpe) leather waste composites. the study shows that without additives, hdpe/chrome tanned composites had higher modulus with lower tensile strength and impact strength. moreover, souza et al., [15] investigated on the mechanical properties of hdpe/textile fibres composites. the investigation result shows that the addition of modified fibres from industrial residue to hdpe improve the tensile strength and modulus which means there is an improvement in the mechanical property. based on the studies highlighted, groundnut shell and hdpe have potential to be processed for use as composite material. however, there is limited or no information available in the literatures on the study. therefore, this study aims to investigate the mechanical and water absorption properties of high-density polyethylene reinforced groundnut shell particulate composite using compression moulding technique. 2 materials and methods 2.1 materials the hdpe was obtained from the department of metallurgical and materials engineering, ahmadu bello university, zaria and the groundnut shells were locally sourced from dawanau market in kano state, nigeria. the shells were washed thoroughly to remove dirt and dried to enable easy crushing and grinding into smaller sizes using shredding machine and a sieve of size less than <0.3mm (300 micrometres) was used. the sieved groundnut shell was then immersed and treated in 5 % naoh for 1, 2, 3 hours with continuous stirring after which the solution was decanted off, washed several times with distilled water until the solution becomes neutral. the ground nut shell was then dried in an oven at a temperature of 105 degrees for 6 hours. 2.2 method 2.2.1 composite preparation the mould used for the preparation of the composite is an iron mould with a dimension of 100 x 100 x 30 mm. an equivalent volume of hdpe was weighed using analytical weighing balance for each sample size. the weight percentage of 0-30 (0, 10, 20, and 30) wt % of groundnut shell were calculated from the weight of the control sample of hdpe, weighed and tight up in different nylons for production of the composite. 2.2.2 compounding and mixing to produce the composite, the ratio of the hdpe to the groundnut shell particles were measured 90/10, 80/20, and 70/30 the measurement was carried out using an electronic digital weighing balance. the two-roll mill machine was warmed up for about one hour (1hr) at a temperature of 150 0 c. the materials were compounded via melt mixing and compression moulding using two roll mill and a compression moulding machine at a temperature of 140 0 c and a pressure of 5 psi to obtain a homogeneous mixture. the weight fraction of the reinforcement was varied from 0-30 (0, 10, 20, and 30). the samples were cooled, after the composite was removed from the mould. the procedure was repeated for all composition of the filler (particle). the compression mould process was carried out at the nilest samara zaria, kaduna state, nigeria. 2.3 mechanical property test 2.3.1 hardness test the micro indentation measurements were carried out at room temperature using shimadzu hmv-1, japan micro hardness tester. the test measures the penetration of a specified indenter into the material with a load of 0.3kgf that has a maximum hardness value of 100hv and a minimum hardness value of 010hv. it consists of an indenter, a graduated circular tube and a flat surface which the sample to be tested was mounted. the sample was placed on the flat surface and a load was applied on the surface of the specimen to obtain the hardness value. the measurements were performed in accordance with astm standard e384 for micro-indentation hardness of materials [22]. the micro hardness was computed at five different locations for each value of load for the prepared samples where the average vickers micro hardness number was calculated and recorded. adebisi et al. (2021): international journal of engineering materials and manufacture, 6(4), 305-311 307 2.3.2 tensile strength test the tensile testing machine used is the tensometer type w (with flexural fixture), monsanto tensometer, uk. the testing of the samples was conducted at the department of metallurgical and materials engineering, ahmadu bello university, zaria, kaduna state, nigeria in accordance with astm d638 standards. the samples were machined to dumbbell shape and then placed in the universal tensile testing machine. the test was determined using tensile machine by gripping the ends of a suitable prepared standard test sample, and then applying a continually increasing uniaxial load until the sample fractured. the tensile loads together with the corresponding extensions were recorded on the graph sheet for evaluation. 2.3.3 impact energy test impact strength of a material is the capacity to absorb energy under shock or impact load. the impact test was conducted on the prepared gsp-hdpe composite on the treated samples using the charpy impact testing machine. the composite samples for the impact test were prepared according to astm d-256 with the dimensions of 55 mm (length) x 10 mm (width) x 10 mm (height) and also provided the v-notch at the middle of the samples. the pendulum was raised to the test height and held there. the sample was mounted in the machine and the door of the machine was closed. the pointer for reading the impact energy value on the calibrated scale was adjusted to zero before the pendulum was released by means of a handle on the door of the machine. the pendulum falls from the height, breaking the sample and hitting the pointer to the test energy value. this process was repeated for all the samples, till all the impact test value for all the different composition was recorded and the average value was recorded. 2.4 water absorption test water absorption test was used to determine the water absorption capacity of the synthesized composite under some specified conditions. the test was carried out by immersion of the samples in water bath at room temperature for a time duration. the samples were cut to dimensions 20 x 20 mm, the initial weight of the samples was taken with aid of an electronic digital weighing balance with tolerance of 0.001 g. then each of the samples were immersed in a beaker containing water and the new weight of the samples was recorded. the samples were immersed in water for a duration of 1 – 3 hrs, after immersion the surface of the specimen were cleaned dry and weighed immediately to measure their weight. the initial weight of samples is taken as w1 and after the sample is removed from the water is taken as w2. the percentage water absorption was obtained from the relationship in equation 1. 3 results and discussions 3.1 groundnut shell and developed hdpe-gsp composite fig. 1(a-c) show the groundnut shell in the as received, untreated and treated conditions. the untreated groundnut shell is bright compared to the treated groundnut which is dark due to the removal of some elements during the treatment process. fig. 1(d) shows the developed hdpe-gsp composite before conducting the various testing to ascertain the properties analysis. % 𝑀𝑜𝑖𝑠𝑡𝑢𝑟𝑒 𝐴𝑏𝑠𝑜𝑟𝑏𝑡𝑖𝑜𝑛 = 𝑊2 − 𝑊1 𝑊1 𝑥100 (1) figure 1: groundnut shell (a) as received, (b) untreated, (c) treated and (d) sectioned portion of developed hdpegsp composite 3.2 mechanical properties analysis 3.2.1 hardness test figure 2 explains the comparative analysis of the hdpe (control sample) and the gsp-hdpe composite subjected to alkaline treatment at various time intervals ranging from 1 to 3 hours. the unreinforced hdpe shows the lowest hardness value of 22.3 hv. the gsp-hdpe reveals a progressive increase in hardness value as the wt% of gsp increases from 10 wt% to 30 wt% for 1 hr alkaline treatment. however, the hardness value for the 2 hrs and 3 hrs treated gsp-hdpe composite exhibited similar trend where there is a drop in hardness value from 71.73 to 54.2 hv and 42.87 to 34 hv for the 20 wt% gsp-hdpe composite. in-situ synthesis and property evaluation of high-density polyethylene reinforced groundnut shell particulate composite 308 the 30 wt% gsp-hdpe composite exhibited a remarkable rise in the hardness value for both 2 hrs and 3 hrs treated composite from 54.2 to 76.13 hv and 34 to 67.9 hv, respectively. the reason for the drop in hardness value for the 20 wt% gsp-hdpe composite maybe ascribed to the poor interfacial bonding or poor adhesion of the reinforced gsp and hdpe. the increase in hardness is attributed to the strengthening effect of the gsp incorporated into the hdpe matrix. 3.2.2 tensile test the tensile strength of the gsp-hdpe composite was found to decrease progressively as the percentage of gsp increased from 10 wt% to 30 wt% as shown in figure 3. however, the 10 wt% reinforced gsp-hdpe treated for 3 hrs showed better tensile strength when compared to 20 and 30 wt% treated composites. the increase in wt% of the gsp is expected to increase the tensile strength but this trend may have resulted due to poor wettability and adhesion with uneven dispersion between the gsp and hdpe. although, similar behaviour was previously reported in the use of coir fibre as filler reinforcement [16]. 3.2.3 impact energy test the impact strength of treated gsp-hdpe composite attained maximum at 20 wt% gsp treated for 1 hr as shown in figure 4. however, the 10 wt% and 30 wt% treated gsp-hdpe composite recorded poor impact strength for all time conditions considered. the impact strength of the composite reduced after 20 wt% may be due to the reduction of elasticity of the material due to gsp addition thereby reducing the deformability of the hdpe. moreover, considerable amount of energy absorption takes place through particle pull out process but after alkali treatment a strong mechanical interlocking develops between the gsp and hdpe and particle pull out is reduced which in turn decreases the impact strength. figure 2: effect of wt% gsp and alkaline treatment on hardness value of gsp-hdpe composites 22.3 63.4 67.57 87 71.73 54.2 76.13 42.87 34 67.9 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 h a r d n e s s ( h v ) wt % reinforcement (gsp) control hdpe 1 hr alkaline treatment 2 hrs alkaline treatment 3 hrs alkaline treatment adebisi et al. (2021): international journal of engineering materials and manufacture, 6(4), 305-311 309 figure 3: effect of wt% gsp and alkaline treatment on tensile strength of gsp-hdpe composites figure 4: effect of wt% gsp and alkaline treatment on impact energy of gsp-hdpe composites 3.3 water absorption the result obtained from water absorption test is plotted against the wt% of gsp as shown in figure 5. the water absorption rate attained maximum with 30 wt% gsp-hdpe treated for 2 hrs. when compared to the hdpe sample, the absorption value increased from 0.653% to 9.579%. similar trend of result was achieved by munoz and garcia (17) in their study. the increase in water absorption upon addition of wt% gsp is as a result of the hydrophilic nature of groundnut shell which absorbs water, thereby creating room inside the composite resulting in micro-cracks that develop between the interface of the particle and the matrix giving rise to higher water absorption. 21.55 13.17 12.36 11.12 13.45 12.7 11.99 14.04 11.74 11.86 0 5 10 15 20 25 0 10 20 30 t e n s i l e s t r e n g t h ( n / m m 2 ) wt % reinforcement (gsp) control hdpe 1 hr alkaline treatment 2 hrs alkaline treatment 3 hrs alkaline treatment 1.43 0.5 1.45 0.57 0.8 1.07 5 0.6 0.4 1.37 0.63 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0 10 20 30 i m p a c t e n e r g y ( j ) wt % reinforcement (gsp) control hdpe 1 hr alkaline treatment 2 hrs alkaline treatment 3 hrs alkaline treatment in-situ synthesis and property evaluation of high-density polyethylene reinforced groundnut shell particulate composite 310 figure 5: effect of wt% gsp and alkaline treatment on water absorption of gsp-hdpe composites 4 conclusions in this study, effects of wt% gsp and alkaline treatment on the mechanical properties and water absorption behaviour of gsp-hdpe composite were reported. it was found that both the wt% gsp and alkaline treatment influences the properties of the composite. the following conclusion were drawn from the study; 1. the gsp-hdpe composite was successfully developed using the melt mixing and compression moulding technique. 2. the hardness value of the gsp-hdpe composite shows a steady rise as the wt% gsp increases from 10-30 wt% for the 1 hr treated gsp. however, the 2 hrs and 3 hrs treated gsp experiences a decline for the 20 wt% gsp. the 30 wt% gsp attained the maximum for all treatment time with 87 hv as the highest value. 3. the tensile strength of the composite decreases progressively as the wt% of the gsp increases from 10-30 wt%. although, the 10 wt% reinforced gsp-hdpe treated for 3 hrs attained the maximum value at 14.04 n/mm 2 . 4. gsp-hdpe composite achieved optimum impact energy at 20 wt% gsp treated for 1 hr. however, the 10 and 30 wt% recorded poor impact strength due to the reduction in the elasticity of the hdpe as a result of gsp addition. 5. water absorption rate attained high value at 30 wt% gsp-hdpe composite for all treatment time. however, the composite treated for 2 hrs achieved the maximum water absorption rate. 6. it is concluded that the wt% and alkaline treatment play a major role in the mechanical and water absorption properties of gsp-hdpe composite. however, an optimization analysis study will be required to fully achieve the best wt% composite of gsp and alkaline treatment time. acknowledgement the authors acknowledge the support received from the department of metallurgical and materials engineering, ahmadu bello university, zaria throughout the conduct of the research. sincere appreciations are also extended to the technical team in the departmental workshop where the experimental studies reported here were conducted. references 1. mohanty, a. k., misra, m. & drzal, l. t. (2002). sustainable biocomposites from renewable resources: opportunities and challenges in the green material world. journal of polymers and the environment, 10, 19-26. 2. singh, a. a., biswas, k., priyanka, d., & palsule, s. (2014). coconut fibre reinforced high density polyethylene composite by compatibilizer process. applied polymer composite, 2(3), 167. 3. adeniyi, a. g., onifade, d. v., ighalo, j. o. & adeoye, a. s. (2019). a review of coir fiber reinforced polymer composites. composites part b: engineering, 176, 107305. 4. teuber, l., militz, h. and krause, a. (2016) processing of wood plastic composites: the influence of feeding rate method and polymer melt rate on particle degradation. journal of applied polymer science, 133, 43231. 5. ismail, m. r., yassene, a. m. & afify, m. s. (2011). mechanical properties of rice straw fiber-reinforced polymer composites. fibers and composites, 12(5), 648-656. 0.653 1.574 1.058 8.834 3.476 1.094 9.579 0.385 1.532 8.779 0 2 4 6 8 10 12 0 10 20 30 w a t e r a b s o r p t i o n ( % ) wt % reinforcement (gsp) control hdpe 1 hr alkaline treatment 2 hrs alkaline treatment 3 hrs alkaline treatment adebisi et al. (2021): international journal of engineering materials and manufacture, 6(4), 305-311 311 6. favano, s. l., ganzerli, t. a., de carvalho neto, a. g. v., da silva, o. r. r. f. & radovanovic, e. (2010). chemical, morphological and mechanical analysis of sisal fiber-reinforced recycled high-density polyethylene composites. express polymer letters, 4, 465-473. 7. fang, h., zhang, y., deng, j. & rodrigue, d. (2013). effect of fiber treatment on the water absorption and mechanical properties of hemp fiber/polyethylene composite. journal of applied polymer science, 127, 942949. 8. bledzki, a. k., franciszczak, p., osman, z. & elbadawi, m. (2015) polypropylene biocomposites reinforced with softwood, abaca, jute, and kenaf fibers. industrial crops and products, 70, 91-99. 9. arumugam, s., kandasamy, j., hameed sultan, m. t., md shah, a. u. & nur azrie safri, s. (2021). investigations on fatigue analysis and biomimetic mineralization of glass fiber/sisal fiber/chitosan reinforced hybrid polymer sandwich composites. journal of materials research and technology, 10, 512-525. 10. adeosun, s. o., taiwo, o., akpan, e. i., gbenebor, o. p., gbagba, s., olaleye, s. (2016). mechanical characteristics of groundnut shell particle reinforced polactide nano fibre. matéria (rio de janeiro), 21(2), 482491. 11. klyosov, a. a (2007). wood-plastic composite. john wiley and sons inc., new jersey, us. 12. jacob, j., mamza, p. a. p, ahmad, a. s. & yaro, s. a. (2019). mechanical and dynamic mechanical characteristics of groundnut shell powder filled recycled high-density polyethylene composites. science world journal, 14(1), 92-97. 13. olaitan, a. j., terhemen, a. e., king, g. d. & oluwatoyin, o. r. (2017). comparative assessment of mechanical properties of groundnut shell and ruce husk reinforced epoxy composite. american journal of mechanical engineering, 5(3), 76-86. 14. musa, e. t., hamza, a., ahmad, a. s., ishiuku, u. s. (2017). investigation on the mechanical and morphological properties of high-density polyethylene (hdpe) leather waste composites. iors journal of applied chemistry, 10(1), 48-58. 15. souza, p. s., rodrigues, e. f., preta, j. m. c., goulart, s. a. s., mulinari, d. r. (2011). mechanical properties of hdpe/textile fibers composites. procedia engineering, 10, 2040-2045. 16. ng, y. r., shahid, s. n. a. m. & nordin, n. i. a. a. (2017). the effect of alkali treatment on tensile properties of coir/polypropylene biocomposites. iop conf. series: materials science and engineering, 368, 012048. 17. munoz, e. & garcia-manrique, (2015). water absorption behaviour and its effect on the mechanical properties of flax fibre reinforced bioepoxy composite. international journal of polymer science, 10, 390275. international journal of engineering materials and manufacture (2017) 2(4) 86-93 https://doi.org/10.26776/ijemm.02.04.2017.02 m. eshtayeh deera metals industries technical support department p.o. box 811, amman 11511, jordan e-mail: eshteyah_m@yahoo.com m. hrairi1 and m.s.i s. dawood department of mechanical engineering international islamic university malaysia p.o. box 10, 50728, kuala lumpur, malaysia 1e-mail: meftah@iium.edu.my e-mail: sultan@iium.edu.my reference: eshtayeh, m., hrairi, m., and shaik dawood, m. s. i. (2017). numerical investigation of springback in mechanical clinching process. international journal of engineering materials and manufacture, 2(4), 86-93. numerical investigation of springback in mechanical clinching process mohanna eshtayeh, meftah hrairi, and m.s.i shaik dawood received: 09 october 2017 accepted: 18 november 2017 published: 10 december 2017 publisher: deer hill publications © 2017 the author(s) creative commons: cc by 4.0 abstract in this work, a numerical investigation was conducted to study the springback phenomena in the mechanical clinching process. the springback values were calculated using finite element simulations and it was found that these values depend strongly on the strength of the materials. a taguchi optimization method was used to determine the optimal parameters affecting springback. however, in the case of materials with low tensile strength, determining parameters affecting springback becomes difficult. implicit and explicit simulations of clinching joints using the springback analysis show that the distance between the joint sheets becomes almost zero after stress recovery. keywords: clinching, springback, finite element, simulation, optimization, taguchi method 1 introduction springback is classified as the main defect during the u-channel fabrication process [1]. springback is generally defined as the dimensional change generated in the part, which occurs due to elastic recovery after the tool is released. in general, springback in metal forming is affected by different factors such as, the mechanical properties (yield strength, elastic modulus) of the metals, tools geometry, and the applied load. in addition, a higher ratio of yield strength and the considerable elastic recovery during unloading lead to springback [2]. furthermore, the amount of elastic recovery can be affected by the tool shape and dimensions, contact friction condition, material properties, and thickness. in the manufacturing industry, it is still a challenge to predict the final shape of the required part after springback, while the final design of the tool is an important issue in order to compensate for the springback effect. in general, high strength materials have greater springback values during cold forming processes such as u-channel fabrication process, flange drawing process and clinching methods. the finite element method was used to evaluate the springback occurring in the sheet metal flange drawing methods by the control of the punch corner radius, die corner radius, blank holder force, and the lubrication [3]. a numerical investigation was conducted to improve the accuracy of the cold stamping process and to accommodate springback [4]. springback in sheet metals with a hole on the bending area was investigated using experiments and finite element analysis [5]. the springback introduced with the clinching process showed that springback is a dimensional change between the two sheets forming the clinched joint, after the pressure of the punch and blank holder is released [6]. in addition, the same study showed that the difference between the strain levels produced by the elastic recovery affect the springback values between the two formed sheets. the accuracy of the springback calculation depends on the yield criterion, the hardening behaviour of the sheets after forming the clinched joint, the elastic properties of the two sheets, and the friction properties between the sheets used. a number of numerical experiments was conducted showing the importance of the springback calculations during the forming of the clinched joint [6]. in this paper, a numerical investigation, using mailto:eshteyah_m@yahoo.com mailto:meftah@iium.edu.my numerical investigation of springback in mechanical clinching process 87 the commercial finite element package ls-dyna, was conducted by performing a procedure to measure the distance between the two sheets after the creation of clinched joints. 2 methodology 2.1 simulation of the clinching process the experiments were designed using the finite element simulation for the clinching process using springback analysis. implicit and explicit simulation models were used for the purpose of investigation. a contact was defined between the sheets (deformable) and tools (rigid body) during the clinching forming process. the two blanks to be clinched were simulated using four node quadratic elements. in addition, friction between the two sheets, blank holder, punch, and die has been utilized using coulomb’s law. the most important input data to establish the fe model are; the material properties, the boundary conditions, the displacement versus time for the punch and blank holder movement, stress versus strain data, strain hardening characteristics of the materials, the definition of the contact model, and the absence of residual stresses in the two sheets before loading starts. in ls-dyna, the updated lagrange formulation was used due to the large strain and displacement analyses in the clinching forming process. springback can be calculated in various terms; radius ratio of parts’ angles after springback, vertical displacement at the end of the process, etc. springback analyses by ls-dyna can be achieved with the interface springback card that allows convenient export of the deformed geometry, stresses, and effective plastic strain from one analysis run to another. the interface card was used to create a dynain file with stress and strain whereas deformed node locations were given. this complicated nonlinear elastic-plastic forming simulation was performed in a relatively shorter time period using a simplified 2d-axisymetric model instead of using a costly 3d model in ls-dyna. with this feature, various configurations could be modelled and simulated successively, thus saving time and effort. figure 1 shows the equivalent von mises stresses and the total equivalent plastic strain obtained using fe simulation of the clinching process while figure 2 shows the von mises stress in the upper sheet (steel) and lower sheet (aluminium). the development of stress originates from the contact interface between the punch and upper steel sheet. as the joining force progresses within the time increment, the punch forces the sheets to deform plastically, reducing their initial thickness. with progressing deformation of both sheets their strain hardening ability increases, causing the increase of punch load. hence, the development of stress starts to progress along the bottom thickness of the upper steel sheet (1.05 gpa) and with a lesser degree in the lower aluminium sheet (0.8283 gpa) as can be seen in figure 1b and figure 2. (a) von mises stress for upper sheet (steel) 1.05 gpa (b) von mises stress for lower sheet (aluminum) 0.8283 gpa figure 2: von mises stress for upper and lower sheets (steel, aluminum) shows that higher yield strength material has higher von mises values (a) the effective strain fringe level before springback analysis (b) the von mises stresses fringe level before springback analysis figure 1: the equivalent von mises stresses and the total equivalent plastic strain obtained from ls-dyna (2d axis symmetric clinching forming process) eshtayeh et al., (2017): international journal of engineering materials and manufacture, 2(4), 86-93 88 as mentioned earlier, springback is a function of the material properties. the larger the strength, the greater the springback will be after forming. in addition, the maximum equivalent plastic strain distribution has a smaller value with higher yield strength. figure 3 shows the equivalent plastic strain in the clinching joint for the upper sheet (steel) and the lower sheet (aluminium). the values show that the equivalent plastic strain after forming in the upper sheet (steel) is smaller than the lower sheet (aluminium), 1.343 and 2.899, respectively. another perspective shows that the equivalent plastic strain has a higher value when there is an increase in the sheet thickness. (a) equivalent plastic strain in upper sheet (steel with higher strength than lower sheet) (b) equivalent plastic strain in lower sheet (aluminum with lower strength than upper steel sheet) figure 3: the equivalent plastic strain in upper and lower sheets in the clinching joints with different yield strength once the punch moves downward in contact with the upper steel sheet surface, the deformation induced in the surface of the upper blank metal progressively fills the die groove. this was numerically simulated by obtaining the necessary total punch displacement with respect to the time interval. figure 4 presents the deformed shape of both upper and lower sheets during clinching processes at 25%, 50%, 75% and 100% of the assigned punch displacement. (a) 25 % of the total punch displacement (initial shear insertion process) (b) 50 % of the total punch displacement (upsetting and spreading) (c)75 % of the total punch displacement (filling of the upper die section with complete filling of the ring groove). (d) 100% of the total punch displacement (retraction of the punch – indirect extrusion) figure 4: deformed shape of both upper and lower sheets during clinching processes at stages 25%-50%-75% and 100% of the assigned punch displacement numerical investigation of springback in mechanical clinching process 89 at 100% of the punch displacement, the upper steel sheet and the lower aluminium sheet take the shape of the die and any subsequent increase in the displacement of the punch causes an increase in the load. the springback was predicted in terms of the vertical displacement from the total load conditions until the material flow to fill in the die cavity. this is done to induce a different level of plastic strain in both sheets. the punch was later slowly returned to its start position, which gradually allowed the release of the elastic energy. the final shapes of the clinching joint, before and after the release of the load, are shown in figure 5. (a) von miese stress before (stress release) springback analysis with value 1.050 gpa (b) von mises stress after springback analysis with value 1.048 gpa (with stress release) figure 5: final shape of the joint before and after stress release (springback analysis) 2.2 taguchi method the taguchi method is one of the most efficient experimental design tools that test combinations of causes and helps to optimize a process and determine factors that influence variability. the minimum number of experiments, which could give the full information of all the factors that affect the performance parameter, are stipulated by standard orthogonal arrays devised by taguchi. the signal-to-noise ratio (s/n) is the value of the loss function used to measure the performance characteristic deviation from the desired value. the analysis of the s/n ratio is usually carried out by one of three categories of the performance characteristic, namely, the nominal-the-better, the lower-the-better, and the higher-the-better. without being affected by the different process parameters, a larger signal to noise (s/n) ratio corresponds to the better performance characteristic. s/n(larger the better) = −10 log �1 n ∑ 1 yi 2 n i=1 � (1) where n is the number of measurements, yi is the measured characteristic value. the reason behind using the analysis of variance (anova) is to find the clinching process parameters that significantly affect the response or performance characteristics. generally, this can be achieved by separating the total variability of the response, measured by the sum of squared deviations from the total mean of the response factors, into the contribution from each of the process parameters and the error [7, 8]. hence, sst = ssf + sse (2) where sst = ∑ �γȷ� − γm� p j=1 2 (3) sst – total summation of the squared deviations about the mean γm – grand mean of the response γj – mean response for the jth experiment t p – number of experiments in the orthogonal array ssf – sum of square deviation due to each factor sse error of the sum of the squared deviation moreover, the f-test was employed to indicate which of the forming parameters had an effective influence on the performance characteristic. generally, the variation of the process parameter exerts a significant effect on the performance characteristic of the process when the f-test value is large. 3 results and discussions as illustrated in figure 6, there is an opening between the upper sheet and the lower sheet after removing the load of the punch and the blank holder. this gap is due to the springback created from the remaining internal stress of the two sheets. the values of the vertical displacement of the selected element (7202) before and after springback analysis are shown in figure 7 and figure 8, respectively. the location of the node after forming, in terms of x and y coordinates, are 3.03973mm, 2.70622mm respectively while after springback, the coordinates are 3.03902mm and 2.70926mm. the difference between the two points is very small around 0.00304 mm in the negative y-axis direction. eshtayeh et al., (2017): international journal of engineering materials and manufacture, 2(4), 86-93 90 another way to measure the vertical displacement is to measure the change in the vertical distance before and after the springback analysis by taking one node as a reference and same node after recovery of the stress. figure 9 shows the history of node 8232 with reference to the node coordinate in the y-coordinate system. the graph shows that the difference between the two sheets or the opening between the two blanks is around 0.07 mm in the vertical direction (y). the difference in location of node 8232 before and after springback is very small, which is about 5e4mm and 1.87e-3mm in x and y coordinates respectively. the distance is decreased from 0.07 mm in the vertical direction to be 0.00187 mm after springback analysis. figure 6: springback between the two joints before the release of the stress (springback analysis) figure 7: vertical y-displacement of element no. 7202 before springback figure 8: vertical ydisplacement of element no. 7202 after springback figure 9: vertical y-coordinate system versus time for node 8232 figure 10 (a) shows the upper sheet with the lower surface before and after springback analysis where the back line showing the lower surface before springback and the red one after springback while figure 10 (b) shows the lower sheet’s upper face before and after. the resultant force between the two parts (upper and lower sheets) is shown in figure 11, which indicates that the force reached the max value 0.15 kn. after 0.1 m-sec the force started to decrease to a value of 0.14 kn with 0.2 m-sec, after which it gradually levelled at approximately 0.13 kn. the stability of the resultant force between the two blanks gives an indication that there is an interlock between the two parts. the taguchi method was used to investigate the most important parameters affecting the springback analysis using the implicit simulation technique as an experiment. taguchi’s l27 orthogonal array design and the notion of signal to noise (s/n) ratio were utilized to obtain the objective function. analysis of variance (anova) showed the importance of factors on overall output. the output of the study showed that there are no main parameters affecting the springback. it may be worth changing the materials used as the clinched sheets to high tensile steel or stainless steel in order to have higher springback values. indeed, the die groove height, die diameter, punch diameter, punch corner radius and clearance between punch and blank holder were found to be the most influential parameters on the bottom and neck thicknesses for the clinching process[9]. table 1 shows selected simulation results from the 27 simulations of the springback process. the distance between the two sheets after the explicit simulation was almost zero. numerical investigation of springback in mechanical clinching process 91 (a) upper sheet lower surface before and after springback analysis (red line shows after spring back, where black one before) (b) lower sheet upper face before and after springback (black line before, red after) figure 10: springback analysis for upper sheet lower face and lower sheet upper face 0 0.5 1 1.5 2 2.5 3 3.5 0 1 2 3 4 5 6 7 m m mm 0 0.5 1 1.5 2 2.5 3 3.5 0 1 2 3 4 5 6 7 m m mm before after eshtayeh et al., (2017): international journal of engineering materials and manufacture, 2(4), 86-93 92 figure 11: resultant force between the upper and lower parts with time. table 1: sample results of the orthogonal array l27 of the clinching simulation and springback. exp. no. simulation output springback analysis (explicit analysis) x tn ts stress flow contour during clinching process stress flow contour after stress release dimensions are in mm 1 0.847 0.358 0.101 9 0.859 0.362 0.027 18 0.845 0.400 0.041 27 1.237 0.256 0.01 6 conclusions in this paper, the finite element modelling of the clinching methods and springback analysis were discussed. the fixed type of die was investigated using ls-dyna commercial software. the friction was assumed to be constant between the areas of contact using coulomb’s law. to save computational effort the simulations were carried out using 2daxisymmetric modelling approach. the high plasticity during the forming of the joint establishes a large element distortion creating numerical problems during the simulation, where the adaptive remeshing option was used to overcome this problem. the results using the springback analysis show the possibility of calculating the springback numerical investigation of springback in mechanical clinching process 93 values (opening between the two sheets after forming the joints) between the two sheets. the optimization of the clinching process to indicate the optimal parameters affecting the springback between the two sheets can be obtained using the taguchi optimization methods. reference 1. kadkhodayan, m. and i. zafarparandeh (2009). an investigation into the influence of blankholder force on springback in u-bending. archives of metallurgy and materials, 54(4), 1183-1190. 2. nikhare, c. (2012). a numerical approach on reduction of young’s modulus during deformation of sheet metals. modeling and numerical simulation of material science, 2(01), 1-13. 3. lee, s.-w. and y.-t. kim (2007). a study on the springback in the sheet metal flange drawing. journal of materials processing technology, 187, 89-93. 4. siswanto, w.a., et al. (2014). an alternate method to springback compensation for sheet metal forming. the scientific world journal. 5. nasrollahi, v. and b. arezoo (2012). prediction of springback in sheet metal components with holes on the bending area, using experiments, finite element and neural networks. materials & design (1980-2015), 36, 331336. 6. coppieters, s., et al. (2011). reproducing the experimental pull-out and shear strength of clinched sheet metal connections using fea. international journal of material forming, 4, 429-440. 7. mondal, s., et al. (2013). application of taguchi-based gray relational analysis for evaluating the optimal laser cladding parameters for aisi1040 steel plane surface. the international journal of advanced manufacturing technology, 66(1-4), 91-96. 8. datta, s., a. bandyopadhyay, and p.k. pal (2008). grey-based taguchi method for optimization of bead geometry in submerged arc bead-on-plate welding. the international journal of advanced manufacturing technology, 39(11-12), 1136-1143. 9. eshtayeh, m. and m. hrairi (2016). multi objective optimization of clinching joints quality using grey-based taguchi method. the international journal of advanced manufacturing technology, 87(1-4), 233-249. international journal of engineering materials and manufacture (2017) 2(2) 31-36 https://doi.org/10.26776/ijemm.02.02.2017.02 m. a. rahman , a. a. jasani, and m. a. ibrahim department of manufacturing and materials engineering international islamic university malaysia p.o. box 10, 50728 kuala lumpur, malaysia e-mail: mrahman@iium.edu.my reference: rahman, m. a., jasani, a. a. and ibrahim, m. a. (2017). flexural strength of banana fibre reinforced epoxy composites produced through vacuum infusion and hand lay-up techniques – a comparative study. international journal of engineering materials and manufacture, 2(2), 31-36. flexural strength of banana fibre reinforced epoxy composites produced through vacuum infusion and hand lay-up techniques – a comparative study mohamed abd rahman, abdul aziz jasani and mohd azizuddin ibrahim received: 15 march 2017 accepted: 30 june 2017 published: 30 june 2017 publisher: deer hill publications © 2017 the author(s) creative commons: cc by 4.0 abstract natural fibres from such as kenaf, sisal, pineapple leaf and banana are becoming popular nowadays due to their many advantages over traditional glass fibres in reinforcing polymer composites. these fibres are renewable, abundantly available, economical, lightweight and environmental friendly. this work compared the flexural property of banana fibre-reinforced epoxy composites produced via vacuum infusion and hand layup processes. banana fibres were treated with sodium hydroxide (naoh) solution for 1 hour before been dried in the oven for 24 hours at 100°c. an aluminium vacuum infusion mold was manufactured per the standard flexural test specimen of 127mm x 12.7mm x 3.2mm. composite specimens were produced while varying fibre volume fraction of 20% and 40% as well as fibre length of 63 mm and 127mm. the highest flexural strength of 136.27 mpa was achieved by specimens made by vacuum infusion process with 40% volume fraction and 63mm fibre length while for hand layup process, the highest flexural strength was only 80.71 mpa with equal fibre content and fibre length. at both fibre lengths, using vacuum infusion resulted in the increase in flexural strength in the range of 31.4 to 107.9% over hand layup. using vacuum infusion has resulted in banana fibre-reinforced epoxy composites with better flexural properties compared to those produced using hand layup process which allow excellent reinforcing characteristic of banana fibres to be realized. keywords: vacuum infusion, hand lay-up, banana fibre, epoxy, volume fraction, fibre length, flexural strength. 1 introduction composites have always attracted interests in the production of goods as this class of materials is known to have excellent properties resulting from the individual components making each composite. the most vital of all the properties are mechanical properties for most applications [1]. achieving important mechanical properties such as flexural strength cannot be easily done using a single material but is possible with composites [2]. nowadays, due to environmental and economic reasons, there is an ever-increasing interest in the use of greener materials as replacement of more traditional ones in the production of goods? a good example of this trend is the research done on natural fibres as reinforcing materials in composites. natural fibres originating from plants such as flax, hemp, jute, kenaf, oil palm, sisal, banana and many more are said to possess many advantages over their synthetic counterparts like glass and carbon fibres. these renewable materials are known to be strong, lightweight, readily available and less hazardous. natural fibres are already known to possess numerous advantages with banana fibres becoming more popular with researchers and industrialists [3]. venkateshwaran and elayaperumal (2010) reviewed the works done on banana fibres, their uses as composite reinforcing phase and the resulting properties [4]. banana fibres with their high specific strength can be utilized to produce light weight composites to manufacture light weight automobile interior parts [3]. in a few studies, banana fibres were used to reinforce epoxy while studying effect of fibre length and optimum fibre loading [5 7]. in the study of santhosh et al (2014), 30% fibre fraction was used without specifying banana fibre length [6]. raghavendra et al (2012) utilized short banana fibres of length 2 to 10 mm and a constant 20% fibre flexural strength of banana fibre reinforced epoxy composites produced through vacuum infusion and hand lay-up…. 32 weight [5]. one study tested the properties of single banana fibres and used them in finite element analysis of banana fibre reinforced composites while assuming continuous banana fibres and 5 – 20% fibre weight [8]. earlier, laly et al (2003) investigated banana fibre reinforced polyester composites and found that the optimum content of banana fibre is 40% [9]. to improve wettability, sodium hydroxide is the most commonly used chemical to treat natural fibres [5, 6]. alkali treatment or mercerization using sodium hydroxide (naoh) is the most commonly used treatment for bleaching and cleaning the surface of natural fibres to produce high-quality fibres. modifying natural fibres with alkali has greatly improved the mechanical properties of the resultant composites. most if not all the above studies used hand layup method to produce the composites. hand layup process is inexpensive and simple but the composites may contain drawbacks like voids, poor fibre compaction and wrinkling [10]. there are other composite processing methods and vacuum infusion composite is one of the well-established methods. in vacuum infusion, resin is drawn into the reinforcing fibres using vacuum resulting in better fibre-to-resin ratio resulting in lightweight and stronger composite products. vacuum infusion process produced composites with better mechanical properties than hand layup method [11]. yuhazri et al (2010) however studied polyester composites reinforced with continuous kenaf fibres produced by hand layup and vacuum infusion methods in which they found that tensile strength and modulus of the composites produced using vacuum infusion technique were higher than those produced using hand layup [11]. despite various works on banana fibres and their uses in reinforcing polymer composites, information on the usage of banana fibres in reinforcing polymers is somewhat limited in the literature [8]. especially there was little if any on banana fibre reinforced epoxy composites made by using vacuum infusion and comparison of the resultant properties with those produced using hand layup process. therefore, there was a need to further study the mechanical properties of banana fibre-reinforced epoxy composites using vacuum infusion method. by using this technique to make banana fibre-reinforced epoxy composites, it was expected that higher mechanical properties in particular flexural strength would result which would hopefully lead to higher utilization of these natural fibres for commercial use. to achieve this, banana fibre-reinforced epoxy composite specimens were prepared using vacuum infusion and hand layup methods while experimenting with different fibre contents and fibre lengths and studied the resulting flexural strength. 2 methodology banana fibres were used as reinforcing phase in epoxy composites. the fibres were treated with 5% naoh solution for 2 hours before thoroughly washed under running water. drying of the fibres was done in the oven for 24 hours at 100 0 c. e-110i epoxy resin was used with h-10 hardener in a 2:1 ratio. to make the composite specimens of banana fibre-reinforced epoxy, a vacuum infusion aluminium mold was prepared using cnc milling machine. the mold has cavities with dimensions 127mm long, 12.7mm wide and 3.2 mm deep as per astm d790 [12]. figure 1 shows the schematic experimental setup of vacuum infusion (vi) process. full factorial experiments were carried out with three factors and two levels (table 1) totalling 8 experiments. figure 2 (a and b) shows the various banana fibre-reinforced epoxy composites that were successfully manufactured using vacuum infusion (vi) and hand layup (hl) processes. in every specimen, banana fibres were arranged longitudinally in the mold cavities. a b figure 1: experimental setup; (a) vacuum infusion process, and (b) universal testing machine. rahman et al., (2017): international journal of engineering materials and manufacture, 2(1), 31-36. 33 table 1: experimental parameters and responses run factors flexural strength (mpa) volume fraction (%) fiber length (mm) process sample 1 sample 2 sample 3 average 1 20 127 vi 86.07 93.93 98.99 93.00 2 20 63 vi 111.98 104.24 98.29 104.84 3 40 127 vi 133.34 144.17 121.65 133.10 4 40 63 vi 87.95 151.06 169.79 136.27 5 20 127 hl 96.71 55.02 60.68 70.80 6 20 63 hl 64.62 60.42 66.95 63.99 7 40 127 hl 58.93 84.02 49.15 64.03 8 40 63 hl 73.23 80.45 88.46 80.71 a b c figure 2: specimens of banana fiber-epoxy composites; (a) produced by vacuum infusion process, (b) produced by hand layup process, and (c) after undergoing flexural test. 3 results and discussions from the analysis of variance of the flexural strength data (see table 2), fibre content and process type significantly affect the composite flexural strength. fibre length did not seem to affect flexural strength significantly as both lengths may be considered to represent long fibres. raghavendra et al (2012) determined that optimal condition was at 4 mm length for banana fibre-reinforced epoxy composites when studying the effect of fibre length on tensile strength. they reported slight decrease of tensile strength when longer fibre lengths used [5]. similar flexural strength values were obtained by santhosh et al (2014) when they studied banana fibre-reinforced epoxy composites produced using hand layup [6]. at 20% and 40% fibre content, using vacuum infusion resulted in 63.8% and 68.8% increase in flexural strength respectively compared to hand layup. this increase was also consistent with works using conventional fibres in which flexural strength of material prepared by vacuum infusion almost double compared to those prepared using hand layup method [13]. table 2: analysis of variance of flexural strength data sources of variation ss dof ms fo p-value fibre content (a) 2486.77 1 2486.77 6.72 0.0196 fibre length (b) 233.00 1 233.00 0.63 0.4390 process type (c) 13198.60 1 13198.60 35.69 0.0000 ab 82.81 1 82.81 0.22 0.6425 ac 1420.19 1 1420.19 3.84 0.0677 bc 10.06 1 10.06 0.03 0.8711 abc 386.72 1 386.72 1.05 0.3217 error 5917.63 16 369.85 total 23735.78 23 flexural strength of banana fibre reinforced epoxy composites produced through vacuum infusion and hand lay-up…. 34 figures 3 and 4 indicate clearly that using vacuum infusion made it possible to realize the reinforcing capability of the banana fibres as the fibre content increased. at both fibre lengths used, increasing fibre content resulted in large increases in composite flexural strength. similar increases were not obtained using hand layup method. in fact, a slight reduction in flexural strength was observed. this is somewhat expected as hand layup process signifies variation in composite properties due to sources such skill, inability to remove air bubbles trapped, difficulty in handling large amount of fibre content. on the other hand, use of vacuum infusion entails more consistent process. figures 5 and 6 below further indicate the benefits of using vacuum infusion method over hand layup method. it is clear that increasing the fibre content resulted in the increase in flexural strength. however, at each fibre content in the vacuum infusion process, using longer fibres resulted in very slight decreases in flexural strength. similar decrease in flexural strength was also observed another previous work [8]. since the length of banana fibres extracted from the tree trunks is inconsistent, shorter fibre lengths may be utilized in composite processes without jeopardizing the properties significantly. figure 7 above shows the flexural strength of the specimens with 40% fibre content and specimens of neat resin made by vacuum infusion process. at 40% fibre content, the use of vacuum infusion resulted in 29.7% increase in flexural strength compared to neat resin. additionally, the specimens with 40% volume fraction achieved highest flexural strength at 136.27mpa. the variations of flexural strength for the samples prepared by vacuum infusion process and hand layup process are compared as shown in figure 8. figure 3: shows the relationship of volume fraction on flexural strength of specimens with fiber length 127 mm figure 4: shows the relationship of volume fraction on flexural strength of specimens with fiber length 63 mm figure 5: shows the relationship of volume fraction on flexural strength of specimens with volume fraction 20% figure 6: shows the relationship of fiber length on flexural strength of specimen with volume fraction 40%. rahman et al., (2017): international journal of engineering materials and manufacture, 2(1), 31-36. 35 figure 7: relationship between specimen with 40% volume fraction offiber and specimen with no-fiber manufacture by vacuum infusion process. figure 8: the variation of flexural strength of specimens with different factors produce with different process. the above results clearly indicate the advantages of vacuum infusion process in terms of producing banana fibre reinforced composites with better mechanical properties hence quality. the vacuum causes bubbles from resin to be removed from the experimental setup and atmospheric pressure to compress the fibre laminates forcing better wetting of the fibres by the resin. better wetting of fibres led to better fibre-matrix interface and the resultant higher flexural strength. in contrast, for hand lay-up method, the process was carried out in environment exposed to moisture and other gases which could react thus affect the composites during curing process [11]. vacuum infusion may be used to produce greener products made of polymer composites reinforced with natural fibres like banana fibres. excellent characteristics of natural fibres as reinforcing phase in composites may be realized. not only product quality will be increased, an eco-friendlier and less wasteful process will result. 4 conclusions in this study, banana fibre-reinforced epoxy composites were successfully made using hand layup and vacuum infusion methods. flexural properties of these composites were studied with 20% and 40% fibre contents and 63 mm and 127 mm fibre lengths. it may be concluded that: 1. using vacuum infusion method to produce banana fibre-reinforced epoxy composites resulted in an increase in flexural strength compared to neat resin with a maximum of 29.7% increase at 40% fibre content. 2. banana fibre-reinforced composites had higher flexural strength when produced using vacuum infusion process. 3. at both 63 mm and 127 mm fibre length, increasing fibre content from 20% to 40% resulted in the increase in flexural strength by 30.0% and 43.1% respectively. in similar instances, the use of hand layup resulted in reductions in flexural strength. 4. at both fibre lengths, using vacuum infusion resulted in the increase in flexural strength in the range of 31.4 to 107.9% over hand layup. 5. at both 20 and 40% fibre contents, flexural strengths slightly reduced upon using 127 mm over 63 mm long fibres. using hand layup resulted modest increase and even higher reduction respectively. 6. at both fibre contents, using vacuum infusion however resulted in much greater increases in flexural strength compared to the use of hand layup. 7. the highest flexural strength was obtained with a specimen having 40% fibre content and 63 mm fibre length produced by vacuum infusion process which is 136.27mpa. 8. vacuum infusion has been shown to produce banana fibre-reinforced epoxy composites with better flexural properties compared to those produced using hand layup process. combination of other natural fibres can be used with banana fibres to develop hybrid composites and the properties determined. filler material can be also used in the composites for possible improvements of the composite properties. acknowledgement the authors are grateful to the international islamic university malaysia for funding the study and the kulliyyah of engineering where the experimental studies were conducted. flexural strength of banana fibre reinforced epoxy composites produced through vacuum infusion and hand lay-up…. 36 references 1. nielsen, l.e. & landel, r.f. (1994). mechanical properties of polymers and composites. 2nd, new york: marcel dekker inc. 2. begum, k. & islam, m. a. (2013). natural fiber as a substitute to synthetic fiber in polymer composite: a review. research journal of engineering sciences, 2(3), 46-53. 3. ashwin sailesh and s.prakash, s. (2013). review on recent developments in natural fiber composites. international journal of engineering research & technology (ijert), 2(9), 2523-2525. 4. venkateshwaran, n. and elayaperumal, a. (2010). banana fiber reinforced polymer composites – a review. journal of reinforced plastics and composites, 29(15), 2387-2396. 5. raghavendra. s, p.balachandrashetty, p., mukunda, p. g. and sathyanarayan, k. g. (2012). the effect of fiber length on tensile properties of epoxy resin composites reinforced by the fibres of banana. international journal of engineering research & technology (ijert), 1(6), 1-3. 6. santhosh, j., balanarasimman, n., chandrasekar, r. and raja, s. (2014). study of properties of banana fiber reinforced composites. international journal of research in engineering and technology (ijret), 3(11), 144-150. 7. vinod, b. and sudev, l. j. (2013). effect of fiber length on the tensile properties of palf reinforced bisphenol composites. international journal of engineering, business and enterprise applications (ijebea), 13(262), 158162. 8. shashi shankar, p., thirupathi reddy, k. and chandra sekhar, v. (2013). mechanical performance and analysis of banana fiber reinforced epoxy composites. international journal of recent trends in mechanical engineering (ijrtme), 1(4), 1-10. 9. laly a. pothana, zachariah oommenb, and thomas s, “dynamic mechanical analysis of banana fiber reinforced polyester composites”, composites science and technology, 63(2), 2003, pp. 283-29. 10. delaney, j. c., & karbhari, v. (2006). the assessment of aspects related to defect criticality in cfrp strengthened concrete flexural members. rep. no. ssrp 06/11, dept. of structural engineering, univ. of california-san diego, la jolla, ca. 11. mohammad yuhazri, y., phongsakorn, p. t., & haeryip sihombing. (2010). a comparison process between vacuum infusion and hand lay-up method toward kenaf-polyester composites. international journal of basic & applied sciences ijbas-ijens. 10(3), 54-57. 12. american standard of testing and materials-astm international (2003). standard test methods for flexural properties of unreinforced and reinforced plastic and electrical insulating materials. united state, astm d79003. 13. bhatnagar, a. and niranjan kumar, i. n. (2015). vacuum infusion process for composite vessel construction. international journal of innovative research & development. 4(7), 1-7. international journal of engineering materials and manufacture (2016) 1(2) 51-58 https://doi.org/10.26776/ijemm.01.02.2016.02 m. konneh , and m. mokhtar department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: mkonneh@iium.edu.my reference: konneh, m., and mokhtar, m. (2016). performance evaluation of diamond grits during precision surface grinding of silicon carbide. international journal of engineering materials and manufacture, 1(2), 51-58 performance evaluation of diamond grits during precision surface grinding of silicon carbide mohamed konneh, and masturah mokhtar received: 06 october 2016 accepted: 29 november 2016 published: 20 december 2016 publisher: deer hill publications © 2016 the author(s) creative commons: cc by 4.0 abstract the excellent material properties of silicon carbide (sic), such as extreme hardness, high durability, high wear resistance and light weight, have caused a wide range of industrial applications of this material. among the engineering applications of this material, it is an excellent candidate for optic mirrors used in an airbone laser (abl) device. however, the brittleness and low fracture toughness characteristics of the sic are predominant factors for its poor machinability. this paper presents surface grinding of sic using resin bonded diamond abrasive cup wheels to assess the cutting performance of diamond grits on the roughness and morphology of the ground workpieces. the wheel grits of grit 46 µm, 76 µm and 107 µm were used. the parameters employed during the machining investigation are depth of cut between 10 30 µm and feed rate between 2 22 mm/min. it is observed that the 76 µm grit performs better in terms of low surface roughness value and minimal fractured surface morphology. keywords: silicon carbide, surface grinding, cup wheel, diamond grits, surface roughness and morphology. 1 introduction silicon carbide (sic) material had long been introduced in into the precision manufacturing industries in the mid1990s due to its potential industrial applications although the material has been around since 1891. the material is well known for its material properties like extreme hardness, high durability, high wear resistance and light weight. according to ravindra, et al. [1], sic being one of the advanced engineered ceramics, was designed to operate in extreme environments. also, it had been revealed by [2, 3] that sic had been employed as a coating and structural material due to its unique properties which are not limited to the larger energy bandgap and breakdown field allowing of the material to be used in high temperature, high-power and radiation-hard environments, its mechanical stiffness expressed by high young’s modulus and the material’s tribology properties such as wear resistance and self-lubricating. silicon carbide is an excellent candidate for optic mirrors used in an airbone laser (abl) device. despite the salient properties of this sic material, it is nevertheless noted for its low fracture toughness and extreme brittleness which result into its poor machinability. based on the author’s [4, 5] machining research experience, it has been observed that hard and brittle like semiconductors, ceramics and glasses are problematic especially when it comes to machining. however, the authors’ [4, 5] research works have demonstrated that when attempting to machine ceramic like sic to improve the surface finish, a ‘damage free’ machining operation often through ductile mode machining (dmm) is possible. ductile mode machining is a process of machining a nominally hard and brittle material such that the materials as if it is ductile material. such a material removal process can be considered in terms of fracture dominated mechanisms or localized plastic deformation. a fracture (brittle fracture) dominant mechanism for ceramics can result in poor surface quality and also deteriorates the material properties and performance [6]. grinding research conducted on brittle materials by bifano et al. [7] revealed that two types of material removal mechanisms are associated with the machining processes, ductile machining in which plastic flow of material in the form of severely sheared machining chips occurs and brittle machining where material removal is through crack propagation. several physical parameters that influence the ductile to brittle transition in grinding of brittle materials are discussed machining literature. some successes have been reported on ductile mode grinding of performance evaluation of diamond grits during precision surface grinding of silicon carbide 52 brittle materials but neither a machining model was not proposed nor a suitable explanation for the origin of ductile regime machining was confirmed until bifano showed up. bifano et al. [7] proposed a model defining the ductile to brittle transition of a nominally brittle material based on the material’s brittle fracture properties and characteristics. they introduced a critical depth of cut model based on griffith fracture propagation criteria, hence the expression for the critical depth of cut (dc) which follows: dc = (e . r) /h 2 (1) where e is the elastic modulus, h the hardness and r the fracture energy. the value of the fracture energy (r) can be evaluated using the relation: r~ kc 2 / h (2) where kc is the fracture toughness of the material. the combination of equations (1) and (2) represents the critical depth (dc) which is a measure of the brittle to ductile transition depth of cut: dc ~ (e / h) . (kc / h) 2 (3) the researchers successfully determined a correlation between the calculated critical depth of cut and the measured depth generally considered as the grinding infeed rate. the constant of proportionality was estimated as to be 0.15. this constant when introduced in equation (3) resulted into more accurate empirical equation (4): dc ~ 0.15 (e / h) (kc / h) 2 (4) equation 4 gives an insight into how a depth of cut is critical in machining brittle materials, considering the material properties and characteristics. this paper presents surface grinding of silicon carbide using diamond cup wheels to assess the performance of diamond grits with respect to the surface roughness generated on the machined surface and also the morphology ground work-piece. 2 experimental details 2.1 work and tool materials the dimensions of the silicon carbide (sic) workpiece used in this research work are samples of 20 mm x 20 mm x 10 mm. there were glued in specially fabricated fixtures made of aluminum as shown in figure 1. the cutting tools chosen for this study are resin bonded diamond cup wheels (figure 2) of different grain sizes. the experimental conditions are shown in table 1. figure 1: silicon carbide work-piece glued on an aluminum fixture. figure 2: diamond cup wheel 75 x 10 x 3 x 16mm bore silicon carbide konneh and mokhtar (2016): international journal of engineering materials and manufacture, 1(2), 51-58 53 table 1: experimental condition and variables workpiece silicon carbide (sic) (20mm x 20mm x 10mm) tool material diamond cup wheel 75 x 10 x 3 x 16mm bore grain size, a, (μm) 46, 76, 107 depth of cut, b, (μm) 10, 20, 30 feed rate, c, (mm/min) 2.0, 12.0, 22.0 2.2 experimental setup and procedure the setup for the machining experiments on a 3-axis vertical nc deckel maho (dmu) machine, which maximum rotational speed of 6300 rpm, is depicted in figure 3. a total of 17 trial runs (table 2) were carried out based on box-behnken design of experiments. surface roughness measurements were done on a mitutoyo surftest sv-500 surface tester, figure 4. a 0.8 mm cut-off length was used and average roughness readings were noted. scanning electron microscopy technique was used to examine the surface morphology of the ground silicon surfaces. figure 3: experimental setup of the work-piece on dmu 35m deckel maho milling machine. figure 4: mitutoyo surftest sv-500 machine on which, surface roughness was measured. 3 results and discussion 3.1 discussion of surface roughness results box-behnken experiment design was used to study the relationship between grinding parameters and the response roughness variable (ra). table 2 shows the surface roughness (ra) results obtained based on box-behnken experimental design with three center points. analysis of variance (anova), table 3, was done to verify the adequacy of the developed models. the main and interaction effects of the grinding parameters on the response parameters have been established. from table 3, it is observed that interaction ab between parameters a (grit size) and b (depth of cut) virtually has no effect on the response variable, hence model reduction was necessary. the reduced anova is shown in table 4. from the reduced anova table 4, it can be seen that the model f-value of 10.94 implies the model is significant. on statistical basis, there is only a 0.14% chance that a "model f-value" this large could occur due to noise. values of "prob > f" less than 0.0500 indicate model terms are significant and values greater than 0.1000 indicate the model terms are not significant. in this case a, b, a 2 , b 2 , c 2 , ac, bc are significant model terms. the "lack of fit f-value" of 1.88 implies the lack of fit is not significant relative to the pure error and there is a 27.88% chance that a "lack of fit f-value" this large could occur due to noise. non-significant lack of fit is desired as we want the model to fit. the normal plot of residuals (figure 5) and the oulier plot (figure 6) reveal no problem with the trial runs. sic in a fixture performance evaluation of diamond grits during precision surface grinding of silicon carbide 54 table 2: box-behnken designs showing trial runs and response variable ra. std run factor a: grit size (µm) factor b: depth of cut (µm) factor c: feed rate (mm/min) response surface roughness (µm) 13 1 76.50 20.00 12.00 0.17 16 2 76.50 20.00 12.00 0.17 02 3 107.00 10.00 12.00 0.13 01 4 46.00 10.00 12.00 0.16 14 5 76.50 20.00 12.00 0.16 13 6 46.00 30.00 12.00 0.15 04 7 107.00 30.00 12.00 0.12 07 8 46.00 20.00 22.00 0.12 11 9 76.50 10.00 22.00 0.16 10 10 76.50 30.00 2.00 0.13 8 11 107.00 20.00 22.00 0.14 15 12 76.50 20.00 12.00 0.18 17 13 76.50 20.00 12.00 0.18 09 14 76.50 10.00 2.00 0.13 05 15 46.00 20.00 2.00 0.14 12 16 76.50 30.00 22.00 0.10 06 17 107.00 20.00 2.00 0.11 table 3: anova for response ra anova for response surface quadratic model [partial sum of squares] source sum of squares df mean square f value prob > f model 8.807e-003 9 9.78se-004 8.51 0.0050 significant a 6.125e-004 1 6.725e-004 5.33 0 0544 b 8.000e-004 1 8.000e-004 6.96 0.0335 c 1.250e-005 1 1.250e-005 0.11 0.7513 a 2 1 253e-003 1 1.253e-003 10.89 0.0131 b 2 9.161e-004 1 9.161e-004 7.97 0.0257 c 2 3.127e-003 1 3.127e-003 27.19 0 0012 ab 0 000 1 0 000 0 000 1.0000 ac 6.250e-004 1 6.250e-004 5.43 0 0525 bc 9 000e-004 1 9.000e-004 7.83 0 0266 residual 8.050e-004 7 1.1506-004 lack of fit 5 250e-004 3 1.750e-004 2.50 0 985 not significant pure error 2.800e-004 4 7.000e-005 cor total 9.612e-003 16 table 4: reduced anova for response ra anova for response surface reduced quadratic model [partial sum of squares] source sum of squares df mean square f value prob > f model 8.807e-003 8 1.101e-004 10.94 0.0014 significant a 6.125e-004 1 6.125e-004 6.09 0 0389 b 8.000e-004 1 8.000e-004 7.95 0.0225 c 1.250e-005 1 1.250e-005 0.12 0.7336 a 2 1 253e-003 1 1.253e-003 12.45 0.0077 b 2 9.161e-004 1 9.161e-004 9.10 0.0166 c 2 3.127e-003 1 3.127e-003 31.07 0 0005 ac 6.250e-004 1 6.250e-004 6.21 0 0374 bc 9 000e-004 1 9.000e-004 8.94 0 0173 residual 8.050e-004 8 1.006-004 lack of fit 5 250e-004 4 1.313e-004 1.88 0 2788 not significant pure error 2.800e-004 4 7.000e-005 cor total 9.612e-003 16 konneh and mokhtar (2016): international journal of engineering materials and manufacture, 1(2), 51-58 55 figure 5: the normal plot of residuals figure 6: the outlier plot indicating the trial runs are within range. a mathematical model represented by equation (5), was proposed to relate the response variable (ra) and the grinding parameters. thus, ra = (a, b, c) (5) where ra is the surface roughness;  the response function, a, the diamond grit size, b, the depth of cut and, c, the feed rate. second order model (equation (5)) was observed the most suitable to relate surface roughness and the grinding parameters. the procedure for establishing a second order model is well detailed out in alao’s [8] work. the model equation 6 has been developed based on the results obtained in this study. ra = +0.17 -0.008750a -0.010b + 0.001250c -0.017a 2 -0.015b 2 -0.027c 2 +0.012ac -0.015bc (6) verification of the adequacy of the model is shown in the anova table 4 where the model f-value of 10.94 implying the model is significant. the model graphs figure 7 shows the individual effects of the process grinding paprameters. from this plots, it can be seen that to get better (lower) surface roughness, it better to incresae the depth of cut (b) and use higher grit size (a). figures 8 and 10 illustrate the 2d interaction effects of the process variables, the corresponding 3d interaction effects are depicted in figure 9 and 11 respectively. performance evaluation of diamond grits during precision surface grinding of silicon carbide 56 figure 7: individual effects of the process variables. figure 8: the interaction effect of feed rate and grit size. figure 9: the 3d plot of the interaction effect of feed rate and grit size. konneh and mokhtar (2016): international journal of engineering materials and manufacture, 1(2), 51-58 57 figure 10: the interaction effect of feed rate and depth of cut. figure 11: the 3d plot of the interaction effect of feed rate and depth of cut. figure 12: scanning electron microscopic image for trial run 16 in table 2: grit size = 76 µm, depth of cut = 30 µm an 22 mm/min showing large areas of plastically deformed surface. performance evaluation of diamond grits during precision surface grinding of silicon carbide 58 3.2 discussion of surface morphology results scanning electron microscopy examination of the surface corresponding to a trial condition 16 in table 2: grit size = 76 µm, depth of cut = 30 µm an 22 mm/min, shows considerably large areas of the surface that have been plastically deformed, figure 12. macro-fractures are also evident at the ground surface. 4 conclusion for the surface grinding experimental investigations conducted using resin bonded diamond cup wheels of three grits 46 µm, 76 µm and 107 µm; depth of cut of 10 µm, 20 µm and 30 µm; and feed rate of 2 mm/min, 12 mm/min and 22 mm/min, the following can be concluded.  it has been observed that the 76 grit performs better in terms of low surface roughness value and this is evident in table 2, run 16 where the roughness value ra = 0.10 µm.  a mathematical model has been developed for predicting surface roughness values within the limits of the machining parameters that has been tested.  it has also been observed that the ground surfaces consist of large plastically deformed areas and small areas of fractured surfaces. acknowledgement the authors express their gratitude and thanks to the faculty of engineering and the research management centre (rmc), iium for moral support and financial support respectively. references 1. deepak, r., saurabh, v., & john, p. (2011). ductile mode micro laser assisted machining of silicon carbide, properties and applications of silicon carbide. prof. rosario gerhardt (ed.), isbn: 978-953-307-201-2. 2. gao, d, wijesundara, m. b. j., carraro, c., low, c. w., howe, r. t., & maboudian, r. (2003). high modulus polycrystalline 3c-sic technology for rf mems. proc. transducers 12th int. conf. solid-state sensors and actuators, 1160-1163. 3. ashurst, w. r., wijesundara, m. b. j., carraro, c. & maboudian, r. (2004). tribological impact of sic coating on released polysilicon structures. tribology letters, 17(2), 195-198. 4. konneh, m., iqbal, m., & faiz, n. m. a. (2012). diamond coated endmills in machining silicon carbide. advanced material research, 576, 531-534. 5. venkatesh, v. c., izman, s., sharif, s., mon, t. t., & konneh, m. (2003). ductile streaks in precision grinding of hard and brittle materials. sadhana, 28(5), 915-924. 6. ravindra, d., patten, j., & tano, m. (2007). ductile to brittle transition in a single crystal 4h sic by performing nanometric machining. proc. isaat precision grinding and conference, advances in abrasive 7. bifano, t. g., dow, t. g., & scattergood, r.o. (1991). ductile regime grindinga new technology for machining brittle materials. journal of engineering for industry, 113, 184-189. 8. alao, a. r., (2007). precision micro-scaled partial ductile mode machining of silicon. msc thesis, international islamic university, malaysia. international journal of engineering materials and manufacture (2018) 3(1) 55-62 https://doi.org/10.26776/ijemm.03.01.2018.07 m. y. ali , a. sabur, a. banu, m. a. maleque, and e. y. t. adesta department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: eadesta@iium.edu.my reference: ali, m. y., a. sabur, a. banu, maleque, m. a., and adesta, e. y. t. (2018). micro electro discharge machining of nonconductive ceramic. international journal of engineering materials and manufacture, 3(1), 55-62. * this article was presented in 2nd world symposium on mechanical and control engineering, guilin, china, 2-3 nov. 2017. micro electro discharge machining of nonconductive ceramic * mohammad yeakub ali, abdus sabur, asfana banu, md. abdul maleque and erry y. t. adesta received: 19 march 2018 accepted: 26 march 2018 published: 30 march 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract the micro-electro discharge machining (micro-edm) models established for single spark erosion are not applicable for nonconductive ceramics because of random spalling. moreover, it is difficult to create single spark on a nonconductive ceramic workpiece when the spark is initiated by the assisting electrode. in this paper, process development for nonconductive zirconium oxide (zro2) is discussed. it is shown that the charging and discharging duration depend on the capacitance and resistances of the circuit. the number of sparks per unit time is estimated from the single spark duration derived from heat transfer fundamentals. the model showed that both the capacitance and voltage are significant process parameters for material removal rate (mrr). however, capacitance was found to be the dominating parameter over voltage. as in case of higher capacitances, the creation of a conductive carbonic layer on the machined surface was not stable; the effective window of machining 101 103 pf capacitance and 80 100 v gap voltage or 10 470 pf capacitance and 80 110 v gap voltage. this fact was confirmed edx analysis where the presence of high carbon content was evident. conversely, the spark was found to be inconsistent using parameters beyond these ranges and consequently insignificant mrr. nevertheless, the effective numbers of sparks per second were close to the predicted numbers when machining conductive copper material. in addition, higher percentage of ineffective pulses was observed during the machining which eventually reduced the mrr. in case of validation, average deviations between the predicted and experimental values were found to be around 10%. keywords: micro-edm, nonconductive ceramics, assisting electrode, mrr 1 introduction advancement in technology has opened the windows of some special materials to meet particular requirements by means of miniaturization. nonconductive ceramics are considered one of the most promising materials that can fulfil the demands of multifarious miniaturized applications in microfluidics, reactors, electromechanical generators and for medical purposes. however, these materials are difficult to machine by conventional machining techniques due to their high hardness and brittleness. nonconventional machining processes are regarded as promising for the structuring or shaping of nonconductive ceramics [1]. micro-electro discharge machining (micro-edm) is a nonconventional, noncontact and effective process for structuring conductive, hard and brittle materials. most of the advanced ceramics are electrically nonconductive; therefore, micro-edm cannot be used directly. in recent years, an advanced technique has been introduced to utilize micro-edm for nonconductive ceramics in which an electrically conductive metallic layer, referred as the ‘assisting electrode’ (ae) is applied on the workpiece surface. using the ae and controlling the micro-edm process parameters such as capacitance, voltage and polarity, nonconductive ceramics (zro2, al2o3, si3n4 and sic) have been successfully structured. 1.1 nonconductive ceramics nonconductive ceramics are also known as engineering, advanced, technical, or insulating ceramics. their electrical conductivity is less than 0.1 scm-1 [2-3]. due to the excellent chemical and physical properties, nonconductive ceramics are now being used in fabrication of domestic, industrial and building products. specific applications include cutting micro electro discharge machining of nonconductive ceramic 56 tools, self-lubricating bearings, turbine blades, internal combustion engines, heat exchangers, ballistic armour, ceramic composite automotive brakes, diesel particulate filters, piezo-ceramic sensors and a wide variety of prosthetic products. currently, nonconductive ceramic materials are used in the biomedical field to fabricate femoral heads and acetabular cups for total hip replacement, dental implants and restorations, bone fillers and scaffolds for tissue engineering. nano-structured alumina (al2o3) and zirconia (zro2) based ceramics and composites or non-oxide ceramics could be potential candidate material for biomedical applications in the near future [4]. 1.2 micro-electro discharge machining micro-electro discharge machining (micro-edm) is an electro-thermal material removal process which is used for manufacturing three-dimensional micro-components. in this machining process, a series of electrical sparks or discharges occurs rapidly in a short span of time within a constant spark gap between the tool electrode and the workpiece. it is a complex process in which thermodynamic, hydrodynamic, electromagnetic and electrodynamic processes are involved. any material having a minimal electrical conductivity of 0.1 scm-1 can be machined by microedm irrespective of its hardness and brittleness [3]. in micro-edm, thermal energy evolved from the electrical sparks flows into the electrode, workpiece and dielectric fluid. a fraction of the heat is conducted through the workpiece and an enormous temperature rise causes melting and vaporization of a small amount of material from the workpiece [5]. in this way a micro-crater is formed in every effective spark. thus, theoretical models of material removal rate (mrr) and average surface roughness (ra) in micro-edm of conductive materials have been developed based on electrical circuit and heat conduction theories considering the material removal by melting and vaporization [6-8]. however, the micro-edm process can also be used for micro-structuring of electrically nonconductive ceramics applying ae [3]. in micro-edm of nonconductive ceramics, material is removed by melting, vaporization and spalling [9]. in micro-edm of nonconductive ceramics, after the removal of the initially applied assisting electrode, a layer of pyrolytic carbon (pyc) would be deposited on the workpiece surface, disassociating the carbonic dielectric in the absence of oxygen at the higher temperature. the new layer would have the threshold of electrical conductivity for continuation of the machining, resulting in material removal by melting, vaporization and spalling. since the melting, vaporization and spalling is the effect of energy and energy is the function of capacitance and voltage in a rc pulse circuit, it is postulated that mrr would have a functional relationship with capacitance and voltage. the models of micro-edm for nonconductive ceramics can certainly contribute towards making the process user-friendly and helping machining parameters selection for desired outputs. in micro-edm, the discharge duration and supplied energy are much lower than edm, with discharge duration limited to around 100 ns and the amount of supplied energy being about 10 µj. figure 1: schematic diagram of relaxation type pulse generator in edm [12] figure 2: schematic diagram of transistor type pulse generator in edm [12] ali, et al. (2018): international journal of engineering materials and manufacture, 3(1), 55-62 57 however, the power density is higher in micro-edm [10-11]. to create the pulses, relaxation or transistor type generators can be used. schematic diagrams of relaxation and transistor type pulse generators are shown in figure 1 and figure 2 respectively. in a relaxation type generator, resistance and capacitance are connected to the circuit in which the capacitor charging and discharging occur alternatively. using this circuit, discharge can be created with a high peak current for a short duration. current and gap voltage are controlled at a predefined level throughout the pulse on-time. in a transistor type pulse generator, a series of resistance and transistors are connected in series as a switching device. this circuit can provide longer discharge duration with a larger peak current. the transistor type circuit has a longer ignition delay time. generator selection in micro-edm depends on the desired machining outputs. the transistor type generator is capable of creating a higher energy with a larger peak current and longer discharge duration. on the other hand, the rc pulse generator can be controlled precisely to generate very low energy with a shorter discharge duration [12]. therefore, the rc pulse generator is used as the pulse creator in micro-edm to produce highly precise microstructures [13]. a multi-purpose miniature machine tool (dt-110, mikrotools inc., singapore) has been manufactured for micromachining with high precision in which a rc pulse circuit is used [14-15]. as a noncontact machining process, micro-edm is capable of machining any material which is electrically conductive, irrespective of its hardness, shape and strength [16]. micro-edm is useful in producing three-dimensional micro-structures with a higher mrr, a machining accuracy of 1-5 µm and an aspect ratio of more than 20 [17]. a minimum feature of 10 µm is possible in fabricating precise micro-hole, micro-mechanical parts, milling tools and complex micro-structures by micro-edm [18]. 1.3 assisting electrode ae is an additional conductive layer on the workpiece that is applied to initiate sparks during machining or structuring of nonconductive ceramic materials [19]. there are two methods of applying ae. in the first method, ae is adhered onto the workpiece to start machining. once the ae layer finishes, carbon molecule cracked from carbonic dielectric is deposited on the machined surface and a conductive thin layer is generated which assists in creating a further spark. the adhesive copper or aluminium foil, coated graphite, silver varnish, sputtered workpiece material with copper, silver or gold are the main materials used as ae. a schematic diagram of micro-edm of nonconductive ceramics using fixed ae is shown in figure 3. in the second method, conductive metallic ae foil or sheet is continuously fed into the machining zone by a servo mechanism as shown in figure 4. electro discharge (ed) milling of al2o3 has been successfully accomplished using the continuously feeding ae method and it is considered a suitable process for large area machining [20]. in this process, a steel wheel is used as a tool electrode mounted on a rotary spindle driven by an ac motor. the tool electrode and the ae are connected to the positive and negative poles of the pulse generator respectively. this paper presents the research development in micro-edm of nonconductive ceramic materials. micromachining techniques were discussed briefly to justify the selection of micro-edm for this study. basic principles, process parameters and characteristics of micro-edm were highlighted. assisting electrode techniques and material removal mechanisms in micro-edm of nonconductive ceramic materials were discussed extensively. special focus was given in exploring the theoretical modelling in micro-edm of nonconductive ceramic materials. from the review, it appeared that the most of existing micro-edm theoretical models are not applicable for nonconductive ceramic materials which results in the need to develop new models for process characteristics. figure 3: schematic diagram of micro-edm of nonconductive ceramics with fixed ae [2] micro electro discharge machining of nonconductive ceramic 58 figure 4: ed milling of nonconductive ceramics [21] 2 effect of different pulses on mrr pulses were recorded during micro-edm of zro2 and five categories of pulses have been identified which are as follows: 2.1 normal (effective) pulse: normal pulses are produced when the capacitor is fully charged before the spark and fully discharged during the sparks. one of the images of effective pulse is shown in figure 5. normal pulses are effective in material removal because of the maximum energy supply by the circuit. normal pulses were observed during the machining of cu ae and during the initial stage of ceramic removal. according to figure 5, the spark had occurred after the completion of charging, without any delay. the discharge shape was almost vertical, which indicates that there was no resistance between the tool and workpiece. the calculated spark number is 909090 for r = 103 ω and c = 220 pf. from figure 5, it is obvious that the effective sparks recorded by oscilloscope to be 902000 which agrees with the calculated value. figure 5: normal pulse at c = 220 pf and v = 110 v 2.2 pulse during cutting ceramics one of the images of ceramic pulses is shown in figure 6. once the copper ae was finished, sparks began to occur between pyc ae and the tool electrode, removing ceramic material. at the beginning of ceramic machining, the normal shape of voltage signal was observed in the charging stage. as the machining progressed, pulses began to ali, et al. (2018): international journal of engineering materials and manufacture, 3(1), 55-62 59 remain constant at peak for long periods which indicate that the capacitor was fully charged but was waiting to release energy. it can be assumed that the conductive pyc layer had yet to attain the sufficient thickness and conductivity for the sparks. once the conditions were fulfilled, the sparks occurred. from figure 6, it can be concluded that the ceramic pulses have a longer pulse-off time than normal pulses. 2.3 effective arc pulse some pulses were observed in which the capacitor was not fully discharged and the spark had occurred at higher voltages than zero, with lower currents. these are known as effective arc pulses. one of the images of effective arcs is given in figure 7. effective arcs have a smaller current than normal or ceramic discharges and remove a little amount of material. effective arcs occurred due to the presence of a small amount of debris in the gap. fewer electrons can reach the anode because of insufficient energy [20-21]. two types of effective arc pulses were observed. in the first type of effective arcs, pulse-off time was similar to the normal pulse. in the second category of effective arcs, pulseoff time was longer which is similar to ceramic pulse. figure 6: pulses during cutting ceramics at c = 100 pf and v = 110 v figure 7: effective arc discharge at c = 100 pf and v = 100 v longer pulse-off shorter pulse-off charging and discharging at higher voltage a: longer pulse-off time micro electro discharge machining of nonconductive ceramic 60 figure error! no text of specified style in document.8: immature discharges at c = 100 pf and v = 100 v 2.4 immature pulse during the deep machining of nonconductive ceramics, several pulses were observed in which sparks occurred after the capacitor voltage had reached a peak value. but charging started at a much higher voltage. these are identified as immature pulses. immature pulses are produced due to the presence of a huge amount of debris inside the cavity and it creates a very small amount of energy. one of the images of immature pulses is given in figure 8. most of the immature pulses do not follow the charging and discharging characteristics of the rc circuit. in many cases, they are mixed with normal and ceramic pulses and produce complex pulse shapes [22]. 2.5 short circuit the short circuit occurred frequently in micro-edm of nonconductive ceramics mainly due to two reasons: i) the presence of debris which creates the channel of current flow without the sparks; ii) tool movement towards the workpiece without creation of a sufficiently conductive carbonic layer. table error! no text of specified style in document.1 experimental parameters conditions values workpiece zro2 tool electrode cylindrical copper rod tool electrode diameter (mm) 1 tool electrode polarity -ve assisting electrode adhesive copper foil assisting electrode thickness (µm) 60 dielectric kerosene pulse generator rc resistance (kω) 1 variables factors parameters levels i ii iii a capacitance, c (pf) 1000 100 10 b voltage, v (v) 100 90 80 c speed, n (rpm) 350 300 250 d feed rate, f (µm/s) 2 1.6 1.2 ali, et al. (2018): international journal of engineering materials and manufacture, 3(1), 55-62 61 2.6 experimental design the design of experiments (doe) is the technique of defining and investigating all possible conditions in an experiment involving multiple factors. a scientific approach was used for planning and conducting the experiments and for analysing the data efficiently. the doe was used to: i) reduce the number of trials significantly. ii) identify important decision variables which control and improve the characteristics of the product or the process. iii) find out the optimal setting of the parameters. in this study, the taguchi method was used for doe and subsequent analysis of the results. it requires a minimum of one run per condition of the experiment. but one run does not represent the range of possible variability in the results. repetition allows determination of variance index called signal to noise ratio. the greater this value, the smaller the product variance around the target. the parameters and their levels for the mrr were selected based on an experimental study as presented in table 1. in the experimental investigations for the modelling of mrr, it was observed that the speed and feed rate are not significant parameters in micro-edm of zro2. to apply the models in micro-edm of nonconductive zro2 ceramic, parameters were found out by solving the developed models based on the expected mrrc. using the parameter values, micro-channels and micro cavities were machined on nonconductive zro2 ceramic material. expected mrrc were compared with the experimental values. 3 conclusions in this research, theoretical models of the material removal rate (mrr) in micro-edm of nonconductive zro2 ceramic have been developed and validated. the research findings have been summarized as follows. 1. process parameters for effective micro-edm of zro2 have been identified by experimental study. capacitance ranges of 101 103 pf and gap voltages of 80 100 v or capacitance ranges of 10 470 pf and gap voltages of 80 110 v have been identified as effective electrical parameters for micro-edm of zro2 with a –ve copper tool electrode and adhesive copper foil assisting electrode in kerosene dielectric fluid. 2. models have been developed for rc pulse micro-edm based on the single spark erosion using electrothermal theories. multiplying correction factor (ε) derived from experimental investigations have been introduced to adjust the mrr in micro-edm of nonconductive zro2. the theoretical mrr model has been expressed by following equation.       += mv s c h k h kkcvn mrr 21 2 2ρ ε ( )20022.000009.0043.0 vc ×+×+−=ε )(5 1 21 rrc n s + = where ε is an experimental correction factor which has been determined in terms of the process parameters of capacitance and voltage and is expressed by following equation. ns is the number of sparks per second which is estimated from the rc pulse charging and discharging duration and is expressed by: 3. it was found that the experimental mrrc is very low compared to the theoretical values due to the longer pulse-off time in micro-edm of nonconductive ceramics and for the effect of various ineffective pulses such as delayed discharge, short circuit, arching and immature discharges. in modelling, the formation energy of pyc and the machining energy of pyc were not quantified. therefore, in addition to spalling effect, the correction factor, ε also includes the effect of formation-dissociation of pyc and the effect of ineffective pulses. 4. from the experimental investigation, it was found that capacitance is the most significant parameter for the creation of a conductive pyc layer in micro-edm of nonconductive zro2 ceramic. however, the mrr is controlled by voltage as a whole. 5. the mrr in micro-edm of zro2 was found to be very low compared to other hard materials. because of electrical nonconductivity, a higher number of ineffective pulses were produced, which eventually lowered the mrr in zro2 as compared to conductive materials. 6. experiments were conducted to validate the mrr in micro-edm of conductive copper materials. the effective number of sparks were recorded by oscilloscope at the initial stage of machining about 902000, micro electro discharge machining of nonconductive ceramic 62 which agrees with the calculated spark numbers of 909090 (at r = 103 ω and c = 220 pf). it has been also observed that the number of effective pulses decreased with the increase of depth of cut and about 50% of pulses were found to be ineffective in micro-edm of conductive materials. 7. micro-channels have been created on zro2 with selected parameters for the expected mrrc values as one of the applications of micro-edm models. 8. it was shown that the mrrc in micro-edm of zro2 were found to be in agreement with the calculated expected values by an average error of 8.86 %. references 1. ji, r., liu, y., zhang, y., wang, f., chen, z., & dong, x. (2011). study on single-discharge machining characteristics of non-conductive engineering ceramics in emulsion with high open voltage and large capacitor. proceedings of the institution of mechanical engineers, part b: journal of engineering manufacture, 225(10), 1888-1898. 2. hösel, t., cvancara, p., ganz, t., müller, c., & reinecke, h. (2011). characterisation of high aspect ratio nonconductive ceramic microstructures made by spark erosion. microsystem technologies, 17(2), 313-318. 3. hösel, t., müller, c., & reinecke, h. (2011). spark erosive structuring of electrically nonconductive zirconia with an assisting electrode. cirp journal of manufacturing science and technology, 4(4), 357-361. 4. chevalier, j., & gremillard, l. (2009). ceramics for medical applications: a picture for the next 20 years. journal of the european ceramic society, 29(7), 1245-1255. 5. yoo, b. h., min, b.-k., & lee, s. j. (2010). analysis of the machining characteristics of edm as functions of the mobilities of electrons and ions. international journal of precision engineering and manufacturing, 11(4), 629632. 6. dhanik, s., & joshi, s. s. (2005). modeling of a single resistance capacitance pulse discharge in micro-electro discharge machining. journal of manufacturing science and engineering, 127(4), 759-767. 7. salonitis, k., stournaras, a., stavropoulos, p., & chryssolouris, g. (2009). thermal modeling of the material removal rate and surface roughness for die-sinking edm. the international journal of advanced manufacturing technology, 40(3-4), 316-323. 8. zahiruddin, m., & kunieda, m. (2012). comparison of energy and removal efficiencies between micro and macro edm. cirp annals-manufacturing technology, 61(1), 187-190. 9. liu, y., yu, l., xu, y., ji, r., & li, q. (2009). numerical simulation of single pulse discharge machining insulating al2o3 ceramic. proceedings of the institution of mechanical engineers, part b: journal of engineering manufacture, 223(1), 55-62. 10. schubert, a., zeidler, h., wolf, n. & hackert, m. (2011). micro electro discharge machining of electrically nonconductive ceramics. in aip conference proceedings, 1353, 1303. 11. wong, y., rahman, m., lim, h., han, h., & ravi, n. (2003). investigation of micro-edm material removal characteristics using single rc-pulse discharges. journal of materials processing technology, 140(1), 303-307. 12. kunieda, m., lauwers, b., rajurkar, k. p., & schumacher, b. m. (2005). advancing edm through fundamental insight into the process. cirp annals-manufacturing technology, 54(2), 64-87. 13. shin, h. s., park, m. s., & chu, c. n. (2011). machining characteristics of micro edm in water using high frequency bipolar pulse. international journal of precision engineering and manufacturing, 12(2), 195-201. 14. lim, h., wong, y., rahman, m., & edwin lee, m. (2003). a study on the machining of high-aspect ratio microstructures using micro-edm. journal of materials processing technology, 140(1), 318-325. 15. jahan, m., wong, y., & rahman, m. (2009). a study on the fine-finish die-sinking micro-edm of tungsten carbide using different electrode materials. journal of materials processing technology, 209(8), 3956-3967. 16. kumar, s., singh, r., singh, t., & sethi, b. (2009). surface modification by electrical discharge machining: a review. journal of materials processing technology, 209(8), 3675-3687. 17. liow, j. (2009). mechanical micromachining: a sustainable micro-device manufacturing approach? journal of cleaner production, 17(7), 662-667. 18. yan, m.-t., & lin, s.-s. (2011). process planning and electrode wear compensation for 3d micro-edm. the international journal of advanced manufacturing technology, 53(1-4), 209-219. 19. mohri, n., fukuzawa, y., tani, t., saito, n., & furutani, k. (1996). assisting electrode method for machining insulating ceramics. cirp annals-manufacturing technology, 45(1), 201-204. 20. liu, y., li, x., ji, r., yu, l., zhang, h., & li, q. (2008). effect of technological parameter on the process performance for electric discharge milling of insulating al2o3 ceramic. journal of materials processing technology, 208(1), 245-250. 21. liu, y., ji, r., li, x., yu, l., zhang, h., & li, q. (2008). effect of machining fluid on the process performance of electric discharge milling of insulating al2o3 ceramic. international journal of machine tools and manufacture, 48(9), 1030-1035. 22. sabur, a., moudood, a., ali, m. y., & maleque, m. a. (2014). effect of micro-edm parameters on material removal rate of nonconductive zro2 ceramic. applied mechanics and materials, 465, 1329-1333. international journal of engineering materials and manufacture (2021) 6(1) 43-49 https://doi.org/10.26776/ijemm.06.01.2021.04 agboola, j.b. , emmanuel, s.a. and oladoye, a.m. department of metallurgical and materials engineering faculty of engineering, university of lagos, akoka, nigeria e-mail: joeagboola@unilag.edu.ng reference: agboola, j.b., emmanuel, s.a. and oladoye, a.m. (2021). effects of cooling rate on the microstructure, mechanical properties and corrosion resistance of 6xxx aluminium alloy. international journal of engineering materials and manufacture, 6(1), 43-49. effects of cooling rate on the microstructure, mechanical properties and corrosion resistance of 6xxx aluminium alloy joseph b. agboola, emmanuel s. anyoku, atinuke m. oladoye received: 14 september 2020 accepted: 07 january 2021 published: 30 january 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract the applicability of materials is highly dependent on its microstructure and mechanical properties. aluminium alloy is being used extensively under diverse conditions. this study investigates the effects of cooling rate on the microstructure, mechanical properties and corrosion resistance of 6xxx-series aluminium alloy. aluminium ingot was melted in a muffle furnace and cast into rods. the cooling rate was controlled by holding the moulds at different temperatures. microstructural characteristics were examined by optical microscopy. mechanical properties such as impact strength, hardness, and tensile strength were analysed using standard methods. corrosion resistance was evaluated by potentiodynamic polarization. it was found that microstructures are dominated by ferrite and pearlite phases with different morphologies and grain sizes depending on the cooling rate. increasing the cooling rate resulted in microstructural refinement and chemical homogeneity, improvement in mechanical properties and corrosion resistance of the 6xxx alloy. keywords: 6xxx al, cooling rate, mechanical properties, corrosion resistance, hcl 1 introduction. most applications of aluminium alloy are dependent on their mechanical properties which are mainly dependent on microstructure [1]. 6xxx-series aluminium alloy is widely used as structural materials in aircraft and automobile because of its high strength and low density [2]. however, it has been observed that 6xxx aluminium alloy despite its good mechanical properties do undergo some form of corrosion attack, the effects of which results to loss of human lives and other economic consequences [3]. corrosion process in aluminium alloy has been attributed to heterogeneous microstructure containing intermetallic phases and precipitates that are usually present at the grain boundaries [4]. the effects of cooling rate on mechanical behaviour of bulk cast of a380 aluminium alloy by using copper as a die material for attaining fast heat transfer during solidification has been investigated. their results showed that a faster cooling rate improved the ultimate tensile strength [5]. however, their work did not investigate the effects of cooling rate on corrosion behaviour of the alloy. it has been established that mechanical properties of aluminium alloy increased as the solidification time reduces [6]. it has also been established that castings at faster cooling rate yields high value of yield strength, ultimate tensile strength, ductility, hardness and resistance to impact in the cast [7]. the influence of cooling rate on solidification behaviour of aa2618 aluminium alloy has been examined [8], [9] and [10]. they all concluded that under slow cooling conditions, the alloy was of complex microstructures with lots of eutectic compounds and that increasing cooling rate suppressed the formation of intermetallic al9feni. despite several efforts that have been made for refining microstructure of aluminium alloy casting to improve mechanical properties suitable for application in automobile industry, research effort on the effect of cooling rate on microstructure and corrosion behaviour of 6xxx alloy is rare. hence, this study investigates the effect of cooling rate during casting process on microstructure, mechanical properties and corrosion behaviour of 6xxx-series aluminium alloy. effects of cooling rate on the microstructure, mechanical properties and corrosion resistance of 6xxx aluminium alloy 44 2 materials, equipment and samples preparation 2.1 materials and equipment the materials used in the study were 6xxx-series aluminium alloy, obtained from nigalex, nigeria while the equipment employed in the work were universal testing machine (utm) model fs 50at, muffle furnace, die moulds, pyrometer, brinell hardness tester, charpy impact tester and gamry 1000t potentiostat/galvnostat. 2.2 melting and casting 6xxx aluminium alloy is melted using muffle furnace. prior to pouring, the moulds were treated to four different temperature conditions in order to control the cooling rate. table 1 shows specimens’ identification according to mould condition. a pyrometer was placed close to the moulds cavity to measure the temperature. the temperature data acquired during cooling was used to plot cooling curve. cooling rate curves were obtained by taking the slope at each temperature of time versus temperature curves. 2.3 samples preparation samples were prepared from the cast 6xxx-series aluminium alloy. the chemical compositions of the alloy used is shown in tables 2. the tensile test samples were prepared based on astm e8m 16 [23], with gauge length of 45 mm and radius of 9 mm. the hardness test samples were prepared by cutting a sample of the cast aluminium. the sectioned samples were thereafter ground sequentially with sic paper of different grit paper up to 1200 in accordance with astm e384. the impact samples were machined to 10 mm by 10 mm cross section with a v notch tip radius of 0.5 mm with notch angles of 45°. 2.4 tensile test the test was carried out on universal testing machine (utm) model fs50at with maximum load capacity of 50 kn. the strain rate was 10 -3 /s. tensile force was applied until the sample reached its failure point. the stress strain relationship parameters for each of the sample were obtained and recorded. 2.5 impact test impact test was performed on test specimen machined to a 10 mm by 10 mm cross section with a v notch using a universal impact testing machine model it30 with maximum capacity of 360j±1 (j). the arm of the machine was allowed to swing freely to ensure freedom of movement of the striker. each sample was clamped to the anvil and rigidly tightened by lever at the base of the machine. the pointer was set to zero-energy position and the striker released from a fixed height throughout the procedure. the average of the three energy values absorbed by each sample as indicated by the loose registering pointer on scale were record. 2.6 hardness test the surfaces of the samples were subjected to a compressive load of 0.3 kgf for 15s using shimadzu hmv-2000 micro hardness tester. diamond shaped indenter with square-based pyramid inclined at an angle of 136° between opposite faces was used. three indentation measurements were taken on each sample in different locations and the average was used to evaluate the hardness of the materials. the vickers hardness value (hv0.2) was calculated according to (meyers and chawla, 1999) from equation 3.1. 𝐻𝑉0.2 = 𝐹 𝐴 ≈ 1.8544𝐹 𝑑2 (1) where f is the applied load in kgf, a is the surface area of the resulting indentation in square millimetre and d is the length of the diagonal of the resulting indentation in millimetre. table i: identification of cast specimens specimen cooling method a alloy cooled in mould at room temperature b alloy cooled in mould immersed in ice-block c alloy cooled at mould temperature of 140 °c d alloy cooled at mould temperature of 230 °c table 2: chemical composition of 6xxx aluminium alloy. composition mg si cu cr fe mn zn ti al wt % 0.834 0.594 0.194 0.051 0.182 0.028 0.023 0.016 98.078 agboola, emmanuel and oladoye (2021): international journal of engineering materials and manufacture, 6(1), 43-49. 45 2.7 microstructure specimens for microstructural analysis were prepared by grinding with silicon carbide emery paper and thereafter polishing the samples with grinding and polishing machine qpol 250 m2 followed by etching with diluted hydrofluoric acid while the microstructural analysis was performed using optical microscope olympus model gx71, at 200 magnifications. 2.8 corrosion test corrosion resistance of the as-cast samples was evaluated using a conventional three electrode system consisting of the different aluminium samples as the working electrodes, a graphite rod as the counter electrode and a saturated calomel electrode (sce) as the reference electrode. the working electrode was embedded in the epoxy with an exposed area of 100 mm 2 . pontentiodynamic polarisation experiments were conducted using a gamry interface 1000t potentiostat (gamry instruments, usa). the electrolyte used for the test was 1m hydrochloric acid prepared from concentrated hcl (37 wt.% analytical grade). pontentiodynamic polarisation was conducted at scan rate of 1mv/s from -250 mv vs ocp (open circuit potential) to about -400mv. prior to this test, ocp was conducted for 10 minutes, experiments was repeated minimum two times. 3 results and discussion 3.1 cooling rate evaluation the 6xxx-series aluminium alloy was cooled under four different cooling conditions, and the cooling rate was measured using a thermocouple. a plot of temperature versus time for different cooling modes was plotted as shown in figure 1 and the cooling rate was calculated from the obtained cooling curves. figure 1: cooling curves of 6xxx-series aluminium alloy under different mould temperature. figure 2 a-d shows the graphs of cooling rate versus temperature for 6xxx aluminium alloy cooled under different cooling conditions. from figure 2a-d, it is found that increasing the temperature led to reduction of cooling rate. figure 2a shows the cooling rate curve under slow cooling at room temperature and the average cooling rate was 45°c/s. the overall cooling rate tends to be fast and uniform. figure 2b shows the cooling rate curve under slow cooling in ice –cooled mould. the average cooling rate was 50°c/s. the overall cooling rate in this cooling mode is faster compared with room temperature condition. the cooling rate curve obtained under 140°c cooling condition is shown in figure 2c. as can be seen from the figure, the cooling rate remained steady at average cooling rate of 35°c/min. figure 2d shows cooling rate curve for 230°c. the trend of cooling rate changed in a similar way to cooling at 140°c. however, the cooling rate was 28°c/min. it can be seen that the dt/dt curve, having reached the peak, exhibits a straight line parallel to the horizontal axis. 3.2 microstructure at different cooling rates figure 3 shows the optical microstructures of 6xxx aluminium alloy solidified at different cooling rates. it can be seen that the faster the cooling rate, the smaller the grains and the more refined the microstructure. plate 1 shows the microstructures of 6xxx aluminium alloy under different cooling conditions. plates 1a and 1b shows the microstructures obtained at room temperature and ice cooled conditions respectively. effects of cooling rate on the microstructure, mechanical properties and corrosion resistance of 6xxx aluminium alloy 46 figure 2: cooling rate curve of cast specimen (a) cooled in mould at room temperature (b) cooled in mould immersed in ice block (c) cooled in mould at 140 °c (d) cooled in mould at 230 °c. figure 3: plate 1: microstructure of the 6xxx aluminium alloy under different cooling rates (a) mould was cooled at room temperature (b) mould was cooled in ice block (c) mould was cooled mould temperature 430 o c (d) mould was cooled at 230 o c. agboola, emmanuel and oladoye (2021): international journal of engineering materials and manufacture, 6(1), 43-49. 47 the grain size appears smaller finer and evenly dispersed. plates 1c and 1d shows the microstructure obtained at high temperatures. as can be seen in plates 1c and 1d, the grains appear larger in size, because the alloy remains at high temperature for a long time [14]. hence, recrystallization followed by grain growth occurs. a large number of precipitates appear in the crystal. it can be seen from the above description that there are significant differences in the size and morphology of the crystal grains in the as-cast alloy under different cooling condition. with an increase of cooling rate, finer crystal grains were found in the alloy. 3.3 mechanical tests results figures 4 shows the effects of cooling rate on ultimate tensile strength (uts), hardness and impact strength of 6xxx aluminium alloy. it is seen from table 3 that tensile strength increases with increasing cooling rate. the hardness measurement indicated that ice-cooled samples had higher hardness compared to air-cooled and samples cooled at elevated temperatures. the uts increase from 39.6 to 45.3 mpa as the cooling rate increase. the increase in strength is due to the presence of finer ferrite-pearlite structure. the lowest value of uts recorded in sample cooled at 230 ℃ is due to the presence of coarser pearlite structure [15]. with faster cooling rate, the transformation temperature is lowered resulting in finer pearlite structure. this in turn increase the strength with increase in cooling rate. the impact energy value decreased from 54 kj/m 2 64 kj/m 2 due to increase in cooling rate which led to the formation of finer and harder phases in the microstructure. whereas ice – cooled samples exhibited least impact energy value of 54 kj/m 2 because of harder micro constituents, samples cooled at 230℃ reflected the highest impact energy values on account of the softer and coarser pearlite structures. the higher the cooling rate, the higher the strength of the materials due to fine grains. the grains in the ice-cooled and air-cooled samples were finer and more uniform. this observation agrees with elahetia (2013) that mechanical properties increased with increase in cooling rate. figure 4: variation in ultimate tensile strength uts, hardness and impact strength with cooling rate. table 3: effects of cooling rate on the mechanical properties specimen cooling rate (°c/min) uts (mpa) hardness (hv1) impact strength (kj/m²) a 8.2 108.5 45.3 58 b 19.1 122.6 48 64 c 3.82 93.58 42.3 55.3 d 2.76 76.95 39.6 54 3.4 electrochemical results figures 5(a-d) shows the potentiodynamic polarization curves of the as-cast aluminium alloys cooled under various conditions in 1.0 m hcl. the corrosion properties estimated form the curves are presented in table 2. generally, a high corrosion potential and a low corrosion current density indicates a higher resistance of the material to dissolution in the given electrolyte. from table 3, it can be observed that the higher the cooling rate of the casting, the better the corrosion resistance with the samples cooled in ice block exhibiting the best corrosion resistance. this enhancement on corrosion resistance as cooling rate increased can be attributed to grain refinement. effects of cooling rate on the microstructure, mechanical properties and corrosion resistance of 6xxx aluminium alloy 48 figure 5: potentiodynamic curves for 6xxx aluminium cast samples cooled in (a) air) b) room temperature (b) mould in ice black) c) in mould at 140°c.(d) cooled in mould at 230 °c. table 4: corrosion data of 6xxx aluminium alloy under different cooling conditions. specimen cooling conditions cooling rate (°c/min) i (corr) ma/cm² e (corr) mv a mould maintained at room temperature 8.2 7.83 -729 b mould immersed in ice-block 19.1 1.27 -752 c mould at 140 °c 3.82 4.11 -736 d mould at 230 °c 2.76 8.03 -750 4 conclusions different cooling rates during casting were investigated in order to investigate the effects of cooling rate on the microstructure, mechanical properties and corrosion behaviour of 6xxx-series aluminium alloy. on the basis of the results of the investigation, the following conclusions are drawn: 1. increasing cooling rate resulted in finer and evenly distributed grains. 2. rapidly solidified cast has very good strength which is basically due to finer grains and homogenous microstructures. 3. the corrosion resistance and mechanical properties improved with the increasing cooling rate. 4. the improvement in the corrosion resistance is attributed to the microstructural refinement and chemical homogeneity. agboola, emmanuel and oladoye (2021): international journal of engineering materials and manufacture, 6(1), 43-49. 49 references 1. akhil, s. & sellamuthu, r. (2014). the effect of section size on cooling rate, microstructure and mechanical properties of a356 aluminium alloy casting. advances in manufacturing and materials engineering; pp. 362368. sciencedirect. 2. raja, s. t. (2011). stress corrosion cracking. theory and practice, cambridge, uk: woodhead publishing limited; pp. 608–650. 3. shimizu, n.k. (2014). high resolution sem investigation of intercrystalline corrosion on 6000 series aluminium alloy with low copper content. ecs electrochemistry letters. 4. sinyavskii, u. (2004). on the mechanism of intergranular corrosion of aluminium alloys. protection of metals, 481-490. 5. mohandass, a.s. (2014). the effect of cooling rate on mechanical behavior of bulk cast of a380 aluminium alloy. international journal of engineering and technology, 374-380. 6. liu y.l., liu, m.l. luo l., wang j.j., liu c.z. (2014). the solidification behavior of aa2618 aluminium alloy and influence of cooling rate. materials (basel) 7(12). 7875-7890. 7. american society for testing and materials, astm-g31-72, american society for testing and materials, philadelphia, pa, 2004. 8. xia,y. zhang,b. wang,y. qian,m. geng,l. (2012). mater. sci. eng. c 32 (4) 665– 669. 9. zhang,b., hou,y., wang, x., wang,y., geng,l. (2011) mater. sci. eng. c 31; 1667–1673. 10. ralston,k.d. birbilis,n.(2010); effect of grain size on corrosion: a review, corrosion 66, 1–13. 11. ou, m.g.; zhang, s.; song, h.c.; liang, y.l. (2017) effects of different cooling methods on microstructure and mechanical properties of tc4 alloy; proceedings of the chinese materials conference, yinchuan, china; springer: singapore; pp. 539–547. 12. hichem, f.; rebai, g. (2015); study of dispersoid particles in two al–mg–si aluminium alloys and their effects on the recrystallization. appl. phys. a,119, 1–5. 13. zhang, x.k.; guo, m.x.; zhang, j.s.; zhuang, l.z., (2016); dissolution of precipitates during solution treatment of al-mg-si-cu alloys. metall. mater. trans., 47, 608– 617. 14. elahetia, & maube, s. (2013). effect of short cycle heat treatment and cooling rate on microstructure and chemical properties of recycled aluminium sand casting; a thesis submitted in partial fulfilment for the degree of master of science in mechanical engineering in the jomokenyatta university of agriculture and technology. 15. equbal, m.i., alam, p., ohdar, r., anand, k.a., alam, m.s., (2016); effect of cooling rate on the microstructure and mechanical properties of medium carbon steel; international journal of metallurgical engineering; 5(2): 21-24 international journal of engineering materials and manufacture (2020) 5(3) 68-75 https://doi.org/10.26776/ijemm.05.03.2020.01 s. abdulkareem , r. a. busari, l. a. fashola and i. a. madu department of mechanical engineering, faculty of engineering and technology, p.m.b. 1515, university of ilorin, nigeria. e-mail: sulkarm@yahoo.com reference: abdulkareem, s., busari, r. a., fashola, l. a and madu, i. a. (2020). characteristics of notched high strength materials under tension, torsion and impact loading. international journal of engineering materials and manufacture, 5(3), 68-75. characteristics of notched high strength materials under tension, torsion and impact loading abdulkareem, s., busari, r. a., fashola, l. a and madu, i. a received: 12 april 2020 accepted: 09 june 2020 published: 30 july 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 abstract high carbon steel (aisi 1065) and stainless steel (aisi 304) are high strength materials that are mostly used as wear resistance materials because of their high hardness and toughness. these two materials are widely used for applications in which high strength, hardness and wear resistance are required, and these requirements are fund in cutting tools, springs and surgical instruments. nevertheless, the presence of notch in these materials do affect their service life. this paper reports on the characteristics of notched high carbon steel and stainless steel materials investigated under tensile, torsion and impact loads. the behaviour of the materials was examined under different notch parameters of angle 30°, 45° and 60° and notch base radius of 0.5 mm and 1.0 mm. the tensile, torsion and impact test samples were prepared according to astm e8m, astm f383-15 and astm e23-16b respectively. examination on the tensile and torsion tests were carried out on testometric universal testing machine (tutm), while avery-denison izod impact testing machine was used for impact test. the results obtained for the two materials showed that there is increase in absorption energy and resistance to twisting failure as notch tip radius and notch angle increase. keywords: hardened steels, notch parameters, mechanical properties. 1 introduction high carbon (aisi 1065) and stainless steels (aisi 304) are two types of materials widely used for applications in which high strength, hardness and wear resistance are required particularly in tools steel, dies, cutting tools, springs in manufacturing and automobile industries as well as surgical instruments in medical industries [1-3]. the performance of these material during their service life depends on inherent properties of the materials, loading system, maintenance culture and environmental effects. these factors can be attributed basically to either the design, manufacturing deficiencies and or handling issue [4]. hence, presence of notch which affect the performance of most materials irrespective of their service or loading conditions could be as a result of design/manufacturing problem or handling issue ([5-6]. most engineering components and structures do have notch of various shapes which could be in the form of vshape threads on bolts, surface scratches, key ways grooves on shafts, non-metallic inclusions and corners, fillets and discontinuities in geometrical shapes, cracks in smooth structural components such as round bars, pipes and shells [79]. stress developed by notch of any form do influence the behaviour of materials and the study of notch properties of materials provides information regarding the effects of stress concentrations of varying magnitude which also helps to understanding how stresses influence material performance under service [10-11]. many research works among whom are [12-22], kobayashi et al, 2019; naqiuddin et al, 2017; nath & das, 2006; rittel et al, 2014; rozumek et al, 2006; tlilan et al, 2006; tlilan, et al 2005; todkari et al, 2015; zappalorto & lazzarin, 2011; zehsaz et al, 2010; zhao et al, 2019 have been documented on the effects of notch on materials behaviour. however, documented work on high strength materials such as high carbon (aisi 1065) and stainless steels (aisi 304) are rarely available. hence, the objective of this work is to examine the characteristics of the two high strength steels (high carbon steel and stainless steel) under tensile, torsion and impact loading conditions. the behaviour of the materials were examined under v-shaped notch geometry of different notch parameters of angle 30°, 45° and 60° and notch base radius of 0.5 mm and 1.0 mm. characteristics of notched high strength materials under tension, torsion and impact loading 69 2 materials, equipment and samples preparation 2.1 materials and equipment the materials used in the study were high carbon steel (aisi 1065) and austenitic stainless steel (aisi 304), while the equipment employed in the work were spectrometer model afs 200t, testometric universal testing machine (utm) model fs-50at and avery-denison izod impact testing machine. 2.2 samples preparation samples were prepared from high carbon steel (aisi 1065) and austenitic stainless steel (aisi 304) materials. the chemical compositions of the high carbon steel and stainless steel materials used as shown in tables 1 and 2 respectively were determined using spectrometer model afs 200t. the tensile test samples were prepared based on astm e8m-16 [23], with gauge length of 55 mm and radius of 5 mm. the test was carried out on testometric universal testing machine (utm) model fs-50at with maximum load capacity of 50kn. according to astm f383-15 [24], the torsion test was carried out on sample length of 144 mm, gauge length of 36 mm and radius of 5 mm with the same notch parameters as that of tensile test. the impact test according to astm e23-16b [25] was carried out on an avery-denison izod impact testing machine. the samples were prepared with gauge length of 55mm, diameter of 10mm, and notch tip radii of 0.5 mm and 1.0 mm with notch angles of 30 o , 45 o and 60 o on the two steel samples. a peripheral 30 o , 45 o and 60 o v-notch were in turn prepared at the center of gauge length of all the samples. the schematic of the impact test sample is shown in figure 1. table 1: chemical composition of the high carbon steel (aisi 1065). c si mn s p cr mo ni cu fe 0.652 0.77 0.732 0.043 0.31 0.071 0.052 0.139 0.053 balance table 2: chemical composition of the stainless (aisi 304) steel. cr ni mn si c p s fe 18.21 8.35 1.31 0.53 0.06 0.075 0.019 balance 2.3 notching of materials samples for the two materials (aisi 1065 and aisi 304 stainless steel) were prepared for izod impact test with circular cross-section and contains 30 o , 45 o and 60 o v-notch, 2 mm deep with a 0.5 mm and 1.0 mm root radius for each sample (fig. 1). the samples were supported as overhanging vertical beam and loaded in the front of the notch using swinging pendulum. 2.4 tensile test sample computerized tensile testing machine was used for this experiment. the samples in accordance to astm [23], were prepared according to astm standards (fig. 2). tensile force was applied until the sample reached its failure point. the stress-strain relationship parameters for each of the sample were obtained and recorded. 2.5 torsion test the samples were gripped onto the torsion testing machine using hexagonal sockets and was firmly mounted. both ends of the sample were fitted to input and torque shafts and reading on the torque meter was set to zero. twisting the sample at strain increment of 0.5 was made until failure occurs. average of three readings were taken for the torsion tests carried out on testometric universal testing machine (tutm, model: fs-50at). 2.6 impact test izod impact testing machine (model: 067/05-u-33122) was used for the test. the arm of the machine was allowed to swing freely to ensure freedom of movement of the striker. each sample was clamped to the anvil and rigidly tightened by lever at the base of the machine. the pointer was set to zero-energy position and the striker released from a fixed height throughout the procedure. the average of the three energy values absorbed by each sample as indicated by the loose registering pointer on scale were record. figure 1: schematic of notched sample abdulkareem et al. (2020): international journal of engineering materials and manufacture, 5(3), 68-75 70 figure 2: sample for the tensile test. 3 results and discussion t3.1 tensile test result for the aisi 1065 steel (hcs) the result of the tensile test for the hcs is shown in table 3. the recorded values of yield strength and ultimate tensile strength for the three notch angles (30 o , 45 o and 60 o ) is higher for 0.5 mm notch radius than the values obtained for 1.0 mm notch radius. this observation is not unconnected to the reduction in effective area that come to play at the point of loading during the application of force. the result of the uts for the hcs (table 3) follows the same trend with the result obtained for the yield strength, with the highest ultimate tensile strength of 1622.107 n/mm2 recorded for 0.5 mm notch radius placed at 45 o on the sample. the next to this is 1569.471 n/mm2 uts values recorded for notch tip radius of 1 mm at 45 o . on the other hand, the results of the percentage elongation (table 3) for the 1.0 mm notch radius is higher than that obtained for 0.5 mm notch radius for all the three angles (30°, 45° and 60°) used in the work. the highest elongation of 8.167% was recorded for notch radius of 1.0 mm placed at 45 o . it is expected that the highest elongation will result in highest uts values in the sample, since the highest value of elongation would subject the material to experience more (high) tensile strength before crack initiation which will eventually lead to fracture could occur in the material. however, the occurrence of 1622.107 n/mm2 values of uts at 45o could be as a result of presence of high stress raiser at base of at 45o angle. the plots of stress versus strain at 45o with 0.5 and 1.0 mm radius that give the highest yield and ultimate tensile strength are shown in figure. 3. it can be observed from fig. 3 that the hcs display less ductility as compare to the stainless steel because of the presence of high percentage carbon content. the effect of the carbon contents in hcs could have a significant impact in the fracture of the materials since high carbon contents increases the hardness of the material which may likely make the material stronger thereby resulting in high ultimate tensile strength. it was noticed that failure of the sample occurs at the notched point due to tensile loading, this occur because of higher stress concentration at the notched point. table 3: tensile test result for aisi 1065 steel (hcs) 30 o 45 o 60 o 0.5 mm 1.0 mm 0.5mm 1.0 mm 0.5 mm 1.0 mm yield strength (n/mm 2 ) 1150.321 1035.677 1522.107 1469.471 1253.784 1143.064 uts (n/mm 2 ) 1250.474 1182.381 1622.107 1569.471 1353.784 1243.064 elongation (%) 5.441 5.936 7.013 8.167 5.100 6.282 (a) (b) figure 3: stress against strain of hcs at 45° notch angle and (a) 0.5 mm, (b) 1.0 mm tip radius characteristics of notched high strength materials under tension, torsion and impact loading 71 3.2 tensile test result for the aisi 304 (stainless steel) table 4 shows the tensile result for stainless steel (aisi 304) samples. the highest yield strength of 1788.293 n/mm2 was recorded with notch radius of 1.0 mm placed at 60 o on the sample, while the corresponding highest ultimate tensile strength of 2028.525 n/mm2 was recorded with the same notch parameter. contrary to the results of tensile test and ultimate tensile strength obtained for the hcs (table 4), the results of yield strength and ultimate tensile strength recorded for stainless steel (aisi 304) is higher for 1.0 mm notch radius than the values obtained for 0.5 mm notch radius for the three notch angles of 30 o , 45 o and 60 o . the highest percentage elongation of 7.702 % was recorded at 60 o notch angle with 1.0 mm radius. the behaviour of stainless steel at elevated temperature (strain hardening in this case) whereby the steel resist loading action resulting in higher elongation before fracture. furthermore, the 60 o and 1.0 mm notch parameters which give high notch angles and tips radius have the high absorption energy due to the fact that the sample has more area at the root tip which is likely not be easy for crack to be initiated and when eventually it is initiated, the crack will cover a large area before the material is fracture, hence results in higher absorbed energy. the plots of stress against strain at 60 o notch angle with 0.5 and 1.0 mm radii that give the highest ultimate tensile strength are shown in figure 4, it can be observed from figure. 4 that the stainless steel (aisi 304) sample display better ductility property before fracture as against the hcs sample. table 4: tensile test result for aisi 304 steel (stainless steel) 30 o 45 o 60 o 0.5 mm 1.0 mm 0.5 mm 1.0 mm 0.5 mm 1.0 mm yield strength (n/mm 2 ) 1450.121 1697.129 1567.259 1741.947 1486.281 1788.293 uts (n/mm 2 ) 1690.353 1937.361 1807.491 1982.179 1726.513 2028.525 elongation (%) 5.158 6.017 7.417 7.567 6.536 7.702 (a) (b) figure 4: stress against strain for stainless steel at 60° notch angle and (a) 0.5 mm, (b) 1.0 notch tip radius 3.3 torsion test the results of the torsion tests for the samples of aisi 1065 and aisi 304 steels are shown in figures 5 and 6. it can be observed (figures 5 and 6) that the effect of notch radius does not have a significant difference as the values obtained for the 0.5 and 1.0 mm radii are very close for the two materials. the torsion results for the two materials show that as notch angle increase with notch tip radius, the higher the torque required to twist the steels. the larger the notch angle and tip radius, the higher the torque that is required to twist the steel, this simply means that lower notch tips radius and smaller notch angle will have low resistance to twisting forces due to the fact that the sample has smaller area at the root tip which makes it easier for the crack to be initiated unlike that of larger tip radius and larger notch angle where the crack initiation has larger area to contend with, before it can be initiated hence results to more resistance to twisting. abdulkareem et al. (2020): international journal of engineering materials and manufacture, 5(3), 68-75 72 (a) hcs at 30° notch angle, 0.5 mm and 1.0 mm notch radius (b) hcs at 45° notch angle, 0.5 mm and 1.0 mm notch radius (c) hcs at 60° notch angle, 0.5 mm and 1.0 mm notch radius figure 5: effect of notch parameters on aisi 1065 steel (hcs) characteristics of notched high strength materials under tension, torsion and impact loading 73 (a) stainless steel at 30° notch angle, 0.5 mm and 1.0 mm notch radius (b) stainless steel at 45° notch angle, 0.5 mm and 1.0 mm notch radius (c) stainless steel at 60° notch angle, 0.5 mm and 1.0 mm notch radius figure 6: effect of notch parameters on aisi 302 steel (stainless steel) 3.4 impact test tables 5 to 7 show the results of impact tests for the high carbon steel (hcs) and stainless steel (ss) workpiece samples. it can be observed from the tables (tables 5 to 7) that the absorbed energy of the materials increase with increase in notch radius and notch angles for the two steels. it was also noticed that failure of the samples occurs at the notched point due to the impact loading, this occurs because of higher stress concentration at the notched point. further observation in table 5-7 shows that lower notch tips radius and smaller angles have the lowest absorption energy. this happens because the sample has smaller area at the root tip which makes it easier for crack to be initiated unlike that of larger tip radius and larger notch angle which the crack initiation has larger area to cover before it can abdulkareem et al. (2020): international journal of engineering materials and manufacture, 5(3), 68-75 74 be initiated hence resulting in higher absorbed energy. carbon contents with respect to the aisi 1065 steel also plays a major role in the failure of the material because higher carbon contents is likely to increase the hardness of the material which make the material stronger and to absorbed more energy before failure. table 5: absorption energy at notch angle of 30° notch tip radius (mm) absorption energy (joules) aisi 1065 aisi 304 0.5 128 114 1.0 162 119 table 6: absorption energy at notch angle of 45° notch tip radius (mm) absorption energy (joules) aisi 1065 aisi 304 0.5 162 122 1.0 170 128 table 7: absorption energy at notch angle of 60° notch tip radius (mm) absorption energy (joules) aisi 1065 aisi 304 0.5 173 128 1.0 178 132 4 conclusions investigation on the characteristics of notched aisi 1065 and aisi 304 steels with respect to tension, torsion and impact loading has been carried out, and based upon the findings from the experimental work the following conclusions can be drawn: 1. high notch tip radius of the samples improves the absorption energy of the steel samples. 2. steel samples with bigger notch angle tend to have higher absorption energy under sudden load. 3. as the notch tip radius increases the sample show more resistance to twisting thus requiring more torque for twist to occur. 4. a high notch tip radius leads to higher ultimate tensile strength of the material before failure will occur. acknowledgement the authors would like to appreciate the following staff of the university of ilorin for their assistance during the study. mr. m. ndagi of the department of mechanical engineering and mr. ibrahim lateef, central workshop of the faculty of engineering. references 1. callister jr, w.d & rethwisch, d.g. (2012). fundamentals of materials science and engineering: an integrated approach”. john wiley & sons. 2. singh, r., chauhan, s & gope, p.c. (2016). influence of notch radius and strain rate on the mechanical properties and fracture behavior of tig-welded 6061 aluminum alloy. archives of civil and mechanical engineering, 16(3), 513-523. 3. antunes, f.v., branco, r., prates, p & costa, j.d. (2019). fatigue crack growth in notched specimens: a numerical analysis. frattura ed integrità strutturale, 13(48), 666-675. 4. altenhof, w., zamani, w.n., north, w & arnold, b. (2004). dynamic stress concentrations for an axially loaded strut at discontinuities due to an elliptical hole or double circular notches. international journal of impact engineering, 30(3). 255-274. 5. majzoobi, g.h & daemi, n. (2010). the effects of notch geometry on fatigue life using notch sensitivity factor. transactions of the indian institute of metals, 63(2–3), 547–552 6. eskandari, j., abolghasemzadeh, m., salavati, h & alizadeh, y. (2014). the effect of notch tip position on the charpy impact energy for bainitic and martensitic functionally graded steels”. materials strength, 46(5), 700–716. springer international publishing ag. http://link.springer.com/journal/11223 characteristics of notched high strength materials under tension, torsion and impact loading 75 7. sobieraj, m.c & rimnac, c.m. (2019). fracture, fatigue, and notch behavior of peek”. in peek biomaterials handbook. william andrew publishing, 67-82. 8. torabi, a.r & kamyab, m. (2019). the fictitious material concept. engineering fracture mechanics, 209, 17-31. 9. torabi, a.r & kamyab, m. (2019). notch ductile failure with significant strain‐hardening: the modified equivalent material concept. fatigue & fracture of engineering materials & structures, 42(2), 439-453. 10. charde, s.r., ballal, a.r., peshwe, d.r., mathew, m.d and paretkar, r.k. (2013). effect of notch on creep behavior of 316l(n) ss”, 6th international conference on creep fatigue and creep-fatigue interaction [cf-6] procedia engineering vol. 55, 517–525. sciverse 11. gbadebo, o., oluwamayowa, o., oluwakayode, b., adewale, o & horace, w. (2015). the effects of notch size and material microstructure on the notch sensitivity factor for notched components. engineering fracture mechanics, 145, 181-196 12. kobayashi, s. ogou., s & tsurekawa., s. (2019). grain boundary engineering for control of fatigue fracture in 316l austenitic stainless steel. materials transactions, 60(5), 623-630. 13. naqiuddin., z.m., rahman, n.a., jaini, z.m & shamila, b.n. (2017). effect of notch position on fracture energy for foamed concrete. in materials science and engineering conference series 271(1), 012-019. 14. nath, s.k & das, u.k. (2016). effect of microstructure and notches on the fracture toughness of medium carbon steel. journal of naval architecture and marine engineering, 3(1), 15-22. 15. rittel, d., rotbaum, y., rodríguez-martínez, j.a., sory, d & zaera, r. (2014). dynamic necking of notched tensile bars: an experimental study. experimental mechanics, 54(6), 1099-1109. 16. rozumek, d., macha, a., lazzarin, p & meneghetti, g. (2006). influence of notch (tip) radius on fatigue crack growth rate. journal of theoretical and applied mechanics, 44, 127-137. 17. tlilan, h.m., sakai, n & majima, t. (2006). effect of notch depth on strain-concentration factor of rectangular bars with a single-edge notch under pure bending”. international journal of solids and structures, 43(3-4), 459474. 18. tlilan, h.m., yousuke, s & tamotsu, m. (2005). effect of notch depth on strain-concentration factor of notched cylindrical bars under static tension”. european journal of mechanics-a/solids, 24(3), 406-416. 19. todkari, t.k., swami, m.c & patil, p.s. (2015). effect of notch angel on the fracture toughness of al7075 t6 alloy–an experimental approach. iosr journal of mech civil eng, 12(1), 1-5. 20. zappalorto, m & lazzarin, p. (2011). strain energy-based evaluations of plastic notch stress intensity factors at pointed v-notches under tension. engineering fracture mechanics, 78(15), 2691-2706. 21. zehsaz, m., hassanifard, s & esmaeili, f. (2010). fatigue life estimation for different notched specimens based on the volumetric approach. in epj web of conferences 6, (42001). edp sciences. 22. zhao, y., peng, x., huang, c., fu, t., yang, b., hu, n & yan, c. (2019). notch effects on deformation of crystalline and amorphous aln–a nanoscale study. ceramics international, 45(1), 907-917. 23. american society for testing and materials (2016). standard test methods for tension testing of metallic materials. west conshohocken, pa, astm international. 24. american society for testing and materials (2014). “standard test method for material hardness. astm international. 25. american society for testing and materials (2014). “standard test methods for impact loading astm international. https://www.sciencedirect.com/science/article/abs/pii/s0013794415001149#! https://www.sciencedirect.com/science/article/abs/pii/s0013794415001149#! https://www.sciencedirect.com/science/article/abs/pii/s0013794415001149#! https://www.sciencedirect.com/science/article/abs/pii/s0013794415001149#! https://www.sciencedirect.com/science/article/abs/pii/s0013794415001149#! https://www.sciencedirect.com/science/journal/00137944 https://www.sciencedirect.com/science/journal/00137944 https://www.sciencedirect.com/science/journal/00137944/145/supp/c international journal of engineering materials and manufacture (2018) 3(3) 134-142 https://doi.org/10.26776/ijemm.03.03.2018.02 development of non-contact liquid level measurement and data storage system muhammad mahbubur rashid, abdullah al mamun, abdul hassan jaafar and md. sajib mollik received: 10 may 2018 accepted: 16 july 2018 published: 15 september 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract the normal contact type liquid measurement devices have some drawbacks since they have potential damage due to the sensor fouling or corrosion since those are continuously exposed to the liquid. especially flash flood may cause the damage of liquid level sensor. so that, it is important to design a non-contact device for liquid level measurement in order to avoid this constrain. distance can be measured without contact such as laser, ultrasonic and radar. in this research, ultrasonic sensor is used to provide non-contact feature of the device since it is low cost and uses ultrasound waves rather than light. this vital sensing device is able to sense uneven surfaces, liquids, clear objects, and objects in dirty environments. this paper discussed the measurement of liquid level in a tank as well as storing historical data. keywords: no-contact, ultrasonic sensor, liquid level measurement 1 introduction this project is aimed at designing a device that can provide non-contact level measurement of a liquid tank. the meaning of non-contact here is that the device, which is used, for liquid level measurement is not put directly in liquid. therefore, it will reduce the potential damage of device due to the sensor fouling or corrosion while it continuously exposed to the liquid. the damage might also occur because debris when there is flood. besides, the non-contact device also allows for easy installation on a bridge or structure over the liquid as safe and easy position. to provide non-contact feature of the device, ultrasonic sensor is used since it uses sound waves rather than light. it has different sensing capability like as uneven surfaces, liquids, clear objects, and objects in dirty environments. the cone-shape wave sound has transmitted by ultrasonic sensors where wave through in air. these sound pulses make echo and sound come back from the liquid surface and are in turn received by the sensor, which measures the time interval between the transmitted and received signal. electronics device can be measured this distance based on sound speed where it in air [6]. additionally, distance can be measured various way like as laser and radar. however, because of their expensive price, they are only set on the minority of instruments. thus, the research of the distance measurement system that consider the high ratio of ability and decreased value has ended at ultrasonic sensor. 9v battery has been used for pic microcontroller power, a 2x16 liquid crystal display (lcd), and two maxsonarez1 ultrasonic sensor. with a lcd, it will immediately display the height of the liquid level. with the rs232 personal computer (pc) link and windows software, the data also can be logged into pc and a graph of the liquid level can be plotted. the proposed sensor is low-cost and reliable would be a useful device to measure the liquid level in a tank either at homes, open channel and waste reservoir. it also might be a prodigious agreement and required for the budding buyers. m. m rashid1 ,abdullah a. mamun2, abdul hassan b jaafar3, md. sazib mollik4 1, 4department of mechatronics engineering 2department of civil engineering 3department of mechanical engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia 1e-mail: mahbub@iium.edu.my, 2e-mail: mamun@iium.edu.my 3e-mail: aseuia@gmail.com, 4e-mail: sajib013@hotmail.com reference: rashid, m. m., mamun, a. a., jaafar, a. h. and mollik, m. s. (2018). development of non-contact liquid level measurement and data storage system. international journal of engineering materials and manufacture, 3(3), 134-142. development of non-contact liquid level measurement and data storage system 2 overview of sonar system sound navigation and ranging (sonar) is a technique that uses sound propagation to steer, interconnect with or sense other vessels. sonar might be used as a means of aural location and measurement of the echo characteristics of object in the liquid. before the introduction of radar, acoustic location in air was used. there are two types of sonar technology which are passive and active sonar. passive sonar devices will only receive the signal without transmit any signal. it is often used in military settings and in science applications such as fish location and various marine environments. on the other hand, active sonar device consists of a sound transmitter and receiver. a wave of sound could be called a "ping" is created, and then echo or reflections of the pulse will be measured. sonar projector has been generated sound wave by electronically. signal generator, power amplifier and electro-acoustic transducer has been used for this projector. sonar system had generated sound frequency from lower level to extremely high level. humans are able to hear sound frequency from 20khz to 20,000 khz, where ultrasonic sound frequency range is higher. music and common sounds that are considered pleasant are typically 12 khz or less. ultrasonic waves consist of frequencies which is larger than human lower frequency and it is exist in excess of 25 mhz and this range have used for several applications such as including plastic welding, medicine, jewelry cleaning, and nondestructive test. in nondestructive test, ultrasonic sound frequency has ability to travel in deep “see through" for detecting solid material or any other surface without affecting the material harmfully [1]. the flowchart for appropriate selection of ultrasonic sensor is given below [6]: 3 system design 3.1 system architecture in figure 3, a block diagram of the whole system architecture is presented. the system consists of a pic 16f877 microcontroller, two ultrasonic sensors, and a lcd for display. the system also provides a serial communication between the microcontroller and personal computer. the pic microcontroller will continuously take the analog signals from the sensors and will directly convert them to digital signal. in this system, no external analog to digital (adc) is needed since it is already built in the pic microcontroller. 3.2. liquid level calculation the value that input by the sensors is the distance between the sensor and the liquid level and is denoted by d1 as shown in the figure below. so that, a calculation is needed in order to get the true liquid level of the tank and denoted as d2. the calculation is as follow: d1 + d2 + 50 = 650 [cm] (1) so that, liquid level = d2 = 600 d1 [cm] (2) it is also very important to note that the values that given by the analog port of the pic microcontroller are not directly show the liquid level. it needs to multiply by a constant and in order get this constant, a simple calibration needs to be done. first, the sensor will put 50 cm above the liquid level or in other words when the liquid is full tank. the constant that need to be multiplied by current reading then calculated. figure 1: principle of active sonar 135 rashid et al., (2018): international journal of engineering materials and manufacture, 3(3), 134-142 figure 2: flowchart for selecting an ultrasonic sensor for a specific selection. figure 3: system architecture 136 development of non-contact liquid level measurement and data storage system figure 4: liquid level measurement 3.3 hardware components 3.3.1 microcontroller microcontroller would be used for controlling purpose which is pic16f877. data acquisition system will take data from sensors, convert them to analog, calculate the liquid level, and display on lcd as well as on the personal computer. the pic16f877 has a 25 mhz processor and this compiler runs the processor at 20 mhz, where it has 33 input and output pins, flash program memory (8k*14words), ram (368*8bytes), eeprom (256*8bytes). this microcontroller runs the program form its own memory because it does not have any operating system. additionally, pic16f877 has several hardware features such as an analog to digital converter (adc), interrupts, timers, and capture/compare/pwm channels. figure 5: pic microcontroller 137 rashid et al., (2018): international journal of engineering materials and manufacture, 3(3), 134-142 3.3.2 the max sonar-ezi ultrasonic sensor the maxsonar ez1 has specific detection range which is very short to long-range. moreover, it required ultra-low power consumption. it has explicit object detection range, where the range starts from 0-inches to 254-inches and offers sonar range information from 6-inches out to 254-inches with 1-inch resolution. objects from 0-inches to 6inches range as 6inches. it has pulse width output, analog voltage output, and serial digital output for interface with output. the specifications of the sensor are given in the table below (maxbotix, 2006). for any ultrasonic range finder, the beam width is a function of the sensor used and the system gain following the sensor. gain capability of the maxsonar ez1 is actively and continuously adjusted with its system software where it has a long comparatively narrow beam. figure 6 shows the specification of the maxsonar ez1. majority of the objects are detecting in the central 36-degree zone. the authentic detection zone is look like a cone that extends from the front of the detector face (maxbotix, 2009). table 1: the maxsonar-ezi sensor specification parameter value width 19.9 mm length 22.1 mm weight 4.3 grams range 6.45 meters power supply 5 v output analog figure 6: maxsonar ezi sensor figure 7: target detection angle of ultrasonic sensor (photo credit: maxbotix). 138 development of non-contact liquid level measurement and data storage system 3.3.4 lcd display a (2x16) liquid crystal display (lcd) is used to immediately display the reading from ultrasonic sensors. two lines of the display space are suitable for the project since there two sensors reading. a total of 7 i/o pins of the pic microcontroller are used to communicate with the lcd. the specifications of the lcd display are given in the table below. 3.4 software code development 3.4.1 pic microcontroller programming flowchart the pic microcontroller programming will be developed in c language and its flowchart is shown in the figure below. when the system is on, immediately the lcd will be initialized. the system then will take reading from ultrasonic sensor through analog pins of the pic microcontroller and convert them to digital. after that, the level of the liquid will be calculated and the result will be display on lcd as well as on personal computer. 3.4.2 pcw c compiler pcw c compiler is a most effective software for design and write the programming code of the project in c++ language. after writing a vital code for the sensor then it is essential to compile this code as a .hex file and upload this file into the microcontroller. most benefits of this compiler is to provide higher level programming designer to solve their problem faster and more efficient. 3.4.3 pic bootloader + pic bootloader + has a specific role which is being used to download the .hex file of the source code into pic microcontroller. this software has a window to display the output of the code. the original of the bootloader was made by petr kolomaznik (czech republic). pic boot plus is based on the delphi sources (1.0.8.0 25.7.2001) provided by (c) 2000-2001 ehl elektronika. all enthusiasts developing pic applications are free to use this software. table 2: lcd specification parameters value display 16 characters x 2 lines operating temperature 0°c to 50°c operating voltage 4.5v 5.5v backlight voltage 5.0v (100ma) module size 80mm x 36mm x 13.5mm viewing area 64.5mm x 14.5mm mounting hole (diameter) 2.9mm figure 8: 2x16 lcd display. 139 rashid et al., (2018): international journal of engineering materials and manufacture, 3(3), 134-142 figure 9: programming flowchart. figure 10: pcw c compiler. 140 development of non-contact liquid level measurement and data storage system figure 11: pic bootloader+ interface. 4 results and discussions firstly, there was a big challenge of using ultrasonic sensor to measure the level of liquid, because it was required to know the how many percent of signal is bounce back to sensor. the surface of the liquid is not suitable reflector of the transmitted signal. for that reason, a piece of polystyrene board (solid surface) is placed on the surface of the liquid as shown in the figure 4. this will make the surface of liquid work as solid surface. in system design part, it is shown how the level of the liquid in a tank is calculated. however, the value given does not present the real level of the liquid in centimeter (cm) unit rather than it shows the corresponding value to the voltage change. it is important to note that the value that comes from the analog port of microcontroller is always proportional to the distance of sensor from the liquid surface. after some experiments, we found that in order to get the liquid level in cm, the reading needs to be multiplied by 6.25 as below: liquid level = analog reading x 6.25 (3) furthermore, the maxsonar-ez1 ultrasonic sensor has some limitations that need to be considered when use it. in figure 6, we can see that objects are detected mostly in the central 36 degree zone. so that, the sensor must be put freely without any obstacle in this region to make sure that it gives the correct value. the obstacles can be the wall of the liquid tank or other sensor that put close together. in addition, it should be noted that the sensor is not effective for the range below approximately 30 cm to 40 cm. any measurement below this range should be avoided. 5 conclusions the objective of this project is to design and implement an ultrasonic sensor based liquid level measurement system. however, due to the sensor limitation, the maximum allowable height of the tank is only up to 6 meters. but changing sensor type, range can be increased accordingly. this research showed: 1. the system is able to detect liquid surface (polystyrene) within the sensing range. 2. the system can calculate the liquid level with accepted accuracy. 3. the system can also communicate with pc through its serial port and a real time graphs is formed. 4. the system provides a lower cost and effective solution for noncontact type level measurements and historical data storage. in addition, beside liquid level measurement, the device has numerous applications such as in automatic guided vehicles, measuring objects distances, and measuring the depth of pools or banks. it also can serve as a motion detector in production lines. the ultrasonic distance measurement has the great capability to adapt to various 141 rashid et al., (2018): international journal of engineering materials and manufacture, 3(3), 134-142 circumstances and ambient conditions since it is a noncontact detection mode. so it does not get much influenced by ray, temperature, color etc. so that, despite drawbacks as discussed before, we find the main features of the device will be useful. acknowledgement the authors would like to thank international islamic university malaysia for supporting this research through research project titled “development of an integrated water-level sensor and data logger system” (edw b 080283). references 1. national instrument (2010). fundamentals of ultrasonic imaging and flaw detection, national instrument. http://www.ni.com/white-paper/3368/en/ 2. john, j. l. & hugh, f. d-w (1992). directed sonar sensing for mobile robot navigation, kluver academic publishers, chapter 2. 3. jaime, f., julio, s. m. & carlos, c. (1997). an experiment model for sonar sensors. dept of industrial electronics, university of minho, guimardes, portugal. 4. maxbotix (2006). www.maxbotix.com, usa, 2006. 5. satish, p., dharmendra, m., anchal, s., atul, s., shukla, r. k. (2008). ultrasonic obstruction detection and distance measurement using avr micro controller, department of physics, university of lucknow, lucknow, india. 6. itrc (1998). liquid level sensors and data logger testing and demonstration, irrigation training and research centre, california polytecnic state university, san luis obispo. 7. zahirul, a. a.h.m., lawal, w. a., khan, s., rashid, m. m. (2009). design of multi-valued quaternary based analog-to-digital converter. american journal of applied sciences, 6(8), 1521-1525. 8. a. h. m., islam, md. r., khan, s., rashid, m. m. (2009). microelectrical mechanical systems switch for designing multi-band antenna” journal of computer science, 5 (7), 479-486. 9. jahirul, m. i., saidur, r., masjuki, h. h., kalam, m.a., rashid, m. m. (2009). application of artificial neural networks (ann) for prediction the performance of a dual fuel internal combustion engine. transactions hong kong institution of engineers, 16(1), 14-20. 10. ogbonnaya, o. c., singh, d. & ohakwe, j. (2011). significant predictors of library use by new international students: the case study of university of malaya, kualla lumpur. malaysia asian journal of applied sciences, 4 (1), 53-62. 11. m. r. mosavi (2011). applying genetic algorithm to fast and precise selection of gps satellites asian journal of applied sciences, 4(3), 229-237. 142 http://www.maxbotix.com/ international journal of engineering materials and manufacture (2020) 5(4) 148-155 https://doi.org/10.26776/ijemm.05.04.2020.04 akhil punneri madathil 1 , siddarth krishnaraja achar 1 , vinutha moses 1 , ujwal shreenag meda 1 , n chetan2, c vidya1, lourdu antony raj 1 and manjula sarode 1 1 department of chemical engineering, rashtreeya vidhyalaya college of engineering bengaluru-560059, india 2 department of iem, dr ambedkar institute of technology bengaluru-560056, india e-mail: vinuthamoses@rvce.edu.in reference: akhil punneri madathil, siddarth krishnaraja achar, vinutha moses, ujwal shreenag meda, n chetan, c vidya, lourdu antony raj and manjula sarode (2020). use of keratin present in chicken feather as a hydrogen storage material: a review. international journal of engineering materials and manufacture, 5(4), 148-155. use of keratin present in chicken feather as a hydrogen storage material: a review akhil punneri madathil, siddarth krishnaraja achar, vinutha moses, ujwal shreenag meda, n chetan, c vidya, lourdu antony raj and manjula sarode received: 12 september 2020 accepted: 07 october 2020 published: 20 october 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 abstract global warming is the major consequence of pollution. the pollutants that contribute to global warming are commonly known as greenhouse gases. the world has seen an increase in the carbon dioxide concentration over the past few years. the largest sources of carbon emission are the combustion of fossil fuels. the concept of “green clean energy” raised on a mission to reduce the release of these hazardous emissions. hydrogen is one of those clean energy fuel which helps in solving the present crisis. materials such as chicken feathers can be used as a medium to store hydrogen. several research studies are reviewed where chicken feathers are thermally treated by the method of pyrolysis to make them a novel material for hydrogen storage. the uniqueness in the structure and properties of chicken feather is it contains 90% of keratin fibre when heated increases its micropore volume that results in higher hydrogen uptake. keywords: hydrogen, chicken feather, keratin fibre, structure, pyrolysis, clean energy. 1 introduction the requirement for energy is rising exponentially day by day, but there is no sufficient conventional source of energy that can support this demand. the conventional energy sources like oil, gas and coal are fossil fuels [1] which deteriorate the environment drastically, burning of them will produce large amounts of greenhouse gases and other pollutants. carbon dioxide, a major greenhouse gas concentration in the atmosphere has steadily increased to 405.25 ppm in 2016 [2], making 2016, one of the hottest year ever recorded is shown in figure1 [2, 3]. people are trying to find various solutions to this crisis, one being usage of more clean energy fuels like solar, wind, bio, hydro, geothermal, ocean and hydrogen energy [4]. 1.1 hydrogen as energy hydrogen can be generated from clean and green sources and its energy content is very high (120 mj/kg). this makes hydrogen one of the most potential fuel for the future. hydrogen can be generated from numerous sources like water (by thermochemical spitting, photovoltaic cell and photo chemical reaction), glycerol, biomass and other sources (urea, electrohydrogenesis from organic material, cheese whey, hydrogen sulphide) [5]. there are also several disadvantages of hydrogen like, its low energy density (high pressure has to be applied to store large mass of hydrogen in a small space), its difficulty in liquefaction (temperature less than 22 kelvin), its high flammability, hydrogen embrittlement (when stored in a high pressure steel tank) [6]. the liquefied hydrogen or pressurized hydrogen (above 35 mpa) has densities that are 10 and 30 times lower than the ambient gasoline density [8]. hydrogen can be stored in numerous ways like compression, liquefaction, physio sorption in microporous carbon, metallic hydride and complex hydrides [7]. akhil et al. (2020): international journal of engineering materials and manufacture, 5(4), 148-155 149 figure 1: concentration change in co2 over a timespan [2]. figure 2: parts of chicken feather [12] the various microporous carbon materials are carbon nanotubes, activated carbon, graphite, carbon nanofibers and metal organic framework. one of the prominent methods in physio sorption is usage of chicken feathers as carbon source. this material is highly porous and has high surface area which contributes to higher physio sorption [8]. major component of chicken feather is keratin which helps in trapping the hydrogen gas. keratin when heated hardens and it attains a structure comparable to carbon nanotubes. the amount of hydrogen stored in keratin is similar to that of expensive carbon nanotubes [9]. several tons of keratin waste are produced annually from poultry farm making their disposal very tedious. various reducing agents are used to chemically treat these waste chicken feathers, they are also degraded chemically and physically by naoh and heat treatment [10]. 1.2 structure of chicken feather poultry feathers are a cheap and renewable source of fibre that contain about 90% keratin protein [12]. statistics show that every year the world produces more than 4 billion pounds of chicken feather [14]. the uniqueness in the structure and properties of chicken feather makes them preferable for several applications like textile products, films, composites and energy storage source [16]. the density of chicken feathers is about 0.8 g/cm 3 which is lower than other sources of fibre such as cellulose (1.5 g/cm 3 ) fibre and wool (1.3 g/cm 3 ). their low density, high mechanical strength, hydrophobicity, high flexibility and structural interaction with other fibres helps to develop new products of very rare and unique properties contrary to natural or synthetic fibres [12, 13]. the chicken feather consists of three primary units. the rachis (about 7 cm in length) forms the central axis. this central axis is attached to the calamus (present at the base). the secondary structure consists of barbs which are attached to the rachis. their length varies along the central axis (from 1 to 4.5 cm). barbs are usually longer at the base and shorter toward the tip, as shown in figure 2. the keratin has β-pleated and α-helix sheet structure as shown in figure 3 that includes about 20 amino acids, mainly of cysteine. its structure consists of a central carbon linked to functional groups (amine, -nh2, and carboxylic acid, -cooh), the hydrogen atoms and the group r (sulphur) [15]. by “slow pyrolysis” and other chemical treatment methods, the properties of chicken feathers can be improved and modified. slow pyrolysis is one of the heat treatments well known and commonly used to obtain carbon in a controlled monitored environment, time, and temperature. during this process volatile components from carbonaceous material are released. these organic substances are a waste in the form of co2 are returned to the environment [17]. figure 3: (a) α-helix and (b) β-pleated sheet structure [16]. a b use of keratin present in chicken feather as a hydrogen storage material: a review 150 2 materials, equipment and samples preparation there are several thermo-chemical processes such as gasification, combustion, hydrogenation, liquefaction and pyrolysis which are used to convert the raw material into energy products. pyrolysis method of conversion is important since they convert the raw materials directly into solid, liquid, gaseous products by thermal decomposition in the absence of oxygen. there are three broad methods of pyrolysisslow, intermediate and fast. slow pyrolysis is incorporated to process the chicken feather because it leads to less liquid and gaseous product and more of char production [18]. the keratin fibres present in the chicken feathers forms cross-links when heated which strengthens its structure and enhances its porosity thereby increasing the surface area. chicken feathers are obtained from various sources like poultry farms and they are separated into rachis and ramus. the general process of pyrolysis of chicken feather proposed by richard p. wool et al. [19].is as shown in figure 4. iliana giraldo et al. (2013) [9], cleaned the rachis chicken feather and dried them at temperature 50 o c and chopped into fine lengths. the chopped pieces were heated at 250 o c, 350 o c and 450 o c for 24 hours in nitrogen atmosphere. the resulting activated carbon was filtered using the mesh of size 0.27-0.55 mm and dried for 24 hours at 105 o c. the sample was again heated at a rate of 5 o c/min in nitrogen atmosphere from room temperature to final activation temperature. distilled water was used to wash the activated carbon till a constant ph value is obtained. erman senoz et al. (2009) [20], obtained chicken feathers that were already separated from the quill. the pyrolysis was conducted in a thermolyne type f6000 box furnace with a capacity of 861 in 3 with a constant nitrogen flow for 3 hours to get pyrolysed chicken feather fibre (pcff). the samples were heated in a two different ways. the first five samples were isothermally heated at a rate of 3 0 c/min to 215 0 c for 2, 4, 10, 15 and 24 hours respectively as shown in table 1 and the variation in residue fraction is as shown in figure 5. the next six samples were pyrolysed in a two-step process, firstly, heated at a low temperature at 215 o c or 220 o c for a desired time and a constant rate (3 o c/min). later these samples were again heated to a higher temperature (400 o c, 450 o c or 500 o c) for an hour. there were two more samples that were heated at 400 o c for 1 hour and 220 o c for 24 hours respectively as shown in table 2. the graph generated from the available data of residue fraction is shown in the figure 6. figure 4: (a) overall pyrolysis process proposed by richard p. wool et al. [19], (b) thermolyne type f6000 box furnace [21], (c) pyrolysed chicken feather [22]. table 1: single step pyrolysis at constant temperature and varying time [20]. sample pcff temperature 0 c i rate 0 c/min time hour residue fraction 1 215 3 2 0.767 ± 0.019 2 215 3 4 0.722 ± 0.012 3 215 3 10 0.638 ± 0.016 4 215 3 15 0.626 ± 0.011 5 215 3 24 0.601 ± 0.015 a b c akhil et al. (2020): international journal of engineering materials and manufacture, 5(4), 148-155 151 table 2: the pyrolysis parameter with adsorption capacity [20]. sample pcff rate-1 0 c/min t1 0 c t1 hour rate-2 0 c /min t2 0 c t2 hour residue fraction adsorption capacity 6 3 215 24 3 400 1 0.176 ± 0.015 best 7 3 220 24 2 450 1 0.101 ± 0.020 best 8 3 220 32 2 450 1 0.063 ± 0.010 best 9 3 400 1 0.209 ± 0.007 medium 10 3 220 5 3 400 1 0.212 ± 0.018 best 11 3 215 24 3 low 12 3 220 26 2 0.004 ± 0.001 medium 13 3 220 24 0.617 ± 0.022 low 0 2 4 6 8 10 12 14 16 18 20 22 24 26 0.55 0.60 0.65 0.70 0.75 0.80 r e s id u e f ra c ti o n time (hour) figure 5: residue mass fraction of pcff samples prepared at various time duration. pcff 6 pcff 7 pcff 8 pcff 9 pcff 10 pcff 11 pcff 12 pcff 13 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 r es id ue fr ac tio n sample residue fraction figure 6: residue fractions for different samples. erman senoz et al. (2010) [8], prepared pcff in two step pyrolysis similar to that described earlier. all the samples were heated to 215 0 c at a rate of 3 0 c/min for 15 hours. the samples were further heated immediately to various isothermal temperatures of 350 0 c, 400 0 c, 420 0 c, 450 0 c, 500 0 c at a rate of 3 0 c/min for 0.5, 1, 1.5 or 2 hours. the residue fractions of various samples are shown in figure 7. the cooled fibres, were washed with toluene and water to clean the materials from depositions. use of keratin present in chicken feather as a hydrogen storage material: a review 152 figure 7: residue mass fractions of pcff samples prepared at (a) 400 0 c, (b) 420 0 c and (c) 450 0 c versus the pyrolysistime at the 2nd step. figure 8: hydrogen uptake isotherms at -196 0 c of activated carbons obtained from rachis chicken feathers (a) cfac-450 (b) cfac-350 (c) cfac-250. 3. hydrogen uptake liliana giraldo et al. (2013)[9] subjected the samples (treated at 250 o c, 350 o c and 450 o c) at a constant temperature of -196 o c for pressures varying from 20-80 bar and its hydrogen uptake was measured and plotted as shown in figure 8. it is understood from the observation that the samples treated at a lower temperature of250 0 c and 350 o c showed less hydrogen adsorption capacities which was due to the result of less porosity and surface area. the sample that was treated at 450 o c showed highest hydrogen uptake with a maximum uptake of 3.5 wt% at 80 bar. there was an increase in the micropore volume (vμp(n2) cm 3 /g) with increase in pressure. the sample prepared at 450 o c showed highest micropore volume. erman senoz et al. (2009) [20], performed nitrogen adsorption, bet analysis and t-plot method on the samples and concluded that the samples that were heated up to 400 o c and 450 o c (pcff-6, 7, 8 and 10) in second pyrolysis step showed higher surface areas and degree of microporosity. specific surface area (sbet) obtained by bet method [23] in the relative pressure range of 0.01–0.05 and micropore volume (vmic) calculated by t-plot are tabulated in table 3: variation of specific surface area, micropore volume and adsorption capacity for different samples. sample pcff sbet (m 2 /g) vmic(cm 3 /g) adsorption capacity residue fraction 6 436 ± 4 0.178 best 0.176 ± 0.015 7 460 ± 2 0.196 best 0.101 ± 0.020 8 419 ± 6 0.176 best 0.063 ± 0.010 9 376 ± 0 0.133 best 0.209 ± 0.007 10 189 ± 6 0.072 medium 0.212 ± 0.018 11 114 ± 0 0.041 medium 12 14 ± 0 0.002 low 0.004 ± 0.001 13 < 1 <0.001 low 0.617 ± 0.022 akhil et al. (2020): international journal of engineering materials and manufacture, 5(4), 148-155 153 erman senoz et al. (2010) [8], performed nitrogen adsorption, bet analysis and t-plot method on the samples. it is found that, after the second step of pyrolysis the complex nature of the protein resulted in numerous degradations and rearrangement reactions at high temperatures. this is due to the side chain of various amino acids such as cysteine (thiol), serine (hydroxyl), glutamic acid (carboxyl), proline (nonpolar hydrocarbon), arginine (amine), etc. this meant that the evolution of the structure of these fibres during pyrolysis have high sensitivity to the reaction conditions. there were two divisions of pyrolysis reactions within temperature range 400-450 0 c which are microporeformation and micropore-destroying reaction. from the experimental data as shown in table 4, it is observed that the maximum specific surface area and microporosity occurs at 1 hour which are plotted in figure 9 and figure 10respectively. when the fibre was pyrolysed for a longer time (>1 hour) micropore-destroying reaction predominates decreasing the micropore volume. when hydrogen storage uptake is measured at room temperature and pressure 5.4 mpa it was evident that pyrolyzing for 1 hour leads to highest hydrogen storage uptake as shown in figure 11. table 4: variation of hydrogen storage uptake (22 o c and 5.4 mpa), specific surface area and micropore volume according to pyrolysis temperature and time. temperature of pyrolysis 0 c pyrolysis time h specific surface area m 2 /g micropore volume cm 3 /g hydrogen storage uptake at room temperature wt% 400 0.5 <10 0.002 0.04 400 1 414 0.178 0.35 400 1.5 226 0.092 0.18 400 2 51 0.020 0.22 420 0.5 221 0.082 0.14 420 1 315 0.120 0.25 420 1.5 163 0.077 0.19 420 2 237 0.092 0.24 450 0.5 336 0.136 0.26 450 1 430 0.173 0.37 450 1.5 29 0.009 0.15 450 2 89 0.032 0.20 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 0 100 200 300 400 500 s p e ci fic s u rf a ce a re a ( m 2 /g ) time (h) a b c figure 9: plot of specific surface area against time for the samples prepared at (a) 400 o c, (b) 420 o c and (c) 450 o c at the second step. use of keratin present in chicken feather as a hydrogen storage material: a review 154 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 m ic ro po re v ol um e (c m 3 /g ) time (h) a b c figure 10: plot of micropore volume against time for the samples prepared at (a) 400 o c, (b) 420 o c and (c) 450 o c at the second step. 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 h yd ro ge n st or ag e up ta ke (w t% ) time (h) a b c figure 11: plot of hydrogen storage uptake at room temperature (22 o c) and pressure 5.4 mpa against time for the samples prepared at (a) 400 o c, (b) 420 o c and (c) 450 o c at the second step. 4. conclusions 1. when the chicken feathers were treated less than an hour, the pyrolysed substance showed lesser micropore volume that led to the decrease in hydrogen uptake. 2. research studies and experiments have shown highest hydrogen uptake for one hour of treatment in the temperature range 400-450 o c. 3. hydrogen storage increases with increase in microporosity. references 1. http:// www.environmentalleader.com category/conventional-energy/ 2. http://www.climate.nasa.gov/vital-signs/carbon-dioxide/ 3. https://www.nasa.gov/feature/goddard/2016/climate-trends-continue-to-break-records/ 4. das s, sikdar s (2016). a review on the non-conventional energy sources in indian perspective ijert 5. dutta s (2016). a review on production, storage of hydrogen and its utilization as an energy resource. journal of industrial and engineering chemistry, 20(4).1148-56. 6. larminie j, dicks a, mcdonald ms (2003). fuel cell systems explained. chichester, uk: j. wiley. 7. zhou l (2005) progress and problems in hydrogen storage methods. renewable and sustainable energy reviews, 9(4):395-408. akhil et al. (2020): international journal of engineering materials and manufacture, 5(4), 148-155 155 8. senoz e, wool rp (2011). hydrogen storage on pyrolyzed chicken feather fibers. international journal of hydrogen energy, 36(12), 7122-7. 9. giraldo l, moreno-piraján jc (2013). exploring the use of rachis of chicken feathers for hydrogen storage. journal of analytical and applied pyrolysis, 104, 243-8. 10. kovács, balázs bálint. zoltán bagi. andrás tóth .gábor rákhely. katalin perei. kornél l (2005).utilization of keratin-containing biowaste to produce biohydrogen. applied microbiology biotechnology, 69,404–410. 11. barone, j.r. and schmidt (2005), w.f. polyethylene reinforced with keratin fibers obtained from chicken feathers. composites science and technology, 65(2), 173-181. 12. jones ln, riven de, tucker dj. handbook of fiber chemistry.marcel dekker, inc., new york, 1998. 13. belarmino, d.d., ladchumananandasivam, r., belarmino, l.d., andrade, s.m.b., galvão, a.o. and ribeiro, l.m. (2012). study of thermal stability of keratin fibre (kf) of chicken feathers for obtaining of carbon – carbonised feathers (cf).holos, 12, 30-40. 14. campbellm.k.bioquímica, 3th edition, artes medicassul-sul/biomed, 2006. 15. martínez-hernández al, velasco-santos c. keratin fibers from chicken feathers: structure and advances in polymer composites. keratin: structure, properties and applications: 1, 49-211. 16. meyers ma, chen py, lin ay, seki y (2012). biological materials: structure and mechanical properties. progress in materials science. 53(1), 1-206. 17. tanger p, field jl, jahn ce, defoort mw, leach je. biomass for thermochemical conversion: targets and challenges (2013). frontiers in plant science, 4,218. 18. sandru o. carbonized chicken feathers better than carbon nanotubes at storing hydrogen, the green optimistic 2009. http://www.greenoptimistic.com/2009/06/25/carbonized-chicken-feathers-hydrogen-storage/ 19. richard p. wool, erman şenöz hydrogen storage on carbonised chicken feather fibres.13th annual green chemistry & engineering conference. university delwar 2009. 20. senoz e, wool rp (. 2010). microporous carbon–nitrogen fibers from keratin fibers by pyrolysis. journal of applied polymer science, 118 (3), 1752-65. 21. https://us.vwr.com/store/product/4787011/barnstead-thermolyne-ashing-furnaces-type-6000-and-type-30400thermo-scientific 22. gao l, hu h, sui x, chen c, chen q. (2014) one for two: conversion of waste chicken feathers to carbon microspheres and (nh4) hco3. environmental science & technology. 12; 48(11), 6500-7. 23. brunauer, s., emmett, p.h. and teller, e (1938).adsorption of gases in multimolecular layers. journal of the american chemical society, 60(2), 309-319. international journal of engineering materials and manufacture (2018) 3(2) 78-86 https://doi.org/10.26776/ijemm.03.02.2018.02 n. a. j. hosni1 m. a. lajis2 , and m. r. idris3 1, 2sustainable manufacturing and recycling technology, advanced manufacturing and materials centre university tun hussein onn malaysia, 86400 parit raja, batu pahat, johor darul takzim, malaysia 3department of electrical engineering, politeknik sultan mizan zainal abidin jalan paka, 23000 kuala dungun, terengganu, malaysia 1e-mail: ainjhsweety568@gmail.com, 2e-mail: amri@uthm.edu.my, 3e-mail: ridzuan@psmza.edu.my reference:hosni, lajis and idris (2018). modelling and optimization of chromium powder mixed edm parameter effect over the surface characteristics by response surface methodology approach. international journal of engineering materials and manufacture, 3(2), 78-86. modelling and optimization of chromium powder mixed edm parameter effect over the surface characteristics by response surface methodology approach nor ain binti jamil hosni, mohd amri bin lajis and muhammad ridzuan bin idris received: 18 april 2018 accepted: 18 may 2018 published: 30 june 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract in this paper, an optimization of chromium powder mixed parameters effect, i.e. discharge current, pulse on time and cr powder concentration of aisi d2 steels in powder mixed edm (pmedm) has been made. rsm has been employed to plan and analyzed the experiment. central composite design (ccd) was chosen as the rsm design that is useful for investigating the quadratic effects. the version 8.0 of the design expert software was used to develop the experimental plan for rsm. a mathematical model in the form of the multiple regression equation for second order response surface with the best fittings was developed. the results identify that discharge current and pulse on time the most important parameters effect to minimize recast layer. with the topmost desirability solution, the suggested optimum parameter of discharge current is 20.12 a, pulse-on time 50.14 µs and 3.96 g/l powder concentration to minimize recast layer. keywords: pmedm, process optimization, response surface methodology, recast layer 1 introduction following the innovation of assembling industry today, machining process is confronting challenges from the promoting request that expected to utilize advanced materials, for example, composite, super alloys, and hardened steels that so difficult to machine. the rapid machine that can create worthy surface uprightness and exactness of cut with less instrument wear are the criteria to use in the propel innovation, i.e. aviation, car and medicinal material. since it is difficult to utilize conventional machining of the hard material, non-conventional machining, edm is one of the perfect skills in managing these materials, which incorporates hardened steel. there are two of the most basic constraints in edm are: the disintegration of the device cathode and poor workpiece surface quality, because of recementing of a portion of the dissolved however not shot out material back on the workpiece. the re-hardened material is alluded to as the recast layer, or white layer. the surfaces of materials machined by edm are essentially modified from the mass workpiece. because of fast re-harden, a very adjusted microstructure is created, which is regularly containing malleable remaining anxieties. sullying of the workpiece with carbon from the dielectric, and from instrument terminal material is likewise known to happen, bringing about an eccentric concoction creation in the machined surface. the morphology of the recast layer is ordinarily poor; showing high surface unpleasantness and containing pores and splits. these morphological highlights commonplace of edm'd surfaces constrain the weakness execution of the part because of stress focus impacts. surface splitting is especially impeding to exhaustion conduct, since the break start phase of disappointment has just happened. unpleasantness, porosity and surface breaking additionally confine erosion conduct of the machined part. to re-establish the machined surface properties and evacuate the surface recognizes, the procedure of fine powder blended into the dielectric liquid of edm, called the powder mixed edm (pmedm), is in this manner proposed [1, 2]. lajis, hosni and idris (2018): international journal of engineering materials and manufacture, 3(2), 78-86 79 pmedm is an incredible inventive technique which is utilized to machine the material with high mrr and surface complete and furthermore adjusts the surface properties of workpiece as per the request of properties. from the work revealed above, it is presumed that a less number of the work is done till these days on surface integrity. tan and yeo (2013) [3] considers the surface uprightness for nano powder-blended dielectric in micro-scale edm and demonstrates that the nearness of powder particles causes a simultaneous bigger plasma direct extension and decrease in division of warmth transition to the workpiece. in this work, recast layers delivered utilizing different powder concentrations. pecas et al. (2008) [4] exhibited an examination work that expects to think about the improvement in the polishing performance of conventional edm when used with a powdermixed into dielectric. the examination was completed by varying the silicon powder concentrations and flushing flow rate over a set of different processing areas and the impacts in the final surface were assessed. the outcomes demonstrate the positive impact of the silicon powder in the reduction of crater dimensions, white-layer thickness and surface roughness. wu et al. (2005) [5] investigated the improvement of surface finish on skd61 steel using edm with three different dielectrics pure kerosene; aluminum powder added kerosene and kerosene with aluminum powder and surfactant added dielectric. it was concluded that insulation is lowered and the gap distance between electrodes is increased with al powder added dielectric and the surfactant added in dielectric. the thin optimized recast layer can be accomplished when the dielectric is mixed with both aluminum powder and surfactant due to well dispersed aluminum powder and uniform distribution of discharge energy during the edm process. this paper expects to recognize the elements which impact the recast layer. this will permit the surface properties of edm'd materials to be all the more unequivocally controlled and more unsurprising. furthermore, these connections will be evaluated utilizing numerical demonstrating. 2 methodlogy figure 1 demonstrated representation of pmedm. the experiments were performed on a sinking edm machine (sodick edm aq55l) equipped with a self-made cycling system for powder mix analysis (figure 2). chromium powder (45-55 µm) was added to the kerosene. the filtered dielectric could be utilized recurrently through cycling system. overview research procedures shown in figure 3. the chemical compositions of aisi d2 hardened steel illustrated in table 1. table 2 shows all the parameters can affect machine characteristics. there are three machining parameters, namely discharge current, pulse-on, and powder concentration need to be determined in a pmedm operation. figure 1: schematic diagram pmedm modelling and optimization of chromium powder mixed edm parameter effect over the surface characteristics by rsm approach 80 figure 2: chromium powder was suspended in the dielectric fluid figure 3: overview research procedures table 1: chemical composition of aisi d2 element c cr si mn mo p< s< v< content (%) 1.40-1.60 11.00-13.00 0.40 0.60 0.80-1.20 0.030 0.030 0.20-0.50 lajis, hosni and idris (2018): international journal of engineering materials and manufacture, 3(2), 78-86 81 table 2: pmedm machining parameter. working parameters description workpiece aisi d2 electrode cuw (ø 10mm) dielectric kerosene and cr powder cr powder size 45-55µm concentration, c 0, 2, 4g/l polarity, p reverse polarity peak current, ip 20, 30, 40a pulse-on, pon 50, 75, 100µs duty cycle 80% voltage 120v depth of cut 3mm flushing rate 3.5lmm3/hour figure 4: basic optimization scheme of response surface methodology 3 response surface methodology response surface methodology (rsm) utilizing a sequence of designing experiments was employed to obtain optimal responses. rsm is a method of optimization using statistical and mathematic techniques useful for developing, improving and optimization process [6]. rsm also quantifies relationships among one or more measured responses and the vital input factors [7] and used to find optimal operating conditions within a system. a linear regression model is used to decide whether a movement of the centre point or a reduction of the search space should be performed next. figure 4 below shows a basic optimization scheme. 3.1 machining setup and experimental design abovementioned, there are three chromium (cr) powder mixed parameters effect i.e. discharge current, pulse on time and cr powder concentration were chosen as variables to study the process performance in terms of recast layer. pmedm parameters and their levels as shown in table 3. the pmedm process was investigated using ccd which is a typical rsm design [8]. a total of 20 experiments were performed in this study, which ran at the predetermined settings and according to the aforementioned procedure. factorial design used in this study is full factorial design with the six star point in the face of the cube portion of the design, 6 central points, and all combinations of the factors at the two levels. the star points links to an α =1 and this sort of design is normally termed face-centered ccd. the ‘design experts 8.0’ software was utilized for graphical analysis and regression of the obtained data. the optimal amounts of the chosen variables were acquired through solving regression equation and evaluating the response surface contour plots. a response surface contour plot stipulates an effective way of envisaging the interaction of parameter. modelling and optimization of chromium powder mixed edm parameter effect over the surface characteristics by rsm approach 82 table 3: pmedm parameters effect and levels for ccd parameters factor symbol unit level -1 0 +1 discharge current, ip a a 20 30 40 pulse on time, ton b µs 50 75 100 powder concentration, cp c g/l 0 2 4 table 4: design layout and experimental response for the pmedm exp.no block process parameters response discharge current, ip, a pulse on time, ton, b powder concentration, cp, c recast layer, rl (µm) 1 block 1 20.00 50.00 0.00 21.13 2 block 1 40.00 50.00 0.00 26.25 3 block 1 20.00 100.00 0.00 26.12 4 block 1 40.00 100.00 0.00 33.02 5 block 1 20.00 50.00 4.00 19.82 6 block 1 40.00 50.00 4.00 26.83 7 block 1 20.00 100.00 4.00 25.25 8 block 1 40.00 100.00 4.00 32.27 9 block 1 20.00 75.00 2.00 23.17 10 block 1 40.00 75.00 2.00 28.65 11 block 1 30.00 50.00 2.00 20.08 12 block 1 30.00 100.00 2.00 26.58 13 block 1 30.00 75.00 0.00 28.39 14 block 1 30.00 75.00 4.00 27.36 15 block 1 30.00 75.00 2.00 25.99 16 block 1 30.00 75.00 2.00 27.29 17 block 1 30.00 75.00 2.00 28.59 18 block 1 30.00 75.00 2.00 24.69 19 block 1 30.00 75.00 2.00 23.39 20 block 1 30.00 75.00 2.00 25.99 4 results and discussions the layout of the design and results of the experiment for the pmedm performance characteristics were tabulated in table 4. for the data analysis, it is necessary to test the goodness of fit of the model. the model accuracy checking included test for significance on model coefficients, test of lack of fits, and tests of significance of regression model. therefore, analysis of variance (anova) is done towards response surface quadratic model for recast layer. the estimations of “prob. > f” in table 5 for model is fewer than 0.05 which designates the significance of the model and it is desirable as it specifies that the terms in the model have a substantial influence on the response. in the same manner, the main effect of discharge current (a), pulse on time (b), the second-order effect of pulse on time (b2) and the second-order effect of powder concentration (c2) are significant model terms. other model terms can be said to be insignificant. these inconsequential model terms (not including those required to help hierarchy) can be evacuated and may bring about an enhanced model. the lack-of-fit can likewise be said to be irrelevant. this is attractive as we need a model that fits. by choosing the retrogressive end methodology to naturally lessen the terms that are not huge, the subsequent anova table for the diminished quadratic model for surface unpleasantness is appeared in table 6. results from table 6 demonstrate that the model is as yet critical. notwithstanding, the primary impact of discharge current (a), pulse on time (b), the second-order effect of pulse on time (b2) and the second-order effect of powder concentration (c2) are the significant model terms. the main effect of powder concentration (c) was added to support hierarchy. the main effect of discharge current (a) and pulse on time (b) are the most substantial factor related with recast layer. lajis, hosni and idris (2018): international journal of engineering materials and manufacture, 3(2), 78-86 83 table 5: anova for recast layer (before eliminating) source sum of squares degrees of freedom mean square f-value prob>f model 207.96 9 23.11 12.35 0.0003 significant a 99.41 1 99.41 53.13 <0.0001 b 84.86 1 84.86 45.35 <0.0001 c 1.14 1 1.14 0.61 0.4527 ab 0.40 1 0.40 0.21 0.6535 ac 0.51 1 0.51 0.27 0.6147 bc 0.099 1 0.0996 0.053 0.8227 a2 0.35 1 0.35 0.19 0.6745 b2 13.59 1 13.59 7.26 0.0225 c2 14.82 1 14.82 7.92 0.0183 residual 18.71 10 1.82 lack of fit 1.81 5 1.87 0.11 0.9858 not significant pure error 16.90 5 0.36 cor. total 226.67 19 3.38 standard deviation = 1.37 r2 = 0.9175 mean = 26.04 r2 adjusted = 0.8919 coefficient of variation = 5.25 predicted r2 = 0.5759 predicted residual error of sum squares (press) = 39.64 adequate precision = 15.172 table 6: anova for recast layer (after elimination) source sum of squares degrees of freedom mean square f-value prob>f model 206.61 5 41.32 28.83 <0.0001 significant a 99.41 1 99.41 69.37 <0.0001 b 84.86 1 84.86 59.21 <0.0001 c 1.14 1 1.14 0.80 0.3870 b2 13.97 1 13.97 9.75 0.0075 c2 19.30 1 19.30 13.46 0.0025 residual 20.06 14 1.43 lack of fit 3.16 9 0.35 0.10 0.9979 not significant pure error 16.90 5 3.38 cor. total 226.67 19 3.38 standard deviation = 1.20 r2 = 0.9115 mean = 26.04 r2 adjusted = 0.8799 coefficient of variation = 4.60 predicted r2 = 0.8681 predicted residual error of sum squares (press) = 29.89 adequate precision = 19.533 modelling and optimization of chromium powder mixed edm parameter effect over the surface characteristics by rsm approach 84 this is normal since it is notable that discharge current gives a critical effect on recast layer and lower discharge current can deliver the more slender recast (white) layer. furthermore, the outcomes demonstrate that the pulse on time likewise is the one of the huge elements that can influence the recast layer. fundamentally recast layer is framed when the current from the edm procedure dissolves the material and the liquid material not flushed away by the dielectric. the period that release vitality liquefy and vaporized workpiece relies upon pulse on setting. the outcome demonstrates that expanding the pulse on will build the recast layer. this is most likely because of long pulse on causes the plasma channel to grow and this development causes less vitality thickness on the workpiece, which is lacking to liquefy and vaporize the workpiece material, which eventually brings about a thick white layer [9]. the lack-of-fit is still allegedly be inconsequential. the r2 value is exalted , close to 1, which is coveted . the forecasted r2 is in rational agreement with the adjusted r2. the adjusted r2 value is particularly beneficial in comparing models with varied number of terms. however, this comparison is done in the background while model reduction is progressing. sufficient accuracy assesses predicted values range at the design points to the average prediction error. ratios that are more than 4 signifies the sufficient discrimination of the model. particularly, this study resulted in the value well above 4. after excluding the insignificant terms, the ultimate response equation for mrr is given as follows: recast layer = 25.86+3.15*a+2.91*b-0.34*c-2.09*b2+2.46*c2 (in coded terms) (1) recast layer =-8.35+0.32ip+0.62ton, -2.63cp-3.343e-003ton2+0.614cp 2 (in actual factors) (2) the 3d surface graphs for recast layer at different interaction process parameters are presented in figure 5 and figure 6. both have curvilinear profile in accordance to the quadratic model fitted. it is clear from figure 5 that at powder concentration of 2 g/l, the best recast layer is obtainable when the discharge current 20 a and pulse on time 50 µs. this is consistent with the fact that the discharge current and pulse on time term are significant. also at lower discharge current and pulse on time, better surface roughness is obtainable. it is also obviously from figure 5 that the recast layer increasing with ascending discharge current and pulse on time. figure 5: three dimensional surface graph for recast layer between discharge current and pulse on time 5 optimization of desirability the greatest and utmost efficient parameters will be revealed in the optimization. the elucidation implied for aptness is indicated in table 7. the topmost desirability solution number 1 ought to be selected as the desirability (99%) is extremely near to 100%. optimization graph and contour plot for solution desirability is shown in figure 7 and figure 8, respectively. table 7: solution for desirability solution number discharge current, ip, a pulse on time, ton, b powder concentration, cp, c recast layer desirability 1 20.12 50.14 3.96 19.8126 1.000 selected lajis, hosni and idris (2018): international journal of engineering materials and manufacture, 3(2), 78-86 85 figure 6: three dimensional surface graph for recast layer between discharge current and powder concentration figure 7: three dimensional surface graph for solution desirability modelling and optimization of chromium powder mixed edm parameter effect over the surface characteristics by rsm approach 86 figure 8: contours for solution desirability function 6 conclusions the outcomes of an experimental reconnaissance on the influence of discharge current, powder concentration and pulse on time on the recast layer while machining aisi d2 hardened steel within pmedm was presented in this study. it was found that the discharge current and pulse on time are the most significant factor influencing the response variables studied through anova tests. the reduced quadratic models obtained through rsm were relatively precise and usable in prediction concerning the constrains of the investigated factors. acknowledgement the authors would like to show their utmost gratitude towards the ministry of higher education (mohe), malaysia, for subsidizing this research project via the exploratory research grant schemes (ergs-vote numbers 0886). additional supports in terms of facilities were also provided by universiti tun hussein onn malaysia (uthm). references 1. hosni, n.a.j. and m.a. lajis, the influence of span-20 surfactant and micro-/nano-chromium (cr) powder mixed electrical discharge machining (pmedm) on the surface characteristics of aisi d2 hardened steel. iop conference series: materials science and engineering, 2018. 342(1): p. 012095. 2. lajis, m. and n. hosni, the influences of various mixed dielectric fluids on the performance electrical discharge machining of aisi d2 hardened steel. materialwissenschaft und werkstofftechnik, 2018. 49(4): p. 413-419. 3. tan, p. and s. yeo, simulation of surface integrity for nanopowder-mixed dielectric in micro electrical discharge machining. metallurgical and materials transactions b, 2013. 44(3): p. 711-721. 4. peças, p. and e. henriques, effect of the powder concentration and dielectric flow in the surface morphology in electrical discharge machining with powder-mixed dielectric (pmd-edm). the international journal of advanced manufacturing technology, 2008. 37(11-12): 1120-1132. 5. wu, k.l., et al., improvement of surface finish on skd steel using electro-discharge machining with aluminum and surfactant added dielectric. international journal of machine tools and manufacture, 2005. 45(10): p. 11951201. 6. montgomery, d.c., design and analysis of experiments. 2008: john wiley & sons. 7. myers, r.h., d.c. montgomery, and c.m. anderson-cook, response surface methodology: process and product optimization using designed experiments. 2016: john wiley & sons. 8. jeff, c., w. hamada, and c. michael, experiments: planning, analysis, and parameter design optimization. 2000, wiley, john & sons. 9. syed, k.h. and k. palaniyandi, performance of electrical discharge machining using aluminium powder suspended distilled water. turkish journal of engineering & environmental sciences, 2012. 36(3): 195-207. international journal of engineering materials and manufacture (2018) 3(2) 105-112 https://doi.org/10.26776/ijemm.03.02.2018.05 s. m. s. abd rashid, h. anuar , s. n. e’zzati, and f.b. yose department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia 1 e-mail: sitimunirahsalimah@gmail.com, 2 e-mail: hazleen@iium.edu.my 3 e-mail: snezzatiapandi@gmail.com, 4 e-mail: yose@iium.edu.my reference: abd rashid, s. m. s., anuar, h., e’zzati, s. n., and yose, f. b. (2018). effect of uv radiation on degradation of durian skin fibre composites. international journal of engineering materials and manufacture, 3(2), 105-112. effect of uv radiation on degradation of durian skin fibre composite siti munirah salimah abd rashid, hazleen anuar, siti nur e’zzati mohd apandi and yose fachmi buys received: 30 april 2018 accepted: 22 may 2018 published: 30 june 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract durian skin fibre (dsf) reinforced high-density polyethylene (hdpe) composite was fabricated by melt-blending and then compression moulded. as dsf is polar and hydrophilic in nature, while hdpe is non-polar and hydrophobic, thus the adhesion between them is low. therefore, maleic anhydride-grafted-polyethylene (mape) was added to enhance the interaction of hdpe and dsf. this paper highlight the effect of mape on hdpe/dsf composite. dsf content from 10, 20, 30 and 40 wt% were immersed in water for 70 days. water absorption was increased with dsf loadings. however, the increasing of water absorption was low as mape was added. furthermore, tensile properties of hdpe/dsf composite was degraded after 500, 1000 and 2000 h of uv radiation exposure. morphological observation under sem showed that the fibre and matrix became less interacted after exposed to uv radiation. voids and gaps between hdpe and dsf in the presence of mape were reduced as revealed under sem micrographs. the colour index of the hdpe/dsf composite was increased and became whiter with uv radiation exposure but the presence of mape reduced the colour changed. this showed that mape significantly improved the properties of hdpe/dsf composite. keywords: durian skin fibre, high-density polyethylene, coupling agent, water absorption, uv radiation 1 introduction in recent years, the use of natural fibre as reinforcement for plastics, replacing glass fibre and other synthetic material has increased rapidly. this is due to the low cost, good specific properties, low density, renewability, environmental friendliness and reduced energy consumption. one of the example of natural fibre is durian skin fibre (dsf) that extracted from durian or durio zibethinus. durian is popular in southeast asia like thailand, malaysia, indonesia and philippines. the statistical data from malaysia ministry of agricultural and agro-based industry reported that malaysia produced 320,164 metric ton (mt) of durian fruit in 2013. this production was roughly 20,000 mt greater compared to 2012 [1]. as the production of durian increased, the agricultural waste of durian also increased and may lead to the environmental problems if this waste is not dispose efficiently. to reduce this problem, these agricultural waste can be recycled and reused to produce new product. durian skin fibre consist of 47.2% cellulose, 9.63% hemicellulose, lignin and ash with 9.89% and 4.20% respectively [2,3]. basically, cellulose has lower water absorption resistance because of the hygroscopic characteristic. durian contains only 50-65% of flesh while the rest is considered as waste which include skin and seed which is 45-55% [1]. composite based on thermoplastic reinforced with natural fibre was increased over the last decade. the improvement of using this composite is due to good performance of natural fibre, for instance low density, high stiffness, low cost, renewability, environmental friendly and low energy consumption compared to features of inorganic reinforcement like glass, silica, clay and many more. material durability is a vital information to determine the effect of weathering in analysing the material life span for outdoor application. material with good mechanical properties is not necessarily can endure the degrading elements of weather. mechanical properties are reduced because of exposing to the ultraviolet (uv) radiation of sunlight, rain and humidity [4]. it is an important issue to understand the interfacial adhesion between polymer effect of uv radiation on degradation of durian skin fibre composite 106 matrix and fibre reinforcement in composite. this is to ensure the composite product can be used in a longer time. degradation of the interface of matrix and reinforcement resulting in decrease the performance of the composite for the stress transfer between these materials and reduce the mechanical properties [5]. this paper reported the effect of water absorption and uv exposure on mechanical and physical properties on hdpe/dsf composite. maleic anhydride grafted polyethylene (mape) was added as a coupling agent for hdpe and dsf. 2 methodology durian waste was obtained from the local market. firstly, the inner skin was removed and then washed thoroughly to remove any dirt and dusk. after that, the skin was dried in an oven for 24 h at 60 ̊c after chopping and grinding process. the skin was then crushed to get smaller size and was sieved with a 250 µm siever to get durian skin fibre as exhibited in figure 1. figure 1: preparation of durian skin fibre the blending of hdpe/dsf composites were processed using thermo haake 600p internal mixer at temperature of 135 ̊c and a rotational speed of 65 rpm for 8 min. the composition were varied from 10 wt%, 20 wt%, 30 wt% and 40 wt% of dsf with the presence of 3 wt% of mape. the other compositions are 10 wt%, 20 wt%, 30 wt% and 40 wt% dsf with hdpe without mape and 100 wt% hdpe as well as shown in table 1. upon completion of the mixing process, the composites blend were shaped in the mould by using a hot press machine with a 135 ̊c for 8 min in each bottom and upside. the hdpe/dsf composite samples were placed in q-sun xenon 1 (utm skudai, johor) test chamber for uv exposure. the irradiation of uv was set to 1.10 w/m² and the black panel temperature was 65 ̊c. the samples were left in uv chamber for 500, 1000 and 2000 h. all samples were then tested for tensile test, fourier transform infrared (ftir) spectroscopy and characterized for its morphology by scanning electron microscope (sem). lastly, the samples were also analysed for its colour to investigate the effect of degradation after exposed to uv radiation. table 1: composition of the composite blend sample hdpe (%) dsf (%) mape (%) 1 100 2 90 10 3 80 20 4 70 30 5 60 40 6 87 10 3 7 77 20 3 8 67 30 3 9 57 40 3 3 characterization of the composite water absorption analysis was carried out to determine the amount of water absorbed into the sample. the weight of the composite was measured for every 24 h for the first two weeks and continued once a week until the increasing of weight is constant. before weighing, the sample was wiped with a tissue paper to ensure it is dry. the percentage of water absorption (wa) is determined by following eqn. 1. wa (%) = [(𝑊1 − 𝑊0) 𝑊0]⁄ 𝑥 100 (1) rashid et al., (2018): international journal of engineering materials and manufacture, 3(2), 105-112 107 where 𝑊1 is the mass of the samples after immersion and 𝑊0 is the mass of the samples before immersion tensile test was performed based on astm d638 using universal machine (autograph ags-x) with strain rate of 5 mm/min and load of 5 kn. scanning electron microscope (sem) (jeol, jsm-5600) was used to observe the fracture surface of the composite samples before and after the uv exposure with magnification of 500x. before morphology was observed, the samples were cut into small pieces and coated with thin layer of gold to avoid electrostatic charging during evaluation. ftir was conducted to obtain the information of the existence of the functional groups at the surface of the samples. ftir spectra were analysed with an ir spectrometer within wave number range between 4000 cm -1 and 600 cm -1 using perkin elmer, model spectrum one. the optical properties was measured by uv-visible spectrometer with the cielab colour system. in this colour system, l indicates lightness, a and b are the chromaticity coordinates where a is the red/green coordinate and b is the yellow/blue coordinate. deltas for l (∆l), a (∆a) and b (∆b) representing the differences between initial values (before weathering) and final values (after weathering) of l, a and b, respectively. an increasing of l value indicates the sample is lightening. for example, positive ∆l for lightening and negative ∆l for darkening. positive ∆a mean it switch toward red while negative ∆a mean it switch toward green. positive ∆b signifies a shift toward yellow and negative ∆b signifies a shift toward blue. the total colour difference (∆e) is always positive and determined by using eqn. 2. ∆𝐸 = (∆𝐿2 + ∆𝑎2 + ∆𝑏2)1/2 (2) 3 results and discussion 3.1 water absorption test figure 2 showed the percentage of water absorption of hdpe/dsf composites with and without mape. water absorption of the composite samples were higher as the composition of dsf was increased. the water absorption of 40 wt% dsf was increased rapidly in the first ten days and continue until they reached the maximum and constant water uptake. the weight of the composite samples remain constant at certain time. at this point, it is called saturation point and the duration of this point is different for all compositions. composition with 40 wt% of dsf without mape had the highest water uptake due to the hydrophilic nature of natural fibre and poor interfacial interaction between hdpe and dsf. dsf is a natural fibre and it is hydrophilic thus easy to absorb the moisture. the composition with 10 wt% of dsf with mape had better interaction between dsf and hdpe. the percentage of water absorbed was depend on the content of natural fibre in which 10 wt% was the lowest, then 20 wt% followed by 30 wt% and 40 wt%, respectively. this means that with increasing of dsf content, the cellulose content and the number of hydroxyl (oh) group in the composites also increased. this will result in increasing the water uptake as free ohgroups come in contact with water and form hydrogen bonding. the composite with lower cellulose content reach the equilibrium moisture content more quickly [6,7]. however, adding mape into hdpe/dsf composite reduced the water absorption in the composite as shown in figure 2. each composition of dsf with mape absorbed lower moisture compared to without mape. mape acted as a coupling agent and thus blocked the permeation of water into the durian skin fibre. water absorption of 10 wt% dsf with mape at 70 days was 2.3% higher compared to 10 wt% dsf without mape. this indicated that mape helped in improving the interfacial adhesion between dsf and hdpe by reducing the gaps as observed under sem micrograph in figure 4. for pure hdpe, it showed that the water absorption was constant as it hydrophobic and absorbed no moisture. figure 2: percentage of water absorption of unreinforced hdpe, hdpe/dsf and hdpe/dsf/mape composite effect of uv radiation on degradation of durian skin fibre composite 108 3.2 tensile test figure 3 exhibited the tensile strength of unreinforced hdpe and hdpe/dsf composite with and without mape. hdpe/dsf composite with mape had higher tensile strength compared to without mape but lower than unreinforced hdpe. from figure 3, it was observed that the tensile strength was decreased as the exposure time to the uv was longer for all specimens. tensile strength of the unexposed specimens were highest for each sample followed by 500, 1000 and 2000 h, respectively. the tensile strength of 500 h exposure time for hdpe recorded 15.2 mpa which was 11.6% higher compared to 1000 h. tensile strength of hdpe/dsf dropped significantly at 38.9% after 1000 h of exposure. this was due to the broken polymer chains by uv radiation into smaller and micro-cracking occurred in polymer leading to the failure of specimens under lower loading with exposure time. similar observation was also reported by umar et al. (2012) on effect of accelerated weathering on tensile properties of kenaf reinforced high density polyethylene composites [4]. the tensile strength of dsf composite was higher in the presence of mape because the interaction between filler and matrix became stronger [8,9]. interfacial adhesion was degraded and pore size was increased as the specimens were exposed to uv radiation. the uv exposure encouraged the molecular chain scission and formation of carbonyl and hydroperoxides. the poor interfacial bonding between fibre and polymer resulted in lower tensile strength. however, the addition of mape enhanced the strength of composite by bridging the dsf and hdpe and made their interaction better. this is evident in figure 3 where the tensile strength of dsf composites with mape were higher compared to without mape. the existing of voids might also be a factor for the drop in tensile strength of hdpe/dsf composites. 3.3 sem micrograph sem micrographs of the fracture surface from the tensile test of hdpe/dsf and hdpe/dsf/mape composites of unexposed and exposed to uv radiation were shown in figure 4. in figure 4(a), the fibre seem to detach from hdpe matrix and the formation of voids were clearly seen. this was due to the poor interfacial adhesion between the fibre and matrix. these features showed that the tensile strength of hdpe/dsf composite was low in the absence of mape. the presence of voids or gaps led to more weakening point, thus it diminished the strength [10]. the efficiency of stress transfer from matrix to fibre was also reduced because of the incompatibility between hdpe and dsf. therefore, mape was used as a bridge between hdpe and dsf. the presence of mape enhanced the interfacial adhesion between matrix and fibre and hence improved the tensile strength of the composite. in addition, the voids between hdpe and dsf were decreased as shown in figure 4(b). as a result, the stress transfer between matrix and fibre could be effective. however, the surface characteristic of hdpe/dsf composites were changed significantly after exposure to uv radiation. the bonding between the matrix and fibre became poorer for both specimens with and without mape. from figure 4(c), it revealed the surface of fibre was unequally distributed in the matrix due to the presence of voids. these voids leading to brittle and low tensile strength. nevertheless, the crack formation in the hdpe matrix appeared to be less severe for the hdpe/dsf composite with mape compared to without mape. furthermore, the presence of more voids were shown in figure 4(c) as coupling agent was absent compared to figure 4(d). a good compatibility between the matrix and fibre improved the strength after hdpe/dsf composites were treated with mape. figure 3: effect of exposure time of tensile strength of unreinforced hdpe, hdpe/dsf and hdpe/dsf/mape composite rashid et al., (2018): international journal of engineering materials and manufacture, 3(2), 105-112 109 figure 4: sem micrographs for unexposed uv of hdpe/dsf composite (a) without mape, (b) with mape, and uv exposure (c) without mape, (d) with mape 3.4 fourier transform infrared analysis the infrared spectra for durian fibre was obtained by using an ftir spectrometer as shown in figure 5. from the figure 5(a), the peaks at 2915-2914 cm-1 and 2847 cm-1 represent the c-h stretching vibration while the peaks at 1472 cm-1 and 1462-1461 cm-1 demonstrate the c-h bending from the alkane group [13]. the oh peak was more likely to be broader in the presence of mape from 3500-3000 cm-1 showing that a reaction took place between the fibre’s hydroxyl group and polar group in mape because of esterification reaction supplied by the mape [14]. the peak between 1750-1650 cm-1 is related with the c=o group and owned by maleic anhydride in mape. mape produced esterification reactions and covalent bonding with the hydroxyl group in cellulose fibre in order to enhance the bonding between hdpe matrix and dsf [14]. the bands between 1461-730 cm-1 was disappeared after exposed to uv radiation. the peak at 802 cm-1 shown in figure 5(b) could be result from presence of lignin and was removed after exposed to uv. it was also noticed that the peak at 1262 cm-1 was missing as illustrated in figure 5(b). this is due to the hemicellulose that bind to each other was removed. the peaks detected at 1472-1464 cm-1 and 730-718 cm-1 associated with content of polyethylene crystalline (1472 and 730 cm-1) and amorphous content (1464-718 cm-1) [13,15]. 3.5 optical test the colour of composite specimens was changed as it underwent the photodegradation process. figure 6 revealed the lightness of specimens was increased after it exposed to uv radiation. this showed that the specimens became whiter as exposure times was longer from 500 to 2000 h. however, the l values for hdpe/dsf/mape composite was lower than hdpe/dsf composite. the lightening of composite was lower due to the presence of coupling agent. the addition of mape blocked the penetration of uv radiation and to mask the bleaching of hdpe/dsf [11]. the values of ∆e at different exposure times for hdpe/dsf with and without mape were revealed in table 2. the increased values proved the increased of lightness as specimens turned whiter after it exposed to uv radiation. the specimens with 500 h of exposure times showed the lowest colour shift followed by 1000 and 2000 h, respectively. the difference of ∆e was due to bleaching of the fibre component, degradation of polymer as it exposed to uv radiation and the darkening effect which could be linked to surface oxidation [12]. exposure to uv radiation, moisture and oxidation of polymer degraded the surface layer of composite and removed the colour of materials. therefore, the colour of composite was changed. (a) (b) (d) (c) effect of uv radiation on degradation of durian skin fibre composite 110 figure 5: ir spectra of hdpe/dsf composite and hdpe/dsf/mape composite (a) unexposed uv (b) exposed uv (a) (b) rashid et al., (2018): international journal of engineering materials and manufacture, 3(2), 105-112 111 figure 6: effect of exposure time on l of hdpe/dsf and hdpe/dsf/maoe table 2: ∆e at various exposure time exposure time (h) colour change (∆e) hdpe/dsf hdpe/dsf/mape 500 9.04 9.44 1000 14.82 13.46 2000 20.07 16.27 6 conclusions in this research, durian skin fibre (dsf) reinforced high density polyethylene (hdpe) with and without maleic anhydride-grafted-polyethylene (mape) as a coupling agent has been developed. the effects of mape on water absorption, tensile test, surface morphology and colour properties showed the followings: 1. the addition of mape reduced the water uptake. this suggests that coupling agent enhanced the interaction between natural fibre and polymer matrix as it decreased the water absorption when mape was added. 2. the performance of hdpe/dsf composite was degraded as the time exposure to uv radiation increased to 500, 1000 and 2000 h. however, incorporation of mape reduced the degradation of the hdpe/dsf composite. for example, after 2000 h of exposure, the tensile strength of hdpe/dsf without mape was 7.3 mpa and increased to 9.3 mpa when mape was added. 3. the surface morphology under sem observation revealed that deterioration of the surface layer on hdpe/dsf composite occurred after exposed to uv radiation. interfacial adhesion between hdpe and dsf for both unexposed and exposed uv radiation were poorer in the absence of mape. 4. the existence of mape reduced the colour change of hdpe/dsf composite. acknowledgement the authors wish to thank fundamental research grant scheme (frgs16-003-0502) and fundamental research grant scheme (frgs14-108-0349) awarded by the ministry of education malaysia for the financial support and international islamic university malaysia for the facilities and equipment in making these studies a success. effect of uv radiation on degradation of durian skin fibre composite 112 references 1. manshor, m. r., anuar, h., mohd nasir, n. a., ahmad fitrie, m. i., wan busu, w. n., el-shekeil, y. a., & wahit, m. u. (2014). mechanical, thermal and morphological properties of durian skin fibre reinforced pla biocomposites. materials and design, 59, 279-286. 2. charoenvai, s. (2014). a new material from recycled hdpe and durian peel fiber. the 5th tsme international conference on mechanical engineering. chiang mai: tsme-icome asean and beyond. 3. charoenvai, s. (2014). durian peels fiber and recycled hdpe composites obtained by extrusion. energy procedia, 56, 539-546. 4. umar, a., zainudin, e., & sapuan, s. (2012). effect of accelerated weathering on tensile properties of kenaf reinforced high-density polyethylene composites. mechanical engineering and sciences (jmes), 2, 198-205. 5. rashdi, a., sapuan, s., ahmad, m., & khalina, a. (2010). combined effects of water absorption due to water immersion, soil buried and natural weather on mechanical properties of kenaf fibre unsaturated polyester composites (kfupc). mechanical and materials engineering (ijmme), 5(1), 11-17. 6. abd aziz, n. z., mohamed, r., & fahimi, m. (2015). effects of kenaf and rice husk on water absorption and flexural properties of kenaf /caco3/hdpe and rice husk/caco3/hdpe hybrid composites. international journal of environment, chemical, ecological, geological and geophysical engineering, 9(4), 349-353. 7. penjumras, p., abdul rahman, r., talib, r., & abdan, k. (2015). mechanical properties and water absorption behaviour of durian rind cellulose reinforced poly(lactic acid) biocomposites. advanced science engineering information technology, 5(5), 343-348. 8. makara, l., rashid, a., othman, n., tezuka, y., & chhorda, p. (2014). comparison of mechanical properties and curing characteristics of natural rubber composites with different coupling agent. advanced materials research, 858, 24-31. 9. huang r., xu x., lee s., zhang y., kim b.-j., & wu q. (2013). high density polyethylene composites reinforced with hybrid inorganic fillers: morphology, mechanical and thermal expansion performance. materials, 6, 41224138. 10. anuar, h., mohd nasir, n. a, & el-shekeil, y. (2015). effects of coupling agent on the properties of durian skin fibre filled polypropylene composite. chemical, molecular, nuclear, materials and metallurgical engineering, 9(12), 1300-1304. 11. stark, n., & matuana, l. (2003). ultraviolet weathering of photostabilized wood-flour-filled high-density polyethylene composites. applied polymer science, 90, 2609-2617. 12. bajwa, d., bajwa, s., & holt, g. (2015). impact of biofibers and coupling agents on the weathering characteristics of composites. polymer degradation and stability, 120, 212-219. 13. stark, n., & matuana, l. (2004). surface chemistry changes of weathered hdpe/wood-flour composites studied by xps and ftir spectroscopy. polymer degradation and stability, 86, 1-9. 14. zulkifli, n. i., samat, n., anuar, h., & zainuddin, n. (2015). mechanical properties and failure modes of recycled polypropylene/microcrystalline cellulose composites. materials and design, 69, 114-123. 15. stark, n., & matuana, l. (2004). surface chemistry and mechanical property changes of wood-flour/high-densitypolyethylene composites after accelerated weathering. applied polymer science, 94, 2263-2273. international journal of engineering materials and manufacture (2020) 5(2) 62-67 doi: https://doi.org/10.26776/ijemm.05.02.2020.05 s. islam kent institute australia pty. ltd. (kent) level 10, queen street melbourne, vic 3000, australia e-mail : saiful.islam@kent.edu.au reference: islam, s. (2020). enhanced information system security in internet banking and manufacturing. international journal of engineering materials and manufacture, 5(2), 62-67. enhanced information system security in internet banking and manufacturing saiful islam received: 03 june 2020 accepted: 22 june 2020 published: 30 june 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 abstract the internet has contributed significantly by changing the way of interaction among people and the execution of business today. by virtue of the internet, electronic commerce has been developed, enabling business to manage their customers and other organisations inside more effectively and outside their industries. the industry which is applying business transaction using this new communication pathway to reach its business clients is the banking sector. the electronic banking system identifies different emerging trends including providing service to meet customer's demand anytime and anywhere, importance of product time-to-market and increasingly complex back-office integration challenges. the challenges that internet banking is facing are providing information system security and protecting privacy of information. this paper will first discuss the current forms of security threats in the internet banking; secondly, it will investigate weaknesses in the current information security protocols of the internet banking. thirdly, it will propose an enhanced information system security for internet banking. keywords: information system, security risk, and internet banking. 1 introduction banking is one of the oldest businesses known to humankind. technology however have transformed and transitioned the traditional banking processes and strategies. banking institutions have heavily invested in information technology in addition to other well-known systems such as telephone and branch banking. according to rahi et al. (2018), banks have claimed information systems contributes to reduced operating costs and competitive advantage over rivals as some of the reasons for adopting information technology. internet banking is the latest information technology infrastructure and has brought a 360-degree change in the entire finance industry. the adoption of internet banking has helped banks to offer real time financial transactions and helps in attracting and retaining customers. this is because banking institutions are now able to offer services at the comfort of customers that who would otherwise be needed to be physically present for transactions. the impacts of internet banking have been of interest to both business financial researchers and banking management. ntseme, nametsagang, and chukwuere (2016) in a study of risks and benefits of online banking focused on the five advantageous factors of internet banking that is: accessibility, perceived security, self-efficacy, convenience, and usability. ling et al. (2016) identified speed, convenience, 24hours banking as benefits of online banking. even though banks in several countries have integrated security features, there is several internet security threats and vulnerabilities still continue to persist. as new threats continue to emerge, banks will need to adopt new measures to protect users. banks can do more by deploying information security policies that ensure safer internet banking experience. the purpose of this report is to evaluate the current forms of security threats in the internet banking, investigate weaknesses in the current information security protocols of the internet banking and propose an enhanced information system security for internet banking. 2 an overview of internet banking according to shaikh and karjaluoto (2018), internet banking is a connection of banking systems that enable customers to get access to their bank accounts and other important banking details through the use of a website and without the inconvenience of attending physically to the bank, sending faxes, letters, or telephone confirmations. internet banking has also been defined as a technological service which customers can request bank services such as opening of an account, funds transfer, balance inquiry, and online payments over the internet without leaving their homes or https://doi.org/10.26776/ijemm.05.02.2020.04 enhanced information system security in internet banking and manufacturing 63 organizations (sundaram et al. 2019). ramavhona and mokwena (2016) stated that the key feature of internet banking is that it provides a universal connection from any location globally and it is very accessible from any internet connected computer. the convenience of internet banking is making more and more banks are integrating internet into their services to develop and expand transactional relationships with their customers (ramavhona & mokwena, 2016). novokmet and tokić (2016) identified three functional levels of internet banking that are currently employed in the banking industry as show in figure 1. • informational roletypically, the bank uses a stand-alone server to send marketing information over the internet to consumers about their products and services. this is usually the basic role of internet banking • communicative levelthis role allows interaction between the consumer and the bank systems. the communication is often limited to loan applications, personal details updates (name and address updates) and electronic mail. • transactional levelthis functional level allows bank customers to directly execute financial transactions. usually, the most basic transactional system allow customer to only transfer funds between different accounts of bank. today, the advanced transactional internet systems allow online payments directly to third parties taking the forms of electronic bank check, electronic money transfer, and bill payments. kalra and narayan (2017) in a case study in india defined internet banking as a convenient form of banking where a bank account is usually maintained over the internet. the authors stated that the internet banking has a multidimensional advantage, which is both to the consumers and the banking institutions as shown in table 1. despite a lot of benefits of internet banking, there are some security threats exist in current internet banking system. tabiaa et al. (2017) found that internet banking combines a lot of risks. the authors classified the risks into two parts; that is general and operational risks. the general risks are associated with physical equipment such as computers and server tools. the operational risks mean inadequate processes, eternal attacks, and failure of people and system. the operational risks are important to this study as they are a security threat to the provision of internet banking services. figure 1: the three functional roles of internet banking table 1: advantages of internet banking to both customers and banks, source: kalra and nayaran (2017) to consumers to the bank • ability to operate different bank accounts at the same time • reduce time in executing different accounts operations • save operations costs • accessibility at any time in any geographical area • decrease in operational costs thus an increase in profitability • less paperwork due to computerized administrative tasks • 24 hours income generation • investment in personnel greatly reduced due to absence of physical agencies and investment in virtual banks table 2: banks that have recently reported cyber-attacks. source: bouveret (2018) internet banking informational role communicative role transactional role islam (2020): international journal of engineering materials and manufacture, 5(2), 62-67 64 institution year type of attack details federal reserve bank of cleveland 2010 data breach theft of 122,000 credit cards federal reserve bank of new york 2012 data breach theft of proprietary software code worth usd 9.5 million sveriges riksbank 2012 business disruption distributed denial of service (ddos) attack left the website offline for 5 hours banco central del ecuador 2013 fraud usd 13.3 million stolen from the account of city of riodamba at the central bank federal reserve bank of saint louis 2013 data breach publication of the credentials of 4,000 bank executives by anonymous central bank of swaziland 2014 fraud theft of usd 688,000.00 ecb 2014 data breach 20,000 email addresses and contact information compromised norges bank 2014 business disruption ddos attack on seven large financial institutions, resulting in suspended services during a day central bank of azerbaijan 2015 data breach theft of thousands of bank customers’ information bangladesh bank 2016 fraud the swift credentials of the bangladesh central bank were used to transfer usd 81 million from its account at the frbny. hackers tried to steal usd 951 million bank of russia 2016 fraud 21 cyber-attacks aimed at stealing usd 50 million from correspondent bank accounts at the central bank, resulted in a loss of usd 22 million bank of italy 2017 data breach hacking of email accounts of two former executives 3 challenges of internet banking internet banking has been emerged as one of the fastest and easiest way of banking. the threat of cyber security attacks become a great challenge for the internet banking and electronic commerce (e-commerce) industries. therefore, the security of this information system infrastructure is a major concern in the provision of effective banking services. the bbc news reported on 27 march 2015 that internet banking fraud rose by 48 percent in 2014 as compared to 2013 in the united kingdom (more, jadhav, & nalawade, 2015). the rise was due to increased development of computer malware and con artists tricking online banking users to give personal details that is common online threat known as phishing. another report by business insider india (jan 5, 2015), revealed that the number of cybercrimes in india increased from 22,060 in 2011 to 71,780 in 2012 (more, jadhav, & nalawade, 2015). the report also noted that the increased use of mobile phone in financial transactions will increase the internet banking security vulnerabilities to a great extent. international monetary fund (imf) in 2018 reported that more financial institutions around the globe are reporting cyber-attacks, data breaches, and frauds on their online services as shown in table 2 (bouveret, 2018). from this context, creating an information technology infrastructure that ensures optimized security of internet banking is critical. the current internet banking system relies on personal identification number (pin) authentication and unencrypted short messages (sms) and emails as the only security features in their internet banking systems. sundaram et al. (2019) further studied the current security protocols in internet banking and found that financial institutions use similar methods of authentication for all users. the measures employed ranged from telephone number, pin, mother’s maiden name, and simple passwords only systems. the problems with the structures now-a-days are inherent inside the setup of the communications and additionally within the computer systems itself. hackers have many unique methods that they can access these security protocols of internet banking. therefore, even though banking institutions have integrated security features in internet banking, the existing security protocols are not efficient. while a significant number of australians use internet banking, a large number continue to use bank conventionally. according to australia bureau of statistics (abs, 2016), only 21 percent of australian citizens are comfortable using the mobile banking despite having many benefits of online banking. moreover, age is a determinant of using internet banking. abs (2016) reported that 61 percent of australian citizens age 15 years and above used internet in 2014 and 2015 and 72 percent of them used the internet for conducting banking transactions. on the other hand, only 49 percent of australians aged 65 years used the internet and only a half used the internet for banking services. security concerns are the core reason for lower adoption of internet banking in australia. the groups who do not engage in internet banking have cited low trust in the system. at the same time, security remains a main concern for those who use the services in australia. given the many benefits of internet banking such as convenience, non-physical handling of money, speed, and cost reduction, this study will evaluate the current forms of security threats in the internet banking, investigate weaknesses in the current information security protocols of the enhanced information system security in internet banking and manufacturing 65 internet banking and propose an enhanced information system security for internet banking. as a result, individuals will trust internet banking and ensure many australians benefit from the new technology. 4 security risks in internet banking khan et al. (2016) stated that internet banking infrastructure can be attacked with different skills and persistence. communication and transitional roles of internet banking has been termed as the most vulnerable to security attacks. according to reserve bank of australia (2018), the most common cyber threats in australian banks are data breaches by stealing sensitive data by means of phishing, system disruption such as denial of service (dos) attack and financial attacks either through fraud or ransom. hsbc australia stated in their website that the most common cyber-attacks in australian banks are phishing, malware, business email compromise, text and phone scams. australian cyber security centre reported in 2016 that the most common threats in financial institutions are phishing and denial of service (dos) attack. internet banking may face some security threats including phishing, denial-of-service (dos) attack, password cracking, social engineering attack, man-in-the-middle attacks, and man-in-the-browser attacks. 4.1 phishing khan et al. (2016) focused on phishing where fraudsters use the communicative level of internet banking to send fraudulent emails that are created with the intention to deceive the systems users to disclose personal information. information including user passwords, pin, social identification, and date of birth, and credit card details have also been critical details for phishers. the study reported that one-way fraudsters are phishing is done by developing a website that exactly resemble the original bank site. once the customers enter their username and password, the attacker’s systems store the details for use in the original website of the bank (khan et al. 2016). 4.2 denial-of -service attack (dos attack) tabiaa et al. (2017) stated dos attack as the most common type of internet banking security risk after phishing. the authors described dos as an attack where the cyber criminals make internet banking network unavailable to its intended users. they temporarily or indefinitely disrupt services of a host connected to a bank computer (tabiaa et al. 2017). khan et al. (2016) further stated that dos attacks significantly degrade the internet banking service quality experienced by the legitimate users. the attackers inject and execute arbitrary code when performing a dos attack to give commands to the server and access critical information from the systems. 4.3 password cracking veras, collins, and thorpe (2014) stated in a study of semantic patterns of passwords that cyber attackers can involve a guess work to obtain personal information from internet. the attacker often tries many passwords and passphrases with the hope of eventually guessing the password correctly. in password cracking, tabiaa et al. (2017) revealed that cyber attackers check all possible passwords systematically until a correct one is found. veras, collins, and thorpe (2014) stated dictionary attacks, pattern guessing, and word list substitution as the most common types of password cracking. 4.4 social engineering attacks mouton et al. (2015) revealed that social engineering attack is more common with global connectivity of internet. this is the science of using social interaction to persuade an internet banking user to comply with a specific request from the attacker and the request involves a computer related trick. airehrour et al. (2018) in investigating social engineering in the new zealand banking system stated that cyber attackers use relationships and friendships to obtain information from their victims. the authors explored social engineering attack cycle which was first described by kevin mitnick (2002) as show in figure 2. 4.5 man-in-the-middle attacks kimwele et al. (2014) focused on studying threats associated with man-in-themiddle attacks in the mobile banking system. they found that this type of attack often targets the communicative level of internet banking which is normally achieved through sms and emails. the attacker will intercept messages in a public communication server and then retransmits them, substituting the message to a new but related version so that the two original parties appear to be communicating with each other. tabiaa et al. (2017) stated the attacker is usually a third party who has access to the communication channel between two end users. the attackers convince the two communicating parties that they have a secure channel but instead they access to all the encrypted messages. 4.6 man-in-the-browser (mitb) attacks a man-in-the-browser attack is performed by infecting a user browser with a browser add-on, or plug-in that executes malicious actions. generally, the attacker can perform anything the user can and can act on their behalf once user's machine is infected with malware. the attacker can perform any bank transfer that the user does while infected if the user logs into their bank account at that time. by the virtue of being invoked by the browser during web surfing, that code can take the control of the session and perform malicious actions without the user’s knowledge. islam (2020): international journal of engineering materials and manufacture, 5(2), 62-67 66 figure 2: social engineering attack cycle. source: airehrour et al. (2018) 5 research methodology in this study, a survey was conducted in australia as the research methodology. the targeted participants were bankers and internet banking users. the bankers were considered the most suitable informant, especially if these bankers also at a senior level in the overall organizational hierarchy. the questionnaires were sent to 200 participants and the response rate was good. 123 participants responded to this survey. the participants were asked about current forms of security threats in the internet banking, weaknesses in the current information security protocols of the internet banking and they were asked to propose an enhanced information system security for internet banking. based on the survey’s positive and negative responses, the security threats, and weaknesses in the current information security protocols in internet banking have been identified. finally, an enhanced information security for internet banking has been proposed. 6 results and implications of the study the most common security threats in internent banking are not pure technical attacks. 71 participants mentioned that phishing is the main threat in internet banking and they mentioned that password stealing, identity theft, denial-ofservice (dos) attacks and man-in-the-browser (mitb) attacks are the other security threats. 52 respondents stated that denial-of-service (dos) attack is the main security threat in internet banking while phishing, password stealing and identity theft are the other types of cyber attack in intenet banking. therefore, the most security threats that are identified for internet banking in this study are phishing, password stealing, identity theft, denial-of-service (dos) attacks and man-in-the-browser (mitb) attacks. cyber attackers often steal and accses to personal and bank security details. currently, banks have developed authentication protocols to mitigate cyber attacks in internet banking. an authentication is a method and a piece of information used to verify the identity of a person or organization when accessing networks with security constraints. the most common types of authentication in current online banking systems include, pin, passwords, identifiable picture, one time password (otp), finger and palm print, voice, signature, and facial recognition. kayode et al. (2017) stated that the most common methods of authentication using in current internet banking have low to medium security strength. the authors revealed only iris pattern have high security strength. sheikh and rajmohan (2015) stated now-a-days captcha is a common authentication protocol in internet banking. the authors however stated that the images used are too simple, making it very possible to obtain desired banking information using the ocr sofware. this study recommends that biometrics-based authentication is the enhanced security solution to address security issues in online banking. this is the use of personal physical and behavioral human features to identify the identity of internet banking user. some common features used include voice, fingerprints, facial paaterns, and typing cadence. this type of authentication is not transferable as with the case in passwords, pin, and mother maiden name. the findings of this study will challenge banking management to rethinks about their current authentication methods in online banking. the findings are also important for system developers who design and develop internet banking information technology infrastructure. 7 relevance to manufacturing industry industrial production relies upon secure digital connections with vendors, partners, and customers to stay relevant and competitive. these digitally connected industry has significant amount of cyber risk. all that sensitive data, communication channel and automatic processes multiply the opportunities for hackers by expanding the “surface area” exposed to cyber-attack. since digital systems are very much embedded in daily operations, the significant damage can be magnified from even a single security incident. industrial business processes are automated, digitized and streamlined. this data-driven, real-time operation creates more risks from autonomous machines and processes. these risks could occur from robots to automatic warehouse equipment to information systems that automatically carry out work with outsiders. to manage risks, industry need to develop pervasive cyber resilience that weaving cyber protection into all operations they perform at present and plan to perform in future. this paper recommends cyber security solutions that can help industry to make them cyber resilient. cyber resilient enterprises can operate safely under persistent threats and sophisticated attacks. they can strengthen customer trust and boost industrial production. 8 conclusions the number of cyber attacks have increased dramatically as more banks adopt internet banking. the technology have been adopted due to its benefits in increasing convinience of banking services, the potential to reduce operations costs in bank, and the perceived security. however, the current security models in mobile banking have some enhanced information system security in internet banking and manufacturing 67 weaknesses due to the persistent number of attacks. common types of security attacks in online banking systems include phishing, denial of service attcks, password cracking, social engineering attacks, man-in-the-middle attacks and man-in-the-browser attacks. it is important that banks rethink their authentication strategies. the limitation of this research is that this study was conducted in a single country only. the future research may be conducted in broad geographical areas in the world. acknowledgement the author is grateful to the bankers and the internet users in australia who participated in the survey as part of this research study. references 1. airehrour, d., vasudevan nair, n. & madanian, s. (2018). social engineering attacks and countermeasures in the new zealand banking system: advancing a user-reflective mitigation model. information, 9(5), 110. 2. australia bureau of statistics (abs, 2016). 8146.0 household use of information technology, australia, 2016-17. retrieved from: https://www.abs.gov.au/ausstats/abs@.nsf/mf/8146.0 3. acsc threat report. (2016). retrieved from: https://www.cyber.gov.au/sites/default/files/201904/acsc_threat_report_2016.pdf 4. bouveret, a. (2018). cyber risk for the financial sector: a framework for quantitative assessment. international monetary fund. 5. hsbc bank australia. (2020). protecting your business, cybercrime. retrieved from: https://www.business.hsbc.com.au/en-au/cybercrime 6. juraj dobrila university of pula. i. (2016). adoption of internet banking service within the corporate sector: evidence from newly acceded eu country. in the eu economic environment postcrisis: policies, institutions and mechanisms. juraj dobrila university of pula. 7. kalra, r. & narayan, b. (2017). e-banking: advantages, challenges and opportunities in the indian context. journal of management and technology, 7(1). 8. kayode, a., (2017). internet banking in nigeria: authentication methods, weaknesses and security strength. american journal of engineering research, 6(9), 226-231. 9. khan, m., khan, k., raza, a., & khan, e. (2016). analysis of electronic banking services & its issues in pakistan. european journal of business & management, 8, 1-8. 10. ling, g. m., fern, y. s., boon, l. k., & huat, t. s. (2016). understanding customer satisfaction of internet banking: a case study in malacca. procedia economics and finance, 37, 80-85. 11. luvanda, a., kimani, s. & kimwele, m. (2014). identifying threats associated with man-in-the-middle attacks during communications between a mobile device and the back end server in mobile banking applications. iosr journal of computer engineering (iosr-jci), 12(2), 35-42. 12. more, m., jadhav, m. & nalawade, k. (2016). online banking and cyber attacks: the current scenario. international journal of advanced research in computer science and software engineering, 5, 743-749. 13. mouton, f., malan, m. m., kimppa, k. k., & venter, h. s. (2015). necessity for ethics in social engineering research. computers & security, 55, 114-127. 14. novokmet, a. k., & tokić, i. (2016). adoption of internet banking service within the corporate sector: evidence from newly acceded eu country. in the eu economic environment post-crisis:policies, institutions and mechanisms. 15. ntseme, n., chukwuere, j. & onneile, j. (2016). risks and benefits from using mobile banking in an emerging country. risk governance and control: financial markets & institutions. 6. 10.22495/rgcv6i4c2art13. 16. rahi, s., ghani, m. & ngah, a. (2018). a structural equation model for evaluating user’s intention to adopt internet banking and intention to recommend technology. accounting, 4(4), 139-152. 17. ramavhona, t. c. & mokwena, s. (2016). factors influencing internet banking adoption in south african rural areas. south african journal of information management, 18(2), 1-8. 18. reserve bank of australia (financial stability review). (2018). box dcyber risk. retrieved from: https://www.rba.gov.au/publications/fsr/2018/oct/pdf/box-d.pdf 19. shaikh, a. a. & karjaluoto, h. (2015). mobile banking adoption: a literature review. telematics and informatics, 32(1), 129-142. 20. sheikh, b. a. & rajmohan, d. p. (2015). internet banking, security models and weakness. international journal of research in management & business studies (ijrmbs 2015), 2(4). 21. sundaram, n., thomas, c. & agilandeeswari, l. (2019). a review: customers online security on usage of banking technologies in smartphones and computers. pertanika journal of science & technology, 27(1). 22. tabiaa, m., madani, a. & el kamoun, n. (2017). e-banking: security risks, previsions and recommendations. international journal of computer science and network security, 17, 189-196. 23. veras, r., collins, c. & thorpe, j. (2014). on semantic patterns of passwords and their security impact. in ndss. https://www.abs.gov.au/ausstats/abs@.nsf/mf/8146.0 https://www.cyber.gov.au/sites/default/files/2019-04/acsc_threat_report_2016.pdf https://www.cyber.gov.au/sites/default/files/2019-04/acsc_threat_report_2016.pdf https://www.business.hsbc.com.au/en-au/cybercrime https://www.rba.gov.au/publications/fsr/2018/oct/pdf/box-d.pdf international journal of engineering materials and manufacture 2023 8(3) 75-87 https://doi.org/10.26776/ijemm.08.03.2023.03 s. m. z al-hady , m. r. islam, m. m. rashid department of mechatronics engineering faculty of engineering, international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: syedmdzakaria@gmail.com syedmdzakaria@live.iium.edu.my reference: al-hady el al. (2023). development of iot based automated dynamic emergency response system against fire incident in academic building. . international journal of engineering materials and manufacture, 8(3), 75-87. development of iot-based automated dynamic emergency response system against fire incidents in academic building syed mohammed zakaria al-hady, md rafiqul islam, muhammad mahbubur rashid received: 26 april 2023 accepted: 30 may 2023 published: 01 july 2023 publisher: deer hill publications © 2023 the author(s) creative commons: cc by 4.0 abstract the ongoing advancement of architectural and structural designs, high-ceiling spaces, special spaces have made fire disasters increasingly diverse and difficult to predict. it is demanding the need for improved firefighting systems. this study aims to address the need for improved firefighting systems in academic building by proposing the development of an iot-based automated emergency response website. the proposed system leverages iot technology, wireless and bluetooth sensor networks to gather real-time data from various sensors and devices installed in the site and uses machine learning algorithms to predict and prevent potential fire incidents. the system also includes an emergency response website that allows users to access real-time information about the fire incident, location, severity, and evacuation instructions. additionally, the proposed system incorporates building information modelling (bim) to optimize evacuation and rescue routes, providing early detection and accurate alarm capabilities, evacuation guidance for endangered individuals, and guidance for firefighters. the integration of bim allows the system to provide a three-dimensional visualization of the site, enabling a more efficient and effective response to fire incidents. overall, the proposed system aims to improve the safety and security through real-time monitoring and response capabilities. by leveraging the power of iot technology, machine learning algorithms and bim, the proposed system aims to reduce the impact of fire disasters by providing accurate and timely information, route optimization and facilitating effective evacuation and rescue efforts. keywords: building information modeling, iot, sensor, dijkstra algorithm, simulation 1 introduction around the world, modern industrial sites, office sites and academic buildings have grown more complex and augmented. given the structural characteristics of these sites, quick evacuation such as through emergency exits or evacuee guidance markers during blackouts caused by fire, building collapse, earthquakes, or building aging is a critical issue. uniform evacuation guidance, such as exit light is insufficient for guiding evacuees during a fire, causing them to take incorrect exits while buildings are on fire. existing emergency exit guides do not take the location of the fire in and out of the account and simply direct people to the nearest exit, which may result in significant secondary casualties if a fire occurs at the exit and evacuees are directed towards it. as a result, we must pay special attention to implementing new technology to combat fire disasters. the internet of things (iot), in conjunction with building information modelling (bim) and wireless sensor networks (wsn), is ideal for firefighting. iot has a high level of intelligence for maintaining many product categories, quantities, complex fire danger factors, and a wide range of fire monitoring and fighting equipment. iot has high scalability and resource-sharing capabilities for handling various complex business information. iot in conjunction with the wireless sensor network (wsn) plays an important role in fire alarm, fire control facility monitoring, and fire equipment management. the fire department's emergency response & rescue capabilities are effectively improved by it. this research will propose an iot-based intelligent fire emergency response system with decentralized control which is far more effective than the traditional noncommunicative signal-based evacuation technology. it can intelligently guide evacuees based on the location and time of a fire to reduce human life loss. development of iot based automated dynamic emergency response system against fire incident in academic building 76 2 literature review the recent surge of technological advancement in sensor-based networking systems has enriched studies based on iot systems and their mechanisms. most iot-based studies on firefighting in the last decade have discussed the following topics: general firefighting systematic plan, technological sensor development, improvement in sensor sensitivity and mechanism, and use of different parameters in fire identification (such as temperature, pressure, moisture content, etc.). 2.1 development of iot-based fire hazard solutions the “internet of things for smart cities” discussed only general iot features that can be implemented in smart city networks, but no recommendations for firefighting were given in it whereas folea and mois discussed low-power wireless sensors for online environmental monitoring, which combines wi-fi connectivity with ambient sensors, used for remote data collection and processing [1]. the use of narrowband iot (nb-iot) in intelligent fire protection systems, can significantly improve firefighting forces combat capability [2]. combined application features of iot technology based on fire-fighting business requirements discuss the fire-fighting iot systematic frame, planning of society fire-fighting safety management, and propose priority development points of society fire-fighting safety management, thereby providing a reference for technology research and development of iot technology in the field of society fire-fighting safety management [3]. an iot-based novel fire extinguishing monitoring and control system is proposed to acquire real-time information on fire extinguishing working conditions and improve the reliable prediction mechanism in a traditional fire monitoring system [4]. the novel system can obtain real-time data on the operation of fire extinguishing facilities, such as pipe flow, pressure, temperature, and humidity of the environment, current and voltage of the electric equipment, valve switch, relay action, and an alarming message [5]. the investigation of the design and implementation of a voc monitoring system using a zigbee wireless sensor network [6]. the consideration of gator tech smart house to be a programmable pervasive space [7]. the detailed discussion on the current state of smart homes and the discussion on the wsn-based smart sensors and actuators for intelligent building power management [8-9]. there are some investigations were conducted on the intelligent self-adjusting sensor based on zigbee communications for smart home services where the structure composition, design concept, and implementation approach has described [ 10]. byun, et al. [11] have made an investigation on a zigbee-based simulation process on a safeguarding sensor system for the real-time monitoring of wireless fire detection nodes. intelligent-based bridging components in the space where the distributed services have been working seamlessly and where the robots are sharing the missing information in the intelligent space [12]. the use of blockchain technology in an iot-based automated dynamic emergency response system for energy distribution can improve the efficiency, reliability, and security of energy distribution, leading to a more sustainable and resilient energy ecosystem [13]. a computer-aided visualization of rescue operations was applied, and the investigation novel concept of a fire hazard ranking distribution system based on multisensory technology [14]. the challenges of integrating a wireless sensor network and the internet of things for environmental monitoring can be improved by using wireless sensors in network-based forest-fire surveillance systems [15-16]. 2.2 bim model development in fire hazard situations in recent years, building information models (bim) have been widely used in building disaster prevention and relief management, and not only does it provide three-dimensional space for visualizing fire conditions and other emergencies [17-19]. the uncertainty of a building fire makes every second of the fire scene critical and the users can quickly determine the best escape route to deal with the fire using this information [20]. bim-based construction safety management system using ar and 4d simulation technologies. advances in civil engineering [21-22]. most of the current research on building fire escape focuses on path planning based on the current fire situation. however, due to many floors and complex internal space in high-rise buildings and large complex buildings, it is difficult to obtain the overall optimal escape path that carries on path planning only through the current location data and situation of a fire, lacking fire spreading and using the fire spreading data to correct the path [23-24]. although there have been some studies on escape paths in the case of fire spreading, they have primarily focused on fire rendering but the research on the emergency evacuation management system of a museum based on bim and virtual reality with little research on dynamically changing escape paths based on fire spreading simulation [25-27] 2.3 dijkstra’s algorithm in a fire escape situation the fire is sprawling and uncertain, and the trapped people are in constant motion. if the escape route planning was performed only by real-time personnel location and fire information, it may cause the current route to be opposite to the previous route with the fire spread and the escape proceeded [28-30]. as a result, it is hard to escape quickly from the fire scene for the problem of partial route detour. although there has been research on fire spread and path planning based on simulation data [31], there is a lack of processing to dynamically correct the escape path according to the fire spread data, so it is impossible to ensure the real-time escape path is optimal in the overall escape process [28]. moreover, people often escape at the same time in a real fire. and it will be more difficult to escape if people are in a panic. congestion and stampede tend to occur on stairs, resulting in unnecessary casualties [32]. al-hady, islam, m. r. and rashid, m. m. (2023): international journal of engineering materials and manufacture, 8(3), 75-87 77 cheng et al. used bluetooth and smoke sensors to obtain information about the fire scene in their study of building fire escape paths [33]. and then used the dijkstra algorithm for dynamic evacuation/rescue path planning, which successfully realized real-time dynamic path planning and navigation of building fires. similarly, chou et al. developed an integrated fire protection system with multiple scenarios for evacuation and rescue by employing the dijkstra algorithm to perform real-time dynamic path planning and constantly update the location nodes of trapped and rescuers [34]. in response to this problems, this paper is going to make a further study on the quick and safe escape from a building fire, and it will adopt iot based system for an effective escape path. for this effective communication a website is created using the bim model in conjunction with dijkstra’s algorithm, integrating fire information to simulate fire spread, the data of fire spread can be obtained and adjusted dynamically according to the real-time situation. this dynamic path analysis of the escape path for complex building fires can be realized and displayed in the bim model, which helps trapped people escape quickly. 3 methodology this proposal is divided into three phases that will be implemented simultaneously to achieve the main objectives. the execution of this research can be categorized as follows: 1. analyzing fire load and fuel arrangements in a typical building, investigating possible worst-case scenarios of fire phenomena in buildings during a fire. 2. examining the efficiency of dynamic exit signage during an emergency using a demo device, modeling a soft computing-based simulation process that can predict the level of emergency due to fire and occupants' flow. 3. integrating the main results from previous studies to produce an automated dynamic emergency response system that will be further developed to meet commercialization goals. 3.1 factors identification a concept is developed through a comprehensive literature review and the identification and evaluation of various components of an iot-based fire fighting system. it also aids in the extraction of preliminary factors that are widely used in various types of buildings, structures, and large areas shown in figure 1. 3.2 data collection and organization to create a building information modelling (bim), fire system sensor data and building planning data were collected. the general mustafiz tower at the military institute of science and technology, located in mirpur cantonment, bangladesh, was selected as the study site which has been shown in figures 2, 3 , and 4. this academic building comprises 10 floors, with the first floor being a lobby. participants were instructed to evacuate from the 3rd floor. as depicted in the figure, the building features one staircase, three elevators, one emergency exit, and a connecting bridge with the adjacent tower. to eliminate any issues with elevator scheduling, occupants on other floors were not permitted to use elevators during the experiments. participants were only allowed to use the staircases, emergency exit, and connecting bridge for the duration of the experiment. figure 1: research framework development of iot based automated dynamic emergency response system against fire incident in academic building 78 3.3 plan layout the floor and node plan diagram are drawn according to the building layout and fire system placements which are shown in figures 5, 6, and 7. the measurement of the classrooms, corridor, and washroom was taken physically during the experiment. figure 2: general mustafiz tower, mist, mirpur cantonment, bangladesh figure 3: student classroom figure 4: common space of the mist academic building figure 5: emergency exit and staircase al-hady, islam, m. r. and rashid, m. m. (2023): international journal of engineering materials and manufacture, 8(3), 75-87 79 figure 6: floor plan of the mist academic building figure 7: combined nodes as shown in figure 6, the building can be modeled as a “graph”, or a series of connected nodes and weighted edges. dijkstra’s algorithm is a computational algorithm that is commonly used to find the shortest distance between two nodes in a graph (with weighted edges), making it the perfect computational tool to find the optimal escape path from one specified location to another. the main advantage of the algorithm is that it can plan the shortest path between any two locations (when modeled as a graph) with the smallest computational time. this is important as in a large building with many locations, nodes, and possible escape paths, there may be a very large number of possible combinations that the iot system would need to compute if a “brute force” computation approach is used to find the shortest path, which may take far too long to compute in a real fire situation. the node-to-node distance is shown in table 1 below. development of iot based automated dynamic emergency response system against fire incident in academic building 80 3.4 planning the dynamic fire escape path 3.4.1 introduction and overview to demonstrate the application of iot systems in a real firefighting scenario, this paper will make use of a web-based (http://dynamicfireescape.com:9999/sp_problem), simulation software “dynamic fire fighting”, a purpose-built to test out fire scenarios. the software will be used to simulate three fire scenarios, which will be visually represented as graphs by the software. dijkstra’s algorithm will then be applied by the software to illustrate how an iot system may plan out an escape route. 3.4.2 simulation software a web-based simulation software was created to demonstrate the application of dijkstra’s algorithm as a proof of concept. this software takes a table of nodes and paths between the nodes as inputs (exactly in the format of table 1 and outputs a table outlining the fastest path from one selected node to another. this software can be accessed at (http://dynamicfireescape.com:9999/sp_problem). 3.5 executed simulations for a dynamic fire escape path refer to figure 7 consider now a building with sensors, entrances, and exits in the locations as shown. similarly, consider the evacuees and fires in the locations as shown in table 2. the following is table 2 of the scenarios that will be simulated for this demonstration. table 1: node to node distance figure 8: simulation software interface node to node distance (ft) node to node distance (ft) p1 – n1 20 p14 – n2 20 p2 – n1 39 p16 – n4 5 p3 – n1 5 p17 – n4 31 p4 – n1 31 p18 – n4 20 p1 – n2 39 p19 – n4 39 p2 – n2 20 p16 – n5 31 p3 – n2 31 p17 – n5 5 p4 – n2 5 p18 – n5 39 p5 – n3 20 p19 – n5 20 p6 – n3 5 p20 – n6 30 p7 – n4 20 p21 – n6 25 p8 – n4 5 p22 – n7 30 p9 – n4 39 p23 – n7 25 p10 – n4 31 e2 – n1 1 p7 – n5 39 e3 – n1 1 p8 – n5 31 n1 – n2 30 p9 – n5 20 n2 – n3 12 p10 – n5 5 n3 – n4 3 p11 – n1 5 n4 – n5 30 p12 – n1 31 n3 – n6 25 p13 – n1 20 n6 – n7 24 p14 – n1 39 e1 – n6 40 p11 – n2 31 e1 – n7 30 p12 – n2 5 p13 – n2 39 http://dynamicfireescape.com:9999/sp_problem http://dynamicfireescape.com:9999/sp_problem al-hady, islam, m. r. and rashid, m. m. (2023): international journal of engineering materials and manufacture, 8(3), 75-87 81 3.5.1 scenario 1 consider a case where, in the event of a fire breakout, there is an evacuee in the bottom left corner room, labeled node p20 in figure 7 as shown in figure 10 below, it is not clear whether evacuee p20 should take the exit ex1 through the red path (path a) or take exit ex3 through the black path (path b). there might be multiple paths in the real scenario under any hazardous situation. but we consider the shortest safety path, which will provide the most safety exist for the people. our shortest path is based on the hazard location, not only the shortest by distance. now, we can model this scenario exactly by using table 1 and inputting the values into the software, and we have the following information from figure 11. figure 9: simulation software interface table 2: simulation dvancement scenario evacuee node possible target exits nodes fire node remarks, the rationale for the choice 1 p20 ex3, ex1 to illustrate a simple scenario without a fire node. 2 p1 ex3, ex2 f1 to illustrate a scenario where the fire is blocking the exit. 3 p19 ex1, ex3 f6, f11 to illustrate the most complex scenario where multiple fire nodes are blocking multiple entrances of the rooms, and it is not clear what is the shortest path the evacuee should take. figure 10: possible escape paths of evacuee p20 development of iot based automated dynamic emergency response system against fire incident in academic building 82 as shown in figure 12, the shortest path from p20 to ex1 is 70 m. thus, we can see that path a to ex1 in figure 9 would be the shortest path available for the evacuee and will be recommended by the iot system to the user. in more complex and practical scenarios (such as scenario 3), the system will always calculate the distances to all exits (not just ex1 and ex3). however, the other exits are not calculated in this example as it is observable by the eye that they are not as viable as ex1 and ex3, and the focus of this example is the result of the calculations. indeed, all exits will be considered in the more complex scenario 3. 3.5.2 scenario 2 next, consider the case of an evacuee represented by node p1. as shown in figure 13, under normal circumstances, his quickest exit route would be to take the green path (path c) to exit ex3. however, consider the scenario where that path is blocked by a fire, represented by node f1. now, with the table row removed, we again run the algorithm with the ‘from’ node set to p1 and the target node set to ex3. now, as shown in figure 15, the algorithm suggests that p1 goes to n2 first, (which is the further room door) then to n1 (outside the room), and finally to exit e3, thus avoiding the fire. the algorithm now must re-calculate the quickest way out of the fire for the evacuee. in our model, n1 represents the room door that is being blocked by the fire node. so, to re-calibrate the software to incorporate the information of the fire node blocking the exit path, we remove the p1 n1 node from the node-to-node table 1, and the value for the same is shown in figure 14. as the data in fifure 11 is identical to table 1, only 10 out of 49 entries are shown to avoid cluttering this report with repetitive information. now, in the “solution” section of the software, we set ex3 and ex1 to be our target nodes, as shown in figure 10. the website now calculates the shortest paths to our target nodes using dijkstra’s algorithm and displays each walk from node to node on each row. figure 11: possible escape paths of evacuee p20 figure 12: calculated exit path from p20 to ex1 al-hady, islam, m. r. and rashid, m. m. (2023): international journal of engineering materials and manufacture, 8(3), 75-87 83 figure 13: quickest path to exit ex3 avoiding. figure 14: table row to be removed figure 15: evacuation path blocked by fire development of iot based automated dynamic emergency response system against fire incident in academic building 84 3.5.3 scenario 3 finally, with such frameworks in place, consider the most complex (and likely realistic) fire scenario as shown in figure 17, evacuee p19 trying to escape a fire, with fire nodes f6 and f11 actively blocking his path, and it is not clear how he should exit the building. this is the shortest path calculated by the software for all three exits combined. charting this path on the figure 7 diagram, we have path f in purple, as shown in figure 19. thus, through the application of dijkstra’s algorithm in a complex fire scenario, we have successfully guided an evacuee through the shortest path to an exit while avoiding fires along the way. now, in our software, we remove the node-to-node data connecting through f10 and f6 like in scenario 2. setting each of the exits ex1, ex2, and ex3 to be the target nodes, we get the following path in figure 17 for ex1. 3.6 system flow diagram the system's proposed module is shown below in figure 20 where signals from the fire alarm are sent to the database, which is then incorporated into the website, where the optimal route for escaping will be identified using the previous algorithm and the fire exit notification will be sent to all mobile users via mobile apps. graphically, this is represented now by the yellow path (path d) in figure 13. figure 16: calculated path to be taken around fire node f1. figure 17: complex fire scenario figure 18: calculated path for evacuee p19 to take given a complex al-hady, islam, m. r. and rashid, m. m. (2023): international journal of engineering materials and manufacture, 8(3), 75-87 85 figure 19: exit path for evacuee p19 figure 20: components of integrated control system module development of iot based automated dynamic emergency response system against fire incident in academic building 86 5 conclusions the suggested iot-based intelligent fire emergency response system can reduce casualties by recognizing the location of a disaster within a building to avoid directional confusion of emergency lights and improper evacuation assistance. by combining the intelligent and automated evacuation system with the central national disaster management agency, the intelligent emergency evacuation system can also aid firefighting by allowing for a speedy assessment of the exact location of the fire. it reduces casualties and evacuation time by directing evacuees to dispersed routes that avoid the location of the fire. future research will focus on expanding the system's applicability to include not just building disasters, but also maritime boats and evacuation within buildings, disaster safety via web or mobile application services, and preventive activities for optimal disaster recovery. 6 acknowledgement the authors would like to express their deepest gratitude to md wahidul islam, head of civil engineering department; prof dr tauhid ur rahman (ce); zabed sultan (dsw); and ahadul islam (program coordinator) at military institute of science and technology (mist) for allowing us to use mist building and its layout pictures for this study. references 1. mois, g., s. folea and sanislav, t. (2017). analysis of three iot-based wireless sensors for environmental monitoring. ieee transactions on instrumentation and measurement, 66(8), 2056-2064. doi: 10.1109/tim.2017.2677619. 2. li, m., li, x., chen, w., li, y., & zhou, w. (2022). internet of things for sustainable development: a survey. sustainable cities and society, 96, 103198. https://doi: 10.1016/j.scs.2021.103198. 3. kumar, n., reddy, v., & kumari, a. (2022). internet of things: a review of architectures, protocols, and applications. journal of ambient intelligence and humanized computing, 13(1), 555-578. doi: 10.1007/s12652021-03344-x. 4. al-fuqaha, a., guizani, m., mohammadi, m., aledhari, m., & ayyash, m. (2021). internet of things: state-ofthe-art review, applications, and research challenges. international journal of information management, 57, 102387. doi: 10.1016/j.ijinfomgt.2020.102387. 5. wang, l., xu, j., xie, y., liu, x., & han, z. (2021). internet of things (iot) and blockchain technology for supply chain management: a systematic literature review. international journal of production economics, 240, 108230. doi: 10.1016/j.ijpe.2021.108230. 6. li, tianxiang, and ping hou. (2019). application of nb-iot in intelligent fire protection system. international conference on virtual reality and intelligent systems (icvris). https://doi.org/10.1109/icvris.2019.00057. 7. akyildiz, i. f., w. su, y. sankarasubramaniam, and cayirci, e. (2020). wireless sensor networks: a survey, comput. netw.38(4), 393-422. 8. madhevan, b., and sakkaravarthi, r. (2017). modeling, simulation and mechatronics design of a wireless automatic fire fighting surveillance robot, 67(5). 9. madhavan, m., sakkaravarthi, r., singh, g. m., diya, r., and durgesh k. j. (2017). modeling, simulation, and mechatronics design of a wireless automatic fire fighting surveillance robot, defense science journal, 67(5), 572-580. https://doi: 10.14429/dsj.67.10237 2017, desidoc. 10. wu, x., zhang, x., jiang, y., huang, x., huang, g. g., & usmani, a. (2022). an intelligent tunnel firefighting system and small-scale demonstration. tunnelling and underground space technology, 120, 104301. https://doi.org/10.1016/j.tust.2021.104301. 11. byuan, d., jeon, b., noh, j, and park, s. (2012). an intelligent self-adjusting sensor for smart home services based on zigbee communications, ieee transactions on consumer electronics 58(3),794-802. https://doi:10.1109/tce.2012.6311320. 12. lu, f. and tian, g-h. (2012). the zigbee-based wireless sensor and actor network in intelligent space oriented to home service robot, school of control science and engineering, shandong university, jinan, china. https://doi: 10.4236/ijcns.2012.55037. 13. römer, k. u., & mattern, f. (2018). internet of things in action: examples and architectures. springer. https://doi: 10.1007/978-3-319-93356-2. 14. islam, m. r., rashid, m. m., rahman, m. a., mohamad, m. h. s. b., and embong, ahb. (2022). a review on blockchain technology for distribution of energy. international journal of engineering materials and manufacture 7(2), 61-70. https://doi.org/10.26776/ijemm.07.02.2022.03. 15. majumder, s., & choudhury, s. (2019). wireless sensor network for fire detection and fighting: a review. proceedings of the 3rd international conference on computing methodologies and communication. 370-377. springer. https://doi: 10.1007/978-981-13-9077-1_43. 16. sabino, m., spinsante, s., & gambi, e. (2019). wireless sensor networks for firefighting applications: a review. sensors, 19(24), 5477. https://doi: 10.3390/s19245477. 17. donald, n. (2017). raspberry pi projects for the evil genius. mcgraw-hill education tab 0071821589·9780071821582. https://www.researchgate.net/journal/ieee-transactions-on-consumer-electronics-0098-3063 http://dx.doi.org/10.1109/tce.2012.6311320 https://www.scirp.org/journal/articles.aspx?searchcode=school+of+control+science+and+engineering%2c+shandong+university%2c+jinan%2c+china&searchfield=affs&page=1&skid=0 http://dx.doi.org/10.4236/ijcns.2012.55037 al-hady, islam, m. r. and rashid, m. m. (2023): international journal of engineering materials and manufacture, 8(3), 75-87 87 18. flavian. carlos & gurrea. raquel & orús.carlos, (2009). web design: a key factor for the website's success. j. systems and it. 11. 168-184. 10.1108/13287260910955129. 19. li, h., zhao, w., & wei, s. (2021). research on wireless sensor networks in fire fighting applications. in proceedings of the 5th international conference on mechanical, control and computer engineering. 243-248. springer. https://doi: 10.1007/978-981-16-2393-3_37. 20. molano, a., rajkumar, r., and juvva, k. (2018). dynamic disk bandwidth management and metadata prefetching in a real-time file system. 10th euromicro workshop on realn.time systems (cat. no.98ex168), 204-213. 21. martinez-ortiz, a., lizcano, d., ortega, m. ruiz, l and lópez, g. (2016). a quality model for web components. 430-432. 10.1145/3011141.3011203. 22. the. n. k., patrick, s., bakar, a., saman, s. (2012). autonomous fire fighting mobile platform, procedia engineering, 41, 1145-1153 23. zou, p., zhang, g., wang, j., and zhang, x. (2018). bim-based construction safety management system using ar and 4d simulation technologies. advances in civil engineering, 1-12. https://doi: 10.1155/2018/1237472. 24. valvano, r. (2018). embedded systems: introduction to arm cortex-m microcontrollers. 5th ed., cengage learning. 25. ibrahim, a. m., venkat, i., subramanian, k. g, & kader, a. t. (2016). intelligent evacuation management systems: a review. acm transactions on intelligent systems and technology, 7(3/36), 1–27. https://doi.org/10.1145/2842630. 26. chen, t., li, y., & cao, y. (2019). research on the emergency evacuation management system of a museum based on bim and virtual reality. advances in civil engineering, 1-14. https://doi: 10.1155/2019/2149895. 27. zhu, x., zeng, x., zhang, j., sun, m., & hu, h. (2020). intelligent evacuation planning and simulation for building fire emergencies. automation in construction, 110, 103005. https://doi: 10.1016/j.autcon.2019.103005. 28. jun, w., di, z., meng, l., fang, x., hu-lin, s., and shu-feng, y. (2019). discussion of society fire-fighting safety management internet of things technology system. fifth international conference on intelligent systems design and engineering applications, 422-425. 29. hill, c., czajka, a., hazell, g., grillo, i., rogers, s. e., skoda, m. w., joslin, n., payne, j., & eastoe, j. (2018). surface and bulk properties of surfactants used in fire-fighting. journal of colloid and interface science, 530, 686-694. https://doi.org/10.1016/j.jcis.2018.07.023. 30. yi li, jianjun yi, xiaoming zhu, zhuoran wang and fangwen xu, (2016). developing a fire monitoring and control system based on iot, advances in intelligent systems research, 133. 31. zhu, x., zeng, x., zhang, j., sun, m., & hu, h. (2020). intelligent evacuation planning and simulation for building fire emergencies. automation in construction, 110, 103005. https://doi: 10.1016/j.autcon.2019.103005. 32. pinar, y., zuhair, a., hamad, a., resit, a., shiva k., and omar, a. (2016). wireless sensor networks (wsns). ieee long island systems, applications, and technology conference (lisat), 1-8, doi: 10.1109/lisat.2016.7494144. 33. cheng, m., xu, j., & li, m. (2017). study on fire evacuation path based on bluetooth and smoke sensors. journal of physics: conference series, 790(1), 012102. https://doi: 10.1088/1742-6596/790/1/012102. 34. chou, t.-h., lin, c.-c., & chou, c.-c. (2019). integration of the evacuation and rescue system for the high-rise building. journal of physics: conference series, 1153(1), 012027. https://doi: 10.1088/17426596/1153/1/012027. https://dl.acm.org/toc/tist/2016/7/3 https://doi.org/10.1145/2842630 international journal of engineering materials and manufacture (2018) 3(2) 87-97 https://doi.org/10.26776/ijemm.03.02.2018.03 s. a. suffian 1 , a. a. sidek 2 , t. matsuto 3 , m. h. al-hazza 4 , h. m. yusof 5 and a. z. hashim 6 1,2,4 department of materials and manufacturing engineering 5 department of mechatronics engineering international islamic university malaysia, po box 10, 50728 kuala lumpur, malaysia 3 laboratory of solid waste disposal engineering, hokkaido university, japan 6 myra chicken farm and services, kalumpang, hulu selangor, malaysia 1 e-mail: syakiraafiqah93@gmail.com, 2 e-mail: atiahas@iium.edu.my, 3 e-mail: matsuto@eng.hokudai.ac.jp 4 e-mail: muataz@iium.edu.my, 5 e-mail: myhazlina@iium.edu.my, 6 e-mail: awie2k@gmail.com reference: s. a. suffian, a. a. sidek, t. matsuto, m. h. al-hazza, h. m. yusof and a. z. hashim (2018). greenhouse gas emission of broiler chicken production in malaysia using life cycle assessment guideline: a case study. international journal of engineering materials and manufacture, 3(2), 87-97. greenhouse gas emission of broiler chicken production in malaysia using life cycle assessment guidelines: a case study syakira afiqah suffian, atiah abdullah sidek, tohishiko matsuto, muataz hazza al-hazza, hazlina md yusof and abdullah zawawi hashim received: 24 march 2018 accepted: 18 may 2018 published: 30 june 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract the aim of this research was to evaluate the level of greenhouse gas emission from broiler chicken farming industry in malaysia. in order to achieve that, life cycle assessment method was chosen as a framework to complete the task. a case study was conducted at a broiler chicken farm to gather the data and information related to the broiler chicken production. cradle-to-gate assessment including distribution stage was conducted based on the iso14040/1044 guidelines. inventory data for this case study was gathered in collaboration with one of the selected case study broiler chicken farm company. greenhouse gas emission that consists of several most affected gases such as carbon dioxide, methane and nitrous oxide was studied. result shows that the highest carbon dioxide emission came from manure, which accounted for 1,665,342 kg co2 equivalent per total broilers while the highest methane emission came from feed, which accounted for 126,207.84 g ch4 equivalent per total broilers. for nitrous oxide emission, the highest values came from bedding which accounted for 20,316.87 g n2o equivalent per total broilers in the commercial modern broiler chicken farm. in this case study, it can be concluded that manure gives the most prominent effect to the greenhouse gas emission followed by feed and bedding materials. keywords: greenhouse gas emission, broiler chicken production, life cycle assessment. 1 introduction energy and ecological concerns are intricately connected to the supply chains of numerous products. greenhouse effect (global warming and climate change) as impact category is the harmful ecological consequences to the global climate caused by anthropogenic activity (walter and birgit, 2014). increased community awareness of the dangers postured by global warming has driven towards more prominent concern on top of the impact of anthropogenic carbon emissions to the worldwide climate. approximately, current level of carbon dioxide (co2) in the atmosphere is approaching 409.97 ppm (mauna loa, 2018). from the past of few decades, the environmental concerns has been focusing on companies, government and public. this development was noticeable within regulatory restrictions on industrial contaminant discharges. these strategies concentrates on the treatment and secure disposal of residues and are still in use nowadays when regulatory compliance requirements to be guaranteed. in recent years, there has been substantial awareness in pollution prevention (p2) or cleaner production (cp), in expansion towards pollution prevention control. p2 or cp involves the utilization of methodologies, which attempt to provide essentially clean solutions in order to minimize the necessity of waste management (raymond et.al 2009). according to beauchemin et.al (2010) and garnet (2010), livestock sector is the most prominent environmental burdens and responsible for 18% of global greenhouse gasses (ghg) emissions mostly due to the outcome of the greenhouse gas emission of broiler chicken production in malaysia using life cycle assessment guideline: a case study 88 farm activities throughout all the stages of the livestock product lifecycle. life cycle assessment (lca) is recognized as the most significantly global methods for assessing the environmental impacts of food products (roy et.al 2009; jhony et al 2017; sonko, 2018). the technique assess the environmental aspects and potential impacts of a product’s entire lifecycle production chain (iso 14040:2006). lca is the favourite method of environmental evaluation because it is the most robust and comprehensive methodology accessible, particularly in environmental research area. regarding of its record, numerous of authors that conduct environmental assessment choose lca method as a guideline to study the impact of wide range of food products such as dairy products (gonzales et.al 2014), broiler chicken in varamin city (talayeh et.al 2016), broiler chicken in united kingdom (leionen et.al 2012), broiler chicken in france (seguin et.al 2011) and broiler chicken in australia (wiedemann et.al 2012). malaysia is one of the major producers of poultry in the asia pacific region with export approximately 57.39 million live birds and 13.94 thousand tons of chicken meat to singapore and some middle east countries (orissa, 2017). the consequences of having large production of broiler chicken industry have given the negative impact on the environment. greenhouse gas emission (ghg) from the broiler production has increased the potential of global warming and resulted in warmer temperature. ghg emission contains few dangerous gases including methane (ch4), carbon dioxide (co2), nitrous oxide (n2o) and ammonia (nh3). therefore, there is a need to investigate the environmental impact especially on greenhouse gas emission (ghg) of the broiler chicken production to produce a sustainable and green production system. 2 background 2.1 broiler chicken production malaysian poultry industry has undergone a transformation over the last decade (roger, 2010). according to bernama (2017), deputy prime minister, datuk seri dr ahmad zahid hamidi reported that currently malaysia has been exported about 7% of 1.5 million broiler chicken a day. he urged broiler chicken processing companies to increase output up to 28% for the world market to gain maximum financial profit. report from department veterinary service (2017) indicated that chicken meat is considered the cheapest source of meat protein and the most popular among consumers in malaysia because there are no dietary prohibitions restrictions against the consumption of the meat. figure 1 shows the statistic of broiler chicken production in malaysia from 2004 to 2017. based on figure 1, the statistic of broiler chicken production has been increasing tremendously every year. this shows a good sign for the development of poultry industry. national broiler production in malaysia was dominated by broiler contract farming as much as 75%. it is monopolised by several companies and their operations are divided into five categories: grandparent, broiler parent, layer parent, commercial broiler and commercial layer as shown in table 1 (syauqi et.al, 2015). grandparent is a company that specialize in selective breeding meat chickens. normally they purchase the stock from handful company that based in the us and uk. broiler is young meat type that is raised normally for 9 to 12 weeks before sending to the market or slaughterhouse while layer is a mature female chicken that kept for egg production and called as laying hens. figure 1: statistic of broiler chicken production in malaysia (2004-2017) (department veterinary services, 2017) table 1: statistics of chicken production in peninsular malaysia (2010-2013). (syauqi et.al 2015) types of operation number of companies number of farms population (million) grand parent 4 4 0.90 broiler parent 23 79 11.35 syakira et al., (2018): international journal of engineering materials and manufacture, 3(2), 87-97 89 layer parent 5 14 0.31 commercial broiler individual/contract ±2600 118.52 commercial layer individual/contract ±300 47.35 the case study farm falls into commercial broiler category which gives the highest percentage of production among all chicken production. according to department of veterinary services (2018), parent stock (ps) farms stock were supplied 100% by four grandparent stock farms in 2016. currently, the parent stock (ps) farms in peninsular malaysia has been decreasing from 23 in 2013 to 22 farms in 2017. these farms produce more than 839.08 million broiler day-old-chicks in 2016. cobbs and ross are the major chicken breeds used in these farms. there are around 2,403 broiler farms in peninsular malaysia producing around 818 million birds in the same year. figure 2: total commercial broiler farm in peninsular malaysia (department veterinary services, 2017) figure 2 highlighted the distribution of commercial broiler farms around peninsular malaysia with johor has the most farms and led by perak where the case study broiler farm is located. due to severe market competition between the chicken industries, the number of farm companies has been reduced but are getting bigger in production capacity. as seen on table 1 and figure 2, number of farms decrease from 2600 in 2013 to 2403 in 2016. however, the production capacity increased from 118 million in 2013 to 818 million in 2016. 2.2 life cycle assessment life cycle assessment standards iso 14040 and iso 14044 belong to the iso 14000 family concerning various aspects of environmental management. the lca framework according to iso 14040:2006 in figure 3 proposed four components of lca methodology: goal and scope definition; inventory analysis; impact assessment and improvement analysis. each component in turn has a set of specific constituent activities. greenhouse gas emission of broiler chicken production in malaysia using life cycle assessment guideline: a case study 90 figure 3: lca phases according to iso 14040:2006 (2017) the lca framework is introduced with the recommendation of iso 14040:2006 as shown in figure 3. goal and scope definition describes the functional unit chosen, system boundary of research area and the description of the system that need to be studied. this followed by inventory analysis, which defines the input and output of the material involved in the research area including the measurement unit. during the collection of inventory data, there is a need to do material flow analysis so that the input and output material are both balance. the most crucial part in lca methodology is impact assessment where it assess the product system inventory’s result and provide understanding to its environmental significance followed by interpretation. there has been numerous of authors that conduct environmental assessment choose lca method as a methodology to study the impact of wide range of food products such as dairy products (gonzales et.al 2014), broiler chicken in varamin city (talayeh et.al 2016), broiler chicken in united kingdom (leinonen et.al 2012), broiler chicken in france (seguin et.al 2011) and broiler chicken in australia (wiedemann et.al 2012). 3 methodology 3.1 goal and scope definition the current analysis and report follows the iso 14044 guidelines (iso 14040:2006). the aims of this study were to (1) to evaluate the greenhouse gas emission (ghg) of case study broiler chicken farm and (2) to identify materials/process with major contributions to ghg of broiler chicken production. in order to evaluate the greenhouse gas emission (ghg), life cycle methodology was used and the study covered through a cradle-to-gate perspective from the transportation of one day old broiler chicken into the broiler farm until the transportation of the manure to the plantation farm. the functional unit of 2.5kg broiler chicken meat was chosen because it is the amount of chicken meat that contains the recommended daily protein supply for an average family (six people) and it is the average weight of a broiler chicken available for consumption in the market. the calculation was made using the greenhouse gas emission factor obtained from the official website of environmental protection agency (epa). the study only takes the greenhouse gas emission into account and is calculated according to ipcc 2007 using a 100 year time span. using ipcc 2007, 1g n2o and 1g ch4 correspond to 298g and 25g co2 respectively. 3.2 description of the system and system boundaries an overview of the flow diagram of modern chicken farming supply chain is given in figure 4. starting from hatchingegg farm then to hatchery proceed to broiler farm and lastly to slaughterhouse or supplier. syakira et al., (2018): international journal of engineering materials and manufacture, 3(2), 87-97 91 figure 4: process flow diagram of modern chicken farming supply chain in malaysia figure 4 shows the process flow diagram of commercial modern chicken farming supply chain in malaysia. hatching egg farm is where all layer hens are trained to produce eggs. these eggs will then transferred to hatchery where the eggs are hatched under artificial condition. when day-old chicken were produced, they will then transferred to broiler farm for fattening process and then lastly to slaughterhouse. system boundaries will only limited to the broiler farm where the upper boundary is the transportation of inputs (i.e feeding material, one-day-old broiler chicks, and bedding materials) and the lower boundary is the transportation of outputs (i.e matured broiler chicken and manure). the case study company (myra farm & services) only received and handled one day-old chicken from hatchery farm and reared them until they are ready enough to be transferred to the next chainslaughterhouse or chicken supplier. the whole farm consists of four houses where each house accommodates approximately 24,000 to 26,000 broilers. production systems of the broiler started when the broiler chicks arrived to the farm where they are placed in a containment area with controlled temperature and sufficient amount of feed. usually, the chicken takes about 35-40 days to achieve specific weight (normally 2.5-3kg) and will then distributed to the nearest market. 3.3 material flow system of the broiler chicken production system the broiler chicken farm processed around 100,000 chicks with approximately 40-42 gram weight of each broiler per batch. each year, they can make a maximum of four batches in which will be approximately 400,000 broilers per year. a material flow diagram was shown in figure 5 to indicate the amount of materials needed in the system. numbers shown in the diagram is the average values per batch of the broiler chicken. figure 5: material flow of broiler chicken production system greenhouse gas emission of broiler chicken production in malaysia using life cycle assessment guideline: a case study 92 the broiler chicks are transported from hatchery to the broiler farm by using lorry that needs a total of 10 trips to complete the transportation process. before the broilers arrived in the farm, all possible inputs must be prepared for example feed, bedding, and clean environment for the broilers to live in. normal broilers (weight approximately 2.3 to 2.5 kg) need 18 pounds (8.2kg) of water and 10.5 pounds (4.7kg) of feed to survive throughout their lifecycle in the farm. the volume of bedding used is one of the important elements for the broilers so that it can absorb the moisture from litter and waste water. for the most of the cases, the bedding will be in 7 to 10cm deep, which will give about 292.56 tons of shaving wood and bark consumption. electricity input was calculated by multiplying the usage of fan, light and pump with operation hours. approximately a total of 29665.63kwh was used for entire lifecycle of broiler chicken per batch. when the broilers achieved their minimum weight target, which is 2.5kg, they will be send to slaughterhouse for the next process while the broiler farm will then continue cleaning to prepare for the new batch of broilers. approximately, 106.016 kilo litre of water and detergent were used in the cleaning process. the output parameters, manure and bedding volume were calculated based on estimation of number bags of manure being sold to external vendors. these bags can load a maximum of 30 kg of manure and being sent to various vendor locations depending on order. this broiler farm recorded a mortality rate between 3 to 5%, which is considered acceptably low. mortality rate above 8% is considered to be high and cause of alarm. above 8% of mortality rate will be considered as high. mortality causes of broiler chicken is normally due to the changes in weather condition and the quality of feed given. the only wastewater from broiler chicken production in this case study farm was from cleaning activities and is estimated to be around 106.016 kilo litre. 3.4 inventory analysis the broiler chicken farm was assessed and inventory data is collected to quantify the inputs outputs of the production system.. for inventory analysis, data were obtained by taking average measurements and readings to analyse the results. table 2 shows the main parameters corresponding to the broiler chicken farm under assessment. the selection of broiler breed by the case study farm is based on live production costs and the broiler rapid growth (cobb, 2017). according to lobago et.al (2003), cobb 500 had better overall performance with relatively higher marginal revenue and lower marginal cost compared to ross in the present small-scale production system in debre zeit. for every batch, the farm will receive a total of 106,000 a day-old broiler chicks with fattening period between 35 to 40 days, the feed intake of these broilers during the maturity phase is around 4.7kg per broiler and the expected final weight for market is around 2.5kg. table 3 presented the inventory data for each process within the boundary production system. the values shown in the table 3 is the average consumption of the broilers throughout their life cycle in the farm. for example transportation of broilers in from desaru, johor which required 5 hours of transportation time. broiler manure was transported to cameron highland, pahang and feed materials with broiler out were transported to port klang, malaysia’s premier port. information on feed materials was obtained from literature (weidema, 2013). amount of water, electricity, animal bedding and cleaning agents were recorded based on average consumption of the broilers per batch. 4 result and discussion 4.1 life cycle impact assessment in life cycle assessment guideline, life cycle impact assessment (lcia) is identified as one of the important scientific phase. lcia phase according to iso 14040 and 14044 is composed of fixed and optional elements. selection of impact categories, category indicators and characterization models were included in fixed elements for lcia. there are also parts f optional element which is assignment of lci results as the classification factors and calculation of category indicator results as the characterization factor. table 2: parameters used by the broiler farm variable closed house broiler broiler breed type cobb500 average age (until maturity)(days) 35-40 days average feed intake (kg/broiler) 4.7 kg average final weight (kg/broiler) 2.5 kg average mortality rate (%) 3 % number of broilers per batch 106,000 type of bedding bark, sawdust amount of bedding (kg/broiler) 2.76kg syakira et al., (2018): international journal of engineering materials and manufacture, 3(2), 87-97 93 table 3: inventory data of inputs in the broiler farm. input unit transportation (km) broiler in (desaru-kalumpang) broiler out (kalumpang-port klang) feed (port klang-kalumpang) manure (kalumpang-cameron highland) 2395 1400 424 280 feed (kg) maize soybean wheat branula fungicides 159,000 162,180 127,200 29,680 water (liter) 869,200 electricity (kwh) 29,665.63 broiler bedding (kg) bark sawdust 101,760 190,800 gas (mj) 1696 cleaning agents (l) 71.02 4.1.1 selection of impact categories, category indicators and characterization models from the life cycle inventory analysis results, the class that representing environmental issues concern or normally being assigned as impact category must be identified according to iso 14044. in order to represent the impact category, an impact category indicator was defined and falls into classification factor. characterization factor is a factor that derived from a characterization model, which is applied to convert an assigned inventory analysis result to the common unit of the category indicator. according to figure 6, principle of classification and characterization in the phase life cycle impact assessment was mentioned. this research paper will only focusing to one category of ghg factor, which is global warming potential (gwp). in order to investigate the climate change, it is important to use factors published by the ipcc (intergovernmental panel on climate change) especially owing to varying knowledge and subsequent assessment of indirect impacts. climate change can be investigate by defining the greenhouse effect and calculate the emissions to determine the gwp. figure 6: principle of classification and characterization in the phase life cycle impact assessment 4.2 global warming potential (gwp) global warming potential (gwp) is a measure on how much the energy emissions of 1 ton gas will absorb over a given period time. the unit is normally in carbon dioxide equivalent (co2 eq). effect of high ghg emission will lead to high global warming potential hence caused the unstable climate change. 4.2.1 greenhouse gas emission greenhouse gas emission usually emitted from the combustion process. co2 account the major percentage of emission in greenhouse gas emission. all organizations ought to account for all co2, ch4, and n2o emissions associated with stationary combustion as advised by epa (2014). in some cases, the relative emissions contributions of each gas, ch4 and n2o are excluded by assuming that they are not material. the method used to calculate co2 emissions can also be used to calculate emissions of ch4 and n2o with tolerable accuracy when applying appropriate ch4 and n2o emission factors. greenhouse gas emission of broiler chicken production in malaysia using life cycle assessment guideline: a case study 94 4.2.2 greenhouse gas emission factor emission factor of greenhouse gas emission were obtained from environmental protection agency. these emission factors was proven as one of the methodology to calculate greenhouse gas emission (nicholas et.al 2017). there are few methods available such as waste reduction model (warm) and other lca software. however, this method was the easiest way to estimates the greenhouse gas emission from the activities carried out in the broiler farm. according to table 4, activities and materials in the broiler farm had their own emission factor based on environmental protection agency guideline. for carbon dioxide and methane, the highest emission factor came from manure which is 4.2kg co2/kg and 318 g ch4/ton while for nitrous oxide emission, bedding which consist of wood and barks gives the highest emission factor which is 63 g n20/ton. table 4: greenhouse gas emission factor (environmental protection agency, 2015) type of material/activity carbon dioxide emission (kg co2 eq/ton) methane emission (g ch4 eq/ton) nitrous oxide emission (g n2o eq/ton) transportation (diesel) 2.65 kg co2 / liter 0.0333 g ch4/miles 0.0134 g n2o/miles water 0.8 kg co2/m 3 1.25 g ch4/m 3 0.125 n2o/m 3 feed (agricultural products) 3.2 kg co2/kg 264 g ch4/ton 35 g n2o/ton electricity 1.0 kg co2/kwh 0.0109kg ch4/mwh 0.0083kg n2o/mwh manure 4.2 kg co2/kg 318 g ch4/ton 42 g n2o/ton bedding (wood and wood residuals) 1.64 kg co2/kg 126 g ch4/ton 63 g n20/ton 4.2.3 greenhouse gas emission results table 5 illustrates the greenhouse gas emission results after using all the variables given in the table of emission factor and formula. the study was ought to prove the activity or material that contribute the most of greenhouse gas emission to the environment. the results shows that manure gives the total emission of carbon dioxide highest compared to other activity. carbon dioxide gas was identified to be 1 year kg co2 equivalent per kg ghg. for the methane emission it was shown that feed contribute to the most of the methane gas which is identified to be 25 year kg co2 equivalent per kg ghg. last emission was being studied is nitrous oxide emission and activity that contribute the most is bedding materials. nitrous oxide was identified to be 298 year kg co2 equivalent per kg ghg. according to the results obtained from figure 8, activities and materials in the broiler farm which consist of manure, bedding, electricity, feed, water and transportation were examined to investigate their effect on greenhouse gas emission. the result shows that manure gives the highest percentage for greenhouse gas emission (ghg) followed by feed, bedding, transportation activity and electricity. water give the lowest value to the greenhouse gas emission compared to other materials and activities. manure was known as organic matter and derived from broilers faeces throughout their lifecycle in the broiler chicken farm. broiler chicken manure is the source of direct gaseous emissions of ammonia (nh3), nitrous oxide (n2o), and to a lesser extent, methane (ch4), which occurs during housing, storage, and land spreading (owen and silver, 2015). there are several factors that makes manure as the prominent materials that gives the highest greenhouse gas emission which are manure storage and the handling practices. in order to produce a sustainable broiler chicken production system, there is a need to overview the manure management practices so that the percentage of greenhouse gas emission can be reduced and hence reducing the global warming potential. table 5: greenhouse gas emission from broiler chicken production activity/material carbon emission (kg co2 eq) methane emission (g ch4 eq) nitrous oxide emission (g n2o eq) transportation 115,289.12 93.092 37.46 water 695.36 1086.5 108.65 feed 1,529,792.0 126,207.84 16,732.1 electricity 29,665.63 323.36 246.22 bedding 479,798.4 40,633.74 20,316.87 manure 1,665,342 126,090.18 16,653.42 syakira et al., (2018): international journal of engineering materials and manufacture, 3(2), 87-97 95 figure 7: results of ghg emission; a) carbon emission b) methane emission c) nitrous oxide emission figure 8: greenhouse gas emission percentage according to activities in the broiler chicken farm 5 conclusions in conclusion, the greenhouse gas emission of the case study broiler production has been examined and identified using life cycle assessment methodology. the presence of high greenhouse gas emission will result on warmer earth temperature and lead to uncontrollable climate change such as ocean acidification, smog pollution and ozone depletion. malaysia has taken this matter seriously when the government came out with tenth malaysia plan to reduce the greenhouse gas emission by 45% by 2030 which is the most recent policy of environmental plan (miti, 2017). manure is identified as the most prominent factors that contribute to high greenhouse gas emission. sources of greenhouse gas emission in the farm have been identified to be mainly carbon dioxide co2, methane ch4 and nitrous oxide n2o. much of the greenhouse gases (ghg) generated from this research is primarily from the process of handling and storing faeces of the broilers. this research showed: greenhouse gas emission of broiler chicken production in malaysia using life cycle assessment guideline: a case study 96 1. the highest carbon dioxide emission came from manure, which accounted for 1,665,342 kg co2 equivalent per total of broilers in the commercial modern broiler chicken farm. 2. the highest methane emission also came from feed and manure, which accounted for 126,207.84 g ch4 equivalent per total broilers in the commercial modern broiler chicken farm. 3. the highest nitrous oxide emission came from bedding materials, which accounted for 20,316.87 g n2o equivalent per total broilers in the commercial modern broiler chicken farm. 4. in 2009, malaysia has announced voluntary commitment to reduce carbon emission by 40% of its greenhouse gas emission by 2020 hence exposing the research gap on how we actually can reduce it from poultry side. 5. therefore, an examination on how much the total emission of greenhouse gas emission was studied before finding ways to reduce it. acknowledgement this research was funded by ministry of higher education (mohe) through fundamental research grant scheme (frgs 16-019-0518), to which the authors are grateful. special thanks also goes to all workers from case study broiler farm in helping the author getting more information on broiler chicken production. references 1. beauchemin, k. a., janzen, h. h., little, sm., mcallister, ta., mcginn, sm. (2010). life cycle assessment of greenhouse gas emissions from beef production in western canada: a case study. agric. system. 103, 371-379. 2. cobb, v. (2017). generation of process: cobb500. http://www.cobb-vantress.com/products/cobb-500. (accessed on december 2017). 3. daily co2 records. (2018, march). retrieved from: https://www.co2.earth/daily-co2. 4. deborah, nh., thomas, de. (2009). a life cycle assessment of portland cement manufacturing: comparing the traditional process with alternative technologies. journal of cleaner production 668-675. 5. de varies, m., de boer, ijm. (2010). comparing environmental impacts for livestock products: a review of life cycle assessment. livestock science 128, 1-11. 6. department of veterinary service (dvs), 2017. http:// www.dvs.gov.my (accessed on 18 january 2018). 7. deputy prime minister malaysia aims to export 30% of broiler chickens by 2030. available at: http://www.thepoultrysite.com/poultrynews/39514/dpm-malaysia-aims-to-export-30-of broiler-chickens-by2030/ 8. environmental protection agency. (2015). emission factors of greenhouse gas inventories. https://www.epa.gov/sites/production/files/2015-07/documents/emission-factors_2014.pdf (accessed 23 november 2017). 9. garnett t. (2009). livestock-related greenhouse gas emission: impacts and option for policy makers. environmental science policy 12,491-503. 10. garnett t. (2011). where are the best opportunities for reducing greenhouse gas emissions in the food systems (including food chain)? food policy 36,523-532. 11. gonzales, gs., gomez, fz., dias, ac., feijoo, g., moreira, mt., arroja, l. (2014). life cycle assessment of broiler chicken production; a portuguese case study. journal cleaner production 74, 125-134. http://dx.doi.org/10.1016/j.jclepro.2014.03.067. 12. iso 14040:2006, iso 14040:2006 2017-environmental management; life cycle assessment: principle and framework. iso.org. http://www.iso.org/standard/37456.html. (accessed 13 june 2017) 13. jhony, jl., alberto, a. a., luis, fm., catherine, ap., jorge, rp., jose, or. (2018). environmental impact assessment of chicken meat production via an integrated methodology based on lca, simulation and genetic algorithms. journal of cleaner production, 174;477-491. 14. klopffer, w. (1997). life cycle assessment-from the beginning to the current state. environmental science pollution research., 4, 223-228. 15. leiononen, i., williams, ag., wiseman, j., guy, j., kyriazakis, j. (2012). predicting the environmental impacts of chicken systems in the united kingdom through a life cycle assessment: broiler production systems. poultry science 91:8-25. 16. lobago., melese., mideksa., bizunesh., tibbo., markos. (2003). comparative performance of two broiler hybrids (cobb-500 and ross) under small-scale production system in debre zeit, central ethiopia. bulletin of animal health and production in africa. bulletin des santé et production animales en afrique. 51. 83-93. 17. martins, c. (2014). poultry business: feasibility study on poultry farming in nigeria., 2014. https://martinslibrary.blogspot.com/2014/11/poultry-business-feasibility-study-on.html (accessed on 28 november 2017) 18. ministry of international trade and industry (miti). (2017) malaysia and the united nations framework convention on climate change (unfcc)-the paris agreement. trade and industry related emerging issues division. http://www.cobb-vantress.com/products/cobb-500 https://www.co2.earth/daily-co2 http://www.dvs.gov.my/ http://www.thepoultrysite.com/poultrynews/39514/dpm-malaysia-aims-to-export-30-ofhttps://www.epa.gov/sites/production/files/2015-07/documents/emission-factors_2014.pdf http://dx.doi.org/10.1016/j.jclepro.2014.03.067 http://www.iso.org/standard/37456.html https://martinslibrary.blogspot.com/2014/11/poultry-business-feasibility-study-on.html syakira et al., (2018): international journal of engineering materials and manufacture, 3(2), 87-97 97 19. nikolas, hill., rebekah, bramwell., billy, harris. (2017). 2017 government ghg conversion factors for company reporting. department for business energy & industrial strategy (beis). 20. owen, j. j., & silver, w. l. (2015). greenhouse gas emissions from dairy manure management: a review of field‐ based studies. global change biology, 21(2), 550-565. 21. poultry sector in south east asia: iowa economic development authority, (2017). orissa international pte.ltd.2017. 22. raymond, rt., alvin, bc., michael, rip., joel, qt. (2009). life cycle design, planning and assessment. igi global. 23. reckmann, k., traulsen, i., krieter, j. (2012). environmental impact assessment-methodology with special emphasis on european pork production. j. environmental manag. 107, 102-109. 24. roger, a. (2010). another positive year for malaysia’s broiler producer. https://www.wattagnet.com/articles/7240-another-positive-year-for-malaysia-s-broiler-producers (accessed on 2 december 2017). 25. roy, p., nci, d., orikasa, t., xu, q., okadome, h., nakamura, n., shiina, t. (2009). a review of life cycle assessment (lca) on some food product. j. food eng. 90:1-10. 26. sabine, cl., feely, ra., gruber, n., key, rm., lee, k., bulliester, jl. (2004). the oceanic sink for anthropogenic co2. science 305:367-71. 27. seguin, f., hayo, vdw., isabelle, b., eve, p. (2011). environmental analysis of organic broiler production in france and improvement options. 28. sonko, sp. (2018). express assessment of environmental impact of agriculture technologies on the soils of cherkasy oblast. ukrainian journal of ecology, 8(1); 451-459. 29. syauqi, m., zaffrie, m., hasnul, hi. (2015). broiler industry in malaysia. economic science headquarters mardi. 1-5. 30. talayeh, k., ali, r., asadollah, a., m, sharifi. (2016). environmental impact assessment of chicken meat production using life cycle assessment. journal information processing in agriculture 3(4):262-271. http://doi.org/10.106/j.inpa.2016.10.002. 31. walter, k., birgit, g. (2014). life cycle assessment (lca): a guide to best practice. wiley-vch. 32. weidema, bp., bauer, c., hischier, r., mutel, c., nemecek, t., reinhard, j., vadenho, co., wernet, g. (2013). overview and methodology. data quality guideline for the ecoinvent database version 3. ecoinvent report 1(v3). the ecoinvent centre, st. gallen. 33. wiedemann, s., mcgahan, e., poad, g. (2012). using life cycle assessment to quantify the environmental impact of chicken meat production. https://www.wattagnet.com/articles/7240-another-positive-year-for-malaysia-s-broiler-producers http://doi.org/10.106/j.inpa.2016.10.002 international journal of engineering materials and manufacture (2021) 6(4) 332-339 https://doi.org/10.26776/ijemm.06.04.2021.10 ogedengbe t. s. 1 , abdulkareem s. 2 , ogunware o. p. 1 1 department of mechanical engineering elizade university, ondo state, nigeria 2 department of mechanical engineering university of ilorin, kwara state, nigeria e-mail: temitayo.ogedengbe@elizadeuniversity.edu.ng references: ogedengbe et al. (2021). experimental investigation on the effects of various quenchants on hardened high carbon steels during lathe machining. international journal of engineering materials and manufacture, 6(4), 332-339. experimental investigation on the effects of various quenchants on hardened high carbon steels during lathe machining ogedengbe temitayo samson, abdulkareem sulaiman and ogunware olanrewaju peter received:25 february 2021 accepted:23 april 2021 published:01 october 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract the choice of quenchants during heat treatment of carbon steels can influence the properties of the steel sample. a knowledge of the effect of various quenchants on steel can therefore not be over emphasized. this paper presents results from the experimental investigation on the effects of using brine, water and palm-oil as quenchants during hardening of high carbon steels. three samples of aisi 1090 high carbon steel (0.95%wt, carbon) were furnaceheated at a temperature of 900 o c in a crucible furnace and quenched using brine, water and oil to harden the steel samples. the hardened steel was machined using a pre-developed design of experiment (doe). process parameters during machining were speed (50-150 rpm), feed rate (0.3-0.9 mm/min), depth of cut (0.1-0.3mm) and quenchant (water, brine and palm-oil). the responses analysed were surface roughness and tool wear rate. results show that palm-oil with a lowest surface roughness and hardness (0.09μm and 150hb, respectively) and highest material removal rate (0.5124mm 3 /sec) was a preferred quenchant as it reduced surface roughness and increased material removal rate (mrr). hence, palm oil has proven to be a preferred quenchant during heat treatment of aisi 1090 steel for improved machinability and surface finish. keywords: quenchants, hardening, material removal rate, surface roughness, high carbon steel. 1 introduction high carbon steels have found applications in different industries, such as automobile in the manufacture of vehicle spare parts [1]. this is because they are ready available at affordable price and they possess endearing quality which has attracted the interest of machinists and engineers [2]. however, the difficulty encounter in machining steels could result in an increase in costs and reduction in material performance. these had resulted in the exploration of varying methods of increasing the machinability of high carbon steels for engineering applications [3], [4]. some of such methods include the comparative study of material composition, heat treatment and investigation of thermodynamic properties of cutting fluid types on machinability [2], [4], [5].as reported by [6] and [7], constituent elements and properties of metals could be refined by heat treating, thereby improving machinability of such metals. this submission agrees with [8] who reported that heat treatment can be used to improve hardness, strength, ductility and toughness of materials. ogedengbe et al. had earlier investigated the influence of heat treatment on some mechanical properties of steels and they suggested the process especially for hot forming of steels [9]. however, the quenching media could affect hardenability of steels [9], [10].in this work, an investigation was carried out on the effects of various quenchants on hardened high carbon steel during machining. 2 materials and methods 2.1 workpiece material, machines and tools the workpiece material employed for this research was an aisi 1090 high carbon steel bar (0.95% wt., carbon) of length 120mm and diameter 35mm sourced from the steel market in akure, ondo state, nigeria (figure 1). the machine used for the turning was an ajax model computer numerical control lathe machine (figure 2). the cutting tool utilized for the turning operation was physical vapour deposition (pvd) coated tungsten carbide inserts. the high carbon steel samples were divided into 3 equal parts of 40mm length each. the hardening of the steel samples experimental investigation on the effects of various quenchants on hardened high carbon steels during lathe machining 333 was done using a brother electric muffle furnace with model number xd-1200n with a maximum temperature capacity of 1100 o c (figure 3). 2.2 sample preparation the samples were prepared by dividing the parent workpiece material (120 mm by 45 mm) into 3 equal pieces (40 mm by 45 mm). each sample was thereafter chamfered to remove sharp edges. the pre-experimental compositional analysis of the steel sample used for this study is presented in table 1. 2.3 heat treatment/quenching during heat treatment, samples were furnace heated to a temperature of 900 o c and soaked for a period of 60 minutes. each of the three soaked samples were thereafter quenched in brine, pure water and palm oil respectively. 2.4 design of experiment the central composite design (ccd) of response surface methodology (rsm) from minitab software version 18.0 was employed for the design of this experiment. three factors (cutting speed, depth of cut and feed rate) were used as shown in table 2 together with their levels. the software was further used to generate an orthogonal array to guide the machining process (table 3). figure 1: aisi 1090 high carbon steel used for study figure 2: cnc machine used for study figure 3: electric furnace used for study table 1: compositional analysis of aisi 1090 element fe c mn s p cu ni sb si % 98.2 0.95 0.65 0.02 0.01 0.02 0.016 0.084 0.05 table 2: machining factors and levels for quenched steels level cutting speed (m/min) feed rate (mm/rev) depth of cut (mm) 1 50 0.3 0.1 2 100 0.6 0.2 3 150 0.9 0.3 ogedengbe et al. (2021): international journal of engineering materials and manufacture, 6(4), 332-339 334 table 3: orthogonal array for experimentation run factors cutting speed (m/min) feed rate (mm/rev) depth of cut (mm) 1 50 0.9 0.1 2 150 0.3 0.1 3 100 0.6 0.03 4 50 0.3 0.3 5 100 0.6 0.2 6 100 0.6 0.2 7 100 1.1 0.2 8 100 0.1 0.2 9 100 0.6 0.4 10 100 0.6 0.2 11 100 0.6 0.2 12 150 0.9 0.1 13 100 0.6 0.2 14 184 0.9 0.2 15 16 0.6 0.2 16 50 0.3 0.1 17 150 0.9 0.3 18 50 0.9 0.3 19 150 0.3 0.3 20 100 0.6 0.2 figure 4: cycle observed during machining of aisi 1090 2.5 experimental procedure and tests 2.5.1 experimental procedure the prepared steel samples were hardened by heating them in a furnace and quenched using brine, pure water and palm-oil. the hardened steel samples were thereafter mounted on a three-jaw-chuck lathe machine for the turning process (figure 2). the machining cycle is as illustrated in the figure 4. twenty (20) machining runs were carried out altogether and were guided by the orthogonal array developed. each run was repeated 3 times and the average data was reported. each machining session was timed using a stopwatch and cutting time was fixed for 5 minutes. surface roughness and material removal rate were measured and recorded using a profilometer and weighing balance, respectively. experimental investigation on the effects of various quenchants on hardened high carbon steels during lathe machining 335 figure 5: sample on a rockwell hardness tester 2.5.2 tests a. hardness test the hardness value of the steel samples was determined using a rockwell hardness testing machine resident in the department of civil engineering laboratory, elizade university (figure 5). the experiment was carried out at three intervals (before hardening, before machining and after machining) to allow for robust analysis. the sample surfaces were polished prior to test. the indenters were tungsten carbide hard metal balls with load 15 and 100 kgf, respectively. the procedure used by [8] was adopted for the hardness test. b. surface roughness test the surface roughness values were measured using a profilometer. the surface of the specimen was cleaned before measurements were taken to reduce error. the surface measurement for each machining run was taken three times and the average value was reported to also reduce the incidence of error. c. material removal rate determination material removal rate was calculated using equation (1.0) [7]. the weight of the samples was measured before machining and after machining. the difference in weight was calculated and divided by machining time to determine the average material removal rate. 𝑴𝑹𝑹 = 𝐰𝟏−𝐰𝟐 𝐭 (1.0) where, mrr = material removal rate w2 = final weight w1 = initial weight t = machining time 3 results and discussion 3.1 hardness test the hardness test result is as shown in table 4. the hardness values for heat-treated samples were generally higher when compared with non-heat-treated samples. the highest hardness value of 250 hrb was recorded for steel bar sample quenched with pure water. this represents a sharp increase in hardness value when compared with same steel sample quenched in air (control) with a hardness value of 185 hrb. steel samples quenched with brine and palm-oil were found to have hardness values of 210 hrb and 150 hrb, respectively. this results opines that pure water is a better quenchant for high carbon steels when hardness is required during heat treatment. this was in agreement with [8], [11] and [12] who all reported highest hardness when steel samples were quenched with water as compared with other quenchants. this result also agrees with [13] who reported water as a better quenching media when heat-treating carbon steels for an increase in hardness value. palmoil had the lowest hardness value which is less ideal as a quenchant for hcs when hardness is an interest. ogedengbe et al. (2021): international journal of engineering materials and manufacture, 6(4), 332-339 336 table 4: hardness of the quenched samples quenchant pure water palm-oil brine air hardness value (hrb) 250 150 210 185 figure 6: surface roughness for various quenching media 3.2 surface roughness test the surface roughness result is presented in figure 6. the highest surface roughness values were recorded for pure water which is understandable due to the higher hardness value results obtained from the hardness test, post machining minimum and maximum values of 0.401.1 and 2.31μm were recorded for the steel sample quenched with pure water as compared with steel samples quenched with palm-oil and brine that recorded lower surfaces roughness values of 0.09, 0.07 & 0.12 μm and 0.20, 0.49 & 0.60 μm for minimum, medium and maximum values respectively. from the analyses of the results, it was observed that there was no significant change in the surface roughness values for palm-oil quenched steel, though; a very sharp increase in surface roughness of pure water quenched steel was noticed. this increment is attributed to the increase in hardness of the quenched steel. this depict pure water as a poor quenching media when a better surface finish is desired. however, palm-oil was observed to perform better than brine and water with a moderate surface roughness value (min) of 0.09 μm as against 0.2μm and 0.4μm for brine and pure water, respectively. this result therefore positioned palm oil as a better quenchant especially where reduced surface roughness is of a higher priority. the higher surface roughness values recorded for water can also be explained as resulting from the higher thermal conductivity of water (0.669w/mk) as compared to palm oil (0.167w/mk) and brine (0.321 w/mk) having lower heat conductivities. hence, with higher thermal conductivity, water cooled the steel sample more rapidly resulting in a quick and vast formation of martensite which made the steel harder as compared to samples cooled by oil and brine with lower conductivities and slow cooling effect. this result agrees with [17] who reported that quenching heated steel with water resulted in increased hardness of the steel due to an increase in the martensite phase and [11] who reported palm-oil as a better quenching media when hardness value of carbon steels is to be reduced. this reduction in the ultimately results in a better surface finish as seen in figure 4. 3.3material removal rate analysis the result of material removal rate (mrr) is presented in figure 7. generally, samples quenched in palm-oil was observed to return higher values of mrr with a maximum of 0.5124 mm 3 /sec as against samples quenched in brine and pure water having highest mrr values of 0.2514 mm 3 /sec and 0.1162 mm 3 /sec, respectively. results show that high values of mrr were recorded with high cutting speeds and feed rate. this result agrees with [2], [7] and [14] who all recorded increase in mrr with an increase in cutting speed and feed rate. higher values of mrr observed during machining of steel samples quenched with palm-oil can be attributed to the lower strength possessed by this sample compared to other steel samples quenched with brine and pure water. hence machinability of steel sample was improved by quenching in palm-oil. interestingly, these highest mrr values for all the three quenching media was recorded at run 14 which had highest values machining parameters (cutting speed v = 184 m/min, feed rate f = 0.9 mm/rev). this further buttresses the point that higher values of cutting speed and feed rates results in higher 0 0.5 1 1.5 2 2.5 minimum sr medium sr maximum sr s u rf a ce r o u g h n e ss ( μ m ) pure water palm oil brine experimental investigation on the effects of various quenchants on hardened high carbon steels during lathe machining 337 values of material removal rates. an increase in mrr could subsequently reduce the energy consumed during machine as reported by [15]. an analysis of the effect of experimental factors on the surface roughness and material removal rate was carried out using signal to noise ratio. smaller-is-better and larger-is-better were chosen as design constraints for surface roughness and mrr respectively because a smaller surface roughness and larger mrr are indices for a better machining performance. results (figure 8) show that cutting speed and feed rate were the most significant factors influencing the material removal rate for all three steel samples quenched in various media. the effect of depth of cut was insignificant compared with other factors since it ranked lowest as seen in table5.this result agrees with [16] who reported that cutting speed was the most influencing factor affecting surface roughness during machining. figure 7: material removal rate results for water quenching media table 5: signal-to-noise ratio response for surface roughness and mrr for sample quenched with brine factors levels surface roughness 1 2 3 delta rank cutting speed -25.32 25.46 -23.52 1.94 2 feed rate -26.07 23.52 -23.48 2.59 1 depth of cut -24.16 -25.39 -23.80 1.59 3 material removal rate cutting speed 0.2829 0.2894 0.3550 0.0721 1 feed rate 0.3529 0.3202 0.0528 0.0528 2 depth of cut 0.3414 0.2887 0.3174 0.0527 3 0 0.05 0.1 0.15 1 3 5 7 9 11 13 15 17 19 m r r ( m m 3 /s ) run # ogedengbe et al. (2021): international journal of engineering materials and manufacture, 6(4), 332-339 338 (a) (b) figure 8: main effect of factors on mrr for various quenching media (a) pure water (b) palm-oil 4 conclusions in summary, this work covered an experimental investigation on the effect of various using pure water, brine and palm-oil as quenchants during machining of heat treated high carbon steels. the effects on surface roughness, material removal rate and hardness values have been analysed. the experimental results obtained guided the following conclusions reached (i) aisi 1090 quenched in pure water resulted in highest hardness value of 250 hrb, sample quenched in brine produced a moderate hardness value of 210 hrb. however, when quenched with palm-oil, hardness value dropped to 150 hrb, slightly lower than the air cooled (control) sample of 185 hrb (ii) aisi 1090 sample quenched with pure water had higher maximum surface roughness (2.31 μm) than samples quenched with brine (0.60 μm) and palm oil (0.12 μm). (iii) mrr was larger during machining of sample quenched with palm oil (mrrhighest = 0.5124 mm3/sec), moderate during machining sample quenched with brine (mrrhighest = 0.2514 mm 3 /sec) and lowest during machining sample quenched with pure water (mrrhighest = 0.1162 mm 3 /sec). 5 recommendations based on the conclusions reached from the study, the following recommendations are hereby made: (i) pure water is preferred as quenchant only when there is a need to increase hardness value of aisi 1090; (ii) palm-oil is the preferred quenchant during heat treatment of aisi 1090 to obtain the best surface finish during machining; and (iii) palm-oil is a preferred quenchant during heat treatment of aisi 1090 if the aim is to improve machinability via an increase in mrr. acknowledgement authors will like to appreciate the technologists in central workshops of elizade university and university of ilorin for their support all through this study. references 1. abdulkareem, s., busari, r. a., fashola, l. a and madu, i. a. (2020). characteristics of notched high strength materials under tension, torsion and impact loading. international journal of engineering materials and manufacture, 5(3), 68-75. 2. zheng, h.y. and liu, k. (2013), machinability of engineering materials, handbook of manufacturing engineering and technology doi 10.1007/978-1-4471-4976-7_2-1 3. abdulkareem, s., babatunde, m. a., ogedengbe, t.s. and adegun, i.k. (2020), effect of some thermodynamic properties of cutting fluids on machinability of carbon steel, fuoye journal of engineering and technology, 5(2), 2579-0617 4. abdulkareem, s., ogedengbe, t. s., aweda, j.o., ajiboye, t. k., khan, a. a., babatunde, m. a. (2019), investigation on effect of material compositions on machinability of carbon steels, journal of physics: conference series, 1378, 022046 iop publishingdoi:10.1088/1742-6596/1378/2/022046 5. ogedengbe, t.s., yezeed, o. a., yussouff, a.a. (2019), effect of annealing on machinability of grey cast iron, journal of engineering and technology, 10(1) experimental investigation on the effects of various quenchants on hardened high carbon steels during lathe machining 339 6. isamotu, o.f., jacob, v.o., oriaifo, m.a., raji, k.m., egu, i.a., aluko, j.b. (2020), comparative analysis of red oil and palm kernel oil quenching media for low carbon steel, international journal of engineering applied sciences and technology, 4(12), 67-76 7. verdeja, l.f., verdeja, j.i., & gonzález, r. (2009), machinability improvement through heat treatment in 8620 low-carbon alloyed steel, machining science and technology, doi: 10.1080/10910340903451480. 8. lu, y., sisson, r.d., rong, y.k. (2015), critical heat transfer coefficient test for gas quench steel hardenability, proceedings of the 28th asm heat treating society conference october 20–22, detroit, michigan, usa, 490494. 9. ogedengbe, t.s., abdulkareem, s., aweda, j.o. (2018), effect of coolant temperature on machining characteristics of high carbon steel, covenant journal of engineering technology 1(1), 73-86. 10. hande, g., ertan, r., özcan, r. (2012), influence of heat treatment parameters on the microstructure and mechanical properties of boron-alloyed steels, materials testing, 54(9), 1-9. 11. onyenanu, i.u., ignatius, ekengwu, i.e., mobic, i.m. (2015), investigation of the microstructure and mechanical properties of quenched heat affected zones of mild steel weldments, 7(5), 143-151. 12. ndaliman m.b. (2006), an assessment of mechanical properties of medium carbon steel under different quenching media, assumption university journals. 10(2), 100-104. 13. grinshin, s.a, and churyukin, y.n. (2016) evaluation of the cooling capacity of quenching media based on water. metal sci. heat treat. 28(10), 744-745. 14. shah, a.h.a., azmi, a.i., khalil, a.n.m. (2016). grey relational analyses for multi-objective optimization of turning s45c carbon steel, iop conf. series: materials science and engineering 114 012023 doi:10.10088/1757899x/114/1/012023. 15. ogedengbe t.s. (2019), sustainable machining processes through optimization of process parameters, international journal of engineering materials and manufacturing, 4(1), 22-26, doi: 10.26776/ijemm.04.01.2019.03 16. giovanna r., sergio r. &luigino f. (2019), roller burnishing of ti6al4v under different cooling/lubrication conditions and tool design: effects on surface integrity, the international journal of advanced manufacturing technology, 106(2), 431-440, https://doi.org/10.1007/s00170-019-04631-z. 17. khansaa d.s. and basaam a.a. (2018), effect of quenching media on mechanical properties of medium carbon steel 1030, journal of university of babylon, engineering sciences, 26(2), 214-222. international journal of engineering materials and manufacture (2016) 1(1) 21-26 https://doi.org/10.26776/ijemm.01.01.2016.05 a. a. adebisi 1 , m. a. maleque 1 and m. b. ndaliman 2,3 1 department of manufacturing and materials engineering, international islamic university malaysia. 2 scientific equipment development institute (sedi), minna, niger state nigeria. 3 department of mechanical engineering, federal university of technology minna, niger state nigeria. e-mail: debisi1@yahoo.com reference: adebisi, a. a., maleque, m. a. and ndaliman, m. b. (2016). influence of stirring speed on microstructure and wear morphology of sicp-6061al composite. international journal of engineering materials and manufacture, 1(1), 21-26. influence of stirring speed on microstructure and wear morphology of sicp-6061al composite adetayo abdulmumin adebisi, md abdul maleque, and mohammed baba ndaliman received: 15 september 2016 accepted: 26 september 2016 published: 01 october 2016 publisher: deer hill publications © 2016 the author(s) creative commons: cc by 4.0 abstract the aim of this study is to investigate the influence of stirring speed on stir casting synthesis of 15 wt% silicon carbide particle reinforced aluminium alloy (sicp-6061 al) composite. the composite samples were produced at different stirring speed of 300, 500 and 700 rpm. however, the processing temperature and time are maintained at 800 °c and 180 secs processing condition. dry reciprocating wear test is conducted using a ball on disc wear tester at a constant operating condition of 50n load, 10hz frequency for 30 mins on the samples. the influence of stirring speed on the microstructure and wear morphology is examined using scanning electron microscope (sem). the result reveals that the stirring speed influenced the processing condition including the microstructure and wear topography. composite processed at 500 rpm attained homogeneity of the sicp phase as observed from the microstructure. the worn surface experiences a relatively smooth mild wear without formation of cracks, porosity and craters. however, at 300 rpm the composite experiences micro cracks with formation of abrasive grooves due to insufficient distribution of the sicp phase. moreover, at 700 rpm high speed vortex formation is observed due to vigorous stirring which entraps gases and develops into large porosity, cracks and deep craters. this study establishes that stirring speed has a significant effect on the processing condition as well as the wear morphology of sicp-al6061 composite developed using stir casting technique. keywords: stir casting, stirring speed, wear morphology, sicp-6061al composite, microstructure 1 introduction silicon carbide particles reinforced aluminium alloy (sicp-6061al) composite is the most commonly used metal matrix composite due to its strength and stiffness, improved wear resistance and cost effective process technique [1]. these features makes them to emerge as an important category of materials that have potentials for structural applications in the automotive and aerospace industry. the processing of this attractive material plays a major role in determining the performance properties under operational condition [2, 3]. among the variety of processing technique, the stir casting is generally accepted and commercially viable in developing the aluminium silicon carbide composite [4]. moreover, the properties of sicp-6061al composites produced by stir casting depend on process parameters such as stirring speed. for instance, the homogenous distribution of reinforcement particulate is mostly dependent on the stirring speed of the composite melt. uniform distribution is desired in order to maximize the composite properties. in achieving these properties, the stirring speed is of utmost concern. several casting defects are obviously related to the extent and method in which the stirring occurred. studies [2, 4] have shown that porosity formation is attributed to gas entrapment during vigorous stirring leading to air bubbles in the slurry either independently or as air envelopes the reinforced particles. very high stirring speed forms a vortex on the composite melt surface. the vortex mechanism is necessary in enveloping the particles into the matrix melt as the pressure difference between the inner and the outer surface of the melt sucks the particles into the melt [5]. however, vortex formation also traps inclusions which in turn develop into porosity formation. therefore, the vortex process system needs to be properly controlled with the appropriate stirring speed. naher et al., [6] studied the effect of different stirring speed on homogenous distribution of particle in fluids by simulation analysis. experiments were examined on fluids with the same properties of liquid and semisolid aluminium condition. the use of fluid with viscosity similar to reinforced sicp aluminium composite was used in the simulation of the mixtures with various stirring speed. it is concluded from the study that stirring speed has a significant effect influence of stirring speed on microstructure and wear morphology of sicp-6061al composite 22 on particle distribution. moreover, prabu et al., [7] also investigated the effects of stirring speed on uniform distribution of sicp in al alloy matrix. this investigation considered the effect on the hardness value and microstructure. it was revealed that at higher stirring speed the porosity is observed to be more pronounced in the microstructure due to the vigorous stirring which enables oxide skins, gases and contaminations entrapped in the melt. also, the hardness test indicates regions of both high and low value at lower stirring speed due to particle accumulation in some places and the non-inclusion of sicp in other places. similarly, higher stirring speed shows a non-uniform hardness value. this non uniformity is generated due to porosity, oxide skins, and formation of gases. therefore, an optimum stirring speed is required in order to achieve uniform distribution in the matrix to attain uniform hardness. based on the studies highlighted, the stirring speed is recognised as an important process parameter for processing aluminium composite. though, there is no information available in the literature on the effect of this parameter on wear performance. therefore, this study aims to investigate the influence of stirring speed on wear morphology of sicp-al composite using the stir casting process. 2 methodology 2.1 material preparation aa6061 aluminium alloy is used as the matrix material and silicon carbide particles (sicp) as the reinforcement phase material with an average size of 40 μm. table 1 shows the properties of the matrix and reinforcement materials. table 1. properties of matrix (aa6061) and reinforcing (sicp) phase. property unit al (6061) sicp density g/cm 3 2.7 3.22 melting point °c 660 2973 coefficient of thermal expansion µm/m°c 23.4 4 thermal conductivity w/mk 166 126 young’s modulus gpa 70 410 2.2 composite processing procedure the composite was developed using an electric resistance induction stir casting set up incorporated with a preheating furnace, vacuum chamber, stainless steel stirrer and attached die cavity. the melting furnace for al alloy matrix has a heating capacity of 1000 °c while the reinforcement (sicp) heating can be heated to 1200 °c. the temperature value is determined with a ktype thermocouple for sensing the temperature during the melting process until the desired temperature is attained on the indicator. the sicp powder is preheated to 1100 °c for 2 hrs in order to initiate surface oxidation before incorporating into the aluminium melt [8]. after melting of the aluminium alloy, dross formation is extracted from the melt surface with a coated skimmer which has been preheated. moreover, before the addition of sicp, 1 wt% magnesium was incorporated in the aluminium melt to improve the wettability between the matrix and reinforcement phase. subsequently, the injection of sicp was slowly added to the aluminium melt within an average of one (1) min as the stirrer (stainless steel) is gradually lowered into the furnace in order to perform stirring and pouring. the die steel is heated to 500 °c for 1 hr and then positioned in a vacuum chamber of 350mmhg before pouring take place. throughout this process, the composite melt is monitored to be in a molten state. 2.3 wear testing dry reciprocating wear test is conducted using a ball on disc high frequency reciprocating rig (hfrr) tester (as shown in figure 1) according to astm d 6079-97/en 590. the wear test is conducted at a constant operating condition of 50 n load, 10 hz frequency for 30 mins. each of the composite produced at different stirring speed was tested against a 52100 chrome steel material with ø6mm and 60-67 hrc hardness value. all the cast sample were cleaned with acetone prior and after testing and weighed using a micro scale weighing balance with an accuracy of 0.0001g. the wear rate is determined using the weight loss method as described in equation (1): r m w t   δm = mass loss, ρ = density, t = time (1) adebisi et al., (2016): international journal of engineering materials and manufacture, 1(1), 21-26 23 figure 1: schematic view of wear testing machine. 3 results and discussion 3.1 microstructure figure 2(a) shows the scanning electron microscope (sem) of al6061 alloy and the presence of magnesium and silicon in the al alloy is confirmed from the energy dispersive x-ray spectroscopy (eds) analysis as shown in figure 2(b). the morphology of the sicp powder is shown in figure 3(a) with the eds analysis in figure 3(b). the average size of the sicp is 40 μm. figure 2: (a) scanning electron micrograph (b) energy dispersive x-ray spectroscopy of 6061al alloy. figure 3: (a) scanning electron micrograph (b) energy dispersive x-ray spectroscopy of sicp. a a b b influence of stirring speed on microstructure and wear morphology of sicp-6061al composite 24 3.2 effect of stirring speed on the microstructure of sicp-al composite homogenous distribution of the sicp is desirable in order to optimize the properties of sicp-al composite. to achieve this, the processing condition of the stir casting technique is of utmost importance. therefore, it is essential to examine the influence of stirring speed, a crucial parameter in stir casting, on the distribution of sicp in al alloy matrix. samples from the cast composite processed at 300, 500 and 700 rpm were analysed through microstructure analysis. from the microstructural characterization it is observed that stirring speed significantly influenced the distribution of sicp which is evident in figure 4b. at 300 rpm, it is observed from the micrograph that regions of clustering and micro porosity is detected. moreover, the distribution of sicp is not uniformly dispersed as viewed in figure 4(a). this indicates that 300 rpm is insufficient to achieve homogenous distribution of sicp in the al alloy matrix. with higher stirring speed of 500 rpm, an improved distribution of the sicp is achieved as shown in figure 4(b) indicating the sicp is uniformly dispersed in the matrix alloy. moreover, vortex formation is found to be minimized at 500 rpm stirring speed thereby stabilizing centrifugation which may lead to minimal stirring efficiency and potentially severe air entrainment at higher stirring condition. at higher stirring speed of 700 rpm, the porosity in the microstructure is more pronounced as observed from the micrograph in figure 4(c). this condition is attributed to the vigorous vortex formation due to high stirring speed which enables oxide skins, gases and contaminants to be entrained in the melt. furthermore, the distribution of the sicp is not effective enough due to the formation of undesirable conditions such as large porosity and gas entrapment. 3.3 effect of stirring speed on wear morphology of sicp-al composite dry reciprocating wear test is conducted on the sicp-al composite processed at different stirring speed of 300, 500 and 700 rpm. the surface wear morphology of these composites were evaluated based on the wear test condition of 50n load, 10 hz frequency for 30 mins. figure 5 shows the wear morphology of sicp-al composites considering the influence of stirring speed condition. figure 5(a) examines the composite processed at 300 rpm. it is observed that the surface topography is characterized by both abrasive and adhesive wear mechanism as indicated with regions of groove formation and regions of particle clustering compaction respectively. moreover, due to the insufficient distribution of the reinforced sicp, the surface is characterised with micro cracks and regions of densely packed sicp. as such abrasive grooves are observed in areas where the sicp is absent which eventually formed abrasive grooves as shown in 5(a). figure 4: microstructure of 15 wt% sicp al composite processed at (a) 300 rpm (b) 500 rpm and (c) 700 rpm. the formation of composites, porosity, and micro cracks are indicated. clustered sicp porosity micro cracks sicp sicp sicp sicp clustered sicp porosity cracks a b c adebisi et al., (2016): international journal of engineering materials and manufacture, 1(1), 21-26 25 figure 5: wear morphology of 15 wt% sicp al composite processed at (a) 300 rpm (b) 500 rpm and (c) 700 rpm. the formation of craters, cracks, and abrasive grooves are indicated. however, composite processed at 500 rpm shows that the topography of the worn surface is characterised with a relatively smooth mild wear without formation of cracks and porosity as shown in figure 5(b). this is attributed to the uniform distribution of the sicp attained with 500 rpm stirring speed and also the sufficient wettability between the reinforcement and al alloy. this provides adequate rubbing and stable contact between the composite and the counter surface during the wear test. the stable interaction results to the formation of oxide layer on the wear surface which is viewed as the whitish scale profile on the sem micrograph. this layer serves as a protective surface which improves the abrasion and adhesion resistance of the composite. figure 5(c) describes the wear topography of composite processed at 700 rpm, the surface is characterized with numerous deep craters with crack formation due to the vigorous stirring speed used in the processing. this condition is ascribed to the high speed vortex formation which entraps inclusions such as gases which in turn develops into large porosity formation. 6 conclusions the influence of stirring speed on the microstructural and wear morphology of 15 wt% sicp-al composite was studied. it was found that the stirring speed has significant influence on the properties of composite. the following conclusions were drawn from the experimental results: 1. the sicp-al composite was successfully processed and developed using the stir casting technique by varying the stirring speed. 2. the composite achieved uniform particle distribution with 500 rpm stirring speed which in turn translates to improved microstructural and wear properties. 3. from the microstructural analysis, it is found that at 300 rpm stirring speed, the composite experiences micro cracks with formation of abrasive grooves due to insufficient distribution of the sicp phase. moreover, at 700 rpm high speed vortex formation is observed due to vigorous stirring which entraps gases and develops into large porosity, cracks and deep craters. 4. the wear morphology of the composite processed at 500 rpm shows that the topography of the worn surface is characterised with a relatively smooth mild wear without formation of cracks and porosity. this feature is attributed to the uniform distribution of the sicp in the matrix and also the sufficient wettability achieved between the reinforcement and al alloy. s l i d i n g d i r e c t i o n abrasive grooves densely packed sicp crack formation crack formation deep craters a b c influence of stirring speed on microstructure and wear morphology of sicp-6061al composite 26 5. the surface topography of the composite processed at 300 and 700 rpm is characterized with the formation of abrasive grooves, micro cracks and development of large porosity (deep craters) with cracks respectively. 6. achieving optimum stirring speed of 500 rpm during the processing of sicp-al composite improves and also maximise the microstructural and wear properties. acknowledgement the authors acknowledge the support of the ministry of education and international islamic university malaysia (iium) for the financial support to conduct this research under research project prgs12-002-0002. the authors also appreciates the foundry workshop and metallographic laboratory at iium where the experimental studies were conducted. references 1. evans, a., san marchi, c., & mortensen, a. (2013). metal matrix composites in industry: an introduction and a survey. new york: springer science & business media. 2. sozhamannan, g., prabu, s. b., & venkatagalapathy, v. (2012). effect of processing parameters on metal matrix composites: stir casting process. journal of surface engineered materials and advanced technology, 2(1), 11-15. 3. adebisi, a. a., maleque, m. a. & shah, q. h. (2014). performance assessment of aluminium composite material for automotive brake rotor. international journal of vehicle systems modelling and testing, 9(3-4), 207-217. 4. bharat, k., & jyoti, v. m. (2016). aluminium-based metal matrix composites by stir casting: a literature review. international journal of materials engineering innovation, 7(1), 1-14. 5. ahmad, s. n., hashim, j. & ghazali, m. i. (2005). the effects of porosity on mechanical properties of cast discontinuous reinforced metal matrix composite. journal of composite materials, 39, 451-466. 6. naher, s., brabazon, d., & looney, l. (2003). simulation of the stir casting process. journal of materials processing technology, 143, 567-571. 7. prabu, s. b., karunamoorthy, l., kathiresan, s., & mohan, b. (2006). influence of stirring speed and stirring time on distribution of particles in cast metal matrix composite. journal of materials processing technology, 171(2), 268-273. 8. adebisi, a. a., maleque, m. a., ali, m. y. & bello, k. a. (2016). effect of variable particle size reinforcement on mechanical and wear properties of 6061al–sicp composite. composite interfaces, 23(6), 533-547. http://www.inderscienceonline.com/author/kumar%2c+bharat http://www.inderscienceonline.com/author/menghani%2c+jyoti+v http://www.inderscienceonline.com/loi/ijmatei international journal of engineering materials and manufacture (2019) 4(2) 41-47 https://doi.org/10.26776/ijemm.04.02.2019.01 s. abdulkareem 1 , t. a. adekaye 1 ., a. t. abdulrahim 1 ., y. l. shuaib-babata 2 ., t. k. ajiboye 3 ., i. i. ahmed 2 ., h. k. ibrahim 1 , j. a. adebisi 2 and t. yahaya 2 1 department of mechanical engineering 2 department of materials & metallurgical engineering faculty of engineering & technology, university of ilorin, p.m.b. 1515, ilorin, nigeria 3 department of mechanical engineering faculty of engineering, university of maiduguri, p.m.b. 1069, maiduguri, nigeria e-mail: ibrahim.kh@unilorin.edu.ng reference: abdulkareem s., adekaye t. a., abdulrahim a. t., shuaib-babata y. l., ajiboye t. k., ahmed i. i., ibrahim h. k., adebisi j. a. and yahaya t. (2019). hardness and tensile properties of prophylactic knee brace produced from cow bone and periwinkle shell composites. international journal of engineering materials and manufacture, 4(2), 41-47. hardness and tensile properties of prophylactic knee brace produced from cow bone and periwinkle shell composites abdulkareem sulaiman, adekaye timothy adeniyi, abdulrahim abdulbaqi toyin, shuaibbabata yusuf lanre, ajiboye tajudeen kolawole, ahmed ismail idowu, ibrahim hassan kobe, adebisi jelil adekunle and yahaya taiwo received: 15 february 2019 accepted: 27 march 2019 published: 20 june 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract application of reinforced aluminium scrap for the production of prophylactic knee brace (pkb) particularly with agrowaste materials is rarely available. in this work, hardness and tensile properties of aluminium alloy (al 6063) straps reinforced with cow bone (cb) and periwinkle shell (ps) for the production of pkb were investigated. the cb and ps sourced were cleaned and the cb was sun-dried for 4 weeks before crushing with denver laboratory ball mill (model: 48-d0500/q). the ps was also crushed, sun-dried for 7 days and treated in the oven (model sdo/225) at 110 o c for 30 minutes to remove moisture. the particle size of 75 µm was used to cast six (6) each of aluminium/cowbone (al/cb) and aluminium/periwinkle shell (al/ps) composites. the cast aluminium composites of pkb and original pkb were investigated for density, hardness, and tensile properties. it was observed that addition of cb and ps in the cast pkb gave a density of 2.68 g/cm 3 and 2.60 g/cm 3 respectively. the average values of hardness and tensile strength obtained were 41.18 bhn and 135.88 mpa respectively when ps was added to the cast aluminium pkb, while addition of cb gave harness values of 40.45 bhn and tensile strength of 134.63 mpa. keywords: turning, coolant temperature, ti6al4v, surface roughness, machining parameter 1 introduction the rate of wastes generation in modern day life has tremendously increased in which its composition and the magnitude generated have influence on the way the population lives [1]. improper management of such wastes may have been accountable for degrading the environmental and the difficulty in its disposal [1, 2]. this work focused on using aluminium alloy (al 6063) straps that is the off-cut generated from the production of aluminium doors and windows. the aluminium alloy off-cut was used as matrix while periwinkle shell (ps) and cowbone (cb) were used as reinforcements to form a composite for the production of prophylactic knee brace (pkb) used in bone support. pkb consists of the brace (metal), hinge (link point) and strap system. pkb is usually used as components for knee injury management (preventive and healing mechanism) of knee injuries [3, 4]. many works on reinforcement of aluminium have been carried out [5-12]. among these, umunakwe et al. [12] reported on mechanical properties and microstructures of particulate periwinkle shell-aluminium 6063 metal matrix composite (pps-almmc) and comparing the properties of the composites with those of the aluminium 6063 (aa6063) alloy. application of aluminium scrap for pkb particularly with ps and cb as reinforcements is rarely available. the focus of this study is to investigate the hardness and tensile properties of prophylactic knee brace produced from cow bone and periwinkle shell composites hardness and tensile properties of prophylactic knee brace produced from cow bone and periwinkle shell composites 42 2 materials and methods the materials used are: the off-cut (scraps) of aluminium (al 6063) (door and window frames) produced by nigeria aluminium extrusions limited, lagos nigeria. the ps and cb were sourced from river bank and abattoir respectively. 2.1 preparation of samples 2.1.1 preparation of aluminium scrap the aluminium scraps were cleaned and sun dried for 24 hours to remove dirt before charged into furnace (model no. m254 and serial no. ad3246p) for melting and de-slagging. the molten aluminium was stirred and cast into a rectangular bar. the solidified material was reduced to smaller sizes. the percentage composition of the aluminium alloy used is shown in (table 1) table 1: chemical composition of aluminium (al 6063) off-cut [12] element al si fe cu mn mg zn cr ti ca other wt % 98.18 0.60 0.46 0.012 0.024 0.35 <0.002 0.01 0.06 0.07 0.12 2.1.2 preparation of periwinkle shell (ps) the ps (figure 1) were cleansed by soaking for 24 hours, boiled in water and detergent at 100 o c for 50 minutes and cooled in air. the washing was carried out by wire brush to remove sand particles and dirt. it was later reduced into smaller sizes and sun dried for 7 days. the ps was heated in an oven (model sdo/225 serial no. y9c227) at 110 0 c for 30 minutes to remove moisture as reported by umunakwe et al., [12]. the chemical composition of ps powder as used by nwabufor [13] (table 2). the ps was crushed with denver laboratory ball mill (model 48-d0500/0 with serial no. 14002201). pulverized and sieved to 75μm particle size using bs standard sieves (figure 2). figure 1: periwinkle shells (ps) figure 2: pulverized periwinkle shell table 2: chemical composition of periwinkle shell powder [13]. constitute sio2 al2o3 fe2o3 cao mgo so3 k2o na2o mn2o3 p2o tio2 composition (%) 32.84 10.20 7.02 40.84 1.47 0.26 0.14 0.24 0.78 0.01 1.07 2.1.3 preparation of cow bone (cb) the cb bones were soaked for 24 hours, scraped to remove meat remnants. the bones were boiled in waterdetergent at 100 o c for 90 minutes in other to remove fat and oil and thereafter cooled in air as equally reported by zainal and hamdzun [14]; sangeeta et al., [15]; abdulrahman et al., [16]. the bones were further scrubbed with wire brush in warm water before size reduction by the use of sledge hammer and sun dried for 4 weeks to reduce the moisture [9, 17]. calcination of the bones were effected in oven (model sdo/225 with serial no. y9c227) at 300 o c for 2 hours to ensure elimination of protein [14, 18]. denver laboratory ball mill (model 48-d0500/0 with serial no. 14002201) was used to crush the bones and pulverized to 75 μm particle size according to bs1377:2014. the chemical composition of cow bone (table 3) was adopted from sergius and janecek [19]. abdulkareem et al. (2019): international journal of engineering materials and manufacture, 4(2), 41-47 43 table 3: chemical composition of cow bone powder (wt%) [19] metal ca mg k p co % composition 36.05 0.74 0.85 16.43 4.58 2.2 casting of prophylactic knee brace (pkb) composites 2.2.1 melting and casting of the brace the production of the pkb aluminium composite was achieved using the stir casting method [12, 20]. the samples were produced by varying the percentage of reinforcing cb and ps particles at (1, 2, 4, 6, 8 and 10) wt % of the same 75 μm particle size. the aluminium alloy of mass 292 g was charged into the furnace, which was heated to 850 ˚c to ensure complete melting of the alloy. 2.2.2 production of pkb composite in the production of pkb composite, the furnace temperature was raised to 850 ˚c and the molten aluminium alloy was allowed to cool in the furnace to a temperature of 700 ˚c [12]. the ps was preheated to 200 ˚c for 1 hour to improve the materials wettability [21]. the preheated ps was added and stirred for 5 minutes. the composite slurry was re-heated to a temperature of 850 ˚c and thoroughly stirred for 5 minutes before the melt was poured into a preheated mould with diameter 250 mm and 300 mm length used to prepare cast braces (figure 3 and 4). the pouring of the melt was maintained at laminar flow to avoid entrapped air. the same procedure was adopted for the casting of cb aluminium composite with addition of 0.5 wt% mg for good wettability of particles with molten metal [21]. figure 3: cast brace composite figure 4: finished cast brace composite hardness and tensile properties of prophylactic knee brace produced from cow bone and periwinkle shell composites 44 3 results and discusssions 3.1 determination of the density the density measurements of the samples were carried out using the archimedes’s principle, which states that a body immersed in a fluid is buoyed up by a force equal to the weight of the displaced fluid. the relative density rd is obtained using equation 1 [20]. 𝑅𝐷 = 𝑊𝑎 𝑊𝑎−𝑊𝑤 (1) where, 𝑅𝐷 = relative density of the composite sample, 𝑊𝑎 = weight of the composite in air, 𝑊𝑤 = weight of the composite in water. the density (figure 5) of the reinforced ps composites reduced from 2.72 g/cm 3 at 1 wt % of ps addition to 2.60 g/cm 3 at 10 wt % of ps addition. the density of the reinforced cb composites also reduced from 2.72 g/cm3 at 1 wt % of cb addition to 2.68 g/cm3 at 10 wt % of cb addition. the reduction in density of the cast pkb was more significant in ps composites compared to that of cb composites. the reduction could be because of less dense property of ps particles as against the cb particles. the decrease in density with addition of the particulates could be because of the lower density of the fillers compared to that of aluminium metal matrix. this is good because it will enhance the utilization of al/ps and al/cb metal composites where lighter weight is desired properties. this is in agreement with the work of [12] and [21]. fig 5 shows the densities of the al/ps and al/cb composites produced with that of control and original material (om) used for pkb. it can be observed that the density of the control and om is 2.73 g/cm 3 and is higher than that of al/ps and al/cb. the density of ps reinforced composite is lower compared to the density of al/cb, control and om. the density of al/ps composite falls within the range of density of aluminium material used for pkb. figure 5: density of the al/ps and al/cb composites vs control sample and om 3.2 hardness property the hardness properties of the samples (figure 6) were determined according to astm e10 standard procedure using brinell hardness tester (edibon brinell tester, model eedb, and serial no. eedb0006/13). the machine indenter of diameter 5mm and load 2500n with dwelling time of 15sec was used. according to [22], the average diameter of indentation was used to determine the hardness number of the composites using equation 2. 𝐻𝐵 = 0.102 × 2𝐹 𝜋𝐷(𝐷−√𝐷2−𝑑2) (2) where, f = test force (n), d=diameter of steel ball (mm), d=diameter of indentation (mm) table 4 shows the hardness values of the produced composites with % wt pws and % wt cb, the hardness values of the cast al/ps composites increased as the % wt ps addition increases in the aluminium alloy while that of al/cb abdulkareem et al. (2019): international journal of engineering materials and manufacture, 4(2), 41-47 45 initially decreased sharply before steady increases before decreasing. the hardness value of composites increased from 40.30 hbn to 41.80 hbn at 10 wt % addition of ps. the presence of the hard ceramic phase in the ductile matrix resulted into the increase in the hardness of the al/ps composite from 40.50 hbn to 41.80 hbn for 1 wt % and 10 wt % ps respectively. the al/cb composites increased in hardness from 40.10 hbn for 1wt % up until 40.80 hbn for 6 % wt cow bone particles where it gradually decreased to 40.40 hbn at 10 wt % of cow bone particles. the decrease in hardness of the cb composite might be due to poor wettability and poor filler dispersion at higher weight fraction and the increments of hardness of al/ps was attributed to increase in weight percentage of hard and brittle phase of the ps particles in the aluminium alloy. the increase in hardness could be due to the effect of the increase in the interfacial contact area between the matrix and the reinforcement. this hardness experience in the ps composites is likely to be from sio2, al2o3, cao and fe2o3 present. figure 6 shows the hardness value recorded for the produced aluminium particulates composites and control as well the om it was observed that al/ps composites possess the average highest hardness values of 41.18 bhn followed by the al/cb composites with 40.45 bhn as compared to control with 40.30 bhn used for pkb. table 4: hardness values of al-wt % ps and cb knee brace produced percentage composition of al/ps and al/cb hardness (bhn) periwinkle shell cowbone 99% 1% 40.50 40.10 98% 2% 40.80 40.30 96% 4% 41.20 40.60 94% 6% 41.30 40.80 92% 8% 41.50 40.50 90% 10% 41.80 40.40 hardness value of control sample = 40.30 hardness value of original material = 40.50 figure 6: hardness values for al/ps and al/cb with control and om 3.3 tensile strength the results of the tensile strength (table 5) revealed that the tensile strength of the aluminium alloy was improved with increasing weight fraction of the reinforcements (ps and cb). this was due to the increase in the percentage of ps and cb particulates, which is likely to result in production of more calcium silicate giving higher strength in the composite produced. al/10 wt % ps samples give more strength (140.30 mpa) while the al/10 wt % cb gives strength value of 138.20 mpa which is lower than that obtained from pws sample, hence ps impacts more strength in aluminium than the cb. this result may be attributed to the strengthening effect of the particulates on the aluminium alloy matrix. this behaviour is in agreement with the work of nwabufor [13], agunsoye et al, [18] and aigbodion, hardness and tensile properties of prophylactic knee brace produced from cow bone and periwinkle shell composites 46 [21]. figure 7 shows the tensile strength of al/ps and al/cb composites produced with control and om. the tensile strength of the control sample is lower compared to that of om. when the addition of ps and cb from 1-10 wt % was made, it was observed that the tensile strength of the aluminium composites increased significantly and had higher values compared to the control and om. table 5: tensile strength of al-wt % ps and cb knee brace produced percentage composition of al/ps and al/cb tensile strength (mpa) periwinkle shell cow bone 99% 1% 131.50 130.90 98% 2% 132.80 131.50 96% 4% 135.70 133.70 94% 6% 136.90 135.90 92% 8% 138.10 137.60 90% 10% 140.30 138.20 tensile strength of control sample = 130.10 mpa tensile strength of om = 135.17 mpa figure 7: tensile strength of al/ps and al/cb with control and om 4 conclusions investigation on hardness and tensile properties of prophylactic knee brace produced from cow bone and periwinkle shell composites, using ps and cb as reinforcements has been reported. the evaluations of the hardness and tensile properties of the cast aluminium brace, has necessitated the following conclusions: 1. aluminium composite of lightweight can be produced using ps and cb because the density of the produced al/ps and al/cb composites reduced with increase in the addition of ps and cb. 2. the tensile strength of 140.30 and 138.20 mpa were obtained for 90 % cast aluminium base metal matrix composite with 10 % weight percent addition of ps and cb particles respectively. the tensile strength of cast aluminium base metal matrix composite increases as weight percent addition of ps and cb particles increases. 3. the hardness of the al/ps composites increased as the % wt ps addition increases in the cast aluminium alloy. further work investigation on the impact and buckling properties on the cast pkb with ps and cb particulates as reinforcements is to be carried out. acknowledgement the authors wish to acknowledge the assistance of mr. mustapha ndagi of the department of mechanical engineering, university of ilorin, nigeria for his guidance. abdulkareem et al. (2019): international journal of engineering materials and manufacture, 4(2), 41-47 47 references 1. de sousa f. d. b and zanchet a. (2018). in the search for sustainable processing in compounds containing recycled natural rubber: the role of the reversion process. recycling 2018, 3, 47; doi:10.3390/recycling3040047. multidiciplinary digital publishing institute, switzerland 2. de sousa, f. d. b. (2017). devulcanization of elastomers and applications. in elastomers; çankaya, n., ed.; intech: rijeka, croatia, chapter 10, pp. 209–230. 3. mortaza, n., abu, o., jamshidi, a., & razjoyah, j. (2013). "influence of functional knee bracing on the isokinetic and functional tests of anterior cruciate ligament deficient patents". plos one, 8 (5). 4. yusran, p., & natinee, l. (2009). "adhesion of pineapple leaf fiber to epoxy matrix: the role of structure treatments". journal of science and technology, 31 (2), 189-194. 5. ankesh, k., kanhaiya, k., & suman, s. a. (2016). "study of physica, mechanical and machinability properties of aluminium metal matrix composite reinforced with coconut shell ash particulates". imperial journal of interdisciplinary research (ijir), 2, 151-157. 6. arun, p., shanmughasundaram, p., suganthi, s., kumar, r., & vijay, a. (2016). "wear behaviour of al-chicken bone ash metal matrix composites". journal of advances in natural and applied sciences, 10 (6), 11-15. 7. oladele, i. o., & isola, b. a. (2016). "development of bone particulate reinforced epoxy composite for biomedical application". journal of biotechnology & bioengineering, 1 (1). 8. das, d., mishra, p. c., & singh, s. a. (2014). properties of ceramicreinforced aluminium matrix composites a review". international journal of mechanical and materials engineering, 1 (12), 1-16. 9. oladele, o. i., daramola, o. o., & adewole, a. t. (2014). "comparative study of the reinforcement efficiency of cow bone and cow bone ash in polyester matrix composites for biomedical applications". bulletin of engineering, tome vii, 27-34. 10. michael, i. o., fidelis, i. a., & ikpi, u. u. (2012). "mechanical properties of hybrid periwinkle and rice husk filled cnsl composite". international journal of nano and material sciences, 1 (2), 74-80. 11. purohit, r., rana, r. s., & verma, c. s. (2012). "fabrication of al sicp composites through powder metallurgy process and testing of properties". international journal of engineering research and applications, 2 (3), 420437. 12. umunakwe, r., olaleye, d. j., oyetunji, a., okoye, o. c., & umunakwe, i. j. (2017). "assessment of some mechanical properties and microstructure of particulate periwinkle shell aluminium 6063 metal matrix composite (pps-almmc) produced by two-step casting". nigerian journal of technology (nijotech) , 36 (2), 421-427. 13. nwabufor, m. n. (2015). "development and characterization of al 3.7% cu 1.4% mg alloy / periwinkle ash (turritella communis) particle composites". ahmadu bello university, the department of metallurgical and materials engineering, zaria. 14. zainal, z., & hamdzun, h. (2014). "characterization of local bone ash for bone china production". journal of technology (sciences and engineering), 66 (1), 25-34. 15. sangeeta, p., jie, h., wei, q., & wei, g. (2015). "synthesis and characterization of mesoporous bone char obtained by pyrolysis of animal bones, for environmental application". journal of environmental chemical engineering, 2368-2377. 16. abdulrahman, a., a., l., daud, z., & ridzuan, m. b. (2016). "preparation and characterization of activated cow bone powder for the adsorption of cadmium from palm oil mill effluent". materials science and engineering, 136, 1-6. 17. oladele, i. o., & adewole, t. a. (2013). "influence of cow bone particle size distribution on the mechanical properties of cow bone reinforced polyester composites". biotechnological research international, 2013, 1-5. 18. agunsoye, j., talabi, s., & awe, o. a. (2013). "mechanical properties and tribological behaviour of recycled polyethylene/cow bone composite". journal of materials science research, 2 (2), 41-50. 19. sergius m. & janecek, e. (1931). studies on the chemical composition of bone ash, j. biol. chem., 93:455-466, http://www.jbc.org/content/93/2/455. 20. alaneme k. and bodunrin, m. (2013). "mechanical behaviour of alumina reinforced aa6063 metal matrix composites developed by two-step casting process". acta technical corviniensis-bulletin of engineering, 6 (3), 105-110. 21. aigbodion, v. s. (2010). in a. v. s., "the development and characterization of al-cu-mg/bagasse ash particulate composites" (pp. 17-70). department of metallugical engineering, zaria. 22. asuke, f., aigbodion, v., abdulwahab, m., fayemi, o., popoola, a. p., & nwoyi, c. i. (2012). "effect of bone particle on the properties and microstructure of polypropylene/bone ash particulate composites". journals of elsevier, 135-141. international journal of engineering materials and manufacture (2018) 3(1) 18-31 https://doi.org/10.26776/ijemm.03.01.2018.03 a. n. m. m. rahman 1 , s. alimuzzaman 1 , r. a. khan 2 , m. e. khan 3 and s. n. hoque 3 1 department of fabric engineering, bangladesh university of textiles, tejgaon, dhaka-1208, bangladesh 2 institute of radiation and polymer technology, bangladesh atomic energy commission, dhaka-1349, bangladesh 3 department of textile engineering, ahsanullah university of science and technology, tejgaon, dhaka-1208, bangladesh e-mail: masudfabric@yahoo.com reference: rahman, a. n. m. m., alimuzzaman, s., khan, r. a., khan, m. e. and hoque, s. n. (2018). fabrication, mechanical characterization and interfacial properties of okra fiber reinforced polypropylene composites. international journal of engineering materials and manufacture, 3(1), 18-31 fabrication, mechanical characterization and interfacial properties of okra fiber reinforced polypropylene composites a. n. m. masudur rahman 1 , shah alimuzzaman 1 , ruhul a. khan 2 , md. ershad khan 3 and sheikh nazmul hoque 3 received: 04 february 2017 accepted: 04 march 2018 published: 30 march 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract in this study, an attempt has been taken to manufacture okra fiber (of) composites with varying the fiber content ranging from 25-65% on total weight of the composites and polypropylene (pp) was preferred as matrix material. to fabricate the composites untreated and mercerized fibers were selected. a systematic study was done to observe the mechanical behaviors of the composites such as tensile, impact and bending properties. it was found that treated (mercerized) fiber composites exhibited improved mechanical properties than that of untreated fiber composites. maximum tensile strength (ts) and bending strength (bs) was examined 38.5 mpa and 72.5 mpa respectively, whereas the highest tensile modulus (tm) and bending modulus (bm) was observed 675 mpa and 5.4 gpa respectively. the optimum impact strength (is) and hardness value was found to be 22.87 kj/m 2 and 97 (shore-a) for mercerized fiber composites containing 45% fiber. the composite samples were exposed to different intensities of γ radiation (2.5 kgy–10.0 kgy) and found significant improvement in the mechanical properties up to 5.0 kgy dose. water absorption, degradation properties due to heat and soil medium of the composites were also performed. the interfacial property was examined by microscopic projector and scanning electron microscope (sem) and found that the interfacial bonding between matrix material and fiber was enhanced due to the treatment of fibers which authenticate the found mechanical characteristics of the composites. keywords: okra fiber, γ radiation, polypropylene, composites, compression molding, mechanical properties, composite degradation. 1 introduction recently, fiber reinforced composites have appealed huge consideration in the arena of engineering applications because of their excellent and unique combination of physical and mechanical properties. the bast fibers such as jute, flax, hemp, ramie, sisal, kenaf are presently using as reinforcement in polymer composite and many efforts have been made by researchers to establish natural biodegradable fiber as substitute of synthetic fiber to use effectively in the composite material. several studies reported that incorporation of lingo-cellulosic fiber improves the physicomechanical properties of polymer matrices in the composite material [1-13]. scientists prefer thermoplastic composites than thermoset because of low production cost and lower processing cycle. synthetic fiber reinforced thermoplastic composites are dominating over natural fiber reinforced composites due to their higher strength, stability and corrosion resistance properties. but synthetic fibers are not decomposable and are causing ecological pollution. due to increasing environmental consciousness, composites made of lingo-cellulosic fibers as reinforcing material are exploring day by day [14-17]. okra fiber (of) is obtained from okra plant. the scientific name of the plant is abelmoschus esculentus which is under the family of malvaceae, abundantly available in bangladesh and also in some other tropical countries in the world. fibers can be extracted from the outward cell layers of the stem [18, 19]. presently the fiber has no economic value as the plant is subjected to combustion [20]. but the mucilage of okra fiber can be applicable for fabrication, mechanical characterization and interfacial properties of okra fiber reinforced polypropylene composites 19 the production of decomposable polymer materials with proper grafting process [21]. the composition of of is hemicellulose (15–20%), α-cellulose (60–70%), pectin (3–5%) and lignin (5–10%). the fiber showed improved tenacity (40.1–60.5 mpa) and moderate elongation at break (3–6%) also [22, 23]. the current study of mechanical and morphological properties of okra fiber confirm that it can be a potential candidate as reinforcing material in the composite field which is comparable to those of other common lignocellulose fibers like jute, hemp, flax, pineapple leaf fiber [18]. natural fibers have several advantages; for example, they have acceptable toughness, cheaper, improved strength, recyclable, biodegradable and cause no skin irritation [24-28]. although several advantages, cellulosic fibers endure the drawback of nonresistance to high temperature and proneness to moisture absorption [29]. the composites prepared with nonpolar thermoplastic matrix and hydrophilic natural fiber result in reduced mechanical properties due to the poor affinity between the plastic material and fiber [30]. the mechanical properties of the composites can be enhanced by modification of natural reinforcing fibers by various physical and chemical methods such as alkali/mercerization, monomer grafting under uv and γ radiation [31]. in this study, polypropylene (pp) was selected as thermoplastic resin because it possesses several outstanding properties like very good surface hardness, higher impact strength, superior abrasion and heat resistance. pp with biodegradable fibers can be a favorable way to produce the combination of synthetic-natural polymer composites [32, 33]. the present study was designed to fabricate partially degradable composites using okra fiber as reinforcement and polypropylene as matrix. untreated and mercerized fibers were used to prepare the composite. so, mechanical properties were compared between two types of composites. the optimum fiber content in composites was evaluated based on mechanical performance showed by the composites. thermal aging, degradation under soil medium and water absorption capability were also observed for the optimized composites to investigate the suitability of the composites for wide-ranging applications. the morphology was evaluated by analysis of sem. 2 methodology 2.1 materials okra plant has been collected from gazipur district (bangladesh). about three months old and around 2.5 m high plants were collected. after collection, the middle portion of the stems was separated and then dipped under water for retting. fiber geometry and mechanical properties of fibers strongly depend on stem age [34]. the stems were degraded sufficiently within 15-20 days to allow the collection of fibers. the degraded stems were washed several times using distilled water and then the fibers were obtained. they were dried in open air and reserved in fresh container afterward [19, 35]. 2.2 surface modification to remove natural impurities (lignin, pectin and wax), the fibers were mercerized using 5% naoh solutions for 45 minutes at 70–80°c. then the treated fibers were dried for one week at room temperature and desiccated at the temperature of 100°c for 10 minutes in a hot air oven to remove the presence of any moisture. the color of the fibers was changed from brown to silvery white after mercerization. the change of surface (figure 2) and diameter of the fibers (figure 15) was measured by using the microscopic projector. (a) (b) figure 1: (a) untreated and (b) mercerized okra fiber rahman, et al. (2018): international journal of engineering materials and manufacture, 3(1), 18-31 20 2.3 composite fabrication at first polypropylene sheets were prepared from granules. the preweighted granules were heated for 5 min at 190°c temperature by placing them in between two steel plates in a compression molding machine. the model of the machine was 3856, carver incorporation, usa. cooling was done another compression molding machine of same model for 5-7 min at room temperature using 5 metric ton pressure. the resultant polypropylene sheets were cut to the desired size (12 cm × 12 cm) for composite manufacturing. okra fibers were cut into the length of 20-25 mm. four layers of fibers were inserted between five sheets of preweighted polypropylene during the fabrication of composite. the fibers were embedded randomly in between polypropylene sheets. by this way, a sandwich is formed which was then employed between two steel plates under a pressure of 5 metric ton for 5 min with keeping the temperature of 190°c (shown in figure 3). the thickness of the resultant composites was kept 2 mm. testing specimens were prepared from the composite sheet by cutting with grinding machine carefully. (a) (b) figure 2: the surface image of (a) untreated of and (b), mercerized of figure 3: fabrication model of composite manufacturing fabrication, mechanical characterization and interfacial properties of okra fiber reinforced polypropylene composites 21 2.4 testing of mechanical properties of the composites tensile strength, tensile modulus, elongation at break (%) was investigated by following the din 53455 standard method using a hounsfield s series universal testing machine, model: h 50 ks-0404. the cross-head speed was set 10 mm/min during testing and the gauge length was 20 mm. the geometry of the test specimen was maintained 60 mm × 15 mm × 2 mm. bending strength and bending modulus were examined according to din 53452 by means of above-mentioned equipment. the test speed and span distance was 10 mm/min and 40 mm respectively. the charpy impact strength was performed by maintaining the standard of din en iso 179 in the un-notched, flat mode by means of a pendulum type impact testing machine (model-3016, germany). the hardness of the composite samples was tested by an hpe durometer (model type 60578, germany) according to din 53505 standard. the mechanical properties of unreinforced polypropylene sheet were also tested according to the abovementioned method. prior to testing all the testing specimens were conditioned at 25°c and 50% r.h for several days. all the mechanical properties of composites were tested under the similar conditions. the average value of five samples was taken as the final value of all tests. 2.5 irradiation the composite samples were exposed to irradiation for different doses (2.5‒10.0 kgy) with a dose rate of 3.3 kgy/hr by using the available γ source of cobalt 60 (90.0 kci) of the baec, savar, dhaka. 2.6 water absorption water absorption ability of composite samples was carried out in deionized water. the experiment was done at room temperature (25ºc) for 90 hr into a glass beaker containing 100 ml water. the size of the specimens was 20 mm × 10 mm × 2 mm. the samples were dried at 105°c in an oven before dipping, then cooling was done in a desiccator and the weight was measured. after different soaking period, the mass of the samples was taken by withdrawing them from the beaker. water absorption was calculated by the following formula: wg%=[(wa– wo)/wo]×100, where wg is the water absorption (%), wo denoted the mass of the specimens before dipping in and wa indicated the mass of the test samples after water treatment. 2.7 thermal degradation test for determination of thermal aging, a thermo stated oven was selected and the test was continued up to the time period of 30 days. model of the instrument was denver, aa-160. after a certain time (5 days), samples were taken out from the oven and reserved at 25ºc for 24 h for testing the tensile properties. 2.8 assessment of soil degradation untreated and mercerized composite test samples were buried in soil at 15 cm depth for the assessment of degradation behavior of the composites in soil medium. the soil should contain at least 25% moisture and the assessment was continued up to 24 weeks. after a certain time, samples were taken out from soil followed by washing with purified water and then dried for 6 hr keeping the temperature of 105°c. the samples were preserved for 24 hr at room temperature for conditioning to observe the tensile behaviors. 2.9 examination of interfacial property sem micrographs were taken from a scanning electron microscope (model js 6490, japan). tensile fracture samples were selected for analysis of sem. the dimension of the specimens was 2 mm × 2 mm and the experiment was done at room temperature using 20kv acceleration voltage. 3 results and discussion 3.1 influence of fiber loading to understand the mechanical attributes of a polymer composite several parameters need to be analyzed. these parameters greatly influence the performance of a composite and those are alignment of fiber, fiber-matrix ratio, fiber-matrix interfacial bonding [36, 37]. the fiber loading was varied in the composites from 25 to 65% on the weight basis of the composites. moreover, compatibility between matrix and fiber play a vital role on tensile behavior of the composites [38]. influence of fiber filling (wt. %) on the mechanical properties of resultant composites was examined and the results are plotted in figure 4-8. it was observed that tensile, impact and bending properties were improved with the filling of the fiber up to 45% in the composite and after that considerable amount of reduction in mechanical properties were found with the rising of fiber loading in the composite (figure 4, 6 and 8). at the level of 45% fiber loading, tensile, bending and impact strength of the virgin samples were examined to be 33.2 mpa, 57.2 mpa and 20.84 kj/m 2 respectively. for treated fiber composites that values were observed to be 38.5 mpa, 72.5 mpa and 22.87 kj/m 2 respectively. it was also testified that tensile and bending modulus of the composites improved with the increment of fiber ratio up to 45% in the composites and above 45% fiber ratio, tensile and bending modulus of the composite declined considerably with the growth of fiber volume (figure 5 and 7) for both type of rahman, et al. (2018): international journal of engineering materials and manufacture, 3(1), 18-31 22 composites. the reason behind such result may be ascribed to the fact that with the increase of fiber volume in the composite the fiber-matrix interface was lessened due to reduced wetting tension [39]. figure 4: comparative tensile strength of the resultant composites with respect to fiber loading. figure 5: comparative tensile modulus of the resultant composites with respect to fiber loading. fabrication, mechanical characterization and interfacial properties of okra fiber reinforced polypropylene composites 23 figure 6: comparative bending strength of the resultant composites with respect to fiber loading. figure 7: comparison between bending modulus of the resultant composites with respect to fiber loading. figure 8: comparative impact strength (charpy) of the resultant composites with respect to fiber loading. rahman, et al. (2018): international journal of engineering materials and manufacture, 3(1), 18-31 24 the tensile and bending modulus of untreated fiber composites having 45% fiber content show the value of 615 mpa and 3.8 gpa respectively. similarly, tm and bm value were found 675 mpa and 5.4 gpa respectively for treated fiber composites (45% fiber). from this analysis, it can be concluded that at the level of 45% fiber loading, the composites achieved the best mechanical characteristics. so, at the configuration of 45% fiber loading was found to be the optimal configuration. the composite performs poor mechanical properties due to reduced population of fibers with minor load transmission capability to each other at the lower level of fiber filling. at this level, the stress gathered at some points and extremely localized strains arise in the binder material. at 45% fiber content, the fibers participate in stress transfer very actively because the optimum alignment was found at this stage. a higher level of fiber loading increased the fiber agglomeration, as a result, cluster can be created and stress transferring should be blocked. so, failure occurs in the composite followed by initiation of cracks. the serviceability of the bio-composite might be failed by introducing the failure of the plastic material at first and breakage of reinforcing fiber afterward [40, 41]. 3.2 investigation of mechanical properties of the composites the tensile properties of a material give the information how it behaves during the application of axial loading. the mechanical properties of unreinforced pp, untreated and treated of/pp (45% fiber by wt.) composites were investigated. the obtained values are given in tables 1-2. analyzed data revealed the value of ts, tm, eb (%), bs, bm, is and hardness was 20.5 mpa, 492 mpa, 375%, 35.5 mpa, 1.9 gpa, 4.55 kj/m 2 and 92 shore-a respectively for pp sheet. investigation showed that both raw and treated fiber composites achieved a substantial enhancement of their mechanical attributes which indicated the successfulness manufacture of the reinforcing fibers with pp matrix. the tensile strength and tensile modulus of virgin fiber composite improved to 62 and 25% respectively than pp matrix. from the analytical data, it was also found that bending strength, bending modulus and impact strength also improved to 61, 105 and 358% respectively for virgin fiber composites over the pp matrix. the treated fiber composite showed 88, 37, 104, 184 and 402% increase of ts, tm, bs, bm and is respectively over the pp matrix. on the other hand, eb% was reduced significantly due to lower elongation of the natural fibers. the value of hardness was found to be 95 and 97 (shore-a) for untreated and treated fiber composite respectively. it can be concluded that untreated fiber composites showed comparatively lower improvement in mechanical properties related to mercerized fiber composites. it was reported that the treated fiber composite gained 16 and 10% increment of ts and tm than the untreated fiber composite. the bs, bm and is of the treated fiber composite is improved 27, 38 and 10% higher than the raw fiber composite. during alkali treatment, the interface between fiber and matrix was improved for subtraction of dirty substances from the fiber and produces high-quality fibers. mercerization also decreases fiber diameter also improves the surface roughness. the surface geography and enhancement in aspect ratio compromises better interfacial bond and developed the ultimate mechanical properties. the increment of surface roughness which creates better mechanical interconnecting between fiber and matrix was found due to mercerization. table 1: comparative tensile and bending properties of unreinforced pp sheet and the optimized composites (45% fiber content) found in this study materials tensile properties bending properties ts (mpa) tm (mpa) eb (%) bs (mpa) bm (gpa) polypropylene 20.5 ± 0.8 492 ± 10 375 ± 9 35.5 ± 1.1 1.9 ± 0.2 untreated of/pp 33.2 ± 0.9 615 ± 8 9.5 ± 0.2 57.2 ± 1.3 3.9 ± 0.3 treated of/pp 38.5 ± 0.7 675 ± 8 8.2 ± 0.3 72.5 ± 1.2 5.4 ± 0.1 table 2: comparative impact strength and hardness of unreinforced pp sheet and the optimized composites (45% fiber content) found in this study materials impact strength (kj/m 2 ) hardness (shore-a) polypropylene 4.55 ± 0.2 92 ± 0.5 untreated of/pp 20.84 ± 0.2 95 ± 0.5 treated of/pp 22.87 ± 0.3 97 ± 0.5 3.3 influence of γ radiation on mechanical characteristics of the composites the impression of γ radiation on tensile, impact and bending properties of the composites was inspected by optimized composites (45% fiber). the obtained data reported that the mechanical properties increasing trend was found from 2.5–5.0 kgy dose and after that the values decrease up to 10.0 kgy dose for both untreated and treated fiber composites. best mechanical properties were obtained using 5.0 kgy of total γ dose at 3.3 kgy/h. fabrication, mechanical characterization and interfacial properties of okra fiber reinforced polypropylene composites 25 maximum value of ts, tm, bs, bm and is of raw fiber composites were examined to be 41.9 mpa, 680 mpa, 70 mpa, 4.8 gpa and 22.9 kj/m 2 respectively and for treated fiber composites the optimum ts, tm, bs, bm and is values were 48.8 mpa, 755 mpa, 92 mpa, 7.2 gpa and 24.9 kj/m 2 respectively. for untreated fiber composite, about 26% improve in ts, 11% increment in tm, 28% increase in bs, 23% improvement in bm and 10% increment in is was found compared to non-irradiated sample. for composite made of treated fiber, about 27% improvement in ts, 12% increment in tm, 27% improvement in bs, 33% higher in bm and 9% improvement in is was found compared to non-irradiated composite. the mechanical characteristics of the resultant composite are effected by the strength of interfacial bond between pp and reinforcing fiber. interfacial bond strength was developed due to γ treatment by generating active sites. subsequently, due to the formation of cross-link, the mechanical attributes of the irradiated composites were enriched up to 5.0 kgy dose. it may be supposed that stress transfer between fiber and matrix was better at 5.0 kgy dose which leads to cracks avoiding at the fiber. a possible reaction mechanism between cellulose and polypropylene during irradiation treatment is given in figure 9 (a) and (b). figures indicate that γ irradiation directly affects the internal configuration of the cellulosic fiber and creates some active sites in of and pp by subtraction of electrons which lead to form of/pp complex and as a result, better interfacial bonding could occur between them. this complex formation might be the motive behind the enhanced mechanical properties [42]. but above 5.0 kgy dose, the irradiated composites showed reduced mechanical properties. the fact behind that, due to acquaintance of high energy γ radiation the polymer chains are broken which causes the degradation of pp matrix and cellulose backbone. during the degradation, due to breakage of primary bond in the cellulose components, the strength will loose and therefore, the deviations take place in the central lamella, which reduce the ultimate strength [43]. figure 9: (a) chain scission mechanism of cellulose during γ irradiation figure 9: (b) a possible cross-linking mechanism between cellulose and pp molecules. 3.4 water absorption behavior of the composites the optimized composite samples (45% fiber content) were dipped in deionized stationary water bath for around 90 hrs. the mass of the samples was determined by with drawling them after a certain time interval from the water bath. the obtained results were shown in figure 10 against time. it was examined that the virgin composite samples showed a considerable amount of absorption than treated one. the absorption rate was optimum within the first 10 hr by both type of samples, and then the swelling rate became slow and static with time for treated composite, while the virgin sample continued to soak water very slowly. the virgin composite specimen gained highest water absorption up to 9.85%, whereas the treated sample yielded 7.12% water of its weight. the cause for lower absorption by the treated specimen might be the fact that vacant space of fiber filled by the polymer. rahman, et al. (2018): international journal of engineering materials and manufacture, 3(1), 18-31 26 creation of intermolecular hydrogen bonds with neighboring cellulose can be the reason for increasing moisture absorption. due to alkali treatment, some of the hydroxyl groups are replaced and the hygroscopicity of lingocellulosic fiber is reduced. mercerization also increased crystallinity in the fiber. in the crystalline part, the hydroxyl groups are cross-linked so, there is no space available to retain water [43]. figure 10: water absorption of the optimized composites (45% fiber) against different soaking period. figure 11: loss of tensile strength of the optimized composites (45% fiber) against time. 3.5 thermal degradation of the composites degradation of the composites in heat medium was done by heating the specimens in an oven for 30 days at 90ºc. the ts of the composite samples was determined after a certain period and loss (%) of ts is shown in figure 11. the raw and mercerized samples lost the tensile strength of 28, 22% respectively after 30 days of thermal aging and the values were 23.8 and 29.9 mpa respectively. from thermal degradation test, it is noticed that the fabrication, mechanical characterization and interfacial properties of okra fiber reinforced polypropylene composites 27 untreated composite lost a considerable amount of tensile properties while the treated one retained much of their properties. the degradation behavior of fiber-reinforced composites is related to the breakage of glycosidic linkages of cellulose firstly; the second relevant to the depolymerization of the α-cellulose, hemicellulose and pectin [44]. 3.6 soil degradation study the discontinuous fiber composites of 45% fiber content were buried in soil and degradation test was carried out up to 24 weeks. the results of ts and tm were shown in figure 12 and 13. it was clear for both types of composites that, the tensile properties lessened phenomenally with time interval. after 8 weeks observation, untreated and treated of composites lost nearly 20 and 16% of ts, 9 and 7% of tm respectively. after 5 months of soil degradation, both untreated and treated fiber composites showed a substantial loss of strength. virgin and mercerized fiber composites lost 32 and 26% strength respectively. in the same period, untreated fiber composites lost almost 17% tm and treated fiber composites lost 15% tm. the value of tensile strength and modulus was found to be 22.5 and 510 mpa for untreated and 28.8 and 572 mpa for the treated sample after 5 months of degradation. the strong attraction was found in cellulosic fibers to damage when they are kept under the soil medium. the water molecule enters into the cutting ends of the composites under the soil medium and as a result, the cellulose degraded sufficiently which reduce the tensile properties of the composites significantly. figure 12: tensile strength degradation of the optimized composites (45% fiber) in soil medium. figure 13: tensile modulus degradation of the optimized composites (45% fiber) in soil medium. rahman, et al. (2018): international journal of engineering materials and manufacture, 3(1), 18-31 28 3.7 examination of interfacial properties sem micrographs were used to understand the interfacial bonding of the composites. figures 14 (a), (b) and figures 14 (c) and (d) show the tensile fracture surface of the virgin and mercerized composites (45% fiber). the figures specified that the raw fiber partly adhered to the binder material, demonstrating the weak interfacial bonding between fiber and matrix. it is detected that the fiber diameters are different and found 0.08-0.20 mm (figure 15), the fiber surface is harsh and small amount of fibers and particles adhered. on the other hand, the mercerized fiber was entirely bounded with the pp matrix demonstrating an improved fiber-matrix bonding. as a result enhanced stress transfer occurred between the reinforcing fibers and matrix material. from the images, the debonding of the pp and of is also found. these recommend that the bonding between matrix and reinforcing fiber can be developed further. the physico-mechanical behaviors of composites significantly depend on the interfacial bond strength between reinforcement and matrix. therefore, it is reflected that the tensile, bending and impact behaviors of the composite material can be further optimized by the use of appropriate coupling agents. (a) (b) figure 14: (a), (b) sem micrographs of untreated fiber composite (c) (d) figure 14: (c), (d) sem micrographs of treated fiber composite fabrication, mechanical characterization and interfacial properties of okra fiber reinforced polypropylene composites 29 (a) (b) figure 15: (a), (b) microscopic view of fibers with the measurement of diameter 4 conclusions okra fiber reinforced polypropylene composites were fabricated successfully using compression molding technique and physicomechanical behaviors were assessed. it can be concluded that: 1. the tensile, impact and bending behaviors of the resultant mercerized fiber composites were enriched than the virgin fiber composites. the investigation also showed that at 45% fiber content, the mechanical performance of the composites was the best than all other fiber content. 2. the soil and thermal resistance behaviors of composites were developed when composites were mercerized. water absorption capability was also reduced due to mercerization. γ irradiation was found to be a potential source to improve the physicomechanical properties of of/pp composites. soil degradation test indicated that the composites retained their inherent biodegradation behavior. 3. sem analysis revealed that fiber and pp matrix was in good adhesion and also weak interfacial bonding was found due to agglomeration of randomly orientated fibers which reduces the ultimate mechanical properties of the composites. sem image also indicated that the interfacial affection between polypropylene and fiber could be developed further by using coupling agent with the proper embedding of fibers during manufacturing of composites. 4. the tensile fracture samples were selected for sem analysis only. if sem could be done on bending and impact strength tested samples it would be more supportive to observe the interfacial bonding between reinforcement and matrix material. 5. finally, it had been observed that of/pp composites possessed sufficient physical and mechanical properties which established that okra fiber can be a potential candidate for using as reinforcement in the polymer composite area for diversified applications. acknowledgement the authors are grateful to dr. mubarak ahmad khan, the director general of bangladesh atomic energy commission, for giving the opportunity to conduct experimental works in polymer composite laboratory under institute of radiation and polymer technology, dhaka, bangladesh. references 1. alam, m. s., & khan, g. a. (2007). chemical analysis of okra bast fiber (abelmoschus esculentus) and its physico-chemical properties. journal of textile and apparel technology and management, 5(4). 2. albano, c., gonzalez, j., ichazo, m., & kaiser, d. (1999). thermal stability of blends of polyolefins and sisal fiber. polymer degradation and stability, 66(2), 179-190. 3. ayre, b. g., stevens, k., chapman, k. d., webber, c. l., dagnon, k. l., & d'souza, n. a. (2009). viscoelastic properties of kenaf bast fiber in relation to stem age. textile research journal, 79(11), 973-980. 4. blouin, f. a., & arthur, j. c. (1958). the effects of gamma radiation on cotton part i: some of the properties of purified cotton irradiated in oxygen and nitrogen atmospheres. textile research journal, 28(3), 198-204. 5. botelho, e., pardini, l., & rezende, m. (2005). hygrothermal effects on damping behavior of metal/glass fiber/epoxy hybrid composites. materials science and engineering: a, 399(1), 190-198. 6. bullions, t., gillespie, r., price‐o'brien, j., & loos, a. (2004). the effect of maleic anhydride modified polypropylene on the mechanical properties of feather fiber, kraft pulp, polypropylene composites. journal of applied polymer science, 92(6), 3771-3783. rahman, et al. (2018): international journal of engineering materials and manufacture, 3(1), 18-31 30 7. cantero, g., arbelaiz, a., llano-ponte, r., & mondragon, i. (2003). effects of fibre treatment on wettability and mechanical behaviour of flax/polypropylene composites. composites science and technology, 63(9), 1247-1254. 8. cheung, h.-y., lau, k.-t., tao, x.-m., & hui, d. (2008). a potential material for tissue engineering: silkworm silk/pla biocomposite. composites part b: engineering, 39(6), 1026-1033. 9. czvikovszky, t. (1995). reactive recycling of multiphase polymer systems through electron beam. nuclear instruments and methods in physics research section b: beam interactions with materials and atoms, 105(1-4), 233-237. 10. dey, k., khan, r. a., & chowdhury, a. s. (2012). study on the mechanical, degradation, and interfacial properties of calcium alginate fiber-reinforced polyethylene oxide composites. journal of thermoplastic composite materials, 25(7), 807-819. 11. fortunati, e., puglia, d., monti, m., santulli, c., maniruzzaman, m., foresti, m., vazquez, a. & kenny, j.m. (2013). okra (abelmoschus esculentus) fibre based pla composites: mechanical behaviour and biodegradation. journal of polymers and the environment, 21(3), 726-737. 12. fortunati, e., puglia, d., monti, m., santulli, c., maniruzzaman, m., & kenny, j. m. (2013). cellulose nanocrystals extracted from okra fibers in pva nanocomposites. journal of applied polymer science, 128(5), 3220-3230. 13. gogus, f., & maskan, m. (1999). water adsorption and drying characteristics of okra hibiscus esculentus l. drying technology, 17(4-5), 883-894. 14. gowda, t. m., naidu, a., & chhaya, r. (1999). some mechanical properties of untreated jute fabricreinforced polyester composites. composites part a: applied science and manufacturing, 30(3), 277-284. 15. hassan, m. m., islam, m. r., & khan, m. a. (2005). surface modification of cellulose by radiation pretreatments with organo-silicone monomer. polymer-plastics technology and engineering, 44(5), 833-846. 16. idicula, m., & thomas, s. (2004). effect of fibre loading and fibre ratio on the mechanical properties of intimately mixed banana/sisal hybrid fibre reinforced composites. paper presented at the 5th global wood and natural fibre composites symposium, kassel, germany. 17. islam, t., khan, r. a., khan, m. a., rahman, m. a., fernandez-lahore, m., huque, q., & islam, r. (2009). physico-mechanical and degradation properties of gamma-irradiated biocomposites of jute fabric-reinforced poly (caprolactone). polymer-plastics technology and engineering, 48(11), 1198-1205. 18. jawaid, m., khalil, h. a., bakar, a. a., & khanam, p. n. (2011). chemical resistance, void content and tensile properties of oil palm/jute fibre reinforced polymer hybrid composites. materials & design, 32(2), 1014-1019. 19. john, k., & naidu, s. v. (2004). sisal fiber/glass fiber hybrid composites: the impact and compressive properties. journal of reinforced plastics and composites, 23(12), 1253-1258. 20. joseph, p., joseph, k., & thomas, s. (2002). short sisal fiber reinforced polypropylene composites: the role of interface modification on ultimate properties. composite interfaces, 9(2), 171-205. 21. karina, m., onggo, h., abdullah, a. d., & syampurwadi, a. (2008). effect of oil palm empty fruit bunch fiber on the physical and mechanical properties of fiber glass reinforced polyester resin. journal of biological sciences, 8(1), 101-106. 22. khalil, h. a., hanida, s., kang, c., & fuaad, n. n. (2007). agro-hybrid composite: the effects on mechanical and physical properties of oil palm fiber (efb)/glass hybrid reinforced polyester composites. journal of reinforced plastics and composites, 26(2), 203-218. 23. khan, g. a., shaheruzzaman, m., rahman, m., razzaque, s. a., islam, m. s., & alam, m. s. (2009). surface modification of okra bast fiber and its physico-chemical characteristics. fibers and polymers, 10(1), 65-70. 24. khan, m., hinrichsen, g., & drzal, l. (2001). influence of novel coupling agents on mechanical properties of jute reinforced polypropylene composite. journal of materials science letters, 20(18), 1711-1713. 25. khan, m., kopp, c., & hinrichsen, g. (2001). effect of vinyl and silicon monomers on mechanical and degradation properties of bio-degradable jute-biopol® composite. journal of reinforced plastics and composites, 20(16), 1414-1429. 26. khan, m. a., khan, r. a., haydaruzzaman, ghoshal, s., siddiky, m., & saha, m. (2009). study on the physicomechanical properties of starch-treated jute yarn-reinforced polypropylene composites: effect of gamma radiation. polymer-plastics technology and engineering, 48(5), 542-548. 27. khan, r. a., khan, m. a., sarker, b., saha, s., das, a. k., noor, n., . . . saha, m. (2010). fabrication and characterization of gelatin fiber-based linear low-density polyethylene foamed composite. journal of reinforced plastics and composites, 29(16), 2438-2449. 28. lapique, f., meakin, p., feder, j., & jøssang, t. (2000). relationships between microstructure, fracture–surface morphology, and mechanical properties in ethylene and propylene polymers and copolymers. journal of applied polymer science, 77(11), 2370-2382. 29. miah, m., ahmed, f., hossain, a., khan, a., & khan, m. a. (2005). study on mechanical and dielectric properties of jute fiber reinforced low-density polyethylene (ldpe) composites. polymer-plastics technology and engineering, 44(8-9), 1443-1456. 30. mishra, a., & pal, s. (2007). polyacrylonitrile-grafted okra mucilage: a renewable reservoir to polymeric materials. carbohydrate polymers, 68(1), 95-100. fabrication, mechanical characterization and interfacial properties of okra fiber reinforced polypropylene composites 31 31. mishra, s., mohanty, a. k., drzal, l. t., misra, m., & hinrichsen, g. (2004). a review on pineapple leaf fibers, sisal fibers and their biocomposites. macromolecular materials and engineering, 289(11), 955-974. 32. mohanty, a., khan, m. a., & hinrichsen, g. (2000). surface modification of jute and its influence on performance of biodegradable jute-fabric/biopol composites. composites science and technology, 60(7), 1115-1124. 33. mohanty, a., misra, m., & hinrichsen, g. (2000). biofibres, biodegradable polymers and biocomposites: an overview. macromolecular materials and engineering, 276(1), 1-24. 34. monteiro, s. n., calado, v., rodriguez, r. j., & margem, f. m. (2012). thermogravimetric stability of polymer composites reinforced with less common lignocellulosic fibers–an overview. journal of materials research and technology, 1(2), 117-126. 35. pan, p., zhu, b., dong, t., serizawa, s., iji, m., & inoue, y. (2008). kenaf fiber/poly (ε‐caprolactone) biocomposite with enhanced crystallization rate and mechanical properties. journal of applied polymer science, 107(6), 3512-3519. 36. rahman, m. r., huque, m. m., islam, m. n., & hasan, m. (2008). improvement of physico-mechanical properties of jute fiber reinforced polypropylene composites by post-treatment. composites part a: applied science and manufacturing, 39(11), 1739-1747. 37. rajulu, a. v., & devi, r. r. (2007). tensile properties of ridge gourd/phenolic composites and glass/ridge gourd/phenolic hybrid composites. journal of reinforced plastics and composites, 26(6), 629-638. 38. saba, n., paridah, m., & jawaid, m. (2015). mechanical properties of kenaf fibre reinforced polymer composite: a review. construction and building materials, 76, 87-96. 39. sathishkumar, t., navaneethakrishnan, p., shankar, s., rajasekar, r., & rajini, n. (2013). characterization of natural fiber and composites–a review. journal of reinforced plastics and composites, 32(19), 1457-1476. 40. sawpan, m. a., khan, m. a., & abedin, m. (2003). surface modification of jute yarn by photografting of low‐ glass transition temperature monomers. journal of applied polymer science, 87(6), 993-1000. 41. shubhra, q. t., alam, a., & quaiyyum, m. (2013). mechanical properties of polypropylene composites: a review. journal of thermoplastic composite materials, 26(3), 362-391. 42. zaman, h. u., khan, a., hossain, m., khan, m. a., & khan, r. a. (2009). mechanical and electrical properties of jute fabrics reinforced polyethylene/polypropylene composites: role of gamma radiation. polymer-plastics technology and engineering, 48(7), 760-766. 43. zaman, h. u., khan, m. a., khan, r. a., mollah, m., pervin, s., & al-mamun, m. (2010). a comparative study between gamma and uv radiation of jute fabrics/polypropylene composites: effect of starch. journal of reinforced plastics and composites, 29(13), 1930-1939. 44. zaman, h. u., khan, r. a., khan, m. a., & beg, m. d. h. (2013). physico-mechanical and degradation properties of biodegradable photografted coir fiber with acrylic monomers. polymer bulletin, 70(8), 22772290. international journal of engineering materials and manufacture (2021) 6(1) 22-33 https://doi.org/10.26776/ijemm.06.01.2021.02 hossain, m.z. 1 , hossain, m.j. 2 , rahman, m.m. 1 , hasan, m.d.m. 1 and alam, m.a. 1 1 department of mechanical engineering, dhaka university of engineering and technology gazipur-1707, bangladesh 2 institute of energy engineering, dhaka university of engineering and technology gazipur-1707, bangladesh e-mail: sumon1314@yahoo.com reference: hossain et al., (2021). generation of electricity by microbial fuel cells using industrial effluent. international journal of engineering materials and manufacture, 6(1), 22-33. generation of electricity by microbial fuel cells using industrial effluent md. zakir hossain, md. jakir hossen, m. mostaqur rahman, md. dewan mazharul hasan and md. ahasanul alam received: 03 december 2020 accepted: 29 december 2020 published: 30 january 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract a microbial fuel cell (mfc) is a device that converts bio-chemical energy into electrical energy during substrate oxidation with the aid of microorganisms (bacteria). the energy contained in waste water is converted to the electrical power by the action of bacteria. the principle of mfc is to transfer electrons from the microorganisms to electron acceptor at a higher electrochemical potential. an experimental study was performed to find the most efficient industrial waste water that can produce highest and stable electrical power by the mfc and to determine the removal rate of pollutant from the waste water by the mfc. two mfc, namely one pem mfc and two pem fmc, has been fabricated for this study. the three different waste water samples used were dyeing waste water-1 (dww-1), dairy industry waste water (diww) and dyeing waste water-2 (dww-2). the highest rate of voltage generation is achieved when the mfc was operated with dww-1 (1.06 v), diww (0.95 v) and dww-2(0.644 v), respectively. based on the graph pattern the dww-1 provided the best record in terms of electrical energy generation. keywords: microbial fuel cell (mfc), industrial waste water, proton exchange membranes (pem) 1. introduction in globalization era, people faces energy insecurity and climate change due to depletion of non-renewable energy and global warming. in present situation of the world, most of the energy comes from non-renewable energy sources. but the source of non-renewable energy are limited. after certain time non-renewable energy will be finished. so everyday researcher try to find the new sustainable, renewable and alternative sources of energy. there are lot of renewable energy sources found by the researcher. microbial fuel cell is one of them. it’s a promising technology to meet increasing energy needs using wastewaters as substrates for producing electricity and also wastewater treatment[1]. mfc does not use commercially due to low power generation and its high cost [2]. researcher always try to overcome this limitation for development the performance and commercialization of mfcs. microbial fuel cell (mfc) is a green energy technology which used for electricity generation, wastewater treatment, bioremediation, biosensors hydrogen production[3] and biological oxygen demand (bod) sensors[4]. depend on design, mfc can be classified into two group: single chambered and double chambered. the single chambered mfc contain both cathode and anode in one chamber. on the other hand double chambered mfc contain separate cathode and anode. in double chambered mfc cathode and anode chamber are separate by proton exchange membrane[5]. the function and efficiency of mfc for power production is mainly depend on the following factors nature of carbon source used, fuel cell configuration, nature and type of electrode, mediators present in the cathode chamber, electrolytes used[6], operating temperature[7] and nature of the proton exchange membrane[8]. at present, the power industry faces difficulties ensuring the production of greater volumes of energy to meet the increased demand. simultaneously, the production of waste and wastewater increases considerably. this means that large amounts of industrial and municipal wastewater may be generated. the traditional design of a wastewater treatment plant consumes a lot of energy to perform efficiently, and this generates considerable costs. in this context, it is clear that it is important to decrease the costs of wastewater treatment. nowadays, there are different ideas for the use of wastewater as a raw material for other technologies, and there has been fast development in renewable generation of electricity by microbial fuel cells using industrial effluent 23 sources of energy using wastewater. a microbial fuel cell (mfc) is device that can produce electricity with wastewater treatment [9]. energy is expelled from wastewater by anaerobic digestion from different substrate[10]. the high energy requirements of conventional wastewater treatment systems are demanding for an alternative treatment technology. this treatment technology should be cost effective, requiring less energy for its efficient operation, and should generate energy in such a form that would make overall operation of wastewater treatment self-sustainable. organic matter present in the wastewater can be considered a valuable material acting as a renewable source of energy. the energy available in organic wastewaters can be harvested as electricity by using microbial fuel cell (mfc). in this case to catalyze the conversion of organic matter into direct electricity while accomplishing the biodegradation of organic matter to carbon dioxide as an end product the bacteria can be used. use of mfc for wastewater treatment has various advantages, such as a high efficiency for energy conversion of the organic matter into electricity, working at lower mesophilic temperatures, and the absence of any toxic products. in addition, wastewaters can be used as substrates in mfc to produce electricity[11] and compensate the cost of treatment. if mfcs are used for wastewater treatment, can provide clean and safe energy for people, apart from effective treatment of the wastewaters with and low noise and emissions. although, many researchers have performed extensive studies on the construction and analysis of mfcs in the last twenty years. but, clear information on the construction and analysis of mfcs is still limited and not clarified yet. 2. materials and methods 2.1 experimental setup microbial fuel cell basically contains an anode chamber, a cathode chamber, pem or salt bridge, external circuit[12] and electrode assembly. many different configurations are used in mfcs. the most common configuration is a two chamber mfc with “h” shape, consisting of two bottles connected by a tube with a proton exchange membrane in the middle[13]. the key point to this design is the use of a small membrane separating the two chambers. however, these mfcs typically have a high internal resistance because of the long distance between the two electrodes and the small surface area of the membrane, hence limiting power density output. two-chamber mfcs are basically use in batch mode and also can run in continuous mode[14]. they are especially suitable for laboratory research, such as examining power production using new substrates, electrode materials, membranes or types of microbial communities that arise during the degradation of specific compounds, or for mfc based sensors. performance of an mfcs are mainly depend on the following factors configuration of electrode, electrode materials, membranes, mediators and the biocatalysts[15]. the following figures shows the experimental setup for the analysis mentioned: figure 1: experimental setup of two chambered mfc with one pem figure 2: experimental setup of two chambered mfc with two pem 2.2 electrodes power density of a microbial fuel cell (mfc) mainly depends on the performance of electrodes. so electrode plays a vital role on mfcs. there are different types of electrodes which can be used in mfc. carbonaceous and metallicbased electrodes are mainly used in mfcs. among them carbonaceous materials, carbon cloth, carbon brush, carbon rod, carbon mesh, carbon veil, carbon paper, carbon felt, granular activated carbon, granular graphite, carbonized cardboard, graphite plate and reticulated vitreous carbon are commercially available. metal based materials such as stainless steel plate, stainless steel mesh, stainless steel scrubber, silver sheet, nickel sheet, copper sheet, gold sheet and titanium plate are commercially available. carbon-based nanomaterial’s such as carbon nanotubes (cnts), allotropes of carbon and composite materials such as cnt–polyaniline are used as electrode[16]. as an electrode material carbon nanotube platinum (cnt/pt)coated carbon paper(cp) are used in dual-chambered mfcs[17]. the following features should have the electrode material i) electrical conductivity; ii) resistance to corrosion; iii) high mechanical strength; iv) developed surface area; v) biocompatibility; vi) environmentally friendly and vii) low cost[18]. based on these features following electrode materials were used in this study: copper (cu), aluminum (al), carbon(c) and brass. high internal resistance of electrode material effects on output power of mfc. sustainability and cost of electrode materials are an important issue[19]. hossain et al. (2021): international journal of engineering materials and manufacture, 6(1), 22-33 24 table 1: different types of electrode material with size electrode material cross section copper 13.2cm*5.5cm aluminium 13.2cm*5.5cm brass 13.2cm*5.5cm carbon 15.5 cm bar with 1 cm diameter figure 3: copper electrode figure 4: aluminium electrode figure 5: carbon electrode figure 6: brass electrode 2.3 proton exchange membranes (pems) a proton-exchange membrane (pem), is a semipermeable membrane which permit to transfer proton from anode chamber to cathode chamber. it’s a separator which separate the anode and the cathode. it prevent the mixing of substrate in anode and cathode chambers, especially by effluent, co2, and oxygen[20]. in mfc nafion, cellophane, agar composition etc. are usually used as proton exchange membranes (pem) [21]. the power density of a mfc also depends on the performance of pem. if the surface area of electrode is larger than the area of pem the power output decreases. logan and sang identify that power density increases if the area is in the ratio 2aanode=apem=2acathode [21]. the experiment was conducted with an agar salt bridge as a pem. the pem made with 1 mole of kcl and 10% of agar solution. one another salt bridge used as a pem which made with 1 mole of nacl and 10% of agar solution. the diameter and length of the salt bridge is 2cm and 15 cm respectively. 2.4 method the mfc reactor (fig. 1 & fig. 2) was designed and fabricated from acrylic material. it consisted of two chambers (1 liter each) for the anode and cathode compartment, which were separated by a pem (d =2 cm). the cathode chamber of mfc was filled with normal water as a catholyte. the anode chamber was filled with the wastewater samples. the cathode and anode electrodes that were used composed of different metallic electrodes mentioned above. the cathode and the anode are connected with an external circuit by using connecting wires. both sides of the anodic chamber and cathodic chamber are capped tightly to avoid the addition of unwanted material throughout the entire mfc process (until the voltage became zero or stable as long as 50 hours). a digital multi meter is connected to a resistor in a parallel circuit to measure and record the open electric voltage produced by the electric flow in the mfc throughout the process. chemical oxygen demand (cod) and total kjedahl nitrogen (tkn) were measured before and after the mfc operation to determine the rate of carbon and nitrogen removal in wastewater. the ph value of the wastewater is observed to identify suitable ph conditions for bacterial growth during mfc operation. the mfc operation is conducted by testing on three types of wastewater samples: dyeing waste water1, dairy food waste water and dyeing waste water-2. https://en.wikipedia.org/wiki/ion-exchange_membranes generation of electricity by microbial fuel cells using industrial effluent 25 figure 7: side view of salt bridge made with kcl, nacl and agar figure 8: cross sectional view of salt bridge made with kcl, nacl and agar 2.5 two salt bridge mfc to increase the proton exchange area through the pem, two salt bridges were made from the kcl and agar and attached to the set up as shown in fig. 2. the other processes were same followed by single pem mfc. during this process copper electrode were used in both anode and cathode chamber. 3. results & discussion 3.1 dyeing waste water-1 (dww-1) as large surface area increases the proton exchange rate, so the observation was starts with making two salt bridges with two chambered mfc. according to fig. 9 the open-circuit voltage at the beginning of the study was recorded as 0.52 v and maximum voltage was found as 0.559 v. based on the pattern of the graph shown, the voltage generation increased from the beginning for a small time because of the formation of the biofilm of microorganisms of the waste water and then decreased gradually without increasing until the last observable voltage found. the voltage decreases because of the microorganisms start to compete each other to obtain their foods from the organic matter and nutrients in the waste water [22]. in this case copper electrode were used in both anode and cathode side. 0.2 ma stable current was found by one pem mfc. when using the same electrodes (copper) for one pem different results of voltage were found with respect to time. the voltages found using one pem were found small than that found by two pem mfc. in this case starting voltage was found as 0.291 v and maximum voltage was 0.35 v. the graph pattern showed in fig. 10 is almost similar to fig. 9 including low voltages than previous. similarly, 0.2 ma stable current was found by one pem mfc. by using aluminium as anode and brass as cathode of similar size of copper electrode observable change was found in voltage and current. the fig. 11 shows the graphical representation of time and voltage of dww-1 when using one pem. in this case the voltages were observed till 85 hours. the starting voltage, maximum voltage was found as 1.017 v and 1.06 v respectively. the current was found as 0.7 ma (stable). table 2: electricity production from dyeing waste water-1 (two salt bridges) with respect to time time (hours) electricity production (v) time (hours) electricity production (v) time (hours) electricity production (v) 0 0.52 9 0.419 18 0.165 1 0.559(max) 10 0.35 19 0.1 2 0.545 11 0.283 20 0.085 3 0.53 12 0.265 21 0.05 4 0.52 13 0.263 22 0.02 5 0.511 14 0.25 23 0.005 6 0.5 15 0.22 24 0 7 0.493 16 0.19 8 0.433 17 0.175 hossain et al. (2021): international journal of engineering materials and manufacture, 6(1), 22-33 26 figure 9: electricity production versus time for dyeing waste water-1 (two salt bridges) table 3: electricity production from dyeing waste water-1 (one salt bridges) with respect to time time (hours) electricity production (v) time (hours) electricity production (v) time (hours) electricity production (v) 0 0.291 9 0.256 18 0.158 1 0.35(max) 10 0.24 19 0.144 2 0.32 11 0.231 20 0.129 3 0.31 12 0.223 21 0.1 4 0.305 13 0.22 22 0.07 5 0.3 14 0.209 23 0.065 6 0.28 15 0.2 24 0.003 7 0.275 16 0.18 8 0.26 17 0.165 figure 10: electricity production versus time for dyeing waste water-1 (one salt bridge) generation of electricity by microbial fuel cells using industrial effluent 27 table 4: electricity production from dyeing waste water-1 with respect to time (aluminium anode, brass cathode) time (hours) electricity production (v) time (hours) electricity production (v) time (hours) electricity production (v) time (hours) electricity production (v) 0 1.017 22 1.028 44 0.993 66 0.956 1 1.06(max.) 23 1.024 45 0.99 67 0.956 2 1.058 24 1.022 46 0.99 68 0.955 3 1.055 25 1.02 47 0.988 69 0.954 4 1.05 26 1.018 48 0.986 70 0.954 5 1.047 27 1.017 49 0.984 71 0.953 6 1.045 28 1.016 50 0.976 72 0.953 7 1.045 29 1.0012 51 0.973 73 0.952 8 1.042 30 1.009 52 0.97 74 0.952 9 1.04 31 1.003 53 0.971 75 0.951 10 1.04 32 1.003 54 0.971 76 0.951 11 1.038 33 1.003 55 0.972 77 0.951 12 1.036 34 1.002 56 0.972 78 0.951 13 1.035 35 1.002 57 0.972 79 0.951 14 1.029 36 1.001 58 0.972 80 0.949 15 1.027 37 1.001 59 0.97 81 0.948 16 1.025 38 1.001 60 0.967 82 0.948 17 1.023 39 0.999 61 0.965 83 0.948 18 1.039 40 0.999 62 0.963 84 0.948 19 1.032 41 0.999 63 0.961 85 0.948 20 1.028 42 0.995 64 0.959 21 1.028 43 0.993 65 0.957 figure 11: electricity production versus time for dyeing waste water-1 3.2 dairy industry waste water (diww) based on fig. 12 the initial voltage recorded by mfc that run with the diww is 0.27 v and the maximum voltage is found as 0.716 v. the voltage data was observed for 50 hours. the rate of electric voltage produced experiences a rapid increase for first five hours then decreased slowly for next ten hours. after that the voltages increased gradually and stable for last ten hours. the factor that can be explain that to the sudden drops in voltage is the thickness of biofilm on the electrode surface. the biofilm is the film that produced by microorganisms. the maximum voltage can be obtained whenever this thickness is at moderated condition; not thick or thin. this simultaneous increase and decrease in the electric voltage reading is predicted to continue until all the microorganisms in the waste water are dead and no electric voltage can be generated at the end. the current was found by the mfc was 0.6 ma. based on fig. 13 aluminium was used as anode, brass was used as cathode and the voltage reading was taken for 85 hours. with an observable change in voltage the initial voltage was found as 0.85 v and maximum voltage was found as 0.95 v (which was found initially). the graph pattern shows more fluctuations in voltage with time within a small range of voltage. finally, at the last hours the voltage found stable in 0.8 v. this fluctuation of voltage occurred due to condition of biofilm thickness that explained above. hossain et al. (2021): international journal of engineering materials and manufacture, 6(1), 22-33 28 table 5: electricity production from dairy industry waste water (one salt bridges) with respect to time time (hours) electricity production (v) time (hours) electricity production (v) time (hours) electricity production (v) time (hours) electricity production (v) 0 0.27 13 0.58 26 0.602 39 0.705 1 0.42 14 0.56 27 0.604 40 0.71 2 0.394 15 0.546 28 0.606 41 0.715 3 0.59 16 0.546 29 0.608 42 0.714 4 0.617 17 0.548 30 0.608 43 0.715 5 0.646 18 0.549 31 0.609 44 0.715 6 0.666 19 0.57 32 0.611 45 0.716(max) 7 0.666 20 0.572 33 0.628 46 0.716 8 0.665 21 0.574 34 0.64 47 0.716 9 0.666 22 0.576 35 0.66 48 0.715 10 0.65 23 0.6 36 0.67 49 0.715 11 0.62 24 0.604 37 0.68 50 0.716 12 0.6 25 0.605 38 0.7 figure 12: electricity production versus time for dairy industry waste water (one salt bridge) figure 13: electricity production versus time for dairy industry waste water generation of electricity by microbial fuel cells using industrial effluent 29 table 6: electricity production from dairy industry wastewater with respect to time (aluminium anode, brass cathode) time (hours) electricity production (v) time (hours) electricity production (v) time (hours) electricity production (v) time (hours) electricity production (v) 0 0.85 22 0.94 44 0.83 66 0.87 1 0.95(max.) 23 0.93 45 0.83 67 0.86 2 0.95 24 0.93 46 0.83 68 0.85 3 0.94 25 0.93 47 0.83 69 0.84 4 0.94 26 0.93 48 0.83 70 0.84 5 0.94 27 0.93 49 0.83 71 0.83 6 0.93 28 0.88 50 0.83 72 0.83 7 0.93 29 0.85 51 0.83 73 0.82 8 0.92 30 0.84 52 0.83 74 0.82 9 0.92 31 0.83 53 0.82 75 0.8 10 0.91 32 0.83 54 0.82 76 0.85 11 0.91 33 0.83 55 0.82 77 0.89 12 0.91 34 0.83 56 0.82 78 0.87 13 0.89 35 0.83 57 0.84 79 0.85 14 0.89 36 0.83 58 0.85 80 0.85 15 0.89 37 0.83 59 0.87 81 0.85 16 0.88 38 0.84 60 0.89 82 0.84 17 0.88 39 0.85 61 0.9 83 0.82 18 0.88 40 0.84 62 0.92 84 0.8 19 0.88 41 0.84 63 0.91 85 0.8 20 0.9 42 0.84 64 0.90 21 0.92 43 0.83 65 0.89 figure 14: electricity production versus time for dyeing waste water-2 (one salt bridge) 3.3 dyeing waste water-2 (dww-2) referring to fig. 14 the voltage produced by the mfc when using one salt bridge and copper electrode in both anode and cathode side is higher than the voltage produced by dww-1. the initial and maximum voltage were found as 0.63 v and 0.729 v respectively. the rate of current was found as 0.2 ma (stable). from the experimental values collected it seems that there is an observable fluctuation in voltage rate. initially the voltage was increased for a small time and then decreased also for a small time. again, the voltage increased from six to twelve hour. after that the voltage further decreased for sixteen hours. these fluctuations occurred due to biofilm formation on the anode electrode for microorganisms. again, referring to fig. 15 the rate of voltage produced is less than the fig. 14 but the voltage is stable enough. in this case copper was used as anode and brass was used as cathode and data observed for 85 hours. the initial voltage is 0.487 v and the maximum voltage is 0.644 v. 0.6 ma stable current was found by the mfc. hossain et al. (2021): international journal of engineering materials and manufacture, 6(1), 22-33 30 table 7: electricity production from dyeing waste water-2 (one salt bridges) with respect to time time (hours) electricity production (v) time (hours) electricity production (v) time (hours) electricity production (v) time (hours) electricity production (v) 0 0.63 13 0.7 26 0.499 39 0.51 1 0.65 14 0.684 27 0.488 40 0.53 2 0.675 15 0.67 28 0.483 41 0.555 3 0.668 16 0.64 29 0.55 42 0.563 4 0.65 17 0.63 30 0.54 43 0.57 5 0.643 18 0.61 31 0.53 44 0.583 6 0.631 19 0.59 32 0.53 45 0.585 7 0.655 20 0.57 33 0.53 46 0.537 8 0.67 21 0.55 34 0.515 47 0.51 9 0.69 22 0.544 35 0.5 48 0.495 10 0.71 23 0.539 36 0.48 49 0.44 11 0.72 24 0.521 37 0.46 50 0.445 12 0.729(max.) 25 0.515 38 0.485 table 8: electricity production from dyeing waste water-2 with respect to time (aluminium anode, brass cathode) 3.4 comparison between three waste water samples fig. 16 shows the comparison between the open circuit voltages when using dww-1, diww and dww-2. all of the graphs are plotted in same scale to make a comparison between them. for the dww-1 the range of electric voltage produced is 0.291 to 0.00.3 v, for diww the range is 0.27 to 0.716 v and for dww-2 the range is 0.63 to 0.445 v. the maximum voltage produced by the mfc is 0.729 v by using dww-2. the different in voltage values is due to the presence of different microorganisms in waste waters. by observing the graph pattern, it can be concluded that the voltage produced by diww is more consistent than dww-1 and dww-2 on the basis of same electrode area, same quantity of waste water and one pem. also the fig. 17 shows the comparison between these three waste waters when aluminium used as anode and brass used as cathode for dww-1 and diww and copper as anode and brass as cathode for dww-2. the data was time (hours) electricity production (v) time (hours) electricity production (v) time (hours) electricity production (v) time (hours) electricity production (v) 0 0.487 22 0.612 44 0.595 66 0.598 1 0.546 23 0.61 45 0.594 67 0.598 2 0.546 24 0.609 46 0.594 68 0.598 3 0.545 25 0.608 47 0.594 69 0.599 4 0.546 26 0.604 48 0.594 70 0.599 5 0.548 27 0.602 49 0.593 71 0.605 6 0.555 28 0.6 50 0.591 72 0.605 7 0.561 29 0.597 51 0.592 73 0.606 8 0.565 30 0.598 52 0.593 74 0.606 9 0.573 31 0.598 53 0.593 75 0.607 10 0.579 32 0.598 54 0.594 76 0.608 11 0.585 33 0.597 55 0.594 77 0.609 12 0.587 34 0.597 56 0.594 78 0.61 13 0.61 35 0.596 57 0.595 79 0.61 14 0.626 36 0.595 58 0.595 80 0.61 15 0.631 37 0.595 59 0.595 81 0.61 16 0.639 38 0.595 60 0.595 82 0.61 17 0.644(max.) 39 0.596 61 0.595 83 0.61 18 0.62 40 0.595 62 0.596 84 0.62 19 0.602 41 0.595 63 0.596 85 0.62 20 0.604 42 0.595 64 0.596 21 0.607 43 0.595 65 0.597 generation of electricity by microbial fuel cells using industrial effluent 31 observed for 85 hours for three waste water samples. brass is the best conductor of electron and can accumulate proton more efficiently than copper, aluminium and carbon. that is why the more stable voltage produced in the second case. according to fig. 17 the maximum voltage is 1.06 v and the ranges are for dww-1, 1.017 to 0.948 v, for diww, 0.85 to 0.8 v, and for dww-2, 0.487 to 0.62 v. in the case of dww-2 the voltage produced is less than others because of copper was used as anode. though copper is a good conductor but it is easily effected by bacteria while aluminium doesn’t. by observing the graph pattern, it can be concluded that dww-1 gives the most consistent voltage and also maximum voltage. figure 15: electricity production versus time for dyeing waste water-2 figure 16: comparison between the open circuit voltages when using dww-1, diww and dww-2 (1) 3.5 cow dung this observation was done with carbon electrode of round shape just like a rod. in this case the maximum voltage was found as 0.14 v with current 0.2 ma which is huge with the same setup arrangement, but the voltage produced was not stable. the initial voltage was 0.1 v and the voltage increased gradually up to 2 hours. after that the voltage was stable for next 3 hours. then the voltage decreased gradually for 9 hours. again it was starts to increase gradually for remaining hours. but the graph shows that the voltage was nearly stable with respect to time. carbon clothe gives the more stable voltage but expensive than others and that is why it cannot be used in mfc economically. hossain et al. (2021): international journal of engineering materials and manufacture, 6(1), 22-33 32 table 9: electricity production from cow dung with respect to time time (hours) electricity production (v) time (hours) electricity production (v) time (hours) electricity production (v) 0 0.1 10 0.113 20 0.125 1 0.11 11 0.11 21 0.127 2 0.121 12 0.107 22 0.128 3 0.122 13 0.105 23 0.129 4 0.122 14 0.104 24 0.131 5 0.122 15 0.107 25 0.132 6 0.119 16 0.116 26 0.135 7 0.118 17 0.114 27 0.138 8 0.116 18 0.12 28 0.14(max.) 9 0.114 19 0.122 figure 17: comparison between the open circuit voltages when using dww-1, diww and dww-2 (2) figure 18: electricity production versus time for cow dung (carbon electrode) 4. conclusion in this research, the performance of mfc by using different source of microorganism has been investigated. in the present investigation dyeing waste water-1 (dww-1), dairy industry waste water (diww), dyeing waste water2 (dww-2), and cow dung were used as source of microorganism. the copper, aluminium, brass and carbon were used as electrode. based on the experimental study, the main finding of the study can be summarized as follows: 1. in case of dyeing waste water-1 (dww-1), almost stable and maximum voltage was observed till 85 hours. the starting voltage, maximum voltage and current were found 1.017 v, 1.06 v and 07 ma, respectively. an aluminium, brass and copper were used as anode, cathode and electrode in single pem. generation of electricity by microbial fuel cells using industrial effluent 33 2. when copper electrodes were used for both anode and cathode side diww gave the satisfactory result. in this case initial and maximum voltage was observed 0.27 v and 0.71 v. but when aluminium was used as anode and brass used as cathode it gave maximum 0.95 v for 85 hours. 3. an aluminium as anode and brass as cathode gave maximum voltage for samples because the brass is the best conductor of electron and can accumulate proton more efficiently than copper, aluminium and carbon. it was concluded that for better performance of mfc, selection of source of microorganism and electrode materials are important. for further research, electrode material can be modified by doping, coating and heat treatment for better performance of mfc. it is remarkable that, microorganism of different substrate can be increased by using different types of catalyst. references [1] lu n, zhou s, zhuang l, zhang j and ni j 2009 electricity generation from starch processing wastewater using microbial fuel cell technology, biochemical engineering journal, 43 246–51 [2] choudhury p, prasad uday u s, bandyopadhyay t k, ray r n and bhunia b 2017 performance improvement of microbial fuel cell (mfc) using suitable electrode and bioengineered organisms: a review bioengineered 8 471–87 [3] kumar r, singh l, zularisam a w and hai f i 2017 microbial fuel cell is emerging as a versatile technology : a review on its possible applications , challenges and strategies to improve the performances. int j of engergy res, 42(2), 369-394 [4] guo k, hassett d j and gu t 2012 microbial fuel cells : electricity generation from organic wastes by microbes, ch9, 162-189 [5] chaturvedi v and verma p 2016 microbial fuel cell : a green approach for the utilization of waste for the generation of bioelectricity bioresour. bioprocess. 3(1), 1-14 [6] mohan s v, saravanan r, raghavulu s v, mohanakrishna g and sarma p n 2008 bioelectricity production from wastewater treatment in dual chambered microbial fuel cell ( mfc ) using selectively enriched mixed microflora : effect of catholyte 99(3) 596–603 [7] moon h, chang i s and kim b h 2006 continuous electricity production from artificial wastewater using a mediator-less microbial fuel cell. bioresource technol, 97 621–627 [8] scott k and shukla a k 2004 polymer electrolyte membrane fuel cells : principles and advances. rev environ sc bio/tech, 3(3) 273–80 [9] huang l and logan b e 2008 electricity generation and treatment of paper recycling wastewater using a microbial fuel cell appl. microbiol. biotechnol. 80 349–55 [10] gude v g 2018 microbial fuel cells for wastewater treatment and energy generation wastewater treatment in microbial fuel cells e an overview j. clean. prod. 122 287–307 [11] duteanu n m, ghangrekar m m, erable b and scott k 2010 microbial fuel cells an option for wastewater treatment environ. eng. manag. j. 9 1069–87 [12] li j 2013 an experimental study of microbial fuel cell for electricity generating: performance characterisation and capacity improvement, j sust bio energy, 3(3), 171–178 [13] logan b e, hamelers b, rozendal r, schröder u, keller j, freguia s, aelterman p, verstraete w and rabaey k 2006 microbial fuel cells: methodology and technology environ. sci. technol. 40 5181–92 [14] tharali a d, sain n and osborne w j 2016 microbial fuel cells in bioelectricity production front. life sci. 9 252–66 [15] bhargavi g, venu v and renganathan s 2018 microbial fuel cells: recent developments in design and materials iop conf. ser. mater. sci. eng. 330 [16] mustakeem 2015 electrode materials for microbial fuel cells: nanomaterial approach mater. renew. sustain. energy 4 1–11 [17] mashkour m and rahimnejad m 2015 effect of various carbon-based cathode electrodes on the performance of microbial fuel cell biofuel res. j. 2 296–300 [18] santoro c, arbizzani c, erable b and ieropoulos i 2017 microbial fuel cells: from fundamentals to applications. a review j. power sources 356 225–44 [19] hamed m s, majdi h s and hasan b o 2020 effect of electrode material and hydrodynamics on the produced current in double chamber microbial fuel cells acs omega 5 10339–10348 [20] palanisamy g, jung h y, sadhasivam t, kurkuri m d, kim s c and roh s h 2019 a comprehensive review on microbial fuel cell technologies: processes, utilization, and advanced developments in electrodes and membranes j. clean. prod. 221 598–621 [21] prasad j g and panda s 2018 microbial fuel cells : types of mfc and different source of substrate. intj latest technol eng mgt app sc, vii 158–65 [22] bohari z h, azhari n a, rahman n n a, baharom m f, jali m h, sulaima m f and izzuddin t a 2017 experimental study of bioelectricity-microbial fuel cell for electricity generation: performance characterization and capacity improvement j. teknol. 79 1–5 international journal of engineering materials and manufacture (2023) 8(3) 51-66 https://doi.org/10.26776/ijemm.08.03.2023.01 m. hazra , a. k. singh defence metallurgical research laboratory (dmrl)p.o. kanchanbagh, hyderabad 500 058, india e-mail: mhazra@dmrl.drdo.in reference: hazra and singh (2023). failure investigation on failed towing arm of an aircraft: a case of improper material processing and failed repair welding of a cast al-cu-si type aluminium alloy. international journal of engineering materials and manufacture, 8(3), 51-66. failure investigation on failed towing arm of an aircraft: a case of improper material processing and failed repair welding of a cast al-cu-si type aluminium alloy mrityunjoy hazra and ashok kumar singh received: 01 march 2023 accepted: 19 may 2023 published: 01 july 2023 publisher: deer hill publications © 2023 the author(s) creative commons: cc by 4.0 abstract present work describes the metallurgical failure investigation of a failed towing arm/bar. aircraft attached with this incident travelled a distance of 2 km with normal towing speed (8 km/hr). the component is said to have broken while turning to right from taxi track and then turning left about 15-20 o . the mating fracture pieces of the failed towing arm fork along with bent towing pin were analyzed for failure investigation. parent material of the towing arm has been found to be a cast al-cu-si alloy closely matching with the alloy 295 used in t6 condition. pin is made of mild steel. failure of the towing arm fork has been initiated by weld solidification cracking of the weld region at close to the fusion line. liquation cracks at heat affected zone (haz) have aggravated the situation further by weakening the microstructure and facilitating the crack propagation. grain boundary precipitates of al-cu-fe type in haz have facilitated the propagation of failure along with the liquation cracking. on the other hand, al-fe-mn type of precipitates sitting along the grain boundaries in weld area seems to have not facilitated the failure initiation unlike the solidification cracking. improper material processing has led to the weakening of the bulk microstructure and thus the component itself, by introduction of various defects (pores, grain fall out, thick al-cu-fe type of continuous grainboundary precipitates and cracking). weld repairing has been found to be a failure in al-cu-si system in the present component. keywords: towing arm, cast al-cu-si, repair welding, hot cracking, solidification cracking, liquation cracking, intergranular fracture, al-cu-fe grain boundary precipitates, al-fe-mn grain boundary precipitates. 1 introduction 1.1 background information generally, aircrafts are shifted from hanger to pan (operational parking area / shelters provided by the sites of the runway) by towing process. the towing distance depends on the locations of hanger and pan. the towing bar broke while turning to right from taxi track and then turning left about 15-20 o . the towing distance for this particular case is about 2 km. in further examination, it has been observed that the left side of the towing bar fork end broke during towing process on a normal track i.e., without significant slope from taxi track to pan. the aircraft towed almost 2 km and towing speed was normal about 8 km/hr. the mating fracture pieces of the failed towing arm fork along with bent towing pin were analyzed for failure investigation, while towing spool (part of aircraft which is attached with towing arm for pulling it along with tractor) was found to be intact (undamaged) and likewise not destroyed for analysis. present paper is thus concerned with the failure investigation of the failed towing arm fork along with bent towing pin. 1.2 literature review towing is a method of movement of large aircraft about the airport, flight line and hangar without use of engine power of an aircraft [1]. it is commonly carried out by towing with a tow tractor or tug. hand pushing on the correct areas of the aircraft may be helpful in the case of the small aircraft. certain qualified personnel are also sometimes permitted for taxiing the aircraft about the flight line. reckless or careless duty on towing an aircraft may cause hazard, resulting in damage to the aircraft and importantly injury to the personnel. thus, the specific instructions for each model of aircraft as prescribed in the manufacturer’s maintenance manual must be followed. a qualified person failure investigation on failed towing arm of an aircraft: a case of improper material processing and failed repair welding 52 is usually within the flight (before the flight is being moved for towing) deck to operate the brakes in case the tow bar fails or becomes unhooked. prevention of possible damage of the aircraft can then be reduced. various types of tow bars available for general use are by and large utilized for towing operations of different types. some special types of bars may be employed on a particular aircraft only. such types are built by the aircraft manufacturer. obtaining a sufficient tensile strength value to pull most aircraft has traditionally been the principal design criteria for these bars and very importantly, torsional or twisting loads are not intended at all. a schematic diagram of tow bar assembly is shown in fig. 1. figure 1: schematic diagram of a tow bar assembly two incidents of failures of towing bars in aircraft towing system (ats) have been reported in open literature, although with insignificant metallurgical input [2, 3]. in one case, shear pin broke and caused the failure of the whole system in airbus 319 [2]. in another case, shear bolt along with tow bar body broke in case of a boeing 707 aircraft [3]. fatigue mechanism has been attributed to be the cause of failure. usually, breakage of a tow bar is not a big issue to deal with. one has to replace the tow bar and a few minutes later the aircraft would be back on its way. however, it may have sometimes, secondary damaging effect (i.e. damage caused by the failure of tow bars) which may delay the flight schedule related activities significantly. one such incident of failure of a nose gear is reported as a result of failure of tow bars (would be referred as towing arms, heretofore) [4]. 2 experimental procedure both the failed towing arm fork and bent towing pin were at first visually examined with the help of naked eye and magnifying glass. photographs were taken in as-received condition from various orientations and preserved for future reference during the course of analysis. one of the mating fracture surfaces (dislodged piece) was extracted delicately without damaging the surface for further in-depth examination under scanning electron microscope (sem) equipped with electron dispersive spectroscopy (eds). the fracture surface was examined under sem after cleaning with acetone in an ultrasonic cleaner. subsequently, a representative cross-sectional sample was extracted from failed parts for detailed metallographic investigation. the broken piece of towing arm fork was sectioned into three parts across the thickness. it was done very delicately with the sequence of cold mounting followed by sectioning through slow speed isomet cutter. the polished sample surfaces were examined under optical microscope and sem. the bent portion of the towing pin was prepared for metallographic study in both the un-etched and etched conditions. keller’s reagent was used for etching the towing arm fork pieces, while 2 % nital was employed as etchant for towing pin. bulk compositional analysis of the failed components was carried out by x-ray florescence spectroscopy (xrf) and eds techniques followed by verification of results with those obtained from inductively coupled plasma optical emission spectroscopy (icp-oes). vickers hardness readings were taken at 5 kg load on metallographically prepared samples. 3 results 3.1 visual examination as-received failed components are shown in fig. 2. fractured towing arm fork end bent towing pin along with intact (undamaged) towing spool are seen. red colour paint is seen to cover the entire towing arm fork. fig. 3 reflects fracture surfaces of towing arm fork end in various views. typical brittle fracture of as-cast products seems to prevail, as is typified by coarseness of the fracture features. there is existence of well revealed weld regions in the surroundings of the fracture surfaces. probable detached/peeled off parts during service which seem to have been welded later on have been marked (fig. 3(d, e and f)). these are quite easily identifiable by visibly clear weld beads (boxed). clear visibility is obvious for weld region, base material as well as the heat-affected zone (haz) on the failed surfaces (fig. 3 (a, b and c)). a prominent secondary crack spanning across the whole fracture surface and almost at boundary hazra, m. and singh, a. k. (2023): international journal of engineering materials and manufacture, 8(3), 51-66 53 (fusion line) between the weld region and the rest of the cross-section (consisting of haz and base material) is seen (fig. 3 (b and c)). also, the mating failed surface reveals some small secondary cracks at the welds close to the boundaries of weld and haz in two perpendicular sides (in 2-dimension) of the failed component (fig. 3g). these cracks are along the weld-haz boundary at one side weld as well. henceforth, weld regions with bigger and smaller dimensions at two perpendicular directions are referred as longitudinal and transverse welds, respectively. the counterpart of the fracture surface presented in fig. 3a is shown in fig. 3h. this is a magnified view of high resolution of the portion presented in fig. 3b. here, one may notice the disparity between weld thicknesses in longitudinal and transverse welds. 3.2 fractography fractographs are presented in figs. 4-7 along with eds analyses. intergranular fracture features have been found to be prevalent. fig. 4 displays low magnification image showing intergranularity of the fracture surfaces. figs. 4 and 5 (a, b and c) represent fracture features from haz (marked in fig. 3b). on the other hand, representation of weld fracture is in fig. 5d. summary of all the types of fracture features observed at various locations on the surface is presented in fig. 5. gas-hole and/or porosity have been observed occasionally (boxed region in fig. 5a). intergranular fracture features is quite noticeable along with shallow rubbing. deep secondary cracks along the intergranular channels have been observed (fig. 5 (c and d)). interestingly, this fracture feature also resembles the appearance of pores (fig. 5c). it is to be noted that the type of intergranularity differs in features presented in fig. 5(b and c) to fig.5d. signature of cleavage within the intergranular fractures has also been noticed occasionally (fig. 5 (c and d)). intergranularity in fracture is more vivid in a location presented in fig. 5d, in contrast to the rubbed intergranular fracture of the few other locations observed in fig. 5c. figure 2: photographs of the as-received broken towing arm fork and bent towing pin figure 3: photographs of fracture surfaces of towing arm fork end in various views failure investigation on failed towing arm of an aircraft: a case of improper material processing and failed repair welding 54 eds analysis on the location marked as 1 (fig. 5b) reveals the presence of al and o majorly (fig. 6). it basically reflects the composition of the tiny round particles present in that location. fractographs near the weld region (along one of the side welds) are shown in fig. 7. again, haz in this region reflects intergranular fracture, while fracture of the weld zone is completely cleavage type. however, intergranular channels are even quite visible within this cleaved surface. very prominent secondary crack has also been observed at the boundary or interface between the weld zone and haz. figure 4: low magnification sem image of fracture surface figure 5: summarized view of the various types of fractures observed in the present failure figure 6: eds analysis pattern taken on location 1 (fig. 5b) hazra, m. and singh, a. k. (2023): international journal of engineering materials and manufacture, 8(3), 51-66 55 figure 7: fractographs near the weld region figure 8: cold mount containing towing arm fractured end along with location of the sample in main fractured piece 3.3 metallography towing arm fork (henceforth, it will be referred to as towing arm only) fractured section mounted in cold mount along with the schematic view of the location of the sample in main fractured piece is shown in fig. 8. existence of weld regions at two sides or edges is very clear. this image may be seen along with the as-received photographs presented in fig. 3(a, d-f), so as to have quite a good idea about the relative location of the weld, haz and base material within the fractured component. it has also been found to contain secondary cracks intermittently, as one such is marked in fig. 8b. it is to be noted that the crack trajectory and orientation of secondary cracks is exactly matching with the fracture path (main crack causing the fracture) (fig. 8). grain boundary precipitates and occasional cracking along these precipitates have been observed throughout the base as well as weld region in the un-etched condition (fig. 9). microstructure exhibits the presence of well revealed weld zone and base material after etching (fig. 10). weld region contains few dendrites with 90 angle between primary and secondary dendritic arms indicating that the weld material is cubic. interestingly, both the heat affected zone (haz) and remaining base material reveal the presence of equiaxed grains. heat-affected zone (haz) of a spread of 0.7 mm has been found and contains numerous cracks and grain fallouts (fig. 10). low magnification sem images are shown in fig. 11. ample of pores has been found in both the regions, i.e., weld as well as base material. amount of pores seems to have been more in weld than that in the base material. high magnification images of the weld region and base material are presented in fig. 12(a, b) and fig. 12(c-e), respectively. again, area fraction of the cracks is found to be more in case of weld region than that in the base material. failure investigation on failed towing arm of an aircraft: a case of improper material processing and failed repair welding 56 figure 9: optical microstructures of the failed towing arm end in un-etched condition figure 10: optical microstructures of the towing arm end in etched condition figure 11: sem micrographs of the towing arm end near the weld region hazra, m. and singh, a. k. (2023): international journal of engineering materials and manufacture, 8(3), 51-66 57 the eds analyses on various phases in the weld zone are presented in fig. 13. some precipitates appear to reside along the grain boundaries have been found to be rich in al, fe and mn. eutectic phases contain mainly al and si. overall composition of the weld region has been found to be rich in si and al (fig. 14). base material reveals the presence of grain boundaries rich in cu, fe and al (fig. 15). defect portions of the grain boundaries contain si, cu along with cl and o (fig. 16). overall base material composition shows the presence al along with small amount of cu (fig. 17). figure 12: high magnification sem images of the weld region and base material figure 13: eds analysis patterns on various phases in the weld zone se bse failure investigation on failed towing arm of an aircraft: a case of improper material processing and failed repair welding 58 figure 14: overall composition of the weld region as obtained by eds analysis figure 15: eds analysis on grain boundaries in base material figure 16: eds analysis of defects on grain boundaries in base material hazra, m. and singh, a. k. (2023): international journal of engineering materials and manufacture, 8(3), 51-66 59 fig. 18 exhibits sem micrographs of various locations of the towing arm end away from the failed region. reference image of sample extraction is displayed in fig. 18(a, b). presence of thick and continuous grain boundary precipitates are quite well revealed in the bse images (fig. 18(d, g)). several microstructural defects related to grain boundary cracking and grain pullout have been observed. fig. 19 exhibits high magnification image of the said region. two types of precipitates have been observed: (i) rich in cu and fe and (ii) rich in cu only. matrix composition has been found to be al containing  5 wt.% cu. microstructures of the towing pin are shown in fig. 20. it reveals the presence of alternate layer of greyish and whitish phases. three different locations marked as 1 (bright contrast), 2 (grey contrast) and 3 (overall composition) have been analyzed for composition. the eds analysis reveals the presence of fe only in all the three locations (fig. 21). figure 17: overall base material composition as obtained by eds analysis figure 18: sem micrographs of various locations of the towing arm end away from the failed region se bse se bse failure investigation on failed towing arm of an aircraft: a case of improper material processing and failed repair welding 60 figure 19: high magnification image along with eds analysis on regions (fig. 18) figure 20: optical (a, b) and sem micrographs (c-e) of towing pin hazra, m. and singh, a. k. (2023): international journal of engineering materials and manufacture, 8(3), 51-66 61 figure 21: eds analysis patterns on various marked locations 1, 2 and 3 (fig. 20) 3.5 chemical composition composition of towing arm as obtained by xrf is given in table 1. it shows cu as the major alloying element apart from the base material al. towing pin is found to contain only fe, while the eds analysis was taken from bulk of the sample at low magnification. compositions of the towing arm and towing pin as obtained from icp-oes analysis is presented in table 2. towing arm is found to contain cu and si as major alloying elements along with the base al. the analysed composition of towing arm is very close to the alloy b295 [5]. the ranges of the alloying elements in alloy b295 is included in table 2 for ready reference. towing pin consists of mn as the major alloying elements along with the base fe. contents of the trace elements (c and s) of the towing pin are shown in table 3. table 1: chemical compositions of failed towing arm and towing pin as obtained by xrf and eds techniques. component technique elements (wt.%) cu c si ti ni fe al towing arm xrf 4.65 0.35 0.15 0.009 0.132 bal. towing pin eds 2.2 97.8 table 2: chemical compositions of the failed towing arm and towing pin obtained by icp-oes technique component elements, wt% (standard deviation, wt%) fe ni cu si ti mn p al towing arm 0.17 (0.01) <0.00 2 4.3 (0.1) 1.03 (0.06) 0.13 (0.05) bal. b295 [5] max. 1.0 4.0-5.0 0.7-1.5 max.0.25 max.0.35 bal. towing pin bal. 0.58 (0.06) 0.82 (0.06) 0.037 (0.003) table 3: contents of trace elements (c and s) of the failed towing pin elements c s wt.% (standard deviation) 0.19 (0.01) 0.034 (0.002) failure investigation on failed towing arm of an aircraft: a case of improper material processing and failed repair welding 62 3.4 hardness vickers hardness values of towing arm sample taken at 5 kg load are found to be 88, 102, 108, 98, 92, with an average value of 98 hv. the weld region of towing arm possesses hardness values (taken at 500 g load) of 103.6, 99.1, 94.2, 104.2, with an average value of 100 hv. towing pin possessed hardness value of 230 hv. a micro hardness profile taken along a line across the weld interface and covering both base and weld materials has been shown in fig. 22. fig. 23 is the reference image for the indentations taken on the sample. here, one can notice that the weld material possesses an average hardness value of 102 hv, while the same for base material is 116 hv. it may be noted that these values are not in agreement with the bulk vickers hardness values of the two regions as mentioned above. hardness value of the interface (measured on the actual interfacial line) is found to be around 100 hv. the hardness value on the weld side ranges from 65 to 130 hv and gets stabilized at around 2.25 mm (2250 µm) from the interface. on the other hand, hardness value spanned from 115 hv to 125 hv on the base metal side and gets stabilized at around only 1.5 mm (1500 µm) from the interface. figure 22: micro hardness survey (in vickers scale) across the weld interface figure 23: reference image for the micro hardness survey across the weld interface 4 discussions 4.1 material of construction: identity and suitability microstructure, chemical composition and hardness evaluations of the as-received failed components indicate that the material of construction of towing arm is a cast al-cu-si alloy (closely matching with b295 alloy in t6 condition), while that of the towing pin is a low carbon (mild) steel [5, 6]. microstructure of the base material consists of α-al (with cu) along with grain boundary precipitates rich in al, fe and cu and closely matching with al2fecu type. the material contains defects such as pores and grain fall outs etc. quite extensively throughout its microstructure. the choice of the material composition and (casting) process route appear to be usual for the fabrication of towing arm wherein requirement of high strength, appreciable amount of ductility at room and elevated temperatures, sufficient corrosion resistance along with the involvement of extensive wear and tear is there in service [5-10]. hazra, m. and singh, a. k. (2023): international journal of engineering materials and manufacture, 8(3), 51-66 63 4.2 repair welding: its presence, need and impact upon the present system there are well-defined weld regions around the circumference of the fracture surface of towing arm. this is supported by the visual examinations as well as observation under sem. overall compositions of the base and weld materials as obtained from the eds analysis reflects the use of an al-si base filler metal in the welding process [5, 7, 8, 11-13]. similar level of hardness values along with gross similarity in microstructure between base and weld materials in the failed component indicate that the t6 heat treatment has been given to the component after welding. it seems that the repair welding has been carried out to refurbish prior localized failed and detached areas (fig. 3a). however, one must notice that the inherent defects in the base material in present case are the cracks along the grain boundary precipitates in addition to the pores and grain fallouts. thus, the avoidance of recurrence of such failure by repair welding is not possible, unless it changes the local thermal and/or chemical history to the desired extent [13-17]. intended microstructure resulting from this proposed change in local thermal and/or chemical history may find usefulness in such case. however, no such desired changes have been observed in present case, after the t6 heat treatment given to the whole assembly (base material + weld). interestingly, weld material has been found to contain more defects in terms of pores and cracks than the base. therefore, adoption of the method of repair welding does not seem to suit the purpose of mitigating the existing defects in base material, also assuming that some of those defects have been responsible for the failure. the grain boundary cracks along al-cu-fe rich precipitates have been found in partially melted zone (pmz) of heat affected zone (haz) of the base material, similar to that is observed in locations away from the weld area (i.e. pure base material). introduction of welding has come up with problem of more frequent occurrence of cracking in the heat-affected zone (haz) of the base material than that at away from it (i.e. pure base material). grain boundary rich in al-fe-mn precipitates and frequent cracking along the grain boundaries has been observed in weld regions both in longitudinal as well as transverse welds. thus, in the post-weld condition and during service of the towing arm, cracks seem to have been present along al-cu-fe and al-fe-mn-rich grain boundaries, respectively at the haz and weld regions. 4.3 various weld crack types there may be usually two types of cracking in aluminium welds – (i) hydrogen induced cracking (hic) and/or stress corrosion cracking (scc) and (ii) hot cracking [11,13,18,19]. in the present scenario, based on fractographic evidence and also the background information, possibility of hic as well as scc is zilch [13, 19]. thus, the existing all the types of cracks are basically hot cracks. this is also well supported by the zig-zag crack paths (representative of intergranular cracking) and distinctive fractographs typical of hot cracking [13,18]. now, broadly the four factors are influencing hot cracking in aluminium welds: (i) chemistry of base material, (ii) chemistry of filler metal, (iii) thermal stress (arising out of shrinkage during solidification) and (iv) mechanical stress (due to joint configuration/restraint) [20-23]. nonetheless, one has control over the factors (ii), (iii) (even (iii) is somewhat dependent on (ii)) and (iv)), once chemistry of the base material is fixed by the user. thus, chemistry of the filler material along with the mixture (base + filler material) as well as joint design may be monitored. the present (hot) crack type includes both solidification as well as liquation cracking. the longitudinal crack of importance seen in the weld region (close to the fusion line) on the primary fracture plane and spanning the whole length is a prime example of solidification crack (marked as secondary crack in fig. 3). physical attributes of the crack such as high depth, large length and three-dimensional shape indicate it to be the major culprit of the present failure. in other words, the present failure has initiated with this deep and lengthy discontinuity. similar types of solidification cracks are also seen at weld region (close to the fusion line) along the transverse welds (fig. 3g). small solidification crack well within the weld interior has been observed too occasionally (fig. 3g). orientation of these cracks has been found to be parallel to the above-mentioned longitudinal solidification crack. on the other hand, close examination of the pmz of haz in base material reveals the presence of numerous grain-boundary cracks (fig. 10). these are nothing but the liquation cracks. solidification and liquation cracks at respective weld and haz seem to have been often accompanied by the al-fe-mn and al-cufe rich grain boundary precipitates and their cracking. 4.4 selection of filler metal/alloy somewhat detailed input on welding filler material is worth mentioning here, as no information related to welding is available to the user as well as to the investigator. use of an al-si based is quite justifiable and subsequently discussed. the base al-cu-si (or more specifically, alcu) system has a wide range of crack sensitivity with respect to the cu content [11-13]. thus, the use of autogenous welding as well as the introduction of filler material of composition similar to the base material is highly risky. this is for the reason that doing so would result in the same or enhanced level of crack sensitivity to the system. widely popular filler metals of 4xxx (al-si based) and 5xxx (al-mg based) series are common choices in al welding. interestingly, the alloys of 4xxx series help in diluting the ill effect of cu locally in this regard. problem of shrinkage related thermal stresses is quite low in this case. on the other hand, filler materials of 5xxx series aggravate the cracking tendency by combined poorly effect of cu and mg on the coherency temperature range. failure investigation on failed towing arm of an aircraft: a case of improper material processing and failed repair welding 64 failure mechanism the sequence of failure schematic diagram consisting of a proposed sequence of events is shown in fig. 24. this (fig. 24a) is described with reference to the whole fracture surface presented in fig. 3h. longitudinal three-dimensional crack front spanning the whole length of the weld, close to fusion line is formed as a result of residual stresses coming out of joint constraint and/or heat treatment. this has disturbed the integrity of the joint and thus the component at the beginning of its service operation. this crack front has a curved surface area and extends from location at considerable depth to its opening up at the obtained fracture surface. this, later on, moves towards (both upward and downward) transverse directions (marked as inclined arrows) on the presently obtained plane of fracture surface. advanced stage of its propagation on the fracture plane is indicated by big inclined arrows. on the other hand, material becomes weakened by the presence of liquation cracks in haz (indicated by small straight arrows). thus, these liquation cracks indirectly have assisted in the present failure by easing the crack propagation stage. similarly, small (longitudinal) and moderately big (transverse) solidification cracks in transverse welds have assisted the current failure by weakening the microstructure. varying proportions of the final stages of failure are observed in transverse and longitudinal welds. weld section 1 is proposed to possess the least area fraction of the final stage of failure. this is due to the consumption of its greater amount by the above said three-dimensional solidification crack front. this is much commensurate with the visual examination (fig. 3) as well as with the fractographic evidence (figs. 5 and 7). figure 24: schematic diagram showing a proposed sequence of events leading to failure contribution of joint design, system and/or service stresses [13, 18, 20-23] there is absence of uniform weld thickness along the four sides of the failed surface, as mentioned earlier. this may have led to the unequal distribution of the system and/or service stresses and thus aggravating the early likelihood of the failure. surrounding fixtures during welding operation has an effect in the present case of weld cracking. solidification cracks have been observed at welds close to the fusion lines at both the longitudinal as well as the transverse sides. small solidification cracks aligned along the major axis (i.e., along the longitudinal side on the fracture plane) are also observed within the weld. it is quite clear from the results reported so far, that there has been a dominance of transverse stress over its longitudinal counterpart, as is supported by the frequent occurrence of (solidification) cracks of considerable depth and length, aligned along the longitudinal side. the proposed schematic also corroborates the same in the primary fracture plane which is formed by the movement of longitudinal solidification crack front towards the transverse direction only (fig. 24). it is also possible that the residual longitudinal and transverse stresses may be present. this may well come from the joint configuration and/or heat treatment of the component after welding. contribution from service stress failure extending towards the side (transverse) weld zones has exhibited cleavage type of brittle fracture during final stage of failure. this is purely a result of overload. the signature of other types of load is not observed. presence of cleavage during last stage of failure in both transverse as well as longitudinal weld zones (1, 1 / , 2 and 2 / in fig. 24) in spite of presence of weak intergranular regions (causing solidification cracking) indicate the involvement of rapid rate of loading due to very thin weld areas as compared to the remaining regions of the failed surface. microstructural contribution the inherent weakness of the parent material such as grain boundary cracks, pores, grain fall outs etc. has still been found to be present at failure location (weld zone, haz) as well as at location away from the failure (i.e. unaffected parent base material). thus, the inherent metallurgical weaknesses of the material still prevail and sometimes have hazra, m. and singh, a. k. (2023): international journal of engineering materials and manufacture, 8(3), 51-66 65 been aggravated subsequent to the welding (as manifested by more frequent occurrence of the above defects). thus, the t6 condition of the component material in parent state as well as in as-weld condition does not appear to suit for the present component. a three-dimensional weld solidification cracking has been found to be the primarily responsible for the creation of primary fracture plane in the present failure. this is also supported by the existence of secondary cracks in the weld zone having trajectory and orientation similar to the fracture path, as mentioned above. grain boundary cracks at the haz (often typified by grain fallout) arising out of the liquation cracking have assisted the present failure. solidification and liquation cracking have been found to be accompanied with grain-boundary precipitates rich in alcu-fe and al-fe-mn at the weld and haz, respectively. longitudinal weld side in the final failure reveals the presence of cleavage signs with occasional occurrence of cleaved facets within the moderately well revealed predominantly intergranular fracture (figs. 5 and 7). on the other hand, clear disclosure of the cleavage signature along with cleaved facets and faintly revealed two-dimensional intergranular channels have been noticed on the transverse weld side during the final stage of failure. thus, predominance of traits of cleavage fracture has been noticed especially along the transverse welds unlike along the longitudinal welds. interestingly, this phenomenon indicates that the al-fe-mn rich precipitates along the grain boundaries in weld region are not so week so as to lead a completely intergranular fracture (as in transverse welds), unless there is a co-existence of solidification cracks along with those precipitates (as in longitudinal welds). the longitudinal weld (weld section 1 in fig. 24) is thin enough during final stage of failure. this has resulted in nonrevelation of cleavage (type of signature of the overload) failure. this low thickness of the final zone of failure is due to the presence of the deep solidification crack of three-dimensional nature extending towards longitudinal weld periphery of the fracture surface at the component edge. thus, it is noteworthy from the ongoing discussion so far that precipitates located in base material and haz as well as rich in al-cu-fe are possibly relatively softer than those in weld zone and rich in al-fe-mn. this results in the more active participation of al-cu-fe along with the liquation cracking in aggravating the present failure than that of the al-fe-mn along with the solidification cracking phenomenon. 5 conclusions 5.1 towing arm 1. the present failure appears to have occurred by cracking of the weld region of the towing arm fork, as a result of introduction of weld repairing process as a method of healing of prior existing defects and/or failure at the location of weld area. 2. primary reason of the weld cracking and failure is the existence of solidification cracks at weld region close to the fusion line (haz-weld interface), while liquation cracks at partially melted zone (pmz) in heat affected zone (haz) has contributed to it secondarily by weakening the overall microstructure. 3. grain boundary precipitates of al-cu-fe type have facilitated development of the liquation cracking, while grain boundary precipitates of al-fe-mn type seem to have resisted the intergranular failure in solidification cracking, under the combined actions of welding induced stresses and service stresses. 4. improper material processing has led to the weakening of the microstructure of the base material by introduction of pores, grain fall out, thick al-cu-fe type of continuous grain-boundary precipitates and cracking. 5. weld repairing appears to be not successful at all on the al-cu-si system in the present condition; rather it has aggravated the previously existing improper material condition. 5.2 towing pin mild (low carbon) steel with low strength level could not bear with the load of the fractured assembly of the towing arm and thus got bent. its failure is of secondary nature and importance with respect to the failure of towing arm fork and the whole assembly. 6 recommendations 1. material related: pre-existing (casting related) defects such as porosity, grain fall-outs need to be optimized and to be guided by well-defined specification. 2. repair welding related: the repair welding, if unavoidable, should be practised with the following precautions. 3. process related: process should be monitored based on internationally popular standards for aeronautical applications such as ams 2175 and ams-a-21180 [11, 14-17, 19, 24, 25]. 4. minimization of residual stress and associated cracking: joint design and fixturing should be such that there would be insufficient amount of residual stresses both in longitudinal as well as transverse directions so as not to crack the weld afterwards. post weld heat treatment (pwht) may be employed to minimize the ill effect of residual stresses [18, 19, 20-23, 25]. failure investigation on failed towing arm of an aircraft: a case of improper material processing and failed repair welding 66 acknowledgements the authors would like to thank dr g. madhusudhan reddy, director, dmrl for his constant encouragement to work on the present field. also, funding from drdo is gratefully acknowledged. references 1. part 66 cat. b1 module 7 maintenance practices, volume 2, vilnius-2017, kazimieras simonavicius university, https://ksu.lt/wp-content/uploads/2017/06/m7-vol-2-selected-pages-maintenance-practices-2.pdf, accessed: 15.11.2021. 2. aircraft incident investigation, http://www.gpiaa.gov.pt/wwwbase/wwwinclude/ficheiro.aspx?access=1&id=9936, accessed: 15.11.2021. 3. wen, s., hui, c., fu-hai, l., analysis of boeing 737 aircraft towing accidents. engineering failure analysis, 2017(80), 234-240. 4. goglia., j., two-hour delay follows tow bar break at bos, https://www.aviationpros.com/gse/pushbackstractors-utility-vehicles/tow-bars/blog/10963025/twohour-delay-follows-tow-bar-break-at-bos, accessed: 20.09.2020. 5. astm b26/b26m – 09: standard specification for aluminium-alloy sand castings. 6. engineering handbook, box 232, exit 49, g. l. huyett expy, minneapolis, ks 67467. 7. pa, x. m., brody, h. d., morral, j. e., 2005. an assessment of thermodynamic data for the liquid phase in the al-rich corner of the al-cu-si system and its application to the solidification of a 319 alloy. j. phase equilibria diffus. 26, 225-233. 8. ponweiser, n., richter, k.w., 2012. new investigation of phase equilibria in the system al-cu-si. j. alloys compd. 512, 252-263. 9. kosak, w.e., cast aluminium rear subframe control arm articulations, u.s. patent 6648351, 2003. 10. kosak, w.e., cast aluminium vehicle subframe with tension/compression struts, u.s. patent 6742808, 2004. 11. http://www.alcotec.com/us/en/education/knowledge/techknowledge/trouble-shooting-for-aluminiumwelding.cfm, accessed: 15.11.2021. 12. rakesh, m., kumar, t.r. comparative study of different filler materials on aluminium alloys using tig welding, international journal of engineering research & technology (ijert) issn: 2278-0181, 8(8), 2019. 13. deekhunthod, r. weld quality in aluminium alloys, https://www.divaportal.org/smash/get/diva2:724173/fulltext01.pdf, accessed: 15.11.2021. 14. esposito, l., bertocco, a., cricrì, g., rosiello, v. welding-repair effect on f357-t6 aluminium castings: analysis of fatigue life, 2019, the international journal of advanced manufacturing technology 102(9-12). 15. using in-process welding to repair aluminium castings, https://www.castingsource.com/articles/using-processwelding-repair-aluminium-castings, accessed: 15.11.2021. 16. katsas, s., nikolaou, j., papadimitriou, g. d. microstructural changes accompanying repair welding in 5xxx aluminium alloys and their effect on the mechanical properties, 2006, materials and design 27(10), 968-975. 17. shankar, k., wu, w. effect of welding and weld repair on crack propagation behaviour in aluminium alloy 5083 plates, 2002, materials and design 23(2):201-208. 18. [18]http://www.adhocmarinedesigns.co.uk/wp-content/uploads/2012/07/proboat-june-july-2012-aluminiumwelds.pdf, last accessed on 15.11.2021. 19. davis, j.r., alloying: understanding the basics, asm international, 2001, 351-416, doi:10.1361/autb2001p351, accessed: 15.11.2021. 20. withers, p. j., residual stress and its role in failure, 2007, reports on progress in physics 70(12):2211, doi:10.1088/0034-4885/70/12/r04. 21. sun, j., hensel j., nitschke-pagel, t. and dilger, k., influence of restraint conditions on welding residual stresses in h-type cracking test specimens, materials 2019, 12, 2700; doi:10.3390/ma12172700. 22. luo, y., gu, w., peng, w., jin, q., qin, q., yi, c. a study on microstructure, residual stresses and stress corrosion cracking of repair welding on 304 stainless steel: part i-effects of heat input, materials 2020, 13, 2416; doi:10.3390/ma13102416. 23. de, a., deb roy, t., a perspective on residual stresses in welding, science and technology of welding and joining 2011 16(3), 204-208. 24. how to avoid cracking in aluminium alloys, https://www.esabna.com/us/en/education/blog/how-to-avoid-cracking-in-aluminium-alloys. cfm#:~:text=to%20counteract%20cracking%20problems%2c%20use,the%20hot%20cracking%20tempera ture%20range, accessed: 15.11.2021. 25. the repair of aluminium structures, http://www.alcotec.com/us/en/education/knowledge/techknowledge/the-repair-of-aluminium-structures.cfm, last accessed on 15.11.2021. http://www.gpiaa.gov.pt/wwwbase/wwwinclude/ficheiro.aspx?access=1&id=9936 https://www.sciencedirect.com/science/article/pii/s1350630716307105#! https://www.sciencedirect.com/science/article/pii/s1350630716307105#! https://www.sciencedirect.com/science/journal/13506307 https://www.aviationpros.com/gse/pushbacks-tractors-utility-vehicles/tow-bars/blog/10963025/twohour-delay-follows-tow-bar-break-at-bos https://www.aviationpros.com/gse/pushbacks-tractors-utility-vehicles/tow-bars/blog/10963025/twohour-delay-follows-tow-bar-break-at-bos http://www.alcotec.com/us/en/education/knowledge/techknowledge/trouble-shooting-for-aluminum-welding.cfm http://www.alcotec.com/us/en/education/knowledge/techknowledge/trouble-shooting-for-aluminum-welding.cfm https://www.diva-portal.org/smash/get/diva2:724173/fulltext01.pdf https://www.diva-portal.org/smash/get/diva2:724173/fulltext01.pdf javascript:; javascript:; javascript:; javascript:; https://www.researchgate.net/journal/the-international-journal-of-advanced-manufacturing-technology-1433-3015 https://www.castingsource.com/articles/using-process-welding-repair-aluminum-castings https://www.castingsource.com/articles/using-process-welding-repair-aluminum-castings https://www.researchgate.net/profile/stavros_katsas https://www.researchgate.net/scientific-contributions/77965126-j-nikolaou https://www.researchgate.net/profile/george_papadimitriou3 https://www.researchgate.net/journal/0261-3069_materials_and_design https://www.researchgate.net/journal/0261-3069_materials_and_design http://www.adhocmarinedesigns.co.uk/wp-content/uploads/2012/07/proboat-june-july-2012-aluminum-welds.pdf http://www.adhocmarinedesigns.co.uk/wp-content/uploads/2012/07/proboat-june-july-2012-aluminum-welds.pdf https://www.researchgate.net/profile/philip-withers https://www.researchgate.net/journal/reports-on-progress-in-physics-1361-6633 http://dx.doi.org/10.1088/0034-4885/70/12/r04 https://www.esabna.com/us/en/education/blog/how-to-avoid-cracking-in-aluminum-alloys.%20cfm#:~:text=to%20counteract%20cracking%20problems%2c%20use,the%20hot%20cracking%20temperature%20range https://www.esabna.com/us/en/education/blog/how-to-avoid-cracking-in-aluminum-alloys.%20cfm#:~:text=to%20counteract%20cracking%20problems%2c%20use,the%20hot%20cracking%20temperature%20range https://www.esabna.com/us/en/education/blog/how-to-avoid-cracking-in-aluminum-alloys.%20cfm#:~:text=to%20counteract%20cracking%20problems%2c%20use,the%20hot%20cracking%20temperature%20range http://www.alcotec.com/us/en/education/knowledge/techknowledge/the-repair-of-aluminum-structures.cfm international journal of engineering materials and manufacture (2018) 3(1) 41-54 https://doi.org/10.26776/ijemm.03.01.2018.05 m.a. kothari and w.n.p. hung texas a&m university e-mail: hung@tamu.edu reference: m.a. kothari and w.n.p. hung (2018). suppressing aluminum carbide in welding aluminum silicon carbide composite. international journal of engineering materials and manufacture, 3(1), 41-54. suppressing aluminum carbide in welding aluminum silicon carbide composite mitul a. kothari and wayne n.p. hung received: 12 march 2018 accepted: 17 march 2018 published: 30 march 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract weldability of aluminum-based metal matrix composite a359/sic/10p using gas tungsten arc welding and r356.0 filler material is investigated. the welding current, welding speed, and preheat temperature affect the weld quality significantly. finite element analysis is successfully applied to map the weldment temperature during preheating and welding. during mechanical testing of welded specimens, a crack propagates in the parent composite or in the weld, but not in the stronger zone between the weld and the parent material. the weld region contains reasonably uniform distribution of sic particles due to high viscosity of the molten weld and its fast cooling rate. proper control of heat input and addition of silicon-rich filler material hinder the interfacial reaction between aluminum matrix and the reinforcing sic particles, and successfully suppress the formation of harmful aluminum carbide flakes in the weld. the average tensile and flexural strengths of optimally welded specimens approach those of the parent composite while their ductility exceeds that of the parent material. keywords: gas tungsten arc welding, metal matrix composite, silicon carbide, cast aluminum, aluminum carbide, free energy of formation. 1 introduction advanced metal matrix composites (mmcs) combine the advantages of tough metal matrix and hard reinforcement to enhance their mechanical and/or physical properties. commercially available mmcs with excellent specific strength, high thermal conductivity, controllable thermal property, and good wear resistance have found their ways into many practical applications in bio-medical, electronics, aerospace, marine, machinery, sporting goods, metrology, and transportation. although fiber reinforced composites have been successfully produced, the particle reinforced mmcs are more popular since they behave isotropically and can be produced economically. raw mmcs can be manufactured by casting, bulk forming, or powder metallurgy techniques, but a full application of mmcs still depends on suitable processes that can repeatedly and economically shape a selected composite into useful components. studies of mmc's machinability show that traditional machining processes can be successfully performed with diamond cutting tools and mmcs can also be shaped by other nontraditional techniques. weldability of mmcs to themselves or to other engineering materials has been investigated by many researchers but there are remaining technical issues to be solved. in addition to common welding defects, the thermal-induced metallurgical defects such as agglomeration of the reinforcing particles and formation of aluminum carbide al4c3 in al-sic composites have been reported [1-3]. although low temperature joining processes such as adhesive bonding, brazing, or diffusion bonding can be utilized, the resulting low joining strength and high cost of diffusion bonding are still the concern for high volume production. joining of mmc components among varieties of shapes and sizes using a suitable fusion technique is still a promising alternative if the harmful aluminum carbide al4c3 byproduct can be avoided. the objectives of this research are to (i) utilize gas tungsten arc welding (gtaw) and a suitable filler material to study the weldability of a359 cast aluminum reinforced with sic particulates, and (ii) identify suitable process parameters to achieve high quality weld while suppressing the formation of aluminum carbide. 2 literature review the aluminum association of america recommends nomenclature for metal matrix composite as “matrix/reinforcement/volume fraction and reinforcement type.” the reinforcement type can be either particle (p), suppressing aluminum carbide in welding aluminum silicon carbide composite 42 whisker (w) or fiber (f). for example, the nomenclature a359/sic/10p in this study indicates the mmc containing a359 aluminum matrix and 10 volume % of sic particles as reinforcement. welding of mmcs may produce solidification defects, metallurgical defects, or process related defects. since most reinforcing ceramics have different physical and mechanical properties from the metallic matrix, such differences can lead to pronounced particle segregation effects when the matrix is in the molten state. below a certain solidification temperature, reinforcements can be pushed ahead of the solidification front, forming a non-uniform distribution of the reinforcement in the weld region thus weakening this area. when welding 6061-t6/al2o3, schwartz [2] found that adding a filler metal at unfavorable conditions could alter the matrix and cause a non-uniform distribution of the reinforcement particles in the weld region. the fluidity of the weld pool affects by the sic reinforced particles and how they are distributed. in the molten state the composite metal weld pool has higher viscosity than that of the matrix alone; therefore, it does not flow well. high viscosity also leads to a lower heat transfer by convection mechanism in the weld pool, which affects the resulting microstructures and stress distributions in the mmcs. this leads to an increasing numbers of porosity and weld-lines in the weld metal, as low fluidity may not be sufficient to ensure the filling of the entire weld pool region. solidification problems may result in unfavorable distribution of the reinforcements and non-uniform packing density of the reinforcement across the weld region [3]. 2.1. fusion welding of al-sic composites one major difficulty with most of the fusion welding processes for mmcs is that a prolonged contact between a molten metal matrix and reinforcement can lead to undesirable chemical reactions. under suitable conditions, liquid aluminum would react with sic reinforcement to precipitate the brittle and harmful aluminum carbide al4c3 while increasing the silicon content upon cooling of molten metal matrix. 3𝑆𝑖𝐶 + 4𝐴𝑙 ↔ 𝐴𝑙4𝐶3 + 3𝑆𝑖 (1) these needle-like al4c3 particles embrittle the weld and should be avoided. studies of the interfacial matrix/reinforcement reactions and fracture mechanisms of welded al/sic have revealed that the interfacial failure increases in welded metal due to the formation of al4c3. in addition, the resulting silicon product released from the decomposition of sic, stated in reaction (1), would also degrade the weld. such embrittlement is worsened in the presence of other intermetallic compounds of si, al, and fe. under these circumstances, urena et al. [4,5] reported that tensile strength of welded specimens was less than 50% of that from the base material. previous work on welding of 6061/sic/10p by chen et al. [6], revealed that gtaw tended to produce more al4c3 platelets than pulsed-gtaw. gopinathan et al. [7] studied co2 laser welding of a356/sic containing different amounts of volume fractions of sic particles. the authors calculated the thermal fields in the weld region and yielded the critical temperature and conditions for al4c3 formation. the critical temperature required for al4c3 formation was calculated and verified experimentally to be 827°c when the critical cooling rate was about 12,000 °k/sec. a cooling rate above this critical cooling rate tended to decrease the extent of the interface reaction. ellis [3] studied the thermodynamics in fusion welding of al/sic and predicted the critical temperature of 727°c for the formation of al4c3 plates. in the presence of moisture, the al4c3 may decompose, release methane gas, and increase the joint susceptibility to corrosion cracking while degrading the joint strength. pitting corrosion was observed in the heat affected zone (haz) of welded al-based mmcs, concluded by mathers [8]. another study by park and lucas [9] suggested that al4c3 can be formed around 650°c after prolonged contact between sic and molten aluminum, and the al4c3 can be disintegrated in less than 120 hours when exposed to a wet aqua-environment. other studies by dahotre et al. [10,11] on laser joining of a356/sic composites containing various volume fractions of sic particles showed that an increasing of energy densities would promote the sic particle dissolution and the formation of al4c3 particles. the duty cycle also had direct impact on how the weld microstructure would change. similarly, hung et al. [12] found that yag laser machining also formed the al4c3 precipitates in a359/sic/20p, and other defects such as thermal cracks, redistribution of sic, and voids. the latter was typical in cast and welded mmcs due to low fluidity of the molten matrix and non-uniform shrinkage upon solidification. fusion welding was also applied to weld mmcs with other monolithic materials. since welding of aluminum based mmc with sic reinforcement would form the harmful al4c3, some researchers apply alloying techniques to suppress the formation of al4c3. gomez et al. [13] used metal inert gas welding and selected al-si and al-mg as filler materials to join the 7005/al2o3/10p composite with 7020 aluminum. the joint strength reached 60% of that from the parent material and can be further improved to 95% by a post-weld heat treatment process. in laser welding study, wang et al. [14] sandwiched a 0.3 mm titanium foil between 6061/sic/25p specimens and exposed it to co2 laser with 3.2 kw/mm 2 power density. the energetically favorable titanium carbide tic and other compounds (ti5si3, al3ti, or ti2alc) were formed in the weld instead of al4c3. however, some aluminum carbide al4c3 and similar precipitates (al4sic4, and al4si2c5) were still formed in the heat affected zone away from the titanium rich weld zone. 2.2. solid state welding of al-si composites several solid state welding techniques have been explored to join mmcs. some researchers use friction stir welding technique to join mmc components or mmcs with other engineering alloys. a stirrer rotates, plunges into the joint junction to (i) plasticize the materials, (ii) forge the different materials together, and then (iii) form a joint at a temperature that is below melting temperature of the weldment. kannan et al. [15] friction welded 6061kothari and hung (2018): international journal of engineering materials and manufacture, 3(1), 41-54 43 t6/al2o3/10p onto 304 stainless steel. the stainless steel plate was covered with an electroplated silver layer of 16 µm thick. having the silver interlayer reduced ~3% number of fractured reinforcing particles in the weld. lee et al. [16] friction welded 6092/sic/17.5p composites and considered the effects of axial force, rotation speed, tool feed rate, lead angle, and plunge depth as process variables. excessive abrasive wear of the stirrer was recognized, and a suitable coated stirrer was sought; an inexpensive boron carbide coating was tried unsuccessfully despite of its inherent low coefficient of friction. the optimally welded composite had tensile strength of 300 mpa (43.5 ksi) which was 65% of the parent material strength. after a post-weld solution heat treating and aging to the t6 condition, the joint strength reached up to 426 mpa (61.9 ksi) which is 93% of the parent material’s strength. friction welding, however, produced a soft weld with hardness of 40 rb compared to 80 rb of the parent material. recognizing wear of a stirrer was one of the major drawbacks of friction stir welding for mmcs, prater [17] proposed to monitor stirrer wear using the current from the stirrer motor and found that the stirrer wear was proportional to stirrer rotational speed and welding distance, but it was inversely proportional to the stirrer feed rate. zhou et al. [18] also studied friction stir welding of 6061/al2o3/10p and 304 stainless steel by varying the rotational speed, pressure, and welding time. they reported lots of broken particles at the joint, reduced particle spacing in the weld, and delaminated matrix/reinforcement interfaces that led to final weld fracture in a notched tensile specimen. when comparing against relevant tensile strengths (517 mpa for 304 stainless steel, 310 mpa for 6061 and 338 mpa for the parent mmc), the tested joint strength were in the range 225-337 mpa with is 66-99% of the strength for the parent mmc. bozkurt [19] friction stir welded 2174/sic/25p and concluded that the rotational speed of a stirrer had higher influence to the weld quality than the stirrer feed rate. the resulting weld strengths were 263-366 mpa (58-80%) as compared to 454 mpa of the parent composite. jayaraman et al. [20] experimentally found that the maximum joint strength of friction stir welded cast lm6 a413 was 165 mpa, which was 57% of the tensile strength tensile (290 mpa) of the parent cast aluminum. spot friction welding to form local mmc joints was successfully performed by miller et al. [21]. these researchers added steel particles between 6111-t6 aluminum and then spot friction welded the sandwiches to achieve an increment of 25% higher for shear strength. although friction stir welding of aluminum mmcs with sic reinforcement can avoid formation of aluminum carbide due to its inherent low processing temperature, this process is constrained by specific geometries, limited to certain joint types, and damages to the reinforcement by breaking the particles and their surface coatings. 2.3. other joining techniques for al-si composites other researchers explored different joining techniques for aluminum-based mmcs. huang et al. [22] diffusion bonded 6063/sic/15p with al-si and al-cu powders between mmc specimens. the authors reported that the preferred al-si powders provided a better joint after heating the weldment to 580-605°c at 300 kpa in vacuum for 15-120 minutes. however, shear strength of the best joint reached only 42% (50 mpa) of the 120 mpa shear strength (241 mpa tensile strength) of the 6063-t6 matrix material. rosenberg et al. [23] patented another technique to weld mmc by using high power x-ray at the minimum power density of 10 4 w/cm 2 . this technique was more favorable than electron beam welding since the latter, with a couple of magnitudes higher in power density, would cause more welding defects due to superheating and evaporating of materials in the weld. among all joining techniques, fusion welding of al-si composites is still the most economical process if the silicon carbides can be avoided. the following sections describe the experiments and results from microstructural investigation and mechanical testing. 3. experiments butt joints of a359/sic/10p were welded with a lincoln electric square wave tig 175 pro in this study. an ø2.54 mm electrode containing 99.5% tungsten was ground to 90° tip cone angle for each weld. a series of factorial experiments were performed at high and low values to identify significant variables or their combinations. the variables include welding speed (120-250 mm/min), and ac welding current (90-110 a). argon shielding gas was utilized at a constant flow rate of 215 cm 3 /sec. the r356.0 filler rods with ø4.76 mm (ø3/16 inch) diameter were used for all experiments. optimal conditions were predicted from the design expert software version 6.0 based on these dominant variables. table 1 lists and compares the chemical compositions of the a359 aluminum matrix and the filler material r356.0. this filler material was chosen to closely match with the matrix material, although slightly lower silicon content was noticed. the aspect ratio of the reinforcing sic particles is 1.5:1 with the mean particle size of 12.8 ± 1.0 µm; 94% of population size >5 µm and 3% of population >25 µm. specimens of permanent-mold cast a359/sic/10p mmcs were obtained commercially and were milled to remove all outer layers and possible defects. pre-welding grooves of 90° angle and 2.5 mm depth were milled on all samples and later welded together with a filler material. other physical properties of the a359/sic/10p include 2710 kg/m 3 density, 0.450 cal/cm/s/°k thermal conductivity, 0.235 cal/g/°k specific heat, and 24.8 x 10 -6 /°k average coefficient of thermal expansion. table 2 lists mechanical properties of selected permanent-mold cast mmcs. the abaqus finite element software was used to calculate and map temperatures around and in the weld pool. the simulated temperatures were validated by comparing against actual readings from the thermocouples, located around a weld pool, during an actual pre-heating process. for simplicity, the bulk properties of a359 aluminum matrix were used in the calculation while ignoring the small 10% volume fraction of sic in the mmc. a tetrahedral suppressing aluminum carbide in welding aluminum silicon carbide composite 44 type of element was selected to mesh the fea model to suit the triangular geometry of the weld joint design. the mesh size was user-defined, wherein the mesh size was made finer along the welding surface and near the thermocouple positions for better accuracy. a gtaw torch was rigidly attached to the motorized victor mod 100 rail. a steel ruler and stop watch were used to calibrate the rail speed (welding speed) in both forward and backward directions. to evaluate the weld quality, vicker microhardness was measured with a buehler micromet 2 digital microhardness tester by loading a vicker diamond indenter at 25 gf load for 10 seconds and aiming in the matrix while avoiding colliding of the small indenter tip on a sic reinforcement. the united sfm 30 universal tester was utilized for bending and tensile tests. a four point bending specimen (30 x 15 x 125 mm) was bent to crack open a weld in tensile mode following the asme sec ix qw-462.3 testing standard. a tensile specimen (5 x 15 x 125 mm) was designed to minimize machining-induced defects after welding. three slots were sawed on a pre-welded sample: the central slot would force a crack to propagate through the butt weld, and the other two slots were to streamline the line of force in the specimen gauge length (fig. 1a). preheating in the neighborhood of a weld was required for temperature control. the entire weldment was first preheated to 150°c on a hot plate before welding, transferred onto a welding fixture, and preheated again with the gtaw torch along lines on left and right of a welding groove. a grooved mmc specimen with three embedded thermocouples was fabricated. three type-k thermocouples were attached to drilled holes below the preheat area, and near the v-notch (figs. 1b and 2). the temperature data logger, datapaq reflowpaq 2000 model rp0061, was used for acquiring temperature data from the thermocouples. the gtaw torch preheating was performed at 90 a of ac current and 4 mm torch length. the preheating sequence and welding steps were summarized in table 3. metallographic samples were prepared by first sectioning the weld beads perpendicularly to the welding direction, epoxy mounting with the buehler simplimet 2 press, following by hand grinding, polishing, and then etching for microstructural study. hand grinding with 240, 320, 400, and 600 grit abrasive papers were performed sequentially in flowing water. the samples were rinsed with clean water after each step to remove possible abrasive particles and chips, blown dried with dry compressed air before proceeding to the next step. table 1: compositions of r356.0 filler material [24] and a359 aluminum matrix [25]. si fe cu mg zn ti mn others al a359 8.50 0.20 0.20 0.25-0.45 0.10 0.20 0.10 0.15 remain r356.0 6.5-7.5 0.20 0.20 0.25-0.45 0.10 0.20 0.10 0.15 remain table 2: mechanical properties of permanent-mold cast al-sic mmcs [25]. material tensile strength (mpa) yield strength (mpa) elongation (%) elastic modulus (gpa) rockwell hardness, hb a356-t6 255-276 200 6.0 75.2 55 a359/sic/10p-t6 310-338 283-303 1.2 86.2 73 a359/sic/20p-t71 262 214 1.9 98.6 a359/sic/20p-o 221 165 2.8 98.6 table 3: preheating and welding sequences step process duration (sec) cumulative time (sec) 1 preheat to 150°c on a hot plate 1800 1800 2 preheat with gtaw torch above the left thermocouple, 5 passes @19 sec/pass 95 1800+95 3 idle 15 1800+110 4 preheat with gtaw torch above the right thermocouple, 2 passes @17.5 sec/pass 35 1800+145 5 idle 20 1800+165 6 weld with gtaw torch along the 90° groove 30 1800+195 7 cool in air 300 1800+495 kothari and hung (2018): international journal of engineering materials and manufacture, 3(1), 41-54 45 figure 1a: modified tensile specimen with three sawed slots. all dimensions are in millimeters. figure 1b: setup for temperature test. three thermocouples are located at left (l), right (r) and below the center (c) of a weld. all dimensions are in millimeters. figure 2: welding temperature measurement with (a) gtaw gun, (b) butt joined mmc samples, and (c) three thermocouples at left, right, and below a weld groove. after the final grinding, the samples were polished on a buehler vibromet 2 vibrating polisher using diamond pastes of 15 µm, 9 µm, 6 µm, and 1μm sequentially. next, they were cleaned with isopropyl alcohol between grinding/polishing steps in an ultrasonic cleaner to remove any remaining particles from previous steps. a specimen was etched in keller’s reagent composed of 2 ml hf (48%), 3 ml hcl, 5 ml hno3, and 190 ml h2o. the resulting microstructure was observed and measured on a measuring microscope olympus smt6 with 0.1 µm resolution. to identify silicon carbide in a359/sic mmc for comparison purpose, an mmc specimen was laser drilled (yag, 1 µm wavelength, 200 w power) to intentionally produce silicon carbide in the specimen. microstructure of the laser drilled specimen was prepared with similar procedures as for the welded specimen for comparison. 4. results and discussions since the gtaw torch was attached to the motorized victor mod rail, a chart is obtained to calibrate and quantify the welding speed. the actual rail speed is linearly proportional to the speed calibration dial on the rail. the measured speed is consistent and repeated when moving the rail forward or backward (fig. 3). 15 5 0 0 25 62.5 10 25 1.5 l c r 15 5 0 0 30 62.5 2 30 a c b suppressing aluminum carbide in welding aluminum silicon carbide composite 46 figure 3: calibration of rail speed (welding speed) for the victor mod 100 rail. 5.1. weld temperature estimation finite element simulation was used to estimate temperature at the weld and heat affected zones during welding. actual temperature during preheating was measured and compared with calculated data to verify the validity of the simulation. figures 4a, 4b, and 4c show how temperatures and their gradients change with time during the preheating sequences. although a specimen was initially heated to 150°c on a hot plate, its surface temperature dropped to nearly 100°c after transferring and fixturing a weldment onto a welding table at room temperature. additional preheating with a gtaw torch was necessary to maintain temperature before welding. when the surface above the left thermocouple was heated five times along a line 30 mm from the weld, the average temperatures of all three thermocouples rose linearly during the preheating time (0-95 sec). the temperature gradients then reduced when the heating torch was off while moving to the right location (95-110 sec), after which the temperatures rose again when preheating twice at the right location (110-145 sec). reasonable agreement was obtained between the measured temperatures and the resulting finite element data at three thermocouple locations (left, right, and below a weld). 0 500 1000 1500 0 10 20 30 40 50 60 r a il s p e e d ( m m /m in ) calibration dial average forward backward 100 200 300 400 0 20 40 60 80 100 120 140 t e m p e ra tu re ( ° c ) time (sec) left thermocouple fea 100 200 300 400 0 20 40 60 80 100 120 140 t e m p e ra tu re ( °c ) time (sec) center thermocouple fea a b kothari and hung (2018): international journal of engineering materials and manufacture, 3(1), 41-54 47 figure 4: temperature profiles at three thermocouple locations during preheating at (a) left, (b) center, and (c) right positions. gtaw preheating at 90a, 14.5v. surface heating above the left thermocouple (0-95 sec), switching to right location (95-110 sec), and then surface heating above the right thermocouple (110-145 sec). figure 5: finite element simulation of weld pool temperature. preheating to 150°c, left heating 0-95 sec, idle 95-110 sec, right heating 110-145 sec, idle 145-165 sec, welding 165-195 sec at 90 a, cooling after 195 sec. since the deviation of measured and predicted data was about ±50°c, it was assumed that the temperatures of all points in the weld, heat affected zone, and surrounding area could be predicted by finite element simulation to within ±50°c. figure 5 shows the simulated temperature at the weld pool during preheating and welding. the maximum temperature at the weld pool was 776°c which was higher than both liquidus temperatures of 615°c (of the r356.0 aluminum filler rod), and 660°c (of the a359 aluminum matrix) [26, 27]. 5.2. mechanical tests since a tensile specimen was notched near the weld, the maximum stress obtained from a tensile test was corrected by multiplying with a stress concentration factor. a sawed square slot of 1.5 mm width was approximated as a round-ended slot with 0.75mm radius. the stress concentration factor kt was calculated from [28]: 𝐾𝑡 = 𝐶1 + 𝐶2 ( ℎ 𝐷 ) + 𝐶3 ( ℎ 𝐷 ) 2 + 𝐶2 ( ℎ 𝐷 ) 3 = 2.07 (2) where h : slot length = 10 mm d : specimen depth = 15 mm r : radius of the end slot = 0.75 mm 𝐶1 = 0.953 + 2.136√ ℎ 𝑟 − 0.005 ( ℎ 𝑟 ) (3) 𝐶2 = −3.255 − 6.281√ ℎ 𝑟 + 0.068 ( ℎ 𝑟 ) (4) 100 200 300 400 0 20 40 60 80 100 120 140 t e m p e ra tu re ( °c ) time (sec) right thermocouple fea 0 200 400 600 800 0 50 100 150 200 250 300 w e ld p o o l t e m p e ra tu re ( °c ) time (sec) 776°c maximum c suppressing aluminum carbide in welding aluminum silicon carbide composite 48 𝐶3 = 8.203 + 6.893√ ℎ 𝑟 + 0.064 ( ℎ 𝑟 ) (5) 𝐶4 = −4.851 − 2.793√ ℎ 𝑟 − 0.128 ( ℎ 𝑟 ) (6) all 12 samples and replicates, welded at 2 variables and 2 levels, were carefully fabricated and tested. tables 4 and 5 tabulate the tensile and four-point bending data from specimens welded at factorial test parameters. resulted of the factorial experiments were collected and analyzed, from which optimal welding parameters of 85 a of ac current, and 260 mm/min welding speed were selected for maximum tensile/bending strength. notice that the optimal conditions were selected slightly outside of the testing ranges of 90-110 a and 120-250 mm/min. table 4: factorial experiment. tensile test results with three replicates. run welding current (a) welding speed (mm/min) max tensile stress (mpa) relative tensile strength [weld/parent] (%) max elongation (%) relative ductility [weld/parent] (%) 1 a 110 120 138 57 2.6 60 b 140 58 3.71 85 c 191 79 4.7 107 2 a 110 250 155 64 3.5 80 b 166 69 4.6 105 c 218 90 5.2 119 3 a 90 120 174 72 4.35 100 b 203 84 4.98 114 c 218 90 5.4 123 4 a 90 250 196 81 4.45 102 b 205 85 4.98 114 c 223 92 5.5 126 parent mmc 242 100 4.38 100 table 5: factorial experiment. four point bending test results without replicate. run welding current (a) welding speed (mm/min) max bending stress (mpa) relative bending strength [weld/parent] (%) maximum bending strain (%) relative bending strain [weld/parent] (%) 1 110 120 199 80 2.39 290 2 110 250 210 85 1.06 129 3 90 120 296 100 1.36 165 4 90 250 294 100 2.84 345 parent mmc 248 100 0.822 100 table 6: tensile test data for three replicates at optimal welding conditions. preheating following by welding at 85 a ac, 260 mm/min. replicate max tensile stress (mpa) relative tensile strength [weld/parent] (%) max elongation (%) relative ductility [weld/parent] (%) 1 199 82 6.0 137 2 202 83 5.2 118 3 217 90 7.0 160 average 206 85 6.07 138 parent mmc 242 100 4.38 100 kothari and hung (2018): international journal of engineering materials and manufacture, 3(1), 41-54 49 table 7: four-point bending test data for three replicates at optimal welding conditions. preheating following by welding at 85a ac, 260 mm/min. replicate max bending stress (mpa) relative bending strength [weld/parent] (%) max bending strain (%) relative bending strain [weld/parent] (%) 1 244 100 1.1 133 2 268 108 1.27 155 3 278 112 1.5 182 average 263 106 1.29 156 parent mmc 248 100 0.822 100 when welding at optimal conditions, the relative tensile strength and bending strength of the welded samples were 85% and 106% of those for the parent mmc (table 6). the relative tensile ductility and relative bending strain were 138% 156% of those for and the parent mmc (table 7). ductility of both the tensile and bending specimens was experimentally measured to be higher than those of the parent mmc. the enhanced ductility was contributed by:  addition of the soft and ductile al-si filler material in the weld,  minimizing sic particles redistribution and agglomeration in the weld, and  lack of brittle aluminum carbide in the weld. thermal energy from the 85 a welding current melted both the filler material and the aluminum matrix, but the resulting weld pool cooled down rapidly due to the relatively fast welding speed of 260 mm/min and the high thermal conductivity of the surrounding aluminum-based mmc. finite element results showed the time window of about 15 seconds for a weld to melt and re-solidify again. during such short period, the sic particles would not have sufficient time to redistribute themselves in a viscous melt, therefore, minimizing the chance for particle agglomeration and improving mechanical strength at the weld joint. 5.3. weld microstructure study of weld microstructure complemented the mechanical test results. figures 5 and 6 illustrate typical microstructures of weld samples after tensile and bending tests, respectively. the weld zone and parent mmc were clearly distinguished after etching. the center of a weld zone contained more filler material and less reinforcement, while the sic particles were uniformly distributed away from the weld center. a crack propagated through the weaker weld zone in the center rather than through the stronger weld zone between the weld and parent mmc. figures 7 and 8 compare the microstructures of the parent mmc and that at the weld zone of a typical welded specimen. the distribution of sic particles in eutectic zones was similar in both cases, and there were isolated voids in both the welded zone and in the cast mmc. prolong exposure of sic to heated aluminum in thermodynamically favorable conditions would decompose the sic to form a brittle and needle-like aluminum carbides al4c3 according to the reaction (1). as expected and shown in fig. 9, laser drilling of a359/sic at high power density (i) melted the aluminum matrix and maintained a high temperature due to sequential laser pulses applying at the same location, (ii) transformed sic into needle-like al4c3, and (iii) redistributed sic in the microstructure. other researchers also observed al4c3 in welded al/sic mmcs. the al4c3 needles, typically 20-50 µm long and easily seen under an optical microscope, were reported due to thermal decomposition of sic in an aluminum matrix in tungsten inert gas welding [6], co2 laser welding [7], and yag laser machining [12]. in this study, the needle-shape al4c3 was not observed with the optical microscope in any a359/sic/10p mmc samples welded at optimal conditions. lack of al4c3 in welded microstructure of the mmc could be due to: a) the reaction (1) did not happen and no al4c3 was formed, or b) the reaction (1) happened and al4c3 was formed, but then the reaction reversed due to additional silicon in the weld, or c) the reaction (1) happened and formed al4c3, but the resulting al4c3 needles were too small to be seen even at high magnification optical microscopy, or d) the reaction (1) happened and formed al4c3, but it was dissolved when contact with water during metallographic sample preparation. suppressing aluminum carbide in welding aluminum silicon carbide composite 50 figure 5: fractured surface and microstructure of typical tensile specimen. preheating and gtaw at 85 a ac, 260 mm/min; keller etching. figure 6: fractured surface and microstructure of typical four-point bending specimen. preheating and gtaw at 85 a ac, 260 mm/min; keller etching. although the aluminum carbide al4c3 can be affected by moisture, it was unlikely that the al4c3 was dissolved in water during sample preparation in this study. the metallurgical samples were hand ground and washed with water; a short exposure time (< 1 hour) of a sample in water during preparation was not sufficient for the intermetallic compound al4c3 to completely dissolve. the al4c3, however, can be disintegrated in water after a very long exposure time, says 120 hours [9]. the same metallographic sample preparation procedure after laser processing of similar mmcs, i.e., grinding and washing in water, revealed the 20-50 µm long al4c3 needles (fig. 9) but not in the samples welded at optimal conditions in this study (fig. 8). the relatively high weld strengths were contributed by strong adhesion at the weld zone and absence of the brittle al4c3. the formation of al4c3 depended on temperature, time, and power delivered to the weld [3,7,11]. alloying and thermal control were utilized to suppress the formation of harmful al4c3 in this study: alloying was formed by adding silicon from a filler rod –thus effectively reversed the reaction (1)– and lowering the welding temperature was achieved by welding using a low ac current at relatively fast welding speed. 1 mm 1 mm tensile loading tensile loading bending moment bending moment weld weld fractured surface fractured surface kothari and hung (2018): international journal of engineering materials and manufacture, 3(1), 41-54 51 figure 7: microstructure of as-cast a359/sic/10p. the typical sic particles (at arrow) are in eutectic zone of the cast mmc. figure 8: microstructure of the welded region of a359/sic/10p. notice the absence of needle-shape al4c3 near a sic particle (at arrow). preheating and gtaw at 85a ac, 260 mm/min. figure 9: microstructure of a359/sic after drilling with yag laser (a) laser cut area, (b) al4c3 rich area, (c) sic rich area, and (d) parent a359 aluminum mmc. notice the crack dividing zones (c) and (d). the needle-like al4c3 precipitates are still visible in zones (a) and (b) after ground, polished, and washed in water during sample preparation. 50 µm 20 µm 50 µm a b d c suppressing aluminum carbide in welding aluminum silicon carbide composite 52 aluminum reacts with sic to form aluminum carbide al4c3 and silicon si as predicted in reaction (1), an addition of silicon from the filler metal (into the right side of the reaction) would reverse the reaction and reduce the amount of al4c3. for a chemical reaction to happen, the free energy change of that reaction must be less than zero. ellis [3] proposed that the free energy for the reaction (1) can be calculated from: ∆𝐺 = 113900 − 12.06𝑇𝑙𝑛𝑇 + 8.92 × 10−3𝑇 2 + 7.53 × 10−4𝑇 −1 + 21.5𝑇 + 3𝑅𝑇𝑙𝑛(𝑎[𝑆𝑖]) (7) where a [si] : activity of silicon in aluminum liquid = 0.1 r : gas constant = 8.314 j/mol °k t : absolute temperature (°k) δg : change of reaction free energy (j/mol) the activity of si in liquid aluminum, a[si], was approximately 0.1 for the a356/sic mmcs [7]. the silicon content in a359 aluminum (8.5-9.5 wt% si) was slightly higher than that for a356 aluminum (6.5-7.5 wt% si) of the filler material r356.0 (table 2). since majority of the weld groove was filled with the filler material (figs. 5, 6), it was reasonable to approximate the silicon activity to be 0.1 for a356 aluminum when welding a359/si. substituting the values of the a [si] and gas constant into equation (7) to get: ∆𝐺 = 113900 − 12.06𝑇𝑙𝑛𝑇 + 8.92 × 10−3𝑇 2 + 7.53 × 10−4𝑇 −1 − 35.93𝑇 (8) the temperature t = 1031.6°k (758.6 ≈759°c) that made the right hand side of equation (8) zero can be solved numerically or graphically (fig. 10). thus, the reaction (1) only occurs when the free energy δg ≤ 0, or when the threshold temperature t ≥ 759°c. below this critical temperature, the thermodynamic driving force, as dictated by δg, is positive which would prevent the reaction (1) from happening, therefore suppressing the formation of al4c3. other researchers have reported the threshold temperatures for al4c3 formation were as low as 650°c [9], 727°c [3], or as high as 827°c [7]. figure 10: graphical solution of equation (8) in this study, the temperature of any point in the weld zone can be estimated by finite element method. the fea predicted the highest temperature at a node in the weld pool was approximately 776°c (1049°k) for a short duration of 5-7 seconds (fig. 5), after which the temperature dropped substantially. with the accuracy of ±50°c from fea, the maximum temperature range was therefore 776±50°c or 726-826°c which was in the proximity temperature of al4c3 formation (759°c). although the temperature criterion was at the border line, perhaps the short resident time of the welding pool (5-7 sec) did not allow sufficient time for the reaction (1) to happen. this was confirmed with high magnification optical microscopy examination when no al4c3 near a sic particle can be found in all optimally welded specimens (fig. 8). quality of the weld was also assessed with vicker microhardness measurement in the matrix across a weld. figure 11 plots the microhardness data of the matrix as a function of distance away from a weld center of three weld specimens. the microhardness near center of a weld was similar to that of the parent material, but it increased near the joint interface. a low hardness value at the weld center also indicated the absence of al4c3 precipitates in that area. the microhardness peaks, 3-5 mm away from the weld center and near the weld/parent material interface, perhaps were due to (i) smaller dendrite spacing due to different cooling rates, or (ii) a denser sic particle density (figs. 5 and 6). a higher sic particle density would form high dislocation density in a smaller dendrite by residual strains due to thermal mismatch between the aluminum matrix and ceramic reinforcement, which in turn increased the matrix hardness and matrix strength at this location. -60 -40 -20 0 20 40 60 1031.0 1031.2 1031.4 1031.6 1031.8 1032.0 c h a n g e o f f re e e n e rg y (j /m o l) temperature (°k) δg=0 kothari and hung (2018): international journal of engineering materials and manufacture, 3(1), 41-54 53 figure 11: vicker microhardness of the matrix across the weld of three specimens. each line is the moving average of two data points on a weld zone. microhardness test at 25 gf, 10 s. preheating and gtaw at 85 a ac, 260 mm/min welding speed. 6. conclusions and recommendations weldability of a359/sic/10p metal matrix composite using gas tungsten arc welding and r356.0 filler was determined by systematically identifying the influence of the welding variables on the weld quality. this study shows: 1. thermal control was necessary to obtain favorable distribution of sic particles in the weld pool. preheating of a weldment to 150°c following by gtaw torch surface preheating in the vicinity of the weld helped to control the temperature and viscosity at the weld. finite element analysis predicted the temperature in the vicinity of a weld to within ±50°c. 2. reasonable mechanical properties of the weldments were obtained. when welding at optimal conditions and adding additional silicon from filling rod, the relative tensile and bending strengths were 85% and 106% of those from the parent mmc, and the resulting ductility from tensile and bending tests were 138% and 156% compared to those from the parent material. 3. formation of harmful al4c3 during welding of the a359/sicp composite was suppressed. this was due to the addition of silicon content from the filler material, and favorable temperature control in the weld. the threshold temperature to form al4c3 in al-sic composite was calculated to be 759°c (1032°k). the maximum temperature in the weld pool was calculated to be in the range 726-826°c and remained for about 5-7 seconds. this short time duration and low weld temperature did not allow al4c3 to form in a weld. the absence of 20-50µm needle-like al4c3 was confirmed with microstructure and microhardness study. additional works could be done to confirm the results: a) scanning electron microscopy can be used at very high magnification to find out if the silicon carbide needles have started at the sic and aluminum interface after welding at optimal conditions. b) the dog-bone shaped tensile specimens with though thickness butt weld can be tested to verify the tensile properties of welded composites. c) transmission electron microscopy can be used to study the dislocation densities in the weld and heat affected zone to confirm the microhardness results. references [1] twi. joining of aluminium based metal matrix composites: initial study (2014). http://www.twi-global.com. [2] schwartz mm. joining of composite matrix materials, asm international, materials park, oh, 1994; 89-90. [3] ellis mbd. journal of material review (1996). 41: 41-58. [4] urena a, gomez de salazar jm, gil l, escalera md, and baldonedo jl. j microscopy (1999). 196: 124-136. [5] urena a, escalera md, and gil l. influence of interface reactions on fracture mechanism in tig arc-welded aluminum matrix composites, j composites science and technology (2000). 60: 613-622. [6] chen m, wu c, and gao j. (2002). welding of sic particle reinforced 6061 al matrix composites with pulsed tig, transactions of nonferrous metals society of china 12(5): 805-810. 50 75 100 125 150 0 2 4 6 8 10 v ic ke rs h a rd n e ss distance from center of weld (mm) sample 1 sample 2 sample 3 suppressing aluminum carbide in welding aluminum silicon carbide composite 54 [7] gopinathan s, mccay mh, and mccay td. (1993). continuous wave co2 laser welding of sic/a356 al metal matrix composites: an analytical estimate for formation of aluminum carbide, j processing of advanced materials 3:213-224. [8] mathers g. (1997). the welding of aluminum and its alloys, woodhead publishing limited, cambridge, uk; 2002. [9] park jk and lucas jp (1997). moisture effect on sicp/6061 al mmc: dissolution of interfacial al4c3, j scipta materialia 37(4) 511-516. [10] dahotre nb, mccay mh, mccay md, goinathan s, and sharp cm. (1992). laser joining of metal matrix composites, proceedings of machining of composites materials symposium, asme, chicago, illinois; 167-173. [11] dahotre nb, mccay td, and mccay mh. (1994). laser induced liquid phase reaction synthesis assisted joining of mmcs, j materials and manufacturing processes; 9(3): 447-466. [12] hung np, jana s, yang lj, and heng ch. (1995). laser drilling of cast metal matrix composites, proceedings, asme, new york, amd 208 md 59; 87-92. [13] gomez de salazar jm and barrena mi. (2003). dissimilar fusion welding of aa7020/mmc reinforced with al2o3 particles. microstructure and mechanical properties. j materials science & engineering a; a352: 162-168. [14] wang hm, chen yl, and yu lg. (2000). in-situ weld-alloying: laser beam welding of sicp /6061al mmc. j materials science & engineering a; a293: 1-6. [15] kannan p, balamurugan k, and thirunaavukkarasu k. (2012). reducing the particle fracture in dissimilar friction welds by introducing silver interlayer. j recent technology and engineering; 1:2, 159-160. [16] lee ja, carter rw, and ding j. (1999). friction stir welding for aluminum metal matrix composites. nasa tm1999-209876 report. [17] prater t. (2014). friction stir welding of metal matrix composites for use in aerospace structures. j acta astronautica 93; 336-373. [18] zhou y, li z, hu l, fuji a, and north th. mechanical properties of particulate mmc/aisi 304 friction joints; j iron and steel institute of japan; 1995; 35:10, 1315-1321. [19] bozkurt y, kentli a, uzun h, and salman s. (2012). experimental investigation and prediction of mechanical properties of friction stir welded aluminum metal matrix composite plates; j materials science issn 1392-1320; 18 (4): 336-340. [20] jayaramanm, sivasubramanian r, balasubramanian v. (2009). effect of process parameters on tensile strength of friction stir welded cast lm6 aluminium alloy joints. j material science and technology; 25:5, 655-664. [21] miller sf, arul sg, kruger gh, pan ty, and shih aj. (2011). effect of localized metal matrix composite formation on spot friction welding joint strength. j. engineering materials and technology; 133: 031009 1-8. [22] huang j, dong y, zhang j, wan y, and zhou g. (2005). reactive diffusion bonding of sicp/al composites by insert powder layers with eutectic composition. j. material science and technology; 21:5, 779-781. [23] rosenberg ra, goeppner ga, noonan jr, farrell wj, and ma q. (1999). high power x-ray welding of metalmatrix composites. us patent 5994660. [24] casti metals data book series. casti metals blue book welding filler metals (2002). asm international, materials park, oh, 252. [25] mc-21 inc.(2014). http://mmc-assess.tuwien.ac.at/mmc/cat/suppliers.html. [26] procast technologies (2014). http://www.procast.ca/alloy-information-aluminum-a356-0.php. [27] beck aluminum (2014). http://www.francismanufacturing.com/media/958/msds_359-alloy.pdf. [28] pilkey wd. (1994). formulas for stress, strain, and structural matrices; john wiley & sons inc. international journal of engineering materials and manufacture (2016) 1(1) 11-15 https://doi.org/10.26776/ijemm.01.01.2016.03 m. h. f. hazza and n. a. najwa department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: muataz@iium.edu.my reference: hazza, m. h. f and najwa, n. a. (2016). optimization of cutting parameters to minimize tooling cost in high speed turning of ss304 using coated carbide tool using genetic algorithm method. international journal of engineering materials and manufacture, 1(1), 11-15. optimization of cutting parameters to minimize tooling cost in high speed turning of ss304 using coated carbide tool using genetic algorithm method muataz hazza f. al hazza, nur amirah najwa bt mohmad bakhari received: 17 august 2016 accepted: 30 august 2016 published: 05 september 2016 publisher: deer hill publications © 2016 the author(s) creative commons: cc by 4.0 abstract high speed turning (hst) is an approach that can be used to increase the material removal rate (mrr) by higher cutting speed. increasing mrr will lead to shortening time to market. in contrast, increasing the cutting speed will lead to increasing the flank wear rate and then the tooling cost. however, the main factor that will justify the best level of cutting speed is the tooling cost which merges all in one understandable measurable factor for manufacturer. the aim of this paper is to determine experimentally the optimum cutting levels that minimize the tooling cost in machining aisi 304 as a work piece machined by a coated carbide tool using one of the non-conventional methods: genetic algorithm (ga). the experiments were designed using box behnken design (bbd) with three input factors: cutting speed, feeding speed and depth of cut and three machining levels. keywords: high speed turning, tooling cost, aisi 304, mrr 1 introduction the development of advanced manufacturing technology has been growing up rapidly. one of the advanced approaches is by increasing the machining speed to increase material removal rate and then shortening time to market, lowering cost, high accuracy and better quality. one approach for reducing the machining time in machining is by increasing the speed turning. high speed turning is difficult to define due to the fact of materials are varied for their hardness. therefore, high speed turning for one material may still be a low speed for another for example; the high speed for titanium is a low speed for aluminium [1]. however, these technologies should be justified by economic study. one of the most effective tools for economic study is by developing a cost model. in high speed turning the machining zone will be under high temperature and high sliding velocity. therefore, the wear progress will be difficult to estimate and predict. however, the wear rate of the cutting tool may give unacceptable outputs and that will result a low quality of surface roughness [2]. however, estimating the tool wear is highly valuable to estimate the tooling cost due to the relationship of tool life and material removal during the life of tool. however, tool insert may reaches its life and should be removed and changed before the tool insert edge cannot give the desired and accepted roughness. if the cutting tool reaches its life very fast then this will lead to increase the tooling cost becomes. therefore, the manufacturer needs to determine the best cutting levels that minimize the tooling cost. thus, estimating and then determining the best levels of the independent factors in machining becomes critical and important. determining the input level that can give the optimum values in machining process for one output response is very useful if the need for that response is important for one application but needs a validate and reliable mathematical model. in this research a regression empirical model will be developed and then the genetic algorithm method will be used to determine the minimum tooling cost of high speed turning of aisi 304 using coated carbide insert. optimization of cutting parameters to minimize tooling cost in high speed turning of ss304 … 12 2 methodology the methodology was three related integrated parts: firstly, the experimental work based on the theoretical study, then developing the cost model based on the experimental work. finally, using the genetic algorithm in order to determine the best cutting levels that will give the minimum tooling cost. box behnken design (bbd) has been used in this research to conduct the experimental work for three independent factors: cutting speed, feeding speed and depth of cut. three levels: –1, 0, and 1. however, bbd is easy to conduct in addition to the ability of sequentially. figure 1 concluded the activities and tasks need to be done in order to achieve the objective of the research in developing tooling cost and then determine the optimum cutting parameters to minimize the tooling cost in high speed turning for ss304 using coated carbide tool. figure 1: research methodology. 3 experiment procedure experimental works was conducted on cnc turning machine type power path 15 hs – high speed version (spindle asa a 2-5”) and the insert chosen for this study was a coated cemented carbide type (tnga 16 04 08 t1020) to turn work piece of aisi 304. under dry cutting conditions with cutting speed from 500 up to 700 m/ min, feed speed of 1000 to 2000 mm/min and depth of cut 0.1 to 0.3 mm. based on bbd with three centre points, fifteen run have been conducted. table 1 shows the machining levels. al hazza et al., (2016): international journal of engineering materials and manufacture, 1(1), 11-15 13 table 1: machining levels. max min cutting speed (m/min) 500 700 feeding speed (mm/min) 1000 2000 depth of cut (mm) 0.1 0.3 4 development of tooling cost model tooling cost model developed based and is limited in this research to the cost of tool holder and tool insert. the model was developed based on calculating the cost of removal one cubic centimetre. actually, tooling cost is inversely proportional with tool life and proportional with the machining time therefore, the tooling cost is calculated based on the work of [4-7]. the machining time components used in this research was based on machining time model developed by [6]. however, the final tooling cost was calculated based on the following equation [3]: however, all the experimental results is concluded in table 2. the results was analysed using the doe 6.0.8. the analysis of variance (anova) was conducted to develop an empirical model that can be used to estimate the tooling cost. analysis of variance (anova) is concluded in table 3 which shows significant with value of 0.002 and lacks of fit of 0.9574. therefore, the model can be used to navigate the design space. the following model has been used to determine the optimum cutting levels in the boundary of the design that can minimize the tooling cost. 5 genetic algorithm the genetic algorithm has been implemented using the developed model in the previous section in order to minimize the total tooling cost using three different independent decision variables: cutting speed, feed speed and depth of cut. table 4 concluded the objective functions decision variables, constrains. in the implementation, the chromosome values of each individual are generated randomly from the ranges of these values. however, the simulation has been repeated for four different runs, each for 1000 iterations. the optimum results was concluded in table 5. finally figure 2 shows the results for different runs that give the minimum tooling cost. the results show for different runs that after 100 iterations the values of the objective function become stable and only few points are giving results far from the final one. 3 3 ( ) ( / ) ( ) tc c rm cost rm cm mrv cm  table 2: result of experiment. no. of run cutting speed [vc] (m/min) feeding speed [vf] (mm/min) depth of cut [d] (mm) tooling cost (rm/cmᵌ ) 1 700.00 1500.00 0.30 0.051136 2 700.00 1500.00 0.10 0.273389 3 500.00 2000.00 0.20 0.157189 4 600.00 1500.00 0.20 0.053346 5 500.00 1500.00 0.10 0.193171 6 700.00 2000.00 0.20 0.267183 7 600.00 2000.00 0.10 0.100728 9 600.00 1000.00 0.10 0.096816 10 600.00 1500.00 0.20 0.177876 11 600.00 1500.00 0.20 0.592315 12 600.00 2000.00 0.30 0.078657 13 600.00 1000.00 0.30 0.588838 14 700.00 1000.00 0.20 0.176317 15 500.00 1000.00 0.20 0.160914 17 500.00 1500.00 0.30 0.173868 optimization of cutting parameters to minimize tooling cost in high speed turning of ss304 … 14 table 3: anova table for tooling cost. source sum of squares df mean square f value prob > f model 0.30711 9 0.034123 20.18702 0.0020 significant a 0.060565 1 0.060565 35.82974 0.0019 b 0.038284 1 0.038284 22.64872 0.0051 c 0.088878 1 0.088878 52.57925 0.0008 a2 0.016824 1 0.016824 9.952853 0.0252 b2 0.062186 1 0.062186 36.78888 0.0018 c2 0.008493 1 0.008493 5.024655 0.0751 ab 0.033702 1 0.033702 19.93782 0.0066 ac 0.138012 1 0.138012 81.64661 0.0003 bc 0.04324 1 0.04324 25.58052 0.0039 residual 0.008452 5 0.00169 lack of fit 6.82e-06 1 6.82e-06 0.003231 0.9574 not significant pure error 0.008445 4 0.002111 cor total 0.315562 14 tooling cost = +1.47020-9.44817e-003* cutting speed+4.16756e-003 * feed speed-9.82922* depth of cut+7.34688e-006* cutting speed2-6.96458e-007 * feed speed2 +5.22014* depth of cut22.80425e-006* cutting speed * feed speed+0.018575* cutting speed * depth of cut-3.17638e003* feed speed * depth of cut table 4: ga objectives, decision variables, constrains and parameters. objective function decision variables constrains minimize tooling cost cutting speed feeding speed depth of cut 500≥vc≥700 1000≥vc≥2000 0.1≥vc≥0.3 number of individuals in population= 20 number of generation= 1000 crossover rate = 35% mutation rate = 8% table 5: ga optimization results. run cutting speed feeding speed depth of cut tooling cost 1 500 2000 0.3 0.35779 2 500 1989 0.3 0.035988 3 500 1467 0.3 0.046178 4 500 1276 0.3 0.049914 al hazza et al., (2016): international journal of engineering materials and manufacture, 1(1), 11-15 15 run 1 run 2 run3 run4 figure 2: four different runs for 1000 iteration. 6 conclusions results concluded in table 5, show that the main flexible factor is the feeding speed which varied from 1276 to 2000 mm/min. in contrast, the cutting speed and depth of cut is constant with the values of 500 m/min and 0.3 mm. the results show that to minimize tooling cost, the cutting speed should be in the lowest level while the depth of cut should be in the maximum level. in addition the lowest tooling speed will be achieved in the highest feeding speed. references 1. muataz hazza f. al hazza, h., nabilah, m. yusof, b. m., najwa, n. a., eikhwan, m., khazairul, m., & taha, a. h. (2013). experimental study of flank wear in high speed turning of stainless steel aisi 304. journal of advanced science and engineering research, 3(2), 96-103. 2. ozel, t. and nadgir, a. (2002). predictions of flank wear by using back propagation neural network modeling when cutting hardened h-13 steel with chamfered and honed cbn tools. international journal of machine tools & manufacture, 42(2), 287–297. 3. adesta, e. y. t., al hazza, m., agusman, d., & sutjipto, a. g. e. (2012). development of tooling cost model for high speed hard turning. advanced materials research, 418, 1482-1485. 4. gara, s., bouzid, w., hbaieb, m., & amar, m. b. (2007). cutting speed optimization in high speed turning. international review in mechanical engineering, 1, 237-244. 5. gara, s., bouzid, w., ben amar, m. and hbaieb m. (2008). cost and time calculation in rough nc turning. international journal advanced manufacturing technology, 40(9-10), 971-981. 6. adesta, e. y. t., & al hazza, m. h. (2011). machining time simulation in high speed hard turning. advanced materials research, 264, 1102-1106. 7. al hazza, m. h. f., konneh, m., iqbal, m., taha, a. h., & hasan, m. h. (2015). using the desirability function as an effective tool in target costing model. advanced materials research, 1115, 126-129). 8. kalpakjian serope and steven r. schmid, 2010. manufacturing engineering technology. machining centers, machine tool structures and machining economics (pp 208). prentice hall. international journal of engineering materials and manufacture (2018) 3(4) 182-189 https://doi.org/10.26776/ijemm.03.04.2018.02 akshoy ranjan paul1 and firoz alam2 1department of applied mechanics motilal nehru national institute of technology allahabad allahabad, india. e-mail: arpaul2k@gmail.com 2school of aerospace, mechanical and manufacturing engineering rmit university, melbourne, australia e-mail: firoz.alam@rmit.edu.au reference: paul, a. r. and alam, f. (2018). compliance of boiler standards and industrial safety in indian subcontinent. international journal of engineering materials and manufacture, 3(4), 182-189. compliance of boiler standards and industrial safety in indian subcontinent akshoy ranjan paul and firoz alam received: 15 august 2018 accepted: 29 september 2018 published: 01 december 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract the economic development and industrialisation necessitate the use of boilers/pressure vessels. with the increase of boiler numbers and uses, the boiler explosion is rising. the non-compliance of standards and regulations, poor operation, maintenance, repair and safety-awareness are considered to be the integral part of boiler accidents. human error and poor maintenance are responsible for nearly 50% of the global boiler explosions. the fatalities due to boiler explosions are sky rocketing in the indian subcontinent. the paper has reviewed the global boiler explosions fatalities with a special emphasis on boiler accidents occurred in the indian subcontinent and suggested some remedial actions. keywords: boiler, pressure vessel, industrial safety, standards, indian subcontinent 1 introduction the tragic stories associated with the boiler/pressure vessel explosions are made frequently the major headlines in print and electronic media. nevertheless, many more such stories go unreported and overlooked. the boiler/pressure vessel explosions cause massive devastations regardless of their size or scope. the boiler explosions have significant consequences in developing nations as the explosions not only destroy property and human lives but also ruin livelihoods, and often the sole bread earners of poor families. a generation’s dream is lost through the tragedies. most tragedies could have been easily prevented if standards and guidelines were properly developed, understood, practised and enforced. boilers/pressure vessels are widely used in industries (power plants, chemical and fertilizer industries, paper mills, sugar mills, cotton mills, jute mills, rice mills, pharmaceuticals, textiles and garments industries) and homes and offices (water heating, central heating, cooking, and sanitation, etc.). usually, a pressure vessel with the steam pressure ranging from 0.07 to 2 mpa is called boiler, and above 2 mpa is called steam generator. as per australian standard as2593:2004 (reconfirmed 2016) a boiler is defined as “an arrangement of vessels and interconnecting parts, wherein steam or other vapour is generated, or water or other liquid is heated at a pressure above that of the atmosphere by the application of fire or the products of combustion or process, or by electrical or solar means. it also includes valves, gauges, fittings and controls directly associated with the boiler and, where consistent with the requirements of as2593:2004 (reconfirmed 2016), includes the boiler setting and associated equipment. it does not include fully flooded systems or pressurized systems where the water or other liquid is heated to a temperature lower than the normal atmospheric boiling temperature of the liquid” [1]. a typical boiler classification is shown in figure 1. boilers can be classified based on many parameters including boiler axis, passage, fabrication / manufacturing method, fuel source, working pressure and circulation method. the pressure vessel is usually made of steel (or alloy steel). the rapid uses of boilers began with the industrialisation and economic development. hence, there is an increase of boiler hazards (serious injuries, deaths and destruction of properties). today, boiler explosion is considered one of major threats to the industrial safety. it is significantly worst compliance of boiler standards and industrial safety in indian subcontinent 183 in developing countries especially in the indian subcontinent (india, bangladesh and pakistan). the primary objective of this paper is to highlight the alarming human deaths and injuries due to boiler explosions in the indian subcontinent and some remedial actions that can be undertaken to minimise these losses. in vaporised condition, the volume of water is more than 1,000 times larger than that of liquid form. this highly pressurised water steam can rapture the metal shell and/or disintegrate the poorly welded or rusted joint leading to a violent eruption of the pressurized steam causing death, injury and destruction of property (sometimes entire building along with its occupants). for example, a boiler explosion in r. b. groover shoe factory in brockton near boston at massachusetts, usa killed 58 people and injured over 150 people in 1905. the explosion was so intense that boiler parts ripped through the floors and levelled the four-story wooden building turning it into a crematorium [3]. the groover shoe factory before and after the boiler explosion is shown in figure 2. the groover disaster triggered the formulation of the us national boiler code/standard (by asme) governing the safe design, construction, operation and maintenance of boilers [3,4]. today most national and international standards are primarily based on asme boiler standards. 2 boiler explosions in indian subcontinent boiler accidents and loss of lives are not new in the indian subcontinent. the british india’s boiler regulation was the catapult of a tragic boiler explosion in kolkata in 1863. the bengal council passed a bill in 1864 to inspect the steam boilers in and around kolkata. other indian provinces later followed, and eventually the british established a uniform set of regulations in 1923 called ‘indian boilers act 1923’, which covers inspections, penalties and conditions for material procurement. boiler/pressure vessel explosions data is difficult to obtain as most industries keep boiler accident/incident data in house and unreported. this practice is associated with the non-compliance of national boiler standards, corruptions, and legal litigations [2,11]. as there is no reliable boiler explosion data on indian sub-continent is currently available in the public domain, the authors have used the boiler/pressure vessel incident reports’ database of the us occupational safety and health administration (osha), national board of boiler and pressure vessel inspectors (nbbpvi) and wisconsin boilers inspectors association (wbia) [5,6,7,11]. only incidents/accidents data applicable to the boiler/pressure vessel are used in this study. the osha and nbbpvi maintain us data while the wbia keeps a record on global events that reported in print/electronic media. the authors have analysed the global boiler/pressure vessel accident/incident reported data from 2012 to 2017. figure 1: boiler classifications, adapted from [2] boiler classification fire tube boilers water tube boilers shop-assembled boilers packaged boilers horizontal boilers vertical boilers inclined boilers based on boiler axis based on nature of fuel source used based on method of fabrication based on passage through boiler tubes natural circulation boilers high pressure boilers low pressure boilers solid fuel fired boilers oil fired boilers gas fired boilers forced circulation boilers based on working pressure based on circulation method paul and alam (2018): international journal of engineering materials and manufacture, 3(4), 182-189 184 figure 2: boiler explosion at groover shoe factory, adapted from [3,4,5]. (a) groover shoe factory before the boiler explosion on 20 march 1905, (b) groover shoe factory after the boiler explosion a recent tragic boiler explosion at multifabs garments factory at kasimpur (near gazipur) in bangladesh killed 13 people and seriously injured over 50 people on 3 july 2017 [8]. the intensity of the explosion was so severe that it destroyed the concrete-built garment building as shown in figure 3. most victims are poor workers including the boiler operator. two recent boiler explosions, one at a pharmaceutical unit of probace enterprises at dombivli in thane (india) on 26 may 2016 killed five and injured over 140 people (figure 4). the blast has destroyed two buildings and partially destroyed three more buildings. the blast intensity shattered the window panes of all buildings within 1.5 km radius [9]. the other explosion was at national thermal power company (ntpc)’s unchahar 550 mw thermal power plant in rae bareli, uttar pradesh, india on 1 november 2017. the explosion killed 32 people and critically injured 97 people [10]. the boiler destruction images are shown in figure 5. the number of global death and injury due to boiler/pressure vessel explosions is shown in figure 6. the numbers of deaths in the indian subcontinent (bangladesh, india and pakistan) are progressively higher compared to the rest of the world since 2012. for example, the death numbers in developed countries (e.g. usa, germany, uk, belgium and bulgaria) are only 20 compared to 248 deaths in bangladesh, india and pakistan over the same period. the boiler explosion death is 12.4 times higher in the indian subcontinent than the rest of the world. a total of 726 people were severely injured in a b compliance of boiler standards and industrial safety in indian subcontinent 185 bangladesh, india and pakistan as compared to only 366 people globally. again, the subcontinent boiler explosions caused nearly two times more severe injuries than the rest of the world. figure 7 also shows an increased trend of death and injury in the subcontinent since 2012. the number of catastrophic boiler explosions and fatalities are increasing progressively in india and bangladesh since 2012, which is shown in figure 7. it is alarming to note that over 76% global deaths due to boiler explosions occurred in the subcontinent. india topped the list with 34% of the global death, closely followed by bangladesh (21%) and pakistan (21%). the boiler explosion death in india is higher than bangladesh or pakistan as india’s registered boiler numbers are significantly larger compared to bangladesh and pakistan combined. india, bangladesh and pakistan are also responsible for over 66% global boiler explosion related human injuries compared to the rest of the world’s 34% (figure 8). india again leads with 33% followed by bangladesh (19%) and pakistan (14%). in 1973, there were over 20,000 industrial boilers including roughly 500 power boilers in india [14,17,20]. most boilers used in textile industries, followed by rice mills, distilleries, engineering and chemical industries. the percentage of shell boilers was largest being about 78%, water tube 14.5%, and package 7.5% [14]. it is believed to be the boilers number in india in 2018 is over 100,000. figure 3: boiler explosion at multifabs garments factory, kasimpur (near gazipur), bangladesh [8] figure 4: boiler explosion at probace enterprises pharmaceutical unit at dombivli, india [9] paul and alam (2018): international journal of engineering materials and manufacture, 3(4), 182-189 186 figure 5: boiler explosion at ntpc’s unchahar thermal power plant in rae bareli, uttar pradesh, india, adapted from [12, 13]. (a) boiler explosion at ntpc power plant, (b) fiery destruction after boiler explosion in bangladesh, there are over 10,000 registered boilers. additionally, there are over 2,000 boilers unregistered in bangladesh [15]. the boiler inspection department of bangladesh has only 7 inspectors and a chief inspector to inspect over 6,500 registered operational boilers (out of 10,000) throughout the country [16]. over 47 years ago in 1971, there were 700 registered boilers and four boiler inspectors and a chief boiler inspector. now after 47 years, the number of inspectors increased to 7 from 4 but boiler number has increased to over 10,000 [15]. the number ratio of boilers and boiler inspection is 1250 (in 2018) and 140 (in 1971). this figure clearly indicates why bangladesh has become one of the leading countries (2nd in south asia after india) for boiler explosion deaths and injuries. currently, each of seven boiler inspectors is assigned to inspect on average of 100 boilers per month. however, in reality, they can hardly inspect one-third of assigned boilers. as a result, the defective and registration-expired boilers continue to operate. there is no strict compliance of boiler standards for the material, design, and construction in bangladesh, despite locally manufactured boilers are increasingly filling gap of boiler needs along with imported in bangladesh. pakistan boiler act is based on indian boiler act 1923. like india, each province has boiler board who undertakes boiler registration, inspection and certification. at present, no data is available in public domain about the registered boiler numbers in pakistan. however, it is believed that the number should be at least 8,000 to 10,000. a b compliance of boiler standards and industrial safety in indian subcontinent 187 3 discussions the demand for industrial and domestic boilers has been increasing in all countries of asia led by china, india, japan, south korea, indonesia, bangladesh, vietnam, pakistan, philippines, thailand and malaysia. a recent study undertaken by global market insights has revealed that the global boiler market (industrial, utility, commercial and residential) is expected to be over us$50 billion by 2024 [17, 18, 19, 20, 21]. in the subcontinent, india has the largest boiler market with annual growth of 24% followed by bangladesh and pakistan. indian boiler market is mainly driven by energy and power industries [20]. the garment and textile sector are the main clientele for boilers in bangladesh. about 70% of the boiler requirements of the garment and textile sectors are met through domestic manufacturing units. poultry, feed mills, pharmaceuticals, food industries, auto rice mills, packaging, printing and leather industries are the major industries in bangladesh that require boilers. large boilers in bangladesh are mostly imported. with the sustained growth in garments and textile industries in bangladesh at an annual rate of 7%, there are large demands for boilers, which are expected to increase at a rate higher than the global demand of 4% [17]. after reviewing the boiler act 1923 and boiler regulations of india (1950), boiler regulations of bangladesh (1951 amended in 2007) and pakistan (1951), it is noted that all these countries have identical framework based on historical ‘indian boiler act 1923’. office of the chief inspector of boilers is the main regulatory body to look after the regulatory aspects of this sector in these countries. it also conducts registration of boilers, inspection and recommends for repairs, etc. the boiler boardas a high-powered technical body reviews/approves technical standards, designs, testing and inspection of boilers. trained manpower and equipment strength of the office are inadequate to operate effectively while ensuring safe operation and maintenance of boilers. 'the boiler act 1923’ is old and other regulatory frameworks are also outdated. the boiler rules/regulations and standards need continuous upgradation as new materials, technologies, control and monitoring systems are emerged. the boiler standards developed by asme (usa), standards australia (as), international organization for standardization (iso) and other developed countries are being reviewed and updated regularly. the boiler act 1923 needs to be thoroughly revised and updated as per asme (usa) and standards australia as these two standards are most up to date and incorporated all necessary aspects starting from design, manufacture, inspection & certification, operation, maintenance and repair. some major issues with the boiler are proper operation, maintenance and repair. it is specially so in the indian subcontinent. according to the us national fire protection association (nfpa), the boiler explosions in the us are caused by the operator error (47%), insufficient purge (39%), control failure (11%), and equipment failure (3%) [22]. no such data is available for the indian subcontinent. therefore, the awareness about the boiler explosion should be part of core values in operating a boiler. in addition to the full compliance of national standards and boiler regulations, the boiler user should: a) have qualified personnel on site to manage the boiler, b) run scheduled preparedness drills, and c) undertake regular boiler checks and services. figure 6: world-wide boiler explosion fatalities from 2012 to 2017, adapted from [5, 11] 0 20 40 60 80 100 120 140 death injured death injured death injured death injured death injured death injured 2012 2013 2014 2015 2016 2017 n um be r of p eo pl e bangladesh india pakistan rest of the world paul and alam (2018): international journal of engineering materials and manufacture, 3(4), 182-189 188 figure 7: deaths due to boiler explosions in indian subcontinent from 2012 to 2017 figure 8: injuries due to boiler explosions in indian subcontinent from 2012 to 2017 there appears to be a knowledge gap among industrial managers about boiler regulations and safety in the indian subcontinent. boilers rules in these countries cover features such as inspections and certification, registration, accident investigation, penalties etc. the rules particularly cover the holding of examinations and awarding competency certificates to boiler attendants and boiler engineers and even welders. those assigned to boilers need to be fully conversant with their operations to avoid exposing themselves and others to risk of accidents. however, these rules are often flaunted/ violated while implementing on the grass root levels. the public and private sectors using industrial, utility and commercial boilers must recognise that the function of these laws is not merely to regulate business and industrial activity, but to avoid accidents, injuries, illnesses and loss of property. boiler explosion death: 2012-2017 bangladesh (21%) india (34%) pakistan (21%) rest of the world (24%) boiler explosion injuries: 20122017 bangladesh (19%) india (33%) pakistan (14%) rest of the world (34%) compliance of boiler standards and industrial safety in indian subcontinent 189 4 conclusions based on the present study, the following remedies are suggested to avert boiler related accidents and health hazards in the indian subcontinent. 1. revise the boiler codes/standards and regulations in view of asme (usa) and standards australia (as). 2. create a pool of technical experts in boiler technology and operations to regulate the sector and maintain quality to avoid inherent risks. 3. strictly maintain boiler operation log program and maintenance log program (on daily, weekly, monthly, semi-annual and annual basis). 4. arrange regular training programs on safety aspects for managers, engineers/operators, workers, welders working with the boilers. 5. develop a national database for boiler registrations, renewal, explosions, causes of explosions and remedial actions. 6. provide resources (skilled manpower, finance and equipment) to the national boiler board to carry out vested duties and responsibilities as per national standard and/or international standards. acknowledgement the authors express their sincere gratitude and thanks to professor dr. m. a. rashid sarkar, department of mechanical engineering, bangladesh university of engineering and technology (buet), dhaka for sharing his knowledge on boiler operations in bangladesh with us. references 1. australian standard as2593: 2004 reconfirmed 2016, standards australia, sydney, australia 2. agarwal, s. and suhane, a. (2017), study of boiler maintenance for enhanced reliability of systems a review, materials today proceedings, vol. 4: 1541-1549. 3. canavan, d.a. (2005). remembering the 1905 groover shoe factory explosion, bulletin, 60 (3), 9-12. 4. varrasi, j. (2011). the try harnessing of steam, mechanical engineering magazine by asme, march, usa 5. wisconsin boilers inspectors association, http://thewbia.com/, accessed on 25 april 2018. 6. the national board of boiler and pressure vessel inspectors, http://www.nationalboard.org, accessed on 5 may 2018. 7. the us occupational safety and health administration, https://www.osha.gov/oshstats/, accessed on 10 august 2018. 8. the dhaka tribune, accessed on 25 july 2017. http://www.dhakatribune.com 9. the indian express, accessed on 27 may 2016. http://www.indianexpress.com 10. the hindu, 3 november 2017, http://www.thehindu.com/news/national/other-states/boiler-explodes-in-ntpcunchahar-plant/article19961812.ece, accessed on 30 january 2018. 11. paul, a. r. and alam, f. (2018), compliance of boiler standards and industrial safety in indian subcontinent, proceedings of the proceedings of the 1st international conference on mechanical engineering (incom18), paper no. 258, jadavpur university, kolkata, india, 4-6 january. 12. india today magazine, accessed on 20 march 2018. https://www.indiatoday.in/india/story/uttar-pradesh-boilerblast-rae-bareli-ntpc-boiler-unit-1077764-2017-11-01 13. india blooms news service (ibns), kolkata, india, accessed on 11 march 2018. https://www.indiablooms.com/news-details/n/35441/boiler-blast-at-ntpc-power-plant-in-up-kills-8.html 14. murgai, m.p. and chandra, r. (1990), boiler operations (progress in energy auditing and conservation, ed. sodha, m.s), new age international, new delhi, p. 341, isbn: 81-224-0285-2. 15. daily kaler kantha, accessed on 6 july 2017. http://www.kalerkantha.com 16. the office of the chief inspector of boilers, bangladesh, http://www.boiler.gov.bd/ accessed on 1 august 2017. 17. global market insights, accessed on 17 july 2017. https://www.gminsights.com/industry-analysis/boiler-market 18. bahadori, a. (2016). essentials of oil and gas utilities: process design, equipment, and operations, oxford: gulf professional publishing, uk. 19. tredgold, t. (1827). principle and construction of the steam engine, taylor & francis, london, uk. 20. business wire, accessed on 15 july 2017http://www.businesswire.com/news/ 21. tyagi, s. (2014), indian power boiler market: present & future, energetica india, 4-6. 22. the us national fire protection association, accessed on 5 may 2017. http://www.nfpa.org https://www.osha.gov/oshstats/ http://www.dhakatribune.com/ http://www.indianexpress.com/ https://www.indiatoday.in/india/story/uttar-pradesh-boiler-blast-rae-bareli-ntpc-boiler-unit-1077764-2017-11-01 https://www.indiatoday.in/india/story/uttar-pradesh-boiler-blast-rae-bareli-ntpc-boiler-unit-1077764-2017-11-01 https://www.indiablooms.com/news-details/n/35441/boiler-blast-at-ntpc-power-plant-in-up-kills-8.html application of digital cellular radio for mobile location estimation international journal of engineering materials and manufacture (2017) 2(3) 49-57 https://doi.org/10.26776/ijemm.02.03.2017.02 a. a. m. dalol, t. saleh department of mechatronics engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: tanveers@iium.edu.my reference: dalol, a. a. m. and saleh, t. (2017). concept of programmable fixture for 3-axis cnc. international journal of engineering materials and manufacture, 2(3), 49-57. concept of a programmable fixture for 3-axis cnc ahmed azmi mohamed dalol and tanveer saleh received: 22 march 2017 accepted: 08 june 2017 published: 15 september 2017 publisher: deer hill publications © 2017 the author(s) creative commons: cc by 4.0 abstract cnc machine is the one of the major reasons for industrial advancement in recent decades for its ability of producing accurate parts. the most common cnc machines are of 3-axis and adopted widely in the industrial sector. however, for producing more complicated parts 5-axis cnc machines are required. although the introduction of the 5-axis machine came after the 3-axis cnc machine has established itself and many manufacturers did not make the move toward the newer model and its high pricing compared to the 3-axis model did not help either. in this time the development of a fixture or a platform to help transfer the 3-axis to a 5-axis to some degree. this paper discusses the concept of a programmable fixture that gives 3-axis cnc machine the freedom to act in similar manner as the 5-axis. the paper describes the mechanism with some initial results of the testing. result showed that the platform moves in translation manner with an average error of 5.58 % and 7.303% average error for rotation movement. keywords: cnc, 3-axis, 5-axis, fixture, platform, kinematics, algorithm, graphical user interface (gui) 1 introduction numerical control nc is a method that is used in automation to manufacture highly precise components using commands that are stored in the memory of the machine. with the technology advancements computer has been introduce to the process and formed a computer numerical control. the modern cnc systems use computer aid design cad, noteworthy that the 3d software does not control the cnc it only generates the nc code. cnc machines are used in many manufacturing fields and it is capable of milling, turning, grinding and lathe and other functions to get an accurate product with very small margin of errors. a robot is defined as “a reprogrammable multifunctional manipulator designed to move material, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks” according to robot institute of america (ria). in 1959, the first commercially available robot appeared on the market [1]. robots can be classified using their geometric types to cartesian (ppp), cylindrical (rpp), spherical (rrp), scara (selective compliance assembly robot arm) (rrp), and articulated (rrr) [2]. the first parallel robot was patented by an american farmer called james e. gwinnett in the 1928 [3]. in 1947 a new parallel manipulator was invented and it became the most common or a robot. it was invented by dr. eric gough, who invented the octahedral hexapod in england. it was called the universal tire test machine as shown in figure 1. in the united kingdom dr. stewart presented six degrees of freedom flight simulator in 1966. it is referred as the stewart platform [5]. it consists a triangle moving platform, base and three extensible links. the links connects the platform to the base. the links connected to the base using hook’s joints. the stewart platform was a gate of a new designing era as many inventions were based on the idea of the platform. comparison between parallel and serial manipulators is presented in table 1 [7]. 2 system design the system is designed based on a parallel manipulator. the design of slider and ball-joint mechanism is kept. but with enhancement and modification for the dimensions of parts. the system was reversed engineered using cad software. the software that was used is solidworks. the complete assembly is shown in figure 2. the system is using 6 dc motors and aruino uno r3 as shown in electrical circuit in figure 3. concept of a programmable fixture for 3-axis cnc 50 table 1: comparison between parallel and serial manipulator factor/aspect parallel serial type of loop closed loop open loop end effectors platform gripper inertia low high stiffness high low direct kinematics complex simple inverse kinematics simple complex preferred application precise positioning gross motion figure 1: the tire test machine concept built by dr. eric gough [5] (a) (b) figure 2: 3d image of cmc system (a) cad model and (b) actual prototype the platform is using acrylonitrile butadiene styrene (abs) for 3d printing links and joints. the technical specifications of abs used in the research are listed in table 2 [8]. the specification of arduino uno r3 controller used in this platform is given in table 3 [9]. the servo motor will act as an actuator for the platform. the motor will provide movements which will affects the outcome of the position of the upper platform. the model of the platform used is gs-5515mg. the power source used for the manipulator is a lithium-ion polymer (lipo) battery with 2200 mah capacity. the details of the platform are given in table 4. dalol and salehi (2017): international journal of engineering materials and manufacture, 2(3), 49-57 51 figure 3: the electrical circuit of the system table 2: technical specifications for abs used in this research tensile modulus 1627 mpa tensile strength 22 mpa flexural strength 41 mpa flexural modulus 1834 mpa density 1.05 g/cm³ table 3: arduino uno r3 technical specifications microcontroller atmega328p operating voltage 5v input voltage (recommended) 7-12v input voltage (limit) 6-20v digital i/o pins 14 (of which 6 provide pwm output) pwm digital i/o pins 6 analog input pins 6 dc current per i/o pin 20 ma dc current for 3.3v pin 50 ma flash memory 32kb (atmega328p), 0.5 kb used by bootloader sram 2 kb (atmega328p) eeprom 1 kb (atmega328p) clock speed 16 mhz 3 system analysis this section discussed the mechanical design of the fixture and it showed that the limits of this structure in the aspects of load and size. it also analysed the parallel nature of the manipulator and developed the algorithms. the degree of freedom is calculated by using equation (1). 𝑀 = 6 (𝑛−𝑔−1) + σ𝑓𝑖𝑔𝑖 = 1 (1) where, m = mobility n = number of link of each legs + base + top g = number of joint of each legs fi = number of dof of each joint for each legs n = 1 + (3 x 3) = 10 g = (1 + 1 + 1 + 1) x 3 = 12 fi = (1 + 1 + 3 + 3) x 3 = 24 m = 6(10 − 12− 1) + 24 = 6 http://www.atmel.com/images/atmel-42735-8-bit-avr-microcontroller-atmega328-328p_datasheet.pdf concept of a programmable fixture for 3-axis cnc 52 table 4: platform specifications fixture type parallel controller arduino uno r3 type of joints linear/rotary material of fabrication abs movement generator servo motor gs-5515mg power source lipo battery 2200 ma with 6 volts maximum load for the structure 45 kg maximum load for the motors 15 kg mobility 6 translation x, y, z rotation x, y x-axis leg 2 and 3 y-axis leg 1 z-axis leg 1,2 and 3 rotation about x leg 1 rotation about y leg 2 and 3 the links maximum load can be found using equation (2-6) and taking the weakest link to be the maximum overall for the platform. from the analysis it was observed that the critical load for the weakest link was around 450 n. k= √(i/a) (2) the slenderness ratio= l/k (3) (l/k)_1= √(2πec/sy) (4) pcr=a[sy-(sy/2π l/k)^2 1/ce] (5) pcr= (cπ^2 e)/(l/k)^2 a (6) where, i = mass moment of inertia, k = radius of gyration, a = cross sectional area of the link, pcr = critical buckling load, sy = yield strength, and e = modulus of elasticity the platform is using the three legs to move. leg1 is along y-axis and leg2 and leg3 both acting along x-axis and yaxis as well (figure 1 and 2). all 3 legs act along z-axis. the leg as shown earlier can be divided into two parts upper leg and lower leg. the fixture is at original position [0 0 0 0 0 0] and no orientation when all links are retracted, as a result the movements in z-axis only happens in positive direction upward. further analysis is will show the platform parameters limits and discuss the positioning of the platform. the positon can be represented by the equation (7). p = [ x y z α β γ]t (7) the x, y and z are the translation movements and α,β and γ represents the rotation of the platform. the following equations are derived using inverse kinematics and interpolation: x= ((±15*θ)/180) +15 (8) where ± depends on the direction of the movements. y= ((d*θ)/180) + d (9) where, d= 4 if it is in positive direction and d=-16 if it is in negative direction z=((17*θ)/180 )+17 (10) the fixture need to rotate around x and y axis only. so the α and β are given by α=((q*θ)/180)±q (11) where, q=11 when going anticlockwise and -11 clockwise. q= -11 when going clockwise. dalol and salehi (2017): international journal of engineering materials and manufacture, 2(3), 49-57 53 β=((w*θ)/180)±w (12) where, w=3 when going anticlockwise and w=–12.5 when going clockwise 4 programming the coding was done using c++ and c sharp. the c sharp was needed to use with visual studio software to develop the graphical user interface (gui). the gui can be used in two ways. the first method is by adding the values one by one for each movement and save them. after saving the command “start” will initiate the platform movement. when the platform finishes, it returns to original position and waits for further commands. the second method is by uploading a text with pre-programmed instructions. after uploading the file, “start” button will initiate the platform and it will start moving. when the instructions finish the platform returns to original position. the details of these instructions are shown in figure 4. the logic of instruction of movement is shown in flow chart figure 5. (a) (b) figure 4: sample of the (a) coding and (b) gui for the cnc system concept of a programmable fixture for 3-axis cnc 54 figure 5: flow chart of movement instruction 5 testing the platform algorithms went through several testing and the test results are summarized in table 5. the platform make translation along the three axis x,y and z. the platform also can rotate around all three axes but the needed ones are around x axis and y axis. the rotation about z does not add any extra functionality to the cnc machine that the five different movements cannot achieve by themselves. for translation, a ruler with a right angle was used to measure the actual translation that accrues. for rotation a fixed bar, a ruler and a protractor were used. table 5: summary of platform algorithm test results parameter min max average absolute error translation along x in mm -15 15 0.44444 translation along y in mm -5 16 0.47222 translation along z in mm 0 17 0.40000 rotation about x in degrees -12.5 4 0.66667 rotation about y in degrees -11 11 0.52777 dalol and salehi (2017): international journal of engineering materials and manufacture, 2(3), 49-57 55 (a) (b) (c) figure 6: translation error for converted 5-axis cnc along (a) x axis, (b) y axis, and (c) z axis -0.2 0 0.2 0.4 0.6 0.8 1 1.2 -20 -15 -10 -5 0 5 10 15 20 e rr o r (m m ) movments (mm) translation along x run 1 run 2 run 3 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 -10 -5 0 5 10 15 20 e rr o r m m translation mm translation along y run 1 run 2 run 3 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 0 2 4 6 8 10 12 14 16 18 e rr o r m m translation mm translation along z run 1 run 2 run 3 concept of a programmable fixture for 3-axis cnc 56 (a) (b) figure 7: rotation error for converted 5-axis cnc about (a) x axis and (b) y axis 6 conclusion the paper presents a concept of converting 3-axis low cost cnc machine into a 5-axis cnc machine using a smart fixture. the smart fixture was designed using parallel kinematics and its feasibility was studied. the fixture was tested for positional accuracy in terms of translation and rotation. this research showed:  the coding was done using c++ and c sharp with visual studio software to develop the user friendly gui.  the movement accuracy is found to be in sub millimetre range.  it is possible to convert 3-axes cnc milling machine into 5-axes cnc milling machine acknowledgement authors would like thank international islamic university to provide research grant and laboratory facilities for conducting this research. 0 0.5 1 1.5 2 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 e rr o r (d e g re e s) command rotation (degrees) rotation about x run 1 run 2 run 3 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 -15 -10 -5 0 5 10 15 e rr o r in d g re e s rotation (degrees) rotation around y run 1 run 2 run 3 dalol and salehi (2017): international journal of engineering materials and manufacture, 2(3), 49-57 57 references [1] jazar, r. n. (2007). theory of applied robotics: kinematics, dynamics, and control. new york: springer. [2] pandilov, z. & dukovski, v. (2014). comparison of the characteristics between serial and parallel robots. acta tehnica corviniensis. [3] [gwinnett, 1931] tsai, l. (1999). robot analysis: the mechanics of serial and parallel manipulators. new york: wiley. [4] lenarc ̌ic ̌, j., & husty, m. l. (1998). advances in robot kinematics: analysis and control. dordrecht: kluwer academic. [5] stewart, d. (1966). a platform with six degrees of freedom: a new form of mechanical linkage which enables a platform to move simultaneously in all six degrees of freedom developed by elliott ‐automation. aircraft engineering and aerospace technology, 38(4), 30-35. [6] patel, y., & george, p. (2012). parallel manipulators applications. modern mechanical engineering, 57-64. [7] https://i.materialise.com/3d-printing-materials/abs/technical-specifications [8] https://www.arduino.cc/en/main/arduinoboarduno [9] budynas, r. g., nisbett, j. k., & shigley, j. e. (2011). shigley's mechanical engineering design. new york: mcgraw-hill. [10] xing, y., & wang, t. (2011). accuracy enhancement in manufacture of spiral bevel gear with multi-axis cnc machine tools by a new compensation method. international conference on consumer electronics, communications and networks. doi:10.1109/cecnet.2011.5768862 [11] gallardo, j., lesso, r., rico, j. m., & alici, g. (2011). the kinematics of modular spatial hyper-redundant manipulators formed from rps-type limbs. robotics and autonomous systems, 59 (1), 12-21. doi:10.1016/j.robot.2010.09.005 https://i.materialise.com/3d-printing-materials/abs/technical-specifications https://www.arduino.cc/en/main/arduinoboarduno international journal of engineering materials and manufacture (2021) 6(1) 50-59 https://doi.org/10.26776/ijemm.06.01.2021.05 shazzad hossain and mohammad zoynal abedin department of mechanical engineering dhaka university of engineering and technology gazipur 1707, bangladesh e-mail: abedin.mzoynal@duet.ac.bd reference: hossain s and abedin, m. z. (2021). effect of minimum quantity lubrication system for improving surface roughness in turning operation. international journal of engineering materials and manufacture, 6(1), 50-59. effect of minimum quantity lubrication system for improving surface roughness in turning operation shazzad hossain and mohammad zoynal abedin received: 21 october 2020 accepted: 29 december 2020 published: 30 january 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract due to increase in temperature at the cutting zone, the tool wear and surface roughness along with the non-uniform chip formation and the dimensional deviation of the job by using the conventional cutting fluid, the machining operation experts have directed their concentrations in order to achieve a smooth machining operation by using minimum quantity lubrication (mql). as a consequence, numerous efforts can be seen for not only having the optimum cutting parameters but also other parameters that enhance the product quality and the surface roughness. in this regard, relevant experimental and numerical data outcomes not only mql but also conventional cutting fluid (ccf) in the turning operation of 50hrc steel has been investigated experimentally. it is revealed that the surface roughness becomes optimal and significantly reduced for the condition of mql with that of dry and conventional flood. keywords: turning operation, ccf, mql, surface roughness, lathe machine. 1 introduction minimum quantity lubrication or mql, also known as "micro lubrication", is the new method of delivering metal cutting fluid to the chip-tool interface. using this method, a little fluid, when properly selected and applied, can make a substantial difference in how effectively a tool performs in the operation. the goal of any machining operation such as turning, milling, grinding, drilling, etc. is to reduce the machining costs by improving its quality and productivity. the machining operation is performed by using an extensive lubrication that helps not only to reduce the friction, heat and wear of cutting tools but also helps to ensure a smooth operation between the cutting tools and work pieces. in ancient time, the conventional cutting fluid (ccf) was seen to be highly used in various machining processes that would cause the tremendous health problems of employees as well as environmental pollutions. in addition, by using ccf, it may not be possible to achieve more working satisfactions due to its various reasons such as the recycling of its chips, degrading the quality of fluid and less heat absorbing capacity of the fluid and so on. also, the ccf is considered to be more effective at a lower cutting speed and it becomes ineffective at a higher cutting speed because the amount of generated heat is more and the coolant cannot reach the critical areas, hence the interface cannot be cooled easily. thus, the minimum quantity lubrication system comes out as another method that can be studied in details so as to reach the desired objectives and that may be considered to be an economical and environmentally compatible lubrication system in the machining operation. the mql system provides spray painting at high speed and high pressure to the cutting zone by the gun. it is supplied at a constant pressure around 2 to 6 bars. basically, a mixture of air and cutting fluid (soluble oils, semi synthetics, and synthetics) is applied onto the cutting zone. different papers published on mql in different types of machining process. mql is an advanced method which can perform the superior cutting operation where the temperature at the cutting zone promotes a favorable chip formation and tool wear that leads to have an enhanced tool life and surface finish. the quality of surface is most significant foe any product. the surface roughness is main affecting thing such as for contact causing surface friction, wearing, in production time it is generating high cutting zone temperature. such high temperature list to have a dimensional deviation and enhance premature failure of cutting tools. in high cutting speed machining, it is clear that conventional cutting fluid application fails to penetrate the chip-tool interface and thus cannot remove heat effectively. lubrication and heat removal are the basic ways to keep the tool wear under control. but the conventional cutting fluid effective at lower cutting speed and gets ineffective at higher cutting mailto:abedin.mzoynal@duet.ac.bd effect of minimum quantity lubrication system for improving surface roughness in turning operation 51 speeds and feed, because the amount of heat generation in cutting zone is high. it is also shown rough results in high depth of cut in machining. the coolant cannot reach the critical areas and the tool work piece area or cutting zone area cannot be cooled. solving this problem, it is widely used in various machining operation minimum quantity lubrication (mql) method due to its huge advantages. this is possible if machining is carried out at maximum cutting parameters and at the same time able to achieve enhanced tool life (tl).when the high pressure soluble oil is used on the chip tool interface, it can reduce the cutting temperature and improve the tool life and surface finish to a certain extent. the prospect of using overflow coolant in high speed machining (hsm) is not very optimistic. most coolants, especially water-based coolants, have a negative impact on tool life. mql is one of the new system in which a very small amount of oil is pulverized into a compressed air steam. mql helps to reduce the cutting temperature and avoids the thermal shock of flooded coolant. given the high costs associated with the use of cutting fluids, and when it comes to enforcing stricter environmental regulations, the choice of mql seems obvious. furthermore, mql also reduces the cutting force, power consumption, tool wear, nodal temperature and friction coefficient. authors have also identified the research gaps for further research. although there have been many review articles on this topic. here in this study tries to find out major advantages using mql on machining process from various established journal. so that in future it will help going on further research on mql. the present work reviewed some papers on mql and experimentally investigates the role of mql on surface roughness in turning operation of cnc lathe machine. the wealth of nations can be judged by their investment in machining. modern manufacturing trends require parts to be produced quickly and smoothly. although there have been many review articles on this topic, this attempt has its own merits. it highlights the operational parameters that have been left untouched and can be proved very useful for any future studies in this field.as a significant enhancer. for convenient usage, passive techniques are important topics for scientists and researchers during recent decades. innumerable experimental studies have been conducted to improve the heat transfer rates by these techniques. scientists preferred passive heat transfer enhancement techniques due to their simplicity and applicability in many applications [1]. in recent years, heat transfer technology has been widely applied to refrigeration and air conditioning, automobile, process industries, etc. the main purpose of heat transfer enhancement techniques is to reduce the thermal resistance either by achieving the effective heat transfer surface area or by creating turbulence in the fluid flowing inside the tube. there are various arrangements are used and experimented to get better heat transfer rate such as insertion in tubes, the tube with fins, different tube shapes, corrugated tubes, baffle arrangements as well as different mediums like water, air, and nanofluids. the rearrangements of these different components are used for obtaining various purposes like increases the surface contact area of the fluid, create a swirl in the flow, and decrease the pressure drop to get enhancement heat transfer rates [2]. overall, rough surfaces or extended surfaces are used to increasing the effective surface area whereas inserts, winglets, turbulators, etc. are used for generating the turbulence [3]. based on scientific experiences, various types of inserts such as modified twisted tapes, wire coil, baffles, wire mesh, longitudinal swirl generators, and other types of tube inserts have been designed and studied numerically or experimentally. some researchers summarized the functions of different types of the insert which mainly enhanced single-phase convective heat transfer in heat exchangers by mixing main flow and the turbulence in the boundary layer region [4]. in recent years, heat transfer technology has been widely applied to devise applications in refrigeration, automotive, method industries as heat exchanger system. heat exchanger systems are used in different processes like conversion, utilization and recovery of thermal energy in various industrial, domestic applications and commercial processes. the most common examples include steam generation and condensation in power cogeneration plants widely used the heat exchanger to get better performance. the heating and cooling in thermal processing of pharmaceutical products manufacturing, chemicals industries and waste heat recovery plants are also utilizing the heat enhancement process by various enhancer to increase the heat exchanger efficiency. the increase in heat transfer performance can lead to a more economical design of heat exchanger which can help to make savings of energy, materials and cost which is related to a heat exchange process. this design also obeys many techniques termed as heat transfer augmentation which has an indicative impact on the enhancement of thermal performance. the present study investigated the heat transfer enhancement in various arrangements with insert devices as an important passive technique and their impacts on different mediums and configurations. 2 recent literature survey on mql in the pursuit toward achieving dry cutting, air machining, minimum quantity lubrication system in machining are the stepping stones. nevertheless, machining is always accompanied by certain difficulties, and hence none of these methods has provided a complete solution. dhar et al. [1] investigated the role of minimum quantity lubrication on cutting temperature, tool wear, surface roughness, and dimensional deviation in turning of aisi-4340 steel at cutting speed and feed rate combinations by uncoated carbide insert and found a significant result on tool wear rate, dimensional inaccuracy and surface roughness by using mq. mql helps to reduce the cutting temperature and avoids the thermal shock [2]. lugscheider et al. [3] used this technique in remaining process of gray cast iron and aluminum alloy with coated carbide tools and concluded that it caused a reduction of tool wear when compared with the completely dry process and as a result an improvement in the surface quality of the holes. dhar et al. [4] also used this method in turning process of medium carbine steel and found that, in some cases, a mixture of air and soluble hossain and abedin (2021): international journal of engineering materials and manufacture, 6(1), 50-59 52 oil has been shown to be better than overhead flooding application of soluble oil. the drilling of aluminum silicon alloys is one of those processes where dry cutting is impossible due to the high ductility of the work piece material [5].without cooling and lubrication, the chip sticks to the tool and breaks it in a very short cutting time. therefore, in this process a good alternative is the use of the mql method [6, 7]. khan et al. [8] described that, mql provides environment friendliness with machining (maintaining neat, clean and dry working area, avoiding inconvenience and health hazards due to heat, smoke, fumes, gases, etc. and preventing pollution of the surroundings) and improves the machinability characteristics. dhar et al. [9] compared the mechanical performance of mql to completely dry lubrication for the turning of aisi1040 steel based on experimental measurement of cutting temperature, chip reduction coefficient, cutting forces, tool wears, surface finish, and dimensional deviation. results found that the use of near dry lubrication leads to lower cutting temperature and cutting force, favorable chip–tool interaction, reduced tool wears, surface roughness, and dimensional deviation. the increasing demand for high machine productivity requires the use of high cutting speeds and feed speeds. this processing inherently produces high cutting temperatures, which not only shortens tool life, but also impairs product quality. metal cutting fluids have changed the performance of machining operations due to their lubrication, cooling and chip removal functions, but in terms of employee health and environmental pollution, the use of cutting fluids has become a problem [10, 11]. they suggested mql mainly by which reduction the cutting zone temperature and favorable change in the chip-tool and work-tool interaction. productivity of any machine tool and any tool processing parts depends on the quality of the parts the surface produced by the machine. so for the good functional behavior of any mechanical parts good surface quality is essential [12]. lohar and nanavaty [13] describes that the surface in hard turning of hardened aisi 4340 is better as compare to dry and wet turning. there is 30% improvement in surface finish using mql of turning operation and use the analysis of variance (anova) is carried out using minitab software to investigate difference in average performance of factors using test. as usual hard turning process requires large quantities of coolants and lubricants for machining. the cost of associated with lubricants increases the total cost of production and conventional cutting fluid application fails to penetrate the chip-tool interface. thus conventional cutting fluid cannot remove heat effectively. considering cost and the environmental laws are enforced, alternatives has been sought to minimize the use of cutting fluid in machining operations. some of these are dry machining and machining with minimum quantity lubrication (mql). kedare et al. [14] found that the surface finish improved by 27% using mql system during end milling operation. the results of this study show that mql can be considered an economical and environmentally friendly lubrication technology. y s laio et al. [15] described that the tool life significantly improved by mql in hsm of nak80 hardened steels when cutting parameters are selected properly. mql is the name given to the process in which very small amount of oil is pulverized into the flow of compressed air. mql helps in reducing cutting temperature and also averts thermal shocks, experienced by flood coolant. zhou et al. [16] has investigated of surface damage produced by whisker-reinforced ceramic cutting tools in the finish turning of inconel 718 (nickel-based super alloy). the aim of this study is the effects of the cutting parameters (cutting speed, depth of cut and feed), tool wear and coolant conditions on the surface damage to it occurring during dry and wet turning. mql shows better result at slow cutting speed and low depth of cut. as per as mql is concerned surface roughness value is almost constant with little variations. surface finish of mql is better with medium cutting speed. the main objective of this paper is mql provides the benefits mainly by reducing the cutting temperature, which improves cooling effect and results in better surface finish. cakir et al. [17] has investigated the aisi 1040 steel by turning process, the effects of cutting fluid, application of some gases and dry cutting on cutting force, thrust force, surface roughness, friction coefficient and shear angle were studied. dry machining, wet machining and machining with oxygen, nitrogen and carbon dioxide gases were carried out under constant cutting speed, three level of feed and depth of cut. chrong-jyh et al. [18] has investigated the optimization of cnc turning operation parameters like speed, feed and depth of cut for skd11 (jis) using the taguchi and grey relational analysis method. the cutting tool is made of carbide and coated with titanium nitride (tin) and watersoluble cutting fluids are mixed with water at different ratios depending on the machining operation. rajan and philip by using aisi 4340 steel and the combination has been studied and compared with dry and wet turning under the parameters of speed nation of snmg 120408 and p30 tool material, hard turning with minimal cutting fluid (htmf, feed, depth of cut [19]. so the surface roughness is used as an indicator of the quality of any product. it influences such as wear resistance, fatigue strength, coefficient of friction, corrosion resistance, and lubricity, wear the speed of processing the part. in today's manufacturing industry quality is one of the important factors, the only components that affect customer satisfaction. in every industrial field, the surface quality is determined by the surface roughness of the component [20, 21]. tsai et al. [22] found that the cooling ability of water in terms of temperature drop decreases with an increase in both temperature and depth of cuts. so, this might be the reason for flood cooling having no effect at higher depth of cuts, while the effect for mql might be due to inadequate lubrication. lajis et al. [23] described that the machining temperature at the cutting zone is an important index of machinability and needs to be controlled as far as possible. mql is expected to provide some favourable effects mainly through reduction in cutting temperature. when the chip-tool contact is partially elastic, where the chip leaves the tool, mql is dragged in that elastic contact zone in small quantity by capillary effect and is likely to enable more effective cooling [23]. brain boswell, mohammad nazrul islam, state that, the experimentation involved in determining a suitable environment alternative to using effect of minimum quantity lubrication system for improving surface roughness in turning operation 53 little amount of cutting fluid in high speed velocity at cutting zone. as a result they observed and found that reduce thermal shock and stresses generating during machining [24]. the mql systems enabled reduction in average chip tool interface temperature up to 10% as compared to using conventional cutting fluid. most of the authors have indicated adequate betterment in performance with mql machining compared to dry machining, and more meaningful results could have been obtained if it was also compared with flood machining. surface quality of the machined parts is one of the most important product quality indicators and most frequent customer requirements which can be obtained by mql processing and get accurate finishing than conventional fluid. cha et al. [25] found that inconel 718 alloy is widely used as material of aircraft engine, has a good mechanical property in high temperature, strong anti-oxidation characteristics in oxidized current over 900∘c900∘c, and also is not easily digested in the air containing sulfur, therefore, its usage as mechanical component is expanding rapidly. even though inconel alloy 718 is difficult to machine, it requires highly precise processing/machining to sustain its component quality of high accuracy. in this paper, general turning operation conditions arc tested to select the best cutting process condition by measuring surface roughness through implementing experiments with orthogonal array of cutting speed, feeding speed and cutting depth as processing parameters based on the taguchi method. optimal turning operation conditions are extracted from the proposed experimental models. lee et al. [26] suggested in their research how to derive optimum cutting conditions for the milling process in mql machining. to reach these goals, a bunch of finish milling experiments was carried out while varying cutting speed, feed rate, oil quantity, depth of cut and so on with mql. patil et al. [27] characterized airborne micro droplet diameters and size distribution from two commercially available lubricants a and b for internal minimum quantity lubrication (mql). 3 mql system set up and its applications in general, there are two methods are widely used in machining process one is external spray and another is throughtool. the external spray system made by a coolant tank or reservoir which is connected with tubes fitted with one or more nozzles. it is easy method than others, inexpensive, portable, and suited for almost all machining operations. through-tool mql systems are available in two configurations: based on the method of creating the air-oil mist. the first is the external mixing others name is one channel system. here, the oil and air are mixed externally, and piped through the spindle and tool to the cutting zone. minimum quantity lubrication and dry metalworking system is the most recent and quickly modern technology. this technology was mainly developed in the aerospace industry because the scale of the work amplified the negative attributes of the conventional flood type coolant and it was not possible surface quality requirements by using dry machining. this type of lubrication system can apply anywhere would like to maximize tool life without the conventional coolant mess. such asaluminum, steels, hsla, super alloys, tool steel, copper and brass. various process like as-lathe operation, grinding, cnc profiling, turning, and drilling, milling, etc. to extend the life time of cutting tools and reduces friction between work piece and cutting edges mql contributes a lot. its assists in smoothing and quick operation. obviously the health and safety aspects of using cutting fluids add to the cost of metal cutting as suitable disposal of the cutting fluid is needed. most of the researcher have showed a noticeable improvement in performance with mql machining and more meaningful results could have been obtained. mql very useful on hard machining process because of its high pressure jet flow, good mixture of coolant and applied at the chip-tool interfaces and could reduce cutting temperature. figure 1: high speed cutting fluid with compressor: (1a) nozzle (1b) compressor (1c) cutting fluid reservoir 1c 1a 1c hossain and abedin (2021): international journal of engineering materials and manufacture, 6(1), 50-59 54 figure 2: conventional cutting set up: (2a) nozzle (2b) work piece material (2c) tool post in figure 1 represents the set up for high speed cutting fluid with compressor where lubricant (grade 60) and air is mixed by mql set up based on spray gun of cnc lathe (model: ck6136a-2, made in china). the two separate hollow pipes carry lubricant and air which mixed in mixing chamber (white colour) and just before the tip of the nozzle. the lubricant flow is controlled by flow control valve. in order to have contentious mist, constant pressure is assured by the pressure gauge reading because change in pressure may vary quantity of the lubricant coming out of the nozzle and outer diameter of nozzle is 2.5mm. experiments are carried with the following parameter viz. coolant pressure, spot distance, coolant flow rate are 5bar, 20mm, 850ml/hr. from figure 2 it is shown that the photographic view of conventional cutting fluid on machining process. in figure 3, it has shown that the schematic view of mql set up and all accessories which are to be needed for this system. figure 3: schematic view of mql set up the schematic view of minimum quantity lubrication system set up shows by figure 3 [1]. the conventional cutting fluids are not effective in such high production machining, particularly in continuous cutting of materials like steel and alloy. minimum quantity lubrication presents itself as a viable alternative for turning with respect to tool wear, heat dissipation, and machined surface quality. 4 experimental method and sample preparation the experimental set-up consists of a cnc lathe (model: ck6136a-2) machine. the experiment done using two types of cutting fluids. one is conventional cutting fluid and another is minimum quantity lubrication which is extremely small amount of cutting fluids. the requirements of minimum quantity lubrication is supplied by the mql system during the experiment at 5 bars pressure. the mql system is a superfine particle oil mist generator capable of supplying superfine particles of oil–air mixture from an ejecting nozzle, while discharging cutting oil at a level of 8501000ml/hr. the work piece (ø81mm×l457.2mm) material is shown in figure 4 is a cylindrical round bar of mild steel and consists of hardness is (48-50) hrc. a tungsten carbide tool is shown figure 5 which is used for this experiment which contain (l = 8.7mm, i.c = 12.7mm, r = 0.8mm, d = 5.16mm) specification with wnmg tool holder. the mql system generates the oil mist based on the principle of minimum quantity lubrication, oil mist generator. the experiment is carried out at three cutting speeds are 600, 700 and 800 rev/min at 60, 70 and 80 mm/min feed rate with 015, 020 and 0.30 mm depth of cut. 2b 2a 2c effect of minimum quantity lubrication system for improving surface roughness in turning operation 55 figure 4: work piece raw material (mild steel 50hrc) figure 5: wnmg tool holder with insert table 1: experimental data sl. no. cutting speed (rev/min) feed rate (mm/min) depth of cut (mm) response parameters surface roughness(µm) dry flooded mql 1 600 60 0.15 2.31 2.25 1.85 2 600 60 0.20 2.12 2.38 1.67 3 600 60 0.25 2.40 2.11 1.56 4 600 60 0.15 1.95 1.89 1.48 5 600 60 0.20 2.10 1.97 1.69 6 600 60 0.25 1.96 1.84 1.35 7 600 60 0.15 1.88 1.76 1.23 8 600 60 0.20 2.22 1.72 0.98 9 600 60 0.25 1.91 1.68 0.90 10 600 60 0.15 1.75 1.66 1.20 11 600 60 0.20 2.40 1.78 1.11 12 600 60 0.25 2.10 1.63 0.87 13 600 60 0.15 1.89 1.53 0.79 14 600 60 0.20 1.77 1.66 0.84 15 600 60 0.25 1.82 1.75 0.68 16 600 60 0.15 1.93 1.52 0.72 17 600 60 0.20 1.78 1.60 0.80 18 600 60 0.25 2.12 1.58 0.78 hossain and abedin (2021): international journal of engineering materials and manufacture, 6(1), 50-59 56 5 result and discussion the experiments were designed by using various methods with minitab 19 software. the surface roughness are determined by three cutting condition such as dry, conventional flood and mql systems. from these, the best and optimal results are found by using minitab software. at first specimen is prepared and experiments are carried out in cnc lathe machine. to visualize the effect of cutting speed (cs) depth of cut (doc) over surface roughness parameters (ra) of dry, flooded and mql condition are shown in following figures 6-8. figure 6: analysis of line plot of mean surface roughness for cutting speed (cs). the concept of minimum quantity lubrication (mql) has been suggested since a decade ago as a means of addressing the issues of environmental intrusiveness and occupational hazards associated with the airborne cutting fluid particles on factory shop floors. in figure 6 represents the analysis of line plot of mean surface roughness for cutting speed (cs) of 600 rpm. as shown in figure 6, the mean is the average of the number (response data) and it is used to analyse the way in which the mean varies across different groups of data. as the experiment are done with constant cutting speed, constant feed rate with varies of depth of cut, so it is drawn two line plot figure for dry, flooded and mql over two cutting condition. in the figure 6, it is clear that when cutting speed is constant and applying mql system the surface roughness value is significant over dry and flooded condition. figure 7: analysis of line plot of mean over depth of cut (doc) figure 7 shows the analysis of line plot of mean over depth of cut (doc). as can be seen in the figure 7, with small change of depth of cut, the surface roughness in the machining becomes optimum for mql system comparing with those for dry and flooded situation. when depth of cut is 0.25mm (green colour), mql system show the excellent result of surface roughness than others two depth of cut. in conclusion, it can be said that the cutting performance of mql system of machining is better than that of dry and conventional machining. as per as mql is concerned surface roughness value is almost constant with little variations. minimum quantity lubrication (mql) and cryogenic cooling system has been developed now a days for better surface roughness, temperature and tool life. also, mql reduced effect of minimum quantity lubrication system for improving surface roughness in turning operation 57 average auxiliary flank wear and notch wear on auxiliary cutting edge, surface roughness also grew very slowly under mql condition. surface roughness is also an important index of machinability or grind ability because performance and service life of the machined component are often affected by its surface finish. mql cooling effect also improved to some extent with the decrease in feed particularly at lower cutting velocity. figure 8: time series plot of surface roughness for dry, flooded and mql in figure 8 shows the time series plot of surface roughness for dry, flooded and mql. as can be seen in the figure 8, it is clearly shows that the surface roughness value is optimal than dry and flooded condition. with increasing machining time mql show better surface roughness with gradually. the machining temperature at the cutting zone is an important index of machinability and needs to be controlled as far as possible. mql is expected to provide some favourable effects mainly through reduction in cutting temperature. with the increases of machining time the surface roughness value of mql machining is excellent than dry and flooded machining. 6 conclusion in the cutting performance of machining, mql provides the better surface roughness result than dry and flooded condition which are shown from the experiment. not only surface roughness, but mql also provided reducing tool wear, improved tool life and better surface finish as compared to dry and flooded machining of steel. in this study, mql provides several benefits in the machining of 50hrc steel. the main objective of the present work was to experimentally investigate the role of minimum quantity lubrication (mql) on surface roughness in turning operation 50hrc steel and compared the effectiveness of mql with that of dry and conventional flood. the findings of the present experimental investigation can be written in the following way. 1. mql machining of surface roughness is seen to be significant and optimal when compared with the dry and flooded. 2. it is evident that mql improves surface roughness finish depending upon the work–tool materials and mainly through controlling the deterioration of the auxiliary cutting edge. 3. it is appeared that mql system grows quite fast under dry and conventional machining due to more intensive temperature. 7 future scopes of mql the future direction of mql can be illustrated in the following way. • metal cutting is one of the most extensively used manufacturing processes, and its technology continues to advance in parallel with the developments in material from surface of a work-piece to achieve the desired product and researcher always tried to fulfilled the requirement. • the new method of minimum quantity lubrication (mql) system is the delivering metal cutting fluid to the chip-tool interface and by this method, a little fluid, when properly selected and applied, can make a substantial difference in how effectively a tool performs and is to reduce the machining costs by improving its quality and productivity. • mql is a most environment friendly method and used to minimize the negative aspects of cutting fluid which will be most helpful for researcher in their further research work. hossain and abedin (2021): international journal of engineering materials and manufacture, 6(1), 50-59 58 • iv. by using mql system it is possible to reduce friction, cooling and flushing away chips. the cutting performance of mql machining is better than that of conventional machining. researchers will be more benefits for future research work in this field. • mql provides the benefits mainly by reducing the cutting temperature, which improves cooling effect and results in better surface finish. acknowledgements the authors would like to acknowledge the teachers and staffs in the industrial and production engineering department, duet, gazipur, bangladesh for the entire supports and valuable suggestions and helps during the entire experimental work. references [1] dhar n r, islam s, kamruzzaman m, (2007) effect of minimum quantity lubrication (mql) on tool wear, surface roughness and dimensional deviation in turning aisi-4340 steel g.u. j. science 20(2): 23-32. [2] liao y s, lin h m (2007) mechanism of minimum quantity lubrication in high-speed milling of hardened steel. international journal of machine tools & manufacture 47(11):1660-1666 [3] lugscheider e, knotek o, barimani c, leyendecker t, lemmer o, and wenke r, (1997) investigation on hard coated reamers in different lubricant free cutting operations, surface and coating technology, 90: 172-177 [4] dhar n r, islam m w, and mithu m a h,(2006) the influence of minimum quantity of lubrication on cutting temperature, chip and dimensional accuracy in turning aisi-1040 steel, journal of material processing technology, 171: 93-99. [5] derflinger v, brandle h, and immermann h, (1996) new hard/ lubricant coating for dry machining, surface coating technology, 113: 286-292. [6] brager d u, dini a e, mirranda and coppini n l, (1999) minimal lubricant in the drilling process of aluminium-silicon alloy-a356 (sae 323), proc. of the 3 rd int. machining am grinding conf. (sme), cincinnmi, usa, 1: 683-697. [7] rahman k m, (2004) effect of minimum quantity lubrication in drilling commercially used steels, m. engg. dissertation, buet, dhaka, bangladesh. [8] khan m m a, m a h mithu, dhar n r, (2009) effects of minimum quantity lubrication on turning aisi 9310 alloy steel using vegetable oil-based cutting fluid. journal of materials processing technology, 209, 15-16: 5573-5583. [9] dhar n r, ahmed m t, islam s, (2007) an experimental investigation on effect of minimum quantity lubrication in machining aisi 1040 steel. international journal of machine tools and manufacture. 475: 748-753. [10] dhar n r, siddiqui a t and rashid m h, (2006), effect of high pressure coolant jet on grinding temperature, chip and surface roughness in grinding aisi-1040 steel, arpn journal of engineering and applied sciences. vol. 1(4): pp. 22-28. [11] huang, y. and liang, s.y., 2003, “modelling of the cutting temperature distribution under the tool flank wear effect”, journal of mechanical engineering science, vol. 217(11), pp. 1195-1208. [12] benardos p g, vosniakos g c (2003) predicting surface roughness in machining: a review. int. mach. tools manuf. 43:833-844. [13] lohar d v and nanavaty c r, (2013) performance evaluation of minimum quantity lubrication (mql) using cbn tool during hard turning of aisi 4340 and its comparison with dry and wet turning. bonfring international journal of industrial engineering and management science 3-3: 102106. [14] kedare s b, borse d r, and shahane p t (2014) effect of minimum quantity lubrication (mql) on surface roughness of mild steel of 15hrc on universal milling machine. 3rd international conference on materials processing and characterization. vol 6: 150-153. [15] liao y s, lin h m (2007) mechanism of minimum quantity lubrication in high speed milling of hardened steel. international journal of machine tools and manufacture. 47 (2007), pp: 1660-1666. [16] zhou j m, bushlya v, and stahl j e (2012). an investigation of surface damage in the high speed turning of inconel 718 with use of whisker reinforced ceramic tools. journal of materials processing technology 212: 372– 384. [17] çakır o, kıyak m, and altan e, (2004) comparison of gases applications to wet and dry cuttings in turning. international journal of materials processing technology. 153–154: 35–41. [18] chorng-jyh t, yu-hsin linb, yung-kuang yanga, ming-chang jengc (2009) optimization of turning operations with multiple performance characteristics using the taguchi method and grey relational analysis.” journal of materials processing technology. vol-209: 2753–2759. effect of minimum quantity lubrication system for improving surface roughness in turning operation 59 [19] varadarajan a s, philip p k, and ramamurthy b, (2002) investigations on hard turning with minimal cutting fluid application (htmf) & its comparison with dry & wet turning. international journal of machine tools & manufacture 42: 193–200. [20] feng c x j, wang x, (2002) development of empirical models for surface roughness prediction in finish turning.int. j. adv. manuf. technol.20: 348-356. [21] karayel d (2009) prediction and control of surface roughness in cnc lathe using artificial neural network, journal of material processing technology. 209: 3125-3137. [22] tsai m.k., lee b.y., yu s.f., 2007. a predicted modeling of tool life of high-speed milling for skd61 tool steel. int j adv manufacturing technology.26: 711–717. [23] karayel d (2009) prediction and control of surface roughness in cnc lathe using artificial neural network, journal of material processing technology. 209: 3125-3137. [24] brain boswell, mohammad nazrul islam (2012), feasibility study of adopting minimum quantities of lubrication for end milling aluminum processing’s of the world congress on engineering vol. 3. [25] cha, jinhoon, & han, sangbo. (2010). searching optimal cutting condition for surface roughness in turning operation on inconel 718 using taguchi method. journal of the korean society of machine tool engineers, 19(2): 295-300. [26] lee, j.h, ko, t.j,. & baek, d.g. (2009). a study on optimal cutting condition of mql milling using response surface analysis. journal of the korean society of machine tool engineers, 26(1): 43-50. [27] amla patil, jay raval, tim bangma, immanuel edinbarough, bruce tai, david stephenson, suleiman obeidat and wayne nguyen hung (2020). international journal of engineering materials and manufacture (2020) 5(4) 98-115. international journal of engineering materials and manufacture (2021) 6(3) 102-113 https://doi.org/10.26776/ijemm.06.03.2021.01 j. grass n 1 . , d. rojas p. 1 , r. t. coelho 1 and barragan g. 2 1 sao carlos school engineeringuniversity of sao paulo (eesc-usp) r. da reitoria, 374 – cidade universitária, butantã, são paulo – sp, 05508-220 2 grupo de investigación en ingeniería aeroespacial, universidad pontificia bolivariana e-mail: jsgrassn@usp.br references: grass et al. (2021). numerical and experimental analysis of gas flow in a coaxial nozzle applied to directed energy deposition (ded). international journal of engineering materials and manufacture, 6(3), 102-113. numerical and experimental analysis of gas flow in a coaxial nozzle applied to directed energy deposition (ded) j. grass n., d. rojas p., g. barragan d. r. and r. t. coelho received: 02 march 2021 accepted: 30 april 2021 published: 15 july 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract directed energy deposition (ded) is an additive manufacturing process, which uses a concentrated laser beam to create a melt pool on the substrate. a nozzle is used to carry metal powder within a gas flow until the melt pool, concentrating the flow at the same point. coaxial nozzles usually have also a shield gas flow to prevent oxidation and an internal flow to protect the optical system. a right flow configuration must be selected to avoid high turbulence at the nozzle exit, leading to an efficient, inexpensive, and high-quality process. due to the complexity of the process, cfd – computer fluid dynamics are becoming necessary to understand the behaviour of those gas flows in ded processes. cfd can offer results close to reality and may allow an optimization of the whole nozzle designs, besides selecting the best gas flows for each application. the present work develops a cfd simulation of the gas flow behaviour in a coaxial nozzle with three internal annular channels (internal, carrier and shield). an initial set of gas flow was selected, based on previous experience of the manufacturer, and then improved. it searches for the low gas consumption, to form a focal point coinciding with the laser focus and a low velocity, which favours the deposition quality. to check the accuracy of the proposed cfd model, experimental measurements of gas velocity were performed and compared with simulated results. keywords: additive manufacturing, ded, cfd 1 introduction additive manufacturing is a process by which 3d object can be produced, starting directly from their 3d cad. this process is carried out by depositing layer by layer to form the desired geometry, without the need of various manufacturing process and a number of tooling and jigs (1). amongst existing variety of am process, directed energy deposition (ded) is one of the best for metal deposition. that is defined as a process in which focused thermal energy source, such as a laser beam, an electron beam or plasms arcs are used to melt metals, which are deposited (2). ded has been widely acclaimed for its ability to create components with complex geometries, customized parts without design restrictions, repairs worn components and modify components already manufactured (3). ded is also considered a disruptive manufacturing method, since it allows the use of different materials in the same process and compared to the traditional manufacturing process, is considered a more profitable process due to the short time it demands and its flexibility (4). in ded process, two forms of raw material can be used; powder and wire. powder metal is the most used raw material due to its versatility and the fact that most materials can be transformed into powder. in processes using metal powder, a nozzle is responsible to deliver the powder into the melt pool, using inter gas flows. there are, basically, two types: lateral and coaxial nozzles. due to its easy fabrication, versatility for working with metal powders and its geometry efficiency, coaxial nozzles have been the most used, lately. the coaxial nozzle can be configured with two or three gas flows. two flows, use carrier and shield flow. the most recent models contain coaxial annular channels. designs with three flows use nozzle, carrier and shield channels. the inner channel comes out around the laser beam and it is used to protect the optical system. the carrier gas flows through a middle channel and carries the powder flow to the melt pool. the shield flow comes an outer channel and is used to protect the melt pool against oxidation. (some author refers to the nozzle gas as axial gas and the shield gas as shape gas) the combination of those three coaxial gas flows is strictly related with the ded process efficiency. they all must numerical and experimental analysis of gas flow in a coaxial nozzle applied to directed energy deposition (ded) 103 create a focal point, to deliver the right powder volume to the melt pool, created at the surface in which deposition will occur. additionally, the powder speed at the melt pool, the combination between feed speed and laser power has to be enough to melt the whole volume of delivered powder. therefore, to improve the am process, it is important to develop models to understand the gas flows and demonstrate how the efficiency of the process is affected by them (5). 2 literature review lin (6) performed a numerical analysis, using two types of geometries nozzles. the first with an inward configuration in the inner channel (fig 1a) and the other with an outward configuration in the same channel (fig 1b) using powder size between 45 and 100 μm. it was concluded that the convergence point of powder-gas flow is affected by the coaxial geometry. using the outward configuration, a widely dispersed stream powder was founded and a convergence point at a distance of 5 mm, which was not very uniform. using the inward configuration, the focal point could not be visualized, due to the interaction between flows before the coaxial nozzle outlet. in both nozzles it was observed that the powder concentration increased when the gas flow decreased. figure 1: a. inward configuration b. outward configuration in (7) authors carried out a theorical-experimental analysis, measuring the outlet powder velocity in a coaxial nozzle, finding that the highest speed was exactly twice the lowest speed, getting an average of 9.3 m/s. it was also concluded that due to different gas flows, the particles can have a higher drag after the nozzle outlet. in (8) authors used the fluent™ software. a numerical analysis was carried out in order to analyse the behaviour of metal powder at different deposition heights, using nitrogen gas and 316l stainless steel particles of 45 μm, in average. the first simulation was done at free jet, them locating the substrate at a distance of 5, 10 and 20 mm respectively. it was found that as the deposition distance increased, the powder concentration decreasing on the substrate. authors did recommend the use of depositions distances higher than 10 mm under those parameters tested. in (9) authors used a coaxial nozzle with two annular channels. was setup a standoff 11 mm, gas flow of 3 l/min in the carrier and 2 l/min in the shield. a cfd analysis was performed using kє turbulence model to simulate the gas flow. it was found that the convergence point was formed at a distance of 13 mm. experimentally, it was measured the cross section at the depositions in relation with the powder supply. it was evidenced that the geometry of the coaxial nozzle and the gas flow, offered a process with a 53% efficiency. based on these results, the initial coaxial nozzle was redesigned and validate numerical and experimentally, using the same gas flows. its convergence point was formed at 8 mm from the nozzle outlet, but this was formed out the laser beam. carrier gas flow greater than 3 l/min can create sputter on the substrate and could cause problems to the nozzle. experimentally it was found that this coaxial nozzle redesigned offered a higher concentration of metal powder with the same gas flows and increase the efficiency of the process to 74.8%. koruba, wall and reiner in (10) carried out a numerical and experimental analysis of the inert gas on ded process. using ansys software to simulate a coaxial nozzle with two annular channels; carrier and shield. simulating different gas flows, it was founded that as the shield gas flow increases, the focal point is disturbed up to a point where its formation is not able. using the same gas flows in carrier and shield, only the carrier outlet velocity increases, so the particles will strongly collide with the substrate. experimentally found that a high flow in carrier result in deposition of higher dilution, deeper haz and lower hardness. a high flow in the shield gas, increases the rate of cooling but there was risk of irregularities occurring in the deposition. in (11) authors used three nozzles with different geometries and configurations. nozzle a and b with three annular channels: axial, shaping and carrier flows. nozzle c with two channels: axial, carrier and shielding flows. a numerical and experimental analysis was carried out. using a pitot tube measurement of the outlet gas velocity in the three nozzles were carried out. in nozzle c, it was possible to observe the variation of velocities up to the distance of 11 mm. at a distance of 1 mm, the gas flow was an annular structure, increasing the convergence until forming its convergence point at a distance of 9 mm and a velocity of 1.85 m/s at this point. in nozzle b, it was founded that the outlet velocity was affected by the carrier gas flow, a uniform velocity field was between 11 and 15 mm and its maximum value was 6.11 m/s. in nozzle a, the outlet velocity was measured between 1 and 5 mm and the gas showed a uniform annular structure, reaching a velocity of 20.5 m/s and showing that the axial gas flow affect the outlet velocity of the carrier and shield gas. numerically and using comsol™ software, it was found that the highest j. grass n et al. (2021): international journal of engineering materials and manufacture, 6(3), 102-113. 104 velocities were 4.49 m/s, 8.86 m/s and 58.9 m/s for a, b and c respectively. estimating measurement errors between 30% and 50%, which may be associated with atmospheric conditions at the outlet of the nozzle, or errors in the calibration of the pitot tube. computed fluid dynamics (cfd) is considered the art of replacing the differential equations of the physical aspects of fluids flows with numbers and advancing these numbers in space/time to obtain a final numerical description of the flow field of interest (12). the mesh in cfd simulation is a discrete representation of a geometric domain, which typically includes content and environment form the real world. the creation of the mesh, and the appropriate computational domain has been a challenge, since the complexity of the geometries, the type of flow and the accuracy offered by the different types of meshes must be taken into account. the reliability of the resulted values depends on this. (13) bearing that in mind, the present study aims at a numerical analysis of the behaviour of gas flows in a coaxial nozzle applied to ded process. using a cfd simulation, gas flows were observed on the three channels and different sets of parameters were tested. selecting one of the flow-sets experimental velocity measurement were performed and compared with simulated results. 3 cad and numerical modelling using a siemens nx 3d cad software, a nozzle model was obtained together with a volume below to study the free-flow of gas at outlet (fig 2). figure 2: coaxial nozzle cad (nozzle, carrier and shield) with volume at exit. the volume outside the nozzle has lower limit at 10 mm below the nozzle, which is the laser focal point and where the substrate has to be positioned. due to the annular geometry of the nozzle, just half of it was simulated, and was setup a symmetry plane in the computational domain, improving computational efficiency. a refined mesh was used to speed up the simulation and create a better gas flows visualization. in order to no disturb the gas flow, no deposition surface was set below nozzle outlet (fig.2). the numerical analysis was focused on the dynamics of the gas flow in a ded process. the initial assumption is the following: the gas is treated as steady-state turbulent flow with constant velocity distribution in the inlet boundaries boundaries inlet flow have the same gas source constant gas density no-slip condition. due to the complexity of the geometry for the computational domain, a polyhedral mesh was chosen, which offers a balanced solution to generating complex meshes. this mesh is relatively easy and efficient to construct, as it does not require more surface preparation than the equivalent tetrahedral mesh. besides, they contain approximately five times fewer cells than a tetrahedral mesh for a given initial surface area. simulations were performed using a polyhedral mesh of 2,433,130 elements, being refined in the gas inlets, walls, symmetry plane, and the bottom outlet (figure 3). different flow values were simulated in free jet at exit, to understand and observe the gas behaviour after the nozzle outlet and to know the convergence points under different flow conditions. numerical and experimental analysis of gas flow in a coaxial nozzle applied to directed energy deposition (ded) 105 figure 3: details of polyhedral mesh refined used for the computational domain. solving gas flows in space-time usually requires very high computational times and for this reasons, different turbulence model are available in the software used most of them based on the reynolds-average navier stokes (rans) models (14) in rans approximations all fluid instability is considered part of the turbulence and by averaging the non-linearity of the navier-stokes equations it results in terms that must be modelled. the complexity of turbulence makes it unlikely that a single rans model can represent all turbulent flows and for that reason several turbulence models based on rans were developed. all these considered as engineering approximations and not as physical laws (15) k-є is a two-equation turbulence model, which results in the transport equation for the turbulent kinetic energy k and the turbulent dissipation rate є. in order to determine the turbulent viscosity of the eddy formed by a fluid that is being analysed, it can be defined by the equations below. the turbulent eddy viscosity 𝜇𝑡 is calculated as: 𝜇𝑡 = 𝜌𝐶𝜇𝑓𝜇𝑘𝑇 (eq. 1) where 𝜌 is the density, 𝐶𝜇 is a model coefficient, 𝑓𝜇 is a damping function and t is the turbulence time scale. the transport equations for the kinetic energy k and the turbulent dissipation rate є are: 𝜕 𝜕𝑡 (𝜌𝑘) + 𝛻. (𝜌𝑘𝑣) = 𝛻. [(𝜇 + 𝜇𝑡 𝜎𝑘 ) 𝛻𝑘] + 𝑃𝑘 − 𝜌(𝜀 − 𝜀0) + 𝑆𝑘 (eq.2) 𝜕 𝜕𝑡 (𝜌𝜀) + 𝛻. (𝜌𝜀𝑣) = 𝛻. [(𝜇 + 𝜇𝑡 𝜎𝜀 ) 𝛻𝜀] + 1 𝑇𝑒 𝐶𝜀1𝑃𝜀 − 𝐶𝜀2𝑓2𝜌 ( 𝜀 𝑇𝑒 − 𝜀0 𝑇0 ) + 𝑆𝜀 (eq. 3) where 𝑣 is the mean velocity, 𝜇 is the dynamic viscosity. 𝜎𝑘, 𝜎𝜀, 𝐶𝜀1, and 𝐶𝜀2 are model coefficients. 𝑃𝑘 and 𝜌𝜀 are production terms. 𝑓2 is a damping function. 𝑆𝑘 and 𝑆𝜀 are the user-specified source terms. variable 𝜀0 is the ambient turbulence in the source terms that counteracts turbulence delay. the possibility to impose an ambient source term also leads to the definition of a specific time-scale 𝑇0, that is defined as: 𝑇0 = 𝑚𝑎𝑥 ( 𝑘0 𝜀0 , 𝐶𝑡 √ 𝑣 𝜀0 ) (eq. 4) where 𝐶𝑡 is a model coefficient. the turbulent production is given by: 𝐺𝑘 = 𝜇𝑡 𝑆 2 − 2 3 𝜌𝑘𝛻. 𝑣 − 2 3 𝜇𝑡 (𝛻. 𝑣) 2 (eq.5) the buoyancy production is given by: 𝐺𝑏 = 𝛽 𝜇𝑡 𝑃𝑟𝑡 (𝛻𝑇. 𝑔) (eq.6) 𝛽 is the coefficient of the thermal expansion. for the constant density flows using the boussinesq approximation, 𝛽 is user specified, 𝑃𝑟𝑡 is the turbulent prandtl number, 𝑇 is the gravitational vector [19]. the numerical solution was carried out using a siemens star-ccm+™. it was considered an inert gas atmosphere in the computational domain, which neglects the air-gas mixture. inert gas was set with the argon industrial properties 𝜌 = 1.69 𝑘𝑔 𝑚3 . j. grass n et al. (2021): international journal of engineering materials and manufacture, 6(3), 102-113. 106 initially, condition a was simulated as that recommended by the manufacturer of the deposition head. then, different sets were simulated always towards minimizing gas consumption and improving deposition quality. table 1 shows the whole set of combinations simulated. condition b used the minimum value for the nozzle, tested to save some argon gas and to observe its effect on the overall flow configuration. by analysing the results up to that point, intermediate low values for nozzle and shield gas were tested together with a slightly higher value for carrier, making condition c. following conditions d, e and f, were selected in attempts to achieve two simultaneous conditions: stablish a convergence point for the carrier flow and minimizing the velocity at these points. table 1: conditions to numerical analysis 4 experimental setups the pitot tube was clamped in a 3 jaw chuck positioned at the origin of the x,y machine axe. the chuck center was found using the renishaw omp 60 optical probe supplied with the machining center, romi hybrid d800 model. the pitot tube was positioned directly into the fluid flow and flow velocity was measured. using bernoulli principle pressure was measured using a micromanometer tsi 8705 and related with speed using equation (7): 𝑣 = √ 2(𝑃𝑠𝑡𝑎𝑔−𝑃) 𝜌 (eq.7) the pitot tube used has a single internal diameter of 1 mm and was connected with micromanometer by a plastic tube. (fig.4) figure 4: setup experimental test flow velocities were measured in 1 mm intervals over the x and y axe. an x-y on the z direction, the intervals were at every 2 mm, from 0 to 10 mm below the nozzle. at each measuring point, a time of 20 seconds was given for the argon flow and the micro manometer measurement to stabilize. figure 5 shows the set up for measurements. the experimental data were further processed using an interpolation function in matlab™ and later plotted in 3d graphs for better examinations. numerical and experimental analysis of gas flow in a coaxial nozzle applied to directed energy deposition (ded) 107 figure 5: starting position of pitot tube in y axes. 5 results and discussion 5.1. numerical results figure 6 shows the gas flow simulation for condition a. the gas streams do not form a clear convergence point at 10 mm where laser focal point and the substrate is supposed to be located. it can be noticed that upon reaching the substrate, the gas flow velocity is approx. 7 m/s, which can give an idea of what the velocity of the powder would be upon reaching the melt pool at the substrate. although the velocity is not very high and there is no convergence point at 10 mm below the nozzle, deposition is possible with that set of flows. to reduce gas consumption and reduce outlet velocity, condition b was configured using the nozzle minimum flow rate (figure 7). this configuration shows a convergence point at approx. 5.41 mm from the outlet nozzle and a flow velocity at the substrate of approx. 3.14 m/s. this would be a better set of flows because it achieves a convergence point and with lower velocity at the substrate. however, the nozzle flow at 2 l/min could risk the optical system for long deposition times and such condition should never be used in real tests. figure 6: simulation using condition a continuing with reducing the gas flow but avoiding the risk for the optical system, an increase in the gas nozzle and carrier was performed, which was compensated with a reduction in the shielding gas flow, this being condition c, shown in fig 8. the gas velocity of the carrier gas is considerably increased, which gives a coaxial shape to the gas flow and prevents the formation of the convergence point at 10 mm. it was also observed that the velocity of the gas at the substrate is around 7.5 m/s. this is a comparable to condition a. condition d is shown in fig 9 in which one can see a better convergence point at 7.36 mm with velocity of approx. 8.5 m/s at this point and maintained until reaching the substrate. velocity at the substrate is higher than condition b, but still comparable with the others before. j. grass n et al. (2021): international journal of engineering materials and manufacture, 6(3), 102-113. 108 figure 7: simulation using condition b figure 8: simulation using condition c in an attempt to form a clear focal point, an increase in all flows was made. to compensate, a drastic reduction in the gas shield was made to evaluate its behaviour under minimum flow. such simulation is shown in fig 10. in this configuration, high exit velocities were obtained in the carrier, preventing the formation of the convergence point before 10 mm. condition e may cause some sputter in case of deposition. it was also evidenced that when the gas flow shielding is very low, it may lead to oxidation preventing the use for practical depositions. condition f, shown in fig. 11 was intended to reduce the carrier velocity, test the same amount of gas flow in nozzle, and a slight increase the shielding flow. the formation of a focal point below 10 mm was not achieved, but the gas consumption was significantly reduced. the velocity when reaches the substrate is between 2.7 and 4.12 m/s, which can be considered a very low velocity and could offer smooth depositions and improve the process efficiency. however, experimental confirmation will have to be done. numerical and experimental analysis of gas flow in a coaxial nozzle applied to directed energy deposition (ded) 109 figure 9: simulation using condition d figure 10: simulation using condition e figure 11: simulation using condition f j. grass n et al. (2021): international journal of engineering materials and manufacture, 6(3), 102-113. 110 5.2. experimental results figures 12 to 17 shows gas flow measurements in a 3d shape at 0, 2, 4, 6, 8 and 10 mm form the nozzle, performed for condition e. it can be observed that velocity is not uniform around the nozzle. in addition, maximum velocity values are different at extremes. the same pattern was found with increasing distance from the nozzle. besides that, the actual concentration of the gas flow tends to be off centre, at 10 mm by about 1 mm in each axis. figure 12: gas velocity measured at 0 mm from the nozzle figure 13: gas velocity measured at 2 mm from the nozzle numerical and experimental analysis of gas flow in a coaxial nozzle applied to directed energy deposition (ded) 111 figure 14: gas velocity measured at 4 mm from the nozzle figure 15: gas velocity measured at 6 mm from the nozzle figure 16: gas velocity measured at 8 mm from the nozzle j. grass n et al. (2021): international journal of engineering materials and manufacture, 6(3), 102-113. 112 figure 17: gas velocity measured at 10 mm from the nozzle figure 18: a comparison of numerical and experimental gas velocity values at 10 mm distance from the nozzle. some clear differences of velocities comparing numerical analysis (fig. 10) and experimental measurement (fig 17) can be observed. however, both results describe a velocity field with the same shape, i.e., describing a hat top function. flow velocity measurements using a pitot tube, based on the bernoulli equation is more appropriate for flows with higher reynolds number (16). in low reynolds number, the viscosity has a strong effect on the flow pattern, therefore limiting the use of the bernoulli equation. however, this equation is based on an invaluable model, which makes these measurements sufficient for the description of velocity fields (17). the major differences between cfd and experimental results, can also be due to calibration errors, taking into account that it had not internal aspect ratio diameters, a possible bad location of the static pressure intake and the difference in the densities air-argon presents in outlet coaxial nozzle, could cause errors in the measurements. such result indicates that cfd computational models can be used for describing gas flows behaviour at the exit of coaxial nozzles and, therefore, can be a valuable tool for improving nozzle efficiency in ded processes. 6 conlsusions a cfd model was developed and used for analysing gas flows in a 3-channel coaxial nozzle applied to ded process. different gas flow sets were simulated. an experimental work was also carried out to compare simulated and experimental flow velocities. from all those studies the following conclusions were possible: • cfd analysis indicated that gas flows are sensitive parameters and they may affect the deposition quality and process efficiency. small variations in the inlet gas parameter, significantly affect outlet velocities and can drastically gas flow field, particularly focal point formation and carrier speed at the substrate. • it was found that condition a (fig. 6) offers an excellent set of gas flow with a focal point and relatively low velocity at the substrate. gas consumption is slightly high and could be lowered. • condition b (fig 7) showed some advantages in terms of gas consumption and focal point formation, but it is not recommended because optical system could suffer in long time depositions. numerical and experimental analysis of gas flow in a coaxial nozzle applied to directed energy deposition (ded) 113 • regarding all the other conditions tested, it can be stated that it is not recommending using a shield gas lower than 8 l/min for a height deposition of 10 mm, or higher. shield outlet velocity is easily affected by the carrier gas flow creating turbulence and it may not reach the substrate with sufficient speed to produce the expected protective atmosphere. • although experimental velocity values were higher than those obtained from cfd simulation, the speed fields were similar indicating the same tendency. bearing that in mind, cdf can be a valuable tool for studying and improving nozzle designs and the ded process as a whole. acknowledgement this study was financed in part by the coordenação de aperfeiçoamento pessoal de nível superior – brasil (capes) – finance code 001; são paulo research foundation (fapesp); laboratory for advanced processes and sustainability (lapras). references 1. gebhardt a, kessler j, thurn l. basics of 3d printing technology. in: 3d printing [internet]. münchen: carl hanser verlag gmbh & co. kg; 2018. p. 1–32. available from: https://www.hanserelibrary.com/doi/10.3139/9781569907030.001 2. astm. standard terminology for additve manufacturing technologies. astm int. 2013 sep 9; 3. kamal m, rizza g. design for metal additive manufacturing for aerospace applications. in: additive manufacturing for the aerospace industry [internet]. elsevier; 2019. p. 67–86. available from: http://dx.doi.org/10.1016/b978-0-12-814062-8.00005-4 4. saboori a, aversa a, marchese g, biamino s, lombardi m, fino p. application of directed energy depositionbased additive manufacturing in repair. appl sci. 2019;9(16). 5. vilar r. laser cladding. j laser appl [internet]. 1st ed. 1999 apr;11(2):64–79. available from: http://lia.scitation.org/doi/10.2351/1.521888 6. lin j. numerical simulation of the focused powder streams in coaxial laser cladding. j mater process technol [internet]. 2000 sep;105(1–2):17–23. available from: https://linkinghub.elsevier.com/retrieve/pii/s0924013600005847 7. kovalev ob, zaitsev a v., novichenko d, smurov i. theoretical and experimental investigation of gas flows, powder transport and heating in coaxial laser direct metal deposition (dmd) process. j therm spray technol [internet]. 2011 mar 21;20(3):465–78. available from: http://link.springer.com/10.1007/s11666-010-9539-3 8. zhu g, li d, zhang a, tang y. numerical simulation of metallic powder flow in a coaxial nozzle in laser direct metal deposition. opt laser technol [internet]. 2011 feb;43(1):106–13. available from: http://dx.doi.org/10.1016/j.optlastec.2010.05.012 9. koike r, takemura s, kakinuma y, kondo m. enhancement of powder supply efficiency in directed energy deposition based on gas-solid multiphase-flow simulation. procedia cirp [internet]. 2018;78:133–7. available from: https://doi.org/10.1016/j.procir.2018.09.061 10. koruba p, wall k, reiner j. influence of processing gases in laser cladding based on simulation analysis and experimental tests. procedia cirp [internet]. 2018;74:719–23. available from: https://doi.org/10.1016/j.procir.2018.08.025 11. ferreira e, dal m, colin c, marion g, gorny c, courapied d, et al. experimental and numerical analysis of gas/powder flow for different lmd nozzles. metals (basel). 2020;10(5):1–20. 12. wendt jf, anderson jd, degroote j, degrez g, dick e, grundmann r, et al. computational fluid dynamics [internet]. wendt jf, editor. computational fluid dynamics. berlin, heidelberg: springer berlin heidelberg; 2009. 1–332 p. available from: http://link.springer.com/10.1007/978-3-540-85056-4 13. plm.automation.siemens. meshing [internet]. 2020. [cited 2020 jul 25]. available from: https://documentation.thesteveportal.plm.automation.siemens.com/starccmplus_latest_en/index.html?param =hw9f1&authloc=https://thesteveportal.plm.automation.siemens.com/authoriseredirect#page/starccmp %2fguid-112029fc-12e0-426f-85fc-4198de68a414.html%23 14. plm.automation.siemens. trimmed mesher [internet]. 2020 [cited 2020 jul 25]. available from: https://documentation.thesteveportal.plm.automation.siemens.com/starccmplus_latest_en/index.html#page/s tarccmp%2fguid-db165a77-56ad-4854-a970-c84bf90b68ad.html%23 15. ferziger jh, m.peric. computational methods for fluid dynamics. third, rev. berlin; heidelberg; new york; barcelona; hong kong; london; milan; paris; tokyo: springer berlin heidelberg; 2002. 16. spelay rb, adane kf, sanders rs, sumner rj, gillies rg. the effect of low reynolds number flows on pitot tube measurements. flow meas instrum [internet]. 2015;45:247–54. available from: http://www.sciencedirect.com/science/article/pii/s095559861500062x 17. boetcher sks, sparrow em. limitations of the standard bernoulli equation method for evaluating pitot/impact tube data. int j heat mass transf [internet]. 2007;50(3):782–8. available from: http://www.sciencedirect.com/science/article/pii/s0017931006001396 international journal of engineering materials and manufacture (2019) 4(2) 59-65 https://doi.org/10.26776/ijemm.04.02.2019.03 m. kh th e alazemi 1 and a. k. m. mohiuddin 2 1 department of manufacturing and materials engineering 2 department of mechanical engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: mohiuddin@iium.edu.my reference: alazemi, m. kh. th. e. and mohiuddin, a. k. m. (2019). construction project in kuwait international airport cargo city: issue of conflict management. international journal of engineering materials and manufacture, 4(2), 59-65. construction project in kuwait international airport cargo city: issue of conflict management mohammed kh th e aalazemi and a k m mohiuddin received: 24 april 2019 accepted: 15 june 2019 published: 20 june 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract conflict in construction projects seems to be the reasons of high project cost, project delays, lower productivity, loss of profit, damage business relationships and dispute on the team. effective functioning requires commitment of at least several key personnel to get the venture runs effectively even with the presence of distinctive intrigue. when individuals of fluctuating foundation meet-up on a task group, strife is unquestionably present there. as the individuals inside the venture alliance are interrelated, intrigue impacts and clashes are not uncommon within their activities. this study therefore sought to discover the causes of these conflicts in the construction sector and the manner by which these conflicts can be effectively resolved. here a quantitative survey-type study has been carried out on construction project in kuwait international airport for conflict management. one hundred eighty eight questionnaires have been distributed, fourteen of them have been lost and eleven of them have not been answered. the responses of 163 participants have been analyzed with the statistical package for social scientists (spss). this study showed that the general causes of conflict are predominantly create conflicts. inadequate communication and contradicting instructions according to the results are the leading causes of conflict. the effects of conflict on project mainly include project delays, ineffective construction and reduced productivity, etc. the findings revealed that participants in the study prefer the role of collaborating and compromising styles in solving conflict of on-site construction. every project starts and ends with communication, so communication is the life wire of all construction projects. to cure the communication problem, the study suggests strategies like team meeting discussions, site review meetings, and project status reporting platform to manage the conflict and reduce the dispute of construction projects. keywords: construction project, dispute, conflict, conflict management 1 introduction the construction comprises of different members and specialists do interrelate task of an undertaking. what's more, when these individuals from the project group, there are potential for conflict and conflict circumstances do emerge. one of the key factors that predicts peril or undermines construction of open projects is conflict between task colleagues or members (gardener et. al., 1995; fenne et. al., 1997; emit, 2013). this is predominantly because of their various foundation, preparing, aptitudes, standards to work and part's point of view (duestch, 1973). conflict remains a test in the construction business (kassab et. al., 2010) till today. this specific part or area assesses existing literary works on the significance of contention, conflict types, refereeing styles or methodologies and models in the construction projects. conflict can be increasingly comprehended in the event that it is well-considered as a dynamic procedure containing a succession of contention scenes. pondy (1967) recognized five phases of contention scenes in particular; inactive conflict, saw assignation, sensed fight, show conflict, and engagement repercussions. pondy advance that, each contention scene starts with conditions considered by certain contention possibilities and can be believed of as a slow heightening to a condition of turmoil by an exposed conflict or animosity as a peak of a contention scene. nonetheless, that ensures not mean each contention scene should go over each phase to exposed hostility. gatherings construction project in kuwait international airport cargo city: issue of conflict management 60 to the contention may not see a possible engagement, the contention might be settled before threats cessation out (vaaland and hakansson, 2003). for good comprehension of contention marvels, every one of the five scenes is to be examined. thus, for kuwaiti construction projects, alsabah (1997 p.2) claim as a articulation by the contractual worker that he trusts that he is qualified for additional payment or additional opportunity to finish the works. such payment might be as recommended under a proviso of the agreement, or emerge from a break of the agreement or kuwaiti civil code (kc code)'. in this exploration, alsabah's definition has been picked as the most reasonable one for the kuwaiti construction industry and the idea of cases in this area. building exercises are a vital part of each type of life. consider houses, schools, emergency clinics, malls, and so forth, all are results of structure exercises. also, building exercises devour different assets that by their tendency are rare. accordingly, it is imperative that construction missions are carried out in the most productive and practical way. conflicts in structure projects are refered to by various creators, for example, langford (1992), walker (1996), fenn et al (1997), ambrose and tucker (1999), kumaraswamy (1998), loosemore et al (2000), maiti (2018). gamil and rahman (2018); as one of the components that weaken the development and achievement of the mission. the examination adds to the exploration and practice networks, by tending to concerns on which disputes happen and their causes in structure extends in kuwait international airport cargo city and in kuwait. methodologies and instruments for the executives and avoidance of contentions in structure extends in kuwait are proposed. the aftereffects of the investigation gives extra learning required by customers/lenders, project directors, designers, engineers, amount questionnaires, temporary workers and different partners in the administration of structure projects. the data consequently contained in the investigation may similarly be utilized as bases for building up a charter or a framework for controlling conflicts in the construction of open structures and other open related works by the state. 2 research phiisophy a method of research that combine qualitative or quantitative called the mixed method has been applied in this research. literature review will be done to accumulate a list of disputes, elements instigating them and prevailing clash resolve methods as self-governing variables. then confirmation of self-governing variables recognized from collected works examination in the context of construction manufacturing units in kuwait. and as with basic or primary data or information, questionnaires, observations and interviews will be employed. data previously gathered on construction conflict will also be consulted to shore up the primary data that will be collected. sample of clients, contractors and consultants will therefore be interviewed to verify the variables. since interview is one of the qualitative approaches that are suitable in recognizing the main variables. research variables are as follows:  age of the workers in the construction company in kuwait.  education level for employees in construction projects.  the specialization for managers and engineers in construction projects.  job description for employees in construction projects. 2.1 objectives of the study the purpose of this study is to explore the existing conflicts management approaches, and examine their applicability in building projects in kuwait international airport cargo city. to find solutions to the overall objective, the research endeavor to (i) investigate the main reasons, signs, and symptoms of the conflict in the field of the construction projects in kuwait international airport cargo city and (ii) study the most common methods that used to manage and control conflict management of construction project in kuwait international airport cargo city. 2.2 research hypothesis the research was built based on tow type of hypothesis, as follows:  the conflict of construction of project effect on the performance of the receiving construction projects.  conflict of construction project effect on the relationship between time, cost as well as quality.  the effects of conflict of construction project have some organizational consequences for instance, voluntary turnover, low levels of performance, lack of creativity, responsibility, accident, and low amount of job involvement.  even a small conflict can affect severely on the performance of workers such as motivating workers and engineers. 2.3 research questions the following questions will be posed to achieve the objectives of the study. 1. is there an impact of conflict in construction projects in kuwait international airport cargo city? 2. what are the conflict management systems used in construction projects in kuwait international airport cargo city? 3. what management approaches are used in resolving conflict in public building projects and their effects on project success in kuwait international airport cargo city? alazemi and mohiuddin (2019): international journal of engineering materials and manufacture, 4(2), 59-65 61 3.1 the construction sector in kuwait kuwait has been distinguished by fast construction being developed in the course of the most recent thirty years, with exceptional accomplishments in different fields: financial, social, instructive and construction. the kuwaiti government has considered the construction business to be one of its prime contemplations, with the most astounding need among non-oil areas. the quick increment in construction of the populace made it basic for the administration to focus on construction activities, and the construction industry, along these lines, possesses an essential spot in the monetary activities of the country (alsabah, 1997). kuwait‘s construction industry sector has been hit by a combination of factors in the last quarter of 2016, resulting in a decrease in forecasted growth to 0.65 billion kuwaiti dinars. falling oil prices and new opec quotas are set to reduce petroleum production, which accounts for 80% of government revenues. meanwhile the global acknowledge emergencies, along with local political uncertainty, is greatly impacting investor confidence in kuwait and these factors have led to an exodus of ex-pat’workers and mean that some infrastructure projects may be cancelled or postponed until confidence returns. in kuwait (in view of directorate of specialists standards and conditions) the way toward settling debate is relies upon the understanding between the parties in the agreement, for instance if parties have referenced that they will settle any question under the kuwaiti common law at kuwaiti courts which is prosecution step. some item else, the agreement gatherings can pick arbitration which ought to be referenced in the agreement if the two gatherings needed to determine their question with mediator; the decision of the arbitrator is binding with no further understandings. by utilizing standard types of agreement, a more pleasant parity might be accomplished if there should arise an occurrence of question. the interviewees ensured that the improving of question goals system in kuwait is an interest to recover the construction industry. nonetheless, improving the procedure of debate goals isn't as simple as including a provision in the agreement. concentrate the causes, components and roots of question in construction projects ought to be done before questionnaire the technique for construction. from the interviewees perspective, the deficiency of involvement in question goals with adr for construction extends in kuwait just as the need in preparing and instruction, are the huge bother issues against the utilization of adr to determine construction industry debate. 3.2 research sample and research population the research population in this project is all the employees in company in kuwait. the number of employees in this company and owner is very large, so the sample of questionnaire is random sample represented by the (5%) of the workers in this company (including any worker was present during the distribution of the questionnaire). a 144 questionnaires have been distributed, 14 of them have been lost, and 11of them have not been answered. the questionnaire will be built to make an assessment to the effect of conflict on the performance of the workers as well as to determine the main reasons of conflict of construction as well as to establish the level and extent of the conflict management of construction project. the target group in this part is the workers in the construction projects. the variety among the workers is due to the age, gender, education level and position. this information will be answered by each participant in the questionnaires at the beginning of the study under the (personal information) headline. the questionnaire will be distributed randomly to almost every worker and engineering and project manager and in the shift that will be working during the researcher’s visit. the visits and distribution process will be permitted by the management. every participant will be asked to willingly to answer the questions under the supervision of the researcher, where any question or unclear ideas will be clarified. after completing the questions, every worker will be asked to return them to the researcher. the type of questionnaire is a quantity survey, where the questions are multiple choice from five scale questionnaire (strongly agree, agree, uncertain, disagree and strongly disagree), where these choices determine whether the statement is true or not. 3.3 types of conflicts conflicts may be well-thought-out in three measurements; level one may be seen as man-to-man struggle that is the contention that occurs inside the specific. tier two is social encounter the contention proficient among persons in a comparative get-together or unit for example colleagues, level mates, unit people, etc. such conflicts exist at whatever point people impart or get self-possessed to realize a mutual objective or aim. tier three is the intra-amass engagement, the contention among social affairs in a comparable affiliation, gathering or bearing. the social and intra-cluster conflicts can moreover be arranged into three sorts: the relationship, task and method encounters (bowen, 2017; simmons and peterson, 2000; jackson et. al, 2008). association or energetic encounter is an impression of social inconsistency and normally consolidates weight, unsettling influence, and ill will among gathering people (simmons and peterson, 2000). different examinations done by specialists, for instance, gladstein (1984), wall and nolman (1986), bowen (2018), jahnssen et al., (1999) alluded to in simmons and peterson, record the undesirable things of affiliation engagement on gatherings and affiliation fulfilment and obligation. association conflict contrarily influences cooperative choice quality in three different ways. to begin with, it limits data preparing capacity of the groups in light of the fact that the group individuals invest a large portion of their time and vitality concentrating on one another instead of on the group issues. second, it limits amass individuals' subjective working by expanding their pressure and tension dimensions and third, it supports adversarial or evil attributions for other gathering individuals' conduct, which can make an inevitable outcome of common threatening vibe and conflict acceleration. construction project in kuwait international airport cargo city: issue of conflict management 62 as indicated by simons and peterson (2000) various analysts have discovered that task conflict can prompt expanded fulfillment with the cooperative choice and a longing of individuals to remain in the gathering, and furthermore have appeared cross connection between the two types of conflict. researchers have built up that endeavors to invigorate possibly advantageous errand conflicts run a generous danger of activating inconvenient affiliation encounter. simmon and peterson recommend two conceivable clarifications; first they fight that, task conflict prompts affiliation engagement through a procedure of misattribution. gathering individuals always translate the conduct of other gathering individuals they construe goals, evaluate whether the wellspring of the conduct they see is interior or outer, and questionnaire the culmination and precision of the conflicts made by others. at the point when this attribution procedure indicates individual connection or concealed motivation, at that point mission conflict activates affiliation conflict. the seemingly unanticipated causes of conflict are linked with project commencement and definition. these emanates from unrealistic expectations, misunderstandings, absence of cohesion, communications, modification of scope, insufficient contract records (lu, 2017; blake dawson waldron, 2006). however, hellriegel (1986) cited in femi (2014) classifies conflict into levels based on interaction between persons or human functioning within and outside the group or team. these groups of conflict are the intrapersonal conflict, the interpersonal conflict, the intragroup conflict and the intergroup conflict. the intrapersonal level which he states thus occurs to an individual in respect of the conflict of the mind, a state of paradox. on the other hand the interpersonal conflict is a form of conflict which occurs between two or more individuals has opposing views, goals, interest, attitudes, or values among other items. in fact, literature has it that, interpersonal conflict is one of the top occupational job stressor (liu, 2002). 3.4 improving conflict management process in kuwait state kuwait has been distinguished by rapid growth in construction over the last thirty years, with remarkable achievements in various fields: economic, social, educational and construction. the kuwaiti government has considered the construction industry to be one of its prime considerations, with the highest priority among non-oil sectors. the rapid increase in growth of the population made. it is essential for the government to concentrate on construction activities, and the construction industry, therefore, occupies a very important place in the economic activities of the country (alsabah, 1997). kuwait has been recognized by fast construction being developed in the course of the most recent thirty years, with wonderful accomplishments in different fields: monetary, social, instructive and construction. the kuwaiti government has viewed the construction business as one of its prime contemplations, with the most noteworthy need among non-oil segments. the fast increment in construction of the populace made it fundamental for the legislature to focus on construction exercises, and the construction business, hence, involves a vital spot in the monetary exercises of the nation (alsabah, 1997). kuwait's construction industry part has been hit by a blend of components in the last quarter of 2009, bringing about a decline in gauge construction to 0.65 billion kuwaiti dinars. falling oil costs and new opec standards are set to lessen oil creation, which represents 80% of government incomes. in the meantime, the worldwide acknowledge emergency, alongside neighborhood political vulnerability, is enormously affecting speculator trust in kuwait and these elements have led to a mass migration of ex-pat' specialists and imply that some foundation projects might be dropped or delayed until certainty returns. by 2013, the construction business' value is set to achieve 0.78 billion kuwaiti dinars (kd). the nation's construction industry value construction has descended insignificantly from 2.67% construction in 2008, to 2.28% in 2009, and is relied upon to fall further to 1.03% in 2010. kuwait's construction industry construction will recuperate somewhat by 2013, with construction of 1.60% expected by at that point. there are as of now indications of postponements in a few substantial framework projects, outstandingly the $7 billion metro framework for kuwait city, which is required to be deferred by year and a half, and the broad al-zour refinery which might be overhauled. 4 results and analysis statistical package for social scientist (spss 16.0) and microsoft excel were used in analyzing the collected data. although a number of software thus exist for such research computations, the researcher’s insight in spss and excel made the two techniques the researcher’s favored picks. the spss was used to perform mean & median & stander deviation & frequencies importance indices were performed using microsoft excel including the charts that are generated to depict findings. the package was applied in generating descriptive statistics. and a microsoft excel was also applied in generating relative important indices and chart to back findings. mean values derived from the measurement of the items and the relationship between the variables are established. as previously mentioned, this questionnaire will be comprised of 45 statements categorized into four parts. 188 questionnaires have been distributed, 14 of them have been lost and 11 of them have not been answered. this sample is considered large sample. this part represents mean, median frequency distribution as well as standard deviation for the gender of the participants in the questionnaire. where “valid” is represents the acceptable data in order to analyze process. in addition, “missing” is represents the data that have no value. the table 1 explains that the average value of the participant answers to gender type is mean =1.3, also, the most frequent value of the gender type, and median value equal to (1.00). in addition to the value of standard deviation is equal to (0.4599). the table 5.2 as well as the fig 5.1 below illustrates that all of participants were male 114 contribute 69.9%, and female 49 who contribute with alazemi and mohiuddin (2019): international journal of engineering materials and manufacture, 4(2), 59-65 63 30.1%. this part represents mean, median frequency distribution as well as standard deviation for the age of the participants in the questionnaire. where “valid” is represents the acceptable data in order to analyze process. in addition, “missing” is represents the data that have no value. table 2 and table 3 illustrates that participants' gender (male, female) and ages ranging from (25 to 65 years) who contribute with 100%. where “valid” is represents the acceptable data in order to analyze process. also, it can be considered a good approximation for expecting subsequent data points, also, the most frequent value of the position or answer that occurs, and median value equal to (1.0000) that is considered the middle value of participant’s answers. the median is particularly useful when separating data into two parts. in addition to the value of standard deviation is equal to (.64689), which provides an idea of how close the entire group of participant’s answers is to the value of mean. data groups with a small value of standard deviation have tightly grouped, accurate data. data groups with large value of standard deviations have data spread out over a wide range of values. table 4 illustrates that the total of participants are 163, and their job divided as the following; 108 of them were owner, who contribute with 66.3% and 41 of them were 41 and who contribute with 25.2% and 14 of them contractor and who contribute with 8.6%. table 6 explains that the average value of the participant answers to experience” that is considered the average of data that obtained by dividing the sum of participant’s answers by the answers number. also, it can be considered a good approximation for expecting subsequent data points, also, the most frequent value of the experience or answer that occurs. table.1: possible causes of conflicts in construction by various authors authors date causes of conflict wu, y., li, h., & dan 2018 pre-award design, change orders, pre-construction challenges and quality assurance. bowen et. al. 2018 payment and budget; delay and time; budget performance; negligence; administration tipili et. al., 2014 inadequate communication li et. al. 2012 mismatch in people’s perception and expectation. lu, w., & wang 2017 delay; site access delay, delay in running bill, delay in decision by owner. unrealistic expectation; scope definition not clear, excessive change orders. acharya & lee, 2006 differing site condition, errors and omissions in design, local people obstruction, excessive quantity of works, difference in change order evaluation, double meaning in specification. mgbekem 2004 task dependence, scarce resources, goal incompatibility, communication failures, poorly design reward system, individual difference. yiu & cheung 2007 delay; site access delay, delay in running bill, delay in decision by owner. unrealistic expectation; scope definition not clear, excessive change orders. kumaraswamy 1997 changes of conditions, changes of scope, unrealistic expectations, communications, delays, unpredictability, contract document. rhys jones. 1994 poor communications; inadequate design; economic environment; poor management; unrealistic tendering; inadequate contract drafting; poor workmanship; adversarial culture. conlin et. al. 1996 payment and budget; delay and time; budget performance; negligence; administration. table 2: participants gender frequency percent valid percent cumulative percent valid male 114 69.9 69.9 69.9 female 49 30.1 30.1 100.0 total 163 100.0 100.0 table 3: participants' ages ranging from (25 to 65 years) frequency percent valid percent cumulative percent valid 25 to 28 years 52 31.9 31.9 31.9 28 to 36 years 38 23.3 23.3 55.2 36 to 40 years 51 31.3 31.3 86.5 40 to 50 years 18 11.0 11.0 97.5 55 to 65 years 4 2.5 2.5 100.0 total 163 100.0 100.0 construction project in kuwait international airport cargo city: issue of conflict management 64 table 4: total of participants are 163, and their job divided frequency percent valid percent cumulative percent valid owner 108 66.3 66.3 66.3 consultant 41 25.2 25.2 91.4 contractor 14 8.6 8.6 100.0 total 163 100.0 100.0 table 5: experience frequency percent valid percent cumulative percent valid 2 to 5 years 63 38.7 38.7 38.7 5 to 8 years 34 20.9 20.9 59.5 8 to 10 years 16 9.8 9.8 69.3 10 to 15 years 16 9.8 9.8 79.1 above 15 years 34 20.9 20.9 100.0 total 163 100.0 100.0 table 2: position frequency percent valid percent cumulative percent valid site engineer 33 20.2 20.2 20.2 project manager 24 14.7 14.7 35.0 manager department 1 .6 .6 35.6 administrative 60 36.8 36.8 72.4 technical staff 45 27.6 27.6 100.0 total 163 100.0 100.0 5 conclusions the study was gone for investigation the idea of expert conflicts inside the development conflict management of construction project in kuwait international airport. the survey showed that among the various causes of conflicts in the construction project of kuwait international airport are the following: 1. delays in time for project completion 2. type of procurement method adopted 3. conflicting commitment of project managers 4. absence of qualified personnel in key positions 5. differences in views among stakeholders 6. deficiencies in designs 7. unrealistic expectations from clients 8. dissatisfaction of work progress of main contractor by architect/engineer 9. limited resources 10. lack of team spirit among project team members 6 recommendations it is suggested that, venture supervisors ought to be presented to broad preparing for them to gain aptitudes fundamental to working successfully in any condition. the preparation will assist them with developing proper methodologies and working styles to keep away from strife circumstances which may prompt cases and subsequently to debate and claims. besides peace making ought to be presented as a component of project chiefs preparing inside and outside the ventures. undertaking management administrative body ought to be built up to screen and direct exercises of project management as this will improve venture the board work on preparing and retraining of project managers. it is additionally suggested that all partners ought to be taught on their rights and commitments. with this, delays in venture culmination, conflicting duty, unrealistic clients‟ desire and the conduct of the two contractual workers and sub-temporary workers ought to be tended to which can go far to diminish or maintain a strategic distance from such conflicting circumstances. it is additionally prescribed that, venture supervisors ought to improve correspondence channels; construct a feeling of trust among undertaking colleagues, build up aggregate duties and advance their insight in human connection so as to lessen conflicts in tasks intelligently to enhance venture achievement. alazemi and mohiuddin (2019): international journal of engineering materials and manufacture, 4(2), 59-65 65 references acharya, n., lee, y. and im, h. (2006) conflicting factors in construction projects: korean perspective, engineering construction and architectural management, vol. 13(6) p.543-566. alsabah, s.j.a. 1997, construction disputes and claims in kuwait, university of birmingham, school of civil engineering, faculty of engineering ambrose, m.d. and tucker, s.n. (1999); matching a procurement system to client and project needs: a procurement system evaluator, cab w55 & w65 joint triennial symposium on customer satisfaction, cape town, south africa anderson jr., l. l. and polkinghorn, b. (2008), managing conflict in construction megaprojects: leadership and thirdparty principles, conflict resolution quarterly, vol. 26(2), p. 167-198. ban, c. (1995), conflicts in organizations. in r. k. t. yu and m. leung (2001) investigation of construction conflict resolution in hong kong, 17th annual arcom conference university of salford, vol. 1. bowen, p., govender, r., edwards, p., & cattell, k. (2017). the role of after-hours, work-related contact in workto-family conflict and sleep problems experienced by construction professionals. in arcom 2017 (pp. 360-369). association of researchers in construction management (arcom). bowen, p., govender, r., edwards, p., & cattell, k. (2018). work-related contact, work–family conflict, psychological distress and sleep problems experienced by construction professionals: an integrated explanatory model. construction management and economics, 36(3), 153-174. charehzehi, a., chai, c., md yusof, a., chong, h. y., & loo, s. c. (2017). building information modeling in construction conflict management. international journal of engineering business management, 9, 1847979017746257. clegg, s. (1992) contracts cause conflict, in fenn, p and gameson, r. (eds.),construction conflict: management and resolution, chapman & hall, london pp. 128-144 colledge, b. (2005) relational contractingcreating value beyond the project. lean construction journal, vol. 2(1) p. 30-45 dada, m. o. (2013) conflicts in construction projects procured under traditional and integrated systems: a correlation analysis, international journal of construction supply chain management, vol. 3(1) p.1 -15. femi, o. t (2014) causes and effects of conflict in the nigerian construction industry. international journal of technology enhancements and emerging engineering research, vol. 2(6). femi, o. t (2014) causes and effects of conflict in the nigerian construction industry. international journal of technology enhancements and emerging engineering research, vol. 2(6). fenn, p, lowe, d and speck, s. (1997), conflict and dispute in construction. construction management and economics. vol. 15, p. 513-518. gamil, y., & rahman, i. a. (2018). identification of causes and effects of poor communication in construction industry: a theoretical review. emerging science journal, 1(4), 239-247. gardener, p. and simmons, j. (1995) case exploration in construction conflict management, construction management and economics, vol. 13(3), p. 219-234. kassab, m., hegazy, t. and hipel, k. (2010) compromised dss for construction conflict and resolution uncertainty, journal of construction engineering and management, vol. 136(12) p. 1249-1257 kumaraswamy, m. (1997) common categories and causes of construction claims, construction law journal, vol. 13(1), p. 21-34. kumaraswamy, m. (1998): consequences of construction conflict: a hong kong perspective, management in engineering journal, 14, 66 – 74. langford, et. al., (1992) contingency management of conflict; analysis and solution. in p. fenn and r. gameson (eds.). construction conflict management and resolution. london; e & fn spon, p.64-71. lee, k. l. (2011), an examination between the relationships of conflict management styles and employees‟ satisfaction, international journal of business and management, vol.3 (9), p. 11 -25. maiti, s., & choi, j. h. (2018). investigation and implementation of conflict management strategies to minimize conflicts in the construction industry. international journal of construction management, 1-16. tabassi, a. a., abdullah, a., & bryde, d. j. (2019). conflict management, team coordination, and performance within multicultural temporary projects: evidence from the construction industry. project management journal, 50(1), 101-114. tabassi, a. a., bryde, d. j., abdullah, a., & argyropoulou, m. (2017). conflict management style of team leaders in multi-cultural work environment in the construction industry. procedia computer science, 121, 41-46 tunji-olayeni, p. f., afolabi, a. o., adewale, b. a., & fagbenle, o. i. (2018). questionnaire data set on work-life conflict of women in the construction industry. data in brief, 19, 921-924. wu, g., wu, y., li, h., & dan, c. (2018). job burnout, work-family conflict and project performance for construction professionals: the moderating role of organizational support. international journal of environmental research and public health, 15(12), 2869. international journal of engineering materials and manufacture (2018) 3(4) 200-207 https://doi.org/10.26776/ijemm.03.04.2018.04 m. murthy , k. m. babu and p. m. jebaraj department of mechanical engineering b.m.s. college of engineering bull temple road, bengaluru karnataka, india-560019 e-mail: madhavmurthy.mech@bmsce.ac.in reference: murthy, m., babu, k. m. and jebaraj, p. m. (2018). impact of constraint conditions and cutouts on natural frequency of glass fibre reinforced plastic composite. international journal of engineering materials and manufacture, 3(4), 200-207. impact of constraint conditions and cutouts on natural frequency of glass fibre reinforced plastic composite madhav murthy, kayala mallikharjuna babu and peter martin jebaraj received: 12 september 2018 accepted: 03 november 2018 published: 01 december 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract majority of the activities of a human being is associated with vibrations of one or other form. application of vibrations can be found from a simple example like listening to music to challenging ones like design of complex machines and structures. design of any system will not be rugged if it does not consider vibrations and its effects. the energy dissipated per cycle can be understood as damping. presence of damping in a structure is represented by damping factor or damping ratio. fibre reinforced plastic composites are a class of materials made from matrix and reinforcement. matrix can be a resin system and reinforcement is usually fabric made of glass, carbon or aramid. the vibrating mechanical system causes resonance resulting in failure of machine components. by knowing the natural frequency and changing it from the range of operating machine member, resonance phenomenon could be avoided. this work focuses on finding the damping ratio and natural frequency of s glass fibre reinforced polymer composites through harmonic & modal analysis both by experimental method and fem analysis for bare plate, plate with rectangular cutouts and plate with circular hole. the reduction in natural frequency and increase in damping corresponds to a change in stiffness and damping of the system. these changes are attributed to freeness of the system and introduction of cutouts in the laminate. keywords: vibrations, damping factor, glass fibre reinforced composites, natural frequency 1 introduction man became interested in vibration when he created the musical instruments like drums, whistles and other musical instruments. since then, philosophers and musicians came up with the understanding of sound and sounds, which were used in creation of various musical instruments and were passed from generation to generation [1]. the motion that repeats itself after an interval of time can be called oscillation or vibration. the swinging of a simple pendulum, motion of a tuning fork and the spring balance are typical examples of vibration. many a human activities involve sound and vibration in one or the other form. the theory of vibration deals with the study of oscillatory motion of bodies and forces associated with them. vibration can be desirable or undesirable. sound and vibration studies are interrelated. the types of vibration are free, forced, damped and undammed. 1.1 loss factor when a structure is excited, the vibrations in the structure do not last forever and it therefore dampens out. the ability of structures, which dissipates vibrational energy, is an important parameter of a system called damping which is quantified as damping ratio (ζ) or loss factor (η) [2].damping can be understood as the energy dissipated per cycle. when there is a presence of damping in a structure, it is generally represented by damping factor or damping ratio and when it is defined for a specific mode, it is known as modal damping factor. a structure can have many natural frequencies. for a design to be reliable, estimation of damping becomes important. loss factor estimation is straightforward unlike other parameters like stiffness and mass. it is often evaluated during experimentation. inconsideration of loss factor may not lead to a sound design. hence, a suitable damping is to be provided for increasing the weight, whereas overestimation of loss factor may lead to unwanted impact of constraint conditions and cutouts on natural frequency of glass fibre reinforced plastic composite 201 vibrations and sometimes breakdown of the structure prior to the designed life. some of the common issues associated with loss factor estimation are to understand the limits and requirements in each method of loss factor estimation. it is crucial, as there is no single method suited for all situations [3]. most techniques do not accurately estimate high loss factors, mostly because of insufficient/incorrectness of data provided. while taking measurements, the positioning of excitation point and sensors is vital since multiple input-output locations of the structure are involved. a structure should never be excited at a node line as this may cause rigid body response. it is also important not to measure response from any point on node line [4, 5]. for simulating a continuous system efficiently and removing spatial effect from measurements, long sets of time history of responses needs to be recorded and analysed from multiple locations, which best be randomly chosen. in cases where multiple input and output locations are involved, slope fitting can prove to be another challenge. when a great number of slope fits are required to be performed, human error is unavoidable which may lead to inaccuracy of results. therefore, an automated slope fitting algorithm is recommended. to avoid any probable biased error, visual inspection helps to understand the decay curves for all slope fits [6]. 1.2 half power bandwidth method it is a frequency domain method used for estimation of loss factor. the estimation of loss factor is carried out using frequency response functions. the expression of damping factor is given by ζ= (ωn2ωn1)/2 ωn where ωn is the natural frequency, ωn2, ωn1 are half power points and the difference of these is called the bandwidth. the objective of this work is to estimate the damping factor of glass fibre reinforced composite plates (laminates) with no cutouts, circular cutouts and rectangular cutouts and varying boundary conditions [7, 8]. the boundary conditions considered in this work are clamped-clamped-clamped-clamped (cccc), clamped-clamped-clamped-fixed (cccf) and clamped-fixed -clamped-fixed (cfcf). the laminates were fabricated using resin transfer moulding (rtm) method. the matrix was the combination of resin and hardener in the ratio of 1:10. the matrix and reinforcement used in this study are epoxy ly556 with hy951 as hardener and bidirectional s glass fibre as the reinforcement. the laminate was cured at room temperature. the machining of the laminates was carried out in abrasive water jet machining centre [9, 10]. the validation of experimental and fea values of damping factor and natural frequency results were carried out. fast fourier transforms (fft’s) were obtained from the experimental studies. the boundary conditions used for experiments to determine natural frequencies and fea were the same. there was a variation between the fea and experimental results (analytical vs experimental) which could be due to the mesh quality, section of the element and accuracy of boundary conditions, which should imitate the experimentation condition for validation of fea results. all the plates used for experimentation are fabricated using s glass fibres with the epoxy resin ly556 and the hardener hy951. the composite laminate was fabricated by resin transfer moulding process. the plate dimensions were chosen as 420mm x 210mm x 2mm for the final laminate size. the numbers of layers of reinforcements used are 8 in addition to resin contributing to the rest of thickness and resin-hardener in the ratio of 1:10. the workpiece and experimental setup is shown in figure 1 and figure 2 respectively. figure 1a, 1b & 1c indicates the laminates fabricated and machined to the dimensions and 1b -1c have rectangular and circular cutouts for testing the damping and six modes of frequency. 2 methodology 2.1 experimental procedure the measurement of vibration characteristics depends on various factors such as position of exciter to excite the structure, placement of an accelerometer, and clamping of the plate etc. the brief procedure for the experimentation is as follows. the plate is clamped firmly after the dimensions are measured for all the configurations (cccc, cccf & cfcf) and smearing of wax on the uniaxial accelerometer is carried out before placing the accelerometer on the vibrating structure. the structure is then excited by sine sweep method. then the response of structure is recorded using data acquisition system and compatible software. a b c figure 1:tthe workpiece (a) bare plate, (b) late with rectangular cutout, and (c) plate with circular cutout after the data acquired it is exported to an fft analyser and read in frequency domain, which shows amplitude response corresponding to frequency. the amplitude response is as shown in figure 3 in hertz. natural frequencies at various frequencies and intervals of time can be seen in figure 3. murthy, babu, and jebaraj (2018): international journal of engineering materials and manufacture, 3 (4) 200-207 202 2.2 validation using fem approach the finite element analysis for the orthotropic laminates prepared with the above-mentioned boundary configurations is carried out. frequency response curves obtained experimentally and through ansys is shown in the figure 4. quality factor is calculated for all the configurations using half bandwidth technique. in experimental method, frequency response curves are plotted as frequency v/s amplitude. the amplitude obtained experimentally is shown in terms of volts, larger the volts larger is the amplitude. the plate (laminate) response is taken from the analyser and the accelerometer sends the signals to the analyser in the form of volts as can be seen in figure 4. voltage is a direct measure of amplitude. in finite element analysis, the frequency response curve, magnitude of the amplitude can be obtained. highest peak in experimental frequency responses via fft and fe frequency response curves from ansys corresponds to the natural frequency of the structure the s glass frp laminates are used for the vibration analysis. with the fibre and resin composition of 6040% respectively. the plates are subjected to loads such as fatigue, point loads, bending etc. so the plate should have the capability to resist such loads. the table 1 shows the physical properties of the reinforcement. modulus, density and thickness are important parameters for carrying out simulation and experimental studies, which are given in table 1. figure 2: experimental setup with the fixtures figure 3: amplitude response of bare plate with cccc configuration (hz) impact of constraint conditions and cutouts on natural frequency of glass fibre reinforced plastic composite 203 2.3 boundary conditions the orthotropic laminate is studied for different boundary conditions. the clamping is made on the edges of the plate. these three boundary conditions are shown in figure 5. the various boundary conditions studied are cccc (all ends clamped) for a bare plate (i.e., without any cut out), a plate with circular hole or cutout and a plate with rectangular cutout for carrying out further analysis as can be seen in figure 5. the finite element method analysis is considered and obtained for six mode shapes. in this article only the first mode shapes are discussed as shown in figure 6, figure 7 and figure 8. once the meshing is done and the constraints are defined the next step is to carry out the modal as well as harmonic analysis for the orthotropic plates by providing the inputs of the frequency and the obtained results is as shown in figures 6-8. in figure 6, figure 7 and figure 8 nodal solutions are obtained and further analysed. figure 4: plate with circular hole (cccf condition) table 1: properties of s glass bidirectional fabric properties values e1 85gpa e2 3.5gpa e3 3.5gpa ν12 0.2 ν 23 0.2 ν31 0.35 g12 36gpa g23 36gpa g31 36gpa density 1822kg/m3 fabric thickness 0.25mm a b c figure 5: cccc boundary configuration of (a) bare plate, (b) plate with circular hole and (c) plate with rectangular cutout. murthy, babu, and jebaraj (2018): international journal of engineering materials and manufacture, 3 (4) 200-207 204 figure 6: plate with circular hole cfcf condition figure 7: plate with circular hole cccf condition impact of constraint conditions and cutouts on natural frequency of glass fibre reinforced plastic composite 205 figure 8: plate with circular hole cccc condition 3 results and discussions experimentation and validation: the laminates prepared were subjected to dynamic analysis and the natural frequencies were found out. the same are presented for first three modes. finite element analysis for the various laminates of different boundary conditions was carried out and is as shown in table 2. from table 2 one can infer the various frequency values which helps in designing of structures and also for damping studies the bare plate shows reduced natural frequency when the laminate is under cfcf condition as compared to cccc condition in 1st mode, which reveals that freeness in the system reduces the natural frequency of the system. the result holds good for remaining two modes. these results are in agreement with results from fem approach. it can also be seen that there is a substantial increase in natural frequency of laminates with cutouts as compared to that of bare plate. however, there is a little variation in natural frequency among circular and rectangular cutouts. the calculated values of damping for various boundary conditions are as shown in table 3. it can be seen clearly from the graphs as in figure 9 that composite plates with rectangular cutouts have a higher damping followed by composite plate with circular hole. it can also be seen from figure 9 that composite bare plate has got least damping as compared to plate with cutouts. table 2: comparison of natural frequencies from experiment and fem method plates boundary condition 1st mode 2nd mode 3rd mode frequency (hz) frequency (hz) frequency (hz) fem exp fem exp fem exp bare plate cccc 293 310 438 615 664 730 cccf 251 250 334 490 490 730 cfcf 240 225 276 460 375 700 plate with circular hole cccc 405 390 468 440 755 730 cccf 324 315 427 410 517 490 cfcf 320 315 331 350 470 490 plate with rectangular cutout cccc 402 260 460 520 750 760 cccf 323 200 421 420 510 625 cfcf 318 200 329 380 467 620 murthy, babu, and jebaraj (2018): international journal of engineering materials and manufacture, 3 (4) 200-207 206 table 3: damping ratio from experiment plate boundary condition cccc cccf cfcf bare plate 0.012 0.016 0.025 plate with circular hole 0.015 0.020 0.032 plate with rectangular cutout 0.019 0.025 0.05 figure 9: comparison of damping factor of various composite laminates it can be seen from the figure 9 that there is an increase in damping when the configuration changes from cccc to cfcf for plates with different geometries. the plate constrained in all directions has less damping compared to that of plate, which is constrained in two directions. it can also be observed that the plate with cutout have higher damping compared to bare plate. when geometry of the cutout is considered, there is an increase in damping in rectangular cutout followed by circular cutout and bare plate. the damping could be increased with increased size of cut out. 4 conclusions the structural glass fibre reinforced plastic laminates have shown that freeness in the system reduced the natural frequency of the system for bare plate and plates with cutout in all the three modes. if it is intended to increase the natural frequency, one can make cutout in the laminate. it is also seen that the type of cutout whether circular or rectangular has a little impact on natural frequency. damping is highest in plate with rectangular cutout as compared to plate with circular hole and bare plate for all the types of configuration. it is evident that the damping is less in cccc configuration for all the three types of plates and increases with increase in freeness of the system as in cfcf configuration. damping contributes in attenuation of structural vibration mainly at natural frequencies. the freeness in the system reduces. scope for future work laminates can be fabricated using other types of reinforcements and hybrid composites could as well be produced and the same analysis can be carried out on those laminates. various resin systems can be used to fabricate the polymer composites such as polyester, polyether ether ketone etc. acknowledgment this research was funded by t.e.q.i.p-ii. the authors are grateful to those who contributed directly and indirectly in producing this paper. impact of constraint conditions and cutouts on natural frequency of glass fibre reinforced plastic composite 207 references 1. singiresu, s. r. (2011). mechanical vibrations, upper saddle river, pearson education, inc, fifth edition, 3-7. 2. diveyev, b., smolskyy, a. & sukhorolskyy, m. (2008). dynamic rigidity and loss factor prediction for composite layered panel. archives of materials science and engineering, 31(1), 2008, 45-48. 3. igor, s., & moshe, e. (2016). semi-analytical modeling of cutouts in rectangular plates with variable thickness– free vibration analysis. applied mathematical modelling, 1–18. 4. david, t. h. (2013). effects of constraint, circular cut out and in-plane loading on vibration of rectangular plates. international journal of mechanical sciences, 68, 114–124. 5. liu, x. & banerjee, j. r. (2016). free vibration analysis for plates with arbitrary boundary conditions using a novel spectral-dynamic stiffness method. computers and structures, 164, 108–126. 6. ivo, s., marko, t., nikola, v. & neven, h. (2015). an approximate analytical procedure for natural vibration analysis of free rectangular plate. thin-walled structures, 95, 101-114. 7. rui, l., bowang, gang, l. & bin t. (2016). hamiltonian system-based analytic modeling of the free rectangular thin plates’ free vibration, applied mathematical modelling, 40, 984-992. 8. xing, y. f. & xu, t. f. (2013). solution methods of exact solutions for free vibration of rectangular orthotropic thin plates with classical boundary conditions, composite structures, 104, 187-195. 9. ramu, i., & mohanty, s. c. (2012). study on free vibration analysis of rectangular plate structures using finite element method. procedia engineering, 38, 2758-2766. 10. eduard, v., theodor, k. (2001). thin plates and shells. new york basel, marcel dekker, inc. international journal of engineering materials and manufacture (2019) 4(2) 48-52 https://doi.org/10.26776/ijemm.04.02.2019.02 preventive maintenance of boiler: a case of kuwait industry ahmed s. kh. r. q. alazemi, mohammad yeakub ali and mohd. radzi che daud received: 01 february 2019 accepted: 20 april 2019 published: 20 june 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract in kuwait, industrial boilers are used extensively in food, chemical, oil and gas, textile, pharmaceutical, power plant sectors for generation steam. as a crucial item in industries, its maintenance is of utmost importance. as there are two main maintenance approaches such as reactive maintenance and preventive maintenance, the application of a typical maintenance is definitely based on types of application, safety concern, and cost benefit ratio. if a boiler is down for few days, it may cause huge loss as it interrupts subsequent steps especially in process industries. in this research, the importance of preventive maintenance strategy for steam boilers in kuwaiti industries has been studied. based on relative advantages and disadvantages, a proper strategy is proposed for better management and effective maintenance of boilers. keywords: steam boiler, reactive maintenance, preventive maintenance, maintenance strategy. 1 introduction a boiler is a steam generating unit. it is a closed metallic vessel contains partly water designed to use the chemical energy in fuel to raise the energy content of water so that it can be used for heating and power applications. many fossil and non-fossil fuels are fired in boilers, but the most common types of fuel include coal, oil, and natural gas. by heating water above the atmospheric pressure, steam could be generated at the desired pressure and temperature. in brief, the function of a boiler is to evaporate water into steam at constant pressure and to supply the required type of steam (elie tawil, 2013). industrial boilers are used extensively by food factory, chemical plant, oil field, textile factory, pharmaceutical factory, building material factory, dairy factory, edible fungus factory, garment factory, paper mill, brewery, commercial building, power plant (auxiliary), etc. commercial and institutional boilers are used in many other applications including commercial businesses, office buildings, apartments, hotels, restaurants, hospitals, schools, museums, government buildings, and airports. regardless the applications, steam boiler takes into account the safety needs of the actual work, has a variety of comprehensive safety protection functions to maintain 95% or more efficiency. boilers are commonly subdivided into watertube boiler and firetube boiler units. these designations reflect the way the water and combustion gases are designed to pass through the unit. boilers are also sometimes classified by their heat sources such as oil-fired, gas-fired, coal-fired, or solid fuel-fired boilers. reliable boiler operation requires a maintenance program that includes inspection, test, and preventive maintenance and repair procedures. for the program to succeed, it must be fully documented and have unequivocal management support. written procedures for all important activities listed below are to be maintained (jain, 2012). • operations, such as start-up, shutdown, maintenance procedures and abnormal operations, • emergency response such as operator response to boiler problems, facility response to boiler problems, and operator and boiler response to facility problems and external challenges, • visual inspection and non-destructive testing and evaluation • pressure equipment repair and hot work. a. s. kh. r. q. alazemi, m. y. ali and m. r. c. daud department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: mmyali@iium.edu.my reference: alazemi, a. s. kh. r. q., ali, m. y. and daud, m. r. c. (2019). preventive maintenance of boiler: a case of kuwait industry. international journal of engineering materials and manufacture, 4(2), 48-52. preventive maintenance of boiler: a case of kuwait industry • ensure both facility employees and contracted personnel are properly trained to comply with facility procedures. • conduct periodic refresher training and drills. • include all boilers and fired vessels in a central maintenance management system. on each piece of equipment, maintain a file which includes: 2 literature review in this section, literature review related to steam boilers is presented. it includes the boiler basics, efficiency, maintenance, and safety. however, the maintenance of steam boiler are reviewed in details, where as other subsections are briefly mentioned. this is because the main thrust of this research is preventive maintenance of industrial steam boilers. 2.1 boiler components a number of items must be fitted to steam boiler with the objective to improve operation, efficiency, and safety. however, they are broadly classified in to two, which are (i) boiler mountings and (ii) boiler accessories. a schematic picture of steam generating boiler is shown in figure 2.1. a general list of boiler mountings and boiler accessories are also presented. then a brief discussions on boiler mountings (sadath, 2018) and boiler accessories are presented in the following subsections. figure 1: general overview of steam boiler (watt, 2017) 2.1.1 boiler mountings mountings are crucial, without which the operation of boilers is unsafe. proper maintenance and care of the mountings is important for the safety of both the boiler and the personnel and to maintain optimum operating condition of the boiler (sadath, 2018). the boiler mountings are the part of the boiler and are required for proper functioning. in accordance with the indian boiler regulations, of the boiler mountings is essential fitting for safe working of a boiler. 1. safety valves 2. water level indicators 3. water level controller 4. water level alarms & cut-out assembly 5. remote water level transmitter 6. main steam outlet valve 7. pressure gauge with cock & pressure switches 8. feed water valves 9. burner assembly 10. air vent 11. water sampling valve 49 alazemi, ali and daud (2019): international journal of engineering materials and manufacture, 4(2), 48-58 12. manholes 13. mud holes & peepholes 14. bottom blow down valve 15. de-foaming (scum) valve 16. furnace drain valve 17. soot blowers 2.1.2 boiler accessories second categories include the components, which are installed to increase the efficiency of the steam power plants and help in the power working of the boiler unit. these fitting are called boiler accessories. these are also integral part of boiler. selected boiler accessories are listed below (boster, 2018). 1. air pre-heater 2. economiser 3. super heater 4. feed pump and 5. injector 2.2 boiler efficiency t h e e f f i c i e n c y of a boiler should be an important part since the annual cost of fuel can easily be 2 to 3 times the installed cost of the equipment. therefore, a difference in efficiency and the resultant difference in fuel cost can easily offset a difference in capital cost as fuel savings are on going – year after year. the subject of efficiency for a boiler is rather complex when all of the elements that affect efficiency are considered and a complete thermodynamic analysis is performed. the term efficiency is used in the context of a boiler includes boiler efficiency, thermal efficiency, combustion efficiency and fuel-to-steam efficiency (clayton, 2018). boiler efficiency has a great influence on heating related energy savings. it requires the maximization of heat transfer to th3e water and minimization of heat losses in the boiler (r. saidur, 2010) (nakkeeran, 2014). thermal efficiency refers to the efficiency of a thermal process and mechanical efficiency means the efficiency of a mechanical process. when used in conjunction with boilers, thermal efficiency sometimes refers to the efficiency of the heat exchanger that is fuel-to-steam efficiency. however, fuel-to-steam efficiency is the most significant but is difficult to calculate in real world situations. therefore, combustion efficiency that can be easily computed using a combustion gas analyser is frequently used for performance comparison purposes (sunit shah, 2011). combustion efficiency equals the total heat released in combustion, minus the heat lost in the stack gases, divided by the total heat released. for example, if 100 kw are released in combustion and 20 kw are lost in the stack, then the combustion efficiency is (100 – 20) / 100 = 0.80 or 80%. boiler efficiency can be improved by utilizing e economizer, which may give maximum cost benefit. there are two method for testing boiler efficiency (i) direct method and (ii) indirect method. in the direct method, the energy gain of the working fluid (water and steam) is compared with the energy content of the boiler fuel. whereas in the indirect method, the efficiency is the difference between the losses and the energy input. as such, a detailed maintenance plan should be prepared and implemented. it should include preventive and predictive or proactive maintenance activities. boiler, air-preheater and economizer tubes are critical parts. tube cleaning, leak test and wall thickness analysis should be carried out according to maintenance plan. wall thickness measurement and corrosion check must be carried out for components of flue gas path (nishadevi jadeja, 2017). 2.3 maintenance framework maintenance has been defined as the combination of technical and associated administrative actions intended to retain an item or system in, or restore it to, a state in which it can perform its required function (dhillon, 2002). a proper maintenance needs technical skills, techniques, historical data, methods to properly utilize the assets like factories, power plants, vehicles, equipment and machines. the key objective of maintenance is to ensure system function, life, and safety with minimum cost and expenses. poorly maintained machines or equipment may lead to random breakdowns causing unavailability for service (alsyouf, 2007). three closely related but different decision dimensions are thought to consider simultaneously. these dimensions are (i) output dimension, (ii) risk dimension and (iii) resources dimension. these will be optimising maintenance in an integrated fashion. the overall framework proposed is shown in figure 2 (price, 2007). the bathtub curve, shown in figure 3, provides a useful mental picture of the likelihood of failure over the life of an asset. similar to the life of a typical human, there is a greater likelihood of failure (death) at the beginning of life (infant mortality). 50 preventive maintenance of boiler: a case of kuwait industry figure 2: strategic maintenance framework (price, 2007) figure 3: bathtub curve (fluke, 2018) (daley, 2008) after the period of infant mortality, the likelihood of failure is relatively low and constant during a long period. as the asset ages, the likelihood of failure increases. while the bathtub curve provides a useful mental model of the likelihood of failure over the life of an asset, it is also somewhat misleading. while life generally takes the form shown on the diagram, it includes the simplifying assumption that we actually have a good idea of when the end of life will occur. that is typically not the case. more frequently, we have a general idea of when the end of life will occur but the manner in which an asset is used will affect when the end of life will occur (daley, 2008). in the following subsections, reactive and preventive (also called proactive) maintenance strategy are discussed. 2.3.1 reactive maintenance reactive maintenance is the practice of waiting for something to go wrong with the boiler, and then fixing it. while in some ways, this is the simplest strategy that requires no planning or monitoring. it is by no means the most effective maintenance. taking a reactive approach in boiler maintenance can be quite costly to the business in terms of boiler downtime, parts and labour costs for repairs, and reduced service life for the boiler. finally, if boiler maintenance relies on reactive approach, it is almost like inviting a problem and the consequences of a boiler problem can be quite severe (louis, 2018). the likelihood of failure under reactive maintenance is high and frequent over the time as shown in figure 4 (daley, 2008). figure 4: lifetime likelihood of failure under reactive maintenance (daley, 2008) age li ke lih o o d o f fa ilu re 51 alazemi, ali and daud (2019): international journal of engineering materials and manufacture, 4(2), 48-58 2.3.2 preventive maintenance efficient operation of boiler can be achieved if preventive maintenance strategy in place. it would be especially beneficial for those plants that rely on breakdown or run-to-failure maintenance. there are many advantages for having a preventive maintenance strategy, which apply to every kind and size of plant. the law of preventive maintenance strategy is that the higher the value of plant assets and equipment (per square foot of plant), the greater will be the return if there is a preventive maintenance strategy. preventive maintenance programme consists of actions that improve the condition of system elements for performance optimization and aversion of unintended system failure or collapse. it involves inspection, servicing, repairing or replacing physical components of machineries, plant and equipment by following the prescribed schedule. it is commonly agreed nowadays that preventive maintenance programme can be very successful in improving equipment reliability while minimizing maintenance costs (sunday olayinka oyedepo, 2011). this involves careful watching over the boiler equipment in order to anticipate and correct problems before they have a chance to cause a shutdown or severely affect the performance or service life of the equipment. the foundation of a strong preventive boiler maintenance plan is the historical data. here are some of the key sectors on which boiler operator collect data on a daily basis (gaps, 2018): • water level • operating pressure & temperature • feedwater pressure & temperature • oil pressure & temperature • condensate temperature • flue gas temperature • fuel consumption figure 5: lifetime likelihood of failure under preventive maintenance (daley, 2008) the likelihood of failure under preventive is less and steady over the time as shown in figure 5 (daley, 2008). by looking at the data over the course of a week or a month, it is possible to identify changes and trends that could indicate a need for service. this means the operator do not have to wait until the system actually has a serious problem to get service or deal with all the delays and inconveniences associated with such a problem. routine professional inspections and maintenance visit is another important part of a preventive boiler maintenance strategy. in addition to regular operators, a convenient and planned maintenance services are to be outsourced for few professional visits per year. the conventional professional techniques for non-destructive inspection of boiler materials and parts include liquid penetrant testing, magnetic particle testing, and ultrasonic testing. as such, a preventive maintenance strategy should include the followings (kiyoshi shimomura, 2010): • non-destructive testing. • periodic inspection. • pre-planned maintenance activities. • maintenance to correct deficiencies found through testing or inspections. operating logs for all boiler maintenance are to be strictly maintained. boiler logs may be as sophisticated as automated digital event recording or as simple as a tag attached to the gauge glass where test activity can be entered. in all cases, provide a written system, which is appropriate to the facility and properly maintained. the system should include, as applicable, records of all safety device tests and inspections, water chemistry activities and critical parameters. 2.3.2.1 preventive maintenance schedule preventive maintenance scheduling should be automated to the maximum extent possible. priority should be given to preventive maintenance and a very aggressive program to monitor the schedule and ensure that the work is completed according to schedule. for most boilers: the schedule of preventive maintenance is briefly presented in table 2.1 as an example (mobley, 2002). li ke lih o o d o f fa ilu re age 52 preventive maintenance of boiler: a case of kuwait industry experiences have shown that effective preventive maintenance scheduling can save considerable operational costs while increasing system reliability. in preventive maintenance scheduling, the outages of each unit have to be scheduled in an optimal way satisfying a number of constraints. over a planning interval, that overall system availability is to be maintained (hannam, 2007). table 1: schedule of preventive maintenance of steam boiler (mobley, 2002) frequency description daily • check water level • check oil level and make note of level (if gas, read gas meter) • determine daily consumption. • check oil level in compressor (oil burners), • check water temperature and oil pressure gauges for correct readings, • make note of water addition (if any), • take reading of stack thermometer, • check flame at high fire for length and colour. weekly • test low water safety cut off switch, • do a 15-second blow-down on the: column , • low water automatic water feeder, • surface valve ,oil preheater (for oil burners), • bottom emptying valve, • clean strainers and filters (oil burners). monthly • clean spinning cup or nozzle, • clean fire eye and smoke detection eye on chimney, • check prerotation veins for any oil residue, • check combustion chamber for any oil residue, • once every six months: • thoroughly clean burner and burner assembly, • clean tubes (once a year if oil or gas), • test the safety relief valve on the boiler. yearly • have a complete burner overhaul, • conduct an efficiency test on the burner, • clean stack and breaching, • once every two years: • have a waterside boil out done, • once every five years: (oil burners), • have the oil tank cleaned and inspected, • have the oil lines to and from the boiler steam-cleaned. 2.3.2.2 benefit of preventive maintenance the most important benefit of a preventive maintenance strategy is reduced costs as seen in many ways by aversion of system failure (jain, 2012): 1. reduced production downtime. 2. better conservation of assets and increased life expectancy of assets, thereby eliminating premature replacement of boiler machinery and equipment. 3. reduced overtime costs and economical use of maintenance workers due to working on a scheduled basis instead of a crash basis to repair unanticipated breakdowns. 4. reduced cost of repairs by reducing secondary failures. when parts fail in service, they usually damage other parts. 5. identification of boiler equipment with excessive maintenance costs, indicating the need for corrective maintenance, operator training, or replacement of obsolete equipment. 6. improved safety and quality conditions. 53 alazemi, ali and daud (2019): international journal of engineering materials and manufacture, 4(2), 48-58 2.3.2.3 preventive maintenance of boilers in kuwaiti industry although there are many steam generating boilers in kuwaiti industrial sectors, there are not many article to report that report the maintenance strategy for boilers. it is assumed that the application of preventive maintenance is not precisely practiced. failure of steel tubes in a super heater boiler used at one of kuwait electrical and power plant has been investigated by kuwait institute for scientific research and reported. the failure was due to high heat input, which reached up to 7000 c for long time. at this high heat level, the steel microstructures transformed and caused failure (a. husaina, 2005). the importance of preventive maintenance was highlighted while investigating the failure of superheated firetube of boiler in kuwaiti industries. it is recommended that boiler firing should be checked periodically and adjusted to the operation to fit the initial design (m. alradhi, 2011). ineffective maintenance and management methods and the lack of timely, factual knowledge of asset condition caused high maintenance cost represent a substantial opportunity for every manufacturing and production facility worldwide. effective application of preventive/predictive maintenance can reduce 30-50% (fluke, 2018). 3 problem statement steam boilers are unavoidable items in modern industrial civilization. boilers are extensively used in food factory, chemical plant, oil field, textile factory, pharmaceutical factory, building material factory, dairy factory, garment factory, paper mill, commercial building, power plant, office buildings, apartments, hotels, restaurants, hospitals, schools, museums, airports, etc. regardless the applications, a comprehensive maintenance and safety protection are to be ensured for safe and efficient functioning of any steam boilers. although there are several maintenance approach for efficient boiler maintenance and effective functioning, they have their own merits and demerits, which are associated to cost, and benefits. among the approaches, preventive maintenance of steam boilers is thought to be the best for efficient and smooth functioning. however, historically it was observed that the steam boilers in kuwait industrial sectors suffers from sudden malfunctions and causes process interruption and hence financial loss. as such, a critical investigation of application of preventive maintenance of steam boilers in kuwait industrial sectors is essential. in this research, the application of preventive maintenance of steam boilers is to be surveyed and analysed to identify any weakness and to propose appropriate preventive maintenance of steam boilers in kuwaiti industries. the cost effectiveness for preventive maintenance is also will be analysed. based on the present literature review, the research gap has been analysed and presented in table 3.1. 4 research philosophy kuwaiti industrial sectors rely on labour from kuwaiti citizen as well as foreign experts and workers. many of the services are subcontracted to local and overseas companies for years. as such, the people at the workplace are from various nationalities, language and cultures. however, most of the companies have no induction programme for harmonization, language and technical training to develop the eco system at workplace. as a result, there are differences in understanding of technical responsibilities and practices. therefore, it is assumed that either there is no well-designed strategy for preventive maintenance of steam boilers in kuwaiti industries or the existing strategies could not be strictly followed for safe and efficient running of steam boilers. 5 research scope the main scope of this project is to study the practice of preventive maintenance of steam boilers in kuwaiti industries to identify weaknesses and then propose effective approaches for better maintenance of steam boilers. it includes the followings: 1. studying and investigating the existing preventive maintenance practices for steam boilers in kuwaiti industries. 2. analysis of surveyed data to identify the insufficiency of maintenance approaches for steam boilers in kuwaiti industries. 3. propose efficient approaches for preventive maintenance of steam boilers to ensure smooth and efficient running of boilers in kuwaiti industries. 6 research objectives the objective of this research is to formulate efficient approaches for effective preventive maintenance of boilers in kuwaiti industries. the specific objectives of this research are as follows. 1. to study the present preventive maintenance approach and real practice for boilers in kuwaiti industries. 2. to study the enforcement from the government to comply for maintenance of boilers for efficient and safe running. 3. to analyse the surveyed data to formulate efficient and applicable approaches for preventive maintenance of steam boilers. 4. to validate the proposed strategy for preventive maintenance of steam boiler in one of the selected industries. 54 preventive maintenance of boiler: a case of kuwait industry table 0.1: research gap analysis based on literature review authors article title study method maintenance method findings/recommendation jain, a. k., 2012 an optimal preventive maintenance strategy for efficient operation of boilers in industry review preventive maintenance proposal only no specific case study no management culture studies allen, s.b. t. and john w.h. p., 2007 methodology and theory a maintenance optimisation framework in application to optimise power station boiler pressure parts maintenance experimental case study general optimisation of maintenance decision case study: power station in victoria, australia sunday, o. o. and richard, o. f., 2011 a study of implementation of preventive maintenance programme in nigeria power industry-egbin thermal power plant, case study experimental case study preventive maintenance implementation and performance study historical data: 2005-2009 (5 years) case study: egbin power plant, nigeria recommendation: to move from reactive to proactive maintenance and management. mohsen a., roger g. h. and ashraf w. l., 2007 preventive maintenance scheduling for multicogeneration plants with production constraints experimental case study programming preventive maintenance scheduling of preventive maintenance integer programming case study: cogeneration for power generation and fresh water production in kuwait husaina, a. and habib, k., 2005 investigation of tubing failure of super-heater boiler from kuwait desalination electrical power plant experimental case study preventive/ proactive maintenance failure analysis of boiler components case study: electrical & power plant, kuwait premature failure, recommends proactive maintenance ahmed alazemi, 2019 preventive maintenance strategy for efficient operation of boilers in industry experimental survey preventive maintenance kuwaiti industry (oil & gas, power plant) analysis of present maintenance and identification of root cause. objective: find appropriate scheduling for preventive maintenance and its implementation 4 research philosophy kuwaiti industrial sectors rely on labour from kuwaiti citizen as well as foreign experts and workers. many of the services are subcontracted to local and overseas companies for years. as such, the people at the workplace are from various nationalities, language and cultures. however, most of the companies have no induction programme for harmonization, language and technical training to develop the eco system at workplace. as a result, there are differences in understanding of technical responsibilities and practices. therefore, it is assumed that either there is no well-designed strategy for preventive maintenance of steam boilers in kuwaiti industries or the existing strategies could not be strictly followed for safe and efficient running of steam boilers. 55 alazemi, ali and daud (2019): international journal of engineering materials and manufacture, 4(2), 48-58 5 research scope the main scope of this project is to study the practice of preventive maintenance of steam boilers in kuwaiti industries to identify weaknesses and then propose effective approaches for better maintenance of steam boilers. it includes the followings: 1. studying and investigating the existing preventive maintenance practices for steam boilers in kuwaiti industries. 2. analysis of surveyed data to identify the insufficiency of maintenance approaches for steam boilers in kuwaiti industries. 3. propose efficient approaches for preventive maintenance of steam boilers to ensure smooth and efficient running of boilers in kuwaiti industries. 6 research objectives the objective of this research is to formulate efficient approaches for effective preventive maintenance of boilers in kuwaiti industries. the specific objectives of this research are as follows. 1. to study the present preventive maintenance approach and real practice for boilers in kuwaiti industries. 2. to study the enforcement from the government to comply for maintenance of boilers for efficient and safe running. 3. to analyse the surveyed data to formulate efficient and applicable approaches for preventive maintenance of steam boilers. 4. to validate the proposed strategy for preventive maintenance of steam boiler in one of the selected industries. 7 research methodology the research initiative starts with literature review of relevant technical and government enforcement papers in the field. based on state of the arts literature review, problem statement, research objective, and scope are established. research methodology is developed to carry out the research. data will be collected from one of the power plant in kuwait and will be analysed to identify why present method of maintenance is found to be ineffective. then questionnaire is designed for data collection. based on data analysis, research findings will be established. at the end, a report will be prepared with empirical relationship and recommendation. the process is depicted in figure 6. 8 present study and preliminary result research design and questionnaire have been prepared to collect historical data related to boiler maintenance in kuwaiti oil and gas sector for further analysis and to find the correlation due to unplanned shutdown of the plant. the preliminary studies showed that the boiler maintenance and management in kuwait still esteems tough, individualistic, dominating leadership that often fails to perceive threats or opportunities. management that is more effective would be pivotal to organizing personnel to recognize pertinent opportunities and achieve worthwhile results rather than generate impasses, stagnation, bureaucracy and interpersonal conflict. the following maintenance problems are frequently encountered in boiler maintenance in kuwaiti oil, gas and power sectors: 1. maintenance is not treated seriously at board level, or even by lower level management. 2. maintenance processes lack a corporate or business culture (e.g. no business plans, ineffective or superficial budgets and unfocused reports). 3. maintenance technicians and even team leaders lack adequate management and visionary skills. 4. preoccupation with introducing advanced maintenance methods, while relevant basic maintenance practices are not being implemented. 5. the kuwaiti industries are still using traditional maintenance planning to compile maintenance schedules for all equipment and plant. these schedules only rarely reach the shop floor. hence, maintenance schedule ends up without proper and full implementation. 9 expected outcomes the expected outcomes of the project titled “preventive maintenance strategy for efficient operation of boilers in industry” are as follows. 1. enforcement of current procedure for preventive maintenance of industrial boiler in kuwait. 2. to propose an efficient plan/schedule of preventive maintenance of boiler to avoid unpredicted maintenance and shut down of boilers. 3. pilot implementation of the schedule preventive boiler maintenance for effective running of boilers in industry. 56 preventive maintenance of boiler: a case of kuwait industry figure 6: research methodology 10 summary this article is based on preliminary study of maintenance of steam boilers in kuwait industries. the studies are literature review, practical visit and discussion with maintenance personnel. this study showed that: • the present maintenance systems need to be studied and revised for better services. • the downtime of boiler should be significantly reduced for efficient and uninterrupted industrial processes. • based on the study, selected plant can be considered for pilot study to verify the improvement. • an appropriate research methodology is proposed for conducting this research. references a. husaina, k. h. (2005). investigation of tubing failure of super-heater boiler from kuwait desalination electrical power plant. desalination, 203-208. alsyouf, i. (2007). the role of maintenance in improving companies’ productivity and profitability. international journal of production economics, 70-78. 57 alazemi, ali and daud (2019): international journal of engineering materials and manufacture, 4(2), 48-58 boster. (2018). boiler mountings and accessories. http://www.mechanicalbooster.com/2016/05/boiler-mountingsand-accessories.html. clayton. (2018). steam basics-boiler efficiency. uk: clayton innovative steam system solution. daley, d. t. (2008). the little black book of maintenance excellence. industrial press inc. dhillon, b. s. (2002). engineering maintenance: a modern approach. crc press. elie tawil, p. e. (2013). boiler classification and application. continuing education and development. ny, 10980.: continuing education and development, inc. fluke. (2018). the basics of predictive /preventive maintenance. https://dam-assets.fluke.com/s3fspublic/2534401_b_eng_w.pdf. gaps. (2018). boiler maintenance and operation. global asset protection services llc. hannam, m. a. (2007). preventive maintenance scheduling for multi-cogeneration plants with production constraints. journal of quality in maintenance engineering, 276-292. jain, a. k. (2012). an optimal preventive maintenance strategy for efficient operation of boilers in industry. control theory and informatics, 1-4. kiyoshi shimomura, h. i. (2010). advanced technologies of preventive maintenance for thermal powerplant. tokyo. louis, s. (2018). is your boiler maintenance strategy proactive or reactive? http://www.stanleylouis.com/is-yourboiler-maintenance-strategy-proactive-or-reactive/. m. alradhi, a. a. (2011). role of oxide scale thickness measurements in boiler conditions assessment. international journal of mechanical, aerospace, industrial, mechatronic and manufacturing engineering, 1737-1739. mobley, r. k. (2002). an introduction to preventive maintenance. amsterdam: butter worth heinnman. nakkeeran, m. k. (2014). performance analysis from the efficiency estimation of coal fired boile. international journal of advanced research, 561-574. nishadevi jadeja, s. z. (2017). improved performance of a industrial packaged boiler by use of economizer. improved performance of a industrial packaged boiler by use of economizer, 996-1004. price, a. s. (2007). a maintenance optimisation framework in application to optimise power station boiler pressure parts maintenance. journal of quality in maintenance engineering, 364-384. r. saidur, j. u. (2010). energy, exergyandeconomicanalysisofindustrialboilers. energy policy, 2188-2197. sadath, o. (2018). boiler mountings . dhaka: https://marinestudy.net/wp-content/uploads/2015/04/boilermountings.pdf. sunday olayinka oyedepo, r. o. (2011). a study of implementation of preventive maintenance programme in nigeria power industryegbin thermal power plant, case study. energy and power engineering, 207-220. sunit shah, d. m. (2011). boiler efficiency analysis using direct method. international conference on current trends in thechnology. ieee. watt, m. (2017). general overview and components of a boiler. microwatt energy, http://en.microwatt.cn/index.php?c=content&a=show&id=415. 58 abstract international journal of engineering materials and manufacture (2023) 8(3) 67-74 https://doi.org/10.26776/ijemm.08.03.2023.02 u. abdullahi mechanical engineering department, faculty of engineering bayero university, kano, pmb 3011 kano state nigeria e-mail: ummaabdullahi@abu.edu.ng reference: abdullahi (2023). effects of alloying element and heat treatment on mechanical properties of alloy steels. international journal of engineering materials and manufacture, 8(3), 67-74. effects of alloying element and heat treatment on mechanical properties of alloy steels umma abdullahi received: 29 march 2023 accepted: 08 june 2023 published: 01 july 2023 publisher: deer hill publications © 2023 the author(s) creative commons: cc by 4.0 abstract the effects of cr and ni on three different types of steel with different carbon ratios under constant conditions such as the welding current 120a, voltage 80v, diameter 10 mm and angle 60 degree was observed. nickel percentage of up to 0.147% and chromium 0.083% contributed to affecting the mechanical properties of the steel. undissolved carbide particles refine the austenite grain size. in the presence of nickel, chromium carbide is less effective in austenite grain refinement than chromium carbide in absence of nickel at temperature below 975°c. nickel does not produce any austenite grain refinement but presence of nickel promotes the formation of acicular ferrites. it was also found that ni and cr as chromium carbide also refines the ferrite grain size and morphology. cr as chromium carbide is more effective in refining ferrite grain size than nickel. the microstructure of the base metal as a reference material was analysed before heating to support the results of chemical analysis. nickel percentage of up to 0.147% and chromium 0.083%. molybdenum was 0.03% which contributed to affecting the mechanical properties of the steel. keyword: alloy steel, heat treatment, chromium, nickel, grain size 1 introduction with the technological development in advanced industries such as oil, automotive, aviation, piping networks, metallic bridges and other important industries, the need for a steel with higher tensile strength, adequate ductility and toughness has increased (razzak m.a, 2011: abdullahi u, 2022: bello et al., 2021). this has been principally the issue at hand where light weight is needed, as in the automobile and aircraft industries. an increase in carbon content met this demand in a limited way, but even in the heat-treated condition the maximum strength is about 600-700 mpa above which value, a rapid decrease in ductility and impact strength arises and large effects limit the permissible section (ragu et al., 2015). heat treated alloy steels provide high strength, high yield point, combined with significant ductility even in large sections. the use of plain carbon steels frequently necessitates water quenching accompanied by the danger of distortion and cracking, and only thin section can be hardened throughout. for resisting corrosion and oxidation at elevated temperatures, alloy steels are essential. the researchers in this area assumed the following definition: ‘carbon steels are regarded as steels containing not more than 0⋅5% manganese and 0⋅5% silicon, all other steels being regarded as alloy steels’ (material handbook, 1964) . the major alloying elements added to steel in generally varying amounts either separately or in compound mixtures are nickel, chromium, manganese, molybdenum, vanadium, niobium, silicon and cobalt. the observation in this paper is directed towards experiment on low alloy steels (0⋅095-0-99 wt% c) which has a high weldability and toughness. these properties are in high priority for structural steel if these can be blended in with a high tensile strength. the sole purpose of this study is to find out proper alloying elements to increase the tensile properties with appropriate heat treatment. in the current study three different steels including plain carbon (pc) steel with varying weight percentages of ni and cr were used to observe the effects of alloying elements. the effects were characterized according to the presence of alloying elements either alone or in combination with each other in the low carbon steel samples. the steel samples were characterized using mechanical testing method. tensile strength and elongation data were collected to compare the effects of heat treatment and alloying elements. metallographic analysis was also done to confirm a correlation between alloying elements and microstructural feature like grain size and morphology. 2 experimental work 2.1 specimen preparation three different steels containing the range of 0⋅095%-0.99% carbon and plain carbon steel were used in this study. the composition of the steels was presented in table 1, 2 & 3 for low, medium and high carbon steel respectively. effects of alloying element and heat treatment on mechanical properties of alloy steels 68 the steels were heat treated in an air induction furnace. about 15 mm diameter specimens of each steel were rolled down in order to study the austenite grain coarsening behaviour. 2.2 carburization and measurement of austenite grain size considering the size of the austenite grains as it directly affects the succeeding structure and hence the properties of steels, a study was made to determine prior austenite grain size at temperatures higher than upper critical temperature. carburization technique was deployed to deduce prior austenite grain size. there are also other methods in determining prior austenite grain size like isothermal transformation technique, oxidation technique, etc. but previous work showed that the isothermal technique did not work well in revealing prior austenite grain boundary of low alloy steels (razzak, 2011: ragu et al., 2015: clark & varney, 1962). therefore, carburization technique was implemented to reveal prior austenite grain boundaries of steels in this work. the technique is based on the formation of a continuous cementite network at the austenite grain boundaries. carbon will diffuse in steel from the carburizing atmosphere forming hypereutectoid steel at the surface of the specimen and during slow cooling in the furnace continuous cementite network is formed at the austenite grain boundaries at the selected austenitizing temperatures. subsequent etching of the furnace cooled samples revealed the cementite network formed which marked the prior austenite grain size at the selected carburizing temperatures (clark & varney, 1962: erding et al., 2019). solid carburizing or pack carburizing technique was used for this research. the steel specimens were heated to different austenitizing temperatures, i.e., 900–1050°c with an interval of 50°c. before heating these specimens, they were packed in a pot with carburizing mixture. then they were placed in a dedicated furnace. subsequently, when reaching the required temperature, they were held at that temperature for 2 h to reach near the equilibrium condition and then cooled in this furnace to room temperature. slow cooling ensured a continuous cementite network through the austenite grain boundaries. the assessment of prior austenite grain size was made from direct measurement of the austenite grains in the specimens under optical microscope. the grain size was measured using the mean linear intercept method, counting grain boundary intersections with the circumference of the circle in the eyepiece of a microscope. the effective circumference of the circle was determined precisely by measuring its diameters with reference to a stage μm at the magnification used. a total of at least 300–600 intersections were counted for each specimen. then the size of austenite grain was measured using the mean linear method. 2.3 mechanical testing the heat treated 13 mm diameter bar was then machined into standard tensile specimens with a nominal diameter and gauge length of 3⋅99 and 25 mm respectively. the grip size was chosen to be 13 mm in width and in length as shown in figure 1. the tensile specimens were then tested with a universal tensile testing machine (instron) to obtain data on yield strength (ys), ultimate tensile strength (uts), percentage of elongation (% el), and percentage of reduction in area (% ra). figure 1: dimensions of tensile specimen and location on sample for subsequent microstructure study 2.4 optical microscopy samples from fractured tensile specimens were taken for microscopic examination. to avoid heavily deformed zone for microstructure observation, samples were chosen from the grip of the tensile test specimen as shown in figure 1. the samples were then ground, polished up to γ-aluminium powder and then etched in 5% nital solution. the microstructure of these specimens was then studied. optical microscope photograph (figure 4) of the microstructure of each specimen was taken to compare the microstructural features in conjunction with the mechanical properties. abdullahi, u. (2023): international journal of engineering materials and manufacture, 8(3), 67-74 69 3 experimental results 3.1 alloying elements three different types of alloy steel were used in this work as low, medium and high carbon steel. the classification was based on the carbon content, but according to the level of main mechanical properties of practical importance. as low carbon steels having carbon up to 0.25%, medium carbon steels having carbon between 0.25% to 0.55% and high carbon steels has carbon from 0.55% to ideally a maximum of 2.11% but commonly up to 1.5% max. in commercial steels. and this is the most commonly used commercial classification. table 1, 2 and 3 present the result of chemical composition of the three selected carbon steel. table 1: chemical composition of low carbon alloy steel c % 0.095 si % 0.235 mn % 0.90 p % 0.011 s % 0.013 cr % 0.0083 ni % 0.147 mo % 0.030 al % 0.039 cu % 0.208 co % 0.019 ti % ≤ 0.0010 nb % ≤ 0.0040 v % ≤0.0010 w % ≤0.010 pb % ≤0.0030 mg % ≤0.0010 b % 0.0008 sn % 0.012 zn % ≤0.0020 as % 0.020 bi % ≤0.0020 ca % 0.00003 ce % ≤0.0030 zr % ≤0.0015 la % ≤0.0010 fe % 98.2 table 2: chemical composition of medium carbon alloy steel c % 0.272 si % 0.108 mn % 0.449 p % 0.00089 s % 0.014 cr % 0.0027 ni % 0.029 mo % ≤ 0.0020 al % 0.042 cu % 0.016 co % 0.013 ti % ≤ 0.0010 nb % ≤ 0.0040 v % ≤0.0010 w % ≤0.010 pb % ≤0.0030 mg % ≤0.0010 b % ≤0.0005 sn % ≤0.010 zn % ≤0.0020 as % ≤0.0010 bi % 0.0046 ca % 0.011 ce % 0.0051 zr % ≤0.0015 la % 0.0017 fe % 99.0 table 3: chemical composition of high carbon alloy steel c % 0.99 si % 0.407 mn % 0.79 p % 0.046 s % 0.227 cr % 0.127 ni % 0.132 mo % 0.049 al % 0.127 cu % 0.065 co % 0.050 ti % 0.014 nb % 0.023 v % 0.0023 w % 0.414 pb % 0.132 mg % 0.175 b % 0.028 sn % 0.022 zn % ≥ 0.036 as % 0.036 bi % 0.0048 ca % ≥ 0.015 ce % 0.180 zr % ≤ 0.0015 la % -0.261 fe % ≤ 94.6 3.2 austenite grain size the heat-treatment temperatures of steels were determined by a careful examination of the austenite grain size. the criteria for the determination of the heat treatment temperature of steels were that the steel had the same austenite grain size and that the temperatures were such that an appreciable proportion of the solute elements had entered into solution for subsequent precipitation. this is indicated in figure 2 by a steep rise of the austenite grain size. an austenite grain size of 38 μm was found to be suitable and the corresponding heat-treatment temperatures for the steels were 910, 900, 970 and 950°c for the steels 1–3, respectively. the dissolution temperatures obtained by the equilibrium thermodynamic calculation is below the one expected from the experimental one. as heat treatments were done for 2 h at higher temperatures, it is logical to expect that the precipitating elements will be completely in solution at the chosen heat treatment temperature. effects of alloying element and heat treatment on mechanical properties of alloy steels 70 the prior austenite grain size against temperature graph is plotted and shown in figure 2. the figure shows that, the austenite grain size increases with increasing austenitizing temperature. for steels 1 and 2 this relation is almost linear. steel 1 is a low carbon steel and it does not contain higher number of alloying elements especially carbon. hence, there is no obstruction for grain growth and the austenite grain size increases rapidly and linearly with temperature. steel 2 is basically medium carbon steel with nickel in a little higher percentage than in steel 1. this steel also showed similar austenite grain coarsening behaviour as that of low carbon steel 1. nickel remained in solid solution and not combined with carbon to produce any second phase particles. in absence of second phase particles in steel 2, grain growth is not hindered. steel 3 produced the finer austenite grain size than steel 1. cr combines with carbon and forms chromium carbide precipitates (ragu et al., 2015: clark & varney, 1962: erding et al., 2019: armentani, 2007: kang et al., 2007). figure 2: variation of prior austenite grain size with temperatures for steels 1-3 these precipitates pin the austenite grain boundaries and inhibit grain growth resulting in finer austenite grain size than steel 1. steel 3 also produced grain size finer than steel 1 and coarser than steel 2 (ragu et al., 2015: clark & varney, 1962: kang et al., 2007: jeshvaghani & mirzaei, 2013). steel 3 contains both cr and ni in a little higher percentage than the two steels. as it was observed from steel 1 nickel does not have much significant effect on the austenite grain refinement. therefore, the finer austenite grain size in steel 3 compared to steel 1 is clearly due to the effect of chromium carbide precipitates. the austenite grain size of steel 2 remains finer up to 950°c beyond this temperature; there is a steep rise in austenite grain growth. steel 2 produced finer grain size than steel 3 with (ni + cr) up to a temperature of 975°c and above this temperature steel 3 produced finer austenite grain size than steel 2. composition of steel suggested that steel 2 (cr = 0.0027 wt.%) should contain slightly higher volume fraction of precipitates than steel 3 (cr = 0⋅127 wt.%). presence of higher volume fraction of precipitates increased the grain boundary pinning (zener pinning) efficiency and thus results in smaller grain size as observed from figure 5 showing the prior austenite grain boundaries of steels 1–4 revealed by carburization technique at 1000°c (× 200). the results also indicate that, presence of nickel, chromium carbide is less effective in austenite grain refinement than chromium carbide in absence of nickel at temperature up to 975°c. moreover, presence of nickel decreases the chromium carbide dissolution temperature in the low alloy steels. among the three alloys, steel 2 showed the same grain coarsening behaviour as steel 1. this confirms the previous understanding that ni has no effect on the austenite grain size refinement. finer austenite grain size of steels 2 and 3 indicated that cr as chromium carbide is an effective grain refining element for hsla. 3.3 mechanical properties presence of acicular ferrite effects the mechanical property by lowering elongation and increasing yield strength (clark & varney, 1962: frost, 1991: panel et al., 2022: boumerzoug et al., 2011). in the case of steel 4 with higher amount of ni and cr as alloying elements did not show any significant changes in ferrite morphology, thus the elongation obtained is equal to the base steel 1. it can be expected that the presence of second phase particles and smaller grain size in steels 3 and 4 should yield less elongation which is contradictory with the experimental results obtained. the explanation can be given from the point of view of the fraction of pearlite present in the microstructure and its distribution. presence of second phase particle decreased the amount of carbon available in the matrix. smaller weight fraction of carbon available during cooling should yield lower fraction of pearlite in the microstructure in comparison with the base plain carbon steels 1 and 2 (ni). lower volume fraction of pearlite in the microstructure in conjunction with finer distribution increased the deformability in steels 3 and 4. the effects of second phase particles and smaller ferrite grains in decreasing ductility is somewhat countered by the effects of change in distribution and lower fraction of pearlite in the microstructure in increasing ductility. 20 30 40 50 60 70 1 2 3 a u s t e n i t e g r a i n s i z e ( u m ) temperature (degree c) 910 950 1000 1050 abdullahi, u. (2023): international journal of engineering materials and manufacture, 8(3), 67-74 71 figure 3 shows the tensile test results from the specimens of steels 1–4 cooled at 120°c/min. it is evident from the figure that yield strength of steels 2–4 is higher than the base steel 1 (pc). among the three alloy steels, steel 4 with ni and cr produced the highest yield strength and steel 2 with ni produced the lowest yield strength. steel 3 with chromium produced yield strength in between steels 2 and 4. a similar trend was found with the ultimate tensile strength of these steels. the higher yield strength of steel 3 with cr than steel 2 with ni indicated that cr is more effective than nickel in increasing yield strength. the highest yield strength of steel 4 with ni and cr is clearly due to the combined effects of ni and cr. nickel does not produce any second phase particle. figure 3: comparison of yield strength and elongation of steels 1–4 cooled at 120°c/min ni is found mostly in the form of solid solution in the ferrite (clark & varney, 1962: kang et al., 2007: jesvaghani & mirzaei, 2013: hastuhiko et al., 2007). however, ni increased the strength of the steel by solid solution strengthening. besides that, ni also lowers the transformation temperature, even though the lower transformation temperature produces smaller ferrite grains (clark & varney, 1962: kang et al., 2007: jesvaghani & mirzaei, 2013). besides that, it was observed from the microstructural observation, presence of ni promotes acicular ferrite formation. change in morphology of the ferrite to acicular ones also produces obstacle in dislocation glide. thus, nickel increases the strength by refining the grains by lowering the transformation temperature and also changing the morphology of the ferrite grains. chromium in the form of chromium carbide precipitates increased the strength by means of precipitation strengthening. secondary chromium carbides pin the grain boundaries and inhibit the grain growth. this results in grain refinement and presence of second phase particles also makes dislocation movement more difficult. second phase particles like chromium carbide in the matrix increases the energy required for elastic/plastic deformation, hence creates higher strength in the alloy. percentage of elongation in steels 1, 3 and 4 showed similar results while steel 2 with ni in solid solution showed reduced elongation. 3.4 morphology of steel it was observed that steels 1–4 showed regular ferrite–pearlite structure with some ferrite morphology change in steel 2. the microstructure observed comprised of fine ferrite–pearlite structure where the pearlite is isolated in the ferritic matrix. steel 2 at the fast-cooling rate of 120°c/min showed some widmanstatten ferrite along with regular ferrite pearlite. steels 2–4 produced finer ferrite pearlite than steel 1. among the three alloys, steel 3 produced finer grain size than steel 2 and steel 4 produced the finest grain structure of all steels as noticed also in figure 5. microstructural observation showed presence of acicular ferrite in steel 2. the microstructures of steels 1–4 cooled at 120°c/ min are shown in figure 6. steel 2 has ni as alloying elements; hence it showed smaller grains in comparison with the plain carbon steel 1. it is well known that ni lowers the austenite to ferrite transformation temperature and thus produced condition for smaller ferritic grains to nucleate at relatively low grain mobility condition. besides that, from the microstructural observation shown in figure 6 it was also clear that ni modified the ferrite morphology to more acicular shape. steel 3 contains a little higher amount of cr than steel 2. and cr combines with c and formed chromium carbide precipitates during cooling from the austenite zone. these chromium carbide precipitates pin the newly nucleated ferrite grain boundaries and thus fine ferrite grain is obtained. the finer grain size of steel 3 than steel 2 clearly indicate that cr as chromium carbide is more effective in ferrite grain size refinement than nickel. steel 4 contains both ni and cr. the finest ferrite grain size of this steel is effects of alloying element and heat treatment on mechanical properties of alloy steels 72 due to the combined effects of nickel and chromium. however, it can be said that cr in presence of ni is more effective in producing finer microstructure. in figure 6, average grain diameter of steels 1–4 is presented. grain size measurement also suggested the same phenomenon predicted by microstructural observations. considering the experimental error, it can be said that steel 4 has the smallest mean grain diameter of ~ 15 μm. steel 2 showed smaller grain diameter than steel 1 but it should be considered that acicular morphology of ferrite in the microstructure of steel 2 produced greater extent of error in the measurement by mean linear intercept method. so, ferrite grain size measurement for steel 2 is not fully reliable. (a) steel 1 (b) steel 2 (c) steel 3 (d) steel 4 figure 4: optical micrograph showing prior austenite grain boundaries of steels 1–4 revealed by carburization technique at 1000°c (× 200). figure 5: average grain diameter of steels 1–4. 0 5 10 15 20 25 30 35 40 45 steel 1 steel 2 steel 3 steel 4 g r a i n s i z e ( μ m ) plain low, medium & high carbon steel abdullahi, u. (2023): international journal of engineering materials and manufacture, 8(3), 67-74 73 4 conclusions the carburization method is a practically suitable technique in deducing the prior austenite grain boundaries in low carbon steels comprising nickel and chromium as alloying elements. on heating undissolved particles of chromium carbide refined the austenite grain size. in the presence of nickel, chromium carbide is less effective in austenite grain refinement than chromium carbide in absence of nickel at temperature below 975°c and the reverse is true above 975°c. nickel did not produce any austenite grain refinement. nickel and chromium as chromium carbide precipitates were found to refine the ferrite grain size. cr is found to be more effective in the refinement of ferrite grain size than nickel. nickel in solution and chromium as chromium carbide precipitates increased the yield strength of the low carbon steels but the effectivity of chromium carbide precipitates in the increment of yield strength was found to be more than that of nickel. in the presence of nickel, the contribution of chromium carbide. (a) steel 1 (b) steel 2 (c) steel 3 (d) steel 4 figure 6: optical micrograph of steels 1–4 cooled at 120°c/min (× 200). acknowledgement the author acknowledged the support from tetfund ibr 2021 intervention through ahmadu bello university, zaria and also appreciated the university for providing all the equipment used to conduct the research. effects of alloying element and heat treatment on mechanical properties of alloy steels 74 references 1. abdullahi, u. (2022). effect of tempering treatment on the post-weld properties and chemical compositions of arcwelded alloy steels. international journal of engineering materials and manufacture, 7(4), 89-94 2. american society for metals 1964 metal handbook (materials park, ohio: american society for metals) 8th edn, vol. 2 3. armentani, e. r, (2007). the effect of thermal properties and weld efficiency on residual stresses in welding. journal of achievements in materials and manufacturing engineering, 20, no. 1-2, 319-322. 4. bello k. a., abdullahi u., adeniyi a.s, adebesi a. a, dodo r. m., abdulwahab m., adekunle a.s, (2021). optimizing tensile properties of age hardened a356 aluminium alloy via taguchi method. nigerian journal of engineering, 28(1), 61-68 5. boumerzoug, z., raouache, e., delaunois, f. (2011). thermal cycle simulation of welding process in low carbon steel. materials science and engineering: a, 530, 191-195. 6. clark d s and varney w r 1962 physical metallurgy for engineers (new york: litton educational publishing inc.) 2nd edn 7. erding w., renbo s.* and wenming x., (2019). effect of tempering temperature on microstructures and wear behavior of a 500 hb grade wear-resistant steel. metals 2019, 9, 45 8. frost n.e., dugdale d.e, (1991). the propagation of fatigue cracks in sheet specimens. journal of sound & vibration, 69, no. 4. 9. hamid m. m., effect of heat treatments on the mechanical properties of welded joints of alloy steel by arc welding. diyala diyala journal of engineering sciences vol. 12, no. 02, june 2019, pages 44-53 10. hastuhiko. o, tatsuya. s, tadashi, (2007). weld ability of high strength steel, (hss) sheets for automobiles, nippon steel technical, no.95. 11. jeshvaghani, r.a and mirzaei,r ,m ,(2013). study of welding velocity and pulse frequency on microstructure and mechanical properties of pulsed gas metal arc welded high strength low alloy steel. materials & design, 51, 709-713. 12. kang j s, huang y, lee c w and park c g 2007 adv. mater. res. 15–17 786 13. panel x. w., changbo l., yuman q., yanguo l., zhinan y., xiaoyan l., mingming w. and fucheng z., (2022). effect of tempering temperature on microstructure and mechanical properties of nanostructured bainitic steel. material science and engineering: a, 832. 14. ragu n. s., balasubramanian v., malarvizhi s., rao a.g., (2015). effect of welding processes on mechanical and microstructural characteristics of high strength low alloy naval grade steel joints. defence technology 11, 308317 15. razzak, m. a. (2011). heat treatment and effects of cr and ni in low alloy steel. bulletin of materials science, 34, 1439-1445. international journal of engineering materials and manufacture (2018) 3(4) 224-236 https://doi.org/10.26776/ijemm.03.04.2018.07 m. h. hasan , c. soi, a. mirzajavadkhan, s. rafieian and m. mehany department of mechanical and industrial engineering ryerson university 350 victoria street, toronto, on m5b 2k3 canada email: hasibulhasan@ryerson.ca reference: hasan, m. h., soi, c., mirzajavadkhan, a., rafieian, s. and mehany, m. (2018). experimental study and computer simulation of fracture toughness of ni base super alloys using ct specimen. international journal of engineering materials and manufacture, 3(4), 224-236. experimental study and computer simulation of fracture toughness of ni base superalloy using ct specimen muhammad hasibul hasan, chahat soi, azin mirzajavadkhan, saba rafieian and mirt mehany received: 16 september2018 accepted: 07 november 2018 published: 01 december 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract due to superior mechanical and metallurgical performance, nickel-base alloys 617 and 276 have been considered as structural material for used in complex and stochastic applications. surface irregularities such as cracks in the material may be vulnerable to the structural integrity of an engineering component. void growth behaviour is however analysed using crystal plasticity theory in nickel-based super alloys. elastic-plastic fracture mechanics base single compact tension specimen has been used to determine the j1c value as a function of temperature of austenitic alloy 617 and 276 for ductile crack growth behaviour. crack formation is appropriately explained through crack nucleation based on the microstructural heterogeneity properties of the alloys. alloy 617 showed a fair increased resistance to fracture as temperature increased from ambient to 5000c for duplicate testing, satisfying the epfm criteria. whereas the j1c values of alloy 276 increased gradually with temperature up to 300° c and due to enhanced plasticity in the vicinity of 4000 c this alloy shows inconsistent value. two-dimensional simulation of j-integral model of these nickel base super alloys at temperature range 1000c to 5000 c has been proposed. particular focus is given on the load line displacement where crack propagation occurs during the loading phase only. path independency of j-integral has been clearly demonstrated for both the alloys up to 3000 c employing finite element analysis meshing with 1922 quadrilateral 2d solid elements in ansys. cracks are typically initiated in relation to the level of strain range. a higher strain range initiates cracks due to precipitate shearing, whereas a low strain range initiates cracks with oxidation reactions and carbide diffusion. the values of k1c and crack tip opening displacement for these alloys have been calculated based on the experimental data. moreover, fracture morphology in the loading and unloading sequences near the crack tip has been analysed by sem. keywords: fracture mechanics, fracture toughness, superalloy, computer simulation 1 introduction 1.1 background due to a disparity in supply and demand, energy price is on the rise. moreover, excessive use of fossil fuels produces pollutants. for these reasons, researchers are searching for alternative energy sources. renewable energy is a promising sector as it is clean, available and cheap. wind is a major source of renewable energy. wind turbines are used to convert wind energy to electrical power. currently, worldwide 40,000 mw power is produced from wind energy and it is predicted that the growth rate will be 30% in the next decade [1]. alloy 617 and 276 were found appropriate to be used as wind turbine blade material. these alloys are also suitable for heat exchanging applications, such as in next generation nuclear plants (ngnp) [2]. therefore, metallurgical characterization of these materials is necessary. mechanical properties of a structure can be modified in many ways, for example; through the application of annealing, giving alloy 617 resistance to degradation after long-term exposure [3]. in this paper, the behavior of alloys 617 and 276 in terms of the metallurgical and mechanical properties are characterized based on the fracture toughness, particularly for wind turbine blade applications along with other conventional polyester glass fiber materials. experimental study and computer simulation of fracture toughness of ni base super alloys using ct specimen 225 1.2 material selection to be operated in harsh environments such as desert areas where dust and sandstorms are more commonly to happen, turbine blade material should sustain with high impact forces and abrasion. impact velocity is determined by wind flow velocity and the blade’s speed of revolution. due to the maximization of rotational speed at the leading edges of an aerofoil, an elastomeric material should be applied to prevent erosion. however, it is necessary to replace the tape frequently as they fail to satisfactorily absorb the concussion energy of the particulate matter. hence, blade materials should be chosen carefully to prevent damages. polyester-glass fibre blade material is suitable for high impact erosion. however, nickel-based superalloy has the potential to be used as it has a high tensile strength as well as corrosion resistance properties. in 1970, ni-base alloy 617 was developed to be used in aerospace engineering as an advanced sheet material. the significant properties of this alloy are high strength, oxidation resistance at high temperature (980°c) as well as high resistance to both creep deformation and ruptures at temperatures up to 8500c [4]. in addition, it has excellent metallurgical stability and low density, which provides a high strength-to-weight ratio. due to its oxidation resistance characteristics, alloy 617 along with alloy 276 are used in the production process of nitric acid, heat treating baskets and reduction boats in molybdenum refinement as catalyst-grid support [5]. some other high-temperature applications of alloy 617 are inducting, combustion cans, transition liners in gas-turbines, thermal energy storage capsules, manufacturing of retort furnace and gas cooled reactors. nasa has been using this alloy material for heat shielding in space transportation systems. 1.3 scope an examination on tensile deformation of alloy 617 and 276 under extensive variety of temperatures beginning from ambient to 1000°c had been completed by numerous agents [6]. surface irregularities impact the basic integrity of metallic components. control variables of development rate of surface irregularities and voids comprise of stress triaxiality, the underlying void volume fraction, lode parameters, the crystallographic orientation, the initiated slip system and the level of elastic anisotropy [7]. variable stacking conditions are forced on these segments in temperamental desert conditions and dust storms. elastic-plastic-fracturemechanics (epfm) was applied to appraise crack durability (fracture toughness) of this alloy at various temperatures [8], which happen contingent upon microstructural heterogeneities and the effect on behaviour-elastic anisotropy, morphology and crystallography with the idea of the enforced loading [9]. numerical analysis has been finished by business programming ansys utilizing finite element technique, in which conduct of crack deformations are delineated based microscopic and macroscopic structures in impact temperature reliance of yield strength [10]. in an investigation, specimens were tried by scanning electron microscopy (sem) to decide the morphology of deficiency. 2 experimentation 2.1 test material alloy 617 was custom-melted at the huntington alloys corporation, west virginia by vacuum-induction-melting (vim). rectangular and round bars were fabricated using forging and hot-rolling. after the hot-rolling operation, the thickness of rectangular bars was reduced by cold-rolling. however, residual stresses were developed from hot and cold rolling operations, which were relieved further by thermal treatment. this thermal treatment consisted of solution-annealing at 2150°f (1175°c) for variable time periods depending on the thickness of the processed bars. it produces large sized austenitic grains in alloys. after heat treatment by solution-annealing at 1163°c (2125°f), rapid cooling was done which provides a fully austenitic microstructure. table 1 and 2 provides the chemical composition and room temperature tensile properties of the material, respectively. table 1: chemical composition of alloy 617 (hv1160) and 276 (z7437cg) (wt %) heat no. c mn fe s si cu cr ni al ti co mo hv1160 0.06 0.121 0.002 0.009 0.004 0.001 22.10 54.80 0.87 0.29 12.17 9.52 z7437cg 0.006 0.42 5.9 0.001 0.008 15.8 58.3 0.1 15.9 table 2: ambient-temperature tensile properties heat no. yield strength mpa ultimate tensile strength, mpa %el %ra hardness (rb) hv 1160 371 855 78.35 61.98 86.8 z7437cg 354 794 87 60 79 hasan et al. (2018): international journal of engineering materials and manufacture, 3(4), 224-236 226 2.2 test specimens fracture toughness (j1c) of the alloy was determined by a compact-tension (ct) specimen of 25.4 mm thickness with a straight through notch. in the machining process, the longitudinal rolling direction was normal to the crack plane. figure 1. describes the configuration and pictorial view of the test specimen. 2.3 test procedure test specimens and experimental setup were done as per the procedure prescribed by the astm designation e 3131989 [12]. initially, test specimens were designed to evaluate the plane strain fracture toughness [11] based on the linear-elastic fracturemechanics (lefm) concept for alloy 617 [12]. to comply with the lefm criteria significantly ticker 20” compact tension (ct) specimens were desired and from practical standpoint it was not feasible at all. specimens cost, machine grip, test machine max, pulling capacity and furnace chamber dimensions would not permit this thick specimen to test. thus, to evaluate the fracture toughness in terms of j1c, 1 inch thick multiple ct specimens were tested using elasticplasticfracturemechanics (epfm) concept. for high strength superalloys like alloy 617, two types of testing methods exist, namely singlespecimen technique and multiplespecimen technique. five specimens were needed for multiple specimen technique but only one specimen was required for single specimen technique to determine j1c value in a particular test temperature. all tests were conducted using single specimen technique at temperature ranging from ambient to 5000c. instron testing machine (max capacity of 100 kn) and j1c fracture toughness software [13] provided by instron corporation was used to calculate and validate the fracture toughness value in terms of j1c . the compact tension specimen was pre-cracked to an approximate of 3 mm at room temperature using a load ratio(r) of 0.1 and frequency of 1 hz. maximum load for pre-cracking was maintained at 20 kn and number of cycle for pre-crack tanged from 55000 to 70000. just after pre-cracking, ct specimens was subjected to 30 loading and unloading cycles to measure load line displacement (lld) or crack opening displacement (cod). maximum travel distance of a high temperature knifeedge extensometer was kept ±2 𝑚𝑚𝑚𝑚 to measure the gap between the precracked specimens. experimental setup and a standard load versus lld plot is shown in the figure 2 and 3 respectively. the shaded area in figure 3(b) under the curve represents the energy (jintegral) required to cause each increment of crack length. fracture toughness value in terms of jintegral for each small area was calculated using the following equations. a b figure 1: 25.4 mm ct specimen (a) specimen dimensions and (b) pictorial view the j-integral value for each area was calculated using equations 1-3, given below [12, 14]. j = jelastic + jplastic [1] [2] [3] experimental study and computer simulation of fracture toughness of ni base super alloys using ct specimen 227 figure 2: j1c test set-up a b figure 3: (a) load versus lld plot and (b) areas representing j-integral where k = stress intensity factor, mpa√m = p = load, n b = specimen thickness, mm bn = net specimen thickness, mm = b, in present study w = width of the ct specimen, mm α = geometric factor of the ct specimen e = elastic modulus of the material ν = poisson’s ratio of the material, 0.3 b = uncracked ligament, mm ηpl = 2 + 0.522b/w νpl = lld / cod, mm apl = area corresponding to each loading / unloading sequence (mm2) c t s p ec im en extensometer hasan et al. (2018): international journal of engineering materials and manufacture, 3(4), 224-236 228 the combined elastic and plastic value of j then plotted against crack extension as shown in figure 4 loading compliance principle was used to evaluate each sequence of crack extension (𝑎𝑎𝑖𝑖). the following compliance equation 4 was used for 𝑎𝑎𝑖𝑖 calculation [12]. ai/w= 1.000196 – 4.06319ull + 11.242ull2 – 106.043ull3 + 464.335ull4 – 650.677ull5 [4] where be = effective thickness of the ct specimen, mm = [b – (b – bn)2/b] = b (since b = bn), in current study ci = specimen load line elastic compliance on an unloading/reloading sequence (δv/δp), mm/n δv = increment in lld/cod, mm δp = change in load, n figure 4: j-integral vs. crack-extension a power law regeneration curve was plotted in the j-integral versus crack extension (𝛥𝛥𝑎𝑎). four parallel lines including blunting line, 0.15 mm exclusion line, 0.2 mm exclusion line and 1.5 mm exclusion line were superimposed on the plot to find the calculated value of j integral. the plotted value of j-𝛥𝛥𝑎𝑎 can be considered valid if at least one j-𝛥𝛥𝑎𝑎 point lines between 0.15 mm exclusion line and blunting line. the intersection of the 0.2 mm exclusion line and regression curve usually represents the 𝐽𝐽𝑄𝑄or conditional 𝐽𝐽𝐼𝐼𝐼𝐼value as shown in the figure 5. usually jq or the conditional j1c value is considered to be the j1c value if the following two criteria are met: • thickness (b) of the specimen > [25 jq / σy], where σy = effective yield strength of the material = average of the yield and ultimate tensile strength (σys and σuts, respectively) of the material = [σys + σuts ] / 2. initial uncracked ligament (b0) > [25 jq / σy] • efforts have also been made to correlate j1c to k1c. literature [15,16] suggests that k1c can be calculated from the j1c value, according to equation 5, as given below. fracture toughness can also be measured using the crack-tip-opening-displacement (ctod) method, which is based on equation 6, given below [16]. experimental study and computer simulation of fracture toughness of ni base super alloys using ct specimen 229 figure 5: determination of jq using j-integral versus δa plot [5] [6] where δ = ctod, mm k1 = k1c value of the material, mpa√m m = constant = 2 for plane-strain condition further, tearing modulus has been calculated based on the flow stress and taking into consideration the slopes of the j-integral vs. crack extension curves. [7] [8] where, flow strength yield strength ultimate tensile strength e = young’s modulus the slope of the j-integral vs. crack extension curve hasan et al. (2018): international journal of engineering materials and manufacture, 3(4), 224-236 230 3 results 3.1 j1c values the validity criteria set by the astm designation e 813-1989 was maintained in the j1c testing procedure. jq values were obtained from it. in figure 6., average j1c values are shown for temperature ranging from 30°c to 300°c. it is observed that j1c values decrease with increasing temperature. the effect is higher for temperature up to 100°c (156 to 103 kj/m2). however, from 200°c to 300°c, the decrement is insignificant (88 to 86 kj/m2). figure 7. displays a load vs. lld plot and a j-integral vs. δa plot is shown in figure 8. figure 6: j1c vs. temperature figure 7: load vs. lld at ambient temperature experimental study and computer simulation of fracture toughness of ni base super alloys using ct specimen 231 alloy 617 figure 8: j-integral vs. δa at ambient temperature table 3: k1c and δ values vs. temperature temperature (°c) alloy 617 alloy 276 k1c (mpa√m) δ (mm) k1c (mpa√m) δ (mm) room temperature 193.7 0.20 189 0.20 100 208.9 0.22 205.5 0.21 200 216.4 0.23 213.7 0.22 300 231.5 0.24 227.4 0.24 3.2 equivalent k1c and ctod values the fracture toughness values are estimated using the j integral approach. table 3. shows equivalent k1c and the ctod values for alloy 617 and alloy 276. these values match with open literature. further, the calculated δ values for alloy 617 were very close to a range in ctod values (0.1 to 0.2) for an adequately tough material [17]. 3.3 tearing modulus values the astm designation e 8-01 was used to establish the young’s modulus for alloy 617. the tearing modulus for this alloy varies with temperature and is represented in a semi-logarithmic scale [18]. by averaging the ultimate tensile strength and yield strength the flow stress is obtained with the highest uncertainty between all conditions. based on recent research [19] large stretch zone corresponds to large tearing moduli. the furnace setback limited the study to be conducted at a specific temperature range (up to 5000c); however, the tearing modulus maintained to remain close in these temperature constraints resulting, in accurate results corresponding with the study. the values obtained show a high accuracy with the conducted study [19]. 3.4 finite element analysis of experimental work half ct specimen shown in figure.10 has meshed with 1922 quadrilateral 2d solid elements in ansys. a load of 30 kn was applied at the inside surface of the specimen hole as shown with arrows. 30 kn load was distributed equally over 15 nodes with each node subjected to 2 kn force. a symmetric boundary condition is shown for the half specimen. principal stress plots for alloy 276 at room temperature and at 400 oc are shown in figures 11 and 12 respectively. as expected the plastic zone size at 400 oc is larger compared to the plastic zone size at 30 oc. hasan et al. (2018): international journal of engineering materials and manufacture, 3(4), 224-236 232 figure 9: j-integral vs. δa at ambient temperature figure 10: ct specimen mesh showing the loading and the symmetry boundary condition. a total of 20 paths were defined around the crack tip for j integral estimation in all simulations. the j integral values for alloy 617 and alloy 276 at varying temperatures are shown in fig.13 and fig.14 respectively. it was observed that as the temperature increases the j values do not converge in the near field paths due to an excessive drop in the yield stress and enhanced plasticity. an increase in j values was recorded for increasing temperatures [20] as shown in fig.14. that also points out to the fact that the path independency of the j integral could not be maintained at higher plasticity [21]. this is shown in fig.14 where the j values do not converge easily to a single value but show a path dependency at 400 oc. path independency for j integral was observed even until 500 oc for the alloy 617 but as the temperature reaches 400 oc for alloy 276 the j values show path dependence. cracking deformation behaviour in nickel-based superalloys with stress and strain characteristics are correlated by finite element analysis of microscopic and macroscopic structures [10]. experimental study and computer simulation of fracture toughness of ni base super alloys using ct specimen 233 figure 11: principal stress distribution in ct specimen for alloy 276 at 30 oc figure 12: principal stress distribution in ct specimen for alloy 276 at 400 oc figure 13: j integral variation with increasing temperature for alloy 617. 3.5 fractographic evaluations figure 15 indicates the sem micrographs of alloy 617 that were sampled and experimented at room temperature. three different sections are illustrated by the micrographs each causing a change in morphology. fatigue precracking results in mild striations in one region; however, the vivid striations are caused by loading and unloading sequences and the last region shows dimples on the surface which result from fast rupture. changes in microstructure, as well as applied strain range due to high temperatures, causes a decline in fatigue life in alloy 617 [22]. hasan et al. (2018): international journal of engineering materials and manufacture, 3(4), 224-236 234 figure14: j integral variation with increasing temperature for alloy 276 figure 15: sem micrographs of sampled specimens experimental study and computer simulation of fracture toughness of ni base super alloys using ct specimen 235 4 conclusions the focus of this study was on the evaluation of fracture toughness behaviour of alloys 617 and 276. the key results obtained from the investigation are summarized below. 1. the j1c values fulfilled the legitimacy requirements dictated by the astm designation e 813-1989. 2. the effect of temperature on j1c value for alloy 617 is not that much significant up to 5000c. the reduction in the j1c value from 200 to 500°c was minimal. further, the tearing modulus was changed insignificantly along with the temperature as expected. 3. an abrupt increase is observed in the value of j1c for alloy 276 from 400°c temperature to 500°c, due to enhanced plasticity and path dependency. 4. j values for both the alloys show path independency up to 300° c for an insignificant amount of plastic zone at the crack tip. 5. experimental results of j values and path independency were validated by the finite element analysis in ansis. 6. dimpled microstructures and striations are revealed from the fractographic evaluations of both broken ct specimens. acknowledgement the authors would like to appreciate very much the experimental and analytical support from department of mechanical and industrial engineering at ryerson university in doing this research. references 1. n. dalili, a.edrisy and r. carriveau “ a review of surface engineering issues critical to wind turbine performance” renewable and sustainable energy reviews, 13 (2009) 428-438. 2. paul m. mathias and lloyd c. brown “thermodynamics of the sulfur-iodine cycle for thermochemical hydrogen production” japan march 2003, 68th annual meeting of the society of chemical engineers, japan the university of tokyo 3. akbari-garakani, m., & mehdizadeh, m. (2011). effect of long-term service exposure on microstructure and mechanical properties of alloy 617. materials and design, 32(5), 2695-2700. doi:10.1016/j.matdes.2011.01.017 4. y. sakai, t. tanabe, t. suzuki, h. yoshida, “corrosion behavior of inconel 617 in a simulated htgr helium”, transactions of national research institute for metals, vol. 27, 1985, pp. 20-27 5. u. bruch, d. schumacher, p. ennis, e. heesen, “tensile and impact properties of candidate alloys for hightemperature gas-cooled reactor applications”, nuclear technology, vol. 66, 1984, pp. 357-362 6. ajit roy, muhammad h. hasan, joydeep pal “creep deformation of nickel-base superalloys at different temperatures”, materials science and engineering: a 520 (2009) 184-188. 7. yu, q. m., hou, n. x., & yue, z. f. (2010). finite element analysis of void growth behavior in nickel-based single crystal superalloys. computational materials science, 48(3), 597-608. doi:10.1016/j.commatsci.2010.02.028 8. vikram marthandam, “tensile deformation, toughness and crack propagation studies of alloy 617”, ph.d. dissertation, mechanical engineering, april 10, 2008 9. “wan, v. v. c., jiang, j., maclachlan, d. w., & dunne, f. p. e. (2016). microstructure-sensitive fatigue crack nucleation in a polycrystalline ni superalloy. international journal of fatigue, 90, 181-190. doi:10.1016/j.ijfatigue.2016.04.013” 10. mukai, y., kagawa, h., & okazaki, m. (2015). finite element analysis on crack tip deformation behavior under mode-ii loading in single crystal superalloy. key engineering materials, 665, 281-284. 11. xiao guang, zu han lai, “ realization of single specimen analytical method of j1c determination by using compact tension loading”. engineering fracture mechanics , vol 34 no.5/6, pp 1013-1021, 1989 12. astm designation e 399-1999. “standard test method for linear-elastic plane-strain fracture toughness k1c of metallic materials.” american society for testing and materials (astm) international 13. astm designation e 813-1989. “standard test method for j1c, a measure of fracture toughness.” american society for testing and materials (astm) international. 14. instron corp. fast track 2 j1c unloading compliance software. 15. structural integrity associates inc. “nonlinear fracture toughness testing.” technical paper. 16. perez, j.e., ipiñaa, yawnyb, a.a., stukeb, r. & oliverb, c. gonzalez. “fracture toughness in metal matrix composites.” materials research 3 (2000): 74-78. 17. hertzberg, richard w. deformation and fracture mechanics of engineering materials. ny: john wiley & sons, 1996. 18. astm designation e 8-2001. “standard test method for tension testing of metallic materials” 19. k. krompholz, e.d. grosser & k.ewert. “determination of j-integral r-curve for hastelloy x and inconel 617 up to 1223 k using potential drop technique” materials science and engineering technology, volume 13 , issue 7, page 236-244, july 1982. hasan et al. (2018): international journal of engineering materials and manufacture, 3(4), 224-236 236 20. hsiao-hung hsu, yen-chie wu, leu-wen tsay, notch brittleness of ti-15v-3cr-3al alloys, materials science and engineering a, 545 (2012) 20-25. 21. w. brocks and i. scheider, numerical aspects of the path-dependence of the j-integral in incremental plasticity: how to calculate reliable j-values in fe analyses, technical note gkss/wms/01/08, internal report, institut fur werkstofforschung. (2001) 22. dewa, r. t., kim, s. j., kim, w. g., & kim, e. s. (2017). effect of strain range on the low cycle fatigue in alloy 617 at high temperature. metals, 7(2), 54. doi:http://dx.doi.org.ezproxy.lib.ryerson.ca/10.3390/met7020054 23. riveros, g. a. , numerical evaluation of stress intensity factors (ki) j-integral approach. coastal and hydraulics engineering technical note, erdc/chl chetn-ix-16. (2006) vicksburg, ms: u.s. army engineer research and development center. 24. h ching, c liu, s yen, fe calculations of j-integrals in a constrained elastomeric disk with crack surface pressure and isothermal load, air force research laboratory (afmc),afrl/prsm,10 e. saturn blvd.,edwards (2004) afb,ca,93524-7680 25. “ctod testing.” may 25, 2009. <http://www.twi.co.uk/content/jk76.html>. http://dx.doi.org.ezproxy.lib.ryerson.ca/10.3390/met7020054 1 introduction 1.1 background 1.2 material selection 1.3 scope 2 experimentation 2.1 test material 2.2 test specimens 2.3 test procedure 3 results 3.1 j1c values 3.2 equivalent k1c and ctod values 3.3 tearing modulus values 3.4 finite element analysis of experimental work 3.5 fractographic evaluations 4 conclusions references international journal of engineering materials and manufacture (2018) 3(3) 162-170 https://doi.org/10.26776/ijemm.03.03.2018.05 the scenario of supply chain management in kuwait food industry abdullah e. m. f. alrashidi, muataz hazza faizi al hazza and ahsan ali khan received: 29 august 2018 accepted: 10 september 2018 published: 15 september 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract supply chain management (scm) has been well known to influence the company performance in food manufacturing industries. however, the implication of scm depends on type and culture of the companies. this paper presents the scenario of scm in kuwait food industry. in this study quality, time, information, flexibility, and integration have been selected as variables to predict their influence on kuwait food industries. the methodology of the study was developed where five hypotheses have been proposed on the relationship among the selected factors and the performance. to evaluate the hypotheses, an examination through a questionnaire was conducted, followed by data analysis using statistical package (spss) and minitab applications. it was found that out of five proposed hypothesis only two of them were supported by the analytical results. the accepted two hypothesis are related to the quality of supply chain and time management in supply chain to positively effect on the performance of food manufacturing companies. oher three hypotheses were rejected. information network, company flexibility and integration among the supply chain components were found to have no significant influence on the performance of food manufacturing industries in kuwait. this study ranked the factors to prioritize to improve the performance. keywords: supply chain management, kuwaiti food industry, quality, balanced score card, performance prism 1 introduction one of the performance effects commonly known in many organizations is supply chain management (scm). it can be defined as the administrative aspect of an interconnected businesses network dealing in the product ultimate provision and service packages needed by the end customers. scm spans all manufacturing activities and raw materials storage, inventory of the process, and finished items from the point-of-origin to the point-of-consumption. the purpose of this study is to investigate how different factors in scm affect the food manufacturing companies’ performance as well as to introduce a framework for performance improvement. this is supported with a survey among managers in different food industries to find out the relationship between these factors and food manufacturing companies’ performance along with using statistical package for the social sciences (spss) and minitab software to find out the most crucial factor that affects the performance food manufacturing company. the theory on organizational extension gave the birth to the initiating idea of scm philosophy [1]. the hobbs’ postulate was validated in a marketing framework, urged to extend the organization and all its distribution channel members near to the porter’s value system concept [2]. the tremendous technological advancement and the globalization of business have required companies to expand beyond cost and to prominence quality, speed, flexibility and agility. competitive advantage for many manufacturers now rests upon their ability to monitor ongoing product, process innovation, and superior manufacturing. it also depends on the continuous development of current products as well as developing a continuous line of new service quality concept [3]. however, nowadays, companies are struggling to enhance their performances in all aspects specially to increase the quality at reduced cost. improving the scm is one of the ways to solve the issue. thus, in this study, scm and its consequence on food manufacturing companies’ performances will be studied. as such, this research set the following objectives. a. e.m.f. alrashidi1 , m. h. a. f. hazza2 and a. a. khan3 department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia 1e-mail: eng-alrashidi@live.com 2e-mail: muataz@iium.edu.my 3e-mail: aakhan@iium.edu.my reference: alrashidi, a. e. m. f., muataz, m. h. a. f. and khan, a. a. (2018). the scenario supply chain management in kuwait food industry. international journal of engineering materials and manufacture, 3(3), 162-170. the scenario supply chain management in kuwait food industry 1. to study the factors in supply chain management that are influencing the food manufacturing companies’ performance. 2. to determine the importance of different factors of the supply chain management and to identify the most affecting factors on the company performance. 3. to establish the connection between the independent factors and the dependent factor as well as the relationship between the independent factors themselves. 1.1 research questions this research is to find the relationship between the critical factors and the company’s performance by focusing the major issues in scm. the main question of this research is how the scm can contribute to get a better result and increase an organization's productivity. the research will investigate on the factors such as quality, information, flexibility; integration and time achieve high performance in kuwait food manufacturing companies. the research questions are as follows: 1. what are the scm important and critical factors that influence the performance of the companies in the food manufacturing industries? 2. what are the actions to manage these factors to attain the desired improvement in an organization? 3. what type of model will be applicable to measure the performance within an organization? 4. how far the research participants know about supply chain management and its related knowledge for procurement, manufacturing, and technologies? 1.2 statement of hypotheses five variables affecting the food manufacturing companies’ performance in the supply chain have been chosen. the selection process involved a review study and an extensive research on the scm and performance measurement systems. the selected factors and variables are time, quality, information, integration and flexibility. the hypotheses were generated according to each of the variable: h1: the higher the quality in each part of supply chain, the higher the performance of food manufacturing companies h2: time management in supply chain has a positive impact on the performance of food manufacturing companies. h3: the better the information network among the supply chain, the higher the influence on the performance of the food manufacturing companies. h4: the company’s flexibility to the changes of business environment has a high impact on performance. h5: the integration among all components of supply chain has a great impact on the performance of food manufacturing companies. 1.4 conceptual framework a few studies have been reported in the performance of food manufacturing companies. the selection of the variables involved different item from the one listed in the hypotheses, and comparisons were made to measure the performances. the current work is not identical nor similar to those has that been performed. instead, it can be said as a complementer and contrast the other previous studies. the study aims to apply variables that are often suggested by other authors and appear to affect the performance of food manufacturing companies of the entire supply chain. as presented a classification in the literature, which involved flexibility, quality, cost and time [4]. it is a practical and convenient tool for analysing a system in an organization. the focal point of the investigation was the impact of information structure towards a supply chain performance [4]. as a complementary of the study by zhao and zhang [5] studied the effect of the data sharing towards the same performance. the current work selected five factors to be assessed in terms of their performance in the supply chain. additionally, to investigate the selected variables relation towards the performance of the companies, a conceptual framework is also introduced in this work. inclusive for the variables in this work are time, quality, flexibility, integration and information. the dependent variable is the performance of food manufacturing companies. the authors suggest the following framework to investigate the relationship between the variables and the effect of these factors on food manufacturing companies’ performance. 2 supply chain operation reference the development on supply chain operation reference (scor) has been provided by the supply chain council (scc); an independent and a non-profit organization are used in combination with the attributes of performance in this model. these attributes are features of supply chain, which permit the analysis and the evaluation in contrast to other supply chains. the leading role of scor is the description of measurement and the assessment of the settings of supply chain. according to scc, scor should be a progression reference model, which gives an interactive language in the communication between supply-chain partners. the postulation of the model was developed on four stages. these stages were the basis in drawing and defining a guide to accomplish the hypotheses of the study. it is therefore concluded that the focus of scor is the integration of all supply chain components and associated parties, from suppliers to suppliers, suppliers to costumers, or customers to customers. in terms of performance, the model 163 alrashidi, muataz and khan (2018): international journal of engineering materials and manufacture, 3(3), 162-170 also enumerates the influencing effects of quality and information towards the system. figure 1 is an illustration of the factors that influence the performance based on the scor model. 3 research methodology data sampling concerns the process of estimating the characteristics of the whole population from the selected subset of individuals inside a population. in this research, managers from various food industries in kuwait are the respondents. the selected ones were those who have a good knowledge in the concept of supply chain management (scm) and should be familiar with the position of workers in different levels of the company. it can involve also workers as long as they are aware of scm and its relationship with the industrial engineering. the performance quantification from the food manufacturing companies was measured through a system built out of a five-metrics set. each of the metric component was selected according to the previous studies and literature review performed by other researchers and investigators on the focused topic [6, 7]. the relevancy and reliability of the composed hypotheses was tested. the evaluation employed the distribution of the questionnaire survey among managers and executive of diverse-positions, as well as its analysis with statistical tools of spss and minitab to assist the decision making process. the process of this research methodology is presented in figure 2. 3.1 method and instruments spss is a robust and responsive application for decision-making process. it has been utilized by many experts for analysing both qualitative and quantitative aspects of a decision [8]. the application has the widest services in social science that serves the function of statistical analysis. many parties, including governments, market researchers, education researchers, health researchers, survey companies, marketing companies, and many others, benefit from the utilization of this software. the fundamental features of the application include a data documentation feature, where the data file store the metadata dictionary, and a data management feature, where the creation of data derivation, its case selection, and file reshaping occurs. the two are counted as an addition to the basic feature of the statistical analysis. the application itself is deemed as one of the most exploited methods when it comes to a decisionmaking process with several criteria and sub-criteria, through selective alteration and prioritization processes. the questionnaire includes an array of questions to be sent to the respondents, in an expectation for a response, which is sent by the investigator or researcher to the targeted peers. most questionnaires are self-administered, in that it is distributed to the targeted respondents, asking them to complete it, and resending it back to the owner of the questionnaire [9, 10]. an interview, at the other side, can be considered as an alternative form of a questionnaire, where the series of questions are addressed personally to the respondents [8]. combining semi-structured interviews and structured questionnaires have been routinely performed to attain confirmatory results, regardless the differences in the methods of information collection, analysis, and data interpretation. a comparative study on nineteen questionnaire-interviews even concluded that the statistics on their consistency and consensus between their methods were insufficient. the alignment issue of the processed data generated from the two different methods were described in the evaluation of a questionnaire-interview study of teacher apprehension. figure 1: conceptual framework 164 the scenario supply chain management in kuwait food industry figure 2: research methodology the explanation for the poor alignment can be associated to the discrepancy in the data collection procedures. the unreliability and ramification of the investigated construct, the adversity in data correlation and comparison, possible confusion and misinterpretation from some questionnaire cues, paramount sensitiveness to context, as well as preeminent control of content exposure are also possible reasons of discrepancy. the investigators incorporates a detailed, straightforward, and highly contextualised presentation for the construct made; collecting diversified types of data in a minimum time constraint; and estimating the agreement between methods using consistency statistics. however, the substantial alignment could possibly direct the process to the loss of capacious complementary data as its confirmation cost by allowing each method to be analysed in its respective right. in the educational environment, the utilization of the combined questionnaire-interviews has found to be common [10, 11]. although questionnaires are capable of providing patterns confirmation within a large population, a qualitative interview data often bring together some better insights on the actions, attitudes, and thoughts of the respondents [12]. 3.2 data collection and analysis starting from 15th june 2011 the data collection process was carried for the next two months. in the early date, the targeted companies should have received the questionnaires designated for them. consecutively, the targeted respondents were given the ample time to fill up the information requested in the questionnaire. a 90% of the distributed questionnaire was received. the quantity of the questionnaires collected was 60 out of 67 questionnaires. the analytical stage of the study involved the empirical and descriptive methods of research analysis. translation of the returned data with a numerical scale was performed and then spss analyse was conducted. the formulation of the performance measurement system involved the stages to evaluate the efficiency and productivity of the area is most relevant to the engineers in the manufacturing process. 4 results and data analysis the findings of the study are presented in this chapter. the analytical data of respondent as well as the feedback collected from the survey were discussed and analysed in the next sections and subsections. correspondingly, the results were discussed by using spss software analysis to process the data. the results were then compared with the hypotheses proposed in this research and new suggestions were then demonstrated based on the optimum findings of the study. 4.1 results the questionnaire of the survey was intended to draw the connection between food manufacturing companies’ performance and quality, time, information, flexibility and integration as well as how these parameters influence each other in supply chain and how they could be managed to obtain better performance in an organization. 165 alrashidi, muataz and khan (2018): international journal of engineering materials and manufacture, 3(3), 162-170 questionnaire was divided into two parts. firstly, it includes questions about demographic data of respondents as well as to what extent respondents are familiar with supply chain management, new scm technologies and organizational structure. data summary is presented as qualitative analysis. the analytical data of the respondents about gender, education, age, profession as well as knowledge in scm and its technologies are presented in table 1. most of the 48 respondents were male. the age of respondents was between 26 to 46 years. the result showed the respondents were mostly educated as the majority obtained bachelor or master’s degrees. nearly 50% of the respondents are employees in corporations with 100-500 members. the results of the survey would be preferable if most of the respondents were in corporations with larger number of workforces. a percentage of 70 of respondents claimed an average or high knowledge about management of supply chain, which showed satisfactory percentage for conducting the survey. a value of 9% of the respondents was aware of scm technologies, which indicates that the scm technologies are not well known in their companies. secondly, comprises of questions that concern about the connection between independent and dependent variables to examine the research hypotheses. the questions related to each independent variable are grouped together. respondents demonstrate extent of their agreement or disagreement with the research propositions by answering the questions of part b. the result obtained after analysing these data are provided as quantitative analysis. 4.2 data analysis the spss and minitab software were applied as tools to analyse the data by means of multiple regression method and factor analysis method after the examination the reliability and normality of the data. normality is the first phase of screening of the data, where the data characteristics are being explored. normality of assumption is a precondition for many inferential statistical methods. there are several ways to discover the assumption, such as leaf plot, histogram, box plot and stern. for resting the normality, factors related to each variable are grouped together and analysed. 4.2.1 multiple regressions the term is used to acquire about the relationship between several predictor or independent variable and a criterion or dependent variable, which is fitted for this research. the multiple regressions results are calculated based an equation, which expressed the relationship between factors influencing an independent variable [13]: 𝑌𝑌 = 𝑎𝑎 + 𝐵𝐵1𝑋𝑋1 + 𝐵𝐵2𝑋𝑋2+⋯+ 𝐵𝐵𝑛𝑛𝑋𝑋𝑛𝑛 (1) table 1: demographic distribution of respondents category frequency percent valid percent cumulative percent gender male 48 100.0 100.0 100.0 le ve l o f ed u ca ti o n diploma 11 22.9 22.9 22.9 bachelor’s degree 24 50.0 50.0 72.9 post degree 5 10.4 10.4 83.3 other 8 16.7 16.7 100.0 total 48 100.0 100.0 a g e 30 or below 4 8.3 8.3 8.3 31-35 5 10.4 10.4 18.8 36-40 11 22.9 22.9 41.7 41-40 8 16.7 16.7 58.3 46-50 9 18.8 18.8 77.1 51-55 7 14.6 14.6 91.7 above 55 4 8.3 8.3 100.0 total 48 100.0 100.0 h o w m an y em p lo ye es i n th e co m p an y below 100 employees 5 10.4 10.4 10.4 100-500 employees 37 77.1 77.1 87.5 more than 500 employees 6 12.5 12.5 100.0 total 48 100.0 100.0 100.0 where bn is the regression coefficient, expressing the amount of the dependent variable, (y) varies when varying the corresponding independent factor. the value a is the constant, where the regression line intercepts the y-axis; represents the amount the dependent y when all the independent variables are zero. the standardized version of the b coefficients is the b weights, and the ratio of the b variables. associated multiple regression is r, multiple correlation, which is the percent of variance in the dependent variable explained collectively by all the independent 166 the scenario supply chain management in kuwait food industry variables. in order to run the regression test, factors related to each variable are grouped together and analysed versus independent variable namely food manufacturing companies’ performance [14, 15]: 1. the multiple correlation coefficient is r: a relation between performance and quality. the value of r= 0.494, is acceptable but not preferable since it is not regulated to an extreme side. 2. r squared value expressed the variability in loyalty is regarded by the independent variable. the value of r squared= 0.244 is slightly small and demonstrates the predictors are not considering the performance strongly. 3. based on the findings above, the model of regression can be presented. the result indicates high correlation between performance and two factors viz. quality and time, although the result is not favourable to support the study hypotheses. 4.2.2 factors analysis the factors analysis is conducted to investigate how predictors independently affect each other as well extract the factors, which they are highly correlated together. this test will help indicate which factors are more effectively influence the independent variable as well as affect each other. a likert scale is a type of psychometric scale often used in questionnaires related to psychology. it was named and developed after the organizational psychologist rensis likert. on a questionnaire or a survey, typically, likert items are in the format of strongly disagree, disagree, neither agree nor disagree, agree, and strongly agree. there is diversity of possible scales of responses (1-3, 1-5, 1-7, and 1-9). all of the mentioned odd-numbered scales possess a middle value and often regarded as undecided or neutral. a forced-choice response scale maybe used with responses with an even number and no middle undecided or neutral option. in this case, the responder is obliged to decide whether they svelte more in the direction of the agree or disagree end of each item’s scale. a numerical score is assigned for each statement, which is in the range of 1 to 5. a numerical score is given to each level of agreement and the total score of the responders is calculated by means of the scores sum. the respondent’s opinion is disclosed by the total score obtained. likert scale is of ordinary type as it enables an individual to rate attitudes, however, it does not analyse the difference between attitudes. the same amount of efforts is required to generate as thurston scale, which is regarded as more discerning and solid due to the responses’ large range specified in likert scale. the number of statement of a typical scale of likert scale ranges between 2030 statements. to design a good scale of likert, a large statements pool that are relevant to the attitude measurement ought to be produced and then from statements pool, the ones which are indefinite and nondiscerning must be abolished. therefore, likert scale is a scale of five-point ranging from “strong agreement” to “strong disagreement”. there is involvement of judging gap in this approach. the studies of correlation are used to examine the occurrence of relationships among variables. there are three possibilities of a correlation study results, which are a negative correlation, a positive correlation and no conclusion. the coefficient of correlation is a quantity that assess the strength of correlation and may fall in the range of (-1 to 1). the table below shows how the factors affect each other either negatively or positively through the application of eqn 2. in likert scale, responders are requested to specify the agreement or disagreement amount in form of strong agreement to strong disagreement, using a scale of oneto five-point system. for multiple questions, the same style is applied. this procedure of categorical ranking could be extended to a procedure of evaluation in a straightforward way that applies the numbers full scale instead of verbal categories. quantitative analysis represented that among the group of five independent variables proposed for this research, correlation exists and should be reconsidered. two of these variables namely quality and time were accepted as high output of the regression analysis and the regression model for company performance (cp) was presented by eqn 3. (2) 𝐶𝐶𝐶𝐶 = 0.00638 + 0.246 𝑄𝑄𝑄𝑄𝑎𝑎𝑄𝑄𝑄𝑄𝑄𝑄𝑄𝑄 + 0.226 𝑇𝑇𝑄𝑄𝑇𝑇𝑇𝑇 + 0.187 𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝑇𝑇𝑎𝑎𝑄𝑄𝑄𝑄𝐼𝐼𝐼𝐼 + 0.174 𝐹𝐹𝑄𝑄𝑇𝑇𝐹𝐹𝑄𝑄𝐹𝐹𝑄𝑄𝑄𝑄𝑄𝑄𝑄𝑄𝑄𝑄 + 0.167 𝐼𝐼𝐼𝐼𝑄𝑄𝑇𝑇𝐼𝐼𝐼𝐼𝑎𝑎𝑄𝑄𝑄𝑄𝐼𝐼𝐼𝐼 (3) table 2: ranking of likert scale strongly disagree (1) disagree (2) neutral (3) agree (4) strongly agree (5) rank percentage % quality 2 9 25 102 150 1st 25% time 7 23 28 136 94 2nd 24% information 19 72 51 90 56 3rd 18% flexibility 30 90 45 70 53 4th 17% integration 41 87 44 77 39 5th 16% 167 http://en.wikipedia.org/wiki/likert_scale alrashidi, muataz and khan (2018): international journal of engineering materials and manufacture, 3(3), 162-170 table 3: results correlation scm qualit y time information flexibility integration time pearson correlation -0.051 p-value 0.923 information pearson correlation 0.08 0.545 p-value 0.88 0.263 flexibility pearson correlation -0.135 0.398 0.237 p-value 0.799 0.434 0.651 integration pearson correlation 0.511 0.261 0.267 0.311 p-value 0.33 0.618 0.6 0.549 company performance pearson correlation 0.494 0.427 0.101 0.0595 0.09 p-value 0.32 0.398 0.848 0.213 0.014 there are many coefficients for reliability. cronbach's alpha is one of the most common coefficients. as cronbach's alpha could be regarded as coefficient of correlation, it has a range of 0 to 1 while the determined alpha value for the study factors is 0.494, which is not highly acceptable. some of the factors would result a slight increase in the cronbach's alpha, but control the lead-time, quality of production, ability to respond to markets change, and flexibility to change distribution channels. 4.3 discussions this study was directed to determine the significance of some factors in management of supply chain and their influence on the performance of food manufacturing companies. the research considered how the factors such as quality, information, time, flexibility and integration should be managed in the supply chain to ultimately achieve more efficient result in company as well identifying the more important and significant factors to be considered. though previous studies indicated that all these factors could more or less influence the performance in an organization, this study indicated the degree of importance of variables as compare to the others. according analysis of regression as well as factor analysis conducted in the previous chapter, quality and time were confirmed to be affecting the food manufacturing companies more effectively. the data analysis demonstrated that managing the quality and time in supply chain is more significant for the companies to accomplish higher performance. by considering the analysis of data that support or contrary to the hypotheses of study, the hypotheses can be divided in two categories: accepted hypotheses: h1: the higher the quality in each part of supply chain, the higher the performance of food manufacturing companies h2: time management in supply chain has a positive impact on the performance of food manufacturing companies. rejected hypotheses: h3: the better the information among the supply chain; the higher the influence on the performance of the food manufacturing companies. h4: the company’s flexibility to the changes of business environment has a high impact on performance. h5: the integration among supply chain has a great impact on the performance of food manufacturing companies. 5 summary this research was conducted in order to determine the effect of quality, time, information, flexibility and integration on performance. these factors were chosen by reviewing the previous studies. a questionnaire survey was carried out to investigate the proposition of the research. the data gathered from the survey have been analysed by the spss software as well as minitab program. in addition, the result of the data collected indicates that two of these variables namely quality and time are affecting the food manufacturing companies’ performance according to related hypotheses. relationships of the independent factors were explained as well as measuring procedures of the most important independent factor were mentioned. although other variables and the hypotheses were not completely supported by the findings, further studies are essential and different variables can be employed to additional investigate to the food manufacturing companies’ performance in supply chain. rejecting hypotheses illustrate the data that were obtained from the responders are not supportive of the hypotheses. this may be due to following causes: 1. the attained data from respondent are not accurate as not all contributing responders are expert supply chain management. 2. saudi industries are not enough flexible to the environment changes and adapting to new situations is not taking seriously. 168 the scenario supply chain management in kuwait food industry 3. saudi industries and companies are not as sensitive as the developed countries to the time factor and business in saudi is running more smoothly and steady. 4. a correlation might occur between the independent variables and they could have a negative impact on each other, therefore, other possible combinations need to be examined. 5.1 implication and recommendation this research has been conducted in order to determine the most important factors in supply chain management and then investigate how they supply chain in a company can be modified or refined to improve their efficiency and effectiveness as well as to. the research has illustrated some of the factors affecting the performance. this research examined the relationship between five independent variables and for performance of food manufacturing companies. the result indicated that each variable has its own density of effect on the food manufacturing companies’ performance. further studies are recommended on this topic but considering dissimilar variables as well as different combinations in order to refine the investigation on the factors effecting the performance and efficiency in supply chain namely: • investigating the relationship with suppliers and effect of it on organization • how information technology can contribute in empowering the supply chain and enhancing the performance • is it advantageous to be more flexible in organization • how to improve the deal between the company and suppliers? 5.2 limitations of the study this research is based on a short and quick survey on scm to identify the relationship among different variables and performance of food-manufacturing companies. in this research, the following limitations are observed.  in supply chain, there are several variables affecting the performance; study based on few factors only may not provide the real scenario.  the demographic data indicates respondents were not all at the managerial level as well as not highly familiar with supply chain management and company structure. access to desirable number of experts on supply chain management in order to conduct the survey is difficult. acknowledgement the authors would like acknowledge the time and effort provided by the respondents. the authors also would like to appreciate very much the support from department of manufacturing and materials engineering to facilitate data collection and proving the analytical support. references 1. hobbs, j. e (1996). a transaction cost approach to supply chain management. supply chain management, 1(2), 15-27. 2. kumar, d. & rajeev p. v. (2016). value chain: a conceptual framework. international journal of engineering and management sciences, 7(1) 74-77. 3. lhassan, e., ali, r., & majda, f. (2018). combining scor and bpmn to support supply chain decision-making of the pharmaceutical wholesaler-distributors. in logistics operations management (gol). 4th international conference on logistics operations management. 4. neely, a. d., bourne, m. & kennerley, m. (2000). performance measurement system design: developing and testing a process-based approach. international journal of operations & production management, 20(10), 11191145. 5. zhao, x. et. al. (2002). the impact of information sharing and ordering co-ordination on supply chain performance. supply chain management: an international journal, 7, 24-40. 6. najmi, m., mohamed, h., & mukhtar, m. (2018). performance measurement of rice mills based on supply chain operation reference model. asia-pacific journal of information technology and multimedia, 7(1), 57-69. 7. savino, m. m., manzini, r., & mazza, a. (2015). environmental and economic assessment of fresh fruit supply chain through value chain analysis. a case study in chestnuts industry. production planning & control, 26(1), 118. 8. expert choice (2000). expert choice decision support software, rws publications, pittsburgh, usa. 9. callado, c., a. a., & jack, l. (2015). balanced scorecard metrics and specific supply chain roles. international journal of productivity and performance management, 64(2), 288-300. 10. al-bawab, a. a. (2017). use balanced scorecard (bsc) perspectives in the service sector: a case study on the jordanian private universities. international business research, 10(8), 192-203. 11. brookhart, s. m. & durkin, d. t. (2003). classroom assessment, student motivation, and achievement in high school social studies classes. applied measurement in education, 16(1), 27-54. 12. kendall, l. (2008). the conduct of qualitative interview: research questions, methodological issues, and researching online. 169 alrashidi, muataz and khan (2018): international journal of engineering materials and manufacture, 3(3), 162-170 13. prakash g. (2015). a framework for sustainable food supply chain: reflections from the indian dairy producers. in: kachitvichyanukul v., sethanan k., golinskadawson p. (eds) toward sustainable operations of supply chain and logistics systems. ecoproduction (environmental issues in logistics and manufacturing). springer, cham 14. suhaiza, z. & premkumar, r. (2005). supply chain integration and performance: us versus east asian companies, supply chain management: an international journal, 10(5), 379-393. 15. tracey, m. & lim, j. s. (2005). the impact of supply-chain management capabilities on business performance, supply chain management: an international journal, 10(3), 179-191. 170 1 introduction 1.1 research questions 1.2 statement of hypotheses 1.4 conceptual framework 3 research methodology 3.1 method and instruments 3.2 data collection and analysis 4 results and data analysis 4.1 results 4.2 data analysis 4.2.1 multiple regressions 4.2.2 factors analysis 4.3 discussions 5 summary 5.1 implication and recommendation 5.2 limitations of the study references international journal of engineering materials and manufacture (2020) 5(2) 55-61 https://doi.org/10.26776/ijemm.05.02.2020.04 i. o. ambali 1 , y. l. shuaib-babata 1 , h. k. ibrahim 2 , l. b. abdulqadir 3 , n. i. aremu 1 , and t. o. ibraheem 1 1 department of materials & metallurgical engineering, university of ilorin, ilorin, nigeria 2 department of mechanical engineering, university of ilorin, ilorin, nigeria 3 department of mechanical engineering, kwara state polytechnic, ilorin, nigeria e-mail: sylbabata@unilorin.edu.ng reference: i. o. ambali, y. l. shuaib-babata, h. k. ibrahim, l. b. abdulqadir, n. i. aremu, and t. o. ibraheem (2020). production of abrasive sandpaper using periwinkle shells and crab shells. international journal of engineering materials and manufacture, 5(2), 55-61. production of abrasive sandpaper using periwinkle shells and crab shells ambali ibrahim owolabi, shuaib–babata yusuf lanre, abdulqadir lawal babatunde, ibrahim hassan kobe, aremu ishaq na’allah and ibraheem taofeek olawale received: 24 april 2020 accepted: 15 may 2020 published: 30 june 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 abstract in this study, the properties of periwinkle shell and crab shell grains, such as hardness, compressive strength and wear resistance were examined for their suitability as abrasive materials. the binding effect of polyester resin at high concentration was also considered. through the process of crushing, grinding and subsequently sieving using astm e11 set of sieves, the shells were processed into grit standards grain sizes of p40 and p60. furthermore, by mixing and mould compression using a hydraulic press polymer matrix composite with particles varying from 96 wt.% to 92 wt.% and resin 3 wt.% to 7 wt.% with 1 wt.% each of cobalt naphthalene and methyl ethyl ketone peroxide hardener respectively were developed from the grits. it was found that, with an increase in polyester resin content, the hardness and compressive strength increased, while the wear rate decreased. the composition with 92 wt.% periwinkle shell grains to 7 wt.% polyester resin was found to be with the most improved abrasive properties. keywords: abrasive properties, periwinkle shell, crab shell, wear rate 1 introduction in shaping, finishing and polishing of other materials, abrasive materials which are very rigid mineral materials are used. the abrasive materials are processed in a furnace after which they can further be crushed and sifted into different grain sizes called grits [1]. hardness, brittleness, character of fracture, toughness, grain shape and grain size, purity and uniformity of the grains are considered as the most significant physical properties of abrasive materials [2]. sandpaper is an abrasive grain material that is used to make the surface of work-piece smoother or rougher if rubbed with the surface of the work-piece. small amounts of the work-piece surface materials are removed in the process. this is useful in removing unwanted layer or coating, such as dirt, paint and stain, on surface of a material [3-4] to attain precision and good surface appearance. sandpaper consists of abrasive grain material fixed to a flexible backing material by an adhesive [5]. in nigeria, available synthetic materials abrasive materials are either very scarce or very expensive; this is mainly due to non-availability or high cost of the materials (such as silicon carbide, aluminium oxide and aluminium silicate) used in their production [6]. meanwhile, the available natural materials, like lime, chalk and silica, aluminium silicate, kaolinite, diamond and diatomite are found to be less effective due to impurity nature of the materials [7-8]. in developing countries like nigeria, bio-wastes (such as shells from crabs, periwinkles, snails, etc) which are from biological organisms are dumped indiscriminately and as such results to environmental nuisance. thus, the need to convert these bio-wastes into industrial tools like sandpaper are essential for economic development and sustainability, which will assist in addressing the most needed economic diversification in nigeria to quench the effect of covid-19 on the nation’s economy. periwinkles are marine molluscs (gastropods) with thick spiral shells. the periwinkle shells are the outer casing of the sea snails which are hard with swollen rough surfaces and usually regarded as waste after consuming the inner fleshy part of the snail. as they grow, gastropod shells follow a mathematically ordered pattern. thus, as they increase in size, they retain their basic form. it is the presence of the high level of concentration of calcium carbonate (caco3) that makes the shell hard. in an experiment on the chemical content of the periwinkle shell and its suitability in thin layer cinematography carried out by orji et al. [9], the shells were found to contain very high percentage of caco3, production of abrasive sandpaper using periwinkle shells and crab shells 56 thereby making them a probable source of caco3. the high content is responsible for it being considered for the experiment. crabs are crustaceans that are not readily available to people around landlocked areas, but available in high quantities in coastal areas. the swimming crab, callinectesamnicola is an important food item in coastal waters of west africa. it belongs to the phylum arthropoda, order decapoda and family portunidae. crabs are high in calcium; potassium, magnesium, and manganese which make them possess hard and rigid exoskeleton [10]. other functions of this mineral include formation of endoskeleton structure and maintenance of colloidal system. the crab shell contains 40-70% calcium carbonate which varies according to the species; the calcium carbonate can be further processed into calcium hydroxyapatite [11]. in engineering applications, these sea shells are being used as substitutes for aggregates (chippings) especially in the coastal areas where aggregates are lacking. some researchers have conducted exploratory studies on the partial or total substitution of waste sea shells with coarse aggregate for the production of mortar and concrete used for civil construction. in the study carried out by adewuyi and adegoke [12], it was found that the replacement of granite with 35.4 42.5 % waste periwinkle shells did not compromise the compressive strength of the resulting concrete and made 14.8 17.5 % saving in material cost. in glass manufacturing, the suitability of periwinkle shells as a substitute for lime was examined by malu and bassey [13]. a proximate analysis of periwinkle shell by malu and bassey showed that the shell contained calcium oxide (38.4%), silicon (iv) oxide (0.014%), magnesium oxide (18.70%), aluminium trioxide (0.211%) and iron oxide (0.019%) which are important minerals suitable for glass production [13]. emery cloth/sandpaper was manufactured from locally sourced materials by wai and lily [14]. silicon sand (quartz) which was sieving into fine grit 180µm and coarse grit 50µm was used as abrasive grit with epoxy resins as binder to produce sandpaper using hand spray method. the researchers recommended the manufacturing process for small scale industries. kishore also worked on the investigation of mechanical properties of crab shell. the results of the study showed that under tensile loading conditions, the whole crab shell exhibited a mode of fracture which does not include the delamination of lamellae common to the other arthropods [15]. it is of interest to further study some properties of periwinkle shells and crab shells and also to determine its usefulness and relevance in engineering usages, especially in production of abrasive material. therefore, the use of periwinkle and crab shells which are regarded as waste products were considered for production of abrasive sandpaper in this study. this will help to domesticate production of sandpaper in nigeria; assist in economic diversification of the nation through establishment and sustainability of small and medium scale enterprises (smse); and adequately proffer sustainable solution to the issue of unemployment among the nation’s youths; and economic down turn that may arise as results of covid-19 lockdown. 2 methodology 2.1 materials preparation the periwinkle and crabs were commercially obtained in a market at egbeda, lagos state, nigeria. the periwinkle and crabs shells (figures 1 a & b) were removed and washed in water to remove all traces of dirt on them. approximately 3.5 kg samples of shells were sun dried for 2 weeks and further oven dried till moisture content was fully removed. the dried samples were further charged into a local grinding machine where they were ground into powder. the powdery materials were then separately sieved (using astm e11 guidelines) with two sieve sizes of 250 μm (p60 abrasive grits) and 420 μm (p40 abrasive grits) [16-17]. other substances used in this study, which include cobalt naphthalene, methyl ethyl, ketone peroxide and polyester resin were classified and labelled for easy identification. figures 2 (a & b respectively) show the periwinkle shell grain sieved to size of 250 μm and 420 μm; while the samples of crab shell grain sieved to size of 250 μm and 420 μm are presented in figures 3 (a & b respectively). (a) periwinkle shells (b) crabs figures 1: samples of the periwinkle shells and crabs used in this study ambali et al. (2020): international journal of engineering materials and manufacture, 5(2), 55-61 57 table 1: grains/resin composite formulation in batches weight percentage composition (%) shell grains 96 94 92 polyester resin 3 5 7 accelerator 1 1 1 mekp catalyst 1 1 1 total composition 100 100 100 figure 2a: sample of periwinkle shell grains (250µm) figure 2b: sample of periwinkle shell grains (420µm) figure 3a: sample of crab shell grains (250µm) figure 3b: sample of crab shell grains (420µm) figure 4: some samples of the specimens periwinkle shell and crab shell of 118.0 g, 114.0 g and 111.6 g (in equal percentage, that is 50% each of the total grams) were measured using an electronic weighing balance (hx 302t with 0.01 g accuracy), which corresponds to 96.0 wt.%, 94.0 wt.%, and 92.0 wt.%. a measure of polyester resin in 5.4 g, 7.2 g and 9.6 g which corresponds to 3.0 wt. %, 5.0 wt. % and 7.0 wt. % was separately weighed out. to bring a balance of 100 wt. % in material composition, 1.2 g of catalyst and 1.2 g of accelerator were measured. the test samples were produced from each of the weight composition of resin by compressing the pastes to solid shapes in a metal mould of dimensions height 30 mm and diameter 52 mm using a hydraulic press (model p100t – capacity, serial no-38280). the samples were kept in a well-aerated environment for 21 days as practiced by ibrahim et al. [6]. some of the samples produced from the formulation are presented in figure 4, while table 1 shows the formulation used in production of sandpaper samples. production of abrasive sandpaper using periwinkle shells and crab shells 58 2.2 samples’ characterization the samples of the sandpapers produced were characterized through determination of some of the samples’ physical and mechanical properties, such as water absorption, wear rate, hardness and strength. 2.2.1 water absorption test the water absorption test was carried out by determining the weight of the sample (wo) using weighing machine and subsequently placed the sample in a contained containing water. it was re-weighed after 24 hours to obtain wi. for each sample, the percentage weight gained was calculated and recorded using the following relationship in equation 1 [18]. 2.2.2 hardness test the hardness value of the composite of different grain sizes was determined by the brinell hardness method using a testometric materials testing machine (type dbbmtcl-5000 kg, serial no. 17819) at national centre for agricultural mechanization universal testing machine (ncam utm) laboratory, ilorin, nigeria, based on astm e10-18 guidelines [19]. a 10mm steel ball indenter was pressed with the specimen at a test speed of 5mins using a force load of 50kg to a penetration depth. the brinell hardness number was calculated using equation 2. 2.2.3 compressive test the compressive strength test was carried out using the testometric materials testing machine (type dbbmtcl5000 kg, serial no. 17819) at national centre for agricultural mechanization universal testing machine (ncam utm) laboratory, ilorin, nigeria, based on astm standards c 617 guidelines [20]. 2.2.4 wear test the wear test was carried out at using europec bench grinder (md-250f). the grinding wheel was coated with an abrasive material and a load of 2kg was applied on each of the specimens for 2 minutes at 2950 rev/min. the differences in weight measured before and after tests give the wear of the samples. the formula (equation 3) used to convert the weight loss into wear rate as practiced by bashar et al. and edokpia et al., [21-22]: (%) 𝑤𝑒𝑖𝑔ℎ𝑡𝑔𝑎𝑖𝑛𝑒𝑑 = 𝑊𝑖−𝑊𝑜 𝑊𝑜 𝑥 100 % (1) bhn = 2f πd [d-√(d2 d2)] (kg/m 2 ) (2) 𝑊 = 𝑤𝑥−𝑤𝑦 𝑠 = ∆𝑤 𝑠 (3) where 𝑊𝑖 = weight after immersion and 𝑊𝑜 = weight before immersion, f = applied load in kg, d= diameter of indenter in mm, d= diameter of indentation in mm, wx is the weight before the test, wy is the weight after the test and s is the sliding distance. 3 results and discussions 3.1 water absorption test the results of the water absorption test are presented in figures 5. the results showed that the water absorption rate in the developed abrasive sandpaper samples increased as the sieve size increased from 250 µm to 420 µm in the formulation. the increase in water absorption rate must have been due to the poor interfacial bonding between binder and filler particle that caused increase in porosity. the highest water absorption value for the 250 µm particle size was 5.21% as against the 420 µm particle size which showed a highest value of absorption rate of 13.186%. the composites with low resin concentration are prone to water absorption due to poor interaction of grains surface area and the resin binder [22]. this shows better water absorption property than the produced abrasive sandpaper. from this result, 420 µm particle size of abrasive sandpaper shows better water absorption rate compared to 250 µm particle size. this result is in line with result obtained by obot et al. [23]. figure 5: the sandpaper samples’ water absorption values 0 5 10 15 92 94 96 w a te r a b so rp ti o n v a lu e (% ) weight percentage composition (wt %) 250µm 420µm ambali et al. (2020): international journal of engineering materials and manufacture, 5(2), 55-61 59 3.2 hardness test figure 6 shows the results of the brinell hardness test carried out on the samples made from 250µm and 420µm sieve sizes. the results indicated that there was an increment in the hardness value with increasing polyester resin concentration from 3 wt. % to 7 wt.%. the results for brinell hardness tests carried out on the abrasive samples showed that the hardness values increased proportionally as the percentage weight composition of the polyester resin increased from 3 to 7 wt. %. interfacial bonding of the polyester resin holding the periwinkle shell and crab shell grain particles together was responsible for the increase in hardness, and also contributes to the hardness of the parent composite material [ ]. the samples displayed the hardness increment across the sieve size with hardness values of 18437.263kg/m 2 and 21650.901kg/m 2 for 250 µm and 420 µm sieve sizes with 7 wt. % polyester resin respectively. in line with the findings of obot et al., the samples’ hardness increased with reducing particle sizes [24]. 3.3 wear test the results of the wear test carried out for 2 minutes per specimen with a fixed applied load of 2 kg are as presented in figure 7. it was observed from the results that the 250 μm grain sample has the least wear rate (1.67 m3/nm) with a resin content of 92 wt %. it was also observed that the wear rate decreased with increasing resin content which is due to an increase in hardness value and compressive strengths of the samples. the relationship between compressive strength, hardness and wear resistance with increased polyester resin content is in agreement with the assumptions of previous researchers [6, 25-27]. the decrease in wear rate with increased in the resin content may be also be attributed to the interfacial bonding between the resin and the grains. therefore, the wear properties of the agrowaste sandpaper can be improved by increasing the polyester resin content. from the results (figure 7), it can be proposed that the 250μm sample with 1.67 m3/nm wear rate is an alternative for the common sandpaper. figure 6: the specimens’ hardness values figure 7: the specimens’ wear rates 0 5000 10000 15000 20000 25000 3 5 7 b ri n e ll h a rd n e ss v a lu e ( k g /m 2 ) resin concentration (wt. %) 250µm 420µm 0 1 2 3 4 5 6 7 92 94 96 w e a r r a te ( m 3 /n m ) weight percentage composition (wt %) 250μm 420μm production of abrasive sandpaper using periwinkle shells and crab shells 60 3.4 compressive test the compressive strength test results in figure 8 shows the compressive strength across the sieve sizes. the 250 μm sieve size of the produced samples displayed the lowest compressive strength (1.650 n/mm² and 39.869 n/mm² for 3% and 7% resin composition respectively) while the other sieve size of 420 μm displayed compressive strength of 16.429 n/mm² and 45.477 n/mm² for 3 % and 7 % resin composition respectively. this may be due to the powder fineness inducing brittleness upon the composite as seen by the reduced strength with reducing sieve sizes. there was an increase in the compressive strength with increasing polyester resin concentration from 3 to 7 wt. %. the highest ultimate compressive strengths obtained was 45.477 n/mm²for 420μm particle size of shells with 7 wt. % polyester resin and 39.869 n/mm²was recorded for 250µm particle size with 5 wt.% polyester resin. figure 8: the specimens’ compressive strengths 4 conclusions from the results and discussion of the results, the following conclusions were drawn: 1. the properties of each of the samples varied as a result of the different mixing ratio of the grains composition and resin concentration. 2. calcium oxide largely dominated the composition of the periwinkle shell grains with concentration approximately 90%. under compressive stresses, the grains were liable to distortion and grain disorientation. 3. the periwinkle/polyester resin composite’s hardness and compressive strength increased gradually with increase in the resin’s concentration from 3 to 7 wt. %. meanwhile, with increased in the resin concentration and reduction in grains composition, the wear reduced. interfacial bonding between the combination of periwinkle grains and crab shells with polyester resin attributed to the improvement in the tested properties of the composite. 4. the composition from 92 wt.% and resin at 7 wt.%, and 1 wt.% for methyl ethyl ketone peroxide hardener and cobalt naphthalene each exhibited the most suitable abrasive properties (such as hardness, wear resistance and compressive strength) considered as the appropriate alternative material for abrasive sandpaper production. 5. the properties of the agro-waste sandpaper exhibited possible applications as abrasive grits with further improvement. 5 recommendations from the outcomes of this study, it is recommended that: 1. periwinkle shells and crabs shells can be used to convert waste to wealth. 2. since the performance evaluation of the produced abrasive paper was suitable for usage, the importation of sandpaper from other countries into nigeria can be greatly reduced by producing the abrasive locally using agricultural wastes. 3. further research works can be carried out to discover hitherto waste materials that could be recycle for meaningful purposes rather than disposing them off. 0 5 10 15 20 25 30 35 40 45 50 c o m p re ss iv e s tr e n g th (n /m m ²) resin concentration (wt %) 250µm 420µm ambali et al. (2020): international journal of engineering materials and manufacture, 5(2), 55-61 61 references 1. atia, m. r. and maksoud, t. m. a. (2004). review of intelligent grinding and dressing operations. journal of machining science and technology, 8, 263-276. 2. oyawale, f. a. and odior, a.o. (1998). manufacture of abrasive paper from locally sourced raw materials in nigeria. journal of emerging trends and applied sciences, 1(1), 40-47. 3. odior, a. o. and oyawale, f. a. (2010). manufacture of abrasive grains from locally sourced raw materials in nigeria, journal of emerging trends in engineering and applied sciences (jeteas), 1(1), 40-47 4. obot, m. u., yawas, d. s., aku, s. y., obada, d. o. (2016). an assessment on the production of abrasive sandpaper from locally sourced materials, tribology in industry, 38(2),176-185 5. aku, s., yawas, d., madakson, p., & amaren, s. (2012). characterisation of perinwinkeshell as asbestors-free brake pad materials.pacific journalof science and technology, 13(2), 57-63. 6. ibrahim h.k., abdulhamid, a.s., abdulkareem, s., shuaib-babata, y.l., popoola o.t., kareem, a.g., adeyi a. m., busari, o.y., ambali, i.o. (2019). development of abrasive sandpaper grains from agro-waste material for polishing of wood surface.adeleke university journal of engineering and technology, 48-60. 7. eckart, k., & aku, s. (2013). development of an abrasive material using periwinkle shells. journal of king saud university of engineering science, 5(3), 23-37. 8. scott, i. (2010). tribology of abrasive machining process. william andrew publishing, 268. 9. orji b., igbokwe, g. e., anagonye, c. o. (2017). chemical content of the periwinkle shell and its suitability in thin layer chromatography. international journal of chemistry studies, 09-11. 10. elegbede, i.o. and fashina-bombata, h.a (2013). proximate and mineral compositions of common crab species (callinectespallidus and cardisomaarmatum). journal of poultry, fisheries and wildlife sciences, 2, 1-5. 11. indah r., erna m., afdaliah y., muhammad, s. ad andi, i. l. (2015). synthesis and characterizations of calcium hydroxyapatite derived from crabs shells and its potency in safeguard against to dental demineralizations. internal journal of biomaterials, 1-8. 12. adewuyi, a.p and adegoke, t. (2008). exploratory study of periwinkle shell as coarse aggregate in concrete works.journal of science resources, 1678-1681. 13. malu, s.p and bassey, g.a (2003). periwinkle (t. fuscatus) shell as alternative source of lime for glass industry.global journal of pure and applied sciences, 491-494. 14. wai, j.j. and lily, m.t (2002). manufacturing of emery cloth from local raw materials. global journal of engineering research, 31-37. 15. kishore kumar gadgey, d. a. (2017). investigation of mechanical properties of crab shell: a review. international journal of latest trends in engineering and technology, 268-281. 16. astm e11-17, standard specification for woven wire test sieve cloth and test sieves, astm international, west conshohocken, pa, 2017, www.astm.org 17. fepa abrasives, 2013. p-grit sizes coated abrasive products. retrieved august 18, 2019 at 08:50 from <http://www.fepaabrasives.com/> 18. aigbodion, v. s., akadike, u., agunsoye, j. o. (2011). development of asbestos-free brake pad using bagasse. tribology in industry, 32. 12-18. 19. astm e10-18 – standard test method for brinell hardness of metallic materials, astm international, west conshohocken, pa, 2018, www.astm.org. 20. astm c617 / c617m-15, standard practice for capping cylindrical concrete specimens, astm international, west conshohocken, pa, 2015, www.astm.org 21. bashar, t., da asabe, g., peter, k., madakson, b., joseph, f., &manji, k. (2012). material selection and production of a cold worked composite brake pad. world journal of engineering, 2(3), 96. 22. edokpia, r., aigbodion, v., obiorah, o., & atuanya, c. (2014). evaluation of the properties of eco friendlybrakepad using egg shell particles. e. r. producer, & gum arabic science direct. 23. obot, m.u, aku, s. y,yawas d. s., obada, d.o (2017). an assessment on the production of abrasive sandpaper from locally sourced materials. journal of king saud university – engineering sciences, 284-288. 24. obot, m., yawas, d., & aku, s. (2015). development of abrasive using periwinke shells. journal of king saud university of engineering sciences. 1-5. 25. marinescu, i.d., rowe, w.b., dimitrow, b., inasaki, i., (2004). tribology of abrasive machining process, first ed. william andrew publishing, 268. 26. aigbodion, v., akadike, u., hassan, s., & asuke, f. a. (2010). development of asbestors free brake pad using bagasse. tribology in industry, 32(1), 12-17. 27. yawas, d., aku, s., &amaren, s. (2013). morphorlogy and properties of periwinkle shells asbestors-free brakepad.journal of king saud university of engineering and technology. 32(1), international journal of engineering materials and manufacture (2018) 3(4) 190-199 https://doi.org/10.26776/ijemm.03.04.2018.03 s. e. m. f. alazemi1 , i. hilmy2 and e. y. t. adesta3 department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia 1e-mail: good-lucj78@hotmail.com 2e-mail: ihilmy@iium.edu.my 3e-mail: eadesta@iium.edu.my reference: alazemi, e. m. f. s., hilmy, i. and adesta, e. y. t. (2018). indentation mechanism in rotary hammer forging process: analytical and numerical approach. international journal of engineering materials and manufacture, 3(4), 190-199. indentation mechanism in rotary hammer forging process: analytical and numerical approach saud f. e. m. d. alazemi, irfan hilmy and erry y. t. adesta received: 01 september 2018 accepted: 13 september 2018 published: 01 december 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract rotary hammer forging process is getting popular since it has many advantages comparing to the conventional forging process. the mechanism of the movement in term of orbital motion of the conical upper die become concern of this research. this article present the three stages of the modelling of the rotary hammer forging. the first stage is the development of the orbital motion of the conical upper die. three-dimensional cad model of the conical upper die was developed to determine the orbital motion as a function of the four parameters: nutation, precession, spin and rocking-die mechanism. a reasonably accurate design of the conical upper die and the workpiece had been developed based on motion because of interaction of conical upper die and upper part of workpiece geometries. the behaviour of orbital motion with any active combination of those four parameters was observed. the second stage was the development of the conical upper die with the specific feature in order to generate a product with an unsymmetrical shape of upper part of the product. the sequence and mechanism of the formation of the upper part of product were generated. the third stage was the analysis of the stress strain state during the formation of the upper part of the workpiece. an elastic-plastic, dynamic analysis of 3d rotary hammer forging mechanism with the concern at the workpiece and their interaction with a model of dies have been performed. verification of the indentation mechanism of the rotary hammer forging had been done by validating the result with the existing experimental results. keywords: forging, rotary hammer forging, indentation mechanism, conical upper die, orbital motion 1 introduction rotary hammer forging is one type of forging process which is also called as wobble die forging. parts that have circular feature such as bearing housing, gears, chain sprocket, coupling and clutch hubs are produced by this process. those parts can be found mostly in the automotive industry. it was realized that nearly 85% of all forged parts have a circular shape. in the era of extreme global competition, improvement toward an efficient process will enhance the forging quality and lead to the cost reduction and greater productivity. however, designing new forging process for a more complicated shape of an object is challenging. in addition, to be competitive, the processes are to be faster and accurate method on designing forging mechanism as well as the dies [1, 2, 3]. in this quite competitive era in the business, product life cycle should be shorter to be competitive. as such a faster design for metal forging process is necessary. hence, the research questions are: 1. is there any standard guideline to design the conical upper die of a rotary hammer forging? 2. how to generate the motion of conical upper die based on a set of parameter? 3. how to select suitable workpiece material for dies in the rotary hammer forging? 4. which friction model is suitable in modelling interaction between workpiece and upper conical and lower die? the objective of this research is to develop a new method as a framework to design forging process as well as die design in a rotary hammer forging. the research objective can be broken-down into three specific objectives which are as follows: indentation mechanism in rotary hammer forging process: analytical and numerical approach 191 1. to develop the analytical analysis on orbital motion of the conical upper die of a rotary hammer forging process in order to identify the behaviour under different configuration of forging parameters, 2. to design the conical upper die with a specific feature and specific forging configuration, and 3. to develop a numerical stress analysis based on finite element model of the indentation process of the conical upper die to the upper region of the workpiece. 1.1 research methodology and hypothesis the first stage of the research is the development of the analytical model. at this stage, an integration of solidworks with the add-on motion feature and matlab script has been utilized. the cad (computer aided design) model of the conical upper die as well as the workpiece has been developed. one point of interest has been identified and marked. using euler law of motion, the orbital motion equation has been derived analytically involving parameters of orbital motion: nutation, precession, spin and the rocking-die mechanism. the second stage is the development of the additional feature at the upper conical die in order to generate workpiece with more intricate shape. the model was developed using solidworks software. the developed model refers to the existing upper conical die shape. the scenario of the indentation process by combining the orbital motion at different setting of parameters of the upper conical die developed in the previous stage has been generated. the third stage is the stress analysis of the indentation process. the cad model of the interaction of upper conical die and the workpiece was transferred to the afdex environment in order to perform a numerical, finite element based analysis of the rotary forging process. the research hypotheses on guidelines to the development of analytical and numerical model of the rotary hammer forging are as follows: 1. there is no unique way for the formation of profile indented to the upper part of workpiece. different combination of the hammer forging parameters may offer alternate solutions. 2. friction condition at the interfacial contact between the conical upper die and the workpiece will affect the process of the indentation. 3. assumption of the conical upper dies as a rigid body object is reasonable this study will contribute to the research and development in the forging industry sector. shortening the plc (product life cycle) of a forging product becomes a compulsory requirement in the era of high and critical competition in any sectors especially in the manufacturing field. the proposed method my speed up the design stage in a relatively significant amount of time. 2 literature review based on report from the association of forging industry [4], they record the increase of the forging product with the increase around 25% every year. the leading industry still the automotive sector with around 30% of total forging product have been fabricated. forging processes are widely utilized mostly in the automotive and aircraft manufacturing company. more than 200 forged parts could be identified in a typical large car such as truck. the parts suffer large plastic deformation due to sudden impact load or a slow pressing load. figure 2.1 shows some of the products fabricated using forging process. in the aerospace industries, around 400 forged part for structural components only and another 200 for the engine component. apart from those to fields, other industries such as oil and gas sector, food processor, agricultural and electronics also used many forged part components. 2.1 classification of forging processes forging process can be grouped into two major categories: open die forging and closed die forging. open die forging was the first and can be considered ancient method of forging. blacksmith was one of the oldest technique of the open die forging. fabricating of the horseshoe, dagger, sword etc. utilize this type of forging. the power at that time only utilized human power. therefore, the product can be considered small. open die forging can be characterized by having an open space between dies and workpiece since no sidewall block the flow of the material during its process [5]. this condition will allow the material of workpiece to flow in the free space. figure 1 shows the very basic of forging configuration: open die forging. because of this configuration, the benefit of the open die forging is it can forge the large size of workpiece. workpiece with weight can reach up to 100 tons can be forged with this open die configuration. however, in case of close dies, the shape of the die is negative of the product. if the forging is performed, the workpiece will flow and occupy the negative shape space. this type of forging will produce a quite complex final product with tighter tolerance comparing to the open die forging. nowadays, this type of forging process plays a dominant role in the forging industry. figure 2 shows the schematic of the closed die forging. based on the working temperature, forging can be grouped as cold forging and hot forging. it called cold forging if the process is performed at a room temperature. lubricant is necessary since during cold temperature process, the friction play a significant role to the process. the result of cold forging is usually a finished product with a precise result. the disadvantage is the material does not become soft since no change in the grain structure. alazemi, hilmy and adesta (2018): international journal of engineering materials and manufacture, 3(4), 190-199 192 figure 1: open die forging (a) initial condition, (b) and (c) forging process [5] figure 2: closed die or impression die-forging from starting point until finish [5] table 1: temperature range for various process [5] process ratio of processing temperature and meting point (tp/tm) cold working < 0.3 warm working 0.3-0.5 hot working >0.5 meanwhile, hot forging is performed above the softening temperature where the strain hardening is released during this stage the grain transform from a uniaxial shape become spherical shape. this condition will make the material flow easier and the forging force become lower. the workpiece usually large and bulk in shape and this hot forging process usually for the semi-finished product that need to be processed further. the disadvantage of this process is the oxidation at the surface during cooling process. this process is required to be processed in a faster way to avoid an excessive oxidation. as a guideline, for any metal workpiece, the range of the working temperature is shown in the table 1. the range is displayed as a ratio over the melting temperature tm. in term of the type of power that pushes the forged material, there are two main group of forging machine: hammer or drop forging and press forging. hammer forging work by hammering the workpiece with an instant impact. one of the method is utilizing the gravity hence the name is drop forging. the load is so sudden which act as an impact load. this process consequently is became faster but with the disadvantage that this mechanism is only applicable for a relatively smaller workpiece due to the limitation in the forging force. press forging in the other side is using hydraulic press mechanism. the process is slower than hammer forging but in term of power capability multiple times higher than hammering. it can forge a large and bulk workpiece. in conclusion, depend on the requirement, both have advantages and disadvantages. for a demand of a large quantity product, time is very crucial. only hammering can fulfil the criteria of an economically process. 2.2 characteristic of rotary forging rotary forging was originated in japan. japan has been extensively developed research about rotary forging in almost every aspect. they investigated the performance of the machine, characteristic of stress strain behaviour, the accuracy of the forging process [6], the behaviour of the surface interaction between dies and workpiece. the research was backed up by the private sector as well as the support from the government. as the leader, japan utilize this forging method in almost every sector of metal industry and give a significant contribution to their economy. cold rotary forging can be defined as an advanced and very complex forging technique involving a plastic deformation occurred locally. it has gain more popularity to produce many application in multi sector of industry covering machining equipment, automotive, electrical part and other hardware accessories. it has advantages including very low level of vibration as well as noise, adequate roughness and surface tolerance and relatively low cost and energy requirement. the coverage of the products or components that can be fabricated using rotary forging including flange, hub, cam, gear as well as the flat shape and thin disks. the shape of those parts can be grouped as an axisymmetric part. rotary forging with normal orbital motion of die is suitable to forge them. if complex and indentation mechanism in rotary hammer forging process: analytical and numerical approach 193 axisymmetric component need to be fabricated, then the second type of rotary forging which is the rocking-die motion is applicable. the example of the products is bevel gear, differential gear and t-flanges. rotary forging is more suitable for the specimen, which have a high value of diameter over thickness ratio [7]. the reason is that workpiece with the large flange dimension more suitable to suffer rotary forging load. only smaller axial force is needed if the high ratio of diameter over thickness is fulfilled. another positive impact in the minimal quantity of friction occurs. this is because the shorter contact time between material or workpiece and their dies. the deformation is 30% more than the common forging process. 2.3 mechanism of rotary forging figure 3 shows the mechanism of rotary forging machine. it has lower dies, which rotates continuously, and an upper dies with a conical shape that also rotates with a small inclination angle during its process. at particular time only small part of the workpiece receive the pressing load. the mechanism is called cyclic local pressure or compression. it is contrast with the common forging process which the workpiece received instant blow at the contact surface. therefore, using this method, the force required to perform the forging process is lower than the common forging process. in the rotary forging process, the upper die oscillate rotating the vertical axis of the machine at a constant speed. at the same time, the workpiece is also being pushed by lower die upward direction. this mechanism is repeated simultaneously until it makes a result a perfect plastic deformation in an axisymmetric manner. the numbered component is called part. for example, part 1 and part 2 refer to the component number 1 and 2 respectively. part 1 is the upper holder, which has a conical shape geometry that will contact directly with the workpiece. part 1 is supported by part 2, which has hemispherical head. it will allow part 1 to move in a rocker-die mechanism. part 23 is the main motor, which give power to all movement mechanism. the part 3 is an upper plate, which act to secure the placement of part 2. part 25 is the gearbox system that connected to the motor via the coupling system as indicated as part 24. part 25 reduces the output angular speed of the motor. part 25 also act as axis changer that convert the horizontal axis of rotation become a vertical axis of rotation. figure 3: concept of rotary forging 2.4 orbital motion in rotary forging development of the orbital motion of the conical upper die requires four independent parameters: nutation (n) angle or rotation, precession (p) angle or rotation, spin (s) angle or rotation and the rocking die mechanism in –z direction. figure 4 shows the angle and axis conventions. it is a rotation along x-axis. all the existing rotary forging machines use one or some of the combination of n, p and s parameters. it can be seen that not all of the machines utilized all three angle of rotations parameters [8]. the difference between rotary press and hammer forging is in the speed of loading or indentation. press forging is slower than hammer forging. in rotary hammer forging, the process of the die approaching the workpiece is in order of millisecond. the advantage of this rapid process is the process reduces the heat loss of the surface. the benefit is the improvement of the mechanical properties of the workpiece. 2.5 benefit of forging simulation the benefit of the finite element modelling in metal forming in general and specifically forging are as follows [9]. (1) the behaviour of the workpiece due to the heat treatment process could be predicted, (2) the stress-strain state during the forging process can be obtained, (3) the occurrence of failure in term of location as well as magnitude can be anticipated, (4) the die can be designed to include the wear and their respective lifetime in the considerations, (5) reduce or even eliminate the trial and error in the product life cycle. alazemi, hilmy and adesta (2018): international journal of engineering materials and manufacture, 3(4), 190-199 194 figure 4: three angular movements: (a) nutation, (b) precession and (c) spin in the forging field, it is common that development of the product involving simulation application. there are two types of the finite element based software available in the market. the commercial software and the specific tailor made software that have been developed specifically for the needs of the particular company. simulation can be divided into two activities. simulation of the workpiece and the dies. for each type of analysis, sometime the assumptions have been made whether to treat the dies as a rigid body or non-rigid body [10]. if the main concern is on the workpiece, the dies are considered rigid. using this way, computational time can be reduced quite significant. die configuration is grouped into two possible rigid and elastic. if die is considered as a rigid body, then no analysis is given to the die. in this case, die is not become a concern because for example the workpiece is relatively soft. if the workpiece is from a softer family of metal, then die deformation can be considered too small or not significant. the rest of the combinations treat the die material as an elastic body. assumption has been made that the flow stress is an independent strain rate. for strain rate dependent, the flow stress curve will vary as function of the working temperature or the different speed of strain. forging simulation getting popular due to some benefit. three domain in the forging development consist of (1) cost down, (2) technological improvement and (3) reduced lead times for development. using finite element, various ideas can be explored through different model and design. 3 finite element modeling in afdex development a simulation of metal forming in afdex is grouped into two categories. the first one is the modelling of the behaviour of the workpiece during their forming sequence. in analysis, focus is on the workpiece and usually it is a coupled analysis between flow analysis of workpiece and heat transfer analysis of workpiece. the coupled analysis also can be between the die structural analysis and the workpiece. the input and output parameters cover: (1) heat generation, (2) flow stress change, (3) mechanical load, (4) die geometry change, (5) heat transfer and (6) thermal load. afdex separate the analysis in the sub module. the separation of module is one way to reduce or optimize the resources in term of memory and disk space. only the requested modules will be loaded to the memory. once particular module has done with their work, they will be immediately unloaded from the memory. afdex provide basic geometry modelling feature such as importing the primitive shapes. basic geometry such as cube, cylinder and hollow cylinder and sphere are available to be used as the basic shape. 3.1 meshing technique meshing is one important factor in the finite element analysis. it is a method how a continuum workpiece is being discretized into small elements. a real product can be modelled as one dimensional (1d), two-dimensional (2d) or three-dimensional (3d) element. the choice to determine the level of density of the meshing depends of some issues. in term of hardware requirement to be used as the computing machine, finer the mesh of the structure, the heavier load of the computing machine will be. sometime, the refinement of the element size into half of the original, the computing time will increase exponentially. enlarging the size of the meshing, the computing time can be reduced significantly. the disadvantages of a coarse meshing are missing some results at some locations and the geometry of the product is less accurate. some intricate shape needs extra attention by giving a finer meshing. narrow gap or sharp object requires a finer mesh. otherwise, some important and significant gradient of the result might be missing. to compromise between coarse and fine element meshing, the localized fine meshing is the solution. instead of indentation mechanism in rotary hammer forging process: analytical and numerical approach 195 making a homogeneous meshing, fine meshing is applied only at particular location or point of interest. afdex provide the feature for user to do localized meshing. some techniques are available based on the shape of the enclosed region. 3.2 afdex material library afdex provide a large collection of the material library with the properties detail. one main important curve is the material flow stress. figure 5 shows the example of flow stress of a scm440 alloy steel. since this material is a strain rate dependent, the flow stresses are different at different level of working temperature. it can be seen that the higher working temperature, the lower flow stress occurred since the material getting softer. thus, it is easier to pull the material at the higher level of working temperature. the flow stress also can be generated by choosing the suitable flow stress model as shown in the table 4.3. started from the least complex flow stress equation to the relatively complex flow stress equation which incorporating the damage parameters. figure 5: flow stress of scm440 alloy steel in the afdex library 3.3 afdex friction model implementing a friction model in the forging simulation requires assumption on how the behaviour of the friction. there are two ways of how to enter friction condition inside afdex. use the available model in the afdex library. for advance user, or if the model need to be customized, the friction can be entered in the manual model. the user have to select the friction model and the related contant parameter. there are two ways to enter the maximum allowable penetration limit. firstly, using the auto generation feature, afdex calculates the proper value. another feature is touch limit. a minimum gap when the contact between dies and workpiece can be considered occur (han. et al., 2013). 3.4 afdex dies movement and forming control the forming process can be performed by configuring the movement of the dies. it is a combination of movement between upper and lower dies. in afdex, the motion control can be configured as a force vs. distance or force vs. time. one of the differences between press forging and hammer forging simulation is the time or distance setting. press forging can be configured by set the force vs. time slower and vice versa for the rotary forging. another configuration setup that governs the dies movement is the machine configuration. after finishing all the modelling stage, the last required step is the forming control. it is about configuring the computing process. the behaviour of the analysis and how computer perform the computation and iteration will be governed from this setting. to determine how deep the die penetrates the workpiece is by pointing one point at the die’s corner and another point at workpiece’s corner. afdex will measure the distance between those points and set it as the distance of die’s movement. alazemi, hilmy and adesta (2018): international journal of engineering materials and manufacture, 3(4), 190-199 196 4 orbital motion analysis identifying the orbital motion of conical die is important during the design stage. the plot of orbital is generated using the plot3 function available in matlab. there are four parameters involve in this orbital motion plot: the nutation angle (n), the precession (p), the spin (n) and the rocking die mechanism as it represented by the cyclic translation movement in –y axis. figure 6 shows the setup for the orbital motion analysis. the cylindrical geometry at the base is representing the workpiece. the conical shape with the longer cylindrical part is representing the conical upper die and the rocker arm. location of interest is marked as point pt1. the following orbital plots as shown in the next figures are based on this point pt1. 4.1 orbital motion of the rotary press forging the first orbital motion of the conical upper die is shown in the figure 7. for example, the “n5+=-30oc1pc1sc1” can be breakdown into nutation part “n5+=-30oc1” means that the nutation (n) angle is 5o with the amplitude 30o. therefore, the nutation angle will be varied from -25o to 35owith the frequency one cycle as stated with the code “c1”. it is considered a slow nutation mechanism. the next code is “pc1” which is representing the precession angle. it is a fully cycle from 0o to 360o. the last code is sc1 which is representing the spin angle with a fully one rotation cycle. figure 6: the geometrical setup of orbital motion analysis figure 7: orbital plot of point pt1 with n (nutation angle) = 5o±30o with p (precession) and s (spin) are rotated simultaneously indentation mechanism in rotary hammer forging process: analytical and numerical approach 197 figure 8: orbital plot of point pt1with r (rocking-die) at 10 mm amplitude, n (nutation angle) rotates at 5o±30o, p and s are rotating simultaneously 4.2 orbital motion of the rotary hammer forging the difference between rotary press forging and rotary hammer forging can be seen by the additional parameters that vary during the forging process. there is an additional vertical movement along –y-axis that represent the rocking-die mechanism. followings are the result of orbital motion plot with the additional code r in the first digit of name coding. the additional letter of r code can be found in the first three digits of the coding name as shown in the first orbital motion of the conical upper die as shown in figure 8. the label “rc1” means that (1) the orbital motion is belong to the rotary hammer forging and (2) the vertical axis (y) is moving in a periodic manner. figure 8 shows the orbital motion with the configuration is as follow: rocking die mechanism with stroke 10 mm, and nutation angle rotates between -25o-35o angle while p and s are rotating simultaneously. figure 9 shows the orbital motion with the configuration is as follow: rocking die mechanism with stroke 10 mm, and nutation angle rotates between -25o-35o angle while p is stationary and s is rotating simultaneously. figure 9: orbital plot of point pt1with r (rocking-die) at 10 mm amplitude, n (nutation angle) rotates at 5o±30o, s rotates and p is stationary. alazemi, hilmy and adesta (2018): international journal of engineering materials and manufacture, 3(4), 190-199 198 figure 10: boundary condition of the rotary hammer forging 5 analysis on indentation mechanism the definition of the indentation mechanism is the mechanism that shows how the conical upper die penetrate and deform the upper part of the workpiece under particular rotary hammer forging motion. in this chapter, the mechanism as well as the contour of the pressure state was investigated and discussed. 5.1 cad design and meshing the cad design of upper conical die and the workpiece with small cylinder feature were developed using solidworks application. the conical angle of the upper conical die is 15o. the small feature is a extruded cylinder with the diameter 5 mm and 2 mm depth. the purpose of this small feature is to give indentation to the workpiece. the outer diameter of upper conical die as well as the model of workpiece is 50 mm length. the thickness of the workpiece is 10 mm. for the workpiece, since it will suffer elastic-plastic deformation, the meshing size becomes concern. later on, after every step or iteration during analysis, the meshing will be updated. afdex was set to read the last result of deformation become the initial element for the next result. 5.2 determining the boundary condition the next stage, which is the determination of the boundary condition, becomes the crucial stage. a set of boundary condition will govern the result and the behaviour of the system. in fact, it is the most difficult stage in the finite element analysis. it is different with the geometry or profile of the product. nowadays, with many available and sophisticated cad software, it is easy to follow and model any shape or geometry of a product. no matter how complex or intricate any shape of object, with a higher degree of curve equation, it is not a problem anymore. wrongly adjust the boundary condition; the behaviour will be far from the real condition. figure 10 shows the boundary condition being applied to the rotary hammer forging system. some assumptions have been made as a reason to decide such the boundary condition. firstly, the analysis only concern at the upper part of the workpiece. the lower part of the workpiece was considered rigid. therefore, the fixed boundary condition was applied at the bottom surface of the workpiece. three axes labelled with n for nutation, s for spin and p for precession were defined. two arrow pointers showing the vector direction of the rotation. the behaviour of the n, s, p and-y (rocking die mechanism) depends on the configuration of those parameters. this model then was integrating the orbital motion result. the analysis uses the orbital motion of the conical upper die. in order to increase the frequency of indentation, the frequency of nutation angle have to be quadrupled the initial speed. with the completion of all the modelling stages, the finite element system was ready to be analysed. it can be observed seen that the indentation result showing an exact location with the angle between holes is 90o. 6 conclusions from this research, some conclusions can be summarized as follows: 1. comparing to other conventional forging process, rotary forging has many advance features that can overcome the limitations of their predecessor. the future of the rotary forging process is promising. indentation mechanism in rotary hammer forging process: analytical and numerical approach 199 2. the flow stress and deformation of the workpiece in rotary forging is not uniform. the non-homogeneity of both parameters is getting more significant in a more complex shape of workpiece as well as dies. these issues should be considered when designing the workpiece, dies as well as the process. 3. the force required to perform the rotary forging is lower than the conventional forging. therefore, the process will reduce the energy consumption. 4. since the contact region between workpiece and upper die is smaller than the contact area of the conventional forging, the lifetime of the dies are longer for rotational forging. 5. the relation between rotary forging parameters such as nutation, spin and precession govern the indentation mechanism on the rotary forging have been comprehensively investigated by modelling a three dimensional elastic-dynamic plasticity under afdex environment. 6. from the simulation, the indentation pattern behaviour on the process of the rotary forging can be revealed. it will produce a guideline during design, assembly and installation stage and set of knowledge about how the flow of material performs during forging process. 7. the inclination angle and the angular speed of the upper die play a significant role on the flow of material and deformation homogeneity in the workpiece. maximum forging force in axial direction can be achieved by the smaller inclination angle of the upper die. 8. rising the angular rotating speed of lower die and reducing the angle of inclination improve the flow of the material in the workpiece. 7 recommendation since the prospect of the development of rotary hammer forging is still wide open. some suggestions and recommendations for the future works are as follows: 1. the possibility to develop a specific and tailor made cad and cae software to automate the work of generating the pattern so more user with less technical background can utilize the tools 2. development of a new machine with new kinematic mechanism that can allow utilizing all rotary forging parameters. the new system will allow to generate any kind of pattern by adjusting, activating or deactivating some of the rotary forging parameters. acknowledgement the authors would like to appreciate very much the experimental and analytical support from department of manufacturing and materials engineering in doing this research. references 1. han x. & hua l. (2009). comparison between cold rotary forging and conventional forging. journal of mechanical science and technology, 23, 2668-2678. 2. han, x. h. & hua, l. (2013). 3d fe modelling of contact pressure response in cold rotary forging. tribology international, 57(1), 115–123. 3. han, x. h., hua, l., zhuang, w. h. & zhang, x. c. (2014). process design and control in cold rotary forging of non-rotary gear parts. journal of materials processing technology, 214(11), 2402–2416. 4. yongning, m. m. s. (2009). forging process design for risk reduction. phd theses, the ohio state university. 5. biglari, f. r., o'dowd, n. p. & fenner, r. t. (1998). optimum design of forging dies using fuzzy logic in conjunction with the backward deformation method. international journal of machine tools and manufacture, 38(8), 981-1000. 6. malhotra, r., cao, j., & ren, f. (2011). improvement of geometric accuracy in incremental forming by using a squeezing toolpath strategy with two forming tools. asme journal of manufacturing science and engineering, 133(6), 061019. 7. zhang, y. q., shan, d. b., xu, w. c. & lv, y. (2010). study on spinning process of a thin-walled aluminum alloy vessel head with small ratio of thickness to diameter. asme journal of manufacturing science and engineering, 132(1), 014504. 8. merklein, m., plettke, r. & opel, s. (2012). orbital forming of tailored blanks from sheet metal. cirp annals: manufacturing technology, 61, 263-266. 9. lin h.-r. & wang y.-h. (2005). fem simulation for swing die method. journal of jiangxi nonferrous metals. (9), 40-42. 10. morakabati, m., aboutalebi, m., kheirandish, sh., karimi taheri, a., and abbasi, s. m. (2011). high temperature deformation and processing map of a niti intermetallic alloy. intermetallics 19, 1399–1404. international journal of engineering materials and manufacture (2020) 5(4) 130-147 https://doi.org/10.26776/ijemm.05.04.2020.03 md. shamim ahmed and mohammad zoynal abedin department of mechanical engineering dhaka university of engineering and technology gazipur 1700, bangladesh e-mail: abedin.mzoynal@duet.ac.bd reference: ahmed, m. s. and abedin, m. z. (2020). review on heat transfer enhancement by insert devices. international journal of engineering materials and manufacture, 5(4), 130-147. review on heat transfer enhancement by insert devices md. shamim ahmed and mohammad zoynal abedin received: 24 july 2020 accepted: 05 october 2020 published: 20 october 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 abstract the scientists revise the heat transfer enhancement techniques time to time to achieve better performance and to obtain optimized designs of heat exchangers. the present study reviews the performance and techniques of heat transfer enhancement using various insert devices such as twisted tape and wire coil insert as well as completely different forms of other inserts like air-foil shape inserts, x-shaped twisted tape inserts, baffles and v-winglets inserts with various types of medium and nanofluids. according to the summary of recent significant researches on the heat transfer enhancement by using different types of inserts and combinations of these inserts with various nanofluids showed that insert can indicatively enhance the heat transfer rate by modifying its geometry or configurations like twist ratio, length ratio, pitch ratio, segmented tape, perforated tape, angle of arrangements and insert quantities and so on which caused a considerable impact on performance characteristics of heat transfer enhancement along with the pressure drop and friction factor. it is revealed through reviewing the related literature that the highest value of equivalence heat transfer enhancement is as maximum as 400%, 300% and 9% for the twisted tape insert with helical tube, the air foil shaped inserts and for the wire coil inserts, respectively when compared with the smooth tube. in the case of baffles in nanofluids, as maximum as 255% equivalence heat transfer enhancement could be achieved when compared with that of baffles without nanofluids. keywords: heat transfer enhancement, performance characteristics, twisted tape inserts, wire coil inserts, inserts with nanofluids. nomenclature: abbreviation/symbol meaning tt twisted tape htc heat transfer coefficients g mass flux q heat flux pttt perforated triple twisted tape insert tee thermal enhancement efficiency pr prandtl number re reynolds number fltt full length twisted tape hlutt half-length upstream twisted tape hldtt half-length-downstream twisted tape t-w delta-wing tape inserts p/w wing pitch ratio r b relative winglet height rp relative winglet pitch dw discrete-v winglet tape hte heat transfer enhancement htp heat transfer performance htr heat transfer rate ef efficiency factor mailto:abedin.mzoynal@duet.ac.bd ahmed and abedin (2020): international journal of engineering materials and manufacture, 5(4), 130-147 131 1 introduction the researchers investigate different ways of heat transfer enhancement techniques for reducing the cost and size of heat exchanger for many years. three main categories (active, passive and compound methods) are considered as enhancement techniques to increase heat transfer efficiency. the active method utilizes external power to achieve the desired goal and rarely use in practical applications whereas the passive method does not require external power to achieve the fluid motion and heat transfer enhancement. on the contrary, the compound method is the combination of two or more methods that have limited applications due to its complex design despite it is considered as a significant enhancer. for convenient usage, passive techniques are important topics for scientists and researchers during recent decades. innumerable experimental studies have been conducted to improve the heat transfer rates by these techniques. scientists preferred passive heat transfer enhancement techniques due to their simplicity and applicability in many applications [1]. in recent years, heat transfer technology has been widely applied to refrigeration and air conditioning, automobile, process industries, etc. the main purpose of heat transfer enhancement techniques is to reduce the thermal resistance either by achieving the effective heat transfer surface area or by creating turbulence in the fluid flowing inside the tube. there are various arrangements are used and experimented to get better heat transfer rate such as insertion in tubes, the tube with fins, different tube shapes, corrugated tubes, baffle arrangements as well as different mediums like water, air, and nanofluids. the rearrangements of these different components are used for obtaining various purposes like increases the surface contact area of the fluid, create a swirl in the flow, and decrease the pressure drop to get enhancement heat transfer rates [2]. overall, rough surfaces or extended surfaces are used to increasing the effective surface area whereas inserts, winglets, turbulators, etc. are used for generating the turbulence [3]. based on scientific experiences, various types of inserts such as modified twisted tapes, wire coil, baffles, wire mesh, longitudinal swirl generators, and other types of tube inserts have been designed and studied numerically or experimentally. some researchers summarized the functions of different types of the insert which mainly enhanced single-phase convective heat transfer in heat exchangers by mixing main flow and the turbulence in the boundary layer region [4]. in recent years, heat transfer technology has been widely applied to devise applications in refrigeration, automotive, method industries as heat exchanger system. heat exchanger systems are used in different processes like conversion, utilization and recovery of thermal energy in various industrial, domestic applications and commercial processes. the most common examples include steam generation and condensation in power cogeneration plants widely used the heat exchanger to get better performance. the heating and cooling in thermal processing of pharmaceutical products manufacturing, chemicals industries and waste heat recovery plants are also utilizing the heat enhancement process by various enhancer to increase the heat exchanger efficiency. the increase in heat transfer performance can lead to a more economical design of heat exchanger which can help to make savings of energy, materials and cost which is related to a heat exchange process. this design also obeys many techniques termed as heat transfer augmentation which has an indicative impact on the enhancement of thermal performance. the present study investigated the heat transfer enhancement in various arrangements with insert devices as an important passive technique and their impacts on different mediums and configurations. 2 insert devices as part of heat transfer enhancement, inserts are widely used in pipe flow because it can break the boundary layer and increase the heat transfer rates. inserts require additional arrangements to create turbulence of fluids or mediums which can enhance the heat transfer. there are several types of inserts using for heat transfer enhancement. for instance, twisted tape, wire coils, ribs, baffles, plates, helical screw insert, mesh inserts, convergent or divergent conical rings, conical rings, etc. which are major types of the insert. tube insert devices including twisted tape, wire coils, extended surfaces, and wire mesh inserts are considered as the most important techniques of passive heat transfer enhancement methods. among them, twisted tape and wire coil inserts are widely applied to others. this paper tried to reveal only the very recent significant study on twisted tape (tt) and wire coils inserts [5]. 3 twisted tape inserts twisted tapes are the metallic twisted strips using some of the suitable techniques as per the required shape and dimension, which are inserted in the flow to enhance the heat transfer [6]. to enhance the thermal efficiency of heat exchangers, scientists found that different types of developed twisted tape inserts are suitable as passive augmentation techniques and strengthen the heat transfer efficiency for heat exchangers [7]. among the swirl flow devices, twisted tape inserts are very popular because of their better thermal performance in flow mediums like single-phase flow, two-phase flow, boiling, condensation, etc. generally, twisted tape inserts increase the heat transfer enhancement with an increase in the pressure drop [8]. this enhancement of heat transfer techniques for a twisted tape is achieved by a mixing of the boundary layer rather than an increase in heat transfer surface area. figure 1 shows a typical configuration of plain tt which is commonly used [9]. the very recent study of feng et al., [10] proved that the convective heat transfer in a swirl flow is similar to that in a straight flow. the investigation also found that the tubes with tt inserts show an enhanced heat transfer coefficient compared to the wall temperature of plain tubes and tt tubes by experiment the effects of thermal performance characteristics like the system pressure, heat flux, buoyancy, thermal acceleration and twist ratio with a review on heat transfer enhancement by insert devices 132 wide range of supercritical conditions for a kerosene-type hydrocarbon fuel with a twisted tape insert [10]. figure 2(a) shows the heat flux and the average htc variation for the plain and tt tubes at a pressure of 3.0 mpa. and it shows that the average htc for the tt tubes is larger than that for the plain tubes. in another figure 2(b) shows the overall heat transfer performance for the tt tube with different twist ratios is larger than the plain tube. the effects of porosity of perforated triple twisted tapes (pttt) on heat transfer enhancement and friction factor as an important thermal performance characteristic of a heat exchanger has been studied and found that the highest heat transfer of 320%, the highest friction factor of 355% and maximum thermal enhancement efficiency (tee) of 1.5 is obtained at a porosity of 4.6% with pttt insert compared to the smooth tube. because with decreasing the porosity of the tape inserts the nusselt number, friction factor, and tee are increased. the predicted vs. experimental relationships of heat transfer, friction factor and tee are shown in figure 3(a), figure 3(b), and figure 3(c). it has been observed that the predicted data are well adjusted with those obtained the data for the experiment of heat transfer, friction factor and tee within data range of (+6 to –5)%, (+4 to –6)%, and (+6 to –3)%, respectively [11]. another recent study of gugulothu [12] has been conducted a cfd analysis to investigate the ribbed tube with different twisted tapes insert (fltt, hlutt, hldtt) at uniform heat flux condition to sort out the performance characteristics of thermal efficiency, friction factor and mean nusselt number. air was treated as a working fluid and the simulations (ansys fluent) were carried out in a turbulent region by choosing suitable re and found fttt showed a better heat transfer, friction factor and enhancement efficiency compared to hltt as a numerical result. the main purpose of this comparison was to understand the rate of heat flow and temperature distribution along with the various length of the pipes. the study also observed that in the case of hlutt and hldtt tapes, there is a decrease in the thermal performance factor with an increase in re and twisted ratios which are showing in figure 4, whereas in the case of fltt, the thermal performance factor tends to increase with different twisted ratios and improvements of re [12]. figure 1: twisted tape inserts [9]. figure 2: (a) heat flux and average htc variation in the plain and tt tubes. (b) the overall heat transfer performance for tt tubes and the plain tubes [10]. a b ahmed and abedin (2020): international journal of engineering materials and manufacture, 5(4), 130-147 133 figure 3: comparison between the predicted and experimental data (a) nusselt number (b) friction factor (c) thermal enhancement efficiency [11]. figure 4: variation of re with thermal performance factor for a twist ratio of 0.14 with q=2300 w/m 2 [12]. paneliya et al., [13] found 1.27 times larger heat transfer enhancement for x-shaped tapes than twisted tape inserts by comparing the thermal characteristic of water flowing in a tube equipped with x-tape and twisted tape to investigate the effect of insert tape geometry on the heat exchanger tubes [13]. the material of the insert tapes was stainless steel in this study. the thermal performance of the heat exchanger tube has been analyzed for this experiment in terms of heat transfer rate (q), nusselt number (nu) and friction factor (f). the investigation also conducts a cfd analysis to validate the obtained results and observed that the modified geometry of tapes played a vital role to enhance the heat transfer characteristic and thermal performance where turbulence intensity occurred, showed in figure 5. a b c review on heat transfer enhancement by insert devices 134 the comparison between typical tt and sparsely placed tt with multiple transverse tt studied by samruaisin et al., [14] and observed the tube with sparsely placed tt installed with multiple transverse twisted-baffles gave the highest thermal enhancement factor of 1.32. the study also found an additional flow disturbance caused by the multipletransverse twisted baffles and the combined actions of swirl flow caused by the twisted tape inserts [14]. figure 6 shows the copper tube with a sparsely placed twisted tape combined with multiple transverse twisted baffles. wijayantaa et al., [15] illustrated the limited number of studies of heat transfer enhancement regarding the wingpitch ratio. to experiment in this field, they improved single-phase convective heat transfer with water as working fluid under a condition of 5,300 to 14,500 reynolds number. it is revealed from the study that the delta wing tape inserts with a wing-pitch ratio of 1.18 produces the greatest thermal performance factor of 1.15 and offers the highest average nusselt number of 177% compared to a plain tube [15]. figure 7(a) shows the geometry and figure 7(b) illustrates the photograph of the delta wing tape inserts. in the other recent investigation of liu et al., [16] indicates that the geometric parameters like twist ratio and length ratio play an important role in heat transfer enhancement. the results showed that a segmented tape insert in pipe flow can increase the overall heat transfer rate by 23.5% and the friction factor by 235%, while local improvement along the tube can be 2.8 times more than the plain tube [16]. figure 8 illustrates the relationships between heat transfer coefficient and twist ratio along the tube. figure 5: the turbulence intensity inside the different setups (a) plain tube (b) x -shape tape (c) stainless steel variable [13]. figure 6: copper tube with a sparsely placed twisted tape combined with multiple transverse twisted baffles [14] figure 7: (a) geometry of the delta wing tape inserts (b) photographs of delta-wing tape inserts [15]. a b ahmed and abedin (2020): international journal of engineering materials and manufacture, 5(4), 130-147 135 to demonstrate the flow behaviors and corresponding heat transfer, jundika et al., [17] added a twisted tape inserts in helical tube heat exchanger at a higher frictional pressure drop conditions and found four times enhanced heat transfer performance compared to conventional straight tube heat exchangers. the working methods of this experiment like lowering the twisting ratio and prandtl number (air) respectively promote higher secondary flow and increase the re number which increased the heat transfer enhancement ratio. finally, it predicts the heat transfer and pressure drop for practical applications by developed a correlation between nusselt number and friction factor for water and air as a fluid medium which is illustrated in figure 9 and figure 10, respectively [17]. figure 8: relationship between heat transfer coefficient and twist ratio (p/d) along the tube: (a) length ratio, l/p = 0.3, (b) length ratio, l/p = 0.5, (c) length ratio, l/p = 0.7 [16]. figure 9: (a) average nusselt number of water flow for various configurations at twall = 333.15 k. (b) friction coefficient of water flow for various configurations at twall = 333.15 k [17]. a b review on heat transfer enhancement by insert devices 136 figure 10: (a) average nusselt number of air flow for various configurations at twall = 333.15 k. (b) friction coefficient of air flow for various configurations at twall =333.15 k [17]. figure 11: wire coil insert [18]. 4 wire coil inserts wire-coil inserts have been utilized as another significant passive heat transfer enhancement technique besides the twisted tape inserts and widely used in various heat transfer equipment. this kind of inserts has several advantages compared to other enhancement techniques like easy installation and removal, simple manufacturing process with low cost, preservation of original plain tube from mechanical strength, the possibility of installation in an existing smooth tube heat exchanger, fouling mitigation in refineries, chemical industries, and marine applications. figure 11 illustrates a wire coil insert that should be applied instead of a smooth one to obtain higher heat transfers [18]. abedin and sarkar [19] investigated the enhancement of turbulent heat transfer flow of air through one smooth tube and four different tubes with wire coil inserts at low reynolds numbers and find that the turbulent heat transfer coefficient approximately two-folds higher, the friction factors could be as much as four-folds higher and the effectiveness might be as much as 1.25 folds higher than those for the smooth tubes with similar flow conditions showed in figure 12(a). the investigation has also developed a correlation to predict the turbulent heat transfer coefficients through the tubes at low reynolds numbers illustrate in figure 12(b) [19]. goudarzi and jamali [20] used two-wire coil inserts with different geometry and aluminium oxide (al2o3) in ethylene glycol (eg) as nanofluid to experiment the heat transfer enhancement and found that the use of coils inserts enhanced heat transfer rates up to 9%. the experiment concludes that the coil inserts with the nanofluid with a concentration of 0.08%, 0.5% and 1% result the thermal performance enhancement up to 5% as compared to the use of coil inserts alone [20]. figure 13 demonstrates a relation between thermal performance factor and reynolds number for tube inserts, where the values of thermal performance factors are not significantly different for different reynolds numbers. wanga et al., [21] configured a helical coil device as 360 0 plastic tubing with or without wire coil inserts placed after each 180 0 of the main helical coil loops to investigate the flow and heat transfer characteristics of water. the setup influences the fluid mixing, pressure drop, and other thermal performance characteristics which should have a direct impact on the thermal performance of the helical coil heat transfer devices. the experimental results showed that the structural modifications with the wire coil of the conventional helical coil configuration led to enhance heat transfer in the test section while the pressure drop penalty increased slightly [21]. table 1 depicts the pressure drop increases with the curvature ratio and lower pitch values of the wire coil in reversed loop helical coil tubes. 5 other types of insert devices besides twisted tape and wire-coil inserts, different types of inserts have been utilized in different industries and applications to get efficient heat transfer enhancements. helical coils, air-foil shaped inserts, v-winglets such kind of enhancers which are applied on various applications to achieve better performance. a b ahmed and abedin (2020): international journal of engineering materials and manufacture, 5(4), 130-147 137 figure 12: (a) variation of average effectiveness against reynolds number for smooth tube and wire-coil inserted tubes. (b) prediction of heat transfer coefficients for wire-coil inserted tube (pitch =50 mm, helix angle, α=450) [19]. figure 13: thermal performance factor vs reynolds number for tube inserts [20]. table 1: heat transfer enhancement for helical coils with reversed loops and wire coil inserts [21]. inlet velocity (m/s) reynolds number 𝐇𝐞𝐚𝐭 𝐭𝐫𝐚𝐧𝐬𝐟𝐞𝐫 𝐄𝐧𝐡𝐚𝐧𝐜𝐞𝐦𝐞𝐧𝐭 𝐑𝐚𝐭𝐢𝐨 = 𝐇𝐞𝐚𝐭 𝐭𝐫𝐚𝐧𝐬𝐟𝐞𝐫 𝐜𝐨𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐭 𝐨𝐟 𝐞𝐧𝐡𝐚𝐧𝐜𝐞𝐝 𝐡𝐞𝐥𝐢𝐜𝐚𝐥 𝐜𝐨𝐢𝐥 𝐥𝐨𝐨𝐩 𝐇𝐞𝐚𝐭 𝐭𝐫𝐚𝐧𝐬𝐟𝐞𝐫 𝐜𝐨𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐭 𝐨𝐟 𝐏𝐥𝐚𝐢𝐧 𝐡𝐞𝐥𝐢𝐜𝐚𝐥 𝐜𝐨𝐢𝐥 𝐥𝐨𝐨𝐩 reversed loop curvature ratio and wire-coil insert pitch 1/2(no insert, reversed loop only) 1/2 (3mm) 1/2 (20mm) 1/3(no insert, reversed loop only) 1/3 (3mm) 1/3 (20mm) 1.5 14,037 1.04 1.09 1.04 1.04 1.1 1.07 1.9 17,780 1.06 1.28 1.1 1.09 1.26 1.2 2.3 21,523 1.09 1.29 1.12 1.16 1.27 1.23 2.7 25,266 1.12 1.23 1.11 1.17 1.22 1.18 a b review on heat transfer enhancement by insert devices 138 5.1 helical coil insert with ribs virgilioa et al., [22] reveal that the discontinuous rib has a lower impact on the pressure losses on the azimuthal swirl and the turbulent kinetic energy generations, by examining the effects of the discontinuity in the tube corrugations on the flow separations, turbulence statistics, vorticity and strain rates of the flow particles. the investigation also compares them with a previously studied continuous turbulator and found that the changing height of the discontinuous rib generates turbulent kinetic energy and an azimuthal velocity respectively 50% and 35% in the field close to the wall which is lower than the continuous configuration. the irregularity of the discontinuous obstacle provides a reduced skin friction coefficient which is 0.57 times lower than previously experimented 2-d helical turbulator. it is also observed that the less intense wall-bounded turbulence level occurs with the 3-d helical turbulator which suggests a lower local heat transfer enhancement [22]. in figure 14 the schematic of continuous and discontinuous helical turbulators is shown. 5.2 air foil-shaped insert gururatana and skullong [23] was chosen the aerofoil-shaped inserts, modified-naca0024 to improve the heat transfer performance in the tubes and found that the modified-naca0024 with an inclination angle of 45° can provide the best heat transfer enhancement as much as 3 times over the plain tube as well as achieve the maximum heat transfer enhancement performance of 1.45 [23]. figure 15 is illustrated the geometry of the modified-naca0024 airfoil-shaped insert. figure 14: schematic of continuous and discontinuous helical turbulators: (a)rib-1 (b)rib-2 [22]. figure 15: photograph and geometry of modified-naca0024 airfoil-shaped insert [23]. ahmed and abedin (2020): international journal of engineering materials and manufacture, 5(4), 130-147 139 figure 16: variation of tef with re for (a) v-up dw inserts and (b) v-down dw inserts [24]. 5.3 v-winglet promvonge et al., [24] have shown that the discrete-v-winglet provides a higher thermal performance enhancement factor compared with the typical v-winglets. to explore these findings, a numerical model of the inserted tube flow structures and the heat transfer patterns from the simulation such as temperature contours and streamlines including the nusselt number contours were proposed by him. it is also observed from this experiment that the v-down dw provides a better heat transfer and the thermal performance enhancement factor than the v-up one is around 3.6% and 1.6% respectively [24]. figure 16(a) and figure 16(a) illustrates the variation of thermal performance enhancement factor with re for v-up dw inserts and v-down dw inserts, respectively. 6 combination of nanofluid with different types of insert some researchers enhance the heat transfer rates in various thermal systems by combining two passive techniques like nanofluids and inserts. rashidi et al., [25] worked regarding in this issues for heat transfer improvement where a combination of nanofluid with twisted tapes, wire coils, baffles, and vortex generators showed that the vortex generator is more effective compared with nanofluids on the efficiency of plate-fin heat exchangers and wire coil with the sharp-edged shoe has superior heat transfer efficiency in comparison with the circular one, as well as nanofluid has significant heat transfer efficiency when employed with thicker twisted strips and it is better to employ helical baffles with a small helix angle to achieve maximum enhance heat transfer [25]. 6.1 nanofluids with twisted tape inserts twisted tapes can be widely utilized in the tube due to their significant impact to enhance the heat transfer and thermal performance characteristics. it should be pointed out that by coupling the twisted tapes and nanofluid has a significant potential to achieve the combined advantages of enhancement. by employing twisted tapes with nanoparticles as base fluid and increase liquid mixing and improve the heat transfer enhancement. some scientists conduct various numerical and experimental works to achieve higher values of heat transfer performance by combining these methods and found nanofluids have superior heat transfer efficiency when employed with thicker twisted strips [25]. 6.2 nanofluids with wire coil insert as a turbulent promoter, wire coils can be used to enhance the turbulence of the working fluids and shows a larger value of the heat transfer rate. wire coils operate as artificial roughness at larger values of the reynolds numbers. they are reliable in terms of hot spots and corrosion effects and their performance depends on their geometry and the considered flow regime. this is also observed from the study that more enhancement can be achieved in the heat transfer rates on nanofluids, by using a wire coil inserts with a larger diameter [25]. 6.3 nanofluids with baffles initially, helical baffles are introduced as a replacement for segmental types insert. the main function of baffles is to interrupt both hydrodynamic and thermal boundary layers as well as improve heat transfer performance. many researchers studied the combined impact of baffles and nanofluids in the field of thermal efficiencies and found that the baffles can achieve high heat transfer rates and small pressure drops when using in nanofluid combinedly with a small helix angle. it is also observed that a small displacement of the baffles influences the flow and temperature fields [25]. a b review on heat transfer enhancement by insert devices 140 6.4 nanofluids with vortex generators vortex generators can be used to influence the flow field and the boundary layer development as well as create swirl flow and transfer a great fluid between the center and the wall of the tube, causing a significant heat transfer between the flow and the tube surfaces. it is observed that the vortex generator is more effective in comparison with the nanofluids on the efficiency of plate-fin heat exchangers. figure 17 shows the different kinds of vortex generators [25]. 7 summary different types of insert devices are studied regarding their enhancement performance with thermal characteristics in this paper. some of those are applied individually and some are applied with nanofluids or different arrangements. to figure out the heat transfer enhancement performance of insert devices, it is convenient to represent it in a table with some graphical illustrations. table 2 shows the observation of recent investigations on various types of insert devices in terms of heat transfer enhancement and their impacts on thermal performance characteristics in different flow and mediums, and it is found that a small variation of thermal properties can influence the heat transfer rate whereas the geometry of the insert tube needs a considerable change to enhance the heat transfer rates. it also appeared that the spacing between insert devices, twist ratios, width ratios, and flow conditions of the medium influence the performance of enhancement characteristics. it is considered that twisted tape insert mixes the bulk flow well and therefore, performs better in a laminar flow than turbulent flow. compared to the wire coil, the twisted tape is not effective in the turbulent flow because it blocks the flow and creates a large pressure drop. hence, the thermo-hydraulic performance of a twisted tape is not good compared with a wire coil in a turbulent flow. therefore, it may be concluded that, for compact heat exchanger design, a wire coil is a good choice in a turbulent flow. however, the other several passive techniques such as baffles, winglets and airfoil-shaped insert, etc. are generally more efficient in the turbulent flow than in the laminar flow. figure 17: different kinds of vortex generators: delta wing, rectangular wing, delta winglet pair and rectangular winglet pair [25]. table 2: observation of recent investigations on various types of insert device in terms of heat transfer enhancement. insert device configuration with [reference] working fluid conditions observation twisted tape inserts tt (stainless steel) [10] hydrocarbon fuel (kerosene) (2700 ≤ re ≤ 20000); twist ratio = (6.31, 12.63) (1) the average htc for the tt tube was approximately 18% larger than that for the plain tube, as well as the smaller twist ratio was responsible for excellent fluid mixing and a higher htc. pttt [11] air (7,250 ≤ re ≤ 49,800); porosities= (1.2, 4.6, 10.4 and 18.6%) (1) pttt insert with a porosity of 4.6%, provided the highest heat transfer enhancement is 320%, highest friction factor which is 355% and maximum tee of 1.5 compared to those of the smooth tubes. ribbed tube with (pt, fltt, hlutt) [12] air (25000 ≤ re ≤ 110000) (1) fttt shows better heat transfer, friction factor, and enhancement efficiency compared to hltt. (2) compared to the plain tube with inserts the heat transfer coefficient of (8-36%) was estimated as higher in the case of hlutt. (3) the thermal performance factor decreases ahmed and abedin (2020): international journal of engineering materials and manufacture, 5(4), 130-147 141 with an increase in re and twist ratios in the case of hlutt and hldtt twisted tapes. twisted tapes (x-shaped and twisted tape insert) [13] water twist ratio= (3,4); nusselt number = (2.91 to 5.16 for the xshaped and 2.52 to 4.46 and 3.07 to 5.33 for constant and variable pitch twisted tape) (1) the x-shaped tape inserts showed significant high heat transfer rates of 1.27 and 1.08 times greater in comparison with the constant pitch and variable pitch twisted tape inserts. (2) to enhance the heat transfer characteristics and thermal performance of the heat exchangers, turbulence intensity and swirl flow of the fluid near the wall surface consider as significant factors. (3) to enhance the overall performance of the heat exchanger, effective geometry is essential because of the increments in the turbulence intensity caused by the x-shaped tape inserts. sparsely placed twisted tapes [14] air (6000 ≤ re≤ 22000); twist ratio (2.0, 2.5, 3.0 and 3.5) (1) sparsely placed twisted tapes installed with multiple transverse twisted baffles showing the maximum thermal performance factor of 1.32 at a reynolds number of 6000, twist ratio of 3.5, and width ratio of 0.22. double-sided delta-wing tape insert [15] water (5300 ≤ re ≤ 14500); pitch ratio = 1.18; (1) t-w inserts with a p/w of 1.18 produces the greatest thermal performance factor of 1.15. (2) t-w inserts with a p/w of 1.18 offer the highest average nusselt number of 177% compared to a plain tube. (3) the tube having t-w inserts with p/w of 1.18 produces the highest friction factor, which is 11.6 and 2.72 times greater than the plain tube. segmented twisted tape insert [16] air (10000 ≤ re ≤ 35000); twist ratio = (2.0, 3.3 and 4.6); length ratio = (0.3, 0.5 and 0.7) (1) segmented twisted tapes can increase the local heat transfer coefficient up to 2.8. (2) twist ratio plays a more critical role in local heat transfer enhancement over length ratio, and a smaller twist ratio usually has a better performance. helical tube with twisted tape insert [17] air, water (100 ≤ re ≤ 2000) (1) twisted tape inserts with helical tube heat exchanger at a higher frictional pressure drop conditions show 4 times enhanced heat transfer performance compared to the conventional straight tube heat exchanger. wire-coil inserts wire-coil insert [18] air twist ratios = (3.5, 2.66 and 2.25); pitch ratio = 0.88 (1) the higher heat transfer can be achieved by using wire coils inserts instead of a smooth one. (2) copper has a higher thermal conductivity of 94% than brass (66%) and aluminum (91%) as a wire coil insert. wire-coil insert [19] air (6000≤re≤ 22000); pitches = 12, 24, 40, and 50 mm with correspondin g helix angles =10 0 , 20 0 , 35 0 , and 45 0 , respectively (1) the friction factor for the wire coil inserted tubes becomes as much as 4 times higher than smooth tubes, for comparable reynolds numbers. (2) for similar flow conditions, the average heat transfer coefficient for tubes with a wire coil inserts increase 2 times than the smooth tubes. (3) the heat transfer effectiveness for the wirecoil inserted tubes increases as much as 1.25 times than that of the smooth tubes, for comparable reynolds numbers. review on heat transfer enhancement by insert devices 142 wire-coil insert [20] al2o3-eg nanofluid (18500 < re < 22700); (concentrati ons of nanofluid= 0.08%, 0.5% and 1%) (1) the wire coil inserts with the nanofluid with a concentration of 0.08%, 0.5% and 1% results the thermal performance enhancement up to 5% as compared to the use of coils inserts alone. (2) the values of thermal performance factors are not significantly different for different cases of reynolds number. helical coils with wire coil insert [21] water (6000 < re < 27000) (1) the structural modifications of the conventional helical coil with wire coil insert configuration led to better thermal performance while the pressure drop increased slightly up to 115% with curvature ratios. other types of inserts 2-d and 3-d helical inserts [22] water (20000 < re < 80000); pitch to diameter ratio = 11; height to diameter ratio = 3.6%; (1) friction coefficients of the continuous and discontinuous turbulators are respectively 7 and 4 times higher than the case of a smooth pipe. (2) compared to previously experimented 2-d helical turbulator the irregularity of the discontinuous obstacles provides a 0.57 times lower skin friction coefficient. (3) the 3-d helical turbulator suggests a lower local heat transfer enhancement when less intense wall-bounded turbulence occurs. airfoil-shaped insert, (modified naca0024) [23] air (4196 < re < 8125); inclination angle = (0°, 30° and 45°) (1) the modified naca0024 with an inclination angle of 45° is showed the most effectiveness and the maximum heat transfer enhancement performance of 1.45. discrete-v winglet tape [24] air (4200 < re < 25800); winglet pitch = (0.5, 1.0, 1.5 and 2.0) (1) the discrete-v winglet tape (dw) provides a considerable heat transfer enhancement in the tubes. (2) compared to v-up dw, the v-down dw provides better heat transfer and thermalperformance enhancement factor which is 1.6% and 3.6% respectively. nanofluids with different types of inserts combination of nanofluids and twisted tape inserts [25] nanofluid (al2o3, cuo, tio2 and cnt with water) (100 < re < 30,000) (1) nanofluids have superior heat transfer efficiency when employed with thicker twisted strips. (2) twisted tape with alternated axis has a larger value of heat transfer of 89% as compared with the case of ordinary twisted tapes. combination of nanofluids and wire coil insert [25] nanofluid (fe3o4, al2o3, cuo and grapheme oxide–water) (10 < re < 22,700) (1) more improvement can be achieved in the heat transfer rates on nanofluids by using a wire coil with a larger diameter. (2) wire coil inserts with grapheme oxide– water nanofluid improves the heat transfer rate up to 77%. combination of nanofluids and baffles [25] nanofluid (al2o3, cuo, tio2 and cnt with water) (50 < re < 15,000) (1) a small displacement of the baffle leads to an intense change in the flow and temperature fields. it is better to employ helical baffles with a small helix angle to achieve a high heat transfer rate of 255% and small pressure drops. vortex generators [25] nanofluid (al2o3, cu and tio2 with water) (50 < re < 12,200) (1) the usage of a vortex generator is more effective in comparison with the nanofluid on the efficiency of plate-fin heat exchangers. (2) employing nanofluid with a vortex generator can enhance the performance of up to 27%. ahmed and abedin (2020): international journal of engineering materials and manufacture, 5(4), 130-147 143 to summarize the above observations, different insert devices have been classified into four major categories of inserts such as twisted tape inserts, wire coil inserts, other types of inserts and nanofluids with inserts. in each category, there are also two or more sub-elements classified according to the geometry or names of the inserts. by analyzing the above results of different researchers, table 3 shows the important findings of thermal performance characteristics and heat transfer enhancement of different insert devices with suitable geometrical conditions. to observe the impact on performance characteristics of heat transfer enhancement it is found that x-shaped tape insert shows 27.7 times greater friction factor compared to a smooth tube with an equivalence heat transfer enhancement of 355%. on the other hand, the wire coil insert with a reverse loop arrangement shows the highest pressure drop of 115% and twisted tapes include helical tube shows 0.35 of pressure drop factor with 4 times enhancement performance. the heat transfer enhancements of these insert devices compare to the smooth tube are illustrated in figure 18 to figure out the maximum performance of heat transfer enhancement achieved by various scientists by using different types of insert devices in different conditions. an equivalent heat transfer enhancement parameter of these insert devices is considered to compare the corresponding inserts enhancement performance with smooth tubes and found that the twisted tape with helical tube shows the highest equivalence heat transfer enhancement of 400%. as an effective geometry of tape inserts, the x-shaped tape insert shows the second-highest equivalent heat transfer enhancement of 355% whereas the wire coil insert shows the least performance of 9% compares to a smooth tube without any use of insert devices. the graphical representation of the above findings is illustrated in figure 19, and it is observed that compared to identical inserts without any nanofluids it can be achieved up to 255%, 89%, 77%, and 27% of equivalence heat transfer enhancement by baffles, twisted tapes, wire coils, and vortex generator, respectively when using with nanofluids as a flow medium. table 3: important findings of literature reviews regarding the heat transfer enhancement with various insert devices compared to smooth tubes. insert devices geometry ff pd htc hte htr htp tef hte equivalence to smooth surface reference twisted tape insert tt 18% 18% [10] pttt 355% 320% 1.5 320% [11] x-shaped tape insert 27.7 times 3.55 times 355% [13] sparsely placed tt with baffles 2.52 times 1.32 252% [14] t-w inserts 11.5 [15] segmented twisted tapes 235% 2.8 times 235% 235% [16] tt with helical tube 0.35 4 times 400% [17] wire coil insert wire coil 4 folds 2 folds 1.25 [19] wire coil 11.18% 9% 5% 9% [20] wire coil (reversed loops) 115% [21] other types of inserts helical insert 7 times [22] air-foil shaped insert 3 times 1.45 300% [23] discrete-v winglet tape (down) 2.02 [24] review on heat transfer enhancement by insert devices 144 table 4 depicts another important finding from literature reviews regarding the heat transfer enhancement and thermal characteristics of various insert devices with a combination of nanofluids which is compared with the corresponding insert device alone. it is noticed that the twisted tape inserts achieved the friction factor of 23.69 with 89% enhancement of heat transfer whereas helical baffles with small helix angle achieved the highest equivalence heat transfer enhancement of 255% as well as 150% pressure drops compare to inserts without nanofluids arrangement. comparative graphical representation of equivalence heat transfer enhancement among four major classifications of the insert device is illustrated in figure 20. as can be seen from the figure the twisted tape inserts have the highest heat transfer enhancement of 400% followed by that for air-foil shaped inserts having a value of 300% followed by that for nanofluids with baffles having a value of 255% followed by that for wire coil having a value of 9%. figure 18: equivalent percentage of heat transfer enhancement with different insert devices. table 4: important findings of literature reviews regarding the heat transfer enhancement of various insert devices with nanofluids compared to the corresponding insert device alone. insert devices with nanofluids ff pd htc hte htr htp tef hte equivalence for nanofluid reference twisted tape 23.69 89% 89% [25] wire coil 77% 77% [25] baffles 150% 255% 255% [25] vortex generator 8.50% 27% 27% [25] 18% 320% 355% 252% 235% 400% 9% 300% 0% 50% 100% 150% 200% 250% 300% 350% 400% 450% tt [10] pttt [11] x-shaped tape insert [13] sparsely placed tt [14] segmented tt [16] tt with helical tube [17] wire coil insert [20] air-foil shaped insert [23] h e a t t r a n s f e r e n h a n c e m e n t [ % ] insert devices ahmed and abedin (2020): international journal of engineering materials and manufacture, 5(4), 130-147 145 figure 19: the equivalence heat transfer enhancement of various insert devices with nanofluid compared to identical insert devices without nanofluids. figure 20: comparative representation of heat transfer enhancement by classified inserts. 8 conclusions the study about the effect of inserts on heat transfer characteristics has been reviewed. different types of inserts in various conditions and arrangements have been considered. the main conclusions can be briefly drawn as follows. 1) to enhance the heat transfer characteristics and thermal performance of the heat exchangers turbulence intensity and swirl flow of the fluid near the wall surface consider as significant factors. effective geometry is another important condition to enhance the overall performance which can able to increase the turbulence intensity caused by various insert devices like twisted tapes. the twist ratio of the twisted tape plays a significant role in local heat transfer enhancement over length ratio and smaller twist ratio generally responsible for excellent fluid mixing as well as better performance. from the above information, it can be inferred that due to turbulence intensity and swirl flow of the fluid near the wall surface twisted tape with a helical tube at a frictional pressure drop of 0.35 can enhance the maximum equivalent heat transfer rate up to 400%. moreover, tubes with pttt, x-shaped tape insert, sparsely placed tt, segmented tt also enhance the equivalent percentage of heat transfer up to 320%,355%,252% and 235% respectively, compared to smooth tubes. 89% 77% 255% 27% 0% 50% 100% 150% 200% 250% 300% twisted tape [25] wire coil [25] baffels [25] vortex generator [25] h e a t t r a n s f e r e n h a n c e m e n t [ % ] insert devices with nanofluid hte equivalence with nanofluid 0% 50% 100% 150% 200% 250% 300% 350% 400% 450% h e a t t r a n s f e r e n h a n c e m e n t [ % ] insert devices review on heat transfer enhancement by insert devices 146 2) wire coil inserts have several advantages compared to other enhancement techniques because of its geometry and easer applications. the heat transfer effectiveness for the wire coil inserted tubes increases as much as 1.25 times than that of the smooth tube for comparable reynolds numbers whereas the coil inserts with the nanofluid with a concentration of 0.08%, 0.5%, and 1% results in the thermal performance enhancement up to 5% as compared to the use of coils inserts alone. in addition, the structural modifications of the conventional helical coil with a wire coil insert configuration led to better thermal performance while the pressure drop increased up to 115% with the curvature ratio. the literature found that the wire coil inserts can achieve as maximum as 9% of equivalence heat transfer enhancement with 11.18% of friction factor. 3) helical inserts, dw and air-foil shaped inserts are another significant insert device in the field of heat transfer enhancement. as an enhancer, friction coefficients of the continuous and discontinuous helical inserts are respectively 7 and 4 times higher than the case of smooth tubes. compared to v-up dw, the v-down dw provides better heat transfer and thermal performance enhancement up to 1.6% and 3.6% respectively. moreover, the modified air-foil shaped insert with an inclination angle of 45° is the most effective and shows the maximum equivalence heat transfer enhancement up to 300%. 4) as a passive enhancement technique, nanofluids have superior heat transfer efficiency when employed with thicker twisted strips and helical baffles with a small helix angle which provides a maximum equivalence heat transfer rate of 255%. in addition, twisted tape with nanofluids has a larger value of heat transfer of 89% as compared with the case of ordinary twisted tapes. on the other hand, wire coil inserts with grapheme oxide– water nanofluid improve the heat transfer rate up to 77%. 5) the twisted tape inserts have the highest heat transfer enhancement of 400% followed by that for air-foil shaped inserts having a value of 300% followed by that for nanofluids with baffles having a value of 255% followed by that for wire coil having a value of 9%. references [1] tabatabaeikia, s., mohammed, h. a., nik-ghazali, n., and shahizare1. b. (2014). heat transfer enhancement by using different types of inserts. hindawi publishing corporation advances in mechanical engineering, (13) 250354. [2] shriwas, d., and saini, j. (2018). heat transfer enhancement technique in heat exchanger: an overview. ijrti 3 (9), 2456-3315. [3] maradiya, c., vadher, j., and agarwal, r. (2018). the heat transfer enhancement techniques and their thermal performance factor. journal of basic and applied sciences, 7, 1–21. [4] lv, j.y., liu, z.c., and liu, w. (2020). active design for the tube inserts of center-connected deflectors based on the principle of exergy destruction minimization. international journal of heat and mass transfer, 150(2020)119260. [5] kiran, k., asalammaraja, manoj, and umesh, c. (2014). a review on effect of various types of tube inserts on performance parameters of heat exchanger. international journal of research in advent technology, 2 (6), 2321-9637. [6] klemes, j. j., qiu-wang, w., varbanov, p., zeng, m., china, h.h., lal, n. s., nian-qi, li., wang, b., xuechao, w., and walmsley, t.g. (2020). heat transfer enhancement, intensification and optimization in heat exchanger network retrofit and operation. renewable and sustainable energy reviews, 120 (2020), 109644. [7] liu, s., and sakra, m. (2013). a comprehensive review on passive heat transfer enhancements in pipe exchangers. renewable and sustainable energy reviews, 19, 64–81. [8] hasanpour, a., farhadi, m., and sedighi, k. (2014). a review study on twisted tape inserts on turbulent flow heat exchangers: the overall enhancement ratio criteria. international communications in heat and mass transfer, 02977, (10). [9] saha, s. k. (2020). heat transfer fundamentals for design of heat transfer enhancement devices. introduction to enhanced heat transfer, springer briefs in applied sciences and technology, doi: 10.1007/978-3-030-20740-3_11. [10] feng, s., cheng, x., qincheng, b., pan, h., and liu, z. (2020). experimental investigation on convective heat transfer of hydrocarbon fuel in circular tubes with twisted-tape inserts. international journal of heat and mass transfer, 146 (2020), 118817. [11] bhuiyan, m.m.k., roshid, m., talukder, m. m., rasul, m. g., and das, p. (2019). influence of perforated triple twisted tape on thermal performance characteristics of a tube heat exchanger. doi: 10.1016/j.applthermaleng.2019.114769. [12] gugulothu, s.k. (2020). computational fluid dynamics analysis in a ribbed tube with different twisted tape inserts to enhance the heat transfer. international journal of ambient energy, doi: 10.1080/01430750.2020.1722224. [13] paneliya, s., khanna, s., mankad, v., ray, abhijit, prajapati, p., and mukhopadhyaya, i. (2019). comparative study of heat transfer characteristics of a tube equipped with x-shaped and twisted tape insert. https://doi.org/10.1016/j.applthermaleng.2019.114769 https://doi.org/10.1016/j.applthermaleng.2019.114769 ahmed and abedin (2020): international journal of engineering materials and manufacture, 5(4), 130-147 147 [14] samruaisin, p., kunnarak, k., chuwattanakul, v., and eimear, s. (2019). effect of sparsely placed twisted tapes installed with multiple-transverse twisted-baffles on heat transfer enhancement. journal of thermal analysis and calorimetry, doi:10.1007/s10973-019-09202-8. [15] wijayantaa, a. t., yaningsiha, i., juwana, w. e., aziz, m., and miyazaki, t. (2020). effect of wing-pitch ratio of double-sided delta-wing tape insert on the improvement of convective heat transfer. international journal of thermal sciences, 151 (2020), 106261. [16] liu, g., yang, chen, zhang, junhui., zong, h., xu, b., and jin-yuan, q. (2020). internal flow analysis of a heat transfer enhanced tube with a segmented twisted tape insert. institute of process equipment, college of energy engineering. [17] jundika. c., kurniaa, chaedir, b., agus, p., and sasmito (2020). laminar convective heat transfer in helical tube with twisted tape insert. international journal of heat and mass transfer, 150 (2020) 119309. [18] sonawane, t., patil1, prafulla, chavhan1, a., and dusane, b. m. (2016). a review on heat transfer enhancement by passive methods. international research journal of engineering and technology, 3 (9). [19] abedin, m. z and sarkar, m. a. r. (2018). experimental study of heat transfer enhancement through a tube with wire-coil inserts at low turbulent reynolds number. international journal of engineering materials and manufacture, 3(3) 122-133. doi: /10.26776/ijemm.03.03.2018.01. [20] goudarzi, k. and jamali, h. (2017). heat transfer enhancement of al2o3-eg nanofluid in a car radiator with wire coil insert. applied thermal engineering, 118, 510–517. [21] wanga, y., jorge, l., alvarado, and terrell, w. (2020). thermal performance of helical coils with reversed loops and wire coil inserts. international journal of heat and mass transfer, 146, 118723. [22] virgilioa, m., mayoa, i., dedeynec, j., geem, k.m. v., marin, g.b., and artsa, t. (2020). effects of 2-d and 3-d helical inserts on the turbulent flow in pipes. experimental thermal and fluid science, 110, 109923. [23] gururatana, s. and skullong, s. (2019). experimental investigation of heat transfer in a tube heat exchanger with airfoil-shaped insert. case studies in thermal engineering, 14 (2019) 100462. [24] promvonge, p., promthaisong, p. and skullong, s. (2020). experimental and numerical heat transfer study of turbulent tube flow through discrete v-winglets. international journal of heat and mass transfer, 151, 119351. [25] rashidi, s., eskandarian, m., mahian, o., and poncet, s. (2018). combination of nanofluid and inserts for heat transfer enhancement. journal of thermal analysis and calorimetry, doi:10.1007/s10973-018-70709.(0123456789. https://doi.org/10.1007/s10973-019-09202-8 https://doi.org/10.26776/ijemm.03.03.2018.01 https://doi.org/10.1007/s10973-018-7070-9.(0123456789 https://doi.org/10.1007/s10973-018-7070-9.(0123456789 international journal of engineering materials and manufacture (2021) 6(1) 34-42 https://doi.org/10.26776/ijemm.06.01.2021.03 mrityunjoy hazra and ashok kumar singh defence metallurgical research laboratory (dmrl) p.o. kanchanbagh, hyderabad 500 058, india e-mail: mhazra@dmrl.drdo.in reference: hazra, m. and singh, a.k. (2021). failure analysis of bolt of rear mounting trunion of an aero-engine: a case of bending induced chevron pattern as well as fatigue failure on the same fracture surface. international journal of engineering materials and manufacture, 6(1), 34-42. failure analysis of bolt of rear mounting trunion of an aero-engine: a case of bending induced chevron pattern as well as fatigue failure on the same fracture surface mrityunjoy hazra and ashok kumar singh received: 09 october 2020 accepted: 27 january 2021 published: 30 january 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract present work describes the failure investigation of failed bolt of starboard rear mounting trunion of an aero-engine. multiple fracture initiation points are noticed. this is a classic case of a single bending type of load initiating reversed bending fatigue as well as chevron pattern on the same fracture surface. visually observed bending phenomenon supports the each type of failure mode. more interestingly, point of initiation of fast as well as the reversed bending fatigue failure is the same, although those two events have been found to be separate phenomena. it has been established that two different fatigue crack fronts, typical of reversed bending fatigue phenomenon propagated towards each other to make half of the cross-section fractured, while the another half failed by chevron patterned fast fracture. in this, the fast fracture of one half has preceded the reversed bending fatigue fracture of the other half, although the former is not responsible for happening of the later. modes of fracture and factors influencing have been established in this article with emphasis on circumstantial evidence involving background information and visual examination, supported often by the open literature. presence of cadmium (cd) and its possible source, residence time and relative presence on differently fractured surfaces have offered important clues on establishing the sequence and relative inter-dependence of the said two fracture types. presence of cadmium on the fracture surfaces, multiple crack initiation sites and numerous well-revealed secondary cracks on branson cleaned fracture surface indicate that the cracks pre-existed on the material even before the cadmium plating and manifestation of chevron pattern is its extreme revelation. this pre-existing chevron pattern primarily aggravated the present failure through bending fatigue phenomenon in the later stages. low alloy steel (astm grade 16) with presently used hardness (340 hv) level does not seem to suit the present application, as it is clear from its extreme brittleness as manifested by pre-existing cracks. key words: bolt fracture, chevron pattern, bending fatigue, cadmium plating, low alloy steel. 1. introduction bolts of starboard rear mounting trunion of aero-engine are generally made by low alloy steel. these are used in hardened and tempered condition wherein the material can be employed to withstand high strength at room / elevated temperatures with different loading conditions [1-3]. these bolts quite often fail by environmental induced embrittlements such as hydrogen embrittlement, stress corrosion cracking etc. present work is thus concerned with the failure investigation of the bolt of starboard rear mounting trunion of an aero-engine. the failed parts of the broken bolt were received for failure investigation. 2. experimental procedure the as-received failed parts were at first visually observed with the help of naked eye and magnifying glass. photographs were taken in as-received condition from various orientations and preserved for future reference during the course of analysis. stereo microscopic images of the fracture surfaces were taken afterwards. fracture surfaces from the as-received components were extracted delicately without damaging the same for further in-depth mailto:*mhazra@dmrl.drdo.in failure analysis of bolt of rear mounting trunion of an aero-engine: a case of bending induced chevron pattern…. 35 examination under scanning electron microscope (sem) equipped with electron dispersive spectroscopy (eds). the fracture surfaces were examined under sem after cleaning with acetone in an ultrasonic cleaner. subsequently, the failed surfaces were also cleaned in ultrasonic cleaner using branson liquid for removing oxide layers from the surface and to obtain representative fracture features. after the sem examination was over, representative cross-sectional sample extraction from failed parts was carried out for metallographic (optical and scanning electron microscopic) studies. examination was carried out in both un-etched and etched conditions. 3% nital was used as etchant. bulk compositional analysis of the samples was carried out by eds analysis. carbon, sulphur and hydrogen were analyzed by dry combustion technique. vickers hardness readings at 20 kg load were taken on metallographically polished samples. 3. results 3.1. visual examination the photographs (at various orientations) of failed parts in as-received condition are shown in fig. 1. marked pieces 1, 2 and 3 represent undamaged nut, bent and failed shank portion of the failed bolt along with failed and detached bolt head parts, respectively. bending is vividly revealed in bolt shank part (fig. 1 (a, d-f)). 3.2. fractography stereo microscopic images of the shank fracture surface are displayed in fig. 2. as-received surface is shown in fig. 2a, while fig. 2 (b-e) represents branson cleaned surface. various illuminating conditions and light intensities have been used with the fracture surfaces shown in fig. 2 (b-e) as deemed appropriate to reveal fracture features. points a and b appear to be two important fracture junctions with respect to initiation of the fracture surface under fatigue loading. point b initiates another crack front distinguished by typical chevron pattern. arrows in fig. 2 (b and d) indicate the propagation directions of the cracks. fig.1: photographs of as-received failed components. figure 2: stereo microscopic images of failed bolt shank part in various illuminating and cleaning conditions: (a) acetone and (b-e) branson cleaned conditions. hazra and singh (2021): international journal of engineering materials and manufacture, 6(1), 34-42 36 sem images of the shank fracture surface after acetone cleaning is exhibited in fig. 3, as taken from top of the fracture surface. right side plain region of the surface of fig. 3a corresponds to the region 1 in fig. 1, while the remaining rough region beside that one is region 2 in fig. 1. extensive rubbing has been noticed in both the regions (fig. 3(c and d)). quasi-cleavage fracture has been observed in region 2. cadmium has been found to exist in major area of region 2 (fig. 3 (a and b)). this has been confirmed by the eds analysis (fig. 4). the fracture surfaces of bolt head are displayed in fig. 5. magnified image of region a (region b in fig. 2) is displayed in fig. 5b. localized notch and few cracks seem to have been present along the periphery in this region. crack marked in fig. 5b is basically the same location of the bolt shank part as is the location a in fig. 2b. however, no corrosion pits and / or corrosion debris is found. rough region b displays the presence of cadmium (white patches in figs. 5c and 6), similar to that observed on the mating bolt shank fracture surface (figs. 3 (a and b) and 4). fig. 3: sem fractographs of failed bolt shank in acetone cleaned condition fig. 4: eds pattern taken from the point 1 in fig. 3. 1 failure analysis of bolt of rear mounting trunion of an aero-engine: a case of bending induced chevron pattern…. 37 fig. 5: sem fractographs of failed bolt head in acetone cleaned condition. fig. 6: high magnification images of region c (in fig. 5a) showing presence of tiny cadmium particles, (b) high magnification image of the region a (marked in (a)) and (c) eds pattern taken from tiny particles. high magnification image of apparently clean region c is presented in fig. 6. cadmium has been found to exist as tiny round particles even here. fig. 7 displays high magnification image of a typical area of region d in fig. 5 (region 1 in fig. 1c). the eds patterns are taken from various locations (1, 2, 3 and 4) and results are presented in fig. 7. cadmium has been found even in some areas of this region (especially location 1), while few other areas reveal the presence of corrosion debris (locations 3, 4 in form of fe-o) and base material (location 2). hazra and singh (2021): international journal of engineering materials and manufacture, 6(1), 34-42 38 3.4. metallography metallographic sample was extracted from the fracture surface along plane a-a in fig. 1b. un-etched optical microstructure of the sample shows the presence of cadmium coating, as confirmed by corresponding eds pattern (fig. 9a). fig. 9b exhibits the presence of oxides and few sulphide stringers. a well revealed crack and many other small cracks are found in the sample (fig. 9c). the microstructures in etched condition are presented in fig. 10. this clearly reflects the presence of banding (fig. 10a). high magnification micrographs show the presence of tempered martensite. many small cracks and crack like appearances are observed in the microstructure at periphery of fracture surface. fig. 7: high magnification images of region d in fig. 5a and (b-e) eds data taken from the locations 1, 2, 3 and 4. the fracture surface of failed bolt shank is shown in fig. 8 after branson cleaning. cadmium is not found in region 2 after this cleaning. this reveals the presence of micro-cracks throughout the rubbed fracture surface. fig. 8: sem fractographs of failed bolt head in branson cleaned condition. failure analysis of bolt of rear mounting trunion of an aero-engine: a case of bending induced chevron pattern…. 39 fig. 9: optical micrographs of the failed sample in un-etched condition: (a) presence of cadmium coating at the surface as supported by sem eds pattern, (b) oxides and sulphide stringers in microstructure and (c) cracks starting from the fracture surface. fig. 10: optical micrographs of the failed sample: (a) banding and (b-f) tempered martensite structure along with few peripheral cracks. etchant: 3% nital. hazra and singh (2021): international journal of engineering materials and manufacture, 6(1), 34-42 40 3.5. hardness an average hardness value for both the components is approximately 340 hv under 20 kg load. 3.6. chemical composition chemical compositions of the trace elements and bulk material are given in tables 1 and 2, respectively. it reveals the presence of c in medium range along with si, cr and ni as major alloying elements, while the base is fe. table 1: analyzed trace elements in the bolt material elements c s h composition, wt.% (standard deviation) 0.45 (0.01) 0.011 (0.002) 0.0007 (0.0001) table 2: analyzed major elements in the bolt material elements p ti al si mn cr mo fe composition, wt% (standard deviation) 0.0025 (0.0002 ) 0.002 (0.0002 ) 0.08 (0.002) 0.60 (0.002) 0.54 (0.01) 0.67 (0.02) 0.57 (0.04) bal. 4 discussions 4.1. fracture mechanism the fracture feature shows multiple initiation points such as a and b. two different fatigue crack fronts starting from points a and b have propagated towards each other. this is usually observed during a bending fatigue phenomenon. the crack fronts coincide with each other along line l-l. at the same time, another crack front of fast fracture with typical chevron pattern originated at point b and advanced in another (separate) direction. each of the above crack fronts seem to have proceeded independently, as is clear from the propagation paths [4, 5]. therefore, both the bending fatigue and fast fracture have contributed to the present failure independently, while the failure mechanisms are different to each other. interestingly, the contributions of both the failure mechanisms as described above appear to be approximately equal based on the area of fracture surface covered i.e. 50% each. 4.2. presence of cadmium: its source and implication cadmium is found on the whole fracture surface. however, its presence in larger amount was remarkable in plain region having chevron pattern as compared to that in bending fatigued region. this has been confirmed visually as well as under sem and also verified by the eds analysis. presence of larger amount of cadmium on the fast fracture region indicates that the intake of cadmium has occurred during and / or subsequent to the application of cadmium plating onto the component. it is important to mention here that the cracks are already present in component and these cracks have facilitated the access of cadmium inside the material. manifestation of these pre-existing cracks in the present case is in form of a fast fracture with chevron pattern. this is also supported by the presence of ample of secondary cracks observed on fractographs (figs. 2 and 8) as well as on metallographic samples (fig. 9) containing the fracture surface. 4.3. presence of corrosion: its possibility and contribution to two independent fracture mechanisms fast fracture region in acetone cleaned condition contains significant amount of cadmium and oxygen along with sulphur, chlorine, sodium, potassium and calcium (figs. 3 and 4). another location of the same fracture region contains cadmium and iron with significant amount of oxygen and small quantity of calcium (figs. 5 and 6). on the other hand, fatigued region is found to contain either almost pure cadmium or cadmium with oxygen (fig. 7). elements such as sulphur, chlorine, sodium, magnesium and calcium are often found to be there along with cadmium and oxygen. these findings indicate that the corrosion of cadmium plating may have happened, although the evidence of bolt corrosion is rather not sufficient. indication of corrosion of virgin bolt material is rarely typified by the presence of appreciable amount of fe in cadmium-oxygen rich products on the fracture surfaces [5]. therefore, it is possible that the corrosion of the cadmium plating has occurred and it has happened on the pre-existing fast fracture region. corroding fluid containing chlorine, sulphur and few above mentioned alkaline earth metals seems to have come in touch with the pre-cracked region. it is worth mentioning that all the said elements might have come from the various sources such as environment (like chlorine), rock salts (like sodium, calcium, magnesium etc.) present in a runway or in environment, aviation fuel residues and contaminants (like sulphur) [6-8], thus ruling out the possibility of corrosion. moreover, it is also to be noted that there no presence of mud-cracks indicating the corrosion was detected in the present case. however, enrichment of oxygen along with iron on few locations on the fracture surface points out to the presence of corrosion, how insignificant it may be. failure analysis of bolt of rear mounting trunion of an aero-engine: a case of bending induced chevron pattern…. 41 on the other hand, rare presence of oxygen-rich products on fatigued region indicates that corrosion did not happen in that region. however, it is possible that the corrosion debris of fast fracture region got entered into the fatigued region by some means, subsequent to the failure of fatigued region. it is quite obvious, based on these evidences that the corrosion did not occur on the cadmium plated bolt surface causing its failure. thus, corrosion did not contribute at all to the present failure. it is rather a post-cracking event in the fast fracture region and did not contribute to the bending fatigue failure of the remaining cross-section directly. however, there is a finite chance of the said corrosion to have induced the reversed bending fatigue cracking phenomenon at point b (fig. 2b). nevertheless, there is no trace of corrosion debris, although a crack is found (fig. 5b), similar to that is observed at location a also. this is further corroborated by the presence of numerous cracks on the fracture surfaces as well as on metallographically polished samples. 4.4. presence of bending type of service load existence of bending type of load is well proved considering: (i) visually observed bending of the failed component, (ii) presence of bending fatigue on the fracture surface and (iii) presence of chevron pattern. 4.5. construction material: its identity and suitability material looks to be a chromium-molybdenum grade steel closely matching to that of astm grade 16 governed by the specification a194/a194m [2, 3]. the as-desired hardness range for this material has been specified to be 250330 hv. however, the obtained hardness value of 340 hv in the present case is significantly higher than the asdesired one. this raises the suitability of the material in its current form. it may be noted that there are multiple initiation sites of the fracture surface. also, there are secondary cracks in each of the initiation sites (as indicated in area a, figs. 2d and 5b). interestingly, cracks are found even on the section with fracture surface having chevron mark. there are ample of such evidences wherein secondary cracks are observed on branson cleaned (virgin) fracture surface (fig. 8), thus ruling out the possibility of mud-cracking or cracks present on cadmium-coated surface. the secondary cracks are also observed on the metallographic samples taken across the fracture surface. in other words, material seems to be in a high-hardened (than the as-specified and desired) or embrittled state due to improper heat treatment or any other processing step. a schematic of the probable causes of failure of the bolt is presented in figure 11. this guides and explains the thought process involved in reaching to the conclusion in the present case [5]. this looks to be a case of material failure arising out of the interior and / or surface defects due to the embrittling effect coming from the associated processes employed for manufacturing the component. the non-suitability of the presently used material is quite well proven here through observation of the obtained hardness values, as mentioned earlier. all other possibilities (as presented in fig. 11) are initially listed and rule out one by one and finally conclusion is arrived based on the visual and microscopic observations and very importantly, supported by the background information received from the user. 5. conclusions the following conclusions can be drawn from the present investigation: 1. bolt has failed by a combined action of bending induced fast fracture and fatigue phenomena. these are two independent phenomena and each covers approximately 50% of the fractured area. 2. pre-existing cracks have initiated the present failure, firstly as chevron mark followed by inducing bending fatigue. 3. brittleness of the construction material has resulted in the present failure. 4. cracks of considerable dimensions are present in the material prior to the introduction of cadmium plating and chevron mark is immediate manifestation. acknowledgement the authors are grateful to the drdo for funding the present work. they are also thankful to dr. g madhusudhan reddy, outstanding scientist and director of dmrl for his constant encouragement to work on the present field. reference 1. steel fasteners for the temperature range between -50oc and +150oc, https://www.wuerth-industrie.com, last accessed on 20.01.2021. 2. astm a – 194: standard specification for carbon and alloy steel nuts for bolts for high-pressure and hightemperature service, last accessed on 20.01.2021. 3. astm a – 320: standard specification for alloy steel and stainless steel bolting materials for low temperature service, last accessed on 20.01.2021. 4. metal fatigue: theory and design, ed. a. f. madayag, pp. 3-5, 1968. 5. asm metals handbook vol 11: failure analysis and prevention, edited by w. t. becker and r. j. shipley, asm international, 2002, metals park, ohio. https://www.wuerth-industrie.com/ hazra and singh (2021): international journal of engineering materials and manufacture, 6(1), 34-42 42 6. pszenny. a. a. p., keene. w. c., jacob. d. j., fan. s., maben. j. r., zetwo. m. p., springer-young. m., and galloway. j. n., evidence of inorganic chlorine gases other than hydrogen chloride in marine surface air, geophysical research letter, 20(8) 1993, pp. 699-702. 7. titler, r. v., chemical analysis of major constituents and trace contaminants of rock salt, rock salt paper final 052711.pdf, last accessed on 20.01.2021. 8. groysman, a., corrosion in systems for storage and transportation of petroleum products, nace – international corrosion conference series 2015, springer. figure 11: proposed schematic sequential representation of the probable causes of failure of the bolt facilitating to arrive at conclusion in present failure analysis case (bold captions indicate the concluded most probable cause(s)). international journal of engineering materials and manufacture (2018) 3(2) 98-104 https://doi.org/10.26776/ijemm.03.02.2018.04 m. h. hasan 1 , s. ahmed 2 , r. voldman 3 and m. mehany 4 1,3,4 department of mechanical and industrial engineering ryerson university, canada 2 department of robotics and mechatronics engineering university of dhaka, dhaka 1000, bangladesh 1 e-mail: hasibulhasan@ryerson.ca, 2 e-mail: shugataahmed.rme@du.ac.bd 3 e-mail: rvoldman@ryerson.ca, 4 e-mail: mirt.mehany@ryerson.ca reference: hasan, m. h., ahmed, s., voldman, r. and mehany, m. (2018). parametric effect on surface finish of three-dimensional printed object. international journal of engineering materials and manufacture, 3(2), 98-104. parametric effect on surface finish of three-dimensional printed object muhammad hasibul hasan, shugata ahmed, ron voldman and mirt mehany received: 20 april 2018 accepted: 29 may 2018 published: 30 june 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract the ability to use different parameters and finishing techniques in fused deposition modelling (fdm) depends largely on part geometries, materials, printing processes like z-resolution and post processing to some extent. low quality poor surface finish due to layer ovality, improper z-resolution parameter selection and fill of the empty shell in threedimensional (3d) printing, results unexpected texture and appearance. an investigation is carried out on the effects of z-resolution (0.15 mm to 0.40 mm) and fill parameters on flat and curved surface objects manufactured using the fdm process. moreover, post surface treatment was performed using acetone. it was found that average surface roughness increases with increasing z-resolution. solid fill can create a smoother surface as oppose to sparse fill. surface roughness improves significantly after post treatment with organic solvent acetone. keywords: fused deposition modelling, 3d printing, zresolution, surface roughness 1 introduction three-dimensional (3d) printers are used to fabricate rapid prototypes (rp) for research and analysis purposes. besides rapid prototyping, 3d printing is also used for rapid manufacturing — a new manufacturing technique where 3d printers are used for short run custom manufacturing. in this method, printed objects are not prototypes but actual end user products. the basic principle of fused deposition modelling (fdm), 3d printing or additive manufacturing is to manufacture a prototype layer-by-layer at which most of the printing parameters can be adjusted. surface finish is a major concern in fdm process, and as better surface finish is highly recommended for rapid prototypes and rapid manufacturing products, a large number of research has been carried out on it. in fdm, surface finish can be improved by three methods z resolution, fill of filament and post treatment. the literature has revealed that fill parameter affects the surface finish — fill is the material used to fill the empty space inside the shell of an object. therefore, in order to achieve a better surface finish, the correct type of fill should be used, and choosing a fill pattern depends on the kind of model, desired structural strength and printing speed. a parametric study on the fabrication of a specimen using the fdm 3000 3d printer was conducted by galantucci et al. (2015) the specimen material in use were abs resins and pla, in which specimens were fabricated by the hot extrusion technique and the objective was to improve the specimen’s dimensional accuracy. optimized parameters were determined by the factorial analysis design of the experiment (doe). however, it was observed that after depositing the material, shrinkage occurred due to the large temperature difference (217˚c) between deposited material and deposition platform. for this reason, a deviation from ideal dimensions was observed. guerrero-de-mier et al. (2015) focused on reducing warping and deformation due to internal stress occurring in fdm. for experimental purposes, hexagonal and square shape bricks were used as test parts. a g code was developed to fabricate the brick stacks, which were locked spatially. authors suggested that warping can be reduced by limiting stacking section length. akande (2015) claimed that low layer thickness, low speed of depositions and low fill density are the optimal parameters to have for a better surface roughness. khan et al. (2006) investigated the emphasis of slice thickness and support parameters on surface roughness — they mentioned that lower slice thickness produces hasan et al. (2018): international journal of engineering materials and manufacture, 3(2), 98-104 99 better surface finish. bakar et al. (2010) found optimal parameters for dimensional accuracy, better surface finish and reduced post-processing time. according to galantucci et al. (2009), chemical treatment is fast, cheap, and easy to use, which significantly improves surface finish. in their study, percoco et al. (2012) investigated the effect of chemical treatment on compressive strength and surface roughness of fdm parts. for their chemical treatment, they used a solution composed of 90% dimethyl ketone and 10% water, and they had found that the compressive strength of the parts was improved in this method. researchers concluded that the proposed finishing treatment can be used with immersion time up to 300 sec to reduce roughness up to 90%, which in addition to compressive strength, improves mechanical properties as well. vargas-alfredo et al. (2018) suggested that surface topography and chemical composition in a 3d printed porous object can be improved by immersing the object in polystyrene solution (ps). fused deposition modelling (fdm) technique was utilized to fabricate the 3d parts with different shapes (screws, honeycombs, tubes and scaffolds). 400 nm to 3 μm size pores were created on the surface of the 3d objects by immersing them in the ps solution — this method is known as the breath figures approach. temperature, relative humidity and polymer concentration of the solution and time of immersion have significant effects on the pore size, for when the object was immersed in the solution for 1s, 1.7 ± 0.4 μm pores were created. for 3s and 5s immersion times, 1.9 ± 0.5 μm and 2.4 ± 0.4 μm pores were created on the surface, respectively. bf method was used for chemical modification. rao et al. (2012) discussed that the surface finish of fdm parts can be improved by interacting the surface with vapours of tetrahydrofuran. in this process, the part to be smoothed out is placed on a non-soluble support inside a closed vessel with a non-air-tight lid. heat is then applied to evaporate the tetrahydrofuran so that it can interact with the object's surface to make it smooth. ahn et al. (2004) performed post processing to increase optical transmissivity by applying elevated temperatures and by providing resin infiltration and surface sanding. pandey et al. (2003) examined the use of hot cutter machining to improve surface finish of fdm parts and it was concluded that the proposed machining method was able to produce the surface finish of 0.3 microns, which can be used to obtain a better surface finish of an fdm part. sanatgar et al. (2017) carried out an investigation on 3d printing by deposition of polymers on synthetic fabrics. fused deposition modelling (fdm) technique was used for adhesion. effect of 3d printing process parameters such as extruder temperature, platform temperature and printing speed on the adhesion process were all investigated. it was found that effect of the extruder temperature on adhesion is linear. however, linear effect of platform temperature on adhesion process was insignificant. effect of fabric and filler type on adhesion has been found to be significant. the purpose of this study was to investigate how to improve surface finish of fdm 3d printing by focusing on fill and z-resolution parameters. surface finish was also examined after post treatment by acetone. 2 experiment the up plus 3d printer with up plus software was used to print the specimens and acrylonitrile butadiene styrene (abs) was used as the object material. printed samples are shown in figure 1 and different surfaces of a sample are shown in figure 2. z-resolution were maintained between 0.15 mm to 0.40 mm even though the smallest particle height 0.10 mm or 100 microns could be achieved. the stepper motor of the printer can move the platform by as little as 100 microns, however fdm extruders cannot control the flow of filament precisely enough to produce clean results. for this reason, low micron prints on fdm machines often end up looking worse than high micron prints even though the individual layers may be finer. the modelling envelope temperature is regulated to aid in the bonding process. the fdm head deposits material as it follows the part geometry that has been constructed from bottom and builds up the model to the top in solidworks 2013. starting from the stl file, the geometry of a part can be read by the up plus software. objects are printed for different z-resolutions and fills. various z-resolutions and fills with relevant sample numbers are mentioned in table 1, and after printing, ra values were measured by surface measuring instrument surftest sv.500 of mitutoyo. images of surface texture on specimens were captured by a metallurgical microscope nikon epiphot 200 and a sample image is given in figure 3. post treatment was carried out to improve the surface finish of the specimen using acetone. the specimen was placed on a non-soluble support of aluminium foil raft inside a closed vessel with a non-air-tight lid. heat was applied to evaporate the acetone for 15 to 20 minutes, so that it can interact with the object’s surface to make the surface smooth. after post treatment, ra values were measured again. in 3d printing, using thinner layers has few to no advantages and only serves to increase print time. thinner layers are most useful for improving the surface finish on parts that have diagonal or curved surfaces, such as surface 2 in the study (figure 2b.) figure 1: the printed samples (a) (b) parametric effect on surface finish of three-dimensional printed object 100 table 1: types of fill and z-resolution parameters applied on samples no. of samples z-resolution (mm) fill 1 0.15 solid 2 0.40 solid 3 0.15 sparse 4 0.40 sparse 5 0.15 sparse 6 0.40 sparse figure 2: the view for surface 1 (a), surface 2 (b) and surface 3 (c) used in this study figure 3: an image of the flat surface for sample 1 taken by microscope with magnification factor of 50x 3 results and discussions average surface roughness was calculated for all six samples on their three different surfaces and two filling methods, as shown in the table 2. from the table 2, it can be seen that sample 1 had the lowest value of average surface roughness for surface 1, 2 and 3, which were 12.46 µm, 12.27 µm and 7.10 µm, respectively. meanwhile, sample 4 had the highest value, which were 31.43 µm, 28.49 µm, and the third surface was out of range due to the higher value of surface roughness. sample 3 had a lower value of surface roughness for surface 1 and 2 compared to sample 2, which were 15.85 µm and 12.38 µm, respectively. however, sample 2 had a lower value for surface 3 of 24.62 µm compared to sample 3, which was 36.52 µm. hence, it is inferred that sample 1 had a better surface finish than (a) (b) (c) hasan et al. (2018): international journal of engineering materials and manufacture, 3(2), 98-104 101 other samples as it possessed the lowest average surface roughness values. it is interesting to note that a solid fill with higher z-resolution produces a somewhat better surface finish despite a higher printing time. figure 4 shows the rising trend of the average surface roughness value with the increment of z-resolution. from the figure, it is observed that surface 3 had the lowest value of average surface roughness (7.10 µm) for a 0.15 mm z-resolution. on the other hand, surface 1 had the highest surface roughness value of 31.54 µm for a 0.4 mm zresolution. in comparison, surface 3 had a better surface finish than other two surfaces for solid fill parameter since it has the lowest roughness value for 0.15 mm and 0.275 mm of z-resolutions. however, for a 0.4 mm z-resolution, surface 2 had the lowest average surface roughness of 24.52 µm. table 2: the value of surface roughness for each surfaces of each samples ra value (µm) average ra value (µm) sample no. surface no. 1 2 3 1 12.40 12.67 12.31 12.46 1 2 12.20 12.39 12.23 12.27 3 7.11 7.11 7.09 7.10 1 31.55 31.54 31.52 31.54 2 2 24.53 24.51 24.51 24.52 3 24.62 24.63 24.61 24.62 1 15.85 15.86 15.84 15.85 3 2 12.41 12.39 12.35 12.38 3 36.44 36.63 36.49 36.52 1 31.39 31.46 31.44 31.43 4 2 28.52 28.46 28.48 28.49 3 out of range 1 15.65 16.66 15.68 16.00 5 2 12.53 12.50 12.48 12.50 3 36.42 36.48 36.45 36.45 1 1.56 1.69 1.57 1.61 6 2 0.84 0.92 0.90 0.89 3 out of range figure 4: the ra value depending on z-resolution of two solid fill samples 0 5 10 15 20 25 30 35 0 0 . 0 5 0 . 1 0 . 1 5 0 . 2 0 . 2 5 0 . 3 0 . 3 5 0 . 4 0 . 4 5 a v e r a g e r o u g h n e s s ( 𝜇 𝑚 ) z-resolution(𝑚𝑚) surface 1 surface 2 surface 3 parametric effect on surface finish of three-dimensional printed object 102 similarly, for sparse fill, better surface finish was found for surface 2 in figure 5. on the other hand, surface 3 showed the highest average roughness for sparse fill. as the z-resolution increased from 0.15 mm to 0.45 mm, the surface roughness increased relatively linearly reducing the 3d printing time for sparse fill samples. figure 6 shows the trend of average surface roughness with changing fill parameters. from the figure, it can be seen that the average roughness value for surface 2 and 3 increased as it went from solid to sparse fill parameter. however, there was no value for average roughness of surface 3 with sparse fill parameter, as the reading was out of range. meanwhile, surface 1 displayed a slightly downward trend when the sample was filled with the sparse fill parameter. nevertheless, its average surface roughness was the highest between the other two surfaces. figure 5: the ra value depending on z-resolution of two sparse fill samples figure 6: the ra value depending on fill parameter of two 0.40 mm z-resolution samples 0 5 10 15 20 25 30 35 40 45 0 0 . 0 5 0 . 1 0 . 1 5 0 . 2 0 . 2 5 0 . 3 0 . 3 5 0 . 4 0 . 4 5 a v e r a g e r o g h n e s s ( 𝜇 𝑚 ) z-resolution (𝑚𝑚) surface 1 surface 2 surface 3 0 5 10 15 20 25 30 35 0 0 . 5 1 1 . 5 2 2 . 5 3 3 . 5 a v e r a g e r e s o l u t io n ( 𝜇 𝑚 ) fill parameter surface 1 surface 2 surface 3 hasan et al. (2018): international journal of engineering materials and manufacture, 3(2), 98-104 103 figure 7: comparison of surface roughness between untreated sample and sample after post treatment in figure 7, it is observed that surface roughness of surface 1 and surface 2 of sample 4 were 31.43 µm and 28.49 µm, respectively, before post treatment. however, after post treatment the lowest values of surface roughness for both surfaces were achieved. this result supports a study conducted by lalehpour et al. where it was experimentally proved that chemical finishing processes in fdm, can meet the conditions of a functional and adequate finishing process, as it improves the roughness without negatively affecting the mechanical or geometrical properties of the treated parts. [13]. lalehpour et al. (2018) showed that the maximum reduction percentage of the surface roughness due to the treatment reaches 95% and no effect was observed on the build orientation, dimensional accuracy and dimensional deviation. 4 conclusions the carried out experiment studies the effect of different parameters on surface roughness of 3d printed objects manufactured by the fdm process. the following key factors are determined from the experimental results: 1. average surface roughness is high for higher values of z-resolution for a flat surface. for a curved surface, the z-resolution effect is more pronounced. it is recommended to use a higher resolution or a lower z value for better curved surfaces at the expense of a longer printing time. 2. solid fill is better than sparse fill for generating smoother surfaces, even though more materials would be consumed in making the sample heavy. 3. smoother surface was developed after post treatment by organic compound acetone, which can meet the conditions of a functional and adequate finishing process, as it improves the roughness without affecting the mechanical or geometrical properties of the treated parts. no effect was observed on the build orientation, dimensional accuracy and dimensional deviation. references 1. guerrero-de-mier, a., espinosa, m. m., & domínguez, m. (2015). bricking: a new slicing method to reduce warping. procedia engineering, 132, 126-131. 2. galantucci, l. m., bodi, i., kacani, j., & lavecchia, f. (2015). analysis of dimensional performance for a 3d open-source printer based on fused deposition modeling technique. procedia cirp, 28, 82-87. 3. akande, s. o. (2015). dimensional accuracy and surface finish optimization of fused deposition modeling parts using desirability function analysis. international journal of engineering research & technology, 4(4), 196-202. 4. khan, s. f., salleh a. f, sharif, s., zulkepli m., zulkifli, a. r., & nasir, m. m. (2006) a preliminary study on fdm prototype surface roughness. proceeding of malaysian technical universities conference engineering and technology, mucet. 0 5 10 15 20 25 30 35 s a m p l e 4 p o s t t r e a t m e n t a v e r a g e r o u g h n e s s ( 𝜇 𝑚 ) type of sample surface 1 surface 2 surface 3 parametric effect on surface finish of three-dimensional printed object 104 5. bakar, n.s.a., alkahari, m.r. & boejang, h. (2010). analysis on fused deposition modelling performance. journal of zhejiang university-science a (applied physics & engineering), 11-12, 972-977. 6. galantucci, l.m., lavecchia, f. & percoco, g. (2009). experimental study aiming to enhance the surface finish of fused deposition modeled parts. cirp annals – manufacturing technology, 58(1), 189–192. 7. percoco, g., lavecchia, f. & galantucci, l. m. (2012). compressive properties of fdm rapid prototypes treated with a low cost chemical finishing. research journal of applied sciences, engineering and technology, 19(4), 3838-3842. 8. vargas-alfredo, n., reinecke, h., gallardo, a., del campo, a., & rodríguez-hernández, j. (2018). fabrication of 3d printed objects with controlled surface chemistry and topography. european polymer journal, 98, 21-27. 9. rao, a.s., dharap, m.a.,venkatesh, j.v.l. & ojha, d. (2012). investigation of post processing techniques to reduce the surface roughness of fused deposition modeled parts. international journal of mechanical engineering and technology, 3(3), 531-544. 10. ahn, s., lee, c., & jeong, w. (2004). development of translucent fdm parts by post-processing. rapid prototyping journal, 10 (4), 218-224. 11. pandey, p. m., reddy, n. v. & dhande, s. g.(2003). improvement of surface finish by staircase machining in fused deposition modelling. journal of materials processing technology, 132, 323-331. 12. sanatgar, r. h., campagne, c., & nierstrasz, v. (2017). investigation of the adhesion properties of direct 3d printing of polymers and nanocomposites on textiles: effect of fdm printing process parameters. applied surface science, 403, 551-563. 13. gajdos, i., spisak, e., kascak, l., & krasinskyi, v. (2015). surface finish techniques for fdm parts. materials science forum, 818, 45-48. doi: https://doi.org/10.4028/www.scientific.net/msf.818.45. international journal of engineering materials and manufacture (2020) 5(4) 116-129 https://doi.org/10.26776/ijemm.05.04.2020.02 sabrina n. saiphoo 1 , cassidy m. rose 1 , alexander t. dunn 1 , dwji j. padia 1 and muhammad h. hasan 2 1 department of electrical, computer, and biomedical engineering 2 departmenty of mechanical and industrial engineering ryerson university, canada email: hasibulhasan@ryerson.ca reference: saiphoo, s. n., rose, c. m., dunn, a. t., padia, d. j., hasan, m. h. (2020). comparison of four common gold nanoparticles for photothermal cancer therapy: a review. international journal of engineering materials and manufacture, 5(4), 116-129. comparison of four common gold nanoparticles for photothermal cancer therapy: a review sabrina n. saiphoo, cassidy m. rose, alexander t. dunn, dwji j. padia and muhammad h. hasan received: 28 may 2020 accepted: 23 august 2020 published: 20 october 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 abstract current cancer treatment options, including surgery, chemotherapy and radiation therapy, often cause damage to healthy tissue and reduce a patient's quality of life with well-known side effects, such as pain, infection and nerve damage. recent research has shown that gold nanoparticles used as photothermal agents in photothermal therapy may pose as an alternative to traditional treatments. this great potential is due to their ability to selectively accumulate in cancerous tissue, efficiently absorb near-infrared light, and kill cancerous tissue without harming surrounding cells. gold nanoparticles show promise in increasing treatment efficacy and reducing the side effects associated with cancer therapy. while recent studies show the potential of gold nanoparticles, the existing literature is limited in drawing comparisons between studies and practical use for photothermal therapy. this paper reviews notable studies on four common gold nanoparticles used in the therapeutic treatment of cancer: gold nanocages, gold nanospheres, gold nanorods, and gold nanoshells. by comparing key characteristics of the particles’, including their synthesis, toxicity, absorption spectrum, and selective photothermal lethality, gold nanospheres can be recommended for use in photothermal therapy. although forms of each gold nanoparticle were found to have a low toxicity, gold nanospheres can be rapidly synthesized and appear to exceed in selective photothermal lethality and immature tumour accumulation. due to these advantages in using gold nanospheres for photothermal therapy, cancer could be treated more effectively and improve patient prognosis. keywords: gold nanoparticles, cancer therapy, photothermal agents, photothermal therapy, near infrared radiation, nanorods, nanoshells, nanocages, nanospheres, hyperthermia 1 introduction cancer is the leading cause of death in canada with 1 in 4 cases being fatal [1]. in 2020, 225,800 people in canada are expected to be diagnosed with cancer [2]. cancer also places a large burden on the patient and a financial strain on the country [3]. in 2008, the estimated total cost of cancer in canada was $4.4 billion [3]. cancer’s mortality rate is decreasing due to advancements in the medical field, but remains high globally [4]. this is largely caused by the damage cancer causes to healthy tissue and the large strain placed on the body during conventional treatment [5]. current cancer treatments include surgery, chemotherapy, radiotherapy, gene therapy, hormonal therapy, immunotherapy, and hyperthermia [6, 7]. these treatments can have a wide range of side effects, including pain, fatigue, and nausea [8]. traditional treatments like chemotherapy and radiation therapy cause damage to noncancerous, rapidly-dividing cells [6]. radiation therapy also causes cell death or halts cell division by inducing dna damage using ionizing radiation [9]. a major disadvantage of these treatment methods lies in the fact that they are non-specific, causing healthy, normal cells to be damaged [6]. recently, extensive research has been conducted concerning the application of nanoparticles (nps) as they have shown promise in both drug-targeting and hyperthermia treatments [10, 11, 12]. according to the international union of pure and applied chemistry (iupac), nps are microscopic particles that have dimensions ranging between 1 and 100 nm [13, 14]. the use of nps in cancer treatments has shown the potential to increase the localization and targeting saiphoo et al., (2020): international journal of engineering materials and manufacture, 5(4), 116-129 117 abilities of current treatments [15]. this can be accomplished by using nps as a photothermal agent (pta) in targeted hyperthermia [16, 10]. hyperthermia is a non-invasive cancer therapy where malignant cells are exposed to localized heat greater than 43 °c [17, 18, 19]. conventional hyperthermia can cause damage to surrounding tissues, burns, pain at the target site, blood clots, infection, and swelling [20, 21]. for this reason, a promising method to achieve hyperthermia is using ptas that accumulate selectively in tumour tissue and cause heating in a localized area when exposed to electromagnetic radiation of a certain frequency [16, 22]. this process is known as photothermal therapy (ptt) [17, 41]. the selective accumulation of nps in tumours is possible due to their poorly formed vasculature, which is more permeable than that of normal tissue [10]. metallic nps can strongly absorb and scatter specific wavelengths of light and the resulting resonant energy is converted to heat [23]. ptt typically uses near-infrared (nir) radiation since it offers a low attenuation in tissue, allowing for energy penetration into deep tissues [10, 24]. using nir radiation also causes minimal thermal damage to healthy tissue [10, 12]. due to the high absorption of gold nanoparticles (aunps) in the nir range and their ability to rapidly heat under irradiation, their potential use in ptt is an active area of research [21, 25, 26]. the absorption peaks of these aunps in specific regions of the electromagnetic spectrum are due to the localized surface plasmon resonance (lspr) [22, 25]. since aunps are conductive and smaller than visible light wavelengths, the electric field from electromagnetic radiation can excite electrons of a conduction band [22]. the result is localized plasmon oscillations, whose resonant frequency depends on the geometry and size of the aunp [22]. this resonance generates the heat observed during ptt [22]. aunps have properties unique from other materials being studied for use in cancer treatment applications, such as iron-, polymer-, and lipid-based nps [13]. they have been shown to have adjustable properties, including the ability to optimize the relative proportions of light scattering and absorption based on the application [10]. aunps are also unique in being able to retain their optical properties within the body for a long time [21]. aunps are injected into the body and passively accumulate in tumours before the nir laser is used to excite the particles and generate internal heating [23]. the biological effects of this localized increase in temperature include the nucleation and growth of bubbles on tumour tissues and denaturation in cells [11]. when these growing bubbles rupture, they can then apply mechanical stress to the target cells and cause damage [11]. when comparing different ptas for use in ptt, it is important to consider a few key characteristics and properties. firstly, the toxicity of nps should be low because, otherwise, they may kill healthy cells and cause permanent damage [27]. the particle must also selectively accumulate in the target tissue and efficiently heat under electromagnetic radiation [15, 10]. another key factor is the size of nps since this may affect tissue accumulation and uptake by cancerous cells [10]. tumour vasculature can have varying sizes of fenestrations based on age and, therefore, a smaller particle size might be required for accumulation in early-stage tumour tissue [10]. the absorption spectrum of the particles is also important in determining the functionality of a pta [10]. the absorption peak should lie in the nir region to ensure sufficient tissue penetration and energy absorption can occur during ptt [10, 28]. this paper will compare common aunps for use in ptt with a nir laser. the nps being compared will be gold nanocages (auncs), gold nanorods (aunrs), gold nanospheres (aunss), and gold nanoshells (aunshs). by reviewing notable studies on the aforementioned parameters, an ideal aunp will be selected for use in ptt with the goal of informing and focusing the scope of future research efforts. 3 gold nanocages auncs are a specific morphology of aunp that are widely studied for use in ptt [29, 30]. in 1989, studies performed on aunps to test their effectiveness for ptt found that auncs had promising multi-functionalization and encapsulation abilities [31]. this means their surfaces could be easily modified to achieve enhanced tumour-specific tissue accumulation [31]. auncs act as photothermal transducers, their large surface area converts light into heat [29, 32]. auncs are used because of their high photothermal efficiency, low toxicity, high tissue accumulation, and high cell killing efficiency [29, 33]. this section will review several studies to evaluate the ptt efficacy of auncs. 3.1. synthesis chen and colleagues [29] described how uncoated auncs are synthesized by a simple galvanic replacement reaction between silver nanocubes and haucl4 [29]. galvanic replacement reactions are redox reactions between solid metal ag nanocubes and au ions from haucl4 [29]. this process synthesizes the uncoated aunc structure, giving it certain intrinsic properties, such as the lspr peak of roughly 800 nm, edge length of 47 nm, and diameter of 99 nm found in this study [29]. the characteristics of auncs can be further modified by changing the surface coating [29]. the surface coating also allows for specific tumour cell targeting and can change the efficiency of the photothermal treatment [29]. the nanocage surface can then be covered with a coating of heterofunctional polyethylene glycol (peg) with a sulfhydryl group at one end and a methoxy group at the other [29]. this gave rise to new dimensions, where the edge length was 48 nm and the diameter was 92.2 nm [29]. jenkins and colleagues [33] described a similar method for synthesizing auncs, however, they used a different surface coating for their experiments [33]. the auncs were coated with polydopamine (pda), creating polydopamine-coated auncs (aunc@pda) and then further conjugated with anginex to synthesize aunc@pdacomparison of four common gold nanoparticles for photothermal cancer therapy: a review 118 ax [33]. this coating of the auncs altered their dimensions and absorption properties [33]. the edge length produced in this experiment was 45.6 nm and the hydrodynamic diameter was 132 nm [33]. the lspr peak was also slightly lower than that in the study by chen et al. [29] at 794 nm [33]. 3.2. toxicity according to jenkins et al. [33] the toxicity of a aunp has more to do with its coating and size, rather than shape [33]. jenkins et al. [33] studied the bodies of test mice post-irradiation to assess the biodistribution and tissue concentration of the aunc@pda and aunc@pda-ax [33]. they found relatively high concentrations of aunc in the liver and spleen and low concentrations in the kidneys [33]. this was expected due to the size of the auncs being much larger than the renal filtration limit, preventing them from entering the kidneys [33]. a high distribution of aunc@pda-ax was found in the lungs of the mice, but aunc@pda was found in a much lower percentage [33]. this is interesting because it indicates the specific coatings of auncs can change the distribution of auncs, affecting the degree of toxicity in specific organs [33]. jenkins et al. [33] concluded that bare, uncoated auncs are completely non-toxic and the pda-ax surface coating is entirely responsible for any toxicity exhibited [33]. 3.3. selective photothermal-induced cell death a key factor in the effectiveness of auncs in ptt is their ability to passively accumulate at the tumour site, while minimally affecting healthy cells [29]. in a study by chen and colleagues [29], this was tested by harvesting the tumours and organs of the mice injected with auncs 96 hr after ptt and using inductively-coupled plasma mass spectrometry (icp‐ms) to analyse the accumulation of auncs [29]. chen and coworkers [29] found that the ncswere essentially completely cleared from the blood and muscle tissue with respective concentrations of 0.04 ± 0.03 %id/g and 0.80  ±  0.12 %id/g (percent initial dose per gram of tissue) after 96 hr [29]. the passive accumulation at the tumour site was efficient with a particle concentration of 5.7 %id/g [29]. upon qualitative observation, the entire surface of the tumour was almost fully covered with auncs [29]. the three-dimensional spatial distribution of the ncswas examined by cutting the tumour into small pieces and each piece was weighed and analysed using icp-ms [29]. as seen in figure 1, the edges had the highest concentration of ncs, while the centre had the lowest concentration, with a linear change in concentration between these areas [29]. this is due to the intravenous nature of the nanocage injection, as most tumour blood vessels are on its surface [29]. the ncs were observed to penetrate the leaky blood vessels of the tumour over time, allowing for uniform heat generation during ptt [26, 29]. the results of jenkins and colleagues [33] experiment agree with those of chen and coworkers [29], as the aunc@pda had a tumour accumulation of 22 particles/g and aunc@pda-ax had an even better accumulation of 65 particles/g [33]. figure 1: (a) biodistribution of the aunc in various organs (b) distribution of the aunc within the tumour layers, where e is edge and c is center [29]. chen and colleagues [29] tested the selective destruction of tumourous tissue using auncs by injecting 10 mice with cancer cells (u87wtegfr) subcutaneously in their right and left ear flanks [29]. the mice were then divided into two even groups of five once the implanted tumours had grown to a volume of 200-400 mm 3 [29]. the first group received 100 µl of 9 × 1012 particle/ml pegylated auncs in a phosphate-buffered saline (pbs) solution, while the second group only received an equal volume of saline, both through intravenous injections [29]. the mice were left for 72 hr before beginning ptt [29]. both group’s right ear flanks were subjected to a steady beam 808 nm diode laser at a power density of 0.7 w/cm 2 for 10 min [29]. chen and coworkers [29] noted the group with the aunc injections had a maximum temperature reading of 54 °c, while the saline-injected group’s temperature never passed the 37 °c mark [29]. 24 hr post-irradiation, it was observed that in the group that underwent the auncs treatment, the metabolism of 70% of the tumour cells was saiphoo et al., (2020): international journal of engineering materials and manufacture, 5(4), 116-129 119 halted, effectively rendering them deceased with minimal damage to healthy cells [29]. upon histological examination by electron microscopy, there was evidence of coagulative necrosis (cell death), an abundance of destroyed chromatin fragments throughout the cytoplasm (karyorrhectic debris), and considerable regions of karyolysis (destruction of the nucleus) [29]. 4 gold nanospheres aunss are solid gold nps with a spherical shape and are among the smaller of the aunps being studied for applications in hyperthermia [10]. their absorption peak lies near 530 nm in the visible light region but can be shifted to the nir region by clustering aunss together within or outside of target cells [10, 34]. they have also been studied separately for applications in diagnostic imaging and used in vivo as a radiotracer [10, 35, 36, 37]. as one of the older forms of aunps, many studies showed their potential in ptt were performed in the early 2000s [10]. pitsillides et al. [38] first proposed a method that used aunps to achieve selective cell killing using laser pulses to irradiate cells that had been incubated with antibody conjugated 20 and 30 nm aunss [21]. using this method, energy was selectively delivered to aunss, causing microscopic cellular damage, high localized peak temperatures, and cell death [38]. this study has been built upon in more recent work [21, 10], which will be explored in this section to evaluate auns’s potential efficacy in ptt. 4.1. synthesis compared to other aunps, aunss are relatively simple to synthesize [10]. typically, aunss are produced using a citrate-mediated reduction of chloroauric acid (haucl4) [24, 25, 39]. in a study by chen and coworkers [40], haucl4 (1 ml, 0.25 mm) was added to h2o (90 ml), then stirred at 25 °c 1 min. next sodium citrate (2 ml, 38.8 mm) was added to this solution, which was then stirred for an additional minute before adding nabh4 (0.6 ml, 0.1 m). the reaction mixture was stirred at 0-4 °c for 5-10 min, depending on the desired size. to vary the diameters of the aunss between 3 to 100 nm, the volume of seed colloid (haucl4) added was also varied [40]. a simple, energyefficient, and rapid synthesis method using microwave heating has also been used by liu and coworkers [39]. this method appears promising for the large-scale production of npsthat would be required for the widespread application of aunss in healthcare [39]. 4.2. toxicity the safety of using aunss in the human body is well-known through decades of their use as a radiotracer and gold can remain within cells without reacting for long periods of time [35, 36, 37, 38]. however, chen and coworkers further evaluated the toxicity of aunss over time in mice and found a correlation between np size and toxicity [40]. in this study, 8 mg per week of uncoated aunss with 3, 5, 8, 12, 17, 37, 50, and 100 nm diameters were injected intraperitoneally into mice [40]. these aunss were prepared according to the procedure in section 4.2 [40]. prior to injection, the aunss were purified by dialysis using pbs at a ph of 7.4 [40]. at the end of the experiment, the mice’s liver, lungs, spleen, and brain were isolated for analysis by ex vivo coherent anti-stoke raman scattering microscopy and weighed [40]. their results indicated that both aunps with larger and smaller diameters were non-toxic with notable toxicity observed for intermediate diameters [40]. neither toxic nor harmful effects were observed for those injected with aunss of diameters of 3, 5, 50, and 100 nm [40]. toxic effects like changes in fur colour, weight loss, and fatigue were observed in the mice injected with aunss ranging between 8 to 37 nm in diameter [40]. they also developed hemorrhaging, rashes, and bruising on their skin, as well as irregular spinal shapes [40]. the heart, brain, and kidney from the diseased groups were found to be distinctly different from the normal, healthy tissues of the control mice [40]. within the lungs of these mice, emphysema-like damage and a loss of structural integrity were observed [40]. abnormal amounts of white pulp were discovered in their spleens and a high amount of kupffer cells were found in their livers [40]. within 21 days, most of the mice in the 8 to 37 nm diameter groups died [40]. therefore, this study showed that the toxicity of aunss is size-dependent, with those having diameters less than 5 nm and between 50 to 100 nm being non-toxic in vivo in mice [40]. these results indicate that while in previous studies, aunss showed low toxicity in cell cultures, they can cause lethal effects in mammals at certain diameters and high enough doses [40]. this is an important factor for further research to ensure the safety of using aunss in ptt. 4.3. selective photothermal-induced cell death in a study conducted by el-sayed and colleagues [35], they demonstrated the ability of aunss conjugated to antiepithelial growth factor receptor (egfr) antibodies to selectively damage epithelial carcinoma cells. egfr is a biomarker that is overexpressed by oral squamous carcinoma cells so antibody conjugation can be used to increase the transportation of nanoparticles specifically to tumour cells [34, 35]. in this study, the citrate reduction of haucl4 was used to prepare the aunss [35]. using transmission electron microscopy (tem), the average particle size was found to be 40 nm [35]. a hepes buffer (20 mm, ph of 7.4) was added to the aunss until an optical density of 0.8 at 530 nm was achieved [35]. a dilute solution of anti-egfr monoclonal antibodies was then mixed for 20 min with 10 ml of the auns solution [35]. to prevent aggregation, peg was added (0.5 ml, 1%) [35]. next, the solution was centrifuged and a pbs buffer (ph of 7.4) was used to redisperse resulting pellets of anti-egfr antibodies and aunss [35]. comparison of four common gold nanoparticles for photothermal cancer therapy: a review 120 table 1: laser power densities per cell culture sample [35] cell type incubated with anti-egfr antibody conjugated aunss laser power densities (w/cm 2 ) benign hacat no 19, 25, 38, 50, 64, 76 benign hacat yes 13, 19, 25, 32, 38, 45, 51, 57, 64 malignant hoc 313 clone 8 and hsc 3 yes 13, 19, 25, 32, 38, 45, 51, 57, 64 table 2: photothermal cell destruction results by cell type and laser [35] cell type incubated with anti-egfr conjugated aunss laser power density (w/cm 2 ) approx. photothermal cell destruction (%) hacat no ≤ 76 0 hacat yes < 57 0 hacat yes ≥ 57 100 hsc yes < 19 0 hsc yes ≥ 25 100 hoc yes ≤ 13 0 hoc yes ≥ 19 100 benign human keratinocytes (hacat), were used as the control cells and two forms of malignant human oral squamous carcinoma cells (hoc 313 clone 8 and hsc 3) were used as the test sample cells [35]. these cells were submerged in the anti-egfr antibody conjugated auns solution for 40 min and then rinsed using a pbs buffer [35]. a cw argon laser with a wavelength of 514 nm was used to irradiate cells for four minutes continuously [35]. the laser power densities that the cells were irradiated at are displayed in table 1 [35]. to determine cell viability, 0.4% trypan blue was used to stain cells, which accumulates in dead cells [35]. optical microscopy was used to examine the cells [35]. the results of this experiment, summarized in table 2, indicated that cancerous cells treated with antiegfr conjugated aunss could be killed using less than half the amount of laser energy required to kill benign cells [35]. therefore, this is strong evidence of the ability of aunss to selectively kill malignant cells without damage to healthy cells [35]. the use of aunss in ptt is disadvantaged by their near 530 nm wavelength absorbance peak [10]. ideally, ptt is performed using nir radiation, which can penetrate and treat deeper tissues than visible light [10, 34, 41, 42]. to overcome this disadvantage, aunss can be clustered within or outside of the target cells, shifting their maximum surface plasmon absorption towards the nir region [10, 34, 41, 42]. in a study by huang et al. [43] that used a similar procedure to the previously detailed experiment by el-sayed et al. [35], clusters of 30 nm aunss were formed to shift their absorbance peak to the nir region. human oral squamous carcinoma cells (hsc3) were incubated with anti-egfr antibody conjugated aunss and untreated cells acted as a control [43]. cells were irradiated with 100 fs laser pulses with a wavelength of 800 nm [43]. the results of this study indicated that 20 times less laser power is required to induce photothermal destruction in cells that have been incubated with anti-egfr antibody conjugated aunss than those that were not [43]. this implies that using this method, even higher tumour-cell-specific killing can be achieved using a laser in the nir region and clusters of aunss in ptt [43]. more recently, it was found that photolabile, diazarine-decorated aunss can be triggered by a laser to form crosslinked aggregates, shifting their surface plasmon resonance to the nir region [42]. this novel technique presents an opportunity to precisely treat tumours and minimize damage to healthy cells by selectively triggering only the diazarine-decorated aunss within tumour regions. this method could serve as an effective modality for both enhancing photoacoustic imaging and ptt of tumours. an advantage of aunss in ptt is the potential to use the formation of microbubbles in a unique theragnostic system that can simultaneously image and treat tumours [10, 44]. in a study by lapotko et al. [44], clusters of aunss were formed outside target cells, causing observable laser-induced microbubbles and selective damage to target cells. in this experiment, stem cells, myeloid k562 cells, and human patient-derived acute b lymphoblastic leukemia cells were irradiated [44]. clusters of 30 nm aunss were formed on saiphoo et al., (2020): international journal of engineering materials and manufacture, 5(4), 116-129 121 the surface of k562 and leukemia cells by treating them with monoclonal antibodies [44]. cells were irradiated individually with 10 ns, 532 nm wavelength laser pulses at 5, 35, and 90 j/cm 2 optical fluences [44]. cells were also irradiated in a pbs solution with 1% fetal bovine serum at laser fluences of 0.5-2 j/cm 2 [44]. photothermal microscopy was used to detect microbubble formation and for live monitoring of cell damage on the nanosecond scale [44]. trypan blue was used to determine cell death [44]. the results of this experiment indicate the ability of the incubated aunss to cause photothermal microbubble formation and selective damage to malignant cells [44]. bubbles were only observed during the irradiation of target cells that were incubated with antibody conjugated aunss [44]. physical damage was also frequently observed for these cells [44]. at a fluence of 5 j/cm 2 , the damage probability was 100% for targeted cells and 7% for non-target cells [44]. at a fluence of 35 j/cm 2 , the damage probability was also low (9%) for non-target cells [44]. for the suspended cells, 100% of tumour cells were damaged compared to 16% of stem cells at a 1.7 j/cm 2 laser fluence [44]. 5 gold nanorods aunrs are a specific type of aunp that are elongated in one direction [45]. aunrs have unique optical and electronic properties that are dependent on the particles’ size and aspect ratio [46]. these particles are also anisotropic, which has sparked interest in the biomedical field for applications in drug and gene delivery, as contrast agents in optical imaging, and as ptas in cancer therapy [45, 47, 48]. this interest is due to the presence of two electromagnetic absorption peaks with a bandgap that is extremely tunable [45]. these absorption peaks correspond to the transverse and longitudinal edges and are caused by localized surface plasmon resonance in the np [45, 49]. the lspr can range from 600 to 1300 nm [45, 46, 50]. this section of the paper will look at notable studies on the use of aunr in hyperthermia to analyse its use in cancer treatment. 5.1. synthesis aunrs are commonly synthesized through seed or seedless mediation [45, 51, 52]. seed mediation is a three-step process of taking a face-cantered cubic (fcc) structure metal like au and creating a nanorod [45]. these steps include seed preparation by heavily reducing a gold precursor, preparation of the growth solution with a weak reducing agent, and finally the addition of gold seeds in the growth solution [45]. the seeds allow for the nanorod growth outwards in one direction [45]. seed mediation dates back to 2001 when jana et al. [53] pioneered the method of seed-mediated nanorod growth. seed-mediation is limited by the number of spherical particle by-products and has a low yield [45]. seedless mediation uses sodium borohydride as a seed substitute and is effective at creating smaller aunrs [52]. the use of sodium borohydride as opposed to a seed allows for simultaneous seed formation and aunr growth but follows a similar method as seed-mediated synthesis [52]. overall, the formation of aunrs has a low yield and is a difficult process due to the small nucleation window before isotropic growth occurs [45]. research into the use of microwaves to reduce synthesis times has shown to decrease the growth period time while also eliminating chemicals that would otherwise be required to stop rod elongation [54]. williams et al. [54] also noted a reduction in nanorod impurities while using microwave production. 5.2. toxicity a study by moros et al. [17] sought to find the toxicity of their previously synthesized 51x7 nm aunrs. to test the toxicity in vitro, glucose was attached to increase the uptake by cells [17]. melanoma cells (b16-f10) were incubated with aunrs for a day and then an mtt assay was used to measure metabolic activity and overall cell viability [17, 55]. this is ultimately a colorimetric assay that depends on mitochondrial oxidation of the cells in question [55]. fluorescence microscopy was used to ensure that uptake of aunrs by the cells occurred [17]. the results of this study indicated that the aunr cell uptake was 1.62 pg au/cell and no toxic effects on the cells were observed [17]. a high dose toxicity test was also performed using hydra, a small freshwater hydrozoa used in testing [17]. hydra polyps were placed in a solution of aunps (1 mg/ml) and incubated for 24h with and without peg [17]. the aunrs without peg and with cetyl trimethylammonium bromide (ctab) caused total animal destruction whereas the peglycated aunrs showed no damage to the hydra [17]. this suggests that the peglycated aunrs therefore are safe for human use since hydra are effective at modelling human reactions [17]. ctab is difficult to be removed from the nanorod causing the non-toxic form of aunrs to be hard to safely manufacture. ctab is necessary to direct rod growth but is also challenging to detect in solution due to its structure [56, 57]. a study by ali et al. [58] found similar results for aunr toxicity, where they injected a single dose of 25 nm aunrs into mice and then assessed the histopathology of vital organs at increasing time increments for up to 15 months. no negative side effects were found in the liver, spleen, lungs or kidneys and the mice also showed no visual signs of toxicity [58]. using tem, it was verified that there was an uptake of aunrs and some remained after 15 months without structural changes [58]. the highest levels of uptake were in the spleen with 78 ng of au per mg of dry tissue after 2 days and decreased to 35 ng of au per mg of dry tissue after 15 months [58]. the decrease in concentration is seen throughout the body due to some aunps being removed in excrement [58]. comparison of four common gold nanoparticles for photothermal cancer therapy: a review 122 5.3. effect of aspect ratio on heating effectiveness the percentage of extinction that a plasmonic np converts to heat increases as the particle size decreases [59]. decreasing particle size also decreases the value of extinction itself [59]. since these factors trend oppositely with size, this means there is an optimal size for maximizing heat generation within the aunp size range [59]. mackey et al. [52] compared how changing the aspect ratio of aunrs would affect their heating capabilities in ptt. the group created three sizes of aunrs (38×11, 28×8, and 17×5 nm) to use for comparison [52]. the larger aunrs were created using seed-mediated growth, creating aunrs with an approximate width and length of 11 nm and 38 nm, respectively [52]. the lspr of these nrs was approximately 740 nm [52]. the smaller aunrs were produced with a seedless chemistry method and a sodium borohydride seed substitute [52]. this resulted in aunrs with dimensions of 28x8 nm and 17x5 nm and lsprs of 770 nm and 755 nm, respectively [52]. these parameters are summarized in table 3. these three sizes of aunrs were then tested for their photothermal heating properties in solution by diluting them in h2o until they possessed the same optical density and then exposing them to a nir laser with a wavelength of 808 nm at 5.8 w/cm 2 [52]. a photothermal heat conversion factor was determined for each of the three sizes of aunrs by multiplying the change in temperature per aunr by a factor of 10 11 to increase the ease of comparison [52]. the findings from this study are shown in figure 2 [52]. it can be seen in figure 2 that the 28 nm aunr was the optimal size for use in ptt, as it had a greatest heat conversion factor for treatment times of 1 and 2 minutes with a maximum temperature change of 2.5x10 -11 °c/particle [52]. as the 28 nm aunrs had the best aspect ratio for optimal heating, this size produces the best balance between the percentage of extinction that is converted to heat and the size-extinction dependency [52]. the 17x5 nm aunr showed poor results comparatively [52]. table 3: overview of aunr’s parameters [52] size (nm) seeded lspr (nm) 38×11 yes 740 28x8 no 770 17x5 no 755 figure 2: comparison of photothermal heat conversion factors based on irradiation times with a nir laser and the size of aunrs [52]. saiphoo et al., (2020): international journal of engineering materials and manufacture, 5(4), 116-129 123 5.4. selective photothermal-induced cell death to determine the effectiveness of ptt with aunrs, moros and colleagues [17] used melanoma cells (b16-f10) that were incubated with aunrs for a day and then irradiated with a laser at intensities of 3, 4.5, and 30 w/cm 2 for 3 min [17]. the dish temperature was kept below 43 °c to ensure cell death was only caused by hotspots generated by the aunrs [17]. after 5 hr of recovery time, the cell's conditions were monitored [17]. it was found that the aunrs killed approximately 70% of the targeted tumour cells at 4.5 and 30 w/cm 2 , but no cell deaths at 3 w/cm 2 [17]. at 1 hr post irradiation, the cells remained expanded with a blebbing membrane, signifying apoptotic cell death [17]. similar effects were also found by soni et al. [60], where it was shown that the surrounding tissue was spared during the ptt using aunrs. this study showed that increasing the rod diameter could lead to an increase in photon scattering, which could result in damage to surrounding tissue [60]. a rod diameter increase from 5 to 15 nm increased the scattering coefficient by a factor of 76 with an increase in absorption efficiency by a factor of only 1.7 [60]. experiments performed by zhang et al. [61] found a decline in absorbance peaks after a significant period of laser exposure using an 808 nm laser at 0.8 w/cm 2 . the group also found that the aunrs exhibited the “melting effect” and underwent morphological changes to form approximately spherical aunps [61]. this change resulted in an overall change in absorption and indicated instability in the aunrs [61]. 6 gold nanoshells aunshs consist of a core material that lacks electrical conductivity and a gold shell [62, 63]. there are many variations in the cores of nanoshells, such as gold-sulfide, polystyrene latex sphere, and silica [55]. these types of nanoshells appear to be promising for cancer treatment, as their optical properties have a changeable plasmon resonance in the nir region [55]. specific types of aunsh have size limitations and can potentially form by-products during the fabrication process that can negatively interfere with the hyperthermia treatment [64, 55]. a key disadvantage for the use of polystyrene latex cores is that their resonances cannot produce sufficient heat to kill cancer cells in tumours [55]. studies that used an au2s core with a gold shell found this to have a suitable absorbance peak of 520-900 nm [63]. an additional limitation in the synthesis of au2s nanoshells is that the core and shell cannot be controlled independently [63]. they are dealt with as one structure, not as a separate shell and core, and this can produce harmful by-products that cannot be removed [63]. though there are a plethora of options, the most effective aunsh has been found to be the silica-gold nanoshell (ausinsh), which was developed around 25 years ago [55]. ausinshs show great promise with their structural integrity and adjustable resonance [26, 55]. this tunable plasmon resonance is significant in hybrid nanoshells of different materials, as they can be tailored to absorb or scatter light in the visible to nir region [55, 10]. the potential biomedical applications of ausinshs include cancer hyperthermia treatment [10]. 6.1. synthesis a common method of synthesis is the stober method, which consists of the silica core being grown to create particles with a 60 to 400 nm diameter [26, 55, 63]. there are drawbacks in this range, as the higher values are not considered to be nps and could potentially cause issues during treatment and may not be a suitable size for ptt [13]. in this method, an ethanol solution is used to reduce tetraethyl orthosilicate, allowing for the spherical silica colloid particles to begin to grow and develop in size [63]. reactions occur between the aminopropyltriethoxysilane and the silica surface to make it functional, which allows au colloid to be adsorbed and create the outer shell [63]. this au colloid layer will then be reduced by a haucl4 solution, which allows the au colloid layer to grow to the desired thickness [63]. this np evidently has a broad diameter range and researchers should be aware and stay within the optimal range for cancer treatment [63]. another factor to consider is that the stober method is quite complicated and can produce unwanted toxic by-products [63]. in 2020, riedel et al. [64] investigated the pulsed laser ablation in liquid method (plal) for the synthesis of ausinsh. this method has not yet been extensively researched for creating ausinsh for ptt; this is not its primary application [64]. this study appeared to have found a more straightforward process to synthesize ausinshs [64]. in this process, a laser was focused onto a rotating gold target submerged in a nasio2 and distilled water solution; the laser was focused for 15 min [64]. the ablation process resulted in ausinshs that had a diameter of 9 nm and a shell thickness of 2 nm [64]. 6.2. toxicity a study performed by sang-eun et al. [55] investigated how ausinsh with a clustered shell impacts the effectiveness of hyperthermia treatment. this method involved two different types of ausinshs, one being entirely covered with gold clusters (f-sgns) and the other being partially covered with disconnected gold-clusters (p-sgns) [55]. these nanoshells were both conjugated with erbitux (erb-sgnsh), an antibody target that binds to tumour-specific antigens, which is useful for tumour cell targeting [55]. the cytotoxicity of p-erb-sgns and f-erb-sgns was measured using a mtt assay prior to a laser treatment to measure photothermal performance [55]. the human epidermoid carcinoma cells were treated with p-erb-sgns and f-erb-sgns and incubated overnight [55]. cellular viabilities were analysed for both untreated and treated cancer cells; the treatment consisted ofp-erb-sgns and f-erb-sgns [55]. the ratio of the intensity of the purple comparison of four common gold nanoparticles for photothermal cancer therapy: a review 124 formazan present in the cancer cells after incubation was measured [55]. the results demonstrated that p-erb-sgns and f-erb-sgns have a low cytotoxicity, as there was an 80% cell viability before irradiation [55]. a study conducted by majidi et al. [65] used conjugated silica-gold nanoshells with folic acid (fa-sio2@au) as a tumour targeting agent, similarly to the erb in the past study. in this experiment, a sample of melanoma cells and healthy cells were treated with 100 μg/ml concentration of fa-sio2@au and sio2@au [65]. after the incubation period, both fa-sio2@au and sio2@au were found to be non-toxic to healthy cells, but toxic to cancer cells [65]. the cancer cells showed a significant drop in cell viability after the incubation period [65]. another study by riedel et al. [64] performed an in vivo test, where mice were intravenously injected with unconjugated ausinshs and the concentrations in the organs after 24 hr were measured. the results are displayed in figure 3 [64]. these ausinshs were synthesized using the plal method [64]. this study found a positive observation that there was no accumulation of the np in the brain due to the blood-brain barrier [64]. it was also found that no damage occurred in the heart, liver, spleen, lungs, and kidneys [64]. the concentration of nps in the organs decreased with time, and the particles degraded quickly in the body [64]. this further implies that the results from riedel and coworkers’ [64] study found that the plal method of synthesizing ausinshs was a much simpler process that demonstrated a lower toxicity in comparison. 6.3. selective photothermal-induced cell death sang et al. [55] also investigated the photothermal performance of ausinshs by treating epidermoid carcinoma cells with f-erb-sgns and p-erb-sgns. after treatment, they were incubated at 37 °c in dulbecco’s modified eagle’s medium (dmem) that contained 10% fetal bovine serum and 1% antibiotics. cells were then exposed to a nir laser at 820 nm at a power of 35 w/cm 2 for approximately 5 min [55]. this experiment found that more thermal energy was produced within the tumour that was treated with f-erbsgns than p-erb-sgns [55]. both nanoshells were found to have an absorption peak around 700-820 nm, which is promising as it falls within the nir region [55]. this study also found that there was a reduction in plasmon bands due to the accumulation of gold particles on the shell during synthesis [55]. their main finding was that ausinshs with a thick shell produce the strongest absorption band, but also the lowest solution temperature increase in comparison to the ausinshs with thinner shells [55]. overall, this indicates there was a lower hyperthermia effect when using nps with thicker shells due to dissipation within the thicker shell [55]. the cell death was measured after irradiation and it was found that the control group had a 100% cell viability with no cell deaths, whereas the f-erbsgns and p-erb-sgns treatment groups had 20.6% and 45.3% cell viability, respectively [55]. majidi et al. [65] used a similar process to the one used in the previous study, but the power intensity varied. an in-vitro test was conducted to investigate fa-sio2@au photothermal performance on melanoma cancer cells [65]. as mentioned, cancer cells were treated with fa-sio2@au and sio2@au prior to irradiation [65]. fa-sio2@au and sio2@au were absorbed in 10% dmem and incubated at 37 °c for 24 hr [65]. these cells were exposed to laser pulses of 808 nm wavelength and power intensity of 0.9 w/cm 2 [65]. it was found that the fa-sio2@au reduced the cell viability of tumour cells 31% more than the sio2@au; implying that the fa-sio2@au were more effective [65]. the study concluded that there was an overall 87% tumour cell death due to the use of fa-sio2@au [65]. figure 3: the concentration of ausinshs in major organs after 12, 24, and 72 hr periods post-injection [64]. saiphoo et al., (2020): international journal of engineering materials and manufacture, 5(4), 116-129 125 7 discussions aunss appear to be the optimal choice given the parameters of the absorption spectrum, toxicity, selective cell killing ability, size, synthesis, and additional qualitative advantages and disadvantages. the absorption spectrum for all of the nps considered landed within the nir region, therefore making them viable for use in ptt [10, 29, 38, 50, 55]. all four shapes have also been found to have low toxicity, indicating that they would cause minimal harm to healthy tissue and could be viable candidates for cancer hyperthermia treatment [38, 55, 63, 66]. however, due to the wellknown safety of aunss and their ability to be used in ptt without surface coatings [35], these appear to have the lowest risk of causing toxic effects if used in vivo in humans for hyperthermia cancer treatment. each aunp produced high percentages of tumour cell death with few control cells killed [17, 29, 35, 65]. when comparing these results, it is notable that the following differences between experiments might have affected results: cell type, aunps concentration, power densities, and irradiation duration. despite these differences, certain conclusions can be drawn. the best selective cell killing was found with aunss, with 100% tumour cell death [35]. the study by huang et al. [43] found that when using a nir laser, 20 times less power was required to kill cells treated with aggregates of antibody-conjugated aunss relative to control cells. this is comparable to 2 times less laser power when 514 nm light was used by el-sayed et al. [35], suggesting that selective cell killing using aunss would be further improved using huang and coworkers’ [43] method. these results indicate that aunss produced the highest percentage of selective tumour cell killing while inflicting minimal damage in healthy tissue [35]. since aunps need to enter the tissue before ptt irradiation, it is advantageous for them to be adjustable and smaller in size so they can selectively accumulate in tumours with varying sizes of fenestrations [10, 17]. aunss are functional with sizes down to a diameter of 3 nm, the smallest of the 3 other aunps compared as shown in table 5 [40]. this small size is important to be able to accumulate in immature tumours with smaller fenestrations [10]. the synthesis of medical technology should be rapid and efficient to optimize overall production and minimize costs [67]. aunss can be synthesized through a rapid reduction of haucl4, which is simple in comparison to the synthesis of other aunps. their ability to be produced using a rapid, highly efficient microwave-aided method is a promising avenue for large, commercial scale production, which can reduce costs [39, 67, 68, 69]. furthermore, particle size can also be adjusted through controlling reaction times and temperatures [39, 40]. aunss’ synthesis is efficient [10] and can be easily modified to create auns ranging from 3-100 nm [40]. aunss have the ability to be easily conjugated to various antibodies, improving the ability to accumulate in tumour tissue selectively [35]. lastly, the use of auns provides a unique opportunity to simultaneously image the photothermal-induced damage during treatment due to the production of microbubbles [10, 44]. overall, these advantages of aunss over other aunps make them ideal for ptt to potentially improve the prognosis and quality of cancer treatment for many patients in the future. table 4: summary of targeted cancer cell killing studies by aunp type. sources: [17, 29, 35, 65] np type cells/ animal laser power density (w/cm 2 ) irradiation length (min) % tumour cell death aunc [29] mice 0.7 10 70 auns [35] cells 25 19 4 4 100 (hsc) 100 (hoc) aunr [17] cells 4.5 30 3 3 70 70 ausinsh [65] cells 0.9 5 87 table 5: summary of typical particle sizes. sources: [29, 40, 52, 63]. *9 nm diameter ausinshs have recently been formed using plal technology [64] np type dimension (nm) aunc [29] edge length: 47 diameter: 99 auns [40] diameter: 3-100 aunr [52] diameter: 5-11 length: 17-51 ausinsh [63] diameter: 9* or 60-400 comparison of four common gold nanoparticles for photothermal cancer therapy: a review 126 8 conclusions and furure recommendations 1. nanoparticle-enhanced photothermal therapy presents a promising opportunity to advance cancer treatment beyond current methods that frequently cause non-specific damage to healthy tissues and undesirable side effects. ideally, the particles would cause no toxic effects in vivo, be fast and easy to synthesize without toxic byproducts, be able to selectively kill all tumour cells during ptt and have a maximum surface plasmon absorption in the nir region. 2. the use of gold is optimal due to its high biocompatibility, corrosion-resistance, low toxicity, and strong absorption of radiation in the nir and visible light regions. 3. aunss appear to be the most effective aunp for the treatment of cancer using nanoparticle-enhanced ptt. these have been shown to outperform aunrs, auncs, and ausinshs in the categories of toxicity, selective cell killing, and synthesis. in addition, they can be a sufficiently small size to accumulate in tumour tissue and their absorption peak can be shifted to the nir region. 4. ausinshs are another promising method for ptt when they are synthesized through the plal method, as this is more time-efficient than the conventional stober method [63, 64]. this reduces the ausinshs’ diameter range to fall within the range of a np [13]. however, this method has not been extensively researched and further work in this area is required to fully validate this method [64]. 5. with 225,800 canadians expected to be diagnosed with cancer in 2020, aunss should be further researched for use in aunp-enhanced ptt. [70]. further testing must be performed to ensure the safety of aunps in vivo in humans. additionally, while studies have shown forms of aunps to be acutely non-toxic in rodent models, the long-term effects of these particles in vivo must be rigorously tested to ensure their safety moving forward from preclinical to clinical studies. 6. aunps provide a promising opportunity to provide highly targeted and selective cancer treatments, unique from many currently in use. their unique properties and effective use in ptt have been shown preclinically, demonstrating their potential to help improve the outcome and quality of life for future cancer patients. references 1. canadian cancer statistics advisory committee. (2019). canadian cancer statistics. toronto, on: canadian cancer society. https://www.cancer.ca/~/media/cancer.ca/cw/cancer%20information/cancer%20101/canadian%20cancer% 20statistics/canadian-cancer-statistics-2019-en.pdf?la=en 2. brenner, d. r., weir, h. k., demers, a. a., ellison, l. f., louzado, c., shaw, a., turner, d., woods, r., & smith, l. canadian cancer statistics advisory committee. (2020). projected estimates of cancer in canada in 2020. cmaj: canadian medical association journal = journal de l'association medicale canadienne, 192(9), e199e205. doi:10.1503/cmaj.191292 3. oliveira, c. d., pataky, r., bremner, k. e., rangrej, j., chan, k. k. w., cheung, w. y., hoch, j. s., peacock, s., & krahn, m. d. (2017). estimating the cost of cancer care in british columbia and ontario: a canadian interprovincial comparison. healthcare policy/politiques de santé, 12(3), 95-108. doi:10.12927/hcpol.2017.2502 4. sun, t., zhang, y. s., pang, b., hyun, d. c., yang, m., & xia, y. (2014). engineered nanoparticles for drug delivery in cancer therapy. angewandte chemie international edition, 53(46), 12320-12364. doi:10.1002/anie.201403036 5. kudarha, r. r., & sawant, k. k. (2017). albumin based versatile multifunctional nanocarriers for cancer therapy: fabrication, surface modification, multimodal therapeutics and imaging approaches. materials science & engineering c, 81, 607-626. doi:10.1016/j.msec.2017.08.004 6. stone, j. b., & deangelis, l. m. (2016). cancer-treatment-induced neurotoxicity--focus on newer treatments. nature reviews. clinical oncology, 13(2), 92-105. doi:10.1038/nrclinonc.2015.152 7. trautinger, f., eder, j., assaf, c., bagot, m., cozzio, a., dummer, reinhard., gniadecki, r., klemke, c. d., ortiz-romero, p. l., papadavid, e., pimpinelli, n., quaglino, p., ranki, a., scarisbrick, j., stadler, r., väkevä, l., vermeer, m. h., whittaker, s., willemze, r., knobler, r. (2017). european organisation for research and treatment of cancer consensus recommendations for the treatment of mycosis fungoides/sézary syndrome – update 2017. european journal of cancer, 77, 57-74. doi:10.1016/j.ejca.2017.02.027 8. fletcher, c., wilson, c., hutchinson, a. d., & grunfeld, e. a. (2018). the relationship between anticipated response and subsequent experience of cancer treatment-related side effects: a meta-analysis comparing effects before and after treatment exposure. cancer treatment reviews, 68, 86-93. doi:10.1016/j.ctrv.2018.06.009 9. national cancer institute. (2019, january 18). radiation therapy to treat cancer. national cancer institute at the national institutes of health, u.s. department of health and human services. https://www.cancer.gov/about-cancer/treatment/types/radiation-therapy 10. kennedy, l. c., bickford, l. r., lewinski, n. a., coughlin, a. j., hu, y., day, e. s., west, j.l., & drezek, r.a. (2011). a new era for cancer treatment: gold‐nanoparticle‐mediated thermal therapies. small, 7(2), 169-183. doi:10.1002/smll.201000134 saiphoo et al., (2020): international journal of engineering materials and manufacture, 5(4), 116-129 127 11. avedisian, c. t., cavicchi, r. e., mceuen, p. l., & zhou, x. (2009). nanoparticles for cancer treatment: role of heat transfer. annals of the new york academy of sciences, 1161(1), 62-73. doi:10.1111/j.17496632.2009.04090.x 12. mirzajavadkhan, a., rafieian, s., & hasan, m. h. (2020). toxicity of metal implants and their interactions with stem cells: a review. international journal of engineering materials and manufacture, 5(1), 2-11. https://doi.org/10.26776/ijemm.05.01.2020.02 13. aghebati‐maleki, a., dolati, s., ahmadi, m., baghbanzhadeh, a., asadi, m., fotouhi, a., yousefi, m., & aghebati‐maleki, l. (2020). nanoparticles and cancer therapy: perspectives for application of nanoparticles in the treatment of cancers. journal of cellular physiology, 235(3), 1962-1972. doi:10.1002/jcp.29126 14. gerber, a., bundschuh, m., klingelhofer, d., & groneberg, d. a. (2013). gold nanoparticles: recent aspects for human toxicology. journal of occupational medicine and toxicology (london, england), 8(1), 32-32. doi:10.1186/1745-6673-8-32 15. huang, x., jain, p. k., el-sayed, i. h., & el-sayed, m. a. (2006). determination of the minimum temperature required for selective photothermal destruction of cancer cells with the use of immunotargeted gold nanoparticles. photochemistry and photobiology, 82(2), 412-417. doi:10.1562/2005-12-14-ra-754 16. yang, w., liang, h., ma, s., wang, d., & huang, j. (2019). gold nanoparticle based photothermal therapy: development and application for effective cancer treatment. sustainable materials and technologies, 22, e00109. doi:10.1016/j.susmat.2019.e00109 17. moros, m., lewinska, a., merola, f., ferraro, p., wnuk, m., tino, a., & tortiglione, c. (2020). gold nanorods and nanoprisms mediate different photothermal cell death mechanisms in vitro and in vivo. acs applied materials & interfaces. doi:10.1021/acsami.0c02022 18. farrokhtakin, e., ciofani, g., puleo, g. l., de vito, g., filippeschi, c., mazzolai, b., vincenzo, p., mattoli, v. (2013). barium titanate core--gold shell nanoparticles for hyperthermia treatments. international journal of nanomedicine, 8(1), 2319-2331. doi:10.2147/ijn.s45654 19. cherukuri, p., glazer, e. s., & curley, s. a. (2010). targeted hyperthermia using metal nanoparticles. advanced drug delivery reviews, 62(3), 339-345. doi:10.1016/j.addr.2009.11.006 20. jha, s., sharma, p., & malviya, r. (2016). hyperthermia: role and risk factor for cancer treatment. achievements in the life sciences, 10(2), 161-167. 21. dykman, l., & khlebtsov, n. (2012). gold nanoparticles in biomedical applications: recent advances and perspectives. chemical society reviews, 41(6), 2256-2282. doi:10.1039/c1cs15166e 22. petryayeva, e., & krull, u. j. (2011). localized surface plasmon resonance: nanostructures, bioassays and biosensing—a review. analytica chimica acta, 706(1), 8-24. doi:10.1016/j.aca.2011.08.020 23. lu, y., & mahato, r. i. (2009). pharmaceutical perspectives of cancer therapeutics. springer us. 24. dreaden, e., alkilany, a., huang, x., murphy, c., & el-sayed, m. (2012). the golden age: gold nanoparticles for biomedicine. chemical society reviews, 41(7), 2740-2779. 25. huang, x., & el-sayed, m. a. (2010). gold nanoparticles: optical properties and implementations in cancer diagnosis and photothermal therapy. journal of advanced research, 1(1), 13–28. https://doi.org/10.1016/j.jare.2010.02.002 26. everts, m. (2007). thermal scalpel to target cancer. expert review of medical devices, 4(2), 131-136. doi:10.1586/17434440.4.2.131 27. huang, y., cambre, m., & lee, h. (2017). the toxicity of nanoparticles depends on multiple molecular and physicochemical mechanisms. international journal of molecular sciences, 18(12), 2702. doi:10.3390/ijms18122702 28. su, y., wei, x., peng, f., zhong, y., lu, y., su, s., xu, t., lee, s., he, y. (2012). gold nanoparticles-decorated silicon nanowires as highly efficient near-infrared hyperthermia agents for cancer cells destruction. nano letters, 12(4), 1845-1850. doi:10.1021/nl204203t 29. chen, j., glaus, c., laforest, r., zhang, q., yang, m., gidding, m., welch, m. j., & xia, y. (2010). gold nanocages as photothermal transducers for cancer treatment. small, 6(7), 811-817. doi:10.1002/smll.200902216 30. rengan, a. k., kundu, g., banerjee, r., & srivastava, r. (2014). gold nanocages as effective photothermal transducers in killing highly tumorigenic cancer cells. particle & particle systems characterization, 31(3), 398405. doi:10.1002/ppsc.201300173 31. zeng, j., goldfeld, d., & xia, y. (2013). a plasmon‐assisted optofluidic (paof) system for measuring the photothermal conversion efficiencies of gold nanostructures and controlling an electrical switch. angewandte chemie international edition, 52(15), 4169-4173. doi:10.1002/anie.201210359 32. feng, y., cheng, y., chang, y., jian, h., zheng, r., wu, x., xu, k., wang, l., ma, x., li, x., zhang, h. (2019). time-staggered delivery of erlotinib and doxorubicin by gold nanocages with two smart polymers for reprogrammable release and synergistic with photothermal therapy. biomaterials, 217, 119327. doi:10.1016/j.biomaterials.2019.119327 33. jenkins, s. v., nedosekin, d. a., shaulis, b. j., wang, t., jamshidi-parsian, a., pollock, e. d., chen, j., dings, r. r. m., & griffin, r. j. (2019). enhanced photothermal treatment efficacy and normal tissue protection via vascular targeted gold nanocages. nanotheranostics, 3(2), 145-155. doi:10.7150/ntno.32395 https://doi.org/10.26776/ijemm.05.01.2020.02 comparison of four common gold nanoparticles for photothermal cancer therapy: a review 128 34. panikkanvalappil, s. r., hooshmand, n., & el-sayed, m. a. (2017). intracellular assembly of nuclear-targeted gold nanosphere enables selective plasmonic photothermal therapy of cancer by shifting their absorption wavelength toward near-infrared region. bioconjugate chemistry, 28(9), 2452–2460. https://doi.org/10.1021/acs.bioconjchem.7b00427 35. el-sayed, i. h., huang, x., & el-sayed, m. a. (2006). selective laser photo-thermal therapy of epithelial carcinoma using anti-egfr antibody conjugated gold nanoparticles. cancer letters, 239(1), 129-135. doi:10.1016/j.canlet.2005.07.035 36. el-sayed, i. h., singer, m. i., & civantos, f. (2005). sentinel lymph node biopsy in head and neck cancer. otolaryngologic clinics of north america, 38(1), 145–160. https://doi.org/https://doi.org/10.1016/j.otc.2004.09.004 37. sherman, a. i., ter‐pogossian, m., & with the technical assistance of edward c tocus. (1953). lymph‐node concentration of radioactive colloidal gold following interstitial injection. cancer, 6(6), 1238–1240. https://doi.org/10.1002/1097-0142(195311)6:6<1238::aid-cncr2820060618>3.0.co;2-6 38. pitsillides, c. m., joe, e. k., wei, x., anderson, r. r., & lin, c. p. (2003). selective cell targeting with lightabsorbing microparticles and nanoparticles. biophysical journal, 84(6), 4023-4032. doi:10.1016/s00063495(03)75128-5 39. liu, f., ker, c., chang, y., ko, f., chu, t., & dai, b. (2003). microwave heating for the preparation of nanometer gold particles. japanese journal of applied physics, 42(part 1, no. 6b), 4152-4158. doi:10.1143/jjap.42.4152 40. chen, y., hung, y., liau, i., & huang, g. s. (2009). assessment of the in vivo toxicity of gold nanoparticles. nanoscale research letters, 4(8), 858-864. doi:10.1007/s11671-009-9334-6 41. huang, x., jain, p., el-sayed, i., & el-sayed, m. (2008). plasmonic photothermal therapy (pptt) using gold nanoparticles. lasers in medical science, 23(3), 217-228. 42. cheng, x., sun, r., yin, l., chai, z., shi, h., & gao, m. (2017). light-triggered assembly of gold nanoparticles for photothermal therapy and photoacoustic imaging of tumors in vivo. advanced materials, 29(6), 1604894. https://doi.org/10.1002/adma.201604894 43. huang, x., qian, w., el‐sayed, i. h., & el‐sayed, m. a. (2007). the potential use of the enhanced nonlinear properties of gold nanospheres in photothermal cancer therapy. lasers in surgery and medicine, 39(9), 747753. doi:10.1002/lsm.20577 44. lapotko, d., lukianova, e., potapnev, m., aleinikova, o., & oraevsky, a. (2006). method of laser activated nano-thermolysis for elimination of tumour cells. cancer letters, 239(1), 36-45. doi:10.1016/j.canlet.2005.07.031 45. chhatre, a., thaokar, r., & mehra, a. (2018). formation of gold nanorods by seeded growth: mechanisms and modeling. crystal growth & design, 18(6), 3269-3282. doi:10.1021/acs.cgd.7b01387 46. vigderman, l., khanal, b. p., & zubarev, e. r. (2012). functional gold nanorods: synthesis, self‐assembly, and sensing applications. advanced materials, 24(36), 4811-4841. doi:10.1002/adma.201201690 47. kannadorai, r. k., chiew, g. g. y., luo, k. q., & liu, q. (2014;2015;). dual functions of gold nanorods as photothermal agent and autofluorescence enhancer to track cell death during plasmonic photothermal therapy. ireland: elsevier b.v. doi:10.1016/j.canlet.2014.11.022 48. brioude, a., jiang, x. c., & pileni, m. p. (2005). optical properties of gold nanorods:  dda simulations supported by experiments. the journal of physical chemistry b, 109(27), 13138-13142. doi:10.1021/jp0507288 49. zhao, t., shen, x., li, l., guan, z., gao, n., yuan, p.,yao, s. q., xu, q., xu, g. q. (2012). gold nanorods as dual photo-sensitizing and imaging agents for two-photon photodynamic therapy. nanoscale, 4(24), 7712. doi:10.1039/c2nr32196c 50. nikoobakht, b., & el-sayed, m. a. (2003). preparation and growth mechanism of gold nanorods (nrs) using seed-mediated growth method. chemistry of materials, 15(10), 1957-1962. doi:10.1021/cm020732l 51. scarabelli, l., sánchez-iglesias, a., pe ́rez-juste, j., & liz-marzán, l. m. (2015). a “tips and tricks” practical guide to the synthesis of gold nanorods. united states: american chemical society. doi:10.1021/acs.jpclett.5b02123 52. mackey, m. a., ali, m. r. k., austin, l. a., near, r. d., & el-sayed, m. a. (2014). the most effective gold nanorod size for plasmonic photothermal therapy: theory and in vitro experiments. the journal of physical chemistry b, 118(5), 1319-1326. doi:10.1021/jp409298f 53. jana, n. r., gearheart, l., & murphy, c. j. (2001). seeding growth for size control of 5−40 nm diameter gold nanoparticles. langmuir, 17(22), 6782-6786. doi:10.1021/la0104323 54. williams, m. g., boyne, d. a., & griep, m. h. (2017). rapid synthesis of high purity gold nanorods via microwave irradiation. materials research express, 4(3), 35040. doi:10.1088/2053-1591/aa66de 55. sang-eun park, lee, j., lee, t., bae, s., kang, b., yong-min, h., lee, s., & haam, s. (2015). comparative hyperthermia effects of silica–gold nanoshells with different surface coverage of gold clusters on epithelial tumour cells. international journal of nanomedicine, 10, 261-271. doi:http://dx.doi.org.ezproxy.lib.ryerson.ca/10.2147/ijn.s88309 56. smith, d. k., miller, n. r., & korgel, b. a. (2009). iodide in ctab prevents gold nanorod formation. langmuir, 25(16), 9518-9524. doi:10.1021/la900757s https://doi.org/10.1021/acs.bioconjchem.7b00427 https://doi.org/10.1002/adma.201604894 http://dx.doi.org.ezproxy.lib.ryerson.ca/10.2147/ijn.s88309 saiphoo et al., (2020): international journal of engineering materials and manufacture, 5(4), 116-129 129 57. he, j., unser, s., bruzas, i., cary, r., shi, z., mehra, r., aron, k., sagle, l. (2018). the facile removal of ctab from the surface of gold nanorods. colloids and surfaces, b, biointerfaces, 163, 140-145. doi:10.1016/j.colsurfb.2017.12.019 58. ali, m. r. k., rahman, m. a., wu, y., han, t., peng, x., mackey, m. a., wang, d., shin, h. j., chen, z. g., xiao, h., wu, r., tang, y., shin, d. m., el-sayed, m. a. (2017). efficacy, long-term toxicity, and mechanistic studies of gold nanorods photothermal therapy of cancer in xenograft mice. proceedings of the national academy of sciences pnas, 114(15), e3110-e3118. doi:10.1073/pnas.1619302114 59. jain, p. k., lee, k. s., el-sayed, i. h., & el-sayed, m. a. (2006). calculated absorption and scattering properties of gold nanoparticles of different size, shape, and composition:  applications in biological imaging and biomedicine. the journal of physical chemistry b, 110(14), 7238-7248. doi:10.1021/jp057170o 60. soni, s., tyagi, h., taylor, r. a., & kumar, a. (2013). role of optical coefficients and healthy tissue-sparing characteristics in gold nanorod-assisted thermal therapy. international journal of hyperthermia, 29(1), 87-97. doi:10.3109/02656736.2012.753162 61. zhang, p., wang, j., huang, h., yu, b., qiu, k., huang, j., wang, s., jiang, l., gasser, g., ji, l., & chao, h. (2015). unexpected high photothermal conversion efficiency of auns upon grafting with two-photon luminescent ruthenium (ii) complexes: a way towards cancer therapy? biomaterials, 63, 102-114. doi:10.1016/j.biomaterials.2015.06.012 62. nouri, s., mohammadi, e., mehravi, b., majidi, f., ashtari, k., neshasteh-riz, a., & einali, s. (2019). nir triggered glycosylated gold nanoshell as a photothermal agent on melanoma cancer cells. artificial cells, nanomedicine, and biotechnology, 47(1), 2316-2324. doi:10.1080/21691401.2019.1593187 63. hirsch, l. r., gobin, a. m., lowery, a. r., tam, f., drezek, r. a., halas, n. j., & west, j. l. (2006). metal nanoshells. annals of biomedical engineering, 34(1), 15-22. doi:10.1007/s10439-005-9001-8 64. riedel, r., mahr, n., yao, c., wu, a., yang, f., & hampp, n. (2020). synthesis of gold-silica core-shell nanoparticles by pulsed laser ablation in liquid and their physico-chemical properties towards photothermal cancer therapy. nanoscale, 12(5), 3007-3018. doi:10.1039/c9nr07129f 65. majidi, f. s., mohammadi, e., mehravi, b., nouri, s., ashtari, k., & neshasteh-riz, a. (2019). investigating the effect of near infrared photo thermal therapy folic acid conjugated gold nano shell on melanoma cancer cell line a375. artificial cells, nanomedicine, and biotechnology, 47(1), 2161-2170. doi:10.1080/21691401.2019.1593188 66. rastinehad, a. r., anastos, h., wajswol, e., winoker, j. s., sfakianos, j. p., doppalapudi, s. k., carrick, m.r., knauer, c. j., taouli, b., lewis, s. c., tewari, a. k., schwartz, j. a., canfield, s. e., george, a. k., west, j. l., halas, n. j. (2019). gold nanoshell-localized photothermal ablation of prostate tumors in a clinical pilot device study. proceedings of the national academy of sciences of the united states of america, 116(37), 18590-18596. doi:10.1073/pnas.1906929116 67. nauenberg, e. (2014). changing healthcare capital-to-labor ratios: evidence and implications for bending the cost curve in canada and beyond. international journal of health care finance and economics, 14(4), 339353. doi:10.1007/s10754-014-9154-9 68. sreejith raveendran anindito sen toru maekawa d. sakthi kumar. (2017). ultra-fast microwave aided synthesis of gold nanocages and structural maneuver studies. nano research, 10(3), 1078-1091. doi:10.1007/s12274-0161368-3. 69. world health organization (who). (2017, february 3). early cancer diagnosis saves lives, cuts treatment costs. world health organization. https://www.who.int/news-room/detail/03-02-2017-early-cancer-diagnosis-saveslives-cuts-treatment-costs 70. government of canada. (2020, february 28). cancer-specific stats 2020. https://www.cancer.ca/~/media/cancer.ca/cw/cancer%20information/cancer%20101/canadian%20cancer% 20statistics%20supplementary%20information/2020/2020_cancer-specific-stats.pdf?la=en international journal of engineering materials and manufacture (2021) 6(4) 225-241 https://doi.org/10.26776/ijemm.06.04.2021.01 eisenstat, j. a. 1 , gotthardt, d. a. 1 , assor, r. 1 , dempsey l. r. 1 and hasan, m. h. 2 1 department of electrical, computer, and biomedical engineering 2 department of mechanical and industrial engineering ryerson university, canada e-mail: hasibulhasan@ryerson.ca reference: eisenstat et al. (2021). a comparative review of material properties for current and future dental filling nanomaterials. international journal of engineering materials and manufacture, 6(4), 225-241. a comparative review of material properties for current and future dental filling nanomaterials joshua a. eisenstat, dennis a. gotthardt, rebecca assor, liam r. dempsey and muhammad h. hasan received: 10 february 2021 accepted: 20 april 2021 published: 01 october 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract nanomaterials observe specialized properties relative to gross materials. due to their small size, specialized nanomaterial properties include decreased reactivity, an increased surface area to volume ratio, heightened structural properties, and in some cases, antimicrobial and antibacterial effects. current researchers are looking to use nanoparticle/nanomaterial properties to solve prevalent dental issues that cannot be addressed with traditionally used materials. this paper serves as an extensive review of current nanomaterial applications as they pertain to dental fillings and dental filling processes. comparative assessments of traditional materials used in dental fillings were made, as well as comparative assessments of currently used nanomaterials in dental fillings. material comparisons are based on criteria pertaining to biocompatibility, toxicity, reactivity, cost, and antimicrobial/antibacterial properties. when comparing the three most currently used dental filling nanomaterials – carbon-based nanotubes, silica nanoparticles and silver-coated nanoparticles – it was observed that silica nanoparticles demonstrated the greatest material advantage and should be recommended for continued use. issues regarding future developmental dental filling applications of graphene nanoparticles, starch nanoparticles, organic nanoparticles and gold nanoparticles were also reviewed. keywords: nanomaterials, antibacterial, dental fillings, silica resins, biocompatibility. 1 introduction strong emphasis is placed on oral hygiene and dental appearance in western society. this is evident when observing the financial capital designated towards dental care in western countries. in 2015, canada spent 12.7 billion dollars on dental care [1]. comparatively, the united states of america spent 124 billion dollars on dental care [2]. the current spectrum of dental procedures ranges from physical repairs dental fillings, root canals to cosmetic procedures, such as teeth whitening. the world health organization reported that roughly 60-90 percent of children and about 100 percent of adults worldwide have experienced cavities [3]. as a result, dental fillings are the most performed dental procedures [4]. traditional dental filling materials include amalgam, glass ionomers, resin ionomers, resin composites as well as gold and nickel alloys [5]. among traditional dental filling materials, each observes distinct advantages and disadvantages. since some materials have better properties than others life expectancy, toxicity, corrosion, etc.it is often difficult to find the optimal dental filling material [5]. faced with complications associated with traditional dental filling materials, researchers are looking to nanomaterials for solutions. nanomaterials are composed of nanometer sized particles. due to the small particle size, nanomaterials often exhibit special physical and chemical properties not observed in gross materials [5]. due to the special properties of nanomaterials, extensive research has been conducted looking into the advantages and disadvantages of using nanomaterials for medical and dental applications [6]. this paper will provide a comprehensive review of the current methods for using nanomaterials in dental fillings, an in-depth comparison of those current methods highlighting advantages and disadvantages, as well as look into future developments regarding the applications of nanomaterials in dental fillings. eisenstat et al. (2021): international journal of engineering materials and manufacture, 6(4), 225-241 226 2 traditional dental fillings – an overview a variety of traditional materials are used for dental filling procedures. traditionally used dental filling materials include dental amalgams, resin ionomers, composite resins and glass ionomers. dental filling material selection is based on properties including viscosity, moldability and the ideal marginal integrity of the dental filling in the tooth [7]. dental fillings are also chosen based on susceptibility to corrosion from ph, temperature, protein, saliva, oral health conditions, and diet [8]. saliva, for example, has a ph range of 5.2 to 7.8. food consumption and diet must also be taken into consideration during dental filling material selection. the more acidic the food is, the more likely corrosion will occur to dental fillings and teeth [8]. among traditionally used dental filling materials, there is not one material that provides a solution to all problems. in fact, some currently used traditional dental filling materials can induce unintended health defects. for example, dental amalgam a commonly used dental filling material – could pose health risks for patients due to its high mercury concentration [5]. traditional dental filling materials each come with their respective advantages and disadvantages [5]. table 1: advantages and disadvantages of traditional dental fillings [5] dental filling advantages disadvantages dental amalgam durable inexpensive good corrosion resistance aesthetically displeasing potential toxic mercury content resin ionomer aesthetically pleasing limited sensitivity to temperature changes relatively good against future decay poor wear resistance expensive composite resins good strength and toughness aesthetically pleasing good wear resistance varying tooth sensitivity sensitive to temperature changes expensive glass ionomers aesthetically pleasing relatively good against future decay minimal sensitivity poor wear resistance 2.1 nanomaterial dental filling biocompatibility external materials can be inserted into the body only if they are biocompatible with live tissue. nanomaterials are said to be biocompatible if a homogeneous composition can be made with the inserted nanomaterial and biological tissue. homogeneous nanomaterials demonstrate satisfactory biocompatibility in the patient’s oral cavity relative to heterogeneous nanomaterial compositions [9]. if the added nanomaterials observe high levels of reactivity with the inorganic dental filling material, it is an indication of a homogeneous composition. high levels of nanoparticle reactivity with dental fillings are observed to be beneficial [9]. however, if the added nanomaterials have a high level of reactivity with soft tissue in the oral cavity gums, enamel, tongue then the biocompatibility of the dental filling is deemed unsatisfactory, and the nanoparticle’s high level of reactivity becomes problematic [9]. material reactivity is determined by quantifying the relationship of the surface area relative to the given volume ratio of the particles [10]. this relationship can be described using the following equations 1-3 [10]. as the radius of a particle decreases, reactivity of the particle increases, as illustrated in the mathematical principles in equation 3. due to the small radius of nanoparticles, chemical reactivity increases gradually. nanomaterial toxicity is a result of their small particle size. smaller particle size allows for easier passage through different body membranes [11]. 𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝐴𝑟𝑒𝑎 = 4𝜋𝑟2 (1) 𝑉𝑜𝑙𝑢𝑚𝑒 = 4 3 𝜋𝑟3 (2) 𝑅𝑒𝑎𝑐𝑡𝑖𝑣𝑖𝑡𝑦 = 𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝐴𝑟𝑒𝑎 𝑉𝑜𝑙𝑢𝑚𝑒 = 4𝜋𝑟2 4 3 𝜋𝑟3 = 3 𝑟 (3) a comparative review of material properties for current and future dental filling nanomaterials 227 3 current and previously conducted dental filling nanomaterial research 3.1 polymethyl methacrylate (pmma) the most common material used in dental fillings today are composite resin fillings [12]. this is due to the visual similarity of the resin material and dental tissue. current research has developed a nanomaterial composite resin filler as an alternative to traditionally used composite resin fillers. polymethyl methacrylate (pmma) is a nanocomposite resin filling that has been observed to be a more effective resin filler than current composite resin filler variants. experimental trials determined that a 5% volume fraction of 40% titania (𝑇𝑖𝑂2), and 60% calcium aluminate (𝐶𝑎𝐴𝑙2𝑂4) nanoparticles presented the longest life, best surface interactions (tribological characteristics), and the most stable nano-composition supported by nanoparticles [12]. under experimental trials, pmma has exhibited satisfactory cytotoxicity metrics by demonstrating low damage to erythrocytes and even promoting cellular activity [13]. additionally, pmma has seen expanded use cases regarding denture efficacy and applicability. when compared to other artificial materials pmma has demonstrated a harder enamel surface replacement and increased wear resistance [14]. 3.2 nanomaterial composite resins research has been done to create new nanoparticle composite resins [15]. composite resins are a type of restorative material [15]. examples being strengthening agents like mineral filler particles [15]. these materials can be dispersion reinforced, particulate reinforced, or hybrid composites. although these resins have high dispersion reinforcement, microfill resins are relatively weak structurally. this limits them only to low stress restorations [15]. the goal of this dental filling material was to retain high strength properties for load-bearing restorations and keep its glossy appearance after long periods of wear [15]. the dental composite is applied to the teeth and then exposed to a light source. the light source is used to cure the resin material. the resin is suitable for use in stress bearing applications because of its flexural strength of more than 100mpa [15]. structural fillers that are suitable for this resin are barium magnesium aluminosilicate glass, barium aluminoborosilicate glass (bag), amorphous silica, silica-zirconia, silica-titania, barium oxide, quartz, alumina and various other inorganic oxide particles [15]. the particles present have an average particle size of 0.05 μm to 0.50 μm plus a nanofiller, which observes an average particle size of roughly 100 nm [15]. 3.3 silica nanomaterial resins silica nanoparticles are featured prominently in various current dental filling applications. largely due to the high wear resistance and strong antimicrobial and antibacterial properties [16]. studies have demonstrated significant reduction in oral bacteria escherichia. coli and staphylococcus aureus when placed near silica nanoparticles, highlighting antibacterial effectiveness against both gram-negative and gram-positive bacteria [17]. a common use case of silica nanoparticles is the infusion of silica nanoparticles within traditional dental filling materials. in one study, silica nanoparticles (ox-50) and porous diatomite particles were combined with resin to further determine their combined mechanical properties [18]. silica and porous diatomite particles were added to dental resin at different mass ratios ranging from 60% 75% [18]. it was observed that with the increase of the silica diatomite mass composition, the mechanical properties of the resin increased. with the highest microhardness composite at 75% of silica porous diatomite particles, it was determined that nanosized silica and porous diatomite particles have a demonstrable impact on the mechanical properties of dental resin composites [18]. 3.4 silver coated nanomaterials optical glass fibers can be coated with silver nanoparticles. this was an alternative material for root dental fillings during endodontic therapy (root canal treatment) [19]. the material was used because of its mechanical and antibacterial properties [19]. a group of glass fiber filaments were covered with silver nanoparticles and then placed in a solvent of tetrahydrofuran [19]. synthesis of the silver nanoparticles involved combining silver nitrate (𝐴𝑔𝑁𝑂3) and sodium borohydride (𝑁𝑎𝐵𝐻4) at a 3:1 ratio. sodium borohydride acts as a reducing agent for silver nitrate [19]. after 24 hours of stirring and centrifuging, the nanoparticles were dried at room temperature and recovered. mechanical properties of hardness and elastic modulus were evaluated on the surface of optical glass coated with the silver nanoparticles. using the process of nanoindentation, the hardness value of 3.6±0.17 gpa and an elastic modulus of 78.3±2.6 gpa were determined [19]. the results can be seen in figure 1. 3.5 metallic nanomaterials the introduction of tin, copper, mercury, and silver nano powders and composite nano powders, synthesized using salvia miltiorrhiza bunge root extract, play a large role in dental filling antibacterial properties [20]. salvia miltiorrhiza acts as a reducing and capping agent to improve the antibacterial property of dental fillings [20]. metallic nanoparticle properties include small particle size, high surface area to volume ratio, stability, high dispersity, non-cytotoxicity, and biocompatibility that make them beneficial for dental fillings [20]. new and evolving pathogens must be considered when developing dental fillings. failures in restorative dentistry are mostly attributed to the presence of oral bacteria [20]. the copper composite nano powder, salvia miltiorrhiza root extract, and silver nano powder demonstrated strong antibacterial properties against the oral bacteria streptococcus mutans and lactobacillus acidophilus [20]. these two strains of bacteria are some of the most prevalent forms of bacteria in the oral cavity eisenstat et al. (2021): international journal of engineering materials and manufacture, 6(4), 225-241 228 and are the main causes for dental caries [20]. the application of metal nano powders as alternatives for antibiotics and disinfectants in dental filling materials show promising experimental results [20]. figure 1: sem micrographs: (a) synthesized silver nanoparticles by chemical reduction, (b) the optic fiber without silver nanoparticles coated on the surface of glass fiber cores, (c) the optic fiber with silver nanoparticles coated on the surface of glass fiber cores [19] 3.6 dental cement root canals are a common surgery in dentistry. surveys conducted by the american association of endodontists observed that 15.1 million root canal procedures were conducted in 2005 and 2006 respectively [3]. root canals involve the cleaning and removal of an infected tooth nerve followed by the placing of the filling material such as gutta-percha in the canal space. as the infected nerve is removed the subsequent nerve space is filled with dental material to prevent infection. the most common type of filling used for root canal procedures is gutta-percha, a natural resin and thermoplastic elastomer [21,22]. gutta-percha is seen in three different forms. , , or . the form of gutta-percha is dependent on the rate of material cooling. if gutta-percha is cooled at less than half a degree celsius per hour, then  -gutta-percha is formed [23]. gutta-percha observes biological inertness, reversibility and non-conductibility [23]. despite many beneficial properties, there are concerns regarding the ability of gutta-percha’s material to properly secure the root canal [21]. as a result of this, many sealants have been introduced to work with the filling material. however, the non-polar nature of most sealants renders them incompatible with the polar regions of the oral cavity [21]. a comparative review of material properties for current and future dental filling nanomaterials 229 to overcome these drawbacks, new patents for dental cement compositions have been created. dental cement is comprised of various nanoparticles; di-calcium silicate (𝐶𝑎2𝑆𝑖𝑂4), tricalcium silicate (𝐶𝑎3𝑆𝑖𝑂5), bismuth oxide (𝐵𝑖2𝑂3), gypsum, strontium carbonate (𝑆𝑟𝐶𝑂3), zeolite, calcium sulfate (𝐶𝑎𝑆𝑂4) di-sodium hydrogen phosphate (𝑁𝑎2𝐻𝑃𝑂4) and tricalcium aluminate (𝐶𝑎3𝐴𝑙2𝑂6)[21]. dental cement is used as root-end filling material and demonstrates a fast-setting time, despite saliva and blood exposure. dental cement also hardens at temperatures corresponding to bodily ideals at 36.1 to 37.2 degrees celsius [21]. an important feature of dental cement are its microhardness and strength which come as a result of the nanoparticles in chemical solution [21]. for example, the gypsum incorporated into the solution has a chemical formula of 𝐶𝑎𝑆𝑂4 • 2𝐻2𝑂 [24]. the calcium sulfate is primarily known as anhydrite; however, the addition of water molds the material into that of nano-gypsum, which demonstrates significantly higher than normal levels of microhardness [25]. ostewalder et al. conducted an experiment in which the microhardness of nano-gypsum was compared to an alabaster reference which has a similar chemical formula 𝐶𝑎𝑆𝑂4 • 0.25𝐻2𝑂 to that of nano-gypsum at varying powder to water ratios [25]. their findings demonstrated that regardless of the water to powder ratio, the nano-gypsum demonstrated a compelling increase in vickers hardness (kg/𝑚𝑚2), up to approximately 3.18 times as hard as its alabaster reference at a water to powder ratio of 0.22 [25]. 3.7 gutta percha with nano-diamonds nano-diamonds, a type of carbon-based nanoparticles, have been found to have great antibacterial effects against both gram-positive and gram-negative bacteria, as well as s. aureus, e. coli and s. mutans typical bacteria found in the oral cavity [26]. moreover, the addition of nano-diamonds into resin-based materials had improved their antibacterial and properties. the use of gutta-percha was explained previously, however, there is a new and improved form of gutta-percha with nano-diamonds incorporated into the product that is currently undergoing trials by the american government [26]. with this invention, root canal fillers will be more stable, stronger and protect against harmful bacteria more efficiently with the hopes of preventing secondary caries [27]. 4 current nanomaterial dental fillings – a comparison based on current research, the three most currently used nanomaterials in dental fillings carbon nanotubules, silver nanoparticles and silica nanoparticles were assessed in order to determine which application is most optimal. each method of nanomaterial utilization observed their own respective advantages and disadvantages [4]. due to their covalent and hexagonal bonding structures, carbon nanotubules present strong mechanical properties. this includes high strength, low particle densities and heat stability [5]. carbon nanotubules observe strong adhesive properties when applied to cementum and dentin surfaces. unfortunately, carbon nanotubules’ applications in dental fillings have demonstrated cases of adverse biological reactions. reactions have included inflammation of the dental filling areas due to small carbon nanotubule particles crossing over membranes [5]. carbon nanotubes have been shown to demonstrate promising outcomes when combined with composite resins. evidence suggests current composite resins present problems regarding resistance to future caries in dental fillings. this means that in composite resin fillings there exists a high possibility for gaps to be formed between the filling and the tooth, termed as either outer lesions or wall lesions [28]. depending on whether the size of the gap is small or large, either a micro-leak or macro-leak will ensue [28]. these gaps and leaks within the tooth filling can then harbor bacteria leading to secondary caries [29]. due to the antimicrobial properties of carbon nanotubes, their infusion within composite resin materials disrupts bacteria formation within gaps and leaks, generating a preventative effect against tooth decay and development of secondary caries [29]. silver nanomaterial compounds are used largely due to their antibacterial and antimicrobial properties. while relative toxicity of silver nanomaterials is low compared to other dental filling nanomaterials, overall biological risk is larger due to the severity of potential toxic effects. silver can alter dna base pairings; cause dna unwinding and disrupt cellular phagocytosis and actin function [5]. silver oxide nanoparticles were experimented with to determine if they possess antimicrobial properties against streptococcus mutans and lactobacillus [30]. as mentioned previously, these two strains of bacteria are found in oral cavity, resulting in dental caries [31,32]. it was found that composite resins with either silver or zinc-oxide nanoparticles added into the solution demonstrated greater antibacterial activity against both streptococcus mutans and lactobacillus [30]. silica nanomaterials are an inexpensive nanomaterial dental filling alternative, relative to carbon nanotubules and silver nanomaterials. an advantage of incorporating silica nanomaterials is the improved wear resistance that they provide dental fillings [6]. as a dental filling wears, particles are shed from the surface of the dental filling and the tooth roughens [33]. the size of the particles shed are crucial for the composition of the remaining tooth. larger particle shedding can lead to poor tooth filling composition. when traditional dental fillers are used, shed tooth particles are larger, and the shedding of the given particles will result in a rougher filling surface [33]. when nanomaterials are introduced to the filling material, particle shedding has a minimal effect on tooth filling composition due to the small particle size. this leads to less apparent tooth roughness, such as when silica nanomaterials are used [33]. however, due to the small size of silica nanomaterials, there are a few potential health risks involved. silica nanoparticles can cause reactive oxygen species (ros) and additional oxidative stress. as a reference, there were higher amounts of ros, lactate dehydrogenase (ldh), and malondialdehyde reported when eisenstat et al. (2021): international journal of engineering materials and manufacture, 6(4), 225-241 230 treating non-small cell lung cancers or in other words bronchoalveolar carcinoma, with silica nanoparticles at an exposure rate of 10-100µg/ml [34, 35]. dental composites that release a disinfectant called chlorhexidine (chx) have been found to have inferior mechanical properties than composites that do not release chx [36]. however, as mentioned previously, preventing secondary caries are significant when applying dental fillings. therefore, experiments have been conducted to investigate whether the antibacterial chx can be present in the filling without jeopardizing the mechanical properties of the filling. chx is used across the dental field due to its strong antibacterial activity alongside its low cytotoxicity in the oral cavity [36]. sba-15 mesoporous silica nanoparticles (msn) were mixed with chx and then tested for the ejection of chx, the flexural strength and modulus, surface roughness and the antibacterial activity against the same bacteria as mentioned previously, streptococcus mutans and lactobacillus [36]. to test the flexural strength and modulus, varying amounts of chx (3%, 5% and 6.3%) were either mixed with the msn or not mixed with the msn and each mixture was then compared to a control set at times of 24hours and 1 month [36]. based on the results of the experiment, the flexural strength and modulus of the composites containing mixtures of chx with msn were greater for about every level of chx percentage at both twenty-four hours and one month compared to the composites with only chx. this can be visualized in figure 2, as the blue and grey bars (chx and msn) reach higher magnitudes of flexural strength in mpa and flexural modulus in gpa, than the pink and green bars (pure chx) [36]. figure 2: flexural strength and modulus at varying levels of chx percentages for pure chx and chxmsn mixture at both 24 hours and 1 month [36] regarding the release of chx from the composite with respect to time, the composite with the purely chx mixture released the chx at a much more rapid rate at the start, however, very soon later the rate tapered off [36]. the goal for this composite is to have a continuous release of chx to prevent secondary caries. therefore, the composite composed of chx and msn mixture is preferable despite having a slower release rate of chx at the beginning, as it has a more sustainable release of chx over time, as seen in figure 3 [36]. a comparative review of material properties for current and future dental filling nanomaterials 231 figure 3: ejection levels of chx with respect to time for pure and chx-msn mixture [36] in a different study conducted by stewart et al. it was found that utilizing msn allows for improved antimicrobial characteristics [37]. this is yet another study that proves the advantages of incorporating msn into dental fillings, as they facilitate the release of antimicrobial agents more efficiently, ultimately aiding in the prevention of secondary caries [37]. they developed a dental adhesive, which combines the msn and an antibacterial drug called octenidine dihydrochloride [37]. their adhesive demonstrated no biocompatibility issues and performed well against biofilm formation through the controlled release of the octenidine dihydrochloride [37]. to test the surface roughness of the composite, each composite – pure chx and chx-msn mixture, were submerged under water for a two-week period [36]. upon removal from the water, it was evident that the composite with a mixture of chx and msn had displayed much greater wear resistance, which is of prime importance when working with dental fillings. surface roughness is detrimental to a dental filling, as it yields greater wear on the filling [36]. the testing was conducted on composites of 5% chx-msn mixture and 5% pure chx mixture, and the surface roughness’s prior to exposure of water were measured to be 0.344 and 0.311 respectively. however, after the exposure to water the surface roughness for each composite of 5% chx-msn mixture and 5% pure chx mixture were measured to be 0.410 and 1.113 respectively [36]. on the surface of the composite with pure chx, holes reaching further than 5 µm were visible, which can be seen in figure 4 (b). the holes in the 5% chx composite can be attributed to the greater surface roughness of 1.113 [36]. to calculate the percentage difference, the following equation is used: 𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝐷𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 = |𝑁𝑒𝑤𝑉𝑎𝑙𝑢𝑒−𝐼𝑛𝑖𝑡𝑖𝑎𝑙𝑉𝑎𝑙𝑢𝑒| (𝑁𝑒𝑤𝑉𝑎𝑙𝑢𝑒+𝐼𝑛𝑖𝑡𝑖𝑎𝑙𝑉𝑎𝑙𝑢𝑒) 2 ∙ 100% (4) eisenstat et al. (2021): international journal of engineering materials and manufacture, 6(4), 225-241 232 figure 4: illustrations of the surfaces of (a) chx-msn composite, (b) chx mixture composite, (c) surface roughness graphs for chx-msn composite, (d) surface roughness graphs for chx composite [36] through equation 4, better analysis of the change in surface roughness, and thus wear resistance can be made for the different composites of pure chx versus that of chx and msn. it is evident from table 2, that the wear resistance of the composite with the chx and msn mixture is far superior to that of just pure chx, as the chx composite underwent a 112.64 percent increase in surface roughness after being submerged in water for 14 days, compared to the 17.51 percent increase in surface roughness seen by the composite composed of chx and msn. table 2: percentage differences for surface roughness of each composite mixture for before and after exposure to water [36] mixture surface roughness before water (m) surface roughness after water (m) percentage difference (%) chx 0.311 1.113 112.64 chx-msn 0.344 0.410 17.51 experimental trials demonstrate that silica nanoparticle infusion increases the physical properties of composite materials [36]. the addition of silica nanoparticles also demonstrated satisfactory antibacterial properties relative to control groups. in the tests conducted by j.f. zhang et al. there was a significant number of bacteria present in control samples whereas the composite of chx-msn mixture had minimal or no bacteria present [36]. these observations can be attributed to the sustainable and more constant release of chx from the composite with the chx-msn mixture. as a result of this sustainable release of antibacterial chx, there is less time for the bacteria to accumulate on the surface of the filling. there is a need for consistent exposure to antibacterial substances [36]. j.f, zhang et al. demonstrated that a consistent chx release rate of 0.25 to 1.0 µg/ml for the composite consisting of the chx-msn mixture, will drastically lower the risk of bacteria growth and hibernation, and thus lowering the probability of secondary caries [36]. a comparative review of material properties for current and future dental filling nanomaterials 233 based on the findings of current available research, each type of nanoparticle presents various advantages, and all pose similar disadvantages associated with the health risks and toxicity of the nanoparticles. however, amongst the three most used nanomaterial dental fillings carbon nanotubules, silver nanomaterials and silica nanomaterials silica nanomaterials under controlled doses demonstrate the greatest material advantages. silica nanomaterials improve wear resistance, improve physical and mechanical properties, reduce dental filling tooth roughness, improve the antibacterial properties, and are drastically less expensive relative to silver nanomaterials and carbon nanotubules alternatives [5,36]. although there are health risks associated with silica nanomaterials, the same health risks are also present in carbon nanotubules and silver nanomaterials at greater frequency. under controlled concentrations, silica nanomaterials produce minimal adverse effects [5]. table 3: advantages and disadvantages of currently used nanomaterial dental fillings [5,36] nanomaterial type advantages disadvantages carbon nanotubules increased surface area for reactivity molds well with tooth antimicrobial and antibacterial properties potential health risks due to small particle size. potential toxic effects silver antimicrobial and antibacterial properties relatively low toxicity potential health risks due to small particle size potential toxic effects silica inexpensive improved wear resistance antimicrobial and antibacterial properties improved physical and mechanical properties absorption capacity reduces tooth roughness potential health risks due to small particle size 5 future developments of nanomaterial dental filling applications 5.1 graphene family nanomaterials graphene family nanomaterials (gfn) are potential alternatives to current nanomaterials used in dentistry. gfns are comprised of many subclasses of graphene nanomaterials including graphene oxide (go), reduced graphene oxide (rgo), graphene nanosheets (gns), ultra-thin graphite and few layers graphene (flg) respectively [39]. differences between graphene types are attributed to variances in size, layer depth and surface properties as seen in figure 5 [39]. much testing has been done regarding the biocompatibility of gfn. gfn tests have been performed in vivo and in vitro with results observing safe and potentially harmful thresholds of gfn concentration in the body. for graphene oxide, 50 µg/ml was determined to be the hypothetical toxicity threshold [37]. at concentrations over 50 µg/ml, graphene oxide may carry damage to t-cells and fibroblasts [39]. more research still needs to be concluded regarding gfn biocompatibility as no one determinant for toxicity – size, oxidation, iron content, etc. – has been established. the main area of interest regarding the medical and dental uses of gfn are their antibacterial properties. relative to other materials currently being used in prosthodontic procedures, graphene family nanomaterials – specifically graphene oxide – have shown to induce the complete elimination of microbial integrity. when tested against three bacteria commonly found in the oral cavity, streptococcus mutans, porphyromonas gingivalis, and fusobacterium nucleatum, graphene oxide nanosheets at a concentration of 40 µg/ml were observed to be highly effective at inhibiting bacterial growth. antibacterial properties of gfn are however dependent on concentration. by increasing graphene oxide concentration to 80 µg/ml, complete eradication of all streptococcus mutans cultures was observed [39]. for reference, streptococcus mutans is one the bacteria responsible for dental caries as previously mentioned, porphyromonas gingivalis is a bacterium responsible for periodontitis, and fusobacterium nucleatum is a bacterium responsible for root canal infection [39]. in terms of actual application as dental filling agents, gfn are being tested in combination with glass ionomers. glass ionomers are structurally weak relative to other current filling materials. gfns are looked at to reinforce glass ionomer structural properties and improve material strength [39]. additionally, due to the antibacterial properties of gfn, research is being done in order to derive new dental adhesives to be used for filling processes. eisenstat et al. (2021): international journal of engineering materials and manufacture, 6(4), 225-241 234 figure 5: allotropes of carbon nanostructures: (a) 0d fullerenes; (b) 1d carbon nanotubes; (c) 2d graphene; (d) 3d graphite. (e) graphene oxide is synthesized through graphite oxidation [39] 5.2 chitosan nanomaterials chitosan is an organic compound typically found in the exoskeletons of various shellfish [38]. as a nanomaterial, chitosan exhibits many beneficial properties that can be used in dentistry. one of many reasons why chitosan nanoparticle applications are being researched in dentistry is due to the experimental demonstrated effect of induced bone growth in the human body and oral cavity. when titanium implants are coated with chitosan nanoparticles in adjunct with bone growth protein bpm-2, ectopic bone growth was observed in mice [37]. additionally, acceleration of bone regeneration was observed in mice when chitosan nanomaterials were infused with additional protein growth factors. within regenerative dentistry, use of chitosan nanomaterials may offer alternatives to stopgap procedures like dental fillings. chitosan nanoparticles also observe antibacterial properties. antibacterial properties of chitosan nanomaterials are due to its chemical and polyatomic structure, as can be seen in figure 6 [38]. figure 6: chemical composition of chitosan [38] a comparative review of material properties for current and future dental filling nanomaterials 235 researchers are pairing chitosan nanoparticles with various zinc-oxide-eugenol, calcium silicate and epoxy resin sealers, demonstrating improved antimicrobial properties of composite materials as a result. it is important for sealers to exhibit antimicrobial properties, as sealers are typically used for root canal procedures where there is direct exposure to nerve tissue. the exact mechanism for inducing antimicrobial properties in chitosan nanomaterials has yet to be determined. there is speculation as to whether antimicrobial properties of chitosan nanomaterials are a result of direct contact via material-bacterial interaction or via area effect [38]. a study conducted by nair et al. on chitosan nanoparticles (cs-nps) and zinc oxide nanoparticles (zno-nps) against two strains of enterococcus faecalis was used to show antibiofilm efficacy [40]. e. faecalis atcc 29212 and og1rf strains were each tested in five different environments and their average optimal densities were then compared after a 24-hour period [40]. after the 24-hour period, the two strains of e. faecalis atcc 29212 and og1rf, created a biofilm and their biomasses were able to be analyzed using microtiter plate assay with the use of crystal violet [40]. the root canal sealer used in this experiment was apexit plus. group 1 represents apexit plus with zno-nps, group 2 is apexit plus with cs-nps, group 3 was apexit plus by itself, group 4 was a positive control group with no sealers or nanoparticles, and group 5 was a negative, sterile control group. group 1 was found to have the greatest reduction in average optical density in both strains of e. faecalis when compared to the positive control group. however, also group 2, the environment with apexit plus with cs-nps, demonstrated improved antibacterial activity compared to that of group 4, the positive control environment [40]. a second study of confocal laser scanning microscopy (clsm) was also conducted with 1 week old biofilm to observe the antibacterial effectiveness [40]. the two strains of e. faecalis in their same four individual groups, as in the first experiment, were analyzed by their thicknesses. through investigation of atcc 29212 the data showed a significant reduction in thickness of group 1 compared to the other groups. also, once again group 2, the environment with apexit plus with cs-nps, demonstrated improved antibacterial activity compared to that of group 4, the positive control environment for the atcc 29212 strain [40]. however, all groups of og1rf strain had little to no change in their biofilm thickness after 1 week [40]. a third study of the biofilms was conducted using 200 µl of solution from group 1, group 2 and group 3 [40]. they were placed in glass wells and were left for 24 hours at 37 ℃. after the 24-hour period, they were removed from the wells dyed with a propidium iodide stain (which is used to differentiate between living and dead bacterial cells by the colours green and red respectively) and a biofilm was placed on top [40]. these were left to rest for 10 minutes in the dark. it was seen that group 3 with e. faecalis atcc29212 had extreme amounts of living bacterial cells compared to dead bacterial cells. whereas groups 1 and 2 effectively diminished the presence of the two strains at a much higher rate. this is because the thickness notably decreased. group 1, with e. faecalis og1rf, killed many of the bacterial cells. however, the thicknesses in group 1 with e. faecalis og1rf and group 2 with e. faecalis og1rf had not been compromised, meaning that the thickness of e. faecalis og1rf were not influenced by zno-nps or cs-nps [40]. as mentioned previously, the biocompatibility of products looking to be employed in the dental profession are of prime importance in order to protect patients from potential cytotoxic effects. in a study conducted by elgendy et al. chitosan nanoparticles were compared to propolis, a resinous substance that comes from beehives, as well as non-nanosized chitosan nanoparticles [41]. propolis, in recent years, has gained interest in its applicability in restorative dentistry due to its improved antibacterial activity [42]. elgendy et al. proved however through their study, in which dental pulp stem cells were exposed to chitosan nanoparticles, propolis nanoparticles and standard chitosan particles, that the chitosan nanoparticles exhibited the least cytotoxic effects and resulted in the least characteristic cell changes [41]. despite promising bone regenerative and antibacterial properties chitosan nanomaterials are not without their drawbacks. chitosan nanomaterials exhibit weak processing and mechanical properties, as well as complete insolubility in many common organic solvents [38]. researchers are attempting to mitigate these drawbacks by infusing chitosan nanomaterials with various other organic and inorganic nanomaterials. 5.3 zirconia nanomaterials zirconium dioxide (zr𝑂2) zirconia observes a crystalline structure, a melting point of 2,715 ℃, and resembles the colour of healthy teeth [43]. due to these characteristics, zirconia is a sought-after ceramic in the dental industry [44]. its crystalline structure increases its strength, durability, weatherability, and erosion resistance. at high temperatures, stable zirconia permits the free movement of oxygen ions throughout its crystalline structure, increasing electrical conductivity making it a very useful electro-ceramic material [45]. as a chemical oxide, zirconia is insoluble in water decreasing bacterial adhesion [46,47]. using advanced dental technology, three-unit zirconia ceramics show promising results regarding fixed partial dentures (fpd) by computer aided design/computer aided manufacturing (cad/cam) [48]. in vitro experiments determined that zirconia fulfills many of the characteristics considered necessary for dental fillings and dentures [48]. biomedical implementations of zirconium have been increasing over the years and continue to be used throughout the field [49]. eisenstat et al. (2021): international journal of engineering materials and manufacture, 6(4), 225-241 236 figure 7: anatomical crystalline arrangement of zirconia (zro2) [50] 5.4 gold nanoparticles gold nanoparticles are gaining relevance in the field of dental fillings, due to their potential use as inert carriers for medical purposes and since they are harmless, precise, and rigid [51, 52]. elemental gold or its ions, can be absorbed in the gastrointestinal tract. data regarding the oral toxicity of elemental gold is limited [51]. there were tests done on rats using a single dose of 2000 mg nanoparticles/kg of body weight. the lack of information regarding multiple doses has raised concerns [51]. skin rashes have been documented in humans following the ingestion of liquors containing gold. in vitro studies show that gold nanoparticles in mammals induce dna damage [51]. there should be more time and consideration taken to understand the effects of gold nanoparticles, for how frequent they are used in dental fillings. 6 preventative measures against primary or secondary caries prior to dental fillings as mentioned before, the most common problem seen by dental professionals are those of dental caries, which cause dental cavities. however, another major cause for dental appointments are the failures of the presently used dental fillings, whether it be due to mechanical failure or as a result of secondary caries, as previously mentioned. advancements in the biomedical engineering research of nanomaterial based dental fillings is a reactionary solution to the problem. however, there are also potential proactive solutions to dental caries. in other words, there are biomedical applications of nanomaterials, which can prevent the problem of dental caries in the first place. for example, there are developments for a toothbrush with nanomaterials. in between the bristles of the toothbrush, colloidal gold or silver will be placed which can lead to an improvement in dental health and thus a reduction in dental caries [53]. colloidal silver or gold is simply their respective nanoparticles submerged in a solvent [54]. negative phosphate molecules gravitate towards the positively charged silver and gold, which then aids in the destruction of biofilms and/or plaque [53]. 6.1 starch nanoparticles and early diagnosis of caries nanomaterials are now being recognized as a method to limit the need for dental professionals from needing to carry out full dental filling procedures. dental professionals run the risk of overlooking early signs of caries through the use of visual and tactile exam tools [55]. currently, x-ray imaging is a popular method for caries detection, however this requires the caries to be significantly developed, otherwise the x-rays will not detect them [55]. regardless, when operating with these procedures, the solution is to resort to the “drill and fill” method, which is not ideal due to its invasive nature [55]. at the onset of caries development, very small holes begin to develop in the enamel (outer layer) of the tooth. as a result, greenmark, a healthcare start-up, received approval from the food and drug administration agency in march, 2021 for a product called 𝐿𝑢𝑚𝑖𝑐𝑎𝑟𝑒𝑇𝑀caries detection rinse, which utilizes the benefits of starch nanoparticles [55]. molecules within the starch nanoparticles glow in the presence of a luminated blue curing light, as seen in figure 8. a comparative review of material properties for current and future dental filling nanomaterials 237 figure 8: reproduced figure with permission from greenmark biomedical inc illustrating the starch nanoparticles’ ability to fluoresce [55] as summarized in figure 9, a patient will start by rinsing their mouth out with the greenmark rinse, and as they are rinsing, the miniscule starch nanoparticles are able to enter through the tiny porosities in the enamel and then get trapped around the early caries [55]. the patient then rinses their mouth, essentially ridding the oral cavity of all substances other than the starch nanoparticles in the porosities [55]. when the dental professional then shines the blue curing light, the starch nanoparticles then fluoresce, revealing the locations of the early caries, which can then be treated non-invasively [55]. furthermore, greenmark is also developing a product called 𝐶𝑟𝑦𝑠𝑡𝐿𝐶𝑎𝑟𝑒𝑇𝑀 restorative gel, which contains starch nanoparticles bonded with calcium and phosphate, two of the most important minerals that are reduced in concentration during the onset of caries [55]. as mentioned previously, the starch nanoparticles can penetrate through the openings in the enamel and then attach to the developing caries [55]. once all of this takes place, the starch particles disintegrate, thus allowing the now detached calcium and phosphate to re-mineralize the decayed tooth [55]. part of why the use of starch particles is so beneficial is that there is no safety concern due to their biocompatibility and degradability in the oral cavity [55]. figure 9: privately redistributed figure from greenmark biomedical inc explaining the step-by-step procedure of how the 𝐿𝑢𝑚𝑖𝑐𝑎𝑟𝑒𝑇𝑀caries detection rinse works eisenstat et al. (2021): international journal of engineering materials and manufacture, 6(4), 225-241 238 6.2. glycine guided nanoparticles minimal invasive dentistry (mid) is a dental practice where dentists work to preserve original dental tissue. this can include performing early but small cavity fillings, in order to prevent significant future damage to the tooth. dental decay is a result of the hydroxyapatite (hap) mineral ions loss on the enamel. this is known as demineralization [56]. under mid, the primary method used to treat tooth decay is fluoride application. fluoride treatments provide remineralization to the demineralized tooth. there are however drawbacks to fluoride treatment, as mineral ions in fluoride are difficult to maneuver [56]. remineralization treatments should have the same micro-architecture and organization as the original biological mineral crystals. research demonstrated that hap@acp core-shell nanoparticles can be organized just like the original biological mineral crystals. experiments determined that after 48 hours of hap@acp, nanoparticles with gly formed mineral-like enamel crystals [56]. 6.3. nanomaterial toothpastes a japanese study was conducted to investigate the possibility of nanomaterial infused toothpaste. in this study, nanohydroxyapatite particles (nhap) were incorporated into a toothpaste solution [57]. it was observed that the nanoparticles that were infused in the toothpaste significantly increased tooth enamel microhardness relative to toothpaste not infused with nanoparticle solution. experimental trials demonstrated a 56% reduction in cavity formation of nanomaterial infused vs. non-nanomaterial infused toothpastes. [57]. additional experiments were conducted to test the influences on tooth hardness and the remineralization effect using 3% nanosized sodium tri-metaphosphate infused toothpaste [58]. the remineralization effect pertains to the prevention of a caries progressing into a cavity, which is a later stage [59]. it was found that the addition of nanosized sodium tri-metaphosphate had significant influences on both tooth hardness and remineralization. enamel hardness increased by 20% while the remineralization effect of the enamel increased by 66% [58]. there has also been additional research into the use of nanoparticles in mouthwashes, which found that the addition of nano-calcium fluoride reduces the potential for caries [57]. 6.4. silver and calcium phosphate nanoparticle dental adhesives a study was conducted to test the effectiveness of adding silver nanoparticles (nag) and amorphous calcium phosphate nanoparticles (nacp) to an adhesive in breaking down biofilms, remineralization of both the dentin and enamel of the tooth, and the bond strength of the dentin [60]. low percentages of nag were added to the adhesive, while larger percentages of the mass of the adhesive was occupied by the nacp [58]. it was found through this experiment that the additional nanoparticles had a significant positive effect on the antibacterial properties of the adhesive and the remineralization of the dentin and enamel. furthermore, while the dentin bond strength was of prime concern, it was found to not be affected by the additional nanoparticles [60]. 7 conclusions there has been a great deal of research done regarding dental filling nanomaterials and nanoparticles. not one material has proven to have all the beneficial qualities/characteristics desired for the filling. however, there are materials that have stood out as being a better option. as more research is being piloted, more knowledge is available to professionals in the industry, allowing them to give patients the best dental care possible. 1. promising current research regarding dental filling nanomaterial applications involve nanocomposites, dental cement, glycine guided nanoparticles, nanomaterial resins, silica coated nanomaterials, silver coated and other metallic based nanoparticles. 2. of the three most used nanomaterial dental fillers carbon nanotubules, silver nanomaterials and silica nanomaterials silica nanomaterials were observed to be the best current option due to its low cost, improved wear resistance, improved physical and mechanical properties, improved antibacterial properties and comparable toxicity levels under controlled concentrations. 3. the most important properties that were investigated with dental fillings nanomaterials are the resistance to wear, toxicity and the overall biocompatibility of the material. for the biocompatibility of dental filling nanomaterials, several reactive properties were analyzed, those being corrosion by ph, temperature, protein, saliva, oral health conditions, and diet. 4. the current literature on the cytotoxic effects of various nanomaterials is conflicting, and thus more research should be conducted into the safety of introducing nanomaterials into the oral cavity. 5. developmental strides are being made regarding future applications of graphene family nanomaterials (gfn), chitosan nanomaterials and gold nanoparticles for use in dental filling and dental filling processes. 6. starch nanoparticles are currently being utilized to create new products that aid in detection of early caries, as well as treat early caries by recrystallizing of the decayed tooth. 7. innovations regarding cavity prevention via nanoparticle use in toothpastes are being seen. with continued research, nanomaterials offer solutions to dental filling problems not previously available through traditional dental filling materials. a comparative review of material properties for current and future dental filling nanomaterials 239 refernces 1. dental health services in canada. (n.d.). retrieved from https://www.cdaadc.ca/stateoforalhealth/servicescanada/ 2. american dental association (n.d.). retrieved from https://www.ada.org/en/publications/ada-news/2017archive/december/hpi-report-shows-dental-spending-increased-again-in-2016 3. endodontic treatment statistics. (n.d.). retrieved from https://www.aae.org/specialty/about-aae/newsroom/endodontic-treatment-statistics/ 4. maserejian, n., trachtenberg, f., assmann, s., & barregard, l. (2008). dental amalgam exposure and urinary mercury levels in children: the new england children's amalgam trial. environmental health perspectives, 116(2), 256-262. 5. priyadarsini, s., mukherjee, s., & mishra, m. (2018). nanoparticles used in dentistry: a review. journal of oral biology and craniofacial research, 8(1), 58–67. doi: 10.1016/j.jobcr.2017.12.004 6. khurshid, z., zafar, m., qasim, s., shahab, s., naseem, m., & abureqaiba, a. (2015). advances in nanotechnology for restorative dentistry. materials, 8(2), 717–731. doi: 10.3390/ma8020717 7. netto, l. r. c., borges, a. l. s., guimarães, h. b., almeida, e. r. n. d., poskus, l. t., & silva, e. m. d. (2015). marginal integrity of restorations produced with a model composite based on polyhedral oligomeric silsesquioxane (poss). journal of applied oral science, 23(5), 450–458. doi: 10.1590/1678-775720150041 8. manivasagam, geetha & dhinasekaran, durgalakshmi & rajamanickam, asokamani. (2010). biomedical implants: corrosion and its prevention -a review. recent patents on corrosion science. 2. 40-54. 10.2174/1877610801002010040. 9. hasan m. 2020. chapter 9: toxicity and corrosion. slide 4. department of mechanical and industrial engineering. ryerson university, toronto (ontario). 10. royal society of chemistry. (n.d). retrieved from https://www.rsc.org/cpd/teachers/content/filerepository/frg/pdf/nanoparticles.pdf 11. adabi, m., naghibzadeh, m., adabi, m., zarrinfard, m. a., esnaashari, s. s., seifalian, a. m., … ghanbari, h. (2016). biocompatibility and nanostructured materials: applications in nanomedicine. artificial cells, nanomedicine, and biotechnology, 45(4), 833–842. doi: 10.1080/21691401.2016.1178134 12. salim, f. m. (2019). tribological and mechanical characteristics of dental fillings nanocomposites. energy procedia, 157, 512–521. doi: 10.1016/j.egypro.2018.11.215 13. chen, s., yang, j., jia, y., lu, b., & ren, l. (2019). tio2 and peek reinforced 3d printing pmma composite resin for dental denture base applications. nanomaterials, 9(7), 1049. doi:10.3390/nano9071049 14. kamonwanon, p., yodmongkol, s., chantarachindawong, r., thaweeboon, s., thaweeboon, b., & srikhirin, t. (2015). wear resistance of a modified polymethyl methacrylate artificial tooth compared to five commercially available artificial tooth materials. the journal of prosthetic dentistry, 114(2), 286-292. doi:10.1016/j.prosdent.2015.01.013 15. christos angeletakis. minh-dang son nguyen. (2001). us6593395b2 dental composition containing discrete nanoparticles. retrieved from https://patents.google.com/patent/us6593395b2/en 16. cesero, l. d., oliveira, e. m., junior, l. h., papaléo, r. m., & mota, e. g. (2017). the addition of silica nanoparticles on the mechanical properties of dental stone. the journal of prosthetic dentistry, 118(4), 535539. doi:10.1016/j.prosdent.2017.01.001 17. song, j., kong, h., & jang, j. (2009). enhanced antibacterial performance of cationic polymer modified silica nanoparticles. chemical communications, (36), 5418. doi:10.1039/b908060k 18. wang, h., zhu, m., li, y., zhang, q., & wang, h. (2011). mechanical properties of dental resin composites by co-filling diatomite and nanosized silica particles. materials science and engineering: c, 31(3), 600-605. doi:10.1016/j.msec.2010.11.023 19. nevarez-rasconb, a. orrantia-borundaa, e. gonzález-hernándeza, j. flores-gallardoa, s. hurtado-macíasa, a. (1 december 2014). mechanical characterization of optical glass fiber coated with a thin film of silver nanoparticles by nanoindentation. volume 136, pages 63-66. 20. jeong-ho lee. palanivel velmurugan. jung-hee park. kui-jae lee. jong-sik jin. yool-jin park. keuk-soo bang. byung-taek oh. (june 2016). in vitro fabrication of dental filling nanopowder by green route and its antibacterial activity against dental pathogens. volume 159, pages 229-236 21. mohammad ali saghiri. mehrdad lotfi. houtan aghili. (2011). dental cement composition. retrieved from https://patents.google.com/patent/us8668770b2/en 22. drobny, j. g. (2014). thermoplastic elastomers based on recycled rubber and plastics. handbook of thermoplastic elastomers, 297-299. doi:10.1016/b978-0-323-22136-8.00014-4 23. prakash, d. r., gopikrishna, d. v., & kandaswamy, d. d. (n.d.). gutta-percha – an untold story. retrieved from http://medind.nic.in/eaa/t05/i2/eaat05i2p32.pdf 24. authors: john sawyer professor dr. john sawyer is a professor of agronomy and extension specialist in soil fertility and nutrient management at iowa state university. gypsum: an old product with a new use. crops.extension.iastate.edu/encyclopedia/gypsum-old-product-new-use. 25. osterwalder, n., loher, s., grass, r. n., brunner, t. j., limbach, l. k., halim, s. c., & stark, w. j. (2006). preparation of nano-gypsum from anhydrite nanoparticles: strongly increased vickers hardness and formation eisenstat et al. (2021): international journal of engineering materials and manufacture, 6(4), 225-241 240 of calcium sulfate nano-needles. journal of nanoparticle research, 9(2), 275-281. doi:10.1007/s11051-006-91497 26. makvandi, p., gu, j. t., zare, e. n., ashtari, k., moeini, a., tay, f. r., & niu, l. (2019). polymeric and nanoscopical antimicrobial fillers in dentistry. ssrn electronic journal. doi:10.2139/ssrn.3407082 27. nanodiamond-gutta percha composite biomaterials for root canal therapy full text view. (n.d.). retrieved april 16, 2021, from https://clinicaltrials.gov/ct2/show/nct03376984 28. ferracane j. l. (2017). models of caries formation around dental composite restorations. journal of dental research, 96(4), 364–371. https://doi.org/10.1177/0022034516683395 29. bhattacharya, m., & seong, w. (2019). carbon nanotube-based materials—preparation, biocompatibility, and applications in dentistry. nanobiomaterials in clinical dentistry, 41-76. doi:10.1016/b978-0-12-815886 9.00003-6 30. kasraei, s., sami, l., hendi, s., alikhani, m., rezaei-soufi, l., & khamverdi, z. (2014). antibacterial properties of composite resins incorporating silver and zinc oxide nanoparticles onstreptococcus mutansandlactobacillus. restorative dentistry & endodontics, 39(2), 109. doi:10.5395/rde.2014.39.2.109 31. friedman, j. y. (2011). the role of streptococcus mutans in the formation of dental caries: an ecological perspective. the science journal of the lander college of arts and sciences, 5(1). retrieved from https://touroscholar.touro.edu/sjlcas/vol5/iss1/5 32. ahirwar ss, gupta mk and snehi sk: dental caries and lactobacillus: role and ecology in the oral cavity. int j pharm sci & res 2019; 10(11): 4818-29. doi: 10.13040/ijpsr.0975-8232.10(11).4818-29. 33. brian h. (2020). finding the silver lining zoom presentation. kerr restoratives. 34. bahadar, h., maqbool, f., niaz, k., & abdollahi, m. (2016). toxicity of nanoparticles and an overview of current experimental models. iranian biomedical journal, 20(1), 1–11. https://doi.org/10.7508/ibj.2016.01.001 35. chakraborty rk, sharma s. bronchoalveolar cancer. [updated 2021 mar 1]. in: statpearls [internet]. treasure island (fl): statpearls publishing; 2021 jan-. available from: https://www.ncbi.nlm.nih.gov/books/nbk513281/ 36. zhang, j. f., wu, r., fan, y., liao, s., wang, y., wen, z. t., & xu, x. (2014). antibacterial dental composites with chlorhexidine and mesoporous silica. journal of dental research, 93(12), 1283–1289. https://doi.org/10.1177/0022034514555143 37. stewart, c. a., hong, j. h., hatton, b. d., & finer, y. (2018). responsive antimicrobial dental adhesive based on drug-silica co-assembled particles. acta biomaterialia, 76, 283-294. doi:10.1016/j.actbio.2018.06.032 38. virlan, m., miricescu, d., radulescu, r., sabliov, c., totan, a., calenic, b., & greabu, m. (2016). organic nanomaterials and their applications in the treatment of oral diseases. molecules, 21(2), 207. doi:10.3390/molecules21020207 39. ge, z., yang, l., xiao, f., wu, y., yu, t., chen, j., zhang, y. (2018). graphene family nanomaterials: properties and potential applications in dentistry. international journal of biomaterials, 2018, 1–12. doi: 10.1155/2018/1539678 40. nair, n., james, b., devadathan, a., johny, m. k., mathew, j., & jacob, j. (2018). comparative evaluation of antibiofilm efficacy of chitosan nanoparticleand zinc oxide nanoparticle-incorporated calcium hydroxidebased sealer: an in vitro study. contemporary clinical dentistry, 9(3), 434–439. 41. elgendy aa, fayad dm. cell viability and apoptotic changes of dental pulp stem cells treated with propolis, chitosan, and their nano counterparts. tanta dent j 2017;14;198-207 42. abbasi, a. j., mohammadi, f., bayat, m., gema, s. m., ghadirian, h., seifi, h., bayat, h., & bahrami, n. (2018). applications of propolis in dentistry: a review. ethiopian journal of health sciences, 28(4), 505–512. https://doi.org/10.4314/ejhs.v28i4.16 43. piconi c., maccauro g. zirconia as a ceramic biomaterial. biomaterials. 1999;20:1–25 44. nielsen, r. h., & wilfing, g. (2010). zirconium and zirconium compounds. doi:doi:10.1002/14356007.a28_543.pub 45. george, m. (2020). national minerals information center. from https://www.usgs.gov/centers/nmic/zirconium-and-hafnium-statistics-and-information 46. zarone f., russo s., sorrentino r. from porcelain-fused-to-metal to zirconia: clinical and experimental considerations. dent mater j. 2011;27:83–96. 47. lughi v., sergo v. low temperature degradation-aging-of zirconia: a critical review of the relevant aspects in dentistry. dent mater. 2010;26:807–820. 48. vigolo, p., & fonzi, f. (2008). an in vitro evaluation of fit of zirconium‐oxide‐based ceramic four‐unit fixed partial dentures, generated with three different cad/cam systems, before and after porcelain firing cycles and after glaze cycles. journal of prosthodontics, 17(8), 621-626. doi:10.1111/j.1532-849x.2008.00366.x 49. chellan, p., & sadler, p. (2015). the elements of life and medicines. philosophical transactions: mathematical, physical and engineering sciences, 373(2037), 1-56. from http://www.jstor.org/stable/24506181 50. “zirconium dioxide,” wikipedia, 23-jun-2020. [online]. available: https://en.wikipedia.org/wiki/zirconium_dioxide. [accessed: 07-aug-2020]. 51. hadrup, n., sharma, a. k., poulsen, m., & nielsen, e. (2015). toxicological risk assessment of elemental gold following oral exposure to sheets and nanoparticles – a review. regulatory toxicology and pharmacology, 72(2), 216 221. doi:10.1016/j.yrtph.2015.04.017 a comparative review of material properties for current and future dental filling nanomaterials 241 52. carr a.b., brunski j.b., hurley e. effects of fabrication, finishing, and polishing procedures on preload in prostheses using conventional 'gold' and plastic cylinders. int j oral maxillofac implants. 1996:11. 53. c. raval, k. vyas, u. gandhi, b. patel, p. patelnanotechnology in dentistry: a review j. adv. med. dental sci. res., 4 (3) (2016), p. 51 54. nanocomposix. (n.d.). gold colloid. retrieved august 04, 2020, from https://nanocomposix.com/pages/goldcolloid 55. shuman, l. (2020, may). changing the way we see caries literally. oralhealth, 66-66. 56. wang, h., xiao, z., yang, j., lu, d., kishen, a., li, y., zhang, x. (2017). oriented and ordered biomimetic remineralization of the surface of demineralized dental enamel using hap@acp nanoparticles guided by glycine. scientific reports, 7(1), 40701. doi:10.1038/srep40701 57. alkahtani, r. n. (2018). the implications and applications of nanotechnology in dentistry: a review. the saudi dental journal, 30(2), 107-116. doi:10.1016/j.sdentj.2018.01.002 58. m. danelon, j.p. pessan, f.n.s. neto, e.r. de camargo, a.c.b. delbem effect of toothpaste with nano-sized trimetaphosphate on dental caries: in situ study j. dentistry, 43 (7) (2015), pp. 806-813 59. alhamed, m., almalki, f., alselami, a., alotaibi, t., & elkwatehy, w. (2020). effect of different remineralizing agents on the initial carious lesions – a comparative study. the saudi dental journal, 32(8), 390-395. doi:10.1016/j.sdentj.2019.11.001 60. melo, m. a., cheng, l., zhang, k., weir, m. d., rodrigues, l. k., & xu, h. h. (2013). novel dental adhesives containing nanoparticles of silver and amorphous calcium phosphate. dental materials, 29(2), 199-210. doi:10.1016/j.dental.2012.10.005 international journal of engineering materials and manufacture (2018) 3(4) 245-250 https://doi.org/10.26776/ijemm.03.04.2018.09 a. a. s. abbas1 and k. abou-el-hossein2 department of mechatronics nelson mandela university po box 77000, 6031 port elizabeth, south africa 1e-mail: s215038266@mandela.ac.za 2e-mail: khaled.abou-el-hossein@mandela.ac.za reference: abbas, a. a. s. and abou-el-hossein, k. (2018). investigation of the drill bit temperature during automatic bone drilling. international journal of engineering materials and manufacture, 3(4), 245-250. investigation of drill bit temperature during automatic bone drilling abdalla abbas said abbas and khaled abou-el-hossein received: 14 october 2018 accepted: 04 november 2018 published: 01 december 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract bone drilling operations are carried out in hospitals in different surgical operations worldwide (e.g. orthopedic surgeries and fixing bone breakages). it is considered one of the most sensitive processes in biomedical engineering field. during drilling, the most critical problem is the rise in the temperature of the bone above the allowable limit. a study showed that the allowable limit that must not be exceeded is 50oc. moreover, if this limit is exceeded, the bone may sustain serious damage, namely, thermal necrosis (cell death in bone tissue). the research in this paper focuses on reducing the temperature rise during bone drilling. a study was conducted to observe the effect of the drill rotational speed, feed rate and drilling depth on the drill bit temperature during drilling of goat and cow bone. experimental methods were engaged to optimise the drilling parameters in order to achieve an accepted level of drill bit temperature. keywords: bone drilling, temperature, thermal osteonecrosis, drill bit. 1 introduction bone drilling is an important process which is frequently encountered in various medical practices. in curing bone breakage, a drill is used to make a hole through the bone that will be used for the insertion of screws for fixing fractured bone parts. this is considered aiding the broken bones to recover their original location. during the drilling operation, the temperature generated in the bone must not exceed an allowable limit. any increase of the temperature above the allowable limit will lead to thermal osteonecrosis (cell death) [1, 2]. thermal osteonecrosis is known as death of bone cells due to lack of blood flow. it is caused by an extreme increase in the temperature of the bone, which is led by the change of the phosphates alkaline state of the bone. death of bone cells weakens the bone structure and decreases the material stiffness where the drilling procedure is taking place [3]. for bone breakage fixation and reconstructive surgery, weakening the bone structure will lead to the implants loosening and losing their place. augustin et al. [4] rated the implant failure for lower leg osteo synthesis in the range of 2% 7%. while the loosening of bone-implants can be due to several factors, the focus of this paper is on thermal osteonecrosis. the increase in bone temperature and the amount of exposure time to the heat are the two factors that determine the damage level of the bone [4]. much research has been conducted and the following was discovered; thermal osteonecrosis occurs if the temperature of the bone is between 47 °c 50 °c for one minute. if the exposure time is less than or equal to one minute, thermal osteonecrosis effect can be avoided [5]. another study showed that thermal necrosis takes place immediately if the temperature exceeds 70 °c [6]. however, it was revealed by many researchers that the cell death occurs if the temperature increases above 47 °c for more than one minute [7]. there are several parameters that have a direct effect on the increase in temperature during bone drilling, namely, rotational speed, feed rate, drilling tool diameter and drilling depth. vaughn et al. [8] found that an increase in rotational speed leads to an increase in bone temperature. karaca et al. [9] investigated the bone temperature variations during drilling by using a high quality thermocouple. they found that the temperature increased by decreasing the feed rate and compressive force. moreover, the temperature increased with an increase in rotational speed. investigation of drill bit temperature during automatic bone drilling 246 the variations of drill tool diameter effect on the temperature has been widely researched. kalidindi investigated the effect of changing tool diameter on the temperature. the parameters in his setup were three different drill tool diameters of 2, 3.5 and 4.3 mm, rotational speed of 1200 rpm and feed rate of 0.42 mm/s. it was found that the temperature increased exponentially with the increase in drill bit diameter. this paper presents a study result for measuring the drill bit temperature while varying the rotational speed, feed rate and fixing the drill bit diameter. with a purpose of understanding the effect of drilling parameters on the generation of temperature through the drilling operation. a literature review of previous studies is presented in this paper, followed by the setup and experiment for acquiring the temperature values. finally, validations and comparisons are conducted in relation to the literature review. this research is limited to the temperature of the drill tool only due to the poor heat conductivity of the bone. however, an increase in the drill bit temperature will cause the bone temperature to increase as well. 2 review of related work for the last decade, several studies have investigated the effect of different drilling parameters on the temperature of the bone. when investigating the effect of the variations in the rotational speed, matthews et al. investigated the bone drilling of human femur bone, they observed that there is a small change in the bone temperature while varying the rotational speed from 345 to 2900 rpm [10]. tompson [11] stated that there was a major increase in the temperature accompanied with increasing rotational speed from 125 to 2000 rpm. on another study made by sharawy et al.[12] on drilling pig jaw bones, the results showed that the mean temperature increased with varying the rotational speeds from 1225 to 1667 and 2500 rpm. hillery and shuaib [13] presented a study where they proved the existence of a decrease in the temperature with an increase in rotational speed from 400 to 2000 rpm while using a drill bit diameter of 3.2 mm. lee et al. [14] observed that while drilling human femur bone, the rise in temperature is due to the increase in spindle’s speed and the decrease in temperature is due to the increase in feed rate. when investigating the effect of the variations in the drill bit diameter. hufner et al. [15] found that a small diameter and a long length drill bit tends to deviate from its location during the drilling of the bone. another study made by augustin et al. [16] investigating the effect of drill bit diameter on the temperature while drilling into pig bone. they observed that when the drill bit diameter increased, the contact surface area between the bone and drill tool increased, leading to an increase in the temperature of the bone. tahmasbi et al. [17] presented a study to show how varying the drilling parameters affects the variations in temperature during bone drilling procedures. they also developed a solution to optimize the process. their approach was to vary the drill bit diameter from 2.5 to 4 and 5 mm. for each different drill bit diameter, the temperature measurement were taken whilist varying both feed rate and rotational speed of the drill. figure 1 shows the outcome of their investigation for one of the three drill bit diameters due to its relevance to the drill bit diameter used in this paper. figure 1: temperature diagram of feed rate and rotational speed with drill bit diameter of 4 mm [17]. abbas and abou-el-hossein (2018): international journal of engineering materials and manufacture, 3(4), 245-250 247 due to the variety of tests that were conducted by tahmasbi et al. [17], they were able to generate a graph that shows the effect of increasing the drill bit diameter on the temperature. figure 2 shows the variation of tool diameter on the temperature of the bone. where the figure indicates that with an increase in drill bit diameter, the temperature of the bone also increases. it can also be seen that with using a 5 mm drill bit diameter, the temperature of the bone increased remarkably as mentioned in the literature. 3 setup and experiment in this section, the procedure taken in obtaining the temperature of the drill bit and the equipment used is mentioned and discussed briefly. finally, results are discussed and compared to literature review studies. the drilling procedure was carried out by using an automatic smart bone drill that stops the drilling procedure upon breakthrough of the bone and retract to its initial position. figure 3 shows the proposed automatic bone drill system. a k-type thermocouple was used to measure the temperature of the drill bit, a vice was used to secure the bone from any sudden movement. the thermo-couple sensor used can be seen in figure 4, where the temperature measurement was directly taken upon the completion of the drilling procedure. this was achieved by manually using the probe depicted in figure 4 and reading the temperature value shown on the screen. the procedure of the drilling operation starts when the start button is pressed, the automatic drill will carry out the drilling procedure till breakthrough takes place. following that, the drill retracts to its initial position and the thermocouple is then used to measure the temperature of the drill bit tip. several drilling experiments were conducted on goat and cow bone to test out different bone thickness and density while varying the feed rate and rotational drilling speed. the input feed rate was varied from 2 – 10 mm/s and the drilling speed was varied in the range of 2500 to 7500 rpm with incremental intervals of 2500 rpm. figure 2: effect if varying drill bit diameter on temperature. figure 3: smart automatic bone drill device investigation of drill bit temperature during automatic bone drilling 248 the bone used during the drilling procedure was cooked and fixed using a vice, those two points are considered limitations which is a scenario that will not exist in real drilling procedures. those limitations will not allow the experiments to correlate to actual bone drilling procedures. however, it can show the principle of temperature variations due to change in drilling parameters. the first experiment conducted involved using a goat bone of thickness of 3 mm with a feed rate of 3 mm/s and rotational speed of 2500 rpm. the drilling procedure was executed three times in order to measure the average temperature accompanying the specified drilling parameters. table 1 shows the temperature measurements for experiment one. the results obtained shows a small variation in the three tests. however, this can be due to the thermocouple used and the room temperature. experiment two involved use of three different bone thickness in order to understand the effect of the drilling parameters on the temperature. the feed rate used was 3 mm/s with a rotational speed of 2500 rpm. table 2 shows the temperature measurements for experiment 2. the results shown in table 2 highlights that with an increase in the bone thickness, there is a clear increase in the temperature of the drill bit. moreover, the temperature measured when drilling into cow bone was shown to be high. this implies that the temperature of the bone itself is exceptionally high, which can show that for the used drilling parameters and bone thickness of 5.8 mm onwards, the probability of thermal osteonecrosis occurring is high. in experiment three, a cow bone of thickness 7.5 mm was used, the rotational speed was varied from 2500 to 7500 rpm with incremental intervals of 2500 rpm, while fixing the feed rate at 3 mm/s. the drilling procedure was carried out and the temperature of the drill bit tip were recorded. table 1 shows the values of the measured temperature for this experiment. figure 5 shows the effect of increasing the drilling speed on the temperature of the drill bit tip while fixing the feed rate. figure 5 shows the increase of temperature value due to an increase in rotational speed. this statement was investigated in literature and reflected upon in this experiment. the rise in temperature is partially due to increasing the thickness of the bone specimen, extending the drilling time and thus increasing the temperature. experiment four involved fixing the drilling speed at 2000 rpm and increasing the feed rate from 3 to 10 mm/s with incremental increase of 3 mm/s. the bone used was goat bone with thickness of 3 mm. upon the execution of the three drilling procedures, it was noticed that the drilling device stalled during the drilling procedure when using a feed rate of 10 mm/s, leading to an extremely high measured temperature above 70 ℃. a temperature that high for the drill bit means an even higher temperature in the bone, and at these circumstances thermal osteonecrosis cannot be avoided. therefore, an increase in feed rate while keeping the rotational speed fixed at a low value can lead to high elevation in temperature. figure 6 shows the outcome of experiment four. figure 4: thermocouple sensor arrangement abbas and abou-el-hossein (2018): international journal of engineering materials and manufacture, 3(4), 245-250 249 table 1: temperature measurements for experiment 1 tests temperature °c test 1 28 test 2 29 test 3 28.5 table 2: temperature measurements for experiment 2 bone type thickness (mm) temperature °c goat 3 28 goat 3.5 31 cow 5.86 40 figure 5: effect of rotational speed on the temperature. figure 6: effect of increasing feed rate and fixing rotational speed at 2000 rpm investigation of drill bit temperature during automatic bone drilling 250 4 conclusions in this study testing the effective drilling parameters on the temperature of the drill bit was presented using a thermocouple and a developed smart automatic drilling device. previous research was mentioned in the literature reviewed in order to draw a guideline and a common understanding of the effect of high temperatures on the bone. this study showed: • the temperature increases as the thickness of the bone increases. a speed of 2500 rpm and feed rate of 3 mm/s while drilling into goat bone of 3 mm thickness has proved to yield the least generated temperature. this confirmed what was mentioned in the literature reviewed. • improving the measurement method is necessary in future work in order to measure the bone temperature accurately, to meet the real requirement for bone drilling operations and to achieve the optimal technique for bone drilling while adhering to the safety rules. acknowledgement the authors would like to acknowledge the support of the mechatronics department of nelson mandela university for the financial support. references 1. r. eriksson, t. albrektsson, and b. magnusson, "assessment of bone viability after heat trauma: a histological, histochemical and vital microscopic study in the rabbit," scandinavian journal of plastic and reconstructive surgery, vol. 18, pp. 261-268, 1984. 2. j. lundskog, "heat and bone tissue. an experimental investigation of the thermal properties of bone and threshold levels for thermal injury," scand j plast reconstr surg, vol. 9, pp. 72-74, 1972. 3. k. n. bachus, m. t. rondina, and d. t. hutchinson, "the effects of drilling force on cortical temperatures and their duration: an in vitro study," medical engineering & physics, vol. 22, pp. 685-691, 2000. 4. a. eriksson and t. albrektsson, "temperature threshold levels for heat-induced bone tissue injury: a vitalmicroscopic study in the rabbit," journal of prosthetic dentistry, vol. 50, pp. 101-107, 1983. 5. r. eriksson and t. albrektsson, "the effect of heat on bone regeneration: an experimental study in the rabbit using the bone growth chamber," journal of oral and maxillofacial surgery, vol. 42, pp. 705-711, 1984. 6. a. r. moritz and f. henriques jr, "studies of thermal injury: ii. the relative importance of time and surface temperature in the causation of cutaneous burns," the american journal of pathology, vol. 23, p. 695, 1947. 7. r. k. pandey and s. panda, "drilling of bone: a comprehensive review," journal of clinical orthopaedics and trauma, vol. 4, pp. 15-30, 2013. 8. r. vaughn and f. peyton, "the influence of rotational speed on temperature rise during cavity preparation," journal of dental research, vol. 30, pp. 737-744, 1951. 9. f. karaca and b. aksakal, "effects of various drilling parameters on bone during implantology: an in vitro experimental study," acta of bioengineering and biomechanics, vol. 15, 2013. 10. l. s. matthews and c. hirsch, "temperatures measured in human cortical bone when drilling," jbjs, vol. 54, pp. 297-308, 1972. 11. h. thompson, "effect of drilling into bone," journal of oral surgery, vol. 16, pp. 22-30, 1958. 12. m. sharawy, c. e. misch, n. weller, and s. tehemar, "heat generation during implant drilling: the significance of motor speed," journal of oral and maxillofacial surgery, vol. 60, pp. 1160-1169, 2002. 13. m. t. hillery and i. shuaib, "temperature effects in the drilling of human and bovine bone," journal of materials processing technology, vol. 92, pp. 302-308, 1999. 14. j. lee, o. b. ozdoganlar, and y. rabin, "an experimental investigation on thermal exposure during bone drilling," medical engineering & physics, vol. 34, pp. 1510-1520, 2012. 15. t. hüfner, j. geerling, g. oldag, m. richter, m. kfuri jr, t. pohlemann, "accuracy study of computer-assisted drilling: the effect of bone density, drill bit characteristics, and use of a mechanical guide," journal of orthopaedic trauma, vol. 19, pp. 317-322, 2005. 16. g. augustin, s. davila, k. mihoci, t. udiljak, d. s. vedrina, and a. antabak, "thermal osteonecrosis and bone drilling parameters revisited," archives of orthopaedic and trauma surgery, vol. 128, pp. 71-77, 2008. 17. v. tahmasbi, m. ghoreshi, and m. zolfaghari, "temperature in bone drilling process: mathematical modeling and optimization of effective parameters," international journal of engineering-transactions a: basics, vol. 29, pp. 946-953, 2016. international journal of engineering materials and manufacture (2019) 4(1) 22-26 https://doi.org/10.26776/ijemm.04.01.2019.03 t. s. ogedengbe department of mechanical and automotive engineering elizade university, ilara-mokin ondo state, nigeria e-mail: temitayo.ogedengbe@elizadeuniversity.edu.ng reference: ogedengbe, t. s. (2019). sustainable machining processes through optimization of process parameters. international journal of engineering materials and manufacture, 4(1), 22-26. sustainable machining processes through optimization of process parameters ogedengbe temitayo samson received: 05 november 2018 accepted: 24 december 2018 published: 01 march 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract machining processes are a vital part of manufacturing activities in major industries that contributes to the growth of the economy. they mostly require high amount of electrical energy to power the various support modules installed on machine tools. carrying out machining activities with a view to reducing energy consumption will therefore result in a lowered cost of production for manufactured products. previous studies on some energy-saving methods adopted by researchers and the limitations faced in the reduction of energy consumption have been discussed. in this work, the effect of process parameters in the conservation of energy during machining processes was experimented. minitab 16 was used to design the experiment and a 9-run orthogonal array was generated. the machining parameters were cutting speed (80 – 120 m/min), feed (0.05 – 0.07 mm/rev) and depth of cut (0.1 – 0.3 mm). a high carbon steel bar was machined using high speed steel tool and the energy consumed during the machining process was measured. energy (28.67 kw/hr) was consumed during machining at 0.005 mm/rev and 0.3 m. energy (12.83 kw/hr) was consumed while machining at 0.07 mm/rev and 0.1 m. the energy consumed changed with machining parameters. these results showed that much energy could be saved by optimizing parameters before machining. keywords: energy consumption, machine tools, machining processes, parameters 1 introduction the manufacturing sector comprises some of the largest energy consumers worldwide [1]. over 60% of the energy consumed in the industries is accounted for by manufacturing industries [2]. these industries basically use electric power for the transformation of materials into products [3]. hence, they require a large amount of electrical energy which increases the cost of production for such companies. therefore, companies have to identify ways to reduce the energy consumed during manufacturing of a given product so as to continue to produce especially at reduced cost [4]. the reduction in cost has largely been the driver for recent studies on energy reduction in the manufacturing sector for the development of more energy-efficient machining processes [5; 6]. machining is one of the most fundamental and important manufacturing processes that is widely used in manufacturing industries [1,7]. machining is the process of cutting a material into a desired shape and size using a controlled material-removal process [8]. recent non-conventional machining processes make use of computer numerical control (cnc) machines to fabricate parts [8]. nc machines control the movements of machine tools through direct insertion of coded instructions into the system as numbers and letters [9]. it is therefore important to note that nc machining plays an important role in the metal-cutting industry. however, metal cutting consumes a large amount of energy which can be attributed to the process of material removal and also to the various components that contributes to the efficient operation of the machine tool [10]. energy conservation during machining processes has become of more interest to researchers recently. this is because the conservation of energy during machining which is a key element of manufacturing processes will bring about lower costs of products. a reduction in cost of product will result in greater productivity. there is therefore a need to study the possibility of conservation of energy during machining to ensure an increase in profit margins of production companies. energy demand of a machine tool can be categorized into two broad groups, namely, constant energy components and variable energy components [4]. where the constant components (i.e fans, lightings computer system etc.) consume a constant amount of energy which does not depend on the process parameter selected, the variable components largely depend on the process parameter selected. some of the studies sustainable machining processes through optimization of process parameters 23 on energy conservation during machining are hereafter discussed. a study on automated monitoring of machine tools specifically analysing the energy consumption of the machines has been done [11]. it was reported that process control was a key factor for energy consumption. a study on the possible improvements in energy efficiency of machine tools with diamond-like carbon (dlc) deposited tools has been carried out [12]. results showed that the method was able to reduce the cutting power consumption of the machine by 36%. the optimization of machining processes from the perspective of energy consumption has also been attempted [13]. it was opined that machining parameters, cutting tools and workpiece materials influence the rate of energy consumption during machining processes. there is a need to further consider the possibility of a conservation of energy through the optimization of process parameters. this work is therefore an attempt to conserve energy by reduction of the energy consumed during machining processes. 2 methodology 2.1 machine and tools the experiment was carried out on a colchester triumph model 2000 conventional lathe machine with a 3-jaw chuck as shown in figure 1. the workpiece material was a high carbon steel bar and the tool used for the experiment was high speed steel (hss). the choice of high carbon steel was informed by the higher difficulty in machining the steel as compared to other materials (e.g. mild steel) used in fabrication of parts. hss was selected because it was cheaper and easily accessible compared to other tools. the surface roughness was measured with a profilometer while the power consumed was measured using multimeters. 2.2 experimental procedure the workpiece used for this experiment was a high carbon steel material. table 1 shows the result of the compositional analysis for the workpiece material. figure 2 shows the set up for the experimental process carried out on the lathe machine. the process parameters used for the experiment as given in table 2 were cutting speed, feed rate and depth of cut. the process parameters were selected based on literature and machine constraints. a low feed was used to ensure a longer period of machining to sufficiently measure energy consumed. taguchi orthogonal array from minitab 16 software was used to design the experiment resulting in a 9–experimental run mix with the three factors. the smaller-is-better design option was adopted in the analysis of signal-to-noise (sn) ratio for the energy consumed during machining process as recommended by [14]. the energy consumed during the machining process was measured with the use of multi-meters connected in series and parallel to capture the current and voltage respectively. the resulting values where thereafter used to compute the energy consumed using equations 1 and 2. 𝑃𝑜𝑤𝑒𝑟 = √3 𝑉𝑙 (1) 𝐸𝑛𝑒𝑟𝑔𝑦 𝐶𝑜𝑛𝑠𝑢𝑚𝑒𝑑 = 𝑃𝑜𝑤𝑒𝑟 𝑥 𝑇𝑖𝑚𝑒 (2) table 1: chemical composition of high carbon steel sample s/n element % composition 1 fe 98.07 2 si 0.510 3 cr 0.054 4 s 0.045 5 p 0.032 6 sb 0.0008 7 nb 0.0013 8 w 0.0032 9 v 0.0007 10 mo 0.022 11 mn 0.65 12 c 0.54 13 ni 0.024 14 pb 0.0016 15 cu 0.060 16 ti 0.0009 ogedengbe (2019): international journal of engineering materials and manufacture, 4(1), 22-26 24 figure 1: colchester lathe machine and hss tool figure 2: experimental set-up table 2: machining parameters for experiments factor level 1 2 3 speed (m/min) 80 100 120 feed rate(mm/rev) 0.05 0.06 0.07 depth of cut (mm) 0.1 0.2 0.3 table 3: orthogonal array for machining experiment run machining parametrs speed (m/min) feed (mm/min) doc (mm) 1 80 0.05 0.1 2 80 0.06 0.2 3 80 0.07 0.3 4 100 0.05 0.2 5 100 0.06 0.3 6 100 0.07 0.1 7 120 0.05 0.3 8 120 0.06 0.1 9 120 0.07 0.2 sustainable machining processes through optimization of process parameters 25 3 results and discussions the result gotten after the machining is as shown in figure 4. the highest amount of energy was consumed (28.67kw/hr) during run 7 at a low feed rate of 0.05mm/min and a high depth of cut of 0.3m. the lowest energy consumption (12.83kw/hr) was also recorded at run 6 with feed rate and depth of cut of 0.07mm/min and 0.1mm respectively. also, as shown in figure 6, at values of highest speed of 120m/min and highest feed rate of 0.07mm/min obtained at run 9 with a mrr of 488,850.82mm 3 /min, a very low amount of energy was consumed. these results agree with [15]. the analysis of the s/n ratio as shown in figure 5 indicates that at higher values of cutting speed, the average s/n ratio is higher which is preferable. the analysis also indicates that a higher cutting speed resulted in a higher energy consumption. however, depth of cut and feed rate did not contribute significantly to the consumption of energy. figure 4: energy consumed during runs figure 5: signal-to-noise analysis for parameters. figure 6: mrr and energy consumed analysis during machining. ogedengbe (2019): international journal of engineering materials and manufacture, 4(1), 22-26 26 4 conclusions the aim of this study was to optimize process parameters for conservation of energy. the following conclusions have been reached from the results and findings after the study. • at highest machining speed (120m/min), lowest energy is consumed. • depth of cut has no significant effect on rate of consumption of energy during machining. • energy can be conserved by the optimization of process parameters during machining. acknowledgement the authors are grateful for generous support from the central engineering workshop, university of ilorin, kwara state, nigeria and central engineering laboratory/workshop, elizade university, ilara-mokin, ondo state, nigeria where this research was been conducted. references 1. moradnazhad m. and unver h.o. (2016), energy efficiency of machining operations: a review, proceedings of institution of mechanical engineers, part b journal of engineering manufacture 231(11). doi: 10.1177/0954405415619345 2. zhou lr, li jf and li fy (2016), energy consumption model and energy efficiency of machine tools: a comprehensive literature review. j clean prod; 112: 3721–3734. 3. arif m., ian a. s. and olcay a. (2014), a model to determine the optimal parameters in a machining process for the most profitable utilization of machining energy, proceedings of the institution of mechanical engineers, part b: journal of engineering manufacture, doi: 10.1177/0954405414527960 4. diaz n, helu m, jarvis a (2009), strategies for minimum energy operation for precision machining. in: proceedings of the machine tool technologies research foundation (mttrf) annual meeting, shanghai, china. 5. fang k., uhan n., zhao f. (2011), a new shop scheduling approach in support of sustainable manufacturing. in: proceedings of the 18th cirp international conference on life cycle engineering, technische universita¨ t braunschweig, braunschweig, germany, pp. 305–310. 6. duflou j.r, sutherland j.w, dornfeld d (2012), towards energy and resource efficient manufacturing: a processes and systems approach. cirp ann: manufacturing technology; 61: 587–609. 7. ogedengbe t. s., abdulkareem s., aweda j. o. (2018), effect of coolant temperature on machining characteristics of high carbon steel, covenant journal of engineering technology (special edition), vol 1, no 1, available at https://journals.covenantuniversity.edu.ng/index.php/cjetse/article/view/812 8. abdulkareem s., ogedengbe t.s., aweda j.o, khan a.a (2017), comparative analysis of aisi 1050 steel using n5-soluble oil and arachis oil in metal cutting operation, proceedings of the 30th agm and international conference of the nigerian institution for mechanical engineers. 9. kalpakjian, s. and schmid, s. manufacturing engineering and technology, (1999) (addison-wesley publishing company, boston, massachusetts). 10. he y., liu f., wu t., zhong f-p, and peng b. (2010), analysis and estimation of energy consumption for numerical control machining, proceedings of nimeche vol. 226 part b: j. engineering manufacture. doi: 10.1177/0954405411417673 11. vijayaraghavan, a., dornfeld, d., (2010). automated energy monitoring of machine tools. cirp annals manufacturing technology 59, pp. 21-24. 12. zolgharni, m., jones, b.j., bulpett, r., anson, a.w. and franks, j., (2008), energy efficiency improvements in dry drilling with optimised diamond-like carbon coatings, diamond & related materials, 17:1733–1737. 13. bi z. m. and wang l. (2012), optimization of machining processes from perspective of energy consumption: a case study, journal of manufacturing systems 31, 420– 428, dx.doi.org/10.1016/j.jmsy.2012.07.002. 14. xin q. (2011), diesel engine system design. cambridge: woodhead publishing, pp.212–217. 15. shokrani a., dhokia v., newman s.t. (2016), energy conscious cryogenic machining of ti-6al-4v titanium alloy, proc imeche part b: j engineering manufacture 1–17, imeche, doi: 10.1177/0954405416668923. 16. gutowski t., dahmus j. and thiriez a. (2006), electrical energy requirements for manufacturing processes. in: duflou jr(ed) proceedings of the 13th cirp conference on life cycle engineering (lce 2006), pp.623–627. available at: http://www.mech.kuleu ven.be/ lce2006/071.pdf. international journal of engineering materials and manufacture (2018) 3(1) 32-40 https://doi.org/10.26776/ijemm.03.01.2018.04 i. f. bourini 1 , m. h. a. f. hazza 2 , and h. t. assem 2 1 college of business administration al falah university po box 128821, dubai, united arab emirates e-mail: islam.bourini@afu.ac.ae 2 department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: muataz@iium.edu.my reference: bourini, i. f., muataz, h. a. f. and assem, h. t. (2018). investigation of effect of machine layout on productivity and utilization level: what if simulation approach. international journal of engineering materials and manufacture, 3(1), 32-40. investigation of effect of machine layout on productivity and utilization level: what if simulation approach islam f. bourini, muataz hazza f. al hazza and assem hatem taha received: 13 march 2018 accepted: 27 march 2018 published: 30 march 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract designing and selecting the material handling system is a vital factor for any production line, and as result for the whole manufacturing system. poor design and unsuitable handling equipment may increase the risk of having bottlenecks, longer production time and as a result the higher total production cost. one of the useful and effective tools are using “what if” simulation techniques. however, this technique needs effective simulation software. the main objective for this research is to simulate different types of handling system using what if scenario. to achieve the objective of the research, delmia quest software has been used to simulate two different systems: manual system and conveyers system for the same production line and analyses the differences in terms of utilization and production rate. the results obtained have been analysed and appraised to induce the bottleneck locations, productivity and utilizations of the machines and material handling systems used in the design system. finally, the best model have been developed to increase the productivity, utilizations of the machines, material handling systems and to minimize the bottleneck locations. keywords: handling systems, what if simulation, productivity, utilization, delmia quest 1 introduction organizations now days are struggling to increase quality and productivity level while reducing costs associated with production process [1]. one of the essentials parts of the production process is material handling system which considers as critical stage in design process of a manufacturing facility. facilities layout of manufacturing has received attention where it has an essential role in manufacturing productivity in terms of cost and time [2]. poor selection of material handling system will lead to poor utilization of labour, increase the number of final product, enhance the production process, and possibly increasing the system's flexibility [3][4]. in addition to that, a balanced utilization will reduce the risk of having bottlenecks in the manufacturing system. mohsen & hassan [5] claimed that a well-designed material handling system "would improve the logistics facilities and their productivity, enhance quality of products, and reduce production" costs. there are different techniques and methods to decide and select the best and optimal material handling systems for each individual production line. however, one of the most common methods used is by simulation due to the easiness especially with the availability of new advanced software such as delmia and delmia quest. simulation studies had been used broadly to gain a clear view of the production process before implementing the decision regarding layout and machines handling. many researchers used different types of simulation to improve and modelling the material handling systems and enhancing manufacturing system by taking critical decisions such as [6][7]. investigation of effect of machine layout on productivity and utilization level: what if simulation approach 33 narsingh [8] said that simulation environments helped the industries in simulating and understanding the behaviour of the new decisions before implementing it. this will decrease the risk of investment; reduce the risk of lost, shortage and bottle nick issues. the new software gives the decision makers the knowledge in evaluating analysing the effectiveness and check the performance of the material handling systems of a factory. the simulation gives the possibility to enhance and improve the factory layout and offers the opportunity to create" an innovative environment. one of the common used software for designing simulations of manufacturing system is the delmia quest software. the software is 3d discrete simulation software used for simulating discrete events in manufacturing processes. it provides simulation environment based on the delivery of materials, processing and storage [9. it contains material element for rapid modelling such as machine tool, treatment process, failure rate, maintenance, operator, path and material export, which can help users simulate and analyse the process flow in 3d factory environment [10]. however, many researchers have used the simulation to evaluate and improve the facility layout in order to improve the productivity using different techniques. in this research a simulation based method using delmia quest software have been used to analyses the effect of facility layout and the type of handling system on the productivity and utilization level. 2 what if simulation in this research, what if simulation approach has been used to study the effect of factory layout and material handling system type using one of the advanced discrete events simulation software’s: delmia quest. golfarelli and rizzi [11] claim that (what-if analysis) can help the decision makers to simulate and inspect the behaviour of a complex system before any critical decision using past data as well any available data to reduce the risk for any un expected results. the new development of advanced software for modelling and simulating discrete events in manufacturing gives the opportunity to the decision makers in industry to evaluate, analyse and take the suitable actions to improve their systems in productions line. one of the most important systems to the manufacturer is the material handling systems. an effective and suitable handling system will lead to decrease the bottlenecks in production line, reducing the transportation cost for semi-finished parts and as result improve the smoothness of flow inside the production area. therefore, implementation of different scenarios on designed case in manufacturing in order to investigate and highlights the important of what-if simulation in improving the material handling system and the facility layout. in this research different factors have been considered: cycle time, types of machines, two different handling systems and different types of facility layout. all scenarios considered the flow of the production, starting from the raw material to the final product. to achieve the objectives of the research different steps have been conducted. figure 1 concluded the research methodology. figure 1: research methodology flow chart bourini, muataz and assem (2018): international journal of engineering materials and manufacture, 3(1), 32-40 34 a case study has been designed to evaluate and highlighted of the importance factory layout and material handling systems type in reducing the bottlenecks and increasing productivity. the final product needs to be machined in different types of processes as shown in figure 2. this figure shows two sources of raw materials (s1-s2) need to pass through 10 different machines (m1-m10). the line also contains two buffers b1-b2). the first and second scenarios are using manual and automated handling system respectively. 3 results and discussions to investigate the effect of machine layout on productivity and utilization level a delmia quest simulation technique implemented and the results obtained show improvement on the production process. particularly, significant enhancement for the production line through improving the average production rate of labour from 67 per hour to 85 per hour in the conveyers’ system. however, the proposed model shows an increasing of production rate up to 148 parts per hour. in figure 3 shows a manual handling system by using labour in the production line. figure 2: design of the production line (m: machine; s: source; b: buffer) figure 3: manual handling system investigation of effect of machine layout on productivity and utilization level: what if simulation approach 35 after running the simulation the utilization for each machine and production rate have been concluded in table 1 and table 2. which show seven machines used in the production line and 5 labours for handling parts. the utilization and the total distant movement for each labour is concluded in table 2 from both tables 1 and 2 it was clear that the average utilization for all machines is below 50% except machine 3, where the utilization is about 78%. on the other hand the labour utilization are also have the same values below the 50% except labour 1, where the utilization is about 75%. figure 4 shows the utilization of the different labours. second scenario is by adopting automation approach for the same design which will use conveyer instead of using labours for the same design and same sequence a as shown in figure 5. after running the simulation the utilization for each machine and production rate have been concluded in table 3. the utilization of each conveyer is concluded in table 4. table 1: utilization and production rate for the manual handling system name utilization (%) production rate machine1_1 40.556 72 machine2_1 30.278 72 machine3_1 79.167 71 machine4_1 23.393 70 machine5_1 44.722 70 machine6_1_1 24.306 35 machine6_2_1 24.087 34 machine7_1_1 15.111 34 machine7_2_1 15.111 34 machine6_1 26.444 68 table 2: utilization, parts transferred, and distance travelled for the manual system name utilization (%) no. of parts added distance travelled labor1_1 75.039 72 664736.6 labor2_1 34.988 71 674819.6 labor3_1 44.814 35 266559.8 labor4_1 43.778 34 267343.7 labor5_1 33.596 68 651793.5 figure 4: utilization of labours 0 10 20 30 40 50 60 70 80 labor1_1 labor2_1 labor3_1 labor4_1 labor5_1 u ti li za ti o n % labours bourini, muataz and assem (2018): international journal of engineering materials and manufacture, 3(1), 32-40 36 figure 5: conveyers handling system table 3: utilization and production rate for the conveyer’s system name utilization (%) production rate machine1_1 50.889 91 machine2_1 37.833 90 machine3_1 99.222 89 machine4_1 29.389 88 machine5_1 56.222 88 machine6_1_1 30.556 44 machine6_2_1 30.056 43 machine7_1_1 19.222 43 machine7_2_1 19.111 43 machine6_1 33.444 86 table 4: utilization of conveyer system name utilization (%) transport rate conveyor1_1 99.111 90 conveyor2_1 24.722 89 conveyor3_1 22 44 conveyor4_1 21.5 43 conveyor5_1 47.611 85 investigation of effect of machine layout on productivity and utilization level: what if simulation approach 37 from table 3 and table 4 it can be concluded that the utilization of all machines have be increased. however, it can be mentioned that machine 3 shows about 99% of utilization, which indicate a bottleneck in the production system. moreover, the utilization of the conveyer that feeds to the machine 3 show as well 99% of utilization. the utilization of both manual and conveyers are compared in figure 6. to improve the production system productivity and eliminate the bottleneck a new scenario has been proposed by adding a new machine and conveyer to enhance the production rate and to avoid any bottlenecks issue as shown in figure 7. figure 6: comparison of utilization figure 7: proposed system 0 20 40 60 80 100 120 u ti li za ti o n % machine utilization ( % ) manual handiling system utilization ( % ) in conveyer system bourini, muataz and assem (2018): international journal of engineering materials and manufacture, 3(1), 32-40 38 after running the simulation, the results were concluded in table 5. where it show that machine 3 shows about 87% of utilization, which indicate no more bottleneck in the production system. moreover, the utilization of the conveyer that feeds to the machine 3 show as well 92% of utilization. the utilization and the transport rate was concluded in table 6. from the results, it was found the proposed system show a high production rate compared as shown in figure 8. where at the first scenario with manual handling system the production rate per hour was approximate 52 unit, in the second scenario with conveyers show improvement in the production rate and increase utilization level for some machine and conveyers as consequence of the in-bottleneck issues where led to propose a solution of add extra conveyer and handling machine to reduce the utilization and bottleneck. table 5: utilization and production rate for the proposed system (fig. 7) name utilization (%) production rate machine1_1 88.722 159 machine2_1 65.806 157 machine3_1 87.056 78 machine4_1 51.333 154 machine5_1 97.5 152 machine6_1_1 52.778 76 machine6_2_1 52.472 75 machine7_1_1 33.333 75 machine7_2_1 33.333 75 machine6_1 57.972 149 machine7_1 86.583 77 table 6: utilization and transport rate for the proposed system (fig 7) name utilization (%) transport rate conveyor1_1 92.167 79 conveyor2_1 96.5 154 conveyor3_1 37.833 75 conveyor4_1 37.5 75 conveyor5_1 82.5 148 conveyor1_2_1 92.083 78 investigation of effect of machine layout on productivity and utilization level: what if simulation approach 39 figure 8: production rate for the three different scenarios 4 conclusions what if simulation approach using delmia quest software is found to be suitable to simulate the manufacturing process with consistency [17]. in this research the results of different scenarios using delmia quest software were analysed. it was found that a significant enhancement for the production line through improving the average production rate of labour from 67 per hour to 85 per hour in the conveyers system. moreover, the proposed model showed an increase in production rate of up to 148 part per hour. finally, it can be concluded that the “what if” simulation approach in delmia quest software have resulted the followings:  reducing the total distance of movement for labours,  reducing number of labours,  increasing the number of final products,  determine the bottleneck based on buffer size, and eventually  all these achievements are to minimize the cost related to the production process. moreover, what if simulation can be used for any discrete event model to improve and detect the weakness in that model, reduce the required time to implement real life model as well as reduce the related expenses such as purchasing new handling system hardware and hire more employees. moreover, decision makers in operation can reduce the risk associated with decision of handling system. however, the limitation of this improvement was the high cost of changing the handling system and cost associated with delmia quest purchase which consider costly. however, from the productivity point of view, the investment of changing the handling system become a need to survive in the market. particularly, replacing or updating the handling system will gain organization competitive advantage in regards of quality, time required, productivity and utilization. references [1] roriz, c., nunes, e., & sousa, s. (2017). application of lean production principles and tools for quality improvement of production processes in a carton company. procedia manufacturing, 11, 1069-1076. [2] shafigh, f., defersha, f. m., & moussa, s. e. (2017). a linear programming embedded simulated annealing in the design of distributed layout with production planning and systems reconfiguration. the international journal of advanced manufacturing technology, 88 (1-4), 1119-1140. [3] chan, f. t. s. (2002). design of material handling equipment selection system: an integration of expert system with analytic hierarchy process approach. integrated manufacturing systems, 13 (1), 58-68. [4] dongre, a., and mohite, n. y. (2015). significance of selection of material handling system design in industry-a review. international journal of engineering research and general science, 3, 76–79. [5] mohsen, & hassan, m. d. (2010). a framework for selection of material handling equipment in manufacturing and logistics facilities. journal of manufacturing technology management,21 (2), 246-268. [6] lin, j. t., & huang, c. j. (2014). a simulation-based optimization approach for a semiconductor photobay with automated material handling system. simulation modelling practice and theory, 46, 76-100. [7] ezema, c. n., okafor, e. c., & okezie, c. c. (2016). industrial design and simulation of a jit material handling system. european journal of engineering research and science, 1 (6), 52-57. [8] narsingh, d. (2006). system simulation with digital computer. prentice hall private limited. new delhi, india. 0 20 40 60 80 100 120 140 160 manual conveyers improvent p ro d u ct io n r a te p e r h o u r different scenarios bourini, muataz and assem (2018): international journal of engineering materials and manufacture, 3(1), 32-40 40 [9] lu, h., liu, x., pang, w., ye, w. h., & wei, b. s. (2012). modeling and simulation of aircraft k line based on quest. advanced materials research, 569, 666-669. [10] gingu, e. i., zapciu, m., & sindile, m. (2014). balancing of production line using discrete event simulation model. proceedings in manufacturing systems, 9 (4), 227-232. [11] golfarelli, m., & rizzi, s. (2010). what-if simulation modeling in business intelligence. in business information systems: concepts, methodologies, tools and applications (pp. 2229-2247). igi global. [12] azadivar, f., & wang, j. (2000). facility layout optimization using simulation and genetic algorithms. international journal of production research, 38 (17), 4369-4383. [13] barnes, m. r. (1997, december). an introduction to quest. proceedings of the 29th conference on winter simulation (pp. 619-623). ieee computer society. [14] chan, f. t. s., ip, r. w. l., & lau, h. (2001). integration of expert system with analytic hierarchy process for the design of material handling equipment selection system. journal of materials processing technology, 116(2), 137-145. [15] gingu, e. l., & zapciu, m. (2014). improving layout and workload of manufacturing system using delmia quest simulation and inventory approach. international journal of innovative research in advanced engineering, 1, 52-61. [16] marcelo, m. t., avila, g.v., cruz, m.a., prado, b. m., navarro, m. m. (2016). process improvement and utilization of machines in the production area of a shoe manufacturing company ieee international conference on industrial engineering and engineering management, 2016-december, art. no. 7797966, 701-705 [17] mohd. salleh, n. a., kasolang, s., & jaffar, a. (2012). simulation of integrated total quality management (tqm) with lean manufacturing (lm) practices in forming process using delmia quest. paper presented at the procedia engineering, 41, 1702-1707. doi:10.1016/j.proeng.2012.07.371 international journal of engineering materials and manufacture (2020) 5(2) 40-49 https://doi.org/10.26776/ijemm.05.02.2020.02 abutu, j. 1 , lawal, s. a. 2 , ndaliman, m. b. 2 , lafia-araga, r. a. 3 , oluleye m.a. 4 1 department of mechanical engineering, taraba state university, jalingo, taraba state, nigeria 2 department of mechanical engineering, federal university of technology, minna, niger state, nigeria 3 department of chemistry, federal university of technology, minna, niger state, nigeria 4 department of mechanical engineering, ekiti state university, ado-ekiti, ekiti state, nigeria e-mail: mbndaliman@futminna.edu.ng reference: abutu, j., lawal, s. a. ndaliman, m. b., lafia-araga, r. a. and oluleye,m. a. tribological properties of friction materials developed from nonasbestos materials using response surface methodology. international journal of engineering materials and manufacture, 5(2), 40-49. tribological properties of friction materials developed from nonasbestos materials using response surface methodology abutu joseph, lawal sunday albert, ndaliman mohammed baba, lafia-araga ruth anayimi and oluleye atinuke modupe received: 22 april 2020 accepted: 09 may 2020 published: 30 june 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 abstract over many years, asbestos has been used as reinforcement material in the production of brake pads production but it has lost favour due to its carcinogenic nature, as a result, there is need to investigate other possible substitute which can offer similar tribological properties as the carcinogenic material (asbestos). several works has been carried out using different reinforcement material with the aim of finding a possible replacement for asbestos. in this work, rule of mixture (rom) was ustlised for sample formulation and the tribological properties of natural based material (coconut shell and seashell) were investigated using experimental design (response surface methodology) and multiresponse optimisation technique (grey relational analysis). the multi-response performance of the formulated brake pads samples was compared with a commercial brake pad sample. the research findings revealed that sample can be produced using 52% reinforcement, 35% binder, 8% abrasive and 5% friction modifier while the grey relational analysis (gra) showed that optimum multi-response performance of the developed coconut shell based sample can be achieved using mp, mt and ct and htt of 12mpa, 100 o c, 6mins and 2hrs respectively while that of the developed seashell based brake pad can be achieved using mp, mt and ct and htt of 10mpa, 160 o c, 12mins and 2hrs respectively. also, the analysis of variance (anova) results show a percentage error of less than 5% indicating minima noise effect. in addition, the optimized coconut shell-based brake pads falls within the category of class h (µ >0.55) type of brake pads while seashell based sample falls within the class g (µ: 0.45-0.55) type of brake pads. it therefore concluded that the use of coconut shell can serve as a better substitute for asbestos-based brake pads. keywords: brake pad, response surface methodology, tribological properties, grey relational analysis. 1 introduction friction materials are materials used for the development of automobile parts such as clutch and brake pads which are utilised in the transmission and braking of various machineries like cars, aircraft, motorcycles and other automobile systems. the constituents kept varying with the aim of meeting up with environmental technology and emerging. blau (2001) reported that friction materials can be classified as semi-metallic, organic and carbon-based, depending on the elemental composition. mechanics working on automobile are in most cases exposed to asbestos dust in several ways. this include, grinding of friction brake or clutch, repair work on brakes and clutch, where accumulated dusts are always wiped off before the old ones are replaced using brush (abutu et al., 2018). all these methods are capable of causing asbestos particles to become airborne which is very hazardous to the environment. dagwa and ibhadode (2008) reported that if old brake pads are still hard enough to be applied, automobile mechanics working on them often utilize a bench grinder to normalize the surface, or dissolve the dirts of the lining which often lead to the release of the particles of asbestos, thereby putting human at risk of contacting diseases such as pleural, peritoneal or pericardial mesothelioma, asbestos related cancer and asbestosis (norton, 2001). also, mutlu et al. (2009) reported that tribological properties are very important properties in the performance of brake pads and a relatively high friction coefficient in the range of 0.3-0.7 and lower wear rate is normally desirable when using brake lining materials. several works have been carried out with the aim of replacing asbestos as inclusion in brake pads production. tribological properties of friction materials developed from nonasbestos materials using response surface methodology 41 gabriel (2016) utilized periwinkle/palm shell as reinforcement material using taguchi experimental design and reported that optimal performance of the developed friction material can be obtained using moulding pressure (140 kpa), moulding temperature (150 ˚c) and curing time (10 minutes) as process parameter. also, abutu et al. (2018) with the aim of finding a substitute for asbestos developed a friction material using seashell as reinforcement material and utilizing response surface-central composite design (rsm-ccd) technique and grey relational analysis (gra). the authors reported that seashell can serve as good substitute for asbestos in friction material production and that multiresponse performance of the developed material can be obtained using 1 hour heat treatment time, 12 minutes curing time, 160 ºc moulding temperature and 14mpa moulding pressure. also ruzaidi et al. (2011) formulated a nonasbestos containing brake pad with varying composition of polychlorinated biphenyls (pcb) and palm ash waste along with thermoset resin as a binder and metal filler as abrasive. five samples were produced using moulding pressure, moulding temperature and curing time of 122 mpa, 150 ̊c and 5 minutes respectively and were tested to examine its compression strength, water absorption rate, wear rate, and morphological properties. experimental findings indicated that the optimum performance (mechanical and wear properties) of the brake pads was obtained using higher percentage of palm ash and also, wear properties of the developed brake pads compared satisfactorily with conventional brake pad. also, mutlu et al. (2009) with the aim of finding a possible replacement for asbestos whose dust is hazardous developed friction materials using rice husk dust (rhd) and rice straw dust (rsd) to study the tribological behaviour of brake pads. the materials in each brake pad were composed of rhd, rsd, copper particles, barite, brass, cashew, steel fibres, graphite and alumina. the newly formulated brake pads were tested in order to study their tribological performance and the results revealed a mean friction coefficient of 0.315 – 0.381 which is very low to be applied in heavy duty automobiles brake pads as specified in the work of dagwa and ibhadode (2008) while the wear rate varies from 0.000853 – 0.001041 g/mm 2 . in addition, fono–tamo and koya, (2011), also developed friction materials using palm kernel shell combined with other materials and observed that the optimal mechanical properties of the developed material showed a hardness of 32.34 and shear strength of 40.95 mpa while the optimum coefficient of friction of was found to be 0.43. also, ikpambese et al. (2014) developed an asbestos–free friction material using palm kernel fibres as reinforcement material and reported that sample with 10% palm kernel fiber, 6% al2o3, 40% epoxy–resin, 29% graphite gave and 15% calcium carbonate gave the optimum performance. similarly, bashar et al. (2012) utilized coconut shell powder as reinforcement material to develop friction material and found that high inclusion of coconut powder may results in brittleness of the composite and also samples with 60 % matrix and 10% reinforcement as well as 50% matrix and 10% reinforcement can be utilized in the production of friction materials. yawas et al. (2016) also developed an asbestos–free friction material using periwinkle shell as reinforcement material and revealed that optimal periwinkle shell reinforced sample produced using sieve size of125μm possessed specific gravity (1.01 g/cm3), coefficient of friction (0.41), hardness (116.7 hrb), compressive strength (147 n/mm2), and thickness swell in water (0.39 %) and thickness swell in sea oil (0.37 %). also, ibhadode and dagwa, (2008) used palm kernel shell (pks) as reinforcement material along with other constituents in the production of friction materials and found that optimal sample produced using 56% reinforcement, 24% binder, 14% abrasives and 6% friction modifier compared favourably with commercial samples as a result can served as replacement for asbestos in friction lining production. therefore, in this study, locally sourced coconut shell and seashell were separately used as reinforcement material along with other constituents to develop an environmentally friendly brake pad samples using central composite design (ccd)-response surface methodology (rsm) experimental design technique. the multi-response performance of the two brake pad samples was compared with commercially available brake pad by examining their tribological properties (wear rate and friction coefficient). 2. materials and methods 2.1 materials coconut shells (figure 1a) were sourced locally from a local coconut trader in sabon tasha market, kaduna – nigeria, seashells (figure 1b) were collected from a local seafood vendor in lagos bar beach, lagos-nigeria. also, alumina and commercial brake sample (figure 1c) designed for mazda 323 and produced by ibeto group of companies were sourced from a commercial shop situated in kaduna-nigeria while epoxy resin used together with hardener (sikadur 42t) were purchased from a chemical store located in onitsha-nigeria while graphite (figure 1d) sourced from dry cell batteries (1.5 volt, tiger). 2.2 method development of brake pads constitute the preparation of sourced materials, experimental design using minitab 17 software, compression moulding process, testing of developed samples and analysis of experimental results using signal to noise (s/n), analysis of variance (anova) and grey relational analysis (gra). 2.2.1 materials preparation materials preparation involved the preparation of the coconut shells, seashells and graphite powder. these involved washing, cleaning using tissue paper, drying under the sun for 24 hours followed by crushing with metallic mortar and pestle and thereafter, grinding using grinding machine situated at samaru, zaria and then sieving using a sieve size of 10µm. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0ahukewiaszpdx6dlahxcmw4khbnzat4qfggsmam&url=https%3a%2f%2fwww3.epa.gov%2fepawaste%2fhazard%2ftsd%2fpcbs%2f&usg=afqjcnfwsfeomor1b1tj2whbu3e8oof0ja abutu et al.: international journal of engineering materials and manufacture, 5(2), 40-49 42 2.2.2 design of experiment using rsm design technique in this study, ccd via rsm experimental design consisting of moulding pressure (mp), moulding temperature (mt), curing time (ct) and heat treatment (htt) was built in accordance to standard l27(2) 4 using minitab 17 statistical software. the factor levels of process parameters and experimental design matrix are shown in table 1 and 2 respectively. figure 1: reinforcement and friction modifier used (a) crushed coconut shells (b) seashells (c) commercial brake pad sample (d) extracted graphite rods table 1: factor level of process parameters factor mp (mpa) mt ( o c) ct (min) htt (hr) high 16 160 10 4 low 12 120 6 2 table 2: rsm-ccd experimental design matrix run mt ( o c) mp (mpa) ct (minute) htt (hour) 1 120 12 6 2 2 120 16 6 2 3 160 12 6 2 4 160 16 6 2 5 120 12 10 2 6 120 16 10 2 7 160 12 10 2 8 160 16 10 2 9 120 12 6 4 10 120 16 6 4 11 160 12 6 4 12 160 16 6 4 13 120 12 10 4 14 120 16 10 4 15 160 12 10 4 16 160 16 10 4 17 140 10 8 3 18 140 18 8 3 19 100 14 8 3 20 180 14 8 3 21 140 14 4 3 22 140 14 12 3 23 140 14 8 1 24 140 14 8 5 25 140 14 8 3 26 140 14 8 3 27 140 14 8 3 a c b d tribological properties of friction materials developed from nonasbestos materials using response surface methodology 43 2.2.3 samples formulation and production sample formulation was carried out using rule of mixture (rom) technique outlined in the work of askeland (1985) utilising density (𝜌) as a criteria while production was carried out on a compression moulding machine situated at federal college of chemical and leather technology (fcclt), samaru, zaria (polymer workshop) and was conducted using the procedure adopted by abutu et al. (2019) which involved utilising varying process parameters shown in table 2 with constant percentage composition as obtained from rom. this procedure further involved pouring and mixing epoxy resin and hardener (catalyst) in the ratio of 2:1 in a separate container, followed by filling of mould cavity with total mixture of mixed binder and filler materials, then, the withdrawal of cured samples from the moulding machine, cooling of samples and removal of the cooled samples from the mould. 2.2.4 sample characterization tribological properties (wear rate and friction coefficient) of the developed and commercial samples were evaluated using a tribometer (anton paar gmbh, csm instrument, strasse 20, 8054 graz-austria) and experiment was conducted in accordance with astm g99 testing procedure using the test conditions presented in table 3. 3. results and discussion 3.1 samples formulation and production the results of sample formulation indicate that samples should be produced using 52% reinforcement material (seashell or coconut shell), 35% binder (epoxy resin and hardener), 8% abrasive (alumina) and 5% friction modifier (graphite). 3.1 experimental results the average values of experimental result along with the individual signal-to noise (s/n) ratios for wear rate (wr) and friction coefficient (µ) of the developed brake pad samples are shown in table 4. s/n ratios of friction coefficient were calculated using larger-the better (eqn. 1) while that of wear rate was calculated using smaller-the better (eqn. 2).          n n rn ns 1 2 11 log10/ (1)    nn r n ns 1 21 log10/ (2) r = response value of given factor level combination, n = number of factor level combination from the experimental results presented in table 4, it can be observed that the values of the friction coefficient varied from 0.477 to 0.788 for coconut shell-based samples and 0.43 to 0.61 for seashell-based samples. these values falls within the class f (0.35 – 0.45), g (0.45 – 0.55) and h ( 0.55) type of brake pads recommended for use in automobile by society of automobile engineers (sae) and reported by blau (2001) as well as dagwa and ibhadode (2006).these results are in good agreement with the earlier work of roubicek et al. (2008) who reported that friction coefficient that falls within the range of 0.30–0.70 is desirable in brake pads. therefore, seashell and coconut shellbased brake pads are suitable for use in automobiles. 3.2 multi-response optimisation multi-response optimisation of experimental results was carried using grey relational analysis (gra) technique. this technique was adopted to investigate the optimal process parameters that will produce the multi-response performance of the coconut and seashell-based brake pads. the procedure for gra include using the values of s/n ratios shown in table 3 to calculate the grey relational grade (grg) for friction coefficient and wear rate using larger the better (eqn. 3) and smaller the better (eqn. 4) attribute respectively. this is followed by the calculation of grey relational coefficient (grc) using eqn. 5 and finally, the calculation using grey relational grade using eqn. 6. larger-the-better attributes (wij) = ji iij aa aa   (3) smaller-the-better attributes (wij) = jj ijij aa aa   (4) where, ai = the performance value of alternative i attribute j and ja = max{aij , i = 1, 2, . . . , x}.response and ja = min{lij , i = 1, 2, . . . , x}. grc, (x0j, xij) = max maxmin dd dd ij     (5) abutu et al.: international journal of engineering materials and manufacture, 5(2), 40-49 44 j = 1, 2, . . . , 27 and i = 1, 2, . . . , 27, d= x0j –xij, , = min (dij, i = 1, 2, . . . , x; j = 1, 2, . . . , y), naxd and mind = maximum and minimum grg value for response and  is the distinguishing coefficient,  ∈ (0, 1). the aim of distinguishing coefficient is to reduce or increase the range of the grey relational coefficient and 0.5 is the widely accepted value (chin, 2003). grade = responsesofno grc .  (6) the results of grg, grc and grades obtained from gra are presented in table 5 and the resulting factor effects of process parameters are shown in table 6 while the main effect plots for coconut shell and seashell based brake pads are shown in figure 2 and 3 respectively. table 3: test parameters/conditions for tribology test ball diameter 10 mm speed 10 cm/s load 7 n ball material stainless steel duration of test 223 seconds humidity of environment 55 % temperature of environment 25 °c table 4: experimental results and s/n ratios of developed samples run mp (mpa) mt ( o c) ct (min) ht t (hr) coconut shell based seashell based µ µ (db) wr (mg/m) wr (db) µ µ (db) wr (mg/m) wr (db) 1 12 120 6 2 0.788 -2.07 0.2620 11.64 0.492 -6.16 0.3340 9.525 2 16 120 6 2 0.652 -3.72 1.0936 -0.78 0.447 -6.99 0.2685 11.42 3 12 160 6 2 0.686 -3.27 0.1310 17.66 0.548 -5.22 0.2358 12.55 4 16 160 6 2 0.688 -3.25 0.1703 15.38 0.529 -5.53 0.1834 14.73 5 12 120 10 2 0.685 -3.29 0.2030 13.85 0.556 -5.10 0.3995 7.970 6 16 120 10 2 0.601 -4.42 0.1244 18.10 0.525 -5.60 0.3536 9.029 7 12 160 10 2 0.601 -4.42 0.3995 7.970 0.58 -4.73 2.6130 -8.34 8 16 160 10 2 0.651 -3.73 0.0393 28.11 0.593 -4.54 0.2881 10.81 9 12 120 6 4 0.566 -4.94 0.6614 3.590 0.565 -4.96 0.2358 12.55 10 16 120 6 4 0.533 -5.47 0.2161 13.31 0.572 -4.85 0.1637 15.72 11 12 160 6 4 0.688 -3.25 0.0720 22.85 0.573 -4.84 0.2554 11.86 12 16 160 6 4 0.496 -6.09 0.0655 23.68 0.568 -4.91 0.1113 19.07 13 12 120 10 4 0.558 -5.07 0.6549 3.677 0.430 -7.33 0.2096 13.57 14 16 120 10 4 0.649 -3.76 0.7138 2.928 0.610 -4.29 0.2816 11.01 15 12 160 10 4 0.568 -4.91 0.6680 3.505 0.534 -5.45 0.1899 14.43 16 16 160 10 4 0.477 -6.43 0.7204 2.849 0.496 -6.09 0.7924 2.021 17 10 140 8 3 0.668 -3.50 0.1441 16.83 0.567 -4.93 0.1834 14.73 18 18 140 8 3 0.571 -4.87 0.0720 22.85 0.546 -5.26 0.4977 6.061 19 14 100 8 3 0.617 -4.19 0.6483 3.764 0.521 -5.66 0.1244 18.10 20 14 180 8 3 0.648 -3.77 0.0589 24.59 0.491 -6.18 0.2816 11.01 21 14 140 4 3 0.650 -3.74 0.0197 34.13 0.571 -4.87 0.2161 13.31 22 14 140 12 3 0.550 -5.19 0.0786 22.09 0.544 -5.29 2.1545 -6.67 23 14 140 8 1 0.720 -2.85 0.0066 43.68 0.509 -5.87 0.1048 19.59 24 14 140 8 5 0.614 -4.24 0.0720 22.85 0.519 -5.70 0.6549 3.677 25 14 140 8 3 0.503 -5.97 0.7138 2.928 0.498 -6.06 0.2227 13.05 26 14 140 8 3 0.528 -5.55 0.8382 1.533 0.511 -5.83 0.2096 13.57 27 14 140 8 3 0.521 -5.66 0.7924 2.021 0.497 -6.07 0.2030 13.85 tribological properties of friction materials developed from nonasbestos materials using response surface methodology 45 table 5: results of grey relational analysis (gra) senario grg grc grade coconut shell based seashell based coconut shell based seashell based coconu t shell based seashell based µ wr µ wr µ wr µ wr xo 1.00 1.00 1.00 1.00 1 1.00 0.72 0.39 0.36 1.00 0.64 0.45 0.44 0.82 0.45 2 0.62 1.00 0.11 0.29 0.57 1.00 0.36 0.41 0.79 0.39 3 0.72 0.59 0.69 0.25 0.64 0.55 0.62 0.40 0.60 0.51 4 0.73 0.64 0.59 0.17 0.65 0.58 0.55 0.38 0.62 0.47 5 0.72 0.67 0.73 0.42 0.64 0.60 0.65 0.46 0.62 0.56 6 0.46 0.58 0.57 0.38 0.48 0.54 0.54 0.4\5 0.51 0.50 7 0.46 0.80 0.86 1.00 0.48 0.72 0.78 1.00 0.60 0.89 8 0.62 0.35 0.92 0.31 0.57 0.43 0.86 0.42 0.50 0.64 9 0.34 0.90 0.78 0.25 0.43 0.84 0.70 0.40 0.64 0.55 10 0.22 0.68 0.82 0.14 0.39 0.61 0.73 0.37 0.50 0.55 11 0.73 0.47 0.82 0.28 0.65 0.48 0.74 0.41 0.57 0.58 12 0.08 0.45 0.80 0.02 0.35 0.48 0.71 0.34 0.42 0.53 13 0.31 0.90 0.00 0.22 0.42 0.83 0.33 0.39 0.63 0.36 14 0.61 0.92 1.00 0.31 0.56 0.86 1.00 0.42 0.71 0.71 15 0.35 0.90 0.62 0.18 0.43 0.84 0.57 0.38 0.64 0.48 16 0.00 0.92 0.41 0.63 0.33 0.86 0.46 0.57 0.60 0.52 17 0.67 0.60 0.79 0.17 0.60 0.56 0.71 0.38 0.58 0.55 18 0.36 0.47 0.68 0.48 0.44 0.48 0.61 0.49 0.46 0.55 19 0.51 0.90 0.55 0.05 0.51 0.83 0.53 0.35 0.67 0.44 20 0.61 0.43 0.38 0.31 0.56 0.47 0.45 0.42 0.52 0.44 21 0.62 0.21 0.81 0.23 0.57 0.39 0.73 0.39 0.48 0.56 22 0.28 0.49 0.67 0.94 0.41 0.49 0.60 0.89 0.45 0.75 23 0.82 0.00 0.48 0.00 0.74 0.33 0.49 0.33 0.54 0.41 24 0.50 0.47 0.54 0.57 0.50 0.48 0.52 0.54 0.49 0.53 25 0.11 0.92 0.42 0.23 0.36 0.86 0.46 0.40 0.61 0.43 26 0.20 0.95 0.49 0.22 0.39 0.91 0.50 0.39 0.65 0.45 27 0.18 0.94 0.41 0.21 0.38 0.89 0.46 0.39 0.64 0.43 table 6: resulting factor effects of process parameters level coconut shell based seashell based mp (mpa) mt ( o c) ct (min) htt (hr) mp (mpa) mt ( o c) ct (min) htt (hr) 1 0.5800 0.6700 0.4800 0.5400 0.5500 0.4400 0.5600 0.4100 2 0.6400 0.6565 0.6200 0.6325 0.5475 0.5088 0.5038 0.5513 3 0.5405 0.5190 0.5562 0.5419 0.5095 0.5410 0.4795 0.5324 4 0.5812 0.5687 0.6012 0.5887 0.5388 0.5775 0.5825 0.5350 5 0.4600 0.5200 0.4500 0.4900 0.5500 0.4400 0.7500 0.5300 figure 2: main effect plots for coconut shell based sample abutu et al.: international journal of engineering materials and manufacture, 5(2), 40-49 46 figure 3: main effect plots for seashell based sample the main effect plots shown in figure 2 indicates that optimum multi-response performance of the developed coconut shell based brake pad samples can be achieved using mp, mt and ct and htt of 12mpa, 100 o c, 6mins and 2hrs respectively while figure 3 revealed that optimum multi-response performance of the developed seashell based brake pads can be achieved using mp, mt and ct and htt of 10mpa, 160 o c, 12mins and 2hrs respectively. any change in these optimal parameters may lead to poor bonding between the resin and its constituent fillers (abutu et al., 2018). 3.3 production of optimized samples the optimised brake pad samples were produced using standard compression moulding process described in the earlier section. production of the coconut shell-based sample was done using mp, mt and ct and htt of 12mpa, 100 o c, 6mins and 2hrs respectively while the seashell-based sample was produced using mp, mt, ct and htt of 10mpa, 160 o c, 12mins and 2hrs respectively as obtained from gra. the percentage composition of the brake pad samples remains constant throughout the moulding process. 3.4 characterisation of optimised and commercial samples in order to study and compare the tribological properties of the optimised and commercial (control) brake pads, samples were characterised using the testing methods discussed in the previous section. the results of experimental findings compared with the control are summarised in table 7. the results presented in table 7 revealed that friction coefficient and wear rate of the commercial brake pads are 0.634 and 0.04184 mg/m respectively while that of coconut shell and seashell reinforced samples are 0.614 and 0.03156 mg/m as well as 0.542 and 0.07252 mg/m respectively. these results indicate that the coconut shell-based brake pads possesses lower wear rate compared to commercial and seashell-based samples and also falls within the category of class h (µ >0.55) type of brake pads. thus, is recommended for use in heavy duty automobile by the society of automobile engineers (sae) as reported in the work of blau (2001) and dagwa and ibhadode (2006). also, the samples reinforced with seashell falls within the class g ( : 0.45–0.55) type of brake pads and thus suitable for use in light weight automobile. the morphology of the wear track section of the optimized and commercial sample is shown in figure 4(a-c). the part labeled ‘a’ represent the wear track section of the test specimen. as shown in figure 4a, it can be observed that the coconut shell-based sample has the least track section with an area of 154597.2 μm2. this is followed by commercial sample (figure 4b) with track sectional area of 204896.1 μm2 and finally the seashell-based sample (figure 4c) which showed the widest track section (355165.0 μm2). these differences in the wear track area may be attributed to the variation in the hardness and flexural strength of the samples. this is in agreement with the earlier work of zum-gahr (1987) who reported that wear rate of materials are strongly dependent on the size, hardness, shape and flexibility of the abrasive particles as a results harder materials tend to have lower wear track sectional area. tribological properties of friction materials developed from nonasbestos materials using response surface methodology 47 figure 4: morphology of wear track section on tribometer table 7: tribological properties of optimised and control sample s/n properties commercial product (x) coconut shell based (c) seashell based (s) 1. wear rate (mg/m) 0.04184 0.0315 0.0725 2. coefficient of friction 0.634 0.614 0.525 table 8: anova for friction coefficient factor coconut shell based seashell based dof ss ms f p (%) dof ss ms f p (%) mp (mpa) 4 0.0297 0.0074 9.715 19.388 4 0.0116 0.0029 16.422 24.440 mt (ºc) 4 0.0177 0.0044 5.787 11.549 4 0.0142 0.0035 20.037 29.819 ct (min) 4 0.0252 0.0063 8.249 16.464 4 0.0117 0.0029 16.586 24.684 htt (hr) 4 0.0729 0.0182 23.855 47.609 4 0.0082 0.0021 11.648 17.335 error 10 0.0076 0.0008 4.989 10 0.0018 0.0002 3.721 total 26 0.1532 0.0059 100.0 26 0.0476 0.0018 100.0 table 9: anova for wear rate factor coconut shell based seashell based dof ss ms f p (%) dof ss ms f p (%) mp (mpa) 4 0.492 0.123 12.365 17.65 4 1.332 0.333 15.608 14.93 mt (ºc) 4 0.916 0.229 23.046 32.9 4 1.518 0.38 17.788 17.01 ct (min) 4 0.603 0.151 15.169 21.65 4 4.93 1.233 57.755 55.23 htt (hr) 4 0.675 0.169 16.975 24.23 4 0.932 0.233 10.917 10.44 error 10 0.099 0.01 3.569 10 0.213 0.021 2.391 total 26 2.786 0.107 100 26 8.926 0.343 100 3.5 analysis of variance (anova) anova was conducted on the experimental responses in order to study the significant effects and percentage contribution of individual process parameters. this analysis was carried out using confidence level of 99 % and significance level of 1 %. anova table shown in table 8-9 consist of degree of freedom (dof), sum of square (ss), mean square (ms), f-value and percentage contribution (p). the anova for the coefficient of friction of coconut shell-based composite shown in table 9 indicates that htt with percentage contribution of 47.609% provides the greatest impact on the friction coefficient of the friction materials. this is followed by mp (19.388%) and ct (16.464%), finally, the least significance, mt with percentage contribution of 11.549%. also, the anova for the coefficient of friction of seashell-based composite shown in table 9 indicates that mt with percentage contribution of 29.819% provides the greatest influence on the friction coefficient of the friction materials, followed by ct (24.684%) and mp (24.440%) and htt (17.335%). in addition, the anova for wear rate of coconut shell-based composite shown in table 10 revealed that mt with percentage contribution of 32.896% provides the greatest impact on the wear rate of the friction materials, followed by htt (24.231%), ct (21.653%) and finally, mp (17.651%). also, the anova for the wear rate of seashell-based composite shown in table 10 showed that ct with percentage contribution of 55.232% provides the greatest impact on the wear rate of the friction materials. this is followed by mt (17.011%), mp (14.93%) and finally, mp (10.442%). also, the percentage error obtained for this analysis were less than 5% which indicate that the experimental processes were conducted with minimum influence of noise (lawal et al., 2016; zaharudin et al., 2011). (a) optimised coconut shell -based sample (b) optimised seashellbased sample (c) commercial sample .a .a .a abutu et al.: international journal of engineering materials and manufacture, 5(2), 40-49 48 3.2.4 empirical regression analysis empirical regression equation was obtained using the experimental data with the aim of predicting the value of the investigated responses. the regression equations along with correlation coefficients (rsq) for coconut shell and seashell based sample are shown in equ. 7-11. for coconut shell reinforced composite, µ = 1.128 0.01223 mp 0.000240 mt 0.01056 ct 0.0429 htt (7) r-sq = 85.52% and r-sq (adj) = 75.62%. wear rate = 0.40950.0011 mp 0.00592 mt + 0.0202 ct + 0.0607 htt (8) r-sq = 66.77% and r-sq (adj) = 51.63% for seashell reinforced composite, µ = 0.471 + 0.00042 mp + 0.000342 mt 0.00050 ct + 0.00408 htt (9) r-sq = 53.28% and r-sq (adj) = 50.11% wear rate = 0.65360.0292 mp+ 0.00570 mt + 0.0303 ct 0.082 htt (10) r-sq = 76.47% and r-sq (adj) = 63.10%. as shown in eqn. 7-10, it can be observed that the value of r-sqadj (correlation coefficient) falls below the recommended of 80 % as a result of noise which could occur from experimental uncertainty (asuero et al., 2006). 4. conclusions this study was carried out with the aim of investigating the tribological properties of natural based (coconut shell and seashell) friction materials as a substitute for asbestos in the production of brake pads using response surface methodology and multi-response optimisation technique (gra). from the results obtained, the following conclusion can be drawn; i. changes in experimental factors affects the tribological properties of the developed friction materials as all the samples produced with varying parameters gave different performance characteristics. ii. multi-response optimization results indicate that optimum multi-response performance of the developed coconut shell based brake pad can be achieved using mp, mt and ct and htt of 12mpa, 100 o c, 6mins and 2hrs respectively while optimum multi-response performance of the developed seashell based brake pad can be achieved using mp, mt and ct and htt of 10mpa, 160 o c, 12mins and 2hrs respectively, iii. the optimized coconut shell based brake pads falls within the category of class h (µ>0.55) type of brake pads while seashell based sample falls within the class g ( : 0.45–0.55) type of brake pads as a result can be recommended for use in heavy and light duty automobile as specified by the society of automobile engineers (sae) standards. iv. the wear on seashell based and commercial sample showed a wider track section compared with that coconut shell which has a lower wear track section indicating a better wear resistance and friction coefficient. v. finally, the percentage errors obtained for anova were less than 5% which indicate that the experimental processes were conducted with minimum influence of noise. references abutu j., lawal s.a., ndaliman m.b., lafia-araga r.a., adedipe o. and choudhury i. a. (2018). effects of process parameters on the properties of brake pad developed from seashell as reinforcement material using grey relational analysis, engineering science and technology, an international journal, 21, 787–797, available at https://doi.org/10.1016/j.jestch.2018.05.014. abutu j., lawal s.a., ndaliman m.b., lafia-araga r.a., adedipe o. and choudhury i. a. (2019). production and characterization of brake pad developed from coconut shell reinforcement material using central composite design. sn applied sciences. 1:18. available at https://link.springer.com/article/10.1007/s42452-018-0084-x. askeland, d.r. (1985). the science and engineering of materials. massachusetts, pws publishers: u.s.a. asuero, a.g., sayago, a and gonzalez, a.g. (2006). the correlation coefficient: an overview, critical reviews in analytical chemistry, 36, 41-59. bashar d., peter, b.m. and joseph, m. (2012). effect of material selection and production of a cold-worked composite brake pad, journal of engineering of pure and applied science, 2(3)48. blau, p.j. (2001). compositions, testing and functions of friction brake materials and their additives: a report by oak ridge national laboratory for u.s dept. of energy. retrieved from www.0rnl.gov/webworks/cppr/y2001/rpt /11 2956.pdf. chin, p.f. (2003). manufacturing process optimization for wear property of fiber-reinforced polybutylene terephthalate composites with grey relational analysis, wear, 254, 298–306. dagwa, i. m., and ibhadode, a. o. a. (2008). some mechanical and physical properties of asbestos–free experimental brake pad. journal of raw materials research, issue 2. retrieved from http://www.scielo.br/scielo. php? script=sci_arttextandpid=s167andlng=enandnrm=isoandtlng=en. https://doi.org/10.1016/j.jestch.2018.05.014 https://link.springer.com/article/10.1007/s42452-018-0084-x http://www.0rnl.gov/webworks/cppr/y2001/rpt%20/11%202956.pdf http://www.0rnl.gov/webworks/cppr/y2001/rpt%20/11%202956.pdf http://www.scielo.br/scielo tribological properties of friction materials developed from nonasbestos materials using response surface methodology 49 dagwa, i.m., and ibhadode, a.o. a. (2006). some mechanical and physical properties of asbestos–free experimental brake pad. journal of raw materials research, issue 2. retrieved from http://www.scielo.br /scielo.php?script =sci_arttextandpid=s167858782008000200010andlng=enandnrm=isoandtlng=en. fono, t.r., and koya, o.a. (2011). palm kernel shell in the manufacture of automotive brake pad. department of mechanical engineering, oau, ile-ife. nigeria. gabriel (2016). development of automobile disk brake pad using eco-friendly periwinkle shell and fan palm shell materials. phd thesis, ahmadu bello university, zaria-nigeria. ibhadode, a.o.a. and dagwa, i.m. (2008). development of asbestos-free friction pad material from palm kernel shell, journal of the brazilian society of mechanical sciences and engineering. 30(2), 166-173. ikpambese, k.k., gundu, d.t. and tuleu, l.t. (2014). evaluation of palm kernel fibers (pkfs) for production of asbestos-free automotive brake pads. journal of king saud university – engineering sciences, 28 (1), 110–118. lawal, s.a., ugwuoke, i.c., abutu, j., lafia-araga, r.a., dagwa, i.m. and kariim, i. (2016). rubber scrap as reinforced material in the production of environmentally friendly brake pad. reference module in materials science and materials engineering. oxford: elsevier; 1-10. mutlu, i., eidogan, o. and findik, f. (2009). production of ceramic additive automotive brake pad and investigation of its braking characteristics, international journal of tribology, 84-92. norton, r.l. (2001), machine design: an integrated approach, 2nd (ed) addison wesley longman, singapore. roubicek, v., raclavska, h., juchelkova, d. and filip, p. (2008). wear and environmental aspects of composite materials for automotive braking industry. wear, 265: 167-175. ruzaidi, c.m., mustafa, a. b., shamsul, j.b. and alida, a.,and kamarudin, h. (2011). morphology and wear properties of palm ash and pcb waste brake pad. international conference on asia agriculture and animal ipcbee vol.1, iacsit press, singapore. yawas, d.s., aku, s.y. and amaren, s.g. (2016). morphology and properties of periwinkle shell asbestos-free brake pad. journal of king saud universityengineering sciences, 28,103-109. zaharudin, a.m., berhan, m.n. and talib, r.j. (2011). the effect of phenolic resin, rubber, calcium carbonate and graphite on tribological characteristic of semi-metallic brake. aip conference proceedings, 1400, (1)274. zum-gahr, k.h. (1987), microstructure and wear of materials, tribology series 10, elsevier, amsterdam. list of abbreviations doe=design of experiment mp=moulding pressure mt=moulding temperature ct=curing time htt=heat treatment time µ=coefficient of friction wr=wear rate gra=grey relational analysis grg=grey relational generation grc=grey relational coefficient s/n=signal to-noise ratio dmax= maximum grg dmin=maximum grg  =distinguishing coefficient 𝜌=density rsq=correlation coefficient anova=analysis of variance rom=rule of mixture. http://www.scielo.br/scielo.php?script=sci_arttext&pid=s167 http://www.sciencedirect.com/science/journal/10183639/28/1 http://dx.doi.org/10.1016/j.jksues.2013.11.002 international journal of engineering materials and manufacture (2016) 1(1) 1-2 https://doi.org/10.26776/ijemm.01.01.2016.01 m. y. ali department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: mmyali@iium.edu.my reference: ali, m. y. (2016). editorial. international journal of engineering materials and manufacture, 1(1), 1-2. editorial received: 10 september 2016 accepted: 11 september 2016 published online: 11 september 2016 publisher: deer hill publications © 2016 the author(s) creative commons: cc by 4.0 the international journal of engineering materials and manufacture (ijemm) is celebrating its first year of online open access publication. on this occasion, i would like to congratulate editorial board, reviewers, authors, readers, and subscribers. ijemm will be published quarterly. in the first year 2016, we planned for one issues with 5 articles in addition to this editorial. the initiative of this journal was taken in the 2015 and then with several meetings and discussions, finally platform was formed in july 2016 to nurture continuously growing in interest in the area of materials and manufacturing engineering. it was felt that the increasing number of researchers and academicians in the materials and manufacturing engineering community needs a dedicated journal for the publication of their research outputs. we have formed a strong editorial board for timely publication with high quality consistent review and proofreading. the present editorial board is as follows. editor-in-chief: professor dr. mohammad yeakub ali, international islamic university malaysia section editors: professor dr. md. abdul maleque, international islamic university malaysia professor dr. erry y. t. adesta, international islamic university malaysia professor dr. safian sharif, universiti teknologi malaysia professor dr. md. mustafizur rahman, universiti malaysia pahang, malaysia professor dr. mohammed alauddin, dhaka university of engineering and technology, bangladesh professor dr. a. k. m. sadrul islam, islamic institute of technology, bangladesh professor dr. p. s. sreejith, cochin university of science & technology, india professor dr. b. gültekin çetiner, marmara university, turkey associate professor dr. mohamed rahman, international islamic university malaysia associate professor erik l. j. bohez, asian institute of technology, thailand associate professor dr. mohd amri lajis, universiti tun hussein onn malaysia associate professor dr. mohammed baba ndaliman, federal university of technology minna, nigeria dr. tan bo, ryerson university, canada dr. muataz hazza, international islamic university malaysia dr. md abdul mazid, macquarie university, australia layout editors: mr. adebisi adetayo abdulmumin, international islamic university malaysia ms. asfana banu, international islamic university malaysia editorial 2 as the journal aims for indexing in scopus, thomson reuters, and other indexing authorities, at first we must publish at least several issues with quality relevant articles. we expect passion from authors, readers for indexing with quality articles. i hope that you will join us as authors and reviewers as it is a highly focused journal in the field of materials and manufacturing. it includes material design, processing, characterisation, manufacturing design, development, machining, optimisation, industrial applications, and many other related topics. please enjoy the reading this journal from anywhere anytime as it is a free and an open access journal based on public knowledge project (pkp) concept. the journal will contain original research papers on the topics listed in focus and scope. submitted manuscripts are subject to initial appraisal by the editors. if the manuscript is found to be suitable, it will be sent to two experts for single blind peer review to maintain the quality. once the paper is accepted it will be published online immediately and later on it will be included in an issue and volume. however, individual items will be published as soon as they are ready, by adding them to the “current volume” for faster dissemination of the articles. later on, articles will be organized in four issues in a year (january, april, july, and october). under the umbrella of pkp, this journal utilizes the lockss system to create a distributed archiving system among participating libraries and permits those libraries to create permanent archives of the journal for preservation and restoration. copyright of articles that appear in international journal of engineering materials and manufacture (ijemm) are belonged to “the author(s)” under terms and conditions of creative commons attribution 4.0 international public license (cc by 4.0). https://creativecommons.org/licenses/by/4.0/legalcode. as the journal is open access and full copyright is given to the author(s), it provides immediate access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge. there is no subscription charges for this journal. the journal impose an article processing charge (apc). if the paper is accepted for publication, you will be asked to pay an apc. the apcs are to cover the editorial, review, publication, webhosting, database, preservation, and other cost. if you do not have funds to pay apc, you will have an opportunity to pay at a discounted rate or to waive fee. we do not want fees to prevent the publication of worthy work. we hope that the new international journal of engineering materials and manufacture will serve the community well and this journal will be one of the main vehicles of presenting idea and research work in the areas of materials and manufacturing engineering. any suggestion on how to improve our activity in order to deliver a better journal to the authors, readers and subscribers will be always very much appreciated. professor dr. mohammad yeakub ali mimeche ceng, mieaust cpeng, masme, meuspen, miem, fieb, fbsme phd. (ntu), meng (ait), bsc eng (buet) editor-in-chief international journal of engineering materials and manufacture head department of manufacturing and materials engineering faculty of engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: mmyali@iium.edu.my mmyali@deerhillpublishing.com 10 october 2016 https://creativecommons.org/licenses/by/4.0/legalcode international journal of engineering materials and manufacture (2016) 1(1) 16-20 https://doi.org/10.26776/ijemm.01.01.2016.014 h. anuar et al. department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: hazleen@iium.edu.my reference: hazleen et al. (2016). tensile properties of durian skin fibre reinforced plasticized polylactic acid biocomposites. international journal of engineering materials and manufacture, 1(1), 16-20. tensile properties of durian skin fibre reinforced plasticized polylactic acid biocomposites hazleen anuar, mohd syafiq razali, hafizul adzim saidin, ammelia fazlina badrul hisham, siti nur e’zzati mohd apandi, fathilah ali received: 09 september 2016 accepted: 26 september 2016 published: 28 september 2016 publisher: deer hill publications © 2016 the author(s) creative commons: cc by 4.0 abstract this research investigates the effects of plasticizer and durian skin fibre (dsf) loading on tensile and morphological properties of polylactic acid (pla) biocomposites. epoxidized palm oil (epo) was added as a plasticizer in this project. the effect of epo content 0–10 wt% was investigated over the tensile properties of pla. epo at 5 wt% was found to provide the highest tensile properties on pla biocomposite. the plasticized pla was then investigated for the effect of dsf content by varying the dsf at 1, 3 and 5 wt%. the tensile properties improved by about 7% with 3 wt% dsf. scanning electron micrograph revealed that a ductile failure was induced in pla composite with 5 wt% epo and 3 wt% dsf. keywords: durian skin fibre, epoxidised palm oil, polylactic acid, tensile properties, ductile failure 1 introduction to preserve planet for next generation, the use of natural fibre polymer composites is receiving great attention in food packaging industry. the synthetic polymer based materials lead to an excessive waste in landfill in long period to degrade and also risk the environment and raised the public concern [1]. in 2014, department of environment, malaysia reported that the highest percentage of waste (~ 56%) accumulated in malaysia is dominated by wastage dumped into landfills to decompose rather than through recycling or incineration. therefore, there is a need to reduce these plastic waste problems particularly in food packaging materials [2]. biodegradable natural fibre-polymer composite is an alternative for food packaging offering range of functional due to their excellent properties in biodegradability, biocompatibility and edible [3]. despite of the excessive wastage, the increased number of diseases owing to food-borne pathogenic microorganisms in recent years also shows their influence associated with the development in packaging technologies [4]. therefore, the design concept of active food packaging as the most promising technology systems should be possessing effective attributes towards the preservation quality of food and environment [5]. an active packaging is well defined to extend shelf-life of foods by inhibit microbial growth and maintain the quality of the product with fresh and safe [6]. plasticizers are important agent in the processing of pla composites. pla may improve the brittleness of pla via polymers chain flexibility and process ability by lowering the second order transition temperature, the glass transition temperature (tg). due to low molecular weight and non-volatile compounds in the plasticizers, other properties will be indirectly affected. this includes reduce the tension of deformation, viscosity, hardness and at the same time resistance to biological degradation. current trends nowadays are utilization of natural-based plasticizers from plants to meet product quality and specification requirements. palm oil for example is a favourable vegetable oil because it is cheap, low in toxicity and easily available as a sustainable agricultural resource. the effect of epoxidized palm oil (epo) on pla/pcl was studied by [7]. they reported that epo reduced the tensile strength and modulus of pla/pcl blend produced via solution casting. this paper investigates the effects of plasticizer and durian skin fibre content on the tensile properties of polylactic acid biocomposites. the scanning electron micrograph is also presented to support the arguments in tensile properties. tensile properties of durian skin fibre reinforced plasticized polylactic acid biocomposites 17 2 experimental method the specimens were prepared via solution casting. the pla blends were dried in an oven at temperature 80 o c for 24 h. biocomposite based on pla and durian skin fibre were weighed according to the percentage of composite from 1wt% of dsf content to 5 wt%. polylactic acid (pla) was added with chloroform to dilute the pla powder for solution casting process. the ratio of the chloroform and the pla was 5:1. the mixture was then stirred with strong agitation of magnetic stirrer until the accumulation of the compound disappeared. for the effect of plasticizer, epoxidized palm oil was added into pla biopolymer. the epo was added with amount of 5 wt% and 10 wt%. the solution is poured into a mold with flat surface of the bottom part. then, the solution was let for drying at room temperature for 24 h. in the case of the effect of dsf content, the dsf was varied from 0 wt% to 5 wt%. the dsf and pla powder were mixed and stirred with spatula to ensure there is not aggregates of the compounds. then, all the sample was then cut in specific size for tensile test according to astm d882. tensile test was carried out on shimadzu autograph ags-x series. the cross head speed was 20 mm/min and load applied was 5 kn. the targeted thickness of the specimen was 0.1 ± 0.05 mm. 3 effect of epo on tensile properties pla/dsf composite the effect of epoxidized palm oil (epo) on the tensile properties of pla from 0, 5 and 10 wt% is shown in fig. 1(a). it is clear from fig. 1 that the pla without any epo have the highest tensile strength with 26.0 mpa. pla with 10 wt% epo have the lowest tensile strength which is with 10.6 mpa while pla with 5 wt% epo showed intermediate tensile strength between 0 and 10 wt% epo, which is 15.6 mpa. tensile fracture specimen of plasticized pla at 5 wt% epo is shown in fig. 4(a). fig. 1 shows that adding more plasticizer (epo) proportionally decreased the tensile strength of pla. this finding can be explained by the theory of gelation where the presence of the plasticizer weakened the polymer structure thus improves the flexibility of the pla biopolymer [8]. the low weight of molecular plasticizer molecules reduced and disrupted the polymers interaction which makes the polymer chain hold together [9-10]. the tensile modulus of pla/dsf is shown in fig. 1(b). generally, the addition of epoxidized palm oil (epo) as plasticizer was done to improve the tensile properties of rigid pla. as seen in fig. 1(a), pla with 5 wt% epo possessed the highest tensile modulus which is 1127.1 mpa. pla with epo 0 and 10 wt% again resulted in low tensile modulus. thus, from fig. 1 (b), pla with 5 wt% epo will be used for further investigations in terms of reinforcement loading and anti-microbial properties of pla composites. the increase in tensile modulus is due to good interaction between reinforcement and matrix in increasing wettability property of fibres [11-12]. results demonstrate that modifying chemical structure of pla polymer and dsf enhances the compatibility of hydrophilic dsf reinforcement and hydrophilic pla material in this experiment. figure 1: effect of epo content of pla composites on (a) tensile strength and (b) tensile modulus (b) (a) anuar et al., (2016): international journal of engineering materials and manufacture, 1(1), 16-20 18 4 effect of dsf loading on pla composites the effect of durian skin fibre (dsf) loading on tensile strength of pla and plasticized pla is shown in fig. 2. from fig. 2, it can be seen that the presence of dsf from 1 wt%, 3 wt% and 5 wt% altered the tensile properties of pla. according fig. 2 (a), the highest tensile strength was shown by pla with 3 wt% dsf. this is due to the strong interaction of interfacial bonding between the pla matrix and dsf. beyond 3 wt%, the tensile strength significantly dropped by almost 12%. this is due to the poor interaction which is mainly because of the hydrophobicity of pla and hydrophilicity of dsf. pla has an even electrons distribution which makes it non-polar, thus it cannot attract water [12]. the reduction of the strain of the composites is also due to the poor interfacial adhesion between dsf and the pla matrix as shown in fig. 3. fig. 3 shown the stress-strain curve of pla and pla/dsf. fig. 4(a), 4(b) and 4(c) presented micrographs of pla composites. from fig. 4(a), the surface of pla seen more brittle than fig. 4(b) and 4(c). whereas, ductile failure of the matrix clearly demonstrated the effect of epo as shown in fig. 4(c). the tensile modulus in fig. 2(b) however shows increasing trend with dsf content. this is usually happened in composites that reinforced with hard filler. this shows that dsf has imparted its stiffness to the matrix [13]. since this composite loses it brittle and weaker in terms of tensile strength, it tends to be stiffer [14-15]. the addition of fibre increases the flexibility of pla/dsf biocomposites by improve the polymer chain between both phase. thus, it gained its mechanical property from dsf content. figure 2: effect of dsf content of pla composites on (a) tensile strength (b) tensile modulus figure 3: stress-strain curve of pla and pla/dsf composites. (b) (a) tensile properties of durian skin fibre reinforced plasticized polylactic acid biocomposites 19 figure 4: sem micrographs of tensile fracture specimens at 1000x magnification (a) pla, (b) pla/dsf and (c) pla/dsf/epo (a) (b) (c) anuar et al., (2016): international journal of engineering materials and manufacture, 1(1), 16-20 20 5 conclusions this research presents the effects of plasticizer and durian skin fibre (dsf) loading on tensile and morphological properties of polylactic acid (pla) biocomposites with epoxidized palm oil (epo) as a plasticizer. the prepared composite sample of specific size were tested for tensile test according to astm d882 using shimadzu autograph ags-x series (shimadzu, japan) with 20 mm/min cross head speed and 5 kn load. this experimental research showed the followings.  the optimum plasticizer needed to plasticize the pla is found to be 5 wt%.  the presence of dsf improved tensile properties of plasticized pla at 3 wt%.  the positive effects of epo and dsf produced ductile failure of pla composite. acknowledgement this work was financially supported by fundamental research grant scheme (frgs16-003-0502) from ministry of education malaysia. the authors would like to thank iium for research facilities in making this studies success. references 1. neelamana, i. k., thomas, s., & parameswaranpillai, j. (2013). characteristics of banana fibers and banana fiber reinforced phenol formaldehyde composites‐macroscale to nanoscale. journal of applied polymer science, 130(2), 1239-1246. 2. janjarasskul, t., & krochta, j. m. (2010). edible packaging materials. annual review of food science and technology, 1, 415-448. 3. salmieri, s., & lacroix, m. (2006). physicochemical properties of alginate/polycaprolactone-based films containing essential oils. journal of agricultural and food chemistry, 54(26), 10205-10214. 4. sung, s. y., sin, l. t., tee, t. t., bee, s. t., rahmat, a. r., rahman, w. a. w. a., & vikhraman, m. (2013). antimicrobial agents for food packaging applications. trends in food science & technology, 33(2), 110-123. 5. cagri, a., ustunol, z., & ryser, e. t. (2004). antimicrobial edible films and coatings. journal of food protection, 67(4), 833-848. 6. labuza, t. p., breene, w.m. (1989). application of active packaging for improvement of shelf-life and nutritional quality of fresh extended shelf-life foods. journal of food processing and preservation, 13(1), 1–69. 7. chieng, b. w., ibrahim, n. a., then, y. y., & loo, y. y. (2014). epoxidized vegetable oils plasticized poly (lactic acid) biocomposites: mechanical, thermal and morphology properties. molecules, 19(10), 16024-16038. 8. mekonnena, t., mussone, p., khalil, h., & bressler, d. (2013). progress in bio-based plastics and plasticizing modifications. journal of materials chemistry a, 1(43) 13379-13398. 9. xu, y. q., & qu, j. p. (2009). mechanical and rheological properties of epoxidized soybean oil plasticized poly (lactic acid). journal of applied polymer science, 112(6), 3185-3191. 10. smith, e. r., howlin, b. j., & hamerton, i. (2013). using poss reagents to reduce hydrophobic character in polypropylene nanocomposites. journal of materials chemistry a, 1(41), 12971-12980. 11. hargitai, h., rácz, i., & anandjiwala, r. d. (2008). development of hemp fiber reinforced polypropylene composites. journal of thermoplastic composite materials, 21(2), 165-174. 12. tee, y. b., talib, r. a., abdan, k., chin, n. l., basha, r. k., & yunos, k. f. m. (2015). comparative study of chemical, mechanical, thermal, and barrier properties of poly (lactic acid) plasticized with epoxidized soybean oil and epoxidized palm oil. bioresources, 11(1), 1518-1540. 13. nazri, w. b., ezdiani, z. n., romainor, m. m., erma, k. s., jurina, j., & fadzlina, n. (2014). effect of durian skin fibre loading on the mechanical properties. journal of tropical agriculture and food science, 42(2), 169. 14. faruk, o., bledzki, a. k., fink, h. p., & sain, m. (2012). biocomposites reinforced with natural fibers: 2000– 2010. progress in polymer science, 37(11), 1552-1596. 15. xiao, l., wang, b., yang, g., & gauthier, m. (2012). poly (lactic acid)-based biomaterials: synthesis, modification and applications (pp. 247-282). intech open access publisher. international journal of engineering materials and manufacture (2017) 2(1) 16-24 https://doi.org/10.26776/ijemm.02.01.2017.03 a. n. m. karim , h. m. e. kays , n. a. a. rosland and s. t. tuan department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: mustafizul@iium.edu.my reference: karim, a. n. m., kays, h. m. e., rosland, n. a. a. and s. t. tuan (2017). gate-to-gate life cycle assessment for determining carbon footprint of catalytic converter assembly process. international journal of engineering materials and manufacture, 2(1), 16-24. gate-to-gate life cycle assessment for determining carbon footprint of catalytic converter assembly process a. n. mustafizul karim, h. m. emrul kays, nur aisyah and saravanan tanjong tuan received: 10 march 2017 accepted: 27 march 2017 published: 31 march 2017 publisher: deer hill publications © 2017 the author(s) creative commons: cc by 4.0 abstract with the pursuit of embracing the circular economy, having upward trend in vehicle sales and environmental concern, sustainability has become an imperative part of the global automotive manufacturing strategies. one of the tactics to achieve this sustainable goal is to conserve and enhance the resource base by salvaging the embedded values from end-of-life product and for which, the remanufacturing can be considered as one of the most prominent epitome. even though many of the auto parts like engine, transmissions, starters, alternators and etc. have been assessed for remanufacturability since last few decades, being a major component of a car body the catalytic converter (cc) still remains unfocused in literature. however, to examine the remanufacturability of cc, a comprehensive study for assessing its economic, social, and environmental impact is inevitable. therefore, with an underlying aim of designing the remanufacturable cc, in this endeavour an attempt has been made to evaluate the environmental impact of its welding operations by means of energy consumption through gate-to-gate life cycle assessment. real life data are collected from a local malaysian cc manufacturer. the obtained results show that the welding section has a carbon footprint of 0.203 kgco2e/unit of cc with major emission coming from the plasma arc welding. in addition to that, it is also observed that the value of carbon footprint is not only sensitive to the emission factor and processing time, but also it is responsive to the nature of the processing operations. certainly, this observation is to motivate to change the product design from the prospect of remanufacturing. keywords: carbon footprint, life cycle assessment, exhaust system, catalytic converter 1. introduction the unprecedented and reckless usages of the environment by raw materials extractors, manufacturers and consumers, by considering the environment as a source of unlimited resources as well as sink for the discarded endof-life products, have endangered our natural systems by landfilling, air and water contamination as well as industrial mishaps [1,2] . even nowadays, these problems with landfill have become graver due to the increasing demand of land for habitation along with the waste disposal and generation of methane gas directly from landfills. for instance, in 1996 the environment protection agency (epa) reported that within less than a decade 17 states of us would reach to their landfill capacity while new york and massachusetts even need less than 5 years as 80% of america’s wastes usually go to landfills [3]. whereas, discharge of greenhouse gases such as carbon dioxide (co2), methane and cfcs into air directly by manufacturing and other human activities is rising in an exponential rate [4]. meanwhile, the mishaps as reported in union carbide in india and chernobyl in the former u.s.s.r. resulted in casualties and grave environmental impact. as a consequence, the global warming, as evident in the increases in average air and ocean temperatures, widespread melting of ice, and rising global average sea level, has become unequivocal and remains no more as a hypothetical phenomenon. owing to this graver catastrophe, for satisfying the needs of mankind and protect our environment, the sustainable development has become an imperative act in the manufacturing sectors [5]. one of the tactics of acquiring this goal of sustainable development is the end of life (eol) product recovery and for which, nowadays karim, et al. (2017). international journal of engineering materials and manufacture, 2(1), 16-24. 17 several options like reuse, recycle and remanufacture are widely adopted [6]. however, among these three strategies, the recycling process involves huge amount of energy consumption while it converts the recyclables into the raw materials. moreover, the products manufactured through recycling process also lose some of its early added values. even though, these kinds of deficiencies of recycling processes can possibly be minimized by adopting any of the reusing and remanufacturing processes [7]. but, reusing process does not retain the product features as like new ones, while the remanufacturing processes are envisaged to do so. as a consequence, by featuring the positive attributes, nowadays a numbers of industries have embraced the remanufacturing epitomes within the manufacturing facilities e.g. automotive, machinery, computers, toner, cartridges, medical industry, wood industry and office furniture etc. [8, 9]. unfortunately, a large portion of the available products manufactured from these sectors are difficult to remanufacture as most of their designs are focussed on functionality and cost irrespective to the environmental concern [10]. thereby, many of the researchers believe that the success of this widely adopted remanufacturing practice is largely dependent on the factors like product design, efficient remanufacturing process, demand and condition of returned products [11, 12]. nevertheless, among all the manufacturing sectors, the researchers have identified that the automotive sector alone can secure a share of two-thirds of remanufacturing business [13, 14]. which is also evident in the remanufactured auto parts like engine, transmission, steering gear, starter, generator, turbo charger, alternator, compressor, steering unit and automobile door etc. [15-20]. regrettably, the cc having the potential scope of remanufacturing, is still remaining unfocused. however, to examine the remanufacturability of cc and fill this research gap, a comprehensive study for assessing its environmental impact is inevitable. and for which, the lca process could be one of the best possible approaches. in literature, according to the society of environmental toxicology and chemistry (setac), the “life-cycle assessment is a process to evaluate the environmental burdens associated with a product, process or activity by identifying and quantifying energy and materials used and wastes released into the environment; to assess the impact of those energy and material uses and releases to the environment; and to identify and evaluate opportunities to affect environmental improvements. the assessment includes the entire life-cycle of the product, process or activity, encompassing extracting and processing raw materials; manufacturing; transportation and distribution; use; re-use; maintenance; recycling, and final disposal” [21]. even though it is generically believed that lca should focus on the entire life cycle of a product or process, by featuring the modelling complexities and the scope of studies, the researchers have classified it as cradle-to-grave, cradle-to-gate, cradle-to-cradle, gate-to-gate and well-to-wheel etc. meanwhile, for any of these classes, the iso 14040:2006, 14044:2006 and pas 2050 are generally adopted for accounting and reporting standard of lca. interestingly, with an underlying aim of assessing the environmental burden and improvements, the lca process is widely adopted in various field of applied engineering. for instance, smith, v. m., & keoleian, g. a. (2004) have applied the lca approach for assessing the value of remanufactured engines [22]. yang, m., & chen, m. (2005) quantified the environmental impact of remanufactured engine through lca approach [23]. warsen, j., laumer, m., & momberg, w. (2011) adopted lca approach for comparing the environmental impact of newly manufactured and remanufactured manual transmission system [24]. nevertheless, as best of our knowledge now none of the researchers has attempted to quantify the environmental impact and/or carbon footprint of the catalytic converter. hence in this endeavour an attempt has been made to evaluate the environmental impact by means of energy consumption through gate-to-gate life cycles assessment guideline of iso 14040:2006 and iso 14044:2006. however, within the scope of this gate-to-gate lca search, a wide range of transformation and assembly operations are involved in the catalytic converter manufacturing process, the welding section is explicitly considered in this research for quantifying its environmental impact and/or carbon footprint. subsequent sections of this paper are arranged as follows: section 2 presents a literature review on automotive industries in malaysia, practice of remanufacturing epitome, application of lca in automotive sector. section 3 highlights the research method and collected data. the corresponding results and discussions are provided in section 5. finally, in section 6, the relevant concluding remarks are made. 2. literature review nowadays, within most of the industrialized countries, due to the depleted natural resources, diminished landfill and incineration capacities as well as the increased level of ecological pollution, the sustainable development has become an undeniable act. as a consequence, the governments and environmental protection agencies have come up with several stricter environmental legislations and strategies to limit the industrial wastes by imposing the responsibility of waste disposal on the manufacturers. remanufacturing, being an economical and environmental friendly business paradigm, is deemed to be helpful for the manufacturer in this regard. however, the success of this business epitome is largely dependent on the design of the product and process, and for which the quantification of carbon foot print is very much inevitable. hence, in line with achieving this research goal, in the following subsection a brief literature review on the automotive sectors and lca process is summarized. 2.1 automotive industry in malaysia the automotive sector has drawn the significant attention in manufacturing sector of malaysia since the establishment of its two national car manufacturer named as perusahaan otomobil nasional berhad (also known as proton) on gate-to-gate life cycle assessment for determining carbon footprint of catalytic converter assembly process 18 may 07, 1983 and perusahaan otomobil kedua sdn. bhd. (also known as perodua) on august 01, 1994. even though, at the initial stage the market share was only about 50,000 units per year, interestingly in 2013 it was reported that the perodua and proton had already shared 51.1% of the total industry volume (tiv) [25] amounting to 655,793 units per year. this development and progression of malaysia’s automotive industry has also made the country a production centre for major automotive component manufacturers. as a consequence, today more than 690 automotive component manufacturers are reported in malaysia producing different auto parts like body panels, brake parts, engine parts, transmission and steering parts, rubber parts and electrical and electronic parts. with this increase of share in business market, malaysia’s automotive industries have also drawn significant attention of the researchers and policy makers from the prospect of sustainability. for instance, the government of malaysia, in national automotive policy 2014 (nap 2014) have expressed their interest and set their goal of making the automotive sector more competitive in comparison to other developed countries from the prospect of ‘green’. interestingly, the remanufacturing sector is also getting priority in malaysia as the malaysia automotive remanufacturing roadmaps (marr) have aimed to transform their used parts industries into the remanufacturing one. 2.2 remanufacturing in automotive industry in the period of 1960 to 2002, the global vehicle ownership has increased to about 573 million from 47.6 million [26]. consequently, the transportation system is accounted for approximately 40% of the world’s total oil consumption and thereby identified as one of the major sources of ghgs emission [27]. this fact makes the sustainable development crucial for the automotive manufacturers. by featuring this rising need, the governments and environmental legislation authorities not only pushed the manufacturers to follow the green manufacturing practices but also to take back the eol products. in this regard, remanufacturing, being an environmentally friendly and economically sound approach, is widely adopted in the global automotive sector. for instance, nowadays in europe many of the automotive manufacturers like volkswagen, audi, bentley, bugatti, lamborghini, seat and skoda have involved themselves in remanufacturing [28]. in china, since 2008, 14 different auto part manufacturers get involved in remanufacturing business [18]. nevertheless, even though the remanufacturing business gets wider acceptance in the automotive sectors since last century, only a very few types of auto parts e.g. engine, transmission, gear box, alternator, steering gear, starter, generator, front/rear axles, vehicle frame, turbo chargers, compressors, water pumps, fuel delivery and brake systems are remanufactured in contemporary markets. surprisingly, as best of our knowledge, being a major component of exhaust system, the catalytic converter has not been studied explicitly from this respect. 2.3 application of lca in automotive sector the life cycle assessment or analysis (lca) is generically defined as a method of investigation and valuation of environmental impact due to the existence of any typical product or service. in literature, two different standards, proposed by iso under the title of iso 14040:2006 and iso 14044:2006, are usually adopted as guidelines of lca. whereas the iso/tr 14047:2003 and iso/tr 14047:2002 are used for the life cycle impact assessment and data documentation. besides, nowadays the researchers have also widely adopted the pas 2050 (publicly available specifications), which is proposed by british standards institution (bsi) and prepared by following the guidelines of iso14040 and iso14044, for evaluating the product or process carbon foot print [29]. in recent times, lca process is widely adopted for quantifying the economic, environmental and social impact of the products and processes. for instance, smith, v. m., & keoleian, g. a. (2004) apply the lca approach for assessing the value of remanufactured engines [22]. yang, m., & chen, m. (2005) quantify the environmental impact of remanufactured engine through lca approach [23]. warsen, j., laumer, m., & momberg, w. (2011) adopted lca approach for comparing the environmental impact of newly manufactured and remanufactured manual transmission system [24]. nevertheless, as best of our knowledge till now the environmental impact of catalytic converter has not explicitly studied by means of lca approach. 3. methodology and data collection in this research the iso 14040 and iso 14044 are considered as the guidelines for conducting the gate-to-gate lca of the welding operations involved in the formation process of catalytic converter. in presence of various welding processes, the carbon footprint is computed by using the following eq. (1)-(2).   tpe (1) efecfp  (2) where: p=power rating of welding operation (kw) t=processing time (hour) e=energy consumption of welding operation (kwh) ef= emission factors for electricity (kg co₂e/kwh) karim, et al. (2017). international journal of engineering materials and manufacture, 2(1), 16-24. 19 3.1 data collection in this research, the welding operations involved in the formation process of catalytic converter are considered as the functional units. to collect the relevant data, a detailed time study is conducted in the shop floor of a local catalytic converter manufacturer. whereas, the standard welding parameters are gathered from the shop floor and verified by comparing with the standard parameter settings of welding operations as presented in the metals handbook [30]. on the basis of the collected data, a process map of the welding operations is presented in the fig.1. since the company classified the entire operations involved in the catalytic converter manufacturing process under four titles i.e. main body assembly, inlet assembly, outlet assembly and final assembly, the welding operations in fig.1 are also arranged accordingly. as no welding operation is involved in the main body assembly section, the section is excluded intentionally from our process map. however, the details of each individual process and relevant processing times are presented in table 1. in addition to that, for quantifying the carbon footprint, the electricity emission factor for malaysia is considered in this research as 0.65592 kg co₂e/kwh [31, 32]. meanwhile, the standard operating conditions for each of the welding operations are collected, verified and presented in table 2. figure 1: process map of welding operations involved in catalytic converter manufacturing process. table 1: description of welding operations and associated processing times section process description types of welding processing time, t (sec) i n l e t a s s e m b l y p1 assembly of outer cones mig 41 p2 manual tig welding on the outer cones tig 32 p3 assembly of branches plasma 89 p4 assembly of inlet flange and boss sensor mig 27 p5 assembly brackets mig 53 o u t l e t a s s e m b l y p6 assembly of outlet cone mig 39 p7 assembly of outlet flange tig 25 f i n a l a s s e m b l y p8 assembly of outlet cone mig 34 p9 assembly of inlet branch mig 52 p10 assembly of heat cover brackets mig 34 p11 assembly of heat cover branches, heat cover converters and case converter mig 83 gate-to-gate life cycle assessment for determining carbon footprint of catalytic converter assembly process 20 table 2: standard operating conditions of the welding operations. section process types of welding voltage (v) current (a) i n l e t a s s e m b l y p1 mig 22 85 p2 tig 10 100 p3 plasma arc 30 115 p4 mig 22 85 p5 mig 22 85 o u t l e t a s s e m b l y p6 mig 22 90 p7 tig 22 300 f i n a l a s s e m b l y p8 mig 22 90 p9 mig 22 90 p10 mig 22 90 p11 mig 10 85 4. results and discussions for the considered real life case study of catalytic converter, the carbon footprint is computed trough the incorporation of the data presented in table 1-2 and by using eq. (1)-(2). the obtained results are summarized in the table 3. it can easily be realized that the total energy consumption and carbon footprint of the considered welding processes are 0.30991 kwh which is equivalent to 0.20327 kgco2e respectively. 4.1 carbon hotspot based on the obtained outputs as presented in fig. 2, it is evident that a maximum amount of 0.05594 kgco2e of carbon footprint is traced by process 3 while the process 2 stands for a minimum value of 0.00583 kgco2e. this finding is further supported by a statistical test result, as shown in fig. 3, with 27% of the total emission. thus the process of assembling the inlet branches emits the maximum ghgs, and it can be termed as carbon hotspot. this high emission of the process might be attributable to the specific design requirements and joining methods, power rating as well as the longest processing times. subsequently the whole design process can be revisited for lowering the cfp impact. 4.2 sensitivity analysis since it is realized that the inclusion or exclusion of certain variables may have a significant impact on the entire carbon footprint value, in this subsection an endeavour has been made to analyse the sensitivity from the perspective of emission factor and processing time. 4.2.1 sensitivity analysis from the perspective of emission factor in this sensitivity analysis an attempt has made to realize the impact of changing the emission factor on the entire carbon footprint value. in this context, the electricity emission factor is changed by ±10% with an increment of ±5% from the original value. for these set of revised emission factors the final carbon footprint values are computed and presented in table 4. from table 4 it can be seen that the cfp is responsive to the emission factor. this finding also reviled the concern of energy generation mix in product manufacturing. in other words it may be possible to reduce the manufacturing carbon footprints by selecting the optimal energy generation mix. 4.2.2 sensitivity analysis from the perspective of processing time to comprehend the impact of variable processing time on the entire carbon footprint value, in this section a sensitivity analysis has been conducted from the perspective of processing times. to do so, the processing time is varied by ±10% with an increment of ±5% from the original value. for these set of revised processing times the final carbon footprint values are computed and presented in table 5. the responsiveness of the cfp values to the processing time can easily be comprehended from table 5. this responsiveness of the cfp values to the processing time also reviles the necessity of practicing the production planning tools and techniques (i.e. forecasting, work measurement techniques, lot sizing, balancing and scheduling etc.) for embracing the sustainable development in manufacturing shop floors. however, for better realization we extend our sensitivity analysis for two particular welding operations (i.e. p3 and p7) having maximum processing time. the output of this analysis is tabulated in table 6.the output illustrated in table 6, led us to a very interesting observation that impact of processing time on the cfp values depends also on the nature of operations. to clarify this observation karim, et al. (2017). international journal of engineering materials and manufacture, 2(1), 16-24. 21 the fig. 4 is plotted. it is seen that the cfp values have not exhibited any consistent pattern while we compare it with the changes in processing time. therefore, it can be concluded that the cfp values not only depend on the processing time but also on the process itself. and for which the change in product design to ease the remanufacturing is very much inevitable in reducing the cfp. figure 2: breakdown of carbon footprint of welding processes. figure 3: breakdown of carbon footprint of welding processes according to the percentage. table 3: computed carbon footprints of the welding operations. section process consumed energy (kwh) carbon footprint (kgco2e) i n l e t a s s e m b l y p1 0.02129 0.01396 p2 0.00888 0.00583 p3 0.08529 0.05594 p4 0.01402 0.00919 p5 0.02753 0.01805 o u t l e t a s s e m b l y p6 0.02145 0.01406 p7 0.04583 0.03006 f i n a l a s s e m b l y p8 0.01870 0.01226 p9 0.02860 0.01875 p10 0.01870 0.01226 p11 0.01959 0.01285 table 4: computed values for sensitivity analysis from the prospect of emission factor. changes in ef (%) current cfp (kgco2e) revised cfp (kgco2e) changes in cfp (%) +10 0.20328 0.22360 +10 -10 0.20328 0.18294 -10 +5 0.20328 0.21344 +5 -5 0.20328 0.19311 -5 gate-to-gate life cycle assessment for determining carbon footprint of catalytic converter assembly process 22 table 5: computed values for sensitivity analysis from the prospect of processing time. changes in processing time current cfp (kgco2e) revised cfp (kgco2e) changes in cfp +10% 0.20328 0.22361 +10% -10% 0.20328 0.18295 -10.00% +5% 0.20328 0.21344 +5% -5% 0.20328 0.21344 -5.00% table 6: computed values for sensitivity analysis. process changes in processing time current cfp (kgco2e) revised cfp (kgco2e) changes in cfp p3 +10% 0.20328 0.20887 +2.75 p3 -10% 0.20328 0.19768 -2.75 p3 +5% 0.20328 0.20607 +1.38 p3 -5% 0.20328 0.20048 -1.38 p7 +10% 0.20328 0.20478 +1.48 p7 -10% 0.20328 0.20027 -1.48 p7 +5% 0.20328 0.20478 +0.74 p7 -5% 0.20328 0.20177 -0.74 figure 4: changes in cfp values with respect to processing time. 5. conclusions today, the call of millions of people as reiterated for a climate agreement is to enshrine this generation’s rightful claim for a safe, sustainable, climate-resilient, green and low-carbon future. the call for climate action is not to end in paris or in kyoto but it should echo all the way in the whole world. as to ensure the paris agreement comes into fruition, participating in efforts by conducting a research in line with this global issue would be a notable contribution. with this view in consideration, this paper carries out the gate-to-gate life cycle assessment (lca) of the welding operations of catalytic converter assembly. the computed results show that all the welding operations have a carbon footprint of 0.203 kgco2e for a unit of catalytic converter. process 3 that assembles the inlet branches by using the plasma arc welding contributes about 27.00% of the total emission and is responsible for the majority of the emission. karim, et al. (2017). international journal of engineering materials and manufacture, 2(1), 16-24. 23 this high emission of the process might be attributable to the specific design requirements and joining methods, power rating as well as the processing times. so the whole design as well as the manufacturing process of catalytic converter can be reviewed and assessed with a goal of lowering the cfp impact. besides, in sensitivity analysis, it is also observed that the emission factor has a direct influence over the cfp and thereby, the usage of optimal energy generation mix may help the authorities in reducing the carbon footprint by incorporating some form of renewable energy sources. moreover, as cfp has shown responsiveness to the processing time, the production planning tools and techniques are also deemed to be helpful in optimizing the overall process cfp. it is also observed that the nature of operations has a direct influence over the cfp values. so a change in product and process design is expected to enable the organization to reduce their carbon footprint. this study is expected to be conducive to extend the analysis on the carbon footprint of entire catalytic converter by encompassing a comprehensive sensitivity analysis. acknowledgment this study was conducted under the frgs project (frgs14-102-0343) funded by ministry of higher education (mohe), malaysia. the authors are grateful to mohe and research management centre, international islamic university malaysia for their support. references 1. abdulrahman, m. d. a., subramanian, n., liu, c., & shu, c. (2015). viability of remanufacturing practice: a strategic decision making framework for chinese auto-parts companies. journal of cleaner production, 105, 311323. 2. dzioubinski, o. & chipman, r. (1999). trends in consumption and production: selected minerals (no. 5). retrieved 16th january 2017 from https://sustainabledevelopment.un.org/content/documents/347 esa 99 dp3 .pdf 3. dixit, s. b. (2006). product design: a conceptual development of product remanufacturing index. retrieved 16th december 2017 from http://scholarcommons.usf.edu/etd/2504/ 4. behera, s. r., & dash, d. p. (2017). the effect of urbanization, energy consumption, and foreign direct investment on the carbon dioxide emission in the ssea (south and southeast asian) region. renewable and sustainable energy reviews, 70, 96-106. 5. wu, h., lv, k., liang, l., & hu, h. (2017). measuring performance of sustainable manufacturing with recyclable wastes: a case from china’s iron and steel industry. omega, 66, 38-47. 6. king, a. m., burgess, s. c., ijomah, w., & mcmahon, c. a. (2006). reducing waste: repair, recondition, remanufacture or recycle?. sustainable development, 14(4), 257-267. 7. thierry, m., salomon, m., van nunen, j., & van wassenhove, l. (1995). strategie issues in product recovery management. california management review, 37(2), 114-135. 8. peter lundmark, p., sundin, e., & björkman, m. (2009). industrial challenges within the remanufacturing system. 3rd swedish production symposium göteborg, 2009. 132-138. 9. chapman, a., bartlett, c., mcgill, i., parker, d., & walsh, b. (2009). remanufacturing in the uk. a snapshot of the remanufacturing industry in the uk in 2009. centre for remanufacturing and reuse, uk. http://www.remanufacturing.org.uk/pdf/story/1p342.pdf 10. ferrer, g., (2001).theory and methodology on the widget remanufacturing operation. european journal of operational research, 135(2), 373–393. 11. paul goodall, p., rosamond, e., & harding, j. (2014). a review of the state of the art in tools and techniques used to evaluate remanufacturing feasibility. journal of cleaner production, 81, 1-15. 12. matsumoto, m., & umeda, y. (2011). an analysis of remanufacturing practices in japan. journal of remanufacturing, 1(1), doi:10.1186/2210-4690-1-2. 13. steinhilper, r. (2001). recent trends and benefits of remanufacturing: from closed loop businesses to synergetic networks. proceedings ecodesign 2001: second international symposium on environmentally conscious design and inverse manufacturing, 481-488. 14. yusop, n. m., wahab, d. a., & saibani, n. (2016). realising the automotive remanufacturing roadmap in malaysia: challenges and the way forward. journal of cleaner production, 112, 1910-1919. 15. zwolinski, p., & brissaud, d. (2008). remanufacturing strategies to support product design and redesign. journal of engineering design, 19(4), 321-335. 16. zhang, t., wang, x., chu, j., & cui, p. (2010). remanufacturing mode and its reliability for the design of automotive products. 5th international conference on responsive manufacturing green manufacturing (icrm 2010), 25-31. 17. jody, b. j., & daniels, e. j. (1991). automobile shredder residue: treatment options. hazardous waste and hazardous materials, 8(3), 219-230. 18. zhang, t., chu, j., wang, x., liu, x., & cui, p. (2011). development pattern and enhancing system of automotive components remanufacturing industry in china. resources, conservation and recycling, 55(6), 613-622. gate-to-gate life cycle assessment for determining carbon footprint of catalytic converter assembly process 24 19. jun, h. b., lee, d. h., kim, j. g., & kiritsis, d. (2012). heuristic algorithms for minimising total recovery cost of end-of-life products under quality constraints. international journal of production research, 50(19), 5330-5347. 20. hammond, r., amezquita, t., & bras, b. (1998). issues in the automotive parts remanufacturing industry: a discussion of results from surveys performed among remanufacturers. retrieved 16th january 2017 from https://pdfs.semanticscholar.org/eb84/8085b4858051 e8ff60b37e2c343aeb7419b0.pdf 21. consoli, f., allen, d., boustead, i., fava, j. franklin, w., jensen, a.a., de oude, et al., (eds). (1993). guidelines for life-cycle assessment: a “code of practice”, setac workshop held at sesimbra, portugal 31 march – 3 april. society for environmental toxicology and chemistry (setac). 22. smith, v. m., & keoleian, g. a. (2004). the value of remanufactured engines: life‐cycle environmental and economic perspectives. journal of industrial ecology, 8(1‐2), 193-221. 23. yang, m., & chen, m. (2005). life cycle of remanufactured engines. journal of central south university of technology, 12(2), 81-85. 24. warsen, j., laumer, m., & momberg, w. (2011). comparative life cycle assessment of remanufacturing and new manufacturing of a manual transmission. in: hesselbach j., herrmann c. (eds) glocalized solutions for sustainability in manufacturing. springer, berlin, heidelberg, 67-72. 25. malaysian automotive association (maa), (2013). market review 2013. retrieved 25th january 2017 from http://www.maa.org.my/pdf/market_review_2013.pdf. 26. dargay, j., gately, d., & sommer, m. (2007). vehicle ownership and income growth, worldwide: 1960-2030. the energy journal, 28 (4), 143-170. 27. mcauley, j. w. (2003). global sustainability and key needs in future automotive design. environmental science & technology, 37(23), 5414-5416. 28. gerrard, j., & kandlikar, m. (2007). is european end-of-life vehicle legislation living up to expectations? assessing the impact of the elv directive on ‘green’innovation and vehicle recovery. journal of cleaner production, 15(1), 17-27. 29. franchetti, m. j., & apul, d. (2012). carbon footprint analysis: concepts, methods, implementation, and case studies. crc press. 30. metals handbook (1971). american society for metals, 6. 31. brander. m, sood. a, wylie. c, haughton. a, and lovell. j (2011). ecometrica: electricity-specific emission factors for grid electricity. retrieved 30th january, 2017 from https://ecometrica. com / assets/electricity-specificemission-factors-for-grid-electricity.pdf 32. yazdani. z., talkhestan. g. a., kamsah. m. z. (2013).assessment of carbon footprint at university technology malaysia (utm), applied mechanics and materials, 295-298,872-875. international journal of engineering materials and manufacture (2018) 3(4) 171-181 https://doi.org/10.26776/ijemm.03.04.2018.01 p. manda, a. s. rao, s. singh and a. k. singh defence metallurgical research laboratory kanchanbagh, hyderabad, 500058, india e-mail: singh_ashok3@rediffmail.com reference: manda, p., rao, a. s., singh, s. and sing, a. k. (2018). microstructural characterization of failed aircraft antenna. international journal of engineering materials and manufacture, 3(4), 171-181. microstructural characterization of failed aircraft antenna premkumar manda, aginaparru sambasiva rao, satyapal singh and ashok kumar singh abstract this paper presents the failure analysis of aircraft antenna which is a sub-assembly of traffic collision avoidance system (tcas) used with air traffic control (atc) transponder. the base of the damaged antenna (metallic part) is made from al-based alloy. the micrographs exhibit the typical solidification microstructure consisting of al-rich matrix along with siand mg-si-ferich phases. the antenna is coated with the paint consisting of three layers. first and third layers display the presence of ti and c while second layer consists of si, cr and c elements. the small amount of oxygen is also present in all the three layers. the cracks are appeared in the central region of the fin due to impact of external objects (appears to be blankings and particles). three types of foreign object damage particles are observed on the damaged / hit area. the antenna appears to be damaged during gale as a result of hitting of the large particles lying in aircraft parking area and aircraft engine blankings. keywords: aircraft antenna; traffic collision and avoidance system; scanning electron microscopy; electron probe micro analyser; fibre particles. 1 introduction the growth of airline industry has taken place exponentially during last decade. the increase in number of aircrafts has added to the risk of mid-air collision. consequently, this has led to destruction of lives as well as massive loss of property. this has resulted in the development of advanced traffic collision and avoidance system (tcas) by the federal aviation administration (faa), other countries’ civil aviation authorities (caas), and the aviation industry after many years of extensive research, developments and flight evaluation [1-3]. the tcas assembly has been proposed by morell [4].the tcas is an assembly that provides a solution to the problem of reducing the risk of midair collision between aircrafts [1-6]. it is also known as airborne collision avoidance system (acas) in international arena. the tcas assembly recognizes the presence of nearby aircraft by interrogating the transponders carried by the same. it transmits interrogations at a steady rate (∼ once per second) and employs a receiver to detect replies to these interrogations from the transponders on nearby aircraft. when tcas senses a possible collision threat, it issues a traffic advisory to the pilot indicating the presence and location of the other aircraft. the tcas suggests an action plan if the encounter becomes dangerous [2-3, 7-10]. it functions based on time criteria to issue an alert and not the distance. it calculates a time to reach the closest point of approach (cpa) with the intruder after several successive replies and by dividing the range by the closure rate. as a result, the time value becomes the main parameter for issuing alerts. it also defines the type of alert. the large and smaller values indicate high and low alerts, respectively. if the aircraft transmit their altitude, the tcas accordingly computes the time to reach co-altitude [9-10]. the antenna, which is part of tcas, is employed in aircraft assembly to receive and transmit signals. it can be classified as navigation and communication depending on the application. the navigation antennas are air traffic control (atc), tcas distance measuring equipment (dme), weather radar (wxr), global positioning system (gps), automatic directional finder (adf), satellite communication (satcom), instrument landing system (ils), terminal wireless local area network (lan) unit (twlu), radio altimeter (ra) etc. while the communication antennas are very high frequency (vhf) and high frequency (hf) radios [11]. the locations of these antennas are schematically shown in fig. 1. received: 24 august 2018 accepted: 07 october 2018 published: 01 december 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 mailto:singh_ashok3@rediffmail.com microstructural characterization of failed aircraft antenna 172 the tcas assembly functions independently of ground based atc and provide collision avoidance protection [8]. the tcas antenna offers a directional reception of radio signals from atc transponders of other aircraft. it is also called directional antenna. this is installed below as well as above the fuselage (figs. 1 and 2). a sub-assembly of tcas which is an omni-directional antenna used with atc transponder has been received in damaged condition. this has been employed to transmit and receive aircraft code and altitude. this component has been found in damaged condition during the daily inspection of the aircraft immediately after experiencing gale with strong surface wind. the aircraft engine blankings came off, flew and rolled on the runway during gale. present work is thus concerned with the failure investigation of damaged aircraft antenna. figure 1: typical navigation and communication antennas locations of the boeing 787 aircraft [11]. figure 2: schematic diagrams of: (a) aircraft; (b) top and (c) bottom antenna. manda et al. (2018): international journal of engineering materials and manufacture, 3(4), 171-181 173 2 experimental visual examination was carried out on damaged aircraft antenna followed by photography in as-received condition. the x-ray radiography of the damaged antenna has been carried out to see the internal structure of the same (philips: model no: mg 452 with 450 kv).the chemical composition of the damaged aircraft antenna was determined using scanning electron microscopy (sem: leo 440i) and electron probe micro analyser (epma: sx 100 cameca). the foreign object damage (fod) particles were analysed using sem. the microstructural characterization was carried out using optical microscope (om), sem and epma. line scan profiles and x-ray mapping of elemental distribution were carried out using epma. the chemical composition of the metallic part of the antenna was obtained by epma and given in table 1. table 1−chemical composition of metallic part of damaged antenna (wt. %). the antenna was broken to see the fracture surface of the metallic part. fracture surface was examined in secondary electron (se) mode in sem. energy dispersive spectroscopy (eds) was employed for elemental analysis in the damaged area at different locations. 3. results 3.1. visual examination the photograph of the damaged antenna in as-received condition is shown in fig. 3. this clearly shows that the component has impact marks at the three distinct locations marked by a, b and c (fig.3). the enlarged views of these locations are shown in fig. 4 (a-c) corresponding to a, b and c locations (fig. 3), respectively. it appears that a hard object has hit the antenna at these locations. as a result, paint layer has either come out (figs. 4 (a and c)) or peeled off (fig. 4b). the hits at points a and c have created dent marks. the areas near point b have not displayed dents but the removal of paint layer only (fig. 4b). there appears to be thin layer of paint applied at the base of the fin in the past during servicing. the impact at a caused some damage to base of the antenna while the impact at c that happened to be the tip of the fin resulted in severe cracking in the middle of the fin due to bending forces created by impact of the high velocity object. the paint of the antenna is very hard and not easily scratched or damaged. this has been tested by hammering at the base of the antenna. the removal of paint at the tip of fin in fig. 4c therefore indicates that the fin has been hit by a quite hard object. this has resulted in damage observed in antenna. in addition, antenna also displays multiple cracks initiated from one end to other of the fin (fig. 3). the high magnification photographs of these cracks are shown in fig. 4 (d-f). these cracks are quite deep and appeared on both the side of antenna (fig. 4 (d-f)). 3.2. x-ray radiography the x-ray radiograph taken from the damaged antenna is shown in fig. 5. the blue lines are drawn on the radiograph to understand the internal structure of the component more clearly. the cracking observed is highlighted by white rectangular box (fig. 5). the parallel blue lines shown in the white rectangular box indicate the presence of light material due to absence of contrast in radiograph of that region. figure 3: the photograph of the damaged antenna in as-received condition. al mg si mn zn cu ti bal. 0.19 1.15 0.015 0.03 0.03 0.26 microstructural characterization of failed aircraft antenna 174 figure 4: (a), (b) and (c) are corresponding to enlarged views of the a, b and c locations (fig.3) displaying impact marks; (d), (e) and (f) are enlarged views of the antenna exhibiting multiple cracks at middle of the fin. figure 5: x-ray radiograph of the damaged antenna. cracking area is indicated by white rectangular box. 3.3. eds analysis and fractography the damaged antenna is broken to see the internal structure and mode of fracture. the photographs of the broken pieces are shown in fig. 6. these pieces are marked as x, y and z. the close view of piece marked as z is displayed in fig. 6b. the antenna consists of the three layers (top, middle and inner) as shown in fig. 6b. the internal structure of the antenna also consists of the connecting wire (fig. 6b). in order to know the layers compositions, the eds analysis has been carried out at different locations of the fig. 6b. the eds patterns taken from the top, middle and inner layers are shown in fig. 7 (a-c). the top layer exhibits the presence of c, o, ti, fe, al, si and ti elements (fig. 7a). this indicates the presence of the paint material. the eds pattern of the middle layer displays the presence of al, mg and si (fig. 7b). the middle layer is basically an albased alloy. the inner layer exhibits the presence of si, o and c (fig. 7c). it reflects that the inner layer is made up of si-based material. the dent mark at location a (fig. 3) reveals the presence of several foreign particles. these particles are marked as a, b, c, d and e on the se sem (secondary electron (se) mode in scanning electron microscopy (sem)) images and their corresponding eds patterns are shown in figs. 8-12. the particle marked as a is shown in fig. 8a and corresponding eds pattern is exhibited in fig. 8b. the eds pattern reveals the presence of na, o and cl along with manda et al. (2018): international journal of engineering materials and manufacture, 3(4), 171-181 175 the base material al. the particle b is shown in fig. 9a. the corresponding eds pattern is displayed in fig. 9b. it exhibits the presence of o and si indicating that the particle b is si rich. figure 6: broken pieces of the damaged antenna: (a) all pieces together and (b) close view of the z in (a). figure 7: the eds patterns taken from: (a) top, (b) middle and (c) inner layers of the fig.6b. figure 8: se sem image: (a) particle a in damaged portion of the antenna (location a) and (b) corresponding eds pattern of particle a. microstructural characterization of failed aircraft antenna 176 the se sem images showing fibre particles marked as c, d and e are shown in figs. 10-12. the fibre particle c (fig.10 (a and b)) exhibits the presence of c, o, al, si and ca elements. among these, the elements al is from the base material. the large amount of si in this particle probably appears partly from the base as well as from particles lying on the ground (aircraft parking area). the source of ca appears to be from the later particles. the fibre particle d (fig. 11 (a and b)) shows the presence of c, o, mg, al, si and fe. as mentioned above, the presence of these elements except al are due to particles lying on the ground. the fibre particle e (fig. 12 (a and b)) displays the presence of c, o, al, si and s. the elements like mg, al and si form the particles e are from the base material. the fracture surfaces taken from the location marked as w (fig. 6a) are shown in fig. 13. the fracture surface exhibits the presence of two distinct features (fig. 13b). these are marked with white and black square boxes. the high magnification images corresponding to fig. 13b (marked with white and black square boxes) are shown in fig. 13(c and d). the high magnification se sem image taken from the white square box (fig. 13b) is depicted in fig. 13c. this exhibits characteristic appearance of shrinkage casting dendrites. in addition, it also displays the presence of porosity. the high magnification se sem image taken from the black square box (fig. 13b) is shown in fig. 13d. the fracture surface exhibits the presence of dimples (marked by yellow arrows in fig. 13d) and flat facets (marked by blue arrows in fig. 13d). the type of fracture is mixed mode. figure 9: se sem image: (a) particle b in damaged portion of the antenna (location a) and (b) corresponding eds pattern of article b. figure 10: se sem image: (a) fibre particle c in damaged portion of the antenna (location a) and (b) eds pattern corresponding to fibre particle c. manda et al. (2018): international journal of engineering materials and manufacture, 3(4), 171-181 177 figure 11: se sem image: (a) fibre particle d in damaged portion of the antenna (location a) and (b) eds pattern corresponding to fibre particle d. figure 12: se sem image: (a) fibre particle e in damaged portion of the antenna (location a) and (b) eds pattern corresponding to fibre particle e. figure 13: the fracture surfaces of the location w of the fig. 6a: (a) low and (b) high magnifications. different features in (b) are shown as square white and black boxes; se sem high magnification images of fig. 13b corresponding to regions marked with: (c) white and (d) black square boxes. microstructural characterization of failed aircraft antenna 178 3.4. chemical composition and microstructure of base of the antenna (metallic part) the chemical composition of base of the damaged antenna (metallic part) determined from epma is shown in table 1. this indicates that it is made from al-based alloy. the optical microstructures of the as-received base of the antenna exhibit the typical solidification microstructure (fig. 14). it displays the presence of two phases namely, primary α-al phase with dendrites surrounded by the eutectic al-si (fig. 14 (a and b). optical microstructure taken from the edge showing different layers of paint (fig. 14 (c and d). the bse sem (back scattered electron (bse) mode in scanning electron microscopy (sem)) microstructures taken from the cross section of base of the antenna are shown in fig. 15. the microstructures exhibit the presence of three phases (matrix, grey and white as marked in fig. 15b). the epma x-ray elemental mapping has been carried out on these phases and results are shown in fig. 16. the distribution of al is displayed in fig. 16b. the elemental mappings of ti, fe, mg and si are exhibited in fig. 16 (c-f). it is clear from the fig. 16 that these microstructures consist of three phases. these are al-rich matrix along with si-rich (grey) and mg-si-fe rich (white) precipitates. figure 14: optical microstructures of the base of the antenna: (a) low and (b) high magnifications; optical microstructure taken from the edge showing different layers of paint: (c) low and (d) high magnifications. figure 15: the bse sem microstructures of cross section of the base of the antenna: (a) low and (b) high magnifications. manda et al. (2018): international journal of engineering materials and manufacture, 3(4), 171-181 179 figure 16: epma x-ray elemental mappings of cross section of base of the antenna: (a) bse image (b) al, (c) ti, (d) fe, (e) mg and (f) si distributions in corresponding bse image. figure 17: (a) bse epma image taken from the edge consisting of three layers of paint. the region of line scan on paint is shown by double arrow (in red colour) and (b) epma elemental line scans taken from the double arrow shown in red colour in fig. 17a. microstructural characterization of failed aircraft antenna 180 the optical microstructures taken from the edges show the paint layer at the edges (fig. 14 (c and d).the paint is shown by double arrows in fig. 14 (c and d). the high magnification image (fig. 14d) exhibits that the paint consists of three layers. these layers are marked as 1, 2 and 3 (fig. 14d). the thicknesses of layers 1, 2 and 3 are ∼ 25, 50 and 90 µm, respectively. the microstructures and paint shown in fig. 14 have been investigated in detail by epma. the epma elemental line scans of the paint (shown in fig.14) are exhibited in fig. 17. as mentioned above, paint consists of three layers (figs. 14 and 17). the first and third layers display the presence of ti and c while second layer shows the si, cr and c elements (fig. 17b). the small amount of oxygen is also present in all the three layers. 4. discussions the chemical composition determined from the epma indicates that the metallic part of antenna is made up of albased alloy (al-mg-si). the microstructure exhibits the presence of solidification microstructure indicating that the metallic part of antenna is made in as-cast condition of the material. the as-cast material shows the presence of three phases namely; al-rich matrix along with si-rich (grey) and mg-si-fe rich (white) precipitates (figs. 14 and 15). similar microstructural features are also reported elsewhere in as-cast al-mg-si alloy [12]. impact of the object with the antenna has removed paint only. no cracking is observed in the metallic part of the antenna. the x-ray radiograph of the damaged antenna reveals that the presence of severe cracking in middle part of the fin which is made up of a si based material (fig. 5). the cracks are appeared in the central region of the fin due to impact of an external object (appears to be blankings and particles in the present case). x-ray radiography observations also show that the fin has been cracked at locations where only si based material is present inside the fin structure. cracking observed is highlighted with the white rectangular box (fig. 5). this can be attributed to hitting of the object at the top of the fin (location c of fig. 3). as mentioned above, the paint consists of three layers with different thicknesses. chemical compositions of the layers 1 and 3 (fig. 14d) are same while the layer 2 is different. as a result, the contrast of the layers 1 and 3 are nearly same in optical microstructure. three layers are intact with the metallic part. as mentioned above, the fracture surfaces exhibits two distinctive features: (i) shrinkage casting dendrites along with porosity and (ii) ductile dimples and flat facets. hossain and kurny [13] have observed the similar fracture features in as-cast al-si-mg alloy with cu contents. jerner has also reported the similar fracture features in as-cast aluminium alloy [14]. the location a (fig. 3) exhibits the presence of three types of fod particles namely small particles and fibres. the small fod particles (a and b) display the presence of o, na, al, cl (fig. 8) and o, si elements (fig. 9). the former and later particles are cl and si rich, respectively. the presence of al particularly in particle a is from the base material. the source of small fod particles might have come probably from the ground (aircraft parking area) during gale. the se sem images (figs. 10-12) display that these particles are fibres (third type fod particle). the fibre particles exhibit the presence of c, o, ca, s and fe apart from the base material elements (al, mg and si). these fibre particles are undamaged (fig. 10a), damaged (fig. 11a) and bent (fig. 12a). the lengths of fibre particles are different at different regions in location a. however, these fibre particles display two distinct compositions: (i) the particles c and d mainly consists of si, ca, o, c and mg. the main source of these particles appears to be large particles lying on the aircraft parking area. these particles might have hit the antenna during gale. (ii) the particle e reflects the presence of c as major element. it appears that the source of this particle is from the aircraft engine blanking material. it has been reported that the aircraft engine blanking material is made up of c fibres. it emerges that all the three types of particles as mentioned above might have hit the antenna during gale. surprisingly, the location c (fig. 3) does not show the presence of fod particles. this can probably be attributed to extent of hitting which is not sufficient to leave any fod particles at the location c (fig. 3). 5. conclusions microstructural attributes of failed aircraft antenna in both the un-damaged and impact mark regions have been investigated. the main findings of the results are summarized below. (a) the antenna appears to be damaged due to hitting of the large particles lying in aircraft parking area and aircraft engine blankings during gale. (b) three types of fod particles are observed on the damaged / hit area. the small fod particles appear to come from the ground during gale. the large numbers of fod particles are in the form of fibres. (c) the source of fibre fod particles is from aircraft engine blankings material. acknowledgements authors acknowledge defence research and development organisation for financial support. we are grateful to dr vikas kumar, director, defence metallurgical research laboratory for his kind encouragement. authors thank members of emg, sfag, photography and radiography groups of dmrl for their kind help during investigation. manda et al. (2018): international journal of engineering materials and manufacture, 3(4), 171-181 181 references 1. murugan s and oblah aa.tcas functioning and enhancements, international journal of computer applications (0975-8887) 2010; 1: 45-49. 2. harman wh, “tcas: a system for preventing midair collisions”, in the lincoln laboratory journal 1989; volume 2. 3. de d, chattoraj n, a review: theoretical analysis of tcas antenna: traffic collision avoidance system for aircrafts, ieee international conference on green computing, communication and electrical engineeringicgccee’14. 4. m.j. kochenderfer, decision making under uncertainty: theory and approaches, the mit press, cambridge, england 2015. 5. a.l.u. roberts and s.j. peimber, air traffic control system, us patent 9245451, 2016. 6. j. tang, m.a. piera, y. ling and l. fan, extended traffic alert information to improve tcas performance by means of causal models, mathematical problems in engineering, article id 303768, 2015, 1-11. 7. u.s. department of transportation (federal aviation administration); “introduction to tcas ii”, version 7.1, february 28, 2011. 8. henely s, tcas ii, chapter 18, avionics handbook, crc press llc, 2001. 9. kim wiolland. “traffic alert collision avoidance system, uncovered”. 10. welch jd and orlando va, traffic alert and collision avoidance system (tcas): a functional overview of minimum tcas ii, project report, atc-119, dot/faa/pm-83/10. 11. boeing proprietary, copyright© boeing, rev 1.0, 3-2. 12. boromei i, ceschini l, morri al, morri an, nicoletto g, riva e, influence of the solidification microstructure and porosity on the fatigue strength of al-si-mg casting alloys, metallurgical science and technology 2010; 28-2: 1824. 13. hossain a, kurny asw, effects of strain rate on tensile properties and fracture behavior of al-si-mg cast alloys with cu contents, materials science and metallurgy engineering 2013: 1: 27-30. 14. jerner, http://www.metallurgist.com/atvrollover.html. http://www.metallurgist.com/atvrollover.html international journal of engineering materials and manufacture (2018) 3(3) 122-133 https://doi.org/10.26776/ijemm.03.03.2018.01 experimental study of heat transfer enhancement through a tube with wire-coil inserts at low turbulent reynolds number mohammad zoynal abedin and m. a. rashid sarkar abstract this paper reports an experimental analysis to investigate the enhancement of turbulent heat transfer flow of air through one smooth tube and four different tubes with wire-coil inserts (pitches, pc = 12, 24, 40, and 50 mm with corresponding helix angles, α =100, 200, 350, and 450, respectively) at low reynolds numbers ranging from 6000 to 22000. the test section of the tube was electrically heated and was cooled by fully developed turbulent air flow. the performance of the tubes was evaluated by considering the condition of maximizing heat transfer rate. from the measured data, the heat transfer characteristics such as heat transfer coefficient, effectiveness and nusselt number, and the fluid flow behaviours such as friction factor, pressure drops and pumping power along the axial distance of the test section were analyzed at those reynolds numbers for the tubes. the results indicated that for the tubes with wirecoil inserts at low reynolds numbers, the turbulent heat transfer coefficient might be as much as two-folds higher, the friction factors could be as much as four-folds higher, and the effectiveness might be as much as 1.25 folds higher than those for the smooth tube with similar flow conditions. a correlation was also developed to predict the turbulent heat transfer coefficients through the tubes at low reynolds numbers. keywords: heat transfer enhancement, wire-coil inserts, low reynolds number, friction factor, effectiveness. nomenclature cp specific heat at constant pressure, kj/(kg k) dw diameter of wire coil, m di inside diameter of tube, m e effectiveness of the exchanger fi fanning friction factor, [{(−∆p/x)di}/(2ρv2)] h convective heat transfer coefficient, w/ (m2 k) k thermal conductivity, w/(m k) l length of the test section, m nu nusselt number, hdi /k p pressure, pa pc pitch of the coil, mm pm pumping power, w pr prandtl number, µcp /k re reynolds number, v di /ν tb bulk temperature of air, °c tw wall and coil surface temperature, °c received: 30 april 2018 accepted: 21 june 2018 published: 15 september 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 m. z. abedin1 and m. a. r. sarkar2 1department of mechanical engineering dhaka university of engineering and technology gazipur 1700, bangladesh e-mail: abedin.mzoynal@duet.ac.bd 2department of mechanical engineering bangladesh university of engineering and technology dhaka 1000, bangladesh e-mail: rashid@me.buet.ac.bd reference: abedin, m. z. and sarkar, m. a. r. (2018). experimental study of heat transfer enhancement through a tube with wirecoil inserts at low turbulent reynolds number. international journal of engineering materials and manufacture, 3(3), 122-133. experimental study of heat transfer enhancement through a tube with wire-coil inserts at low turbulent reynolds number v mean velocity of air inside tube, m/s x axial distance, m greek symbols: α helix angle of coil, deg. ∆p pressure drop along axial length, pa ρ density of air, kg/m3 µ viscosity, pas ν kinematic viscosity, m2/s subscripts: avg average condition i inlet condition o outlet condition 1 introduction heat transfer enhancement is of very importance considering its practical applications in many engineering and environmental fields. therefore, an increasing trend of conducting research about the concept of enchantment has received a tremendous attention of many scientists and engineers in the fast few decades [1]. especially, in the processes of industrial applications, heat exchangers are found to be responsible for transferring more than 80% of energy which emphasizes the importance of heat transfer enhancement [2]. generally, three main categories are considered for the enhancement techniques. the first one is called the active method which involves some external power to achieve the desired flow condition and the method is rarely used in the practical design applications due to its complexity in providing the external power in many applications. the second one is the passive method which does not require external power, but sometimes, the additional power is originated from the power of the fluid motion in the cases of the tubes with insert devices. the third one is the compound method consisting of both active and passive methods and the method has limited applications due to its complex design procedures [3]. the compound method mostly deals with the passive method that leads to have wide applications in many engineering fields such as in the heat recovery processes, refrigeration and air conditioning systems and dairy processes. in case of passive method in a tube with different inserts, the mechanism introduces some swirls into the flow field and produces periodic redevelopment of the boundary layer that increases the turbulence intensity, and finally enhances the effective heat transfer rate [4]. among the enhancement techniques, the tube with wire coil inserts is considered to be the superior due to its lower cost, easy installation, and unchanged original smooth tube mechanical strength [5]. the heat transfer enhancement for servotherm medium-grade oil in a laminar flow through one smooth tube and seven wire-coils inserted tubes of varying wire diameter and pitch of wire coil was experimentally investigated by uttarwar and rao [6]. in their studies, it was revealed for wire-coil inserted tubes that as much as 350% heat transfer enhancement might be found and as much as 80% reduction in heat-exchanger area could be achieved by considering the pumping power and basic geometry as constant. for the heat transfer enhancement, many augmentation techniques have been developed and made practicable with a significant heat transfer improvement. for instances, the heat transfer enhancement in the heat-exchanger tubes could be achieved not only with internal fin [7-9], twisted-tape inserts [10-18], metallic filament inserts [19], brush inserts [20], longitudinal strip inserts [21], but also with internal roughness [22], and so on. on the other hand, some numerical investigations were conducted for the predictions of fluid flow behaviours and heat transfer through tubes with fins [23-26]. the experimental investigations on turbulent flow heat transfer and fluid friction in a 25 mm inner diameter copper tube, tightly fitted with helical wire-coil inserts of varying pitch and wire diameter were carried out by sethumadhavan and rao [27]. recently, vahidifar and kahrom [28] experimentally studied the heat transfer enhancement in a heated tube caused by wire-coil and rings, and found that the overall enhancement efficiency increased as much as 128%. garcia et al. [29] also investigated the heat transfer enhancement for the laminar and transitional flow in the wire coil inserted tubes. sarkar et al. [30] experimentally investigated the heat transfer enhancement in turbulent flow through the tubes with wire-coil inserts with varying pitches. in their studies, it was revealed that as much as two-fold heat transfer improvement might be found and as much as four-fold friction factor could be achieved for wire-coil inserted tubes for various flows having reynolds numbers ranging from 20000 to 45000. although the heat transfer enhancement both in laminar and turbulent flows with various augmentation techniques have been clarified to some extent, no approach of the experimental investigations for the improvement of heat transfer coefficients through a tube with wire-coil inserts at low reynolds numbers has so far been reported. therefore, in the present study, we have investigated experimentally the heat transfer enhancement in a turbulent air flow through one smooth tube and four wire-coil inserted tubes at low reynolds numbers ranging from 6000 to 22000. 123 abedin and sarkar (2018): international journal of engineering materials and manufacture, 3(3), 122-133 figure 1: schematic of the experimental set-up. figure 2: cross-sectional view of the test section. 2 experiment 2.1 experimental facility figure 1 shows the schematic drawing of the experimental apparatus to be used for analyzing the heat transfer enhancement. the experimental procedures could be better explained by describing the following section and system such as test section, air supply system, heating system and measurement system. 2.1.1 test section the experimental procedure of the present study is the same as previously described in the experimental study of the turbulent heat transfer enhancement through a smooth tube and four tubes with wire-coil inserts at the reynolds numbers ranging from 20000 to 45000 published in the report of sarkar et al. [30]. the test section is prepared by a brass tube of 1500 mm length (l) and 70 mm inside diameter (di) where the wire coils of different pitches are inserted. the mild steel wire coil is made by tightly wrapping a coil of spring on a circular rod which is shown in figure 2. the outside diameter of the wire coil is slightly larger than the inside diameter of the smooth tube so that the coil may be tightly fitted against the tube wall. the wire coil having a wire diameter (dw) of 3.25 mm is inserted into the smooth tube. after inserting the coil, the two halves of the smooth tubes are clamped and the pudding is pressed into the joint of the tube to prevent any leakage. the test section is wrapped at first with a mica sheet and then a glass-fiber tape before wrapping with nichrome wire (which is used as an electric heater and the resistance of wire is of 0.249 ω/m for smooth tube and of 0.739 ω/m for coil-inserted tubes) spirally wound around the tube with 16 mm uniform spacing. then again a mica sheet, a glass-fiber tape, a heat-insulating tape, and an asbestos tape are used sequentially over the wrapped nichrome wire. the test section is installed in the test facility with the help 124 experimental study of heat transfer enhancement through a tube with wire-coil inserts at low turbulent reynolds number of the bolted flanges, between which asbestos sheets are inserted to prevent the heat flow in the longitudinal direction. an unheated inlet section (sometimes called shaped inlet) casted from aluminum having the same diameter of test section is installed upstream of the test section. the shaped inlet having a length of 533 mm is made integral to avoid any flow disturbances at upstream of the test section in order to get a fully developed air flow in the test section. 2.1.2 air supply system in air supply system, a motor operated suction-type fan is fitted downstream of the test section so that any disturbance produced by the fan does not affect the flow on the test section. in order to minimize the head loss at the suction side, a 120 diffuser of mild steel plate is fitted to the suction side of the fan. to arrest the vibration of the fan a flexible duct is installed between the inlet section of the fan and the gate valves. the gate valves which are known as the butterfly valves installed in order to control the flow rate of air. the butterfly valve consists of a metal circular disk or vane with its pivot axes at right angles to the direction of flow in the tube. to maintain the low turbulent flow at the required reynolds numbers in the range of re = 6000 to 22000 for air inside the tube, two butterfly valves are used from which one value is fitted at the suction side of the tube and other valve is fitted at the lateral position of the main tube. both valves are installed at the upstream of the flexible duct of the tube. 2.1.3 heating system in heating system, a nichrome wire is wounded around the brass tube which provides a constant heat flux when it is connected to a power supply of 5 kva which are maintained with the help of a magnetic contactor and temperature controller. the temperature controller is fitted to sense the outlet air temperature by providing the signal in switching the heater off or on automatically. the on-off switch is provided mainly for the safety purpose during the excess heating of the test section. heat input by nichrome wire is kept constant during the experimental work and is evaluated by measuring the values of current and voltage supplied to the heating element. 2.1.4 measurement system in measurement system, the air flow velocity, the static pressure and the temperature are measured from the experiment. the mean velocity of air flow is measured at the inlet of the test section with the help of a traversing pitot tube. in order to measure the static pressure, the pressure tappings arrangement are fitted so carefully that it just touches the inner surface of the test section and u-tube water manometers at an inclination of 30° are also attached with the pressure tappings. to measure the temperatures of the wall and coil surfaces at the different axial locations of the test section, k-type thermocouples are used and connected with the selector switch and process meter. for smooth tube, 8 thermocouples are fitted at eight equally spaced axial locations of the test section to measure the wall temperatures. for coil-inserted tubes, sixteen thermocouples are fitted at eight locations. at each location, two thermocouples are fitted to measure the wall and the coil surface temperature of the test section. 2.2 experimental procedure at first the fan is operated by pressing the switch as ‘on’ and later the fan is kept running for about five minutes to have the transient characteristics died out. the flow of air is set to a desired value and kept constant with the help of butterfly valves and the air flow is recorded with a traversing pitot tube fitted at the inlet section of the tube. then the electric heater is switched on and the electric power is adjusted (if necessary) with the help of a regulating transformer or variac. steady state condition for temperature at different locations of the test section is defined by gee and webb [22] by two measurements. the variation in wall temperature is observed until constant values are attained, then the outlet air temperature is monitored. steady state condition is attained when the outlet air temperature does not deviate over 10-15 minutes time during the process. at the steady state condition, thermocouple of k-type readings are recorded manually with the help of rotary selector switch and the readings include the air inlet and outlet temperatures, coil surface temperatures and tube wall temperatures. at the same time, manometer readings that indicate the pressure drops along the length of the test section are collected with the help of an inclined u-tube manometer. after each experimental run, the reynolds number is changed with the help of butterfly valves for keeping a constant electrical power input. and after reaching the steady state condition, the readings of thermocouple, pressure tappings and traversing pitot tube are recorded. in a similar fashion, the four test sections are arranged for four different pitches (pc = 12, 24, 35 and 50 mm with corresponding helix angles, α = 10°, 20°, 35° and 45°) with a wire coil of mild steel with a diameter of 3.25 mm. 3 results and discussions on the basis of the present experimental statistics by considering as much as 5% uncertainty of the different measured quantities [31], the fluid flow characteristics such as friction factors, pressure drops and pumping powers, and the heat transfer characteristics such as heat transfer coefficients, average nusselt numbers and heat transfer effectiveness are analyzed and presented in the following section. in addition, a correlation is developed for the prediction of heat transfer coefficients both for smooth tube and tubes with wire-coil-inserts at low reynolds numbers, and finally, a comparative study is also demonstrated between the present results and the predicted results obtained for the higher reynolds number by sarkar et al. [30]. 125 abedin and sarkar (2018): international journal of engineering materials and manufacture, 3(3), 122-133 3.1 friction factor the average friction factors, fi for a smooth tube and four wire coil-inserted tubes against the reynolds numbers, re are shown in figure 3. as seen in the figure, the average friction factor gradually decreases with the increase of reynolds number for the smooth tubes and the tubes with wire-coil inserts. the reason behind such a decreasing trend of friction factor is that at higher reynolds number, a thin hydrodynamic boundary layer may be formed which causes a minimum value of the friction factors. it is also depicted that the value of friction factors for wire coil-inserted tubes becomes higher than that of the smooth tube and the average friction factor for the tube with a higher helix angles become lower than that of the tube with a lower helix angle. this fact implies that at a lower value of reynolds number corresponding to lower flow rate, air just passes over the wire coil and the presence of small vortices behind the wire coil results an increasing trend in the friction factor. however, as the flow rate is increased, a secondary flow and hence some turbulences are induced in the flowing fluid due to the presence of a wire coil, which also provides an increasing trend in the higher values of pressure drops. again, the average friction factor increases with the decrease of the helix angle due to the higher vortices generated behind the wire coils and this similar behavior is also shown for the profiles of the friction factors at higher reynolds numbers (sarkar et al., [30]). it is noted that the local friction factor gets higher value near the entrance region, then sharply falls up to x/l = 0.3, after which it remains almost constant specifying the fully developed flow (not shown in figure). the higher friction factor at the entrance region may be attributed to presence of asbestos plate between the sharp inlet and test section. it can be indicated that the average friction factor for the tubes with wire–coil-inserts at low reynolds numbers increases as much as 3.5 times higher than that of the smooth tube. figure 3: variation of average friction factor against reynolds number for smooth tube and wire-coil inserted tubes. 3.2 pressure drop figure 4 shows the average pressure drops, ∆p for a smooth tube and the tubes with wire-coil-inserts against reynolds numbers, re. it can be seen from the figure that the average pressure drop gradually increases with the increase of reynolds number for all tubes. also, the profiles of the average pressure drops for the coil-inserted tubes becomes higher than that of the smooth tube and the pressure drops for a tube with a lower helix angle become higher than that of the tube with the higher helix angle in analogy with the profiles of an average friction factors as shown in figure 3. figure 4: variation of average pressure drop against reynolds number for smooth tube and wire-coil inserted tubes. 5000 10000 15000 20000 2500 0 0.1 0.2 0.3 reynolds number, re fr ict ion fa cto r, fi tube no. symbol pitch (mm) α(deg.) 0 (smooth) ∞　 　 - 1 12 10 2 24 20 3 40 35 4 50 45 5000 10000 15000 20000 2500 0 5 10 15 20 25 30 35 reynolds number, re pre ssu re dr op , δ p tube no. symbol pitch (mm) α(deg.) 0 (smooth) ∞　 　 - 1 12 10 2 24 20 3 40 35 4 50 45 126 experimental study of heat transfer enhancement through a tube with wire-coil inserts at low turbulent reynolds number figure 5: variation of average pumping power against reynolds number for smooth tube and wire-coil inserted tubes. 3.3 pumping power the variation of the pumping powers, pm both for the smooth tube and the tubes with wire-coil inserts are shown against reynolds numbers, re in figure 5. as seen in the figure, the pumping power for all tubes increases as the reynolds number increases and the pumping power of wire-coil inserted tubes become higher than that of the smooth tube. the presence of small vortices behind the wire coil is responsible for higher pressure drops as previously described in the friction factor shown in figure 3, and consequently the pumping power increases. it is noted that the required pumping power for the tubes with wire-coil-inserts at low reynolds numbers varies as much as two times higher than that of the smooth tube. 3.4 average heat transfer coefficients figure 6 depicts the variation of average heat transfer coefficients, h against the reynolds number, re for the smooth tube and the tubes with wire-coil inserts. it can be seen from the figure that the average heat transfer coefficient increases with the reynolds numbers for all tubes. the local heat transfer coefficient is large at the entrance of the test section due to the development of thermal boundary layer and the coefficient decreases sharply along the axial distance up to x/l = 0.3, after which it remains nearly constant demonstrating the fully-developed thermal boundary layer (not shown in figure). it can be also seen that the average heat transfer coefficient for the tubes with wire-coilinserts becomes higher than that of the smooth tube and the coefficient for a higher helix angles corresponds to a higher value in comparison with those of the tube with a lower helix angle. it can be noted that the average heat transfer coefficient for the tubes with wire-coil-inserts increases as much as two-fold as compared to that of the smooth tube for a comparable reynolds numbers. figure 6: variation of average heat transfer coefficients against reynolds number for smooth tube and wire-coil inserted tubes. 5000 10000 15000 20000 2500 0 0.2 0.4 0.6 reynolds number, re pu mp ing po we r, p m tube no. symbol pitch (mm) α(deg.) 0 (smooth) ∞　 　 - 1 12 10 2 24 20 3 40 35 4 50 45 5000 10000 15000 20000 25000 0 10 20 30 40 50 60 70 reynolds number, re av era ge he at tra ns fer co eff ici en t, h tube no. symbol pitch (mm) α(deg.) 0 (smooth) ∞　 　 - 1 12 10 2 24 20 3 40 35 4 50 45 127 abedin and sarkar (2018): international journal of engineering materials and manufacture, 3(3), 122-133 figure 7: variation of average nusselt number against reynolds number for smooth tube and wire-coil inserted tubes. 3.5 average nusselt number the variation of the average nusselt numbers, nu both for the smooth tube and the tubes with wire-coil inserts are shown against reynolds numbers, re in figure 7. as shown in the figure, the average nusselt number increases with the increase of reynolds number and the average nusselt numbers for wire coil-inserted tubes become higher as compared with that of the smooth tube. it can be seen from the figure that the average nusselt numbers for a tube with higher helix angle become higher than that of the tube with lower helix angle. the local nusselt number is large in the entrance region due to the development of thermal boundary layer with the entrance section at the leading edge and then gradually decreases up to a certain point (x/l = 0.3), after which the thermal boundary layer could be considered fully developed as described previously. the reason behind the higher local nusselt number with reynolds number is that a higher flow rate results in an increment of local nusselt number at tube surface (not shown in figure). 3.6 effectiveness the analysis of the heat transfer effectiveness, e is of very importance for many engineering applications. the heat transfer effectiveness both for smooth tube and wire-coil inserted tubes is considered by considering the constant wall temperature and may be defined as e = (tbo − tbi)/(twavg − tbi). the symbols tbo, tbi represent the bulk temperature based on outside diameter and inside diameter, respectively, and twavg represents average wall temperature of coil surface. figure 8 depicts the variation of average heat transfer effectiveness both for smooth tube and the tubes with wire-coil inserts as a function of reynolds number, re. it can be seen from the figure that the heat transfer effectiveness increases with the increase of reynolds number. it can be indicated that for a comparable reynolds number, the heat transfer effectiveness for wire-coil inserted tubes varies as much as 1.25 times higher than that of the smooth tube. figure 8: variation of average effectiveness against reynolds number for smooth tube and wire-coil inserted tubes. 5000 10000 15000 20000 250 0 50 100 150 200 reynolds number, re av er ag e n us se lt nu m be r, n u tube no. symbol pitch (mm) α(deg) 0 (smooth) ∞　 　 - 1 12 10 2 24 20 3 40 35 4 50 45 5000 10000 15000 20000 2500 0.2 0.4 0.6 0.8 1 reynolds number, re ef fec tiv en es s, e tube no. symbol pitch (mm) α(deg.) 0 (smooth) ∞　 　 - 1 12 10 2 24 20 3 40 35 4 50 45 128 experimental study of heat transfer enhancement through a tube with wire-coil inserts at low turbulent reynolds number 3.7 prediction of heat transfer coefficients as mentioned above, the variation of an average heat transfer coefficient is a function of the reynolds number for both smooth tube and wire-coil inserted tubes. it is evident that the nusselt number for smooth tube and with wirecoil inserted tubes is a function of the reynolds number and the helix angle of the coil. these may be correlated by the equation as follows. nu = c re m pr 0.33 (1) the slope of the straight line for equation (1) is obtained from the graph plotted on (nu/pr 0.33) vs. re as shown in figure 9. as seen in figure 9, the average nusselt number representing as nu/pr0.33 increases with reynolds number in a similar way as shown in figure 7. the coefficient c of equation (1) is plotted against tanα in figure 10. as seen in figure 10, the value of c varies with tanα, where the values of tanα represent the tangent values of the helix angle of the wire coil, and hence, the variation of c with tanα can be represented by the relation as follows. c = 0.0071 (tanα) 2 − 0.0124 tanα+ 0.0057 (2) on the other hand, the exponent m of equation (1) is plotted against tanα in figure 11. as seen in figure 11, the value of m varies with tanα, where the values of tanα represent the tangent values of the helix angle of the wire coil as described previously, and hence, the variation of m with tanα can be represented by the relation as follows. m = − 0.3971 (tanα) 2 + 0.6994 tanα+ 0.9286 (3) the final correlation of the nusselt number with the reynolds number and helix angles can be predicted as follows. nu = [0.0071(tanα) 2 −0.0124 tanα+ 0.0057]×re [0.3971 (tanα) 2 + 0.6994 tanα+ 0.9286] × pr0.33 (4) figure 9: variation of average nusselt number (nu /pr 0.33) against reynolds number for smooth tube and wire-coil inserted tubes. figure 10: variation of c against tanα for smooth tube and wire-coil inserted tubes. 5000 10000 15000 20000 2500 0 50 100 150 200 reynolds number, re av era ge n uss elt nu mb er, nu / p r 0 .33 tube no. symbol pitch (mm) α(deg.) 0 (smooth) ∞　 　 - 1 12 10 2 24 20 3 40 35 4 50 45 0 0.2 0.4 0.6 0.8 1 1.2 1.4 -0.015 -0.01 -0.005 0 0.005 0.01 0.015 tanα c c = 0.0071(tanα)20.0124tanα+0.0057 129 abedin and sarkar (2018): international journal of engineering materials and manufacture, 3(3), 122-133 the average heat transfer coefficients found in the present experimental study are predicted by applying the correlation developed-above in equation (4). figures 12-16 show the prediction of the average nusselt numbers both for the smooth tube and the tubes with wire-coil inserts along, and they are compared with the predicted statistics of the heat transfer coefficients for higher reynolds numbers (sarkar et al., [30]). figure 12 demonstrates the predicted heat transfer coefficients represented by average nusselt number, nu against reynolds number, re for smooth tube. as can be seen in figure 12, the average nusselt number predicted by equation (4) corresponds well with the present experimental results for smooth tube for low reynolds number. the predicted average nusselt number also agrees well with the values predicted by sarkar et al., [30] for higher reynolds number. the predicted heat transfer coefficients represented by average nusselt number, nu against reynolds number, re for wire-coil-inserted tube (pitch, pc = 12 mm, helix angle, α = 100) is depicted in figure 13. as can be seen in figure 13, the average nusselt number predicted by equation (4) corresponds relatively well with the present experimental results for wire-coil-inserted tube for low reynolds number. however, the predicted average nusselt number agrees very well with the values predicted by sarkar et al., [30] for higher reynolds number. figure 14 demonstrates the predicted heat transfer coefficients represented by average nusselt number, nu against reynolds number, re for wirecoil-inserted tube (pitch, pc = 24 mm, helix angle, α = 200). as can be seen in figure 14, the average nusselt number predicted by equation (4) does not correspond well with the present experimental results for wire-coil-inserted tube for low reynolds number. however, the predicted average nusselt number does not agree with the values predicted by sarkar et al., [30] for higher reynolds number. figure 15 demonstrates the predicted heat transfer coefficients represented by average nusselt number, nu against reynolds number, re for wire-coil-inserted tube (pitch, pc = 40 mm, helix angle, α = 350). as can be seen in figure 15, the average nusselt number predicted by equation (4) also does not correspond well with the present experimental results for wire-coil-inserted tube for low reynolds number. however, the predicted average nusselt number does not agree with the values predicted by sarkar et al., [30] for higher reynolds number. figure 11: variation of m against tanα for smooth tube and wire-coil inserted tubes. figure 12: prediction of heat transfer coefficients for smooth tube. 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0.6 0.8 1 1.2 1.4 tanα m m = 0.3971(tanα)2+0.6994tanα+0.9286 5000 10000 15000 20000 25000 0 20 40 60 80 100 reynolds number, re av er ag e n us se lt nu m be r, nu air ( pr = 0.71) present prediction rashid sarkar et al. 130 experimental study of heat transfer enhancement through a tube with wire-coil inserts at low turbulent reynolds number figure 13: prediction of heat transfer coefficients for wire-coil inserted tube (pitch, pc = 12 mm, helix angles, α = 100). figure 14: prediction of heat transfer coefficients for wire-coil inserted tube (pitch, pc =24 mm, helix angles, α =200). figure 15: prediction of heat transfer coefficients for wire-coil inserted tube (pitch, pc =40 mm, helix angles, α = 350). 5000 10000 15000 20000 25000 0 50 100 150 200 reynolds number, re a ve ra ge n us se lt nu m be r, nu air ( pr = 0.71) present prediction rashid sarkar et al. 5000 10000 15000 20000 2500 0 50 100 150 200 reynolds number, re av er ag e n us se lt nu m be r, n u air ( pr = 0.71) present prediction rashid sarkar et al. 5000 10000 15000 20000 2500 0 50 100 150 200 reynolds number, re av er ag e n us se lt nu m be r, n u air ( pr = 0.71) present prediction rashid sarkar et al. 131 abedin and sarkar (2018): international journal of engineering materials and manufacture, 3(3), 122-133 figure 16: prediction of heat transfer coefficients for wire-coil inserted tube (pitch, pc =50 mm, helix angles, α =450). the predicted heat transfer coefficients represented by average nusselt number, nu against reynolds number, re for wire-coil-inserted tube (pitch, pc = 50 mm, helix angle, α = 450) is depicted in figure 16. as can be seen in figure 16, the average nusselt number predicted by equation (4) corresponds very well with the present experimental results for wire-coil-inserted tube for low reynolds number. however, the predicted average nusselt number does not agree with the values predicted by sarkar et al., [30] for higher reynolds number. it can be seen from those figures that the average nusselt number predicted by equation (4) agrees relatively well with the experimental results both for smooth tube and wire-coil inserted tubes except for the tubes with helix angles of α = 20° and 35°. 4. conclusions an experimental investigation has been conducted to study the heat transfer enhancement in turbulent flow of air through one smooth tube and four wire-coil inserted tubes. the study has revealed that the wire-coil inserted tubes would enhance a heat transfer rate at the cost of increased pumping power. the results of the present experimental study may be summarized as follows. • for comparable reynolds numbers, the friction factor for the wire-coil inserted tubes becomes as much as fourfolds higher than those observed in the smooth tube. the local friction factor is high near the inlet section and drops gradually to the fully developed flow. • the average heat transfer coefficient for tube with wire-coil-inserts increases as much as two-fold in comparison with that of the smooth tube for similar flow condition. • for comparable reynolds numbers, the heat transfer effectiveness for the wire-coil inserted tubes increases as much as 1.25 folds than that of the smooth tube. acknowledgement the authors wish to express their gratitude to former professor a. m. azizul hoq of the department of mechanical engineering, bangladesh university of engineering and technology (buet), for his continuous support and important suggestions in the modifications of the experimental setup during the present work. also, the authors are thankful to mr. m. zaidul islam of the department of mechanical engineering, buet, for his cooperation. reference 1. shailendhra, k., & anjali devi, s. p. (2011). on the enhanced heat transfer in the oscillatory flow of liquid metals. journal of applied fluid mechanics, l. 4, 57-62. 2. he, y., zeng, h., zhang, q., tang, y., & zhang, j. (2012). analysis of enhanced heat transfer performance through duct with constant wall temperature. journal of thermodynamics and heat transfer, 26(3), 472-475. 3. jafari nasr, m. r., habibi khalaj, a., & mozaffari, s. h. (2010). modeling of heat transfer enhancement by wire coil inserts using artificial neural network analysis. journal of applied thermal engineering, 30, 143-151. 4. gunes, s., ozceyhan, v., & buyukalaca, o., (2010). heat transfer enhancement in a tube with equilateral triangle cross sectioned coiled wire inserts. experimental thermal and fluid science, 34, 684-691. 5000 10000 15000 20000 2500 0 50 100 150 200 reynolds number, re av era ge n us se lt nu mb er , n u air ( pr = 0.71) present prediction rashid sarkar et al. 132 experimental study of heat transfer enhancement through a tube with wire-coil inserts at low turbulent reynolds number 5. garcia, a., vicente, p. g., & viedma, a. (2005). experimental study of heat transfer enhancement with wire coil inserts in laminar-transition-turbulent regimes at different prandtl numbers. international journal of heat and mass transfer, 48, 4640–4651. 6. uttarwar, s. b., & rao, m. r. (1985). augmentation of laminar flow heat transfer in tubes by means of wire coil inserts. journal of heat transfer, 105, 930-935. 7. edwards, d. p., & jensen, m. k. (1994). pressure drop and heat transfer predictions of turbulent flow in longitudinal finned tubes. advances in enhanced heat transfer, asme htd, 287, 17-30. 8. mafiz, h., huq, a. m. a., & rahman, m. m. (1996). an experimental study of heat transfer in an internally finned tube. proceedings of asme heat transfer division, 2, 211-217. 9. islam, m. a., & mozumder, a. k. (2009). forced convection heat transfer performance of an internally finned tube. journal of mechanical engineering transaction, ieb, me 40(1), 54-62. 10. eiamsa-ard, s., wongcharee, k., eiamsa-ard, p., thiangpong, c. (2010). heat transfer enhancement in a tube using delta-winglet twisted tape inserts, applied thermal engineering, 30, 310-318. 11. date, a. w. (1974). prediction of fully-developed flow in a tube containing a twisted tape. international journal of heat and mass transfer. 17, 845-859. 12. hong, s. w., & bergles a. e. (1976). augmentation of laminar flow heat transfer in tubes by means twistedtape inserts. asme journal of heat transfer, 98, 251-56. 13. marner, w. j., & bergles a. e. (1978). augmentation of tube side laminar flow heat transfer in tubes by means twisted-tape inserts, static mixer inserts, and internally finned tubes. proceedings of 6th international heat transfer conference, hemisphere publishing, washington dc, 583-588. 14. van rooyen, r. s., & kroger d. g. (1978). laminar flow heat transfer in internally finned tubes with twistedtape-inserts. proceedings of 6th international heat transfer conference, toronto, canada. 15. plessis, j. p., & kroger, d. g. (1987). heat transfer correlation for thermally developing laminar flow in a smooth tube with a twisted-tape insert. international journal of heat and mass transfer, 30(3), 509-515. 16. gupte, n. s., & date, a. w. (1989). friction and heat transfer characteristics of helical turbulent air flow in annulis. journal of heat transfer, 111, 337-344. 17. manglik, r. m., & bergles, a. f. (1993). heat transfer and pressure drop correlations for twisted-tape inserts in isothermal tubes: part 1laminar flows. journal of heat transfer, 115, 881-889. 18. saha, s. k., & dutta, a. (2001). thermohydraulic study of laminar swirl flow through a circular tube fitted with twisted tapes. asme journal of heat transfer, 123, 417-425. 19. wang, s., guo, z. y., & li, z. x. (2000). heat transfer enhancement by using metallic filament insert in channel flow. international journal heat and mass transfer, 44, 1373-1378. 20. mergerlin, f. e., murphy, r. w., & bergles, a. e. (1974). augmentation of heat transfer in tubes by means of mesh and brush inserts. journal of heat transfer, 96, 145-151. 21. saha, s. k., & langille, p. (2002). heat transfer and pressure drop characteristics of laminar flow through a circular tube with longitudinal strip inserts under uniform wall heat flux, asme journal of heat transfer, 124, 421-430. 22. gee, d. l., & webb, r. l. (1980). forced convection heat transfer in helically rib-roughened tubes, international of journal of heat and mass transfer, 23, 1127-1136. 23. patankar, s. v., ivanovic, m., & sparrow, e. m. (1989). analysis of turbulent flow heat transfer in internally finned tube and annuli, journal heat transfer, 101, 29-37. 24. prakash, c., & patankar, s. v. (1981). combined free and forced convection in vertical tubes with radial internal fins, journal of heat transfer, 103, 566-672. 25. chowdhury, d., & patankar, s. v. (1985). analysis of developing laminar flow and heat transfer in tubes with radial internal fins, proc. asme national heat transfer conf., 57-63. 26. prakash, c., liu, y. d. (1985). analysis of laminar flow and heat transfer in the entrance region of an internally finned circular duct, journal of heat transfer, 107, 84-91. 27. sethumadhavan, r., rao, r. m. (1983). turbulent flow heat transfer and fluid friction in helical-wire-coilinserted tubes, international journal heat mass transfer, 26, 1833-1845. 28. vahidifar, s., & kahrom, m. (2015). experimental study of heat transfer enhancement in a heated tube caused by wire-coils and rings, journal of applied fluid mechanics, 8(4), 885-892. 29. garcia, a., solano, j. p., vicente, p. g., & viedma, a. (2007). enhancement of laminar and transitional flow heat transfer in tubes by means of wire coil inserts, international journal of heat and mass transfer, 50, 31763189. 30. sarkar, m. a. r., islam, m. z., & islam, m. a., (2005). heat transfer in turbulent flow through tube with wirecoil inserts. journal of enhanced heat transfer, 12(4), 385-394. 31. kline, s. j., & mcclintock, f. a. (1953). describing uncertainties in single-sample experiments, mechanical engineering, 3. 133 international journal of engineering materials and manufacture (2019) 4(2) 66-76 https://doi.org/10.26776/ijemm.04.02.2019.04 y. l. shuaib–babata 1 , h. k. ibrahim 2 , i. o. ambali 1 , r. a. yahya 1 , k.s. ajao 1 , n. i. aremu 1 , a. a pelumi 1 1 department of materials & metallurgical engineering 2 department of mechanical engineering university of ilorin, ilorin, nigeria e-mail: sylbabata@unilorin.edu.ng reference: shuaib–babata, y. l., ibrahim, h. k., ambali, i. o., yahya, r. a., ajao, k. s., aremu, n. i., pelumi, a. a. (2019). inhibitive potential of prosopis africana on corrosion of low carbon steel in 1m hydrochloric acid medium. international journal of engineering materials and manufacture, 4(2), 66-76. inhibitive potential of prosopis africana on corrosion of low carbon steel in 1m hydrochloric acid medium shuaib–babata yusuf lanre, ibrahim hassan kobe, ambali ibrahim owolabi, yahya raheem abolore, ajao kabiru suleiman, aremu ishaq na’allah and pelumi abibat atinuke received: 19 february 2019 accepted: 06 may 2019 published: 20 june 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract recently, there is quest for the use of inexpensive, non-toxic, non-biodegradable, readily available and environmentally acceptable corrosion inhibitor. studies have shown that these properties could be achieved through the use of plants as inhibitor. inhibiting effect of prosopis africana (iron tree) seed extracts were assessed on a sample of low carbon steel in 1m hcl with varying proportion of the seed extract using gravimetric, tafel polarization and gasometrical measurement techniques. the results show that weight loss/corrosion rate decreases with increase in the extracts’ concentrations. good inhibiting efficiency of prosopis africana extracts with optimum inhibiting efficiency of 97.7% at 1.0 g/l after 120 hours exposure in gravimetric measurement was attained. tafel polarization results revealed that the prosopis africana extract shows that the corrosion current density decreases with the increase in the concentration of the extract. the extract is found suitable as green inhibitor for corrosion of low carbon steel in the studied medium. keywords: mild steel, prosopis africana, weight loss, inhibiting efficiency, tafel polarization 1 introduction low carbon steel is a popular metal that has a wide range of applications due to its availability and excellent mechanical properties [1,2]. low carbon steel is much prone to corrosion when exposed to acidic or basic environment [3]. corrosion occurs in air, water, soil and in every environment and often affects most materials. other than materials loss, corrosion interferes with human safety, disrupts industrial operations and possesses danger to the environment [4]. corrosion is a natural process that cannot be totally prevented, but it can be minimized or controlled by proper selection of materials, design, coating and application of inhibitors [5]. for closed systems or sometimes even under flowing conditions, it is effective and convenient to employ corrosion inhibitors. corrosion inhibitors are used to protect metals by adsorption from corrosion attack. some of these inhibitors are synthetic in nature and therefore not eco-friendly because of the toxic product released to the environment after usage [6]. it has been established that most of the efficient inhibitors are organic compounds that contain in their structures mostly nitrogen, sulphur or oxygen atoms that create barrier to corrosion attack on the metal surface [7]. however, the toxicity of organic compounds combined with their cost and non-availability, have made natural products an excellent alternative possible corrosion inhibitors [8 10]. among the organic compounds, the majority of recent studies have been focused on plant extracts. the main constituents of the plant extracts have been reported to be a wide variety of organic compounds, including polyphenols, terpenes, carboxylic acids and alkaloids [11]. some of these plants include jathropha curcas, banana peel, curcuma extract, watermelon waste and moringa oleifera among others [1, 12-17]. prosopis africana is a perennial leguminous tree of the mimosoidae subfamily and is mostly grown in the savannah regions of west africa. in nigeria, this tree can be found between lat. 7° n and 10° n [18]. because this species is not cultivated, it is often referred to as wild, endangered but edible [19]; as a lost crop [20], or as a lesser crop. fruit setting, maturation, and dropping takes place in prosopis africana in nigeria between november and march. the trees produce many legume pods during the months of january and march. in nigeria, the seeds are very important inhibitive potential of prosopis africana on corrosion of low carbon steel in 1m hydrochloric acid medium 67 to the idoma, ighala, ebira, and tiv people (mostly of the guinea savanna) who use them to prepare a spice known as locust beans that is rich in protein and fatty acids [21]. when dried, the roots are used by the yorubas to make chewing sticks called “ayan”, which prevent dental root and gum decay in adults. the hardwood from prosopis africana offers good material for furniture, hoes, bows, pestles, mortars, and charcoal. the tree contributes to nutrient recycling and prevention of soil erosion [22]. prosopis africana seed is abundantly available in nigeria, most especially in the university of ilorin, where it is properly utilized and regarded as waste materials. utilization of the plant seed as corrosion inhibitor will curtail the possible environmental hazard that may arise as a result of its presence in the environment. the use of the plant as an inhibitor may be channelled to create wealth through job creation. however, the aim of this study is to investigate the corrosion potential of the prosopis africana seed extract (pase) and establish the possible efficiency it could offer as low carbon steel corrosion inhibitor in hydrochloric acid (hcl) medium. 2 methodology 2.1 sample preparation the elemental composition of the low carbon steel as shown in table 1 was determined at midwal engineering service limited, lagos using spectromaxx lmf06 spectrometer machine (serial number: 15007384).the sample was prepared in accordance with astm g1-03 & g4 guidelines [23, 24]. the metal sheet specimen was cut using guillotine machine into proper dimension of 2.2cm ×1.7cm× 0.15cm and drilled at the top to make hole (1mm) on the specimen for easy hanging, removal from tested solution and identification. emery papers of different grades (220, 320, 400,800, 1200) was use to grind the specimens (low carbon steel) to attain smooth and uniform surfaces. the specimens were then degreased with acetone, washed with distilled water and hot dried, and then immediately kept in desiccators. 2.2 preparation of the plant extract (inhibitor) prosopis africana seeds were removed from the pod and sun dried for 7 days, when it was fully dried. the dried seeds were crushed to remove the shell. the seed were then grinded into powder form and then soaked in ethanol for 48 hours, sieved using a sieve and filtered to remove the shaft. it was then left for more than 48 hours in a salt bath to allow ethanol to get evaporated. the samples of the prosopis africana (ponds, seeds and shell) are presented in figure 1. 2.3 preparation of test solution the hydrochloric acid, hcl (sp.gr.1.18) was prepared to obtain 1.0 molarity of hcl using the equation 1. the preparation was carried out in the corrosion laboratory at the department of materials and metallurgical engineering, university of ilorin, ilorin, nigeria. molarity = molecular weight of hcl specific gravity of hcl ×percentage of purity × m (1) table 1: chemical composition of low carbon steel sample [1] elements c si mn cr al cu ni p s co fe weight (%) 0.033 0.034 0.220 0.038 0.011 0.021 0.007 0.015 0.008 0.004 99.50 (a) (b) (c) figure 1: prosopis africana, (a) pond (b) shell after removing seeds from the pond (c) seeds shuaib–babata et al., (2019): international journal of engineering materials and manufacture, 4(2), 66-76 68 2.4 phytochemical analysis of the plant extract the phytochemical analysis of prosopis africana seed and pod were carried out at department of chemistry laboratory, university of ilorin, ilorin, nigeria to determine the presence of inhibitive functional groups. 2.5 gravimetric analysis a 140 ml of 1m hydrochloric acid was taken into a container from the prepared acidic solution. the corrosion test using weight loss measurements was carried out in accordance with the guidelines in astm standards [25]. the preweighed specimens from the desiccators were completely immersed in the 140 ml of 1m hcl solution with or without varying concentrations of prosopis africana extract covered from the atmosphere (figure 2). the concentrations of the inhibitor are presented in table 2. the test specimens were exposed to the medium between 24 hours and 2160 hours. this method was carried out in line with astm g1 standards [23]. the experimental set-up is shown in figure 2. sequel to removal of the specimens from the medium of exposure, chemical method of cleaning was employed to remove the corrosion products formed on the surface and edges of the specimens using a prepared solution in accordance with the astm g1 guidelines [23]. the solution containing 500ml of hcl, 3.5g hexamethylene tetramine and reagent water which makes 1000 ml solution. the coupons after corrosion test are shown in figure 3. the specimen was hot dried and then reweighed using electronic weighing balance (hx 302 with 0.01g accuracy) to determine the difference in weight (weight loss).the same procedure was repeated for the specimens exposed to the medium for the periods between 24 hours and 2160 hours. from the weight loss, the corrosion and the percentage inhibiting efficiency (ie %) of the plant extract were calculated using equations 2 and 3 respectively. corrosion rate (mpy) = 𝐤𝑾 𝑫𝑨𝑻 [23] or ∆𝐖 𝑨𝑻 (𝑔𝑐𝑚−2ℎ−1) [1,4,26] (2) where w is the mass loss (g), a is surface area of the specimen (steel coupon) in cm 2 , k is constant = 3.45 × 10 6 mils per year (mpy) [23], d is density of the steel (g/cm3) and t is the time of exposure (hours). i.e (%) = 𝐂𝐑𝐁𝐥𝐚𝐧𝐤− 𝐂𝐑𝐈𝐧𝐡 𝐂𝐑𝐁𝐥𝐚𝐧𝐤 × 𝟏𝟎𝟎 [26] (3) where crblank is corrosion rate in the absence of inhibitor, crinh is the corrosion rate in the presence of inhibitor. table 2: varying concentration of prosopis africana seed extract g/l 0.0 0.2 0.4 0.6 0.8 1.0 figure 2: gravimetric measurements set-up figure 3: cleaned specimen after corrosion test inhibitive potential of prosopis africana on corrosion of low carbon steel in 1m hydrochloric acid medium 69 2.6 tafel polarization techniques the steel sample was cut into 1.0 cm × 1.0 cm dimension. each of the specimens was held together with aluminium foil by connecting it with a flexible cable and placed on a cup mould. in another cup mould, hardener was added to a polyester resin and thoroughly mixed. to the mixture, an accelerator was added and mixed together to form a solution. the prepared solution was then poured in the initial mould where the specimens were placed, left for a period between 15-20 minutes to solidify. for surface exposure into the aggressive environments, the coupon was further polished. the electrochemical measurements were performed using a single compartment electrochemical cell design for varieties of flat samples for electrochemical test at room temperature. the cell consists of a three electrode system, saturated calomel electrode as the reference electrode, working electrode (low carbon steel) and graphite rod as the auxiliary/counter electrode (versastat) as electrochemical work station. for the data analysis, electrochem software was used. electrochemical measurement setup analysis and the specimens connectivity is shown in figure 4 and 5 respectively. 2.7 gasometric measurement gasometric measurement was carried out using the gasometric set-up described by awe et al. [7]. the assembly was setup as in figure 6 to measure the volume of evolved hydrogen gas from corroded mild steel in the test solution. this set-up consists of two necked conical flask (reaction flask) which contained test solutions and mild steel specimens, separating funnel, calibrated tube with retort stand, taps, and water bath. the measurement was carried out with different test solutions that contained in the reaction flask. and the reaction flask was connected to an inverted calibrated tube through a delivery tube. initial volume of water in the calibrated tube was recorded and mild steel specimens were carefully dropped in the test solution and quickly closed. the volume of evolved hydrogen gas from in reaction flask was monitored by the downward displacement of water. this displacement was monitored at 10 minutes interval, progressively for 100 minutes and the difference in the level of water was recorded as the volume of hydrogen gas. from obtained values of evolution hydrogen gas, the inhibition efficiency (ie %) was calculated using equation 4 [7]. ie % = 1 − crinh crabs (4) where crabs is the hydrogen evolution rate in absence of inhibitors and crinh is the hydrogen evolution rate in the presence of different concentration of inhibitors. figure 4: electrochemical measurement analysis setup figure 5: specimens held in foil and connected with cable for electrochemical measurement shuaib–babata et al., (2019): international journal of engineering materials and manufacture, 4(2), 66-76 70 figure 6: schematic diagram of the set-up used for gasometric measurements [5] table 3: qualitative and quantitative analyses of prosopis africana seed extract parameters (mg/100g) prosopis africana flavonoids 0.80 (+) tannin 4.10 (+) saponin 8.50 (++) steroids 2.20 (+) phenol 3.05 (+) table 4: phytochemical analysis of prosopis africana pod extract parameter (mg/100g) prosopis africana saponin 108.70 alkanoids 101.60 tannin 83.80 phenol 9.90 flavonoid 2.10 cardiac cilycosides 1.06 steroids 7.80 3 results and discussion 3.1 phytochemical analysis phytochemical compounds and herbal-based extracts have garnered increasing interest in the field of sustainable material protecting products [11]. the role of protection is to form a barrier of one or several molecular layers against corrosive media attack and this depends widely on the part of the plant and its geographical location [7]. from the results obtained in table 3 and 4, high presence of alkaloid (11.70 mg/l), alkaloid (10.60 mg/l) and saponin (108.70 mg/l) in prosopis africana seed extract is revealed. the presence of these compounds and their structures contribute to the inhibition efficiency due to the many functional groups that was found present in the compounds [7, 27]. the identified compounds as summarized in tables 3 and 4 were based on standard methods in literature [7, 27]. the presence of organic compounds such as tannins, alkaloids, steroids, amino acids, flavonoids, among others in some natural plant products has been found to be responsible for their inhibitory action [1,4, 28-33]. it was previously reported that bitter leaves extract contained many phytochemical compounds like tanins, saponins, alkaloids, and flavanoids and this make it more effective for inhibition of corrosion [27]. studies have also shown that formation of protective film on the metal surface due to adsorption of molecules of phytochemicals present in the plants on the surface of the metal is responsible for the inhibitive effect of some plants solution extract [33-35]. 3.2 gravimetric measurement (mass loss) the variation of mass loss recorded in low carbon steel at different concentrations of prosopis africana seed extract in 1m hcl at different time of immersion are shown in figure 7. generally, the mass loss of low carbon steel in hcl increased with increase in time of exposure, but decreases as the concentration of inhibitor increases. this implies that alkaloids 11.70 (++) inhibitive potential of prosopis africana on corrosion of low carbon steel in 1m hydrochloric acid medium 71 the rate of corrosion of the low carbon steel in hcl within the period of exposure would decrease as the concentration of the extract increased. though, the mass loss of the specimens with the presence of prosopis africana seed extract in 1m hcl reduced drastically (figure 8). in line with the views of lai et al. and shuaib-babata et al. [1, 36], the reduction in mass loss might be as a result of adsorption of the inhibitor on the metal surface. for instance, the mass loss in the medium after 168 hours of exposure with and without 1.0g/l of inhibitor was 0.02 g and 0.54 g respectively. this is an indication of effective potential inhibiting of prosopis africana at all concentrations. it is also in agreement with odusote et al. [4]s’ view that the mass loss of steel decreased as the concentration of the inhibitor increased. with 0.2g/l of inhibitor in the medium, mass loss of 0.13g after 168 hours of exposure was recorded, while at the same time 0.4g/l recorded 0.1g, 0.6g/l recorded 0.06g, 0.8g/l recorded 0.04g and 1.0g/l recorded 0.02g as shown in figure 8. these indicate that the weight loss increases with concentration of the inhibitor in line with the findings of loto et al. [37]. the results revealed formation of significant inhibitory properties of passive film on the surfaces and edges of the specimens, which could be traced to synergistic concentrations of phytochemical constituents of prosopis africana [1]. it is interested to note the specimens could not survive reaction in the media beyond 168 hours without the presence of prosopis africana (inhibitor) due to the aggressiveness of the environment, while other specimens in the medium with prosopis africana survived beyond 2160 hours. this is an indication of good inhibiting efficiency of prosopis africana. the specimens in the medium without prosopis africana after 168 hours of exposure is shown in figure 8a & b, while figures 8c show the nature of the specimen without inhibitor in the medium after corrosion test. figure 7: variation of mass loss with time for the corrosion of low carbon steel in 1m hcl with and without inhibitor. (a) (b) (c) figure 8: effectiveness of prosopis africana as an inhibitor in hcl medium. (a) nature of the low carbon steel immediately (b) the low carbon steel totally destructed after 168 hours after immersion without inhibitor of exposure in the medium without inhibitor due to aggressiveness of the evironment (c) nature of the low carbon steel without inhibitor in hcl after corrosion tests. shuaib–babata et al., (2019): international journal of engineering materials and manufacture, 4(2), 66-76 72 figure 9: the variation of corrosion rate in prosopis africana seed extracts figure 10: the percentage inhibition efficiency of prosopis africana seed extract at different concentrations the variation of corrosion rates within the time of exposure are presented in figure 9. it is shown in the results that the corrosion rate of low carbon steel in hcl with plant’s extract in the medium decreases with increase in time of exposure, while that of specimens in medium without plant extract decreases with increase in time of exposure. after 24 hours of exposure, the specimens in the medium with 0.0 g/l recorded corrosion rate of 461.72 mpy, while 152.18 mpy was recorded after 168 hours at the same medium. more so in hcl with plants extract, the specimen’s corrosion rate decreases with increase in concentration of the extract. considering the corrosion rate results after 24 hours of exposure, the specimen exposed in 1m hcl with the 0.2 g/l concentration of prosopis africana seed extract recorded 63.92 mpy, while specimen in the medium with 1.0 g/l recorded 10.65 mpy for the same period. again, in medium with 0.2 g/l and 1.0 g/l inhibitor after 72 hours of exposure, the recorded corrosion rate was 78.12 mpy and 10.65 mpy respectively. in medium with 0.2 g/l and 1.0 g/l inhibitor after 168 hours of exposure, corrosion rate was also 39.57 mpy and 6.09 mpy respectively. as a result of this, it is assumed that there is increase in adsorption of the constituents of the extract on the surface of the low carbon steel as the concentration of prosopis africana seed extract increases, which led to reduction in corrosion in the medium [1, 38, 39]. figure 10 shows the variation of prosopis africana seed extract inhibiting efficiency within the period of immersion in 1m hcl solution. the results indicate that the prosopis africana seed extract inhibiting efficiency increases with its increasing concentration, but it was not consistent with the time of exposure. it is as a result of formation of a protective film which results to transition of metal interface from an active dissolution state to a passive state. the optimum inhibiting efficiency of 97.7% was recorded with concentration of 1.0 g/l after 120 hours of exposure. from the results (figure 10), the steadiness inhibitive behaviour of prosopis africana seed extract was revealed through the calculated percentage inhibition efficiency. the ie% ranged between 74.0 and 97.7% within 24 to 168 hours of exposure. the percentage inhibition efficiency of prosopis africana seed extract in hcl medium beyond 168 hours of exposure could not be calculated since the specimens in hcl without prosopis africana seed extract could not withstand the aggressiveness of the medium as shown in figure 8. though, the specimens in hcl medium with prosopis africana seed extract were intact (figures 3 & 4) even after 2160 hours of exposure. this proved the effectiveness of prosopis africana seed extract as an inhibitor of low carbon steel in hcl medium beyond 2160 hours. the effectiveness may be attributed to transition of metal interface from an active dissolution state to a passive state which resulted to the formation of protective film on the surfaces and edges of the specimens. inhibitive potential of prosopis africana on corrosion of low carbon steel in 1m hydrochloric acid medium 73 3.3 tafel polarization technique corrosion rate is being measured with tafel extrapolation. tafel behaviour (polarization curves) exhibits linear behaviour in the corrosion potential (ecorr) against log corrosion current density (icorr) plots for an electrochemical reaction under activation control. starting from a cathodic potential of -200mv/s to an anodic potential of +250mv/s at a cam rate of 0.166, polarization measurements were carried out. the linear tafel segment of the cathodic curves and the calculated anodic tafel lines were extrapolated to corrosion potential to obtain the corrosion current densities icorr [40]. figure 11 shows that as the concentration of prosopis africana seed extract increased, the corrosion potential shifts toward a more noble direction. furthermore, in the presence of prosopis africana seed extract, the corrosion current decreases markedly and the magnitude of such an effect increases with increasing prosopis africana seed extract concentration. the inhibitive action of the extract to corrosion of low carbon steel in the 1m hcl is reflected in the results (figure 11). the inhibition efficiency increases with increasing extract concentration. the effect of the extract on both anodic and cathodic reactions is also reflected in the results (figure 11). prosopis africana seed extract therefore acts as a mixed inhibitor. 3.4 gasometric analysis figure 12 shows the variation in volume of hydrogen gas evolved in 1m hcl at different concentration of the extract. it was revealed that the volume of hydrogen gas evolved increases with time until a level was reached when it remains constant. this constant level was reached quicker in the solutions containing inhibitors than that without inhibitor. this may be as a result of quicker formation of passive layer on the surface of the metal in the solution containing inhibitors. thus, the higher the inhibitor concentration in a solution, the quicker the passivity level would be reached. figure 11: corrosion potential against corrosion current density (prosopis africana seed extract) figure 12: rate of evolution of hydrogen gas in 1m hcl at different concentration of the extract. shuaib–babata et al., (2019): international journal of engineering materials and manufacture, 4(2), 66-76 74 figure 13: variation of inhibition efficiency with time of exposure. figure 13 shows the results obtained by the variation of percentage inhibition efficiency with the time of exposure. the results show same initial 20 minutes of zero inhibition at all inhibitor concentration. this might be the period for formation of passive layer in the solution. the corrosion rate was high at the initial point with no inhibitive action from the extract irrespective of the concentration until adsorption of the inhibitor on the metal surface began. it is revealed in the results (figure 13) that total inhibition of corrosion of the low carbon steel in 1m hcl solution was initially experienced (100% at 30 minutes) and later decreased to a level where it started increasing as the time of exposure increases. the initial behaviour might be as a result of slow adherence of the acid to the metal surface which in turn slowed down the attack of the metal by the acid. the point of initiation of the decrease in inhibition level may be as a result of the absorption of the extract on the steel surface before corrosion retardation occurred. the increase in the inhibition with the concentration of the extract is probably due to the retardation of the corrosion rate by the inhibitor as suggested by odusote et al. [4] for the inhibition of mild steel corrosion by moringa oleifera leave extract. conclusions according to the assessment of inhibition of corrosion of the low carbon steel in an acidic solution (hcl) by the use of prosopis africana seed extract using gravimetric, electrochemical measurement (tafel polarization techniques) and gasometric analysis. the following conclusions are drawn from this study: 1. the inhibition of the corrosion of the low carbon steel in the acidic solution by prosopis africana seed extracts is due to the phytochemical constituents of the plant extract 2. the corrosion rate of the low carbon steel in the acidic solution (hcl) solution decreases with increase in the concentration of prosopis africana seed extract 3. the optimum percentage inhibition efficiency of prosopis africana (97.7%) was attained with 1.0 g/l concentration of the extract after 120 hours of exposure 4. in gravimetric technique, the prosopis africana seed extract’s inhibition efficiency depends on its concentration. the efficiency decreases with increase in the extract’s concentration in the medium. 5. tafel polarization technique result showed that the extract acted as a missed type inhibitor via a simple absorption of the phytochemicals present in the extract on the low carbon steel surface in hcl. 6. gasometric technique revealed quicker formation of passive layer on the surface of the metal in the solution containing prosopis africana seed extract (inhibitors). thus, the higher the inhibitor concentration in a solution, the quicker the passivity level would be reached. 7. the prosopis africana seed extract was found to be an effective inhibitor of corrosion of low carbon steel in hcl solution. references 1. shuaib babata, y. l., busari, y.o., yahya, r. a. & abdul, j. m. (2018). corrosion inhibition of aisi 1007 steel in hydrochloric acid using cucumis sativus (cucumber) extracts as green inhibitor, acta technica corviniensis – bulletin of engineering, xi(4):153-161 2. shuaib-babata, y. l. (2006). effect of heat treatment on corrosivity of commercial mild steel in sulphuric acid, journal of environmental monitor, 1(1): 73-82 inhibitive potential of prosopis africana on corrosion of low carbon steel in 1m hydrochloric acid medium 75 3. abdulraman a. s., kareem a. ganiyu, ibrahim h. kobe, awe i. caroline (2015). the corrosion inhibition of mild steel in sulphuric acid solution by adsorption of african perquetina leaves extract. international journal of innovative research in science engineering and technology. 4(4): 1809-1921 4. odusote. k.o. & ajayi, o. m. (2016). inhibition efficiency of moringa oleifera leaf extract on the corrosion of reinforced steel bar in hcl solution. the west indian journal of engineering , 38(2): 64-70. 5. abdulraman a. s., ibrahim h. kobe, v. s. aigbondion, kareem a. ganiyu, awe i. caroline (2014). thermodynamic behaviour of mild steel corrosion in an enviroment of bilberry cactus plant extracts in hydrochloric acid solution, journal of metallurgy and materials engineering, 9:1-14. 6. odusote. k.o. & ajayi, o. m (2013). corrosion inhibition of mild steel in acidic medium by jathropha curcas leaves extract. journal of electrochemical science and technology, 4(2):81-87. 7. awe i. caroline abdulraman a. s., ibrahim h. kobe, kareem a. ganiyu, (2015). inhibitive performance of bitter leaf root extract on mild steel corrosion in sulphuric acid solution, american journal of material engineering and technology, 3(2):35-45 8. el ibrahimi, b., jmiai, a., bazzi, l., el issami, s. (2017). amino acids and their derivatives as corrosion inhibitors for metals and alloys, arabian journal of chemistry, in press. 9. salhi, a., bouyanzer1, a., chetouani, a., el ouariachi, e., zarrouk, a., hammouti, b., desjobert, j.m. and costa, j. (2017). chemical composition, antioxidant and anticorrosion activities of mentha suaveolens, journal of materials and environmental sciences, jmes, 8 (5): 1718-1728. 10. allam, l., oulmas, c.,boughrara, d. kadri, a. benbrahim, n. ( 2017). eugenia caryophyllata extract as green inhibitor for steel corrosion in 1m hcl solution, journal of materials, processes and environment .5 (1):18. 11. xhanari, k., finˇsgar, m., knez hrnˇciˇc, m., maver, u, knez, z. and seiti, b. (2017). green corrosion inhibitors for aluminium and its alloys: a review, rsc adv., 7(2017): 27299 –27330. 12. omotosho, o. a. ajayi, o.o. fayomi, o. s. ifepe, v. o. (2011). assessing the deterioration behaviour of mild steel in 2m h2so4 using bambusa glauscescens. international journal of applied engineering research, dindiguc, 2(2): 406-418. 13. devarayan, k. mayakrishnan, g. and nagarajan, s. (2012). green inhibitors for corrosion of metals: a review, chemical science review and letters, 1(1): 1-8 14. ajayi, o. m., odusote, j. k. & yahya, r. a. (2014). inhibition of mild steel corrosion using jatropha curcas leaf extract, j. electrochem. sci. eng., 4(2): 67-74 15. olusegun sunday j., adeiza barnabas a, ikeke k. i. and bodunrin m.o. (2013). jatropha curcas leaves extract as corrosion inhibitor for mild steel in 1m hydrochloric acid, j. emerg. trends eng. appl. sci., 4(1): 138 – 143. 16. kairi, n. i. & kassim.j. (2013). the effect of temperature on the corrosion inhibition of mild steel in 1 m hcl solution . international journal of electrochemical science , 8(2013):7138 7155. 17. odewunmi, n. a., umoren, s. a. & gasem, z. m. (2015). utilization of watermelon rind extract as a green corrosion inhibitor for mild steel in acidic media, journal of industrial and engineering chemistry, 21(2015):239247. 8. agboola, d. a. (2004). 'prosopis africana (mimosaceae) stem, roots, and seeds in the economy of the savanna areas of nigeria. economic botany 58(supplement):s34-s42. 19. ola-adams, b. a., and h. d. onyeabusim. 1993. conservation and utilization of endangered edible wild plants in nigeria. proceedings of the seminar on lost crops of nigeria. university of agriculture, abeokuta, nigeria, 3343. 20. okafor, j. c. 1993. lost crops of nigeria. proceedings of the seminar on lost crops of nigeria. university of agriculture, abeokuta, nigeria, 221. 21. sanni, a., e. lie, and a. m. lindberg. (1993). fatty acid composition of prosopis africana and its fermented products 'okpehe'. food chemistry microbiology technology, 15:89-90. 22. alabi, d. a. (1993). parkia biglobosa: an endangered species. proceedings of the seminar on lost crops of nigeria. university of agriculture, abeokuta, nigeria. 23. astm g1. (1999).standard practice for preparing, cleaning, and evaluation corrosion test specimens, 14-21. 24. astm g4. (1995).standard guide for conducting corrosion coupon test in field application, 44-53. 25. astm nace/astm g3112a (2012): standard guide for laboratory immersion corrosion testing of metals, astm international, 100 barr harbor drive, west conshohocken, pa 19428-2959, united states. 26. adewuyi, b.o. and talabi, h. k. (2017). inhibiting efficiency of locally developed inhibitors (amaranthusspinosus, euphorbia heterophylla, imperatacylindrica and panicum maximum) on low carbon steel in acidic and saline media, international journal of engineering, tome xv (fascicule 2): 69-76. 27. debi, g. e., esah, h., mohammad, i., asipita, s. a.,5aminu, m. ( 2013). effect of vernonia amygdalina extract on corrosion inhibition of mild steel in simulated seawater, australian journal of basic and applied sciences, 7(14), 257-263 28. martinez, s. (2002). inhibitory mechanism of mimosa tannin using molecular modelling and substitutional adsorption isotherms. materials chemistry and physics, 77(1):97-102 29. chowdhary, r., jain, t., rathoria, m. k. and mathur, s. p. (2004). corrosion inhibition of mild steel by acid extracts of prosopis juliflora, bulletin of electrochemistry, 20(2):67-75 shuaib–babata et al., (2019): international journal of engineering materials and manufacture, 4(2), 66-76 76 30. amitha rani, b. e. and basu, b. b. j. (2012,). green inhibitors for corrosion protection ofmetals and alloys: an overview, international journal of corrosion, 2012: 1-15 31. nnabuk, o. e., stevens, a. o. and ibiam, n. a. (2010) ethanol extract of ocimum gratissimum as a green corrosion inhibitor for the corrosion of mild steel in h2so4, green chemistry letters and reviews, 3(3):165172. 32. zakvi, s. j. and mehta, g. n. (1988) acid corrosion of mild steel and its inhibition by swertia aungustifoliastudy by electrochemical techniques, transactions of the saest, 23(4):407–410. 33. verma, s. and mehta, g. n. (1999).effect of acid extracts of acacia arabica on acid corrosion of mild steel, bulletin of electrochemistry, 15(2):67–70. 34. oguzie, e.e. and ebenso, e. e. (2006). studies on the corrosion inhibiting effect of congo red dye – halide mixtures, pigment & resin tech. 35(1):30–35. 35. el-etre a. y. and el-tantawy, z. (2006). inhibition of metallic corrosion using ficus extract. portugaliae electrochimica acta, 24:347–356. 36. lai, c., xie, b., zou, l, zheng, x., mab, x., zhu, s. (2017). adsorption and corrosion inhibition of mild steel in hydrochloric acid solution by s-allyl-o,o0-dialkyldithiophosphates, results in physics, 7: 3434–3443. 37. loto, c. a., loto, r. t. and joseph, o. o. (2017). effect of benzamide on the corrosion inhibition of mild steel in h2so4, south african journal of chemistry, 70(2017): 38-43. 38. nnanna, l. a. & owate, i. o. (2014). an interesting and efficient green corrosion inhibitor for aluminium from extracts of moringa oleifera in acidic solution. scientia africana , 13(1):52-63. 39. okoronkwo, a. e., olusegun, s. j. and oluwasina, o. o. (2015). the inhibitive action of chitosan extracted from archachatina marginata shells on the corrosion of plain carbon steel in acid media, anti-corrosion methods and materials, 62(1): 13-18. 40. amin, m.a., a. e.-f. ((2009). electrochemical frequency modulation and inductively coupled plasma atomic emmission spectroscopy methods for monitoring corrosion rates and inhibition of alloy steel corrosion in hcl solution and a test for validity of the tafel extrapolation. corrosion science , 51(2009):882-894. international journal of engineering materials and manufacture (2018) 3(2) 68-77 https://doi.org/10.26776/ijemm.03.02.2018.01 a. maged 1,a , s. haridy 1,2,b , m. shamsuzzaman 2,c , i. alsyouf 2,d and roubi zaied 1,3,e 1 benha faculty of engineering, benha university, benha 13512, egypt 2 department of industrial engineering and engineering management university of sharjah, po box 27272, sharjah, united arab emirates 3 department of industrial engineering, northern border university, arar 7322, saudi arabia a e-mail: ahmed.maged@bhit.bu.edu.eg, b e-mail: sharidy@sharjah.ac.ae, c e-mail: mshamsuzzaman@sharjah.ac.ae d e-mail: ialsyouf@sharjah.ac.ae, e e-mail: rouby.nasr@bhit.bu.edu.eg reference: maged et al. (2018). statistical monitoring and optimization of electrochemical machining using shewhart charts and response surface methodology. international journal of engineering materials and manufacture, 3(2), 68-77. statistical monitoring and optimization of electrochemical machining using shewhart charts and response surface methodology ahmed maged, salah haridy, mohammad shamsuzzaman, imad alsyouf and roubi zaied received: 17 april 2018 accepted: 10 may 2018 published: 30 june 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract the response surface methodology (rsm) and shewhart control charts have been widely used in manufacturing to reduce variation, improve quality and optimize the output. this article proposes an application of individuals & moving range chart (i&mr) and rsm in electrochemical machining. the shewhart-type i&mr control chart and rsm are combined together in an effective way to successfully guarantee the statistical control of the surface roughness (ra) of the items produced by wire electrochemical turning, and meanwhile optimize ra by exploring the optimal values of the machining parameters including applied voltage, wire feed rate, wire diameter, rotational speed and overlap distance. the conducted experiments reveal that the optimal values of the aforementioned factors are 23.67, 0.5, 0.2, 900 and 0.02, respectively. a second-order regression model is also developed to predict the output (ra) at different combinations of the input parameters. the developed regression model can predict the output values with a determination coefficient (r 2 ) of 96.9%. the proposed combined scheme of shewhart charts and rsm can be employed in other manufacturing processes and even in different service sectors to efficiently enhance the performance and reduce the cost. keywords: electrochemical machining, surface roughness, control chart, response surface methodology, regression model, analysis of variance 1 introduction distinct from conventional machining processes, non-traditional machining processes are capable of machining the highly alloyed materials irrespective their mechanical properties. consequently, maximizing the need for the utilization of suitable techniques of non-traditional machining processes on different existing and newly developed materials (e.g. metals, non-metals, and composites, etc.) (debnath, kunar, anasane, & bhattacharyya, 2017). electrochemical machining (ecm) is a non-traditional machining technique to shape metals by controlled anodic dissolution at extremely high current densities. the process evades mechanical stress applied to tool and workpiece, as well as it yields shiny surfaces without further finishing processes. material hardness does not affect the process in any way. on the other hand, it can be used to achieve complex surfaces by changing the shape of the tool (breitkopf & swider-lyons, 2016). ecm process can be more economical if a conductive wire is used as a tool since it helps to prevent tool profiling. using wire-tool allows cutting complex shapes with no need for large amount of power supplies (qu, ji, & zeng, 2014). using wire-tool in ecm is known as wire electrochemical machining (wecm). however, there are some difficulties while using in achieving the optimal parameters of machining process such as voltage applied (v), feed rate (f) and the diameter of the wire (d). the optimal machining parameters can enhance the key process characteristics such as the metal surface roughness (ra) and metal removal rate (mrr). many articles have discussed the wecm (kim, na, lee, choi, & chu, 2005; qu et al., 2014; shin, kim, & chu, 2008; wang, zeng, liu, & zhu, 2012; yamaguchi & natsu, 2017). hofstede and van den brekel (1970) suggested using a wire tool in electrochemical turning (ect), which was later defined as wire electrochemical turning (wect). el-taweel and haridy (2014) experimentally determined the key factors affecting metal removal rate (mrr) and investigated an efficient prediction model to maximize mrr in the wect process. maged et al., (2018): international journal of engineering materials and manufacture, 3(2), 68-77 69 control chart (originally developed by walter shewhart in late 1920s) has played a key role in monitoring products’ quality. the idea behind the developing of shewhart control chart is that repeated measurements from a process will exhibit variation. in a stable process, the variation can be easily predicted and can be approximated by one of several statistical distributions. the sole purpose of control chart is to keep the process near the target value and within boundaries of natural variations (benneyan, lloyd, & plsek, 2003). on the other hand, response surface methodology (rsm) is a structured methodology of design of experiments (doe) for systematically applying statistics to experimentations allowing the user to find relationships between the different input factors affecting the outputs. rsm typically involves setting up a combination of experiments, in which all relevant factors are varied systematically. these experiments are then analysed, allowing the user to find optimal parameters and the main factors affecting the results as well as identifying the interactions and synergies between factors if existed. it can be adopted whenever a phenomenon is to be investigated whether to gain more understanding or to achieve a better performance regardless of their background (maged, haridy, kaytbay, & bhuiyan, in press). this study presents a combined scheme of rsm and shewhart charts to obtain an adequate experimental procedure for investigating a reliable prediction model that relates input and output parameters of the wect. the output parameter of interest in this case experiment is surface roughness. rsm is used to design and analyze all experiments. the output parameters are tested for statistical control using individuals and moving range chart (i&mr) control chart which is a shewhart-type control chart. in addition, an optimization analysis is performed to locate the optimal values of the input parameters, accordingly minimizing the surface roughness. minitab 17 is used for the statistical analysis held in this article. 2 shewhart control charts statistical process control (spc) techniques are adopted to monitor a process over time to detect variations in the performance (woodall & montgomery, 1999). spc methodologies include the employment of shewhart control charts to detect assignable causes so that the corresponding root causes may be permanently removed. control chart is the most commonly used tool in spc (oakland, 2007). the shewhart control chart is one of the most popular statistical tools for monitoring a quality characteristic of interest. the popularity of the shewhart control chart stems from its effectiveness and simplicity (haridy, maged, kaytbay, & araby, 2017; saleh, mahmoud, keefe, & woodall, 2015; shamsuzzaman, haridy, alsyouf, & rahim, 2018). in some situations, the sample size used for process control is n = 1; that is, the sample consists of an individual unit (skinner, montgomery, & runger, 2003). for examples, in occasions where automated inspection and measurement technology is used, and every single unit manufactured is inspected. in addition, where the production rate is very slow, a sample size of n > 1 is not allowable. as well as, in situations where repeated measurements of a process differ only due to laboratory or inspection error, as in many chemical processes. in such situations, the i&mr control chart is adequate. it uses the moving range of two successive observations to estimate the process variability. the moving range is defined as i i-1 x x i mr  an estimate of  is: 128.1 2 ^ mr d mr  (1) because d2 = 1.128 when two consecutive observations are used to calculate a moving range. the center line, and upper and lower control limits for a control chart for individuals are given by 128.1 33 2 mr x d mr xucl  , xcl  , 128.1 33 2 mr x d mr xlcl  (2) 3 response surface methodology response surface methodology (rsm) is considered as a common tool in experimental data analytics. it is used when the influence of several input factors on a response variable are to be investigated by approximating complex functional relationships by “simple” linear or quadratic multivariate polynomial regression models, which are usually denoted as first or second order response surface models (anderson-cook, borror, & montgomery, 2009; myers, montgomery, & anderson-cook, 2009). the vast applications of rsm are in situations where several input variables potentially affect some performance measure or quality characteristic of the process, that is called as response. munda and bhattacharyya (2008) proposed a general second order polynomial response surface model to evaluate the parametric influences on the various machining criteria as follows 𝑌𝑢 = 𝑏𝑜 + ∑ 𝑏𝑖𝑋𝑖𝑢 𝑛 𝑖=1 + ∑ 𝑏𝑖𝑖𝑋𝑖𝑢 2𝑛 𝑖=1 + ∑ 𝑏𝑖𝑗𝑋𝑖𝑢 𝑛 𝑗>𝑖 𝑋𝑗𝑢 + 𝜀 (3) where yu is the corresponding response, xiu (1, 2… n) are the coded levels of the n controlling machining parameters pertaining to yu, and ε is the experimental error. the terms bi, bii, and bij are the first and second-order regression coefficients. the second term of this polynomial equation is attributable to linear effect, whereas the third term corresponds to the higher-order effects, and the fourth term of the equation includes the interactive effects of the process parameters. applying the least square technique, the values of these coefficients can be estimated by using statistical monitoring and optimization of electrochemical machining using shewhart charts and response surface methodology 70 the collected (y1, y2,…yk) through the k design points (munda & bhattacharyya, 2008). mukhopadhyay and khuri (2008) optimized response surface designs for multivariate generalized linear models. anderson-cook et al. (2009) discussed graphical methods used to evaluate design performance and their application on different rsm problems emphasizing how to use it to choose between competing designs. ahmad and gilmour (2010) investigated design of experiments in case of missing observations and also, the robustness of subset designs was improved for multiple levels applying the minimax loss criterion. khuri and mukhopadhyay (2010) studied the various milestones in the development of response surface methodology. drovandi et al. (2017) introduced a principled design of experiments approach to analyse big data. many researchers usually use rsm as an optimization method. campatelli, lorenzini, and scippa (2014) minimized the power consumption in milling process of carbon steel. sarıkaya and güllü (2014) analyzed and optimized the machining parameters of cnc turning process using taguchi design and rsm. thirugnanasambandham, sivakumar, and maran (2015) used rsm to optimize electrochemical treatment in food industry. asiltürk, neşeli, and i̇nce (2016) investigated the parameters affecting the surface roughness of medical material produced by cnc lathe machine using rsm and found that the radius of the machining tool tip is a key factor for optimizing it. diel et al. (2016) increased the efficiency of energy usage in pulp and paper industry using rsm. 4 experimental setup all the required experiments are conducted on wect test rig. the wet consists of three main parts, the mechanical components (e.g. gears, bolts, etc.), the electrical power driving system (e.g. motors) and the electrolyte flow control system. the test rig has three axes in order to achieve the motion in the x, y, and z-axes. the wire movement occurs in x-axis direction parallel to the centre axis of the workpiece, while the workpiece rotates around the same axis. the x-axis screw is rotated by a stepper motor. a worm gear is used to reduce the rotational speed of the stepper motor. the stepper motor speed is controlled by the number of pulses from the microcontroller. for instance, the stepper motor of 1.8 o step will undergo a rotation of 1.8 o for each pulse received. so, a revolution of 360 o is performed by 200 pulses. the stepper motor speed and rotation direction controls the tool feed rate. the workpiece is held inside a box by a rotatable chuck at one end, and by a centering tool at the other end. the workpiece rotating motion is controlled by a dc motor. the tool (i.e. wire) is fixed in a copper holder to resist corrosion. the wire is fixed by the nozzle and a tightening screw as indicated in figure 1, allowing the electrolyte to flow and penetrate around it. just before starting the wect process, the initial position of the wire and workpiece is shown in figure 2. 4.1 conditions and measurements of experiments a primitive wect experimental set was successfully prepared to analyze the effect of the main machining input parameters on the machining performance characteristics of interest. input parameters include applied voltage (v), wire feed rate (f), wire diameter (d), rotational speed (n) and overlap distance (h). on the other hand, the machining performance characteristic is the surface roughness (ra). the experimental settings of wect process parameters are depicted in table 1. these conditions are chosen based on prior experiments and literature surveys (da silva neto, da silva, & da silva, 2006; el-taweel & haridy, 2014; hofstede & van den brekel, 1970). ra for each specimen was measured by a surface roughness tester. the final values shown in table 3 are obtained by averaging four measurements. figure 1: tool holder model maged et al., (2018): international journal of engineering materials and manufacture, 3(2), 68-77 71 (a) (b) figure 2: various positions of wire and workpiece in wecm. (a) initial position of workpiece and wire and (b) machining of the workpiece. table 1: wect working conditions working conditions description workpiece material mild steel tool material brass applied voltage , v 10-40 v feed rate, f 0.1 – 0.5mm/min wire diameter, d 0.2 -2 mm rotational speed, n 300 – 900 rpm overlap distance, h 0.020.06 mm electrolyte type nacl electrolyte concentration 250 g/l electrolyte flow rate 15 l/min initial frontal gap 1mm nozzle diameter 6 mm machining distance 11mm 5 implementation and discussions the implementation of the combined scheme of rsm and shewhart charts is briefed below: 1. the values of the input parameters are defined using rsm. 2. the experiments are held using the generated values and their corresponding outputs are obtained. 3. shewhart control chart is used to assess the process control on the output parameters. 4. experiments are considered reliable for investigating a prediction model and optimality search, if the output parameters are in statistical control. 5. experiments are considered invalid if the output parameters are not in statistical control. assignable causes, which led to the non-statistical control or change the range of the input parameters, should be eliminated and a new set of input values has to be generated. 5.1 generating input and output parameters experimental runs are conducted on the test rig and responses are obtained. the input parameters of the real and coded values are listed in table 2. the design matrix used to hold the experiments and the corresponding output ra are illustrated in table 3. statistical monitoring and optimization of electrochemical machining using shewhart charts and response surface methodology 72 table 2: doe factors levels in wect input parameter levels -2 -1 0 +1 +2 applied voltage (v) , v 10 17.5 25 32.5 40 longitudinal feed rate (f) , mm/min 0.1 0.2 0.3 0.4 0.5 wire diameter (d), mm 0.2 0.65 1.1 1.55 2 overlap distance (h), mm 0.02 0.03 0.04 0.05 0.06 rotational speed (n), rpm 300 450 600 750 900 5.2 individuals control chart individual moving range (i&mr) control chart (shown in figure 3) is constructed to determine whether the surface roughness (ra) is in statistical control or not. it can be seen that all points are in statistical control; consequently the data can be used to build up a regression model. figure 3: i&mr chart for ra 5.3 investigating the prediction models prediction model is a mathematical model links the responses and the machining parameters. using the relevant data listed in table 3, the mathematical models of the real values of ra can be formulated as follows: 2 2 2 2 ( 5) ( 3) 11.57 0.1743 5.64 2.413 175.6 0.00707 0.000457 1.94 0.096 194 0.1492 0.00722 3.725 2.9 10 0.681 85.6 10.69 2.25 10 0.1212 a r v f d h n v f d h vf vd vh vn fd fh dh dn hn                        (4) the model is checked for adequacy by analysis of variance (anova) as in table 4 and a graphical presentation of predicted versus the experimental values is shown in figure 4. it can be seen that the predicted values are quite close to the real ones. the model is now considered reliable for further predictions as long as they are within the specified range. 3128252219161310741 3 2 1 0 observation in d iv id u a l v a lu e _ x=1.595 ucl=2.948 lcl=0.242 3128252219161310741 1.6 1.2 0.8 0.4 0.0 observation m o v in g r a n g e __ mr=0.509 ucl=1.662 lcl=0 i-mr chart of c1 maged et al., (2018): international journal of engineering materials and manufacture, 3(2), 68-77 73 5.4 main effect plot this plot (figure 5) helps in distinguishing the significant factors from insignificant ones. where there is an observable difference between the values of response at the high and low levels of a factor, this factor is contemplated as significant (v, f, d, h and n). it also demonstrates which level is to be maintained for the significant factors to minimize ra. it can be seen that holding all the factors at high level will decrease the ra. figure 4: predicted vs. real response values of ra surface roughness figure 5: main effect plot for ra surface roughness 2.52.01.51.0 2.5 2.0 1.5 1.0 predicted r e s p o n s e 500-50 30 20 10 0 -10 0.50.0-0.5 20-2 0.10.0-0.1 10000-1000 v m e a n o f r e s p o n s e f d h n main effects plot for response fitted means r2 = 96.9% statistical monitoring and optimization of electrochemical machining using shewhart charts and response surface methodology 74 table 3: matrix of input variables and corresponding responses exp. no. input parameters applied voltage feed rate wire diameter overlap distance rotational speed surface roughness ra (µm) coded x1 real v coded x2 real mm/min coded x3 real mm coded x4 real mm coded x5 real rpm 1 -1 17.5 -1 0.2 -1 0.65 -1 0.03 1 750 1.53 2 1 32.5 -1 0.2 -1 0.65 -1 0.03 -1 450 1.95 3 -1 17.5 1 0.4 -1 0.65 -1 0.03 -1 450 2.2 4 1 32.5 1 0.4 -1 0.65 -1 0.03 1 750 1.2 5 -1 17.5 -1 0.2 1 1.55 -1 0.03 -1 450 1.6 6 1 32.5 -1 0.2 1 1.55 -1 0.03 1 750 0.9 7 -1 17.5 1 0.4 1 1.55 -1 0.03 1 750 1 8 1 32.5 1 0.4 1 1.55 -1 0.03 -1 450 1.4 9 -1 17.5 -1 0.2 -1 0.65 1 0.05 -1 450 1.56 10 1 32.5 -1 0.2 -1 0.65 1 0.05 1 750 2 11 -1 17.5 1 0.4 -1 0.65 1 0.05 1 750 1.3 12 1 32.5 1 0.4 -1 0.65 1 0.05 -1 450 2.6 13 -1 17.5 -1 0.2 1 1.55 1 0.05 1 750 1.2 14 1 32.5 -1 0.2 1 1.55 1 0.05 -1 450 1.5 15 -1 17.5 1 0.4 1 1.55 1 0.05 -1 450 1 16 1 32.5 1 0.4 1 1.55 1 0.05 1 750 2.55 17 -2 10 0 0.3 0 1.1 0 0.04 0 600 1.2 18 2 40 0 0.3 0 1.1 0 0.04 0 600 1.85 19 0 25 -2 0.1 0 1.1 0 0.04 0 600 1.4 20 0 25 2 0.5 0 1.1 0 0.04 0 600 1.7 21 0 25 0 0.3 -2 0.2 0 0.04 0 600 2 22 0 25 0 0.3 2 2 0 0.04 0 600 1.1 23 0 25 0 0.3 0 1.1 -2 0.02 0 600 1.3 24 0 25 0 0.3 0 1.1 2 0.06 0 600 1.8 25 0 25 0 0.3 0 1.1 0 0.04 -2 300 1.8 26 0 25 0 0.3 0 1.1 0 0.04 2 900 1.2 27 0 25 0 0.3 0 1.1 0 0.04 0 600 1.4 28 0 25 0 0.3 0 1.1 0 0.04 0 600 1.8 29 0 25 0 0.3 0 1.1 0 0.04 0 600 1.8 30 0 25 0 0.3 0 1.1 0 0.04 0 600 1.7 31 0 25 0 0.3 0 1.1 0 0.04 0 600 1.8 32 0 25 0 0.3 0 1.1 0 0.04 0 600 1.7 maged et al., (2018): international journal of engineering materials and manufacture, 3(2), 68-77 75 table 4: anova analysis in wect process source df ss ms fvalue p-value model 20 5.24398 0.2622 17.04 0 linear 5 1.01147 0.20229 13.15 0 v 1 0.38017 0.38017 24.71 0 f 1 0.07337 0.07337 4.77 0.052 d 1 0.28674 0.28674 18.64 0.001 h 1 0.63507 0.63507 41.28 0 n 1 0.23174 0.23174 15.06 0.003 square 5 0.06311 0.01262 0.82 0.56 v*v 1 0.01935 0.01935 1.26 0.286 f*f 1 0.01108 0.01108 0.72 0.414 d*d 1 0.01108 0.01108 0.72 0.414 h*h 1 0.01108 0.01108 0.72 0.414 n*n 1 0.02991 0.02991 1.94 0.191 2-way interaction 10 2.54561 0.25456 16.55 0 v*f 1 0.20026 0.20026 13.02 0.004 v*d 1 0.00951 0.00951 0.62 0.448 v*h 1 1.24881 1.24881 81.18 0 v*n 1 0.01756 0.01756 1.14 0.308 f*d 1 0.01501 0.01501 0.98 0.345 f*h 1 0.11731 0.11731 7.63 0.019 f*n 1 0.00181 0.00181 0.12 0.738 d*h 1 0.03706 0.03706 2.41 0.149 d*n 1 0.36906 0.36906 23.99 0 h*n 1 0.52926 0.52926 34.4 0 error 11 0.16922 0.01538 lack-of-fit 6 0.04922 0.0082 0.34 0.888 pure error 5 0.12 0.024 total 31 5.4132 table 5: optimized input parameters in wect parameter optimal value applied voltage (v), v 23.67 longitudinal feed rate (f ), mm/min 0.5 wire diameter (d), mm 0.2 overlap distance ( h), mm 0.02 rotational speed ( n ), rpm 900 5.5 optimality search another objective of rsm is to find the region where the output of interest reaches or is very close to the optimal value. the purpose of optimality search is to evaluate the input parameters within the experiment ranges for minimizing ra. optimality search is done using utility transfer function (sait, aravindan, & haq, 2009). based on the results of this implementation, the optimal configurations for minimum surface roughness are as shown in table 5. according to eqn. 4, surface roughness at these configurations will be approximately zero. 6 conclusions wire electrochemical machining (wecm) is a popular non-traditional machining process for machining artificial materials with high strength and hardness. however, it is not easy to identify the optimal values of the machining parameters, such as voltage, feed rate, rotational speed, wire diameter, and overlap distance of the machining process. the use of optimal values of the machining parameters can enhance the key process characteristics such as the workpiece surface roughness and minimize the machining cost. this article proposes a combined scheme of statistical monitoring and optimization of electrochemical machining using shewhart charts and response surface methodology 76 response surface methodology (rms) and individuals chart in order to identify the optimal parameters of the wecm process. the applicability of the proposed scheme is tested through a real experiment. the output of the experiment is considered as surface roughness. the rsm is used to scientifically design and analyze all the experiments. the statistical control of the output (i.e. surface roughness) is evaluated using i&mr control chart. then, a prediction model linking the response (surface roughness ra) and the input parameters (voltage, feed rate, rotational speed, wire diameter, and overlap distance) is developed based on the statistically in-control output data as evident by the i&mr chart. finally, an optimization search is conducted to identify the optimal combination of the machining parameters, which results in minimizing the surface roughness. the held experiments reveal that factors (v, f, d, h and n) are considered significant and their optimal values are (23.67, 0.5, 0.2, 0.02, 900), respectively. the developed regression model can predict the output values with a r 2 = 96.9%. it can be concluded that the proposed combined scheme including rsm and shewhart chart might be an effective technique to guarantee the statistical control identify the optimal parameters of the wecm process. references 1. ahmad, t., & gilmour, s. g. (2010). robustness of subset response surface designs to missing observations. journal of statistical planning and inference, 140(1), 92-103. 2. anderson-cook, c. m., borror, c. m., & montgomery, d. c. (2009). response surface design evaluation and comparison. journal of statistical planning and inference, 139(2), 629-641. 3. asiltürk, i̇., neşeli, s., & i̇nce, m. a. (2016). optimisation of parameters affecting surface roughness of co28cr6mo medical material during cnc lathe machining by using the taguchi and rsm methods. measurement, 78, 120128. 4. benneyan, j., lloyd, r., & plsek, p. (2003). statistical process control as a tool for research and healthcare improvement. quality and safety in health care, 12(6), 458-464. 5. breitkopf, c., & swider-lyons, k. (2016). springer handbook of electrochemical energy: springer. 6. campatelli, g., lorenzini, l., & scippa, a. (2014). optimization of process parameters using a response surface method for minimizing power consumption in the milling of carbon steel. journal of cleaner production, 66, 309-316. 7. da silva neto, j. c., da silva, e. m., & da silva, m. b. (2006). intervening variables in electrochemical machining. journal of materials processing technology, 179(1), 92-96. 8. diel, c. l., canevesi, r. l. s., zempulski, d. a., awadallak, j. a., borba, c. e., palú, f., & silva, e. a. (2016). optimization of multiple-effect evaporation in the pulp and paper industry using response surface methodology. applied thermal engineering, 95, 18-23. 9. debnath, s., kunar, s., anasane, s., & bhattacharyya, b. (2017). non-traditional micromachining processes: opportunities and challenges non-traditional micromachining processes (pp. 1-59): springer. 10. drovandi, c. c., holmes, c., mcgree, j. m., mengersen, k., richardson, s., & ryan, e. g. (2017). principles of experimental design for big data analysis. statistical science, 32(3), 385-404. 11. el-taweel, t., & haridy, s. (2014). an application of fractional factorial design in wire electrochemical turning process. the international journal of advanced manufacturing technology, 75(5-8), 1207-1218. 12. haridy, s., maged, a., kaytbay, s., & araby, s. (2017). effect of sample size on the performance of shewhart control charts. the international journal of advanced manufacturing technology, 90(1), 1177-1185. doi:10.1007/s00170-016-9412-8 13. hofstede, a., & van den brekel, j. (1970). some remarks on electrochemical turning. annals of the cirp, 18, 93106. 14. khuri, a. i., & mukhopadhyay, s. (2010). response surface methodology. wiley interdisciplinary reviews: computational statistics, 2(2), 128-149. 15. kim, b. h., na, c., lee, y.-s., choi, d., & chu, c. (2005). micro electrochemical machining of 3d micro structure using dilute sulfuric acid. cirp annals-manufacturing technology, 54(1), 191-194. 16. maged, a., haridy, s., kaytbay, s., & bhuiyan, n. (in press). continuous improvement of injection moulding using six sigma: case study. international journal of industrial and systems engineering. 17. mukhopadhyay, s., & khuri, a. i. (2008). optimization in a multivariate generalized linear model situation. computational statistics & data analysis, 52(10), 4625-4634. 18. munda, j., & bhattacharyya, b. (2008). investigation into electrochemical micromachining (emm) through response surface methodology based approach. the international journal of advanced manufacturing technology, 35(7), 821-832. 19. myers, r. h., montgomery, d. c., & anderson-cook, c. (2009). response surface methodology, hoboken. new jersey: john wiley&sons, inc, 2(0), 38-38. 20. oakland, j. s. (2007). statistical process control: routledge. 21. qu, n., ji, h., & zeng, y. (2014). wire electrochemical machining using reciprocated traveling wire. the international journal of advanced manufacturing technology, 72(5-8), 677-683. maged et al., (2018): international journal of engineering materials and manufacture, 3(2), 68-77 77 22. sait, a. n., aravindan, s., & haq, a. n. (2009). optimisation of machining parameters of glass-fibre-reinforced plastic (gfrp) pipes by desirability function analysis using taguchi technique. the international journal of advanced manufacturing technology, 43(5-6), 581. 23. saleh, n. a., mahmoud, m. a., keefe, m. j., & woodall, w. h. (2015). the difficulty in designing shewhart x and x control charts with estimated parameters. journal of quality technology, 47(2), 127. 24. sarıkaya, m., & güllü, a. (2014). taguchi design and response surface methodology based analysis of machining parameters in cnc turning under mql. journal of cleaner production, 65, 604-616. 25. shamsuzzaman, m., haridy, s., alsyouf, i., & rahim, a. (2018). design of economic x̄ chart for monitoring electric power loss through transmission and distribution system. total quality management & business excellence, 1-21. doi:10.1080/14783363.2018.1433028 26. shin, h. s., kim, b. h., & chu, c. n. (2008). analysis of the side gap resulting from micro electrochemical machining with a tungsten wire and ultrashort voltage pulses. journal of micromechanics and microengineering, 18(7), 075009. 27. skinner, k. r., montgomery, d. c., & runger, g. c. (2003). process monitoring for multiple count data using generalized linear model-based control charts. international journal of production research, 41(6), 1167-1180. 28. thirugnanasambandham, k., sivakumar, v., & maran, j. p. (2015). response surface modelling and optimization of treatment of meat industry wastewater using electrochemical treatment method. journal of the taiwan institute of chemical engineers, 46, 160-167. 29. wang, s., zeng, y., liu, y., & zhu, d. (2012). micro wire electrochemical machining with an axial electrolyte flow. the international journal of advanced manufacturing technology, 63(1-4), 25-32. 30. woodall, w. h., & montgomery, d. c. (1999). research issues and ideas in statistical process control. journal of quality technology, 31(4), 376. 31. yamaguchi, k., & natsu, w. (2017). investigation of influence of low-level voltage on machining characteristics in pulse wire ecm. international journal of electrical machining, 22, 14. article international journal of engineering materials and manufacture (2018) 3(3) 151-161 https://doi.org/10.26776/ijemm.03.03.2018.04 thermo-mechanical and morphological properties of water hyacinth reinforced polypropylene composites manabendra saha and ali md. afsar received: 01 august 2018 accepted: 08 september 2018 published: 15 september 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract this paper focusses on the analysis of thermo-mechanical and morphological properties of water hyacinth (wh) fiber reinforced polypropylene (pp) biocomposites manufactured by using a single screw extruder and an injection molding machine. with a view to increasing the compatibility between the wh fibers and polypropylene matrix, raw wh fibers were chemically treated with benzenediazonium salt in base media. composites were manufactured with five different levels of loading (15, 20, 25, 30 and 35 wt%) of both the raw and treated wh fibers. thermal properties of wh-pp composites were evaluated by thermogravimetric and differential thermal analyses. to analyze mechanical properties of composites, tests of tensile strength and stiffness, flexural strength and stiffness, and charpy impact strength were carried out following astm standards. it was found that thermal stability and all the mechanical properties except tensile strength were improved considerably for chemically treated wh fiber composites in comparison with untreated ones. fracture surfaces of the tensile and flexural specimens were scanned with scanning electron microscopy (sem) to understand their surface morphologies. the sem images clearly revealed that there were fewer fiber agglomerations, microvoids, and fiber pull out traces in treated wh-pp composites than in the untreated ones indicating better distribution of the fibers into the matrix as well as stronger fiber matrix interfacial adhesion due to treatment of wh fibers. water absorption properties were studied to evaluate the viability of these biocomposites under specified conditions. keywords: thermo-mechanical properties, scanning electron microscopy, water hyacinth fiber, polypropylene, biocomposites 1. introduction natural fiber reinforced polymer matrix composites, often called biocomposites, are now preferred over artificial fiber reinforced composites as natural fiber composites have outstanding advantages of environment friendliness, biodegradability, recyclability, cost-effectiveness, and better physico-mechanical properties [1-6]. the using of biobased lignocellulosic natural fibers as reinforcing materials for manufacturing of biocomposites is gaining more and more approval day by day due to their flexibility during processing (require low processing temperature), higher specific stiffness, lightweight, non toxic properties, and low cost. so far, numerous researches have been carried out on the polymer composites [7-13], where different natural fibers such as wood fibers and flour, kenaf fibers, sago, rice starch, corn starch, pineapple leaf fibers, and coir fibers were used as fillers in polymer matrices. among various natural fibers easily available to human beings, water hyacinth (eichhornia crassipes) is one of the cheapest fibers and quite new in reinforcing thermoplastics. an experimental study to evaluate the mechanical and thermal properties of water hyacinth (wh) fiber reinforced low density polyethylene (ldpe) composites was conducted by supri et al.[14]. this study appears to be the first attempt of using wh fibers as a reinforcing material. they observed good mechanical properties of wh-ldpe composites lead to concluded that wh fibers have a great potential to use as a filler materials m. saha1, 2 and a. m. afsar2 1 school of mechanical engineering the university of adelaide, sa 5005, australia e-mail: manabendra.saha@adelaide.edu.au, 2department of mechanical engineering bangladesh university of engineering and technology dhaka 1000, bangladesh e-mail: mdafsarali@me.buet.ac.bd reference: saha, m., and afsar, a. m. (2018). thermo-mechanical and morphological properties of water hyacinth reinforced polypropylene composites. international journal of engineering materials and manufacture, 3(3), 151-161. mailto:manabendra.saha@adelaide.edu.au thermo-mechanical and morphological properties of water hyacinth reinforced polypropylene composites in polymeric composites owing to their high content of cellulose. however, no systematic studies have been conducted for better understanding the thermal and mechanical properties of wh fiber reinforced polypropylene (pp) composites. wh is abundant in nature and reproduces freely on the surface of fresh water and also has a minimal effect on the environment due to their biodegradable properties [8]. therefore, it is necessary to systemically explore the thermo-mechanical and morphological properties of wh-pp biocomposites to know their potential applications as engineering materials. the physico-mechanical properties of lignocellulosic biocomposites mostly depend on the type of matrix, the properties and volume fraction of the reinforcing fibers, and fiber–matrix interaction. uniform dispersion of the reinforcements can be achieved by effective mixing of the components and a proper compounding process. like other natural fibers, one shortcoming that restricts the extensive usage of the wh fibers is the lack of good adhesion with most polymeric matrices [8, 14, 15]. the hydrophilic nature of wh fibers adversely affects adhesion with hydrophobic polypropylene (pp) matrix that may cause a loss of strength. to get rid of this problem, the surfaces of wh fibers have to be modified by suitable chemical treatment in order to promote adhesion. it is reported [6] that the compatibility between fibers and matrix materials can be improved to a large extent by chemical treatments of the lignocellulosic fibers using a suitable chemical agents [6]. the effect of chemical treatment on coir fibers with benzenediazonium salt was analysed by haque et al. [16]. coir fibers were seen to have immense potential of better compatibility with pp after chemical modification and consequently the mechanical properties of the composites were increased significantly. edeerozey et al. [6] reported that alkalization treatment of kenaf fibers with naoh had improved significantly the mechanical properties of the kenaf fiber reinforced composites as compared to that of untreated fibers. islam et al. [7] investigated the effect of chemical pre-treatment of wood fibers with 5% alkaline naoh solution on physical and mechanical properties of wood polymer composites. they found that the chemical modification improved overall properties of the composites compared to that of the untreated fiber reinforced composites. this improvement was attributed to the better adhesion between polymer matrix and the chemically treated wood fibers. in the present paper, raw wh fibers were chemically treated with benzenediazonium salt in alkaline medium to increase the compatibility and adhesion of the wh fibers with the pp matrix. composites were manufactured with both the treated and raw wh fibers and pp by using a single screw extruder and an injection molding machine. the thermo-mechanical and surface morphological properties of the wh-pp composites are presented. also, the effect of the fiber loading on the above properties of the wh-pp composites are analysed and discussed. 2. experimental 2.1 materials the thermoplastic polypropylene (pp) used as matrix material was supplied by the linyi aosen chemicals co. ltd., shandong, china, in the form of homo-polymer pellets. according to the manufacturer, the melt flow rate (mfr) of 8 g/10 min and melting temperature of 165–171 ˚c were noted for the specified pp. the fresh water hyacinth fiber was collected from local area of bangladesh. the stems of the fresh water hyacinth were cleaned to remove adhering dirt and cut into small pieces followed by drying under solar radiation for 48 hours to evaporate any trace of water content. the dried water hyacinth was ground into powder, named as water hyacinth (wh) fibers. it comprises 18.4% cellulose, 49.2% hemicellulose, 3.55% lignin, 12.60% crude protein, and 16.25% other constituents [17]. the measured diameter of the wh fibers was between 350 to 400 µm. chemicals used in this study to treat wh fibers were hydrochloric acid (hcl), sodium nitrite (nano2), sodium hydroxide (naoh), aniline (c6h5nh2), and n,ndimethyle aniline c6h5n(ch3)2. 2.2 chemical treatment of wh fiber in an attempt to improve mechanical properties of the composites, wh fibers were chemically treated using benzenediazonium salt. the hydroxyl group in the raw wh fibers is responsible for high water absorption and weak interfacial bond between the fibers and pp matrix. the chemical treatment converts the hydroxyl groups into diazo group and results in azo product, 2,6-diazocellulose. benzenediazonium salt was synthesized by the standard diazotization method using both aniline and n,n-dimethyle aniline (nndma). wh fibers were dried at 105°c for 24 hr in order to minimize its moisture content to 1–2% and then kept in a sealed container. one litter 5% naoh solution was taken in a 5 litter beaker into which 750 g wh fibers were submerged and kept for 10 min at about 5°c in an ice bath. a freshly prepared cooled (temperature below 5°c) solution of benzenediazonium salt was then poured slowly into the above mixture with constant stirring and kept for about 10 min. later, the fibers were washed properly with distilled water and dried in open air under sunlight for 36 hours. wh fibers were treated with two types of benzenediazonium chloride: (anl)/naoh and (nndma)/naoh. 2.3 fabrication of composites wh fibers were weighed according to the required weight fraction of fibers. then they were dried in an oven at a temperature slightly higher than 100 °c for about 1 hr to evaporate any trace of moisture. weighed amount of commercial polypropylene was taken in a beaker. to prevent voids, water bubbles, poor fiber–matrix adhesion, the polypropylene was dried in an oven at about 100 °c for 3 hr [4]. wh fibers were manually mixed thoroughly with pp granule in the beaker at various weight proportions. the wh fibers and pp were then melt-mixed by passing them 152 saha and afsar (2018): international journal of engineering materials and manufacture, 3(3), 151-161 through a single screw extruder machine. the processing temperature of the extruder was controlled at 165°c. the melt-mixed wh-pp was delivered from the extruder in the form of a rod of small diameter. the rod shaped meltmixed wh-pp was cut into small pieces of 5-10 mm length by a scissor. the small pieces of melt-mixed wh-pp products were then fed into an injection molding machine in order to prepare composite specimens directly as per astm standard. the injection molding temperature was maintained at 165°c. the injection-molding machine was vertical and operated manually. the tensile test specimens and bending test specimens were fabricated by using corresponding die in the injection molding machine. finally, the specimens were carefully discharged from the die after complete cooling. 2.4 thermal property the thermogravimetric analysis (tga) and derivative thermal gravimetric (dtg) analysis were conducted by a tg/dta-630 module analyser. the samples were scanned from 25°c to 600°c at 20°c/min in the presence of nitrogen. 2.5 mechanical property in order to investigate the mechanical properties of the wh-pp composites, tensile, three point bending, and charpy impact tests were carried out. the static tensile test of the composites were carried out in an universal tensile testing machine (model hounsfield utm (h10ks), capacity: 10kn, ogawa seiki c. ltd., japan) at a cross head speed of 5 mm/min. tensile tests were carried out following astm d 638-01, 2002 standard. the tensile strength and young’s modulus were calculated automatically by the qmat software. three point bending tests were carried out according to astm d 790-00, 2002 using the same testing machine mentioned above at the same crosshead speed. the dynamic charpy impact tests were conducted according to astm d 6110-97, 2002 using an universal impact testing machine (type: tit-30, tokyo testing machine mfg. co. ltd., japan). weight of the hammer of this machine was 20.54 kg. notched composite specimens were used during the experiment. 2.6 water absorption property the water absorption tests of the composites were carried out following astm: d 570-98, 2002. to measure the water uptake capacity of the composites, rectangular specimen of dimension76 mm × 25 mm × 3.4 mm was prepared. from the difference of the final and initial weights before and after immersion in a water bath for 24 hr, percentage of water uptake was calculated. in each test and type of composite, 10 specimens were tested and the average values are reported. 2.7 morphological properties the morphology of the fracture surfaces of composites were studied by using scanning electron microscope (sem), model: jsm-5510 sem analyser from jeol co. ltd., japan. since the wh-pp composites are not conductive, before the examination of sem, the fractured samples were mounted on aluminium stubs and allowed to undergo sputtering coating to make the samples conductive. the sample surfaces were sputter-coated with a thin gold layer of 20 nm to avoid electrostatic charging during examination. 3. results and discussions 3.1 thermal properties thermal characteristics of raw and treated wh fiber reinforced composites are displayed in figs. 1 and 2. the dtg and tga have been carried out to evaluate the thermal stability and degradation of 35 wt% wh-pp composites. the dtg curves (fig.1) of all composites showed an initial peak between 260 ˚c and 350 ˚c which corresponds to the thermal decomposition of hemicelluloses and the glycoside linkage of cellulose. after this peak, the curve corresponding to benzenediazonium salt (nndma)/naoh treated wh-pp composite exhibits single peak at 469 ˚c temperature while the raw wh-pp composite exhibits the peak at 462 ˚c temperature. the dtg curve of benzenediazonium salt (anl)/naoh treated wh-pp composite exhibits single decomposition with the highest peak at decomposition temperature of 478˚c. the peak in the range of 400-500˚c is due to the thermal decomposition of lignin and α cellulose [9]. figure 2 shows the results of thermal gravimetric analysis (tga) of wh-pp composites with 35% fiber loading. table 1 shows the temperature of 50% weight loss, the final decomposition temperature, and residual mass of raw and treated wh-pp composites. these results show that benzenediazonium salt, (anl)/naoh, treated wh-pp composites exhibit more thermal stability than those of benzenediazonium salt, (nndma)/naoh, treated wh-pp composites and raw wh-pp composites in terms of the highest final decomposition temperature and largest amount of residual mass. the raw wh-pp composites have shown least thermal stability. this was due to the presence of good interfacial adhesion between chemically modified wh fibers and pp as a result of uniform dispersion of fiber throughout the pp matrix. the better dispersion of filler acts as a barrier against the release of volatile matter from the composites during the thermal degradation. it also might be attributed to an adsorption effect of volatile gases at the fiber surface which affects to slow down the decomposition rate of polymer composites[18]. 153 thermo-mechanical and morphological properties of water hyacinth reinforced polypropylene composites table 1: decomposition temperature of 35 wt% wh-pp composites composites derivative thermal gravimetric (dtg) analysis thermogravimetric analysis (tga) decomposition beginning temp. (˚c) decomposition peak temp. (˚c) t-50 %wt (˚c) final decomposition temp. (˚c) residual mass (%) raw wh-pp 269 462 453 597 3.09 nndma/naoh treated wh-pp 329 469 458 598.5 5.59 anl/naoh treated wh-pp 345 478 472 598.5 9.65 figure 1: derivative weight loss of 35 wt% wh-pp composites as a function of temperature figure 2: weight of 35 wt% wh-pp composites as a function of temperature 154 saha and afsar (2018): international journal of engineering materials and manufacture, 3(3), 151-161 3.2 mechanical properties 3.2.1 tensile properties the tensile strengths of the raw and chemically treated wh-pp composites at different fiber loadings are shown in fig. 3. it is observed from the figure that the tensile strength of the wh-pp composites decreased with fiber loading. similar results were also reported by other researchers [4, 12-14, 18-21]. wh fibers are hydrophilic in nature owing to the presence of hydroxyl groups of the cellulose of wh, whereas the nature of pp is hydrophobic. thus, the hydrophilic wh fiber does not interact well with the hydrophobic pp. as a consequence, the weak interfacial area between the wh fiber and pp matrix was increased with the increment of fiber loading that contributes to the decreasing trend of tensile strength. in order to increase the compatibility of the wh fibers with pp matrix, raw wh fibers were chemically treated with (anl)/naoh and (nndma)/naoh. this consequently increased the tensile strength of (anl)/naoh treated wh-pp composites. it is found that the tensile strength increased approximately 4– 12% over the raw wh fiber composites. the overall change of tensile strength due to the effect of chemical treatment may be due to the change in the structure of the cellulose unit of wh. the chemical treatment of wh reduced the hydroxyl group of the cellulose unit by coupling with basic diazonium salt. however, tensile strength of (nndma)/naoh treated wh-pp composites decreased slightly over the raw wh-pp composites. the reason behind the decrease of tensile strength in this case is not well understood. the chemical reaction pathway is expected to be more complex than that of previous case, however the decreasing trend of tensile strength of (nndma)/naoh treated wh-pp composites with fiber loading is not dissimilar of raw or (anl)/naoh treated wh-pp composites. however, in all the cases of composites, the strength is lower than that of neat pp. figure 4 exhibits the young’s modulus of the composites corresponding to different fiber loadings. as expected, the addition of fiber increases the modulus of the composites, resulting from the inclusion of rigid fiber into the soft pp. this observation suggests that the incorporation of rigid fibers into the soft thermoplastic pp increases the stiffness of the composite. the chemically treated wh-pp composites are found to show higher modulus compared to those of the untreated ones. this indicates that homogeneous dispersion of wh fibers and better fiber–matrix interaction can be achieved by treatment of wh fibers. the range of the young’s modulus found in the present research is between 608-761 mpa, which is significantly higher than that obtained in a previous research [15] (150-260 mpa) using the same fiber material. the higher values of the young’s modulus found in the current research might be due to the chemical treatment of wh fiber and use of different matrix material. between the two treated fiber composites, (anl)/naoh treated wh-pp composite appears to be better in terms of tensile strength and modulus than those of (nndma)/naoh treated wh-pp composite. figure 3: effect of fiber loading on tensile strength of wh-pp composites 3.2.2 flexural properties the variation of the flexural strength and modulus of both raw and treated wh reinforced pp biocomposites at different fiber loadings is shown in figs. 5 and 6, respectively. from fig. 5, it is seen that the flexural strength of raw wh-pp composite increased with fiber loading up to 25% followed by reduction of strength for further addition of fibers. on the other hand, for chemically treated wh fiber reinforced pp composites, flexural strength increased 155 thermo-mechanical and morphological properties of water hyacinth reinforced polypropylene composites steadily with the increase of the fiber content. the steady behaviour of flexural strength of the treated wh-pp composites could be a balance in the favourable entanglement of the polymer chain with the filler and opposing weak filler-matrix interfacial adhesion with increasing filler content. the (nndma)/naoh treated wh-pp composites yielded higher flexural strength compared to the other wh-pp composites. it is found that the flexural strength increased by approximately 10-28% over the raw wh fiber composites, while the increment was 4–11% over (anl)/naoh treated wh-pp composites. it is evident from fig. 6 that the addition of wh fibers to pp has significantly increased the modulus of the composites, which is found to be in good agreement with the results of previous studies [8, 14, 15]. since wh fiber is a high modulus material [14], higher fiber concentration in the composites demands stronger stress for the same amount of deformation. consequently, flexural modulus of the composites increases with an increase in the fiber content. both the flexural strength and modulus are found to be higher for chemically treated fiber, which could be due to better fiber-matrix interfacial adhesion and effective stress transfer from the matrix to the fiber. figure 4: effect of fiber loading on the young’s modulus of wh-pp composites figure 5: flexural strength as function of fiber loading in wh-pp composites 156 saha and afsar (2018): international journal of engineering materials and manufacture, 3(3), 151-161 figure 6: flexural modulus as a function of fiber loading in wh-pp composites 3.2.3 impact strength charpy impact strength as a function of fiber content of both the raw and chemically treated wh fiber reinforced pp composites is shown in fig. 7. the charpy impact strength test is a standardized high strain-rate test which determines the amount of energy absorbed by a material during fracture. this absorbed energy is a measure of a given material’s toughness and acts as a tool to study brittle-ductile transition. for fiber-reinforced polymeric composites, it depends on a number of factors, such as the nature of the fiber, polymer matrix, and the polymer-matrix interfacial bonding. an increase in toughness, i.e., increase in the resistance of crack propagation occurs if fiber bridges the crack in the composites [4, 19]. as shown in fig. 7, impact strength of both the raw and treated whpp composites show an increasing trend with an increase in the fiber loading, implying that the fiber is capable of absorbing energy. further, treated wh-pp composites have improved impact strength over untreated wh-pp composites. this ensures the improved interfacial bonding between fibers and matrix providing an effective resistance to crack propagation during impact tests. again, (nndma)/naoh treated wh-pp composites exhibit higher impact strength than those of (anl)/naoh treated composites. it is found that the impact strength of (nndma)/naoh treated wh-pp composites increased by approximately 31-78% over the raw wh fiber composites, while the increment was 25-50% over (anl)/naoh treated wh-pp composites. significantly higher impact strength for (nndma)/naoh treated wh-pp composites is probably due to the favourable interaction between the treated wh fiber and the hydrophobic pp chain of the matrix. it is speculated that the so-called fiber pullout and fiber agglomeration could be responsible for the lower impact strength of raw wh-pp composites. 3.2.4 water absorption characteristics water absorption of wh fiber reinforced pp composites is one of the important characteristics that determines the suitability of terminal applications of these composites. water absorption could lead to a decrease in some of the properties and needs to be considered when selected for a specific application. in fact, it is difficult to eliminate entirely the absorption of moisture from the composites without using expensive surface coatings on the surface of composites and/or fibers. water absorption in lignocellulosic fiber-enriched composites can lead to build up of moisture in the fiber cell wall and also in the fiber-matrix interphase region. water absorption characteristics of the wh-pp composites against fiber loading are shown in fig. 8. it shows that water absorption increased with an increase in fiber loading. usually natural fiber-polymer composites without compatibilizer show remarkable water absorption due to the presence of voids [4, 11, 16, 21-23]. with an increase in fiber loading, the number of hydroxyl groups as well as microvoids in the composites increases, which result in an increase in water absorption. however, chemically treated wh fiber reinforced composites of the present study are found to show lower water absorption tendency compared to the untreated ones, indicating that the hydrophilic nature of wh fiber has substantially decreased upon chemical treatment with benzenediazonium salt. this can directly be attributed to the decrease in the number of 157 thermo-mechanical and morphological properties of water hyacinth reinforced polypropylene composites hydroxyl groups responsible for the hydrophilic nature of the cellulose that converted into diazo group and results in azo product, 2,6-diazocellulose. no dimensional change was observed upon immersion of the composites in water. this indicates that fibers are thoroughly encapsulated in the matrix. at the same time, it can also be ascribed that, due to favourable interaction between the matrix and the treated fibers, microvoids in the composites have substantially minimized, exhibiting lower water uptake tendency. figure 7: impact strength versus fiber loading curves of wh-pp composites figure 8: water absorption characteristics of wh-pp composites 158 saha and afsar (2018): international journal of engineering materials and manufacture, 3(3), 151-161 3.3 morphological properties the surface morphology of tensile and flexural fracture surfaces reflects the reasons why mechanical properties of composites prepared from fibers of different surface properties are different. the morphological features of tensile and flexural fracture surfaces of 35 wt% wh fiber reinforced pp biocomposites investigated by sem are shown in fig. 9. figures 9(a) (c) represent the fracture surfaces of tensile specimens while figs. 9(d) (f) represent the fracture surfaces of flexural specimens. it can be easily traced out that there are a number of agglomerations resulting from strong fiber-fiber interaction and fiber pullout marks in the sem images of the raw wh fiber reinforced pp composite (fig. 9a). this implies that there is poor interfacial bonding between the matrix and the raw fibers. the raw wh fibers can be clearly seen in the composite micrograph of fig. (9)d due to fiber pullout as a result of weak interfacial bonding between the eaw fiber and matrix.. for this reason, the raw wh-pp composites had worst set of mechanical properties. from sem images of chemically treated composites (figs. 9(b), (c), (e), and (f)), it is seen that the fibers and matrix are not clearly differentiable due to improved interfacial bonding between them. during chemical treatment, hydrophilic –oh groups in the raw wh cellulose were converted to hydrophobic groups. consequently, the interaction and interfacial bonding between the wh fibers and the pp matrix was increased, which in turn, increased the physico-mechanical properties of the resultant composites. also, sem images of chemically treated whpp composites show almost no signs of fiber agglomeration and microvoids in the fracture surface of the composite. in addition, the pullout traces are found to have substantially decreased for treated wh-pp composites. this supports that the interfacial adhesion between the chemically treated wh fiber and the pp matrix has become much more favourable upon treatment of the fibers. figure 9: sem micrographs of 35 wt% wh-pp composites: (a) tensile fracture surface of raw wh composite, b) tensile fracture surface of (nndma)/naoh treated wh composite, c) tensile fracture surface of (anl)/naoh treated wh composite, (d) flexural fracture surface of raw wh composite, (e) flexural fracture surface of (nndma)/naoh treated wh composite, and (f) flexural fracture surface of (anl)/naoh treated wh composite. 159 thermo-mechanical and morphological properties of water hyacinth reinforced polypropylene composites 4. conclusions the effects of fiber loading and chemical treatment of wh fibers on the thermo-mechanical and morphological properties on wh-pp composites have been investigated. it is found that wh fibers as renewable materials can be used to manufacture useful composites with good thermal stability and mechanical properties. the following conclusions could be drawn from the experimental results of this study: 1. raw, (anl)/naoh, and (nndma)/naoh) treated wh (35 wt%) fiber reinforced pp composites are thermally stable up to 273 c, 294 c, and 284 c, respectively. (anl)/nao -pp composites exhibit the best thermal properties in terms of thermal stability and lowest derivative weight loss with respect to time. 2. the tensile strength of the wh-pp biocomposites decreased with an increase in the wh fiber loading. however, the treatment of fibers with (anl)/naoh gives the maximum tensile strength of the composites. thus, the treatment of wh fibers with (anl)/naoh is recommended when strength is the main concern. 3. in all the cases of composites, the young’s modulus, flexural strength, flexural modulus, and charpy impact strength are found to increase with an increase in fiber loading and the values are found to be higher for treated wh-pp composites than those of the untreated ones. it is concluded that interaction between the fiber and the matrix has become more favourable upon chemical treatment of wh fibers. 4. chemical treatment resulted in lower water absorption for treated wh-pp composites compared to raw wh-pp composites. this indicates that hydrophilic nature of wh fiber was reduced upon chemical treatment of wh fiber with benzenediazonium salt in basic medium. 5. morphological study of the fracture surface of wh-pp composites shows that, due to favourable interaction between the treated wh fibers and pp, microvoids in the composites are minimized, dispersion of the fibers in the matrix are improved, agglomeration of fibers in the composites and pulling out of fibers are reduced. the above features ensure the net benefits of the composites of interest of this study. furthermore, the composites of the present study are biodegradable, cost effective as wh is easily available in nature and environment friendly. therefore, these composites could be considered as alternatives to costlier wood and can find applications in furniture, door panels, table tops and other potential applications. 5. acknowledgement the authors gratefully acknowledge the financial assistance of bangladesh university of engineering and technology. the authors would also like to thank prof. monimul huque, buet, for his insights into chemical treatment of the fibers and dr md abdul gafur, bcsir, dhaka, for useful discussions while carrying out experiments in bcsir laboratories. references 1. kabir m, wang h, lau k, cardona f. chemical treatments on plant-based natural fibre reinforced polymer composites: an overview. composites part b: engineering. 2012;43:2883-92. 2. faruk o, bledzki ak, fink h-p, sain m. biocomposites reinforced with natural fibers: 2000–2010. progress in polymer science. 2012;37:1552-96. 3. la mantia f, morreale m. green composites: a brief review. composites part a: applied science and manufacturing. 2011;42:579-88. 4. islam mn, haque mm, huque mm. mechanical and morphological properties of chemically treated coir-filled polypropylene composites. industrial & engineering chemistry research. 2009;48:10491-7. 5. john mj, thomas s. biofibres and biocomposites. carbohydrate polymers. 2008;71:343-64. 6. edeerozey amm, akil hm, azhar ab, ariffin miz. chemical modification of kenaf fibers. materials letters. 2007;61:2023-5. 7. islam ms, hamdan s, sobuz hr, rahman r, ahmed as. thermal and decay-resistance properties of tropical wood–plastic composites. journal of composite materials. 2013;47:1493-500. 8. saha m, rahman mh, ali ma. effect of fiber loadings on mechanical properties of water hyacinth fiber reinforced polypropylene composites. proceedings of the international conference on mechanical engineering 2011. dhaka, bangladesh: icme11-am-048; 2011. 9. bledzki ak, mamun aa, volk j. physical, chemical and surface properties of wheat husk, rye husk and soft wood and their polypropylene composites. composites part a: applied science and manufacturing. 2010;41:480-8. 10. oksman k, mathew ap, långström r, nyström b, joseph k. the influence of fibre microstructure on fibre breakage and mechanical properties of natural fibre reinforced polypropylene. composites science and technology. 2009;69:1847-53. 11. haque mm, hasan m, islam ms, ali me. physico-mechanical properties of chemically treated palm and coir fiber reinforced polypropylene composites. bioresource technology. 2009;100:4903-6. 12. garkhail s, heijenrath r, peijs t. mechanical properties of natural-fibre-mat-reinforced thermoplastics based on flax fibres and polypropylene. applied composite materials. 2000;7:351-72. 160 saha and afsar (2018): international journal of engineering materials and manufacture, 3(3), 151-161 13. amash a, zugenmaier p. morphology and properties of isotropic and oriented samples of cellulose fibre– polypropylene composites. polymer. 2000;41:1589-96. 14. supri ag, ismail h. the effect of nco-polyol on the properties of low-density polyethylene/water hyacinth fiber (eichhornia crassiper) composites. polymer-plastics technology and engineering. 2010;49:766-71. 15. supri ag, tan s, ismail h, teh p. effect of poly (methyl methacrylate) modified water hyacinth fiber on properties of low density polyethylene/natural rubber/water hyacinth fiber composites. polymer-plastics technology and engineering. 2011;50:898-906. 16. haque m, islam n, huque m, hasan m, islam s, islam s. coir fiber reinforced polypropylene composites: physical and mechanical properties. advanced composite materials. 2010;19:91-106. 17. kumar a, singh l, ghosh s. bioconversion of lignocellulosic fraction of water hyacinth (eichhornia crassipes) hemicellulose acid hydrolysate to ethanol by pichia stipitis. bioresource technology. 2009;100:3293-7. 18. herrera-franco p, valadez-gonzalez a. a study of the mechanical properties of short natural-fiber reinforced composites. composites part b: engineering. 2005;36:597-608. 19. mir ss, nafsin n, hasan m, hasan n, hassan a. improvement of physico-mechanical properties of coirpolypropylene biocomposites by fiber chemical treatment. materials & design. 2013;52:251-7. 20. islam s, hamdan s, jusoh i, rahman r, ahmed as. the effect of alkali pretreatment on mechanical and morphological properties of tropical wood polymer composites. materials & design. 2012;33:419-24. 21. haque mm, islam ms, islam mn. preparation and characterization of polypropylene composites reinforced with chemically treated coir. journal of polymer research. 2012;19:1-8. 22. rahman mr, hasan m, huque mm, islam mn. physico-mechanical properties of jute fiber reinforced polypropylene composites. journal of reinforced plastics and composites. 2010;29:445-55. 23. huda m, drzal l, misra m, mohanty a. wood fiber reinforced poly (lactic acid) composites: evaluation of the physicomechanical and morphological properties. journal of applied polymer science. 2006;102:4856-69. 161 international journal of engineering materials and manufacture (2019) 4(3) 85-95 https://doi.org/10.26776/ijemm.04.03.2019.01 a. s. rao and a. k. singh defence metallurgical research laboratory kanchanbagh, hyderabad, 500058, india e-mail: singh_ashok3@rediffmail.com reference: rao, a. s. and singh, a. k. (2019). blade lock ring of 4 th stage compressor rotor: failure investigation. international journal of engineering materials and manufacture, 4(3), 85-95. blade lock ring of 4 th stage compressor rotor: failure investigation aginaparru sambasiva rao and ashok kumar singh received: 14 may 2019 accepted: 03 september 2019 published: 27 september 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract present work describes the failure investigation of blade lock ring of 4 th stage compressor rotor. the lock ring is fabricated from martensitic stainless steel. the microstructure of failed lock ring is tempered martensite. it shows non-metallic inclusions with three distinct shapes namely, elongated (mns), globular (al2o3) and complex shaped (oxy-sulphide). the corrosion pits and corrosion debris are observed in un-etched microstructure and fracture surface, respectively. the tree like branching cracks has observed at several places near surface. these cracks have initiated from the corrosion pits and then propagated inside the material. the interface of inclusions and matrix has also acted as crack initiator. the lock ring has initially suffered pitting corrosion in service and then cracks have propagated inside the material by stress corrosion cracking. keywords: lock ring; stainless steel; inclusions; pitting; stress corrosion cracking. 1. introduction the main purpose of compressor rotor is to raise the pressure of incoming air to have an efficient combustion in the combustion chamber and to generate enough thrust to propel the aircraft [1]. air entering the compressor section is compressed and delivered into the combustor section where it is mixed with fuel and then ignited to generate high-speed exhaust gas flow [2] .the compressor rotor blades from 4 th to 9 th stages are made up of ni-base alloys. these are mounted to a fan hub and a blade lock assembly is used to axially retain the fan blades within corresponding fan hub slots. blade lock assembly includes a lock ring that is axially slid onto the fan hub in an unlocked position and rotated to a locked position. this includes a fan hub that has blade slots each configured to receive a root of a fan blade. the locking ring includes circumferentially spaced second slots aligned with the first slots in the locked position and multiple discrete pins. blade lock ring of 4 th stage compressor rotor of aero engine had failed and found broken during overhauling. total number of hours utilized the existing lock ring since new is 931:29 hours. however, expected life of the lock ring as per specification is 1500 hrs. present work describes the metallurgical failure analysis of blade lock ring of 4 th stage compressor rotor which was pre-maturely failed. 2. experimental initially, the failed blade lock ring segments were examined visually and photographs of failed ends as well as typical flat surfaces of both the parts were captured using high resolution digital camera in as-received condition. in order to examine the surface cracks (if any) on the flat surface of failed ring, non-destructive test was carried out on both sides of plane surfaces using dye penetrate test. drillings were taken from the region slightly away from the failed region for wet chemical analysis. in addition, small pieces of about 3  4 mm2 size were also cut for carbon and sulphur analysis. bulk chemical composition was analysed using inductively coupled plasma-optical emission spectroscopy (icp-oes). the interstitial elements such as c and s were measured using inert gas fusion technique. samples were cut from the failed region and mounted its plane surface in bakalite mounts in order to examine the microstructure under optical and scanning electron microscopes (om and sem).these samples were mounted and prepared using standard metallographic procedure. surface irregularities near failed region and morphology of non-metallic inclusions (if any) were examined in as-polished samples using optical microscope in an un-etched condition. the polished samples were further etched with aquaregia (50% hcl and 50% hno3 by volume) and microstructural characterization was done using optical microscope. samples were cut from the fracture ends of both the counter parts of failed lock ring and cleaned ultrasonically in acetone to remove dirt and other residues mailto:singh_ashok3@rediffmail.com blade lock ring of 4 th stage compressor rotor: failure investigation 86 over the fracture surface. fracture surfaces were studied using fei make environmental sem (model: quanta 400) in secondary electron (se) mode. energy dispersive spectroscopy (eds) was employed to evaluate the contaminated products over the fracture surfaces. longitudinal sections of as-polished samples obtained from close to fracture as well as away from the failed region were also examined using cameca make, sx-100 model electron probe micro analyser (epma) in un-etched condition. in order to confirm the type and morphology of inclusions in the failed lock ring, x-ray elemental distribution mappings were carried out using epma technique. x-ray mappings of mn, s, al, si and o elements were carried out at 20 kv and 20 na current. x-ray elemental mappings were gathered for each element separately and correlated with respective back scattered electron (bse) image for interpretation. hardness measurements were carried out using vickers hardness tester with 30 kg load. the hardness values were reported after taking an average of 10 measurements. 3. results 3.1. visual examination photograph of broken lock ring in as-received condition is shown in fig. 1. the ring is in the form of flat surface all around the circumference. the width and the thickness of the lock ring are 5.5 and 2.5 mm, respectively. it clearly shows that the lock ring has broken into two pieces. these rings are smooth and shiny surface finish on both plane surfaces. it also exhibits several micro-cracks along one side of plane surface of the both parts of lock rings and are extended from one end to other end (fig. 2a). these cracks are confirmed by dye penetrate (dp) test and also with stereo microscopic examinations (figs. 2a and 3). close inspection of the fracture surface in stereo microscope of failed lock ring displays two distinct features with dark and bright contrast (fig. 2b). the major part (75%) of the fracture surface exhibits dull and dark contrast while the remaining part (25%) is bright and shiny. figure.1: broken parts of lock ring in as-received condition. figure. 2: stereo micrographs of failed lock ring: (a) irregular crack across the width on one plane surface and (b) dark and bright fracture surface obtained from broken lock ring. rao and singh (2019): international journal of engineering materials and manufacture, 4(3), 85-95 87 figure.3: photograph of post dye penetrant test showing several cracks across the width on one plane surface of failed lock ring (magnified image of crack region is shown as inset). figure. 4: sem fractographs: (a) fracture features from dark region, (b) magnified image of (a) reveals several mud cracks, (c) fracture surface of entire fracture surface with distinct regions and (d) magnified image of (c) from mating surface between dark and bright regions. 3.2. sem fractography se images of fracture surface corresponds to entire fracture area has been examined and the fractographs taken at different magnifications are shown in fig. 4. the fracture characteristics of dark region are quite different from that of the bright region. specifically, thick layer of contaminated foreign material has masked over the dark region of fracture surface (fig. 4a). magnified micrograph of the dark region demonstrates extensive mud cracks which are typical of corrosion derbies (fig. 4b). on the contrary, bright region of fracture surface reveals cleavage facets (fig. 4 c and d). it also illustrates grain boundary cracks close to the mating surface between dark and bright fracture regions (fig. 4 c and d). blade lock ring of 4 th stage compressor rotor: failure investigation 88 3.3. energy dispersive spectroscopy (eds) eds analysis was carried out on the dark region of the fracture surface. the eds spectrum reveals the presence of c, o, ca, cl, na, mg, al, si and k along with elements pertaining to parent material (fig. 5). this also confirms that the dark fracture region is enveloped with corrosion products. 3.4. optical microstructure longitudinal samples prepared from plane surface of failed lock ring exhibits typical tempered martensite structure in-etched condition (fig. 6). the microstructure of the samples close to fracture surface in un-etched condition is shown in fig. 7. surface close to outermost edge exhibits surface pitting at several locations. it indicates that the material was degraded during service and also part of the same has dislodged from the parent material due to localized pitting. the formation of pitting is quite severe at the surface than that of the interior of the lock ring. figure. 5: eds spectrum of the dark region of fracture surface showing corrosion products along with major elements of parent material. figure. 6: microstructures showing tempered martensite: (a) low and (b) high magnifications. rao and singh (2019): international journal of engineering materials and manufacture, 4(3), 85-95 89 figure. 7: optical microstructures of failed lock ring close to surface exhibits pitting cavities in un-etched condition: (a) low and (b) high magnifications. 3.5. electron probe micro analyser (epma) 3.5.1. back scattered electron images back scattered electron images obtained from the failed lock ring close to fracture region demonstrates extensive pitting at several locations near the top surface (fig. 8). these features are similar to those observed in optical microscope. this also confirms that the material has undergone pitting corrosion which has initiated at the surface. in addition, the cracks which are originated from the plane surface of its width side have further propagated into the base material along with several branches (fig. 8). low magnification bse image obtained for entire width of the failed lock ring part exhibits abundant number of cracks with multi-branching. these cracks are extended towards inside the material (fig. 9a). magnified microstructures taken from three different regions of fig. 9a clearly indicate that the cracks have propagated arbitrarily into different directions and formed tree like branching (fig. 9 b-d). as a result, part of the base material has also dislodged from the affected area. blade lock ring of 4 th stage compressor rotor: failure investigation 90 figure. 8: epma-bse image at crack tip of the failed lock ring. figure. 9: epma-bse images: (a) low magnified image for entire width of failed ring, (b), (c) and (d) magnified images obtained from different region of (a). rao and singh (2019): international journal of engineering materials and manufacture, 4(3), 85-95 91 3.5.2. x-ray elemental distribution mappings bse image of failed lock ring exhibits the presence of both the elongated as well as globular inclusions. in order to identify the type and its morphology, x-ray elemental distribution mappings are obtained at three different regions and shown in figs. 10-12. the base material reveals elongated manganese sulphide inclusions (fig. 10). these mns inclusions are elongated along the rolling direction and are located as bunch of inclusions within the area of about 200  200 µm2 area. another set of x-ray elemental distribution mappings has been taken from the region wherein both the elongated and globular inclusions are present. these mappings reveal the enrichment of o, al and mn, s elements, respectively (fig. 11). this reflects that the mns and al2o3 types of inclusions are predominantly present in the material. x-ray mappings are also gathered from the region wherein both the types of inclusions are imbedded as single identity. it clearly illustrates that globular oxide inclusion is encapsulated with elongated mns (fig. 12). the mns inclusion is elongated and located at the periphery of the al2o3. epma analysis shows that the parent material used for lock ring contains predominantly mns as well as al2o3 types of inclusions. figure. 10: epma x-ray elemental distribution mappings of the elements mn, s, o and al. blade lock ring of 4 th stage compressor rotor: failure investigation 92 figure. 11: epma x-ray elemental distribution mappings of the elements mn, s, o, si and al. rao and singh (2019): international journal of engineering materials and manufacture, 4(3), 85-95 93 figure. 12: epma x-ray elemental distribution mappings of the elements mn, s, o, si and al. 3.6. chemical composition and hardness the chemical composition of the lock ring obtained by icp-oes technique is given in table 1. the interstitial elements c and s are also included in table 1. the chemical composition of the lock ring is similar to that of the martensitic stainless steel (aisi 422) [3]. the hardness value of the failed lock ring is 390 ± 5 vhn30. blade lock ring of 4 th stage compressor rotor: failure investigation 94 table 1: chemical composition of the lock ring element c s ni cr mn mo v w fe wt. % 0.105 0.009 1.66 10.78 0.4 0.39 0.21 1.75 balance 4. discussions chemical composition of the lock ring sample suggests that it is made up of martensitic stainless steel. the analysed composition is nearly equivalent to aisi 422 grade. alloy aisi 422 is a hardenable stainless steel designed for use up to 649 c. the properties can be optimized through heat treatment (hardening and tempering). as this material is resistance to scaling and oxidation and also having high strength, it is a potential candidate for fabricating aircraft components [3-4]. both the microstructure and hardness indicate that the lock ring material is in hardened and tempered condition. the failed lock ring contains a large amount of non-metallic inclusions with three distinct shapes. these are elongated (mns), globular (al2o3) and a complex shape wherein al2o3 is embedded with mns called as oxysulphide. it is to be noted that these inclusions are not permitted for aerospace applications, as they reduce the mechanical properties and corrosion resistance of the material. the surface of the lock ring has suffered severe pitting corrosion as evidenced by metallography and epma studies. several branching cracks are found propagating from the corrosion pits into the material which point towards the occurrence of stress-corrosion cracking (scc). dark contrast with mud cracks on 75% of the fracture surface reflects that these cracks were open to corrosion environment during service. the eds results also confirm the same. sem micrograph of the fracture surface exhibits extensive mud-cracks which has masked the most of the fracture features (fig.4 b). these mud-cracks are the characteristics of drying out of hydrated, probably gel-like deposits. hence, mud-cracks are typically termed as corrosion debris. in addition mud-crack pattern can usually be seen on fracture surfaces caused by scc and sem fractography study is required to see the mud-crack pattern in most cases [5]. the fracture region close to mating surface of pre-existing crack and newly formed crack reveals cleavage facets (fig. 4 c and d). this indicates that the material has failed in brittle manner. interestingly, cleavage mode of brittle fracture feature is one of the characteristic of scc [6]. as reported by truhan et al., a very close relationship exists between stress corrosion cracking and pitting [7]. it is known that stainless steel forms chromium oxide passive film to protect from environmental corrosion. as a result, the components made up of stainless steel material are less susceptible to corrosion during service [8]. however, if the passive film damages or breaks due to other service / environmental conditions, then it lead to the creation of local anodes surrounded by relatively large cathodic areas of matrix material and pitting results. in addition, the areas which are formed as anodic to act as initiator for pitting have been identified as metal carbides, sulphide inclusion, grain boundaries and deformed material. more likely processes for premature passive film breakdown are: (i) mechanical breakdown of the passive film, (ii) chloride adsorption to change the conductivity properties of the film and (iii) preferential dissolution of certain precipitates / sulphides [7]. once localized breakdown of the passive film occurs, these small discontinuities acts as relatively anodic and then these areas become prone to pitting. pitting corrosion is therefore, an electrochemical oxidation-reduction process, which occurs within localized deeps on the surface of metals coated with a passive film [9]. the corresponding anodic reaction inside the pit is given below. fe = fe 2+ + 2e (dissolution of iron) (1) these pits cause failure through perforation (a small hole or row of small holes) and engender stress corrosion cracks. subsequently, the life cycles of stainless alloy components decrease [9]. stress corrosion cracking (scc) may initiate at the base of corrosion pits and then propagate inside the material [5 and 10]. the scc cracking may be defined as the delayed failure of alloys by cracking when exposed to certain environments in the presence of a static / residual tensile stress [6]. scc is the cracking induced from the combined influence of tensile stress and a corrosive medium. as the lock ring is utilized to lock the blades in 4 th stage compressor rotor, it has been subjected to continuous tensile stress during operation. in addition, the environmental condition during operation/service might have provoked to initiate stress corrosion. thus the failed lock ring exhibits several tree like branched cracks which have been initiated from surface and then propagated inside the material. this has subsequently broken the lock ring into two pieces. similar type of tree branched cracks have been observed for the stainless steel material failed due to stress corrosion cracking [11]. the scc frequently initiates at pre-existing feature. it includes groves, laps, burs and / or stress concentrated sharp corners etc. [12]. in addition, the scc can also initiate at pits that are formed during exposure to service environment. pits can form at inclusions that intersect the free surface. secondary phases, like mns inclusions act as crack initiation sites by promoting localized corrosion of the material [13]. it is also reported that sulphide inclusions act as anodic relative to the surrounding sulphur free matrix [13]. thus, mns inclusion decreases the pitting resistance of the material. frankel has also stated that the pits in stainless steels are often associated with rao and singh (2019): international journal of engineering materials and manufacture, 4(3), 85-95 95 mns inclusions [14]. once the crack reaches a critical crack length, it continues to propagate the metal and the reminder of the fracture surface fails. it is also reported by liu et al. that the pitting corrosion occurs preferentially around the al2o3 inclusions. as al2o3 inclusions are stable and hard, during the process of corrosion, these inclusions do not dissolve like mns [15]. therefore, pitting corrosion is induced at the interface of the inclusions and the steel matrix and then results in micro cracks. as the corrosion progressed, the size of the micro-crack becomes larger and accordingly cracks progress inside the material. both the elongated mns and globular al2o3 inclusions aggravate the stress concentration sites to initiate the scc. the oxy-sulphide inclusion observed in epma mapping has been reported in stainless steel by grajcar et al. [16]. these inclusions also act as preferential sites for pit formation and corrosion pitting and nucleate at the interface between inclusion and matrix. present results have therefore pointed towards that the lock ring has initially suffered pitting corrosion in service and then cracks have propagated inside the material by stress corrosion cracking. this has introduced premature failure of lock ring during service. 5. conclusions this research showed the followings. 1. lock ring has suffered with pre-existing cracks up to 3/4th of the thickness during service. 2. complex type (oxy-sulphide) inclusions have changed the local crack-tip chemistry and acted as preferential sites for nucleation of pits at the interface between inclusions and matrix. 3. crack with tree like multi-branching observed in failed lock ring is a key characteristic of stress corrosion cracking. 4. the lock ring has finally failed due to stress corrosion cracking that has initiated due to pitting corrosion. acknowledgements authors acknowledge defence research and development organisation for financial support. we are grateful to dr vikas kumar, director, defence metallurgical research laboratory for his kind encouragement. authors thank members of emg, mag, photography and radiography groups of dmrl for their kind help during investigation. references 1. mallikarjuna, v., kishore, g. k. and reddy, b. r. b. (2013). fatigue analysis and design of different compressor rotor blade of an orpheus engine, international journal of advanced research in engineering and applied sciences, 2(9), 40-55. 2. andeson, c. r. and tomeo, p. v. (2014). gas turbine engine fan blade lock assembly, u s patent us2014/0133991 a1. 3. hamilton, m. l., huang, f. h.and hu, w. (1992). mechanical properties of martensitic allot aisi 422, presented at the 16 th astm international conference on radiation effect on materials, denver, colorado. 4. stainless steel 422 / s42200 / 1.4935 / 616, http://4.imimg.com/data4/kg/vi/my-626992/stainless-steel-422round-bar.pdf. 5. brown, b. f. (1977). stress corrosion cracking control measures, national bureau of standards monograph 156. 6. chatterjee, u. k. (1995).stress corrosion cracking and component failure: causes and prevention, sadhana, 20(1), 165-184. 7. truhan, j.j., jr. and hehemann, r.f. (1977). surface aspects of pitting and stress corrosion cracking, case western reserve university, cleveland, ohio, prepared by national aeronautics and space administration nasa lewis research centre, grant ngr 36-027-051. 8. leffler, b. (1998). stainless-stainless steels and their properties. chapter 3. 2nd edition. 9. bensalah, n. (2012). pitting corrosion. chapter 7, corrosive effects of chlorides on metals, fong-yuan ma. chaina. 10. roberge, p.r. (2012). handbook of corrosion engineering, mcgraw-hill, new york san francisco, chapter 5, corrosion failure, 332. 11. aly, o.f. and neto, m.m. (2013). stress corrosion cracking, chapter 4, developments in corrosion protection, ed. m aliofkhazraei, intech open publishers, 65-79. http://dx.doi.org/10.5772/57349 12. jones, r. h. (2017). stress-corrosion cracking, materials performance and evaluation, second edition, chapter 1, mechanism of stress-corrosion cracking, asm international. 13. gulbrandsen, s. (2012). stress corrosion cracking of 316l austenitic stainless steel in high temperature ethanol/water environments, thesis on degree master of science in the school of materials science and engineering, georgia institute of technology. 14. frankel, g. s. (1998). pitting corrosion of metals a review of the critical factors, journal of the electrochemical society, 145(6), 2186-2198. doi: 10.1149/1.1838615 15. liu, q., yang, s., zhao, m., zhu, l. and li, j. (2017). pitting corrosion of steel induced by al2o3 inclusions, metals, 7(247), 1-12. doi:10.3390/met7090347. 16. grajcar, a. and plachciñska, a. (2016).effect of sulphide inclusions on the pitting-corrosion behaviour of highmn steels in chloride and alkaline solutions, materials and technology 50 (5), 713–718. doi: 10.17222/mit.2015.169 http://4.imimg.com/data4/kg/vi/my-626992/stainless-steel-422-round-bar.pdf http://4.imimg.com/data4/kg/vi/my-626992/stainless-steel-422-round-bar.pdf international journal of engineering materials and manufacture (2019) 4(1) 15-21 https://doi.org/10.26776/ijemm.04.01.2019.02 y. m. akib 1 , a. kabir 2 , and m. hasan 3 1 department of industrial and production engineering rajshahi university of engineering and technology (ruet) rajshahi-6204, bangladesh 2 department of mechanical engineering bangladesh university of engineering and technology (buet) dhaka, bangladesh 3 department of mechanical engineering north carolina a&t state university, greensboro, nc 27401, usa e-mail: mhasan2@aggies.ncat.edu reference: akib, y. m., kabir, a. and hasan, m. (2019). critical assessment of altitude adaptive dual bell nozzle using computational fluid dynamic. international journal of engineering materials and manufacture, 4(1), 15-21. critical assessment of altitude adaptive dual bell nozzle using computational fluid dynamics yeasir mohammad akib, asif kabir, and mahdi hasan received: 04 october 2018 accepted: 30 december 2018 published: 01 march 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract space exploration and space tourism have now become a raging competition among the developed nations. for this reason, different types of advanced rocket nozzles with prospective privileges are introduced. altitude adaptive dual bell nozzle will soon replace the conventional nozzles for the first stage rocket launcher. indeed, this nozzle has auto adaption capability based on altitude. the major feature of a dual bell nozzle is the two bell-shaped contours separated by an inflection point. this nozzle has left rooms for researchers to test different flight conditions and transition characteristics. in this paper, a dual bell nozzle contour has been developed in matlab and analysed for different thermodynamic parameters. ansys fluent is used in analysing flow through the nozzle. shadowgraph imaging technique is used for measuring density gradient and compared it with fluent results. the simulations were performed by using the k-epsilon turbulence model. keywords: altitude adaption, dual bell nozzle, supersonic flow, inflection point, ansys fluent 1 introduction recently dual bell nozzle has been unearthed to be one of the most undertaking concepts. plug nozzles, either linear or axisymmetric, nozzles with extendable exit cones (eec), and dual-bell nozzles are presently under consideration by space industries and agencies as possible main engine candidates for future launchers [1, 2]. currently, several research organizations (nasa, onera, etc.) and aviation and space industries (boeing, snecma motors, dassault, etc.) are working on the improvement of the performances and reliability of the supersonic rocket engine nozzles and space launchers nozzles [3]. the dual-bell concept was first initiated in literature in 1949 by f. cowles and c. foster, and was patented in the 1960s by rocketdyne [4]. in 1994, tests at rocketdyne conducted by horn and fisher and in europe by the future european space transportation investigations program (festip) at the european space agency (esa) investigated the influence of the extension contour geometry on the flow behavior in the first experimental study and confirmed the feasibility of this nozzle design [4]. horn and fisher found that a dual-bell nozzle could provide enough thrust to carry 12.1% more payload than a conventional nozzle of the same area ratio [4]. since the early nineties, many studies, mostly numerical, have been made by goel and jensen [5], immich and caporicci [6] (within the festip program) to understand and attempted to predict the behavior of this new nozzle concept. a numerical study of the feasibility was made by karl and hagemann [7]. p. goel and r. jensen performed the first numerical analysis of dualbell nozzles, which was published in 1995 [8]. throughout the 2000s, several numerical and experimental studies of dual-bell nozzles were conducted in the united states and europe [2]. critical assessment of altitude adaptive dual bell nozzle using computational fluid dynamics 16 a dual-bell nozzle has an inner base nozzle contour, a wall inflection, and an outer extension nozzle contour (figure 1, left). this nozzle provides two stable operation modes. at low altitude, the high ambient pressure forces the flow to separate at the inflection (figure 1, upper right) and at high altitude mode (figure 1, lower right): the extension is flowing full, offering a large area ratio for improved altitude performances and this area ratio limitation of conventional nozzles is circumvented for an overall performance gain [9]. 2 methodology at first, a full-length dual-bell nozzle contour is created using matlab. then the meshing part is completed using ansys. for the analysis of this model fluent software is used. along the nozzle flow behaviour is obtained. for the nozzle, air is taken as a working medium. using the isentropic flow relations, area ratio of the dual-bell nozzle was determined. due to the large assumed pressure and the high temperatures, the value of the ratio of specific heats was assumed to be 1.23. 2.1 contour design dual bell nozzle is defined by three section: converging part, throat and diverging part. converging section and throat is designed using two circle equation having two different radii (figure 2). this nozzle has two parts in its diverging section. the first part is known as the base or primary nozzle. the second bell (figure 3) starts with a slope angle higher than the first bell end, such to yield an attached flow with a centred expansion at the inflection point in under expanded regime and a separated flow in the second bell in strong over expanded regime [13]. a b figure 1: (a) dual-bell nozzle (b) two operating modes: sea level (top) and altitude mode (bottom) [2] figure 2: dual bell nozzle (up to the first bell) [10] akib, kabir and hasan (2019): international journal of engineering materials and manufacture, 4(1), 15-21 17 figure 3: dual bell nozzle with labeled section [11] the first parabola length of the nozzle is determined by 𝐿𝑛 = 𝐾(√𝜀−1)𝑅𝑡 tan(𝜃𝑒) (1) where k is a percentage of the length of an equivalent 15% conical nozzle, ε is nozzle exit ratio, rt is the throat radius, θe is nozzle exit angle. a coordinate system is defined with the axial (x) axis and the radial (y) axis centred at the throat in order to define the nozzle further. the first and second curves define the entrance and exit of the throat of the nozzle and are based on circular curves. the third curve is a parabola. the equation of first parabola dual-bell is 𝑥 = 𝑎𝑦2 + 𝑏𝑦 + 𝑐 (2) the coefficients a, b and c are determined by the derivatives of the contour at the point where the circle from the throat meets the beginning of the parabola xn, and the length of the nozzle ln where the definition of xn is 𝑥𝑁 = 𝑎𝑅𝑁 2 + 𝑏𝑅𝑁 + 𝑐 (3) respectably the slope of xn and slope at the exit is 𝑑𝑦 𝑑𝑥 = tan(𝜃𝑁) = 1 2𝑎𝑅𝑁+𝑏 (4) 𝑑𝑦 𝑑𝑥 = tan(𝜃𝑒) = 1 2𝑎𝑅𝑒+𝑏 (5) in matrix form, a full system of equations for the parabolic coefficients for the first parabola is [ 2𝑅𝑁 1 0 2𝑅𝑒 1 0 𝑅𝑁 2 𝑅𝑁 1 ] [ 𝑎 𝑏 𝑐 ] = [ 1 tan(𝜃𝑁) 1 tan(𝜃𝑒) 𝑥𝑁 ] (6) full length of dual-bell nozzle is determined by 𝐿𝑀 = 𝐾𝑀(√𝜀−1)𝑅𝑡 tan(𝜃𝑒) (7) similarly, a full system of equations for the second parabola of the dual-bell nozzle [ 2𝑅𝑀 1 0 2𝑅𝑒 1 0 𝑅𝑁 2 𝑅𝑁 1 ] [ 𝑎′ 𝑏′ 𝑐′ ] = [ 1 tan(𝜃𝑀) 1 tan(𝜃𝑒) 𝑥𝑀 ] (8) where a’, b’ and c’ are the coefficients of the second curve. the final design parameters are listed in table 1. critical assessment of altitude adaptive dual bell nozzle using computational fluid dynamics 18 firstly, dual bell nozzle contour has developed in matlab using the above equation. then the meshing part is completed using ansys fluent. a grid independent study was performed (figure 4) by solving the governing equations for different grid densities ranging from 28,000 – 100,000 elements. the flow parameters at the nozzle exit for pressure ratio (pr) =50 show that the maximum difference between the results of the 48,000 and 100,00 portion solver type was selected as density based, time was steady and 2d space was selected as axisymmetric. hybrid initialization was selected as solution initialization and the data was computed from the pressure inlet. after running calculation, taking 3000 number of iteration, the isentropic parameter was calculated. 3 results and discussions 3.1 total pressure for both pressure ratio, 50 and 100, total pressure at the inlet is very high. total pressure decreases slightly along the nozzle length but drops significantly from the midpoint of the second curve and becomes lowest at the exit. total pressure varies from 17.5 kpa to 0.73 kpa at the exit region. figure 5 exhibits the pressure variations across the nozzle for the two different pressure ratios. 3.2 total temperature total temperature variations along the nozzle length is shown below in figure 6. from the figures, the total temperature seems high from the starting point of the second curvature for both pressure ratios. after that, through the axial distance, temperature varies significantly. there is a slight variation in total temperature at the nozzle exit for the pressure ratios 50 and 100 .the temperature varies from 101-107 k as the exit gas meets the air at the exit portion. 3.3 velocity vector velocity vector for pressure ratios 50 and 100 are shown in figure 7. velocity vectors show the change of mach numbers along the nozzle geometry. for both the pressure ratio 50 and 100, velocity vector increases to become supersonic inside the nozzle and later decreases down to subsonic at the exit. this drastic decrement in velocity vector occurs after the second diverging section. for pr 100, the mach velocity vector becomes slightly lower than pr 50. table 1: parabolic coefficients of the dual-bell nozzle parabolic coefficients dual-bell nozzle (first contour) dual-bell nozzle (second contour) a 10.2859 21.8315 b 0.5084 -4.7223 c -0.0208 0.5362 table 2: design parameters for the dual-bell nozzle length (m) theta_n (degrees) theta_e (degrees) area ratio 0.2732 20 9.588 64.5603 figure 4: grid independence test static temperature vs. axial position 0 20 40 60 80 100 120 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 s t a t i c t e m p e r a t u r e ( k ) axial postion (m) 28k 48k 100k akib, kabir and hasan (2019): international journal of engineering materials and manufacture, 4(1), 15-21 19 a b figure 5: contour of total pressure for pressure ratio 50 (a) and 100 (b) a b figure 6: contour of total temperature for pressure ratio 50 (a) and 100 (b) a b figure 7: contour of mach velocity vector for pressure ratio 50 (a) and 100 (b) critical assessment of altitude adaptive dual bell nozzle using computational fluid dynamics 20 3.4 mach number mach number is subsonic at the inlet for both pressure ratio 50 and 100. flow becomes supersonic and slightly hypersonic at the starting of the second diverging section. there are some variations of mach number at the exit. at the midpoint of the second diverging section, pr 100 shows more variation of mach number than pr 50. 3.5 shadowgraph visualization numerical shadowgraph or schlieren image was generated by contour plotting the absolute value of the density gradient using tecplot. the numerical shadowgraph did not distinguish between shocks or expansions since the absolute value was used. figure 10 shows the mach number at specific positions of the nozzle for different pressure ratio. in the graph the yellow line represents the theoretical mach number calculated from isentropic flow relation. for more consistency, our results are compared with numerical data at three different positions calculating by the ref [12] only for mach number. at throat and exit position, as the pressure ratio increases mach number remains nearly same for both our own result and referred one. it can be noticed that at the inflection point, there is a little discrepancy in between that two numerical results. 4 conclusions a critical assessment of dual-bell nozzles was presented in this paper. this paper represents the design of a dual-bell nozzle contour and the study of the fluid parameters behaviour like pressure, temperature, mach number, velocity vector etc. but in future studies, there are some aspects that may be studied. the present study was conducted only for four different pressure ratios. future study may examine to perform some experimental works by using same input parameters to compare with the numerical data for validation. a b figure 8: contour of mach number for pressure ratio 50 (a) and 100 (b) a b figure 9: schlieren image or shadowgraph for pressure ratio 50 (a) and 100 (b) akib, kabir and hasan (2019): international journal of engineering materials and manufacture, 4(1), 15-21 21 figure 10: mach number at different nozzle position (along with centre line) for four different pressure ratios references 1. muss, j., nhuyen, t., reske, e., mcdaniels, d., muss, j., nhuyen, t., reske, e. & mcdaniels, d. (1997, july). evaluation of altitude compensating nozzle concepts for rlv. in 33rd joint propulsion conference and exhibit (p. 3222). 2. hagemann, g., immich, h., nguyen, t. v., & dumnov, g. e. (1998). advanced rocket nozzles. journal of propulsion and power, 14(5), 620-634. 3. kbab, h., sellam, m., hamitouche, t., bergheul, s., & lagab, l. (2017). design and performance evaluation of a dual bell nozzle. acta astronautica, 130, 52-59. 4. horn, m., & fisher, s. (1993). dual-bell altitude compensating nozzles. nasa propulsion engineering research center, 140-147. 5. goel, p., & jensen, r. (1995). numerical analysis of the performance of altitude compensating dual bell nozzle flows. in rockwell international corp, 32nd jannaf combustion subcommittee meeting and propulsion engineering research centre 7th annual symposium p 117-140 (see n 96-27892 10-20). 6. immich, h., & caporicci, m. (1997). festip technology developments in liquid rocket propulsion for reusable launch vehicles. in 32nd joint propulsion conference and exhibit (p. 3113). 7. kronmüller, h., schäfer, k., stark, r., & zimmermann, h. (2002). kaltgas-höhensimulationsprüfstand p6. 2 des dlr lampoldshausen. 8. frey, m., & hagemann, g. (1999). critical assessment of dual-bell nozzles. journal of propulsion and power, 15(1), 137-143. 9. genin, c., stark, r., karl, s., & schneider, d. (2012, july). numerical investigation of dual bell nozzle flow field. in 48th aiaa/asme/sae/asee joint propulsion conference & exhibit (p. 4164). 10. kulhanek, s. l. (2012). design, analysis, and simulation of rocket propulsion system (doctoral dissertation, university of kansas). 11. akib, y. m., kabir, a., & hasan, m. (2017). characteristics analysis of dual bell nozzle using computational fluid dynamics. in 3rd international conference on mechanical industrial and materials engineering (icmime), 2017. fluid mechanics, fm-76. 12. davis, k., fortner, e., heard, m., mccallum, h., & putzke, h. (2015). experimental and computational investigation of a dual-bell nozzle. in 53rd aiaa aerospace sciences meeting (p. 0377). 0 1 2 3 4 5 6 0 20 40 60 80 100 120 m a c h n u m b e r pressure ratio oc @throat ref[12] @throat oc @inflection ref[12] @inflection oc @exit ref[12] @exit calculated mach *oc = own creation international journal of engineering materials and manufacture (2018) 3(2) 113-121 https://doi.org/10.26776/ijemm.03.02.2018.06 n. hasan1 , a. o. rahman2 and m. s. alam3 1petroleum and chemical engineering programme, faculty of engineering universiti teknologi brunei, jalan tungku link, gadong be 1410, brunei darussalam e-mail: nurulhasan@asme.org 2faculty of engineering, deakin university, geelong, victoria 3220, australia e-mail: aorahman@deakin.edu.au 3department of civil engineering, university of bahrain, po box 32038, sakheer, kingdom of bahrain e-mail: malam@uob.edu.bh reference: hasan, n., rahman, a. o., and alam, m. s. (2018). validation and verification of cfd prediction of fluid flow of a submerged vertical round jet. international journal of engineering materials and manufacture, 3(2), 113-121. validation and verification of cfd prediction of fluid flow of a submerged vertical round jet nurul hasan1, ahmed oliur rahman2 and md. shah alam3 received: 27 may 2018 accepted: 08 june 2018 published: 30 june 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract verification and validation are the main two vital items to consider a cfd simulation project. in the proposed research article these steps are applied for a vertical round submerged jet into a cylindrical bath. an axisymmetric domain minimized the computational cost as the navier-stokes equation is simplified and a finite volume method (fvm) is used to solve continue and momentum equation using commercial computational fluid dynamics, cfd (fluent) software. verification refers to solving equation right, and a step-by-step grid independence tests were performed. for validation, experimental data was produced under the same arc funding using laser doppler velocimetry (ldv). among the turbulence model, sst was found to predict the flow behavior better than k -ε realization or rsm models. keywords: turbulent flow, submerged jet, validation of cfd, verification of cfd list of symbol/abbreviation re j jet reynolds no cd cylinder diameter (m) ch cylinder height (m) 0d jet diameter (m) h water level (m) rsm reynold stress model 1 introducion numerous papers are published without a strategic verification and without coordinating with the experimentalists. so in many cases the mesh in cfd is not optimized. on the other hand, the published experimental data are not well-analyzed or well-presented. the boundary conditions for the cfd do not always represent the total physics. there are difficulties for any experimental data to produce; not the same way there are problems in all the turbulence models of cfd. a receiving bath when receives a submerged jet [1,2], the fluid decelerates and spreads, and this process continues as it entrains the surrounded liquid. to uniform the turbulence intensity and effect on the receiving bath, a honeycomb [3] can be used. this might also suppress a possible swirl [4] which can be ignored for practical purpose. the cfd [5-7] investigations performed previously in this area were without any proper verification of the solution, the computational central line velocity can be plotted against the experimental data at the same location. one of validation and verification of cfd prediction of fluid flow of a submerged vertical round jet 114 the best set of data is available from bayly et al. [8]. without verification, previous authors have performed an investigation, e.g., a mesh of 54x44 [8] is not enough as shown in the current investigation. a large number of studies is not justified in any cfd investigation performed by devahastin and mujumdar [9]. also, the cfd needs to be verified systematically for laminar and turbulence flow separately and independently [10]. the unnecessarily fined mesh could lead a wrong conclusion. the very wrong approach to validate cfd results without satisfying the verification requirement. this is not a crude practice. it may be the case that the researchers are using more or less mesh than it requires. for example, wilson and imber [11] studied a computational model of a rectangular jet ( 0 0re lj l d u ρ µ = =1.49x105) with aspect ratio 10. it would be interesting to investigate the effect of doubling the mesh of wilson and imber [11]. this investigation could be helpful for more applied pipeline oil flow under the sea [12] or under the ground [13]. the approach used by devahastin and mujumdar [9] would force the researchers to cause unnecessary wastes of computing resources (by running longer time for low reynolds number). this approach is not followed here. rather, each case has been checked for grid independence. here in the research: next section defines the computational physics, followed by experimental setup and computational models, results are presented with verification and validation. the conclusions are added next. presenting the grid independence behavior offers more satisfaction [14]. the mixing zone analysis needs the outcome of a submerged jet [15]. when the free surface is involved like in an in an impinging jet, the flow becomes more complex [16]. the heated flow the validation process is very complicated as the experimental process has limitations as in these cases [17, 18]. for a bigger domain [19], the experimental data is not easy to collect. for simplicity, the oscillation or fluctuation [20] is not considered which did introduce error. all kind of absorption [21, 22] of air is neglected for simplicity. 2 computational physics an axisymmetric geometry is considered which represent the cylindrical receiving bath of 500 mm long ( c h ) with a diameter ( cd ) of 90 mm (figure 1). at the center of the cylinder from the top roof the nozzle comes vertically down and the tip of the nozzle is 355 mm above the base or 145 mm below the top of the cylinder wall, only 145 mm is inside the receiving cylindrical bath (the rest 55 mm is not shown). concerning figure 1, outlet pipe the jet is located 0≤ r ≤6 and cylinder is located at -145≤ x ≤355 mm and 0≤ r ≤45 mm, and inlet jet is defined as 0≤ r ≤4.8 mm for the inlet jet, 355mm≤ x ≤555 mm and mm for the outlet pipe in the bottom. an inlet boundary condition was set at nozzle inlet, and this is 200 mm of length. an outlet pipe bc was used at the domain outlet. the tip of the exit pipe is 200 mm below the base. the mass flow rate of the inlet a outlet are kept same so there is no rise of liquid air surface level while running the experimental or computation test. it was easier to set a no accumulation zone; however, experimentally its was nearly hard. the circular outlet pipe (figure 1) will not be shown in the rest of the figures of this paper. 3 experimental setup for the submerged liquid jet, laser doppler velocimetry (ldv) data were taken to validate the computational results of the primary flow. a schematic diagram of the experimental arrangement is shown in figure 2. the major equipment consists is a cylindrical receiving bath ( cd =90 mm, ch =500 mm), a nozzle ( 0d =9.6 mm), a reservoir tank, a pump to recirculate the water. the size of the nozzle, the receiving cylinder, and the outlet are identical to those in computational models. the level of water in the cylinder is kept constant by controlling the flow. for a 100 mm nozzle submergence depth, there was no significant oscillation in the free liquid surface in the cylindrical bath. so for a 100 mm of h , the free surface was considered as a wall (with zero shear stress) in the computational models. in the experiments, even though efforts were made to keep a ‘no accumulation’ of water in the cylindrical bath, in reality, it was not strictly possible. this minor variation was unfavorable. the liquid in the bath was stationary before switching on liquid jet both for the computational techniques and for experimentations. 4 computational models continuity, momentum equations along with ε−k realizable [23], rsm [24, 25], and sst [26] turbulence models were used to solve the fluid flow by an sj. the detail verification of grid refinement is presented in the results section. the level of convergence was of the order of 10-6. consistency higher order discretizations and pressurevelocity coupling [27] were used in all cases studied. the computational modeling parameters were determined after verification [28] and validations [29]. hasan, rahman, and alam (2018): international journal of engineering materials and manufacture, 3(2) 113-121 115 figure 1: a schematic diagram of the computational domain of the submerged liquid jet apparatus with the boundary conditions [ ind =9.6 mm, cd =90 mm, lh =455 mm, ch =500 mm, h =100 mm, outlet nozzle, 0utd =12 mm]. figure 2: experimental set up of the submerged liquid jet validation and verification of cfd prediction of fluid flow of a submerged vertical round jet 116 5 results and discussions using refinement as presented in this section ensures the less grid dependence solution. all the turbulence parameters (turbulent kinetic energy k , turbulent intensity ( 2 3 /k u ), turbulent dissipation rate,ε ) and primary flow parameters (velocity) are examined for this purpose as the refinement performed, even though a few are presented here. figure 3 presents a typical case where the center line velocity magnitude (m/s) (left-hand side) and center line turbulence kinetic energy ( k ) (right-hand side) have been plotted against nondimensional distance from the nozzle ( / cx d ) for four quadrilateral meshes (mesh0=32,550, mesh1=40,100, mesh2=43,875, mesh3=54,000). in both these cases, it is clearly shown that on mesh3, the solution parameters have reached their asymptotic levels. even mesh2 and mesh1 are fine enough to predict the velocity and turbulent kinetic energy. the mesh density is higher near the nozzle region compared to the rest of the domain to capture the sharp gradient of solution parameters. figure 3 (left) shows that at about 0.75-1.25 of / cx d , the center line velocity is most sensitive to the choice of grid size. it is repeatedly found in many cfd papers that the authors check only one parameter (especially velocity components) as the refinement continues; however, figure 3 (right-hand side) show that the turbulent kinetic energy does not behave the same way as the velocity magnitude (left-hand side of figure 3). the peak kinetic turbulent energy is at 1.0 / cx d (right-hand side of figure 3) and k is very sensitive in the (0.60-1.10) / cx d region. sensitivity of turbulence intensity (left hand side, figure 4), turbulent dissipation rate (right hand side, figure 5), rate of change of axial velocity in the axial direction (left hand side, figure 5) and strain rate (right hand side, figure 5) with the four meshes considered are presented. figure 3: center line velocity magnitude (m/s) and turbulent kinetic energy for four different meshes [ qv =12 liter/min, symbols are shown in figure 1]. hasan, rahman, and alam (2018): international journal of engineering materials and manufacture, 3(2) 113-121 117 figure 4: left: center line turbulent intensity, right turbulent dissipation rate for three different meshes [ qv =12 liter/min]. the turbulent intensity (left-hand side of figure 4) is more sensitive at the inlet ( / cx d =0.50-1.0), whereas the turbulent dissipation rate (figure 4, right) has a similar pattern to the turbulent kinetic energy (figure 3, right). it should be noted that the inlet liquid jet is 40 times in length the nozzle radius for all the results presented. hence when the liquid jet exits to the cylindrical bath ( / cx d =0.0), the flow is fully developed. at the inlet, the turbulent intensity ( 02 3 * 100k u ) was set 10%, and after flowing 200 mm ( nl of figure 1), at the nozzle exit ( / cx d =0.0) to the receiving bath, the developed turbulent intensity is ~11% as found in figure 4 (left-hand side). the rate of change of solution parameters is more sensitive to grid size as shown figure 5. the left of figure 5 shows that rate of change of axial velocity along an axial direction, which suggests that /du dx is more sensitive than the corresponding velocity (left-hand side of figure 3). however, solutions on mesh3 have reached the asymptotic level (figure 3, figure 4 and figure 5). the center line strain rate (right of figure 5) is even more sensitive on mesh size, however, again found that the strain rate of the centre line on mesh3 (right-hand side of figure 5) is less dependent on the mesh. in fact, solution on mesh2 is fine enough to predict the center line solution parameters. validation and verification of cfd prediction of fluid flow of a submerged vertical round jet 118 figure 5: left: center line axial velocity gradient ( dxdu / ), right: center line strain rate for three different meshes [ qv =12 liter/min]. the verification of the dependence of solution parameters on grid size in the center line does not guarantee that the solution is independent of the grid in the rest of the domain. the variations of two solution parameters, e.g., axial velocity and turbulent kinetic energy at 100 mm ( / cx d =1.11) down from the nozzle along the non-dimensional radial direction ( crr / ) are shown in figure 6, left and right, respectively. figure 6 shows that up to crr / =0.18, both the axial velocity and turbulent kinetic energy are sensitive to grid size. however, the mesh3 solution does not significantly differ from the solution on mesh2. where the gradient of solution parameters is higher, the solution parameters (velocity, turbulent kinetic energy, turbulent intensity, turbulent dissipation rate, etc) are more sensitive to mesh size compared to the rest of the domain. in all the sections presented next, only mesh2 is used which is less dependent on mesh size as shown in general. the results in figure 6 also indicates that the local refinement is necessary to capture the physics in the core of the jet as concluded by others [30] as well. figure 7 presents the center line mean velocity magnitude (left-hand side) and center line turbulent kinetic energy ( k ) (right-hand side) as a function of dimensionless distance from the nozzle exit ( / cx d ) for k -ε realizable (referred as kerz), rsm and sst turbulence models. the black squares (figure 7) show the experimental data. hasan, rahman, and alam (2018): international journal of engineering materials and manufacture, 3(2) 113-121 119 figure 6: radial variation turbulent kinetic energy (left) and turbulent intensity (right) at 100 mm below the nozzle for three different meshes [ qv =12 liter/min]. the experimental velocity magnitude (left of figure 7) is calculated by the sqrt of 3 velocity components ( )2 2 2x y zv v v+ + . figure 7 (left) shows in terms of velocity magnitude production, both k -ε realizable and rsm are of same accurate for / cx d =1.0-3.0, however, for / cx d <0, rsm is better. sst is the better in predicting the center line velocity. within / cx d =0.8-1.0 and / cx d =2.0-3.0, a higher discrepancy is noticed. the former discrepancy is probably because sst is not very accurate in predicting sharp gradient in velocity. the second discrepancy is due to the bottom exit. the solution is not steady near the exit of the domain. figure 7 (right) shows that in the range of / cx d =0-1.0, k -ε realizable and sst fail to predict the turbulent kinetic energy, whereas the rsm can predict the k better. the experimental turbulent kinetic energy is calculated as ( )2 2 21 2 x y zσ σ σ+ + , where iσ is the root mean square velocity components. next, to the nozzle exit, the higher gradient of velocity (left of figure 6) exists, which may result in high turbulence as can be seen from figure 7 (right). from figure 5, the mean axial velocity is same up to 0.75 cx d , after this, there is a sharp decrease in axial velocity resulting in higher turbulence kinetic energy. it is ongoing on how to calculate the experimental turbulent kinetic energy. the non-isentropic experimental yσ compared to xσ is carefully noticed. validation and verification of cfd prediction of fluid flow of a submerged vertical round jet 120 figure 7: computational (solid lines) and experimental (black squares) centre line velocity magnitude (m/s) and turbulence kinetic energy ( k ) [ qv =12 litre/min]. 6 conclusions the step-by-step verification and validation process will remind the researchers how important it is to follow the steps of these processes. forced to consider to an axisymmetric flow, computationally it was cheap, which will serve the purpose of many industrial applications. it was found the sst model predicts the flow field more closely to the experimental data compared to k -ε realizable and rsm . the models developed here could easily be broadened for liquid jets with a definite swirling flow. however, in most cases, the swirling nature is challenging to report from the experimental data. the experimental data could be used to test any cfd code, as shown here. references 1. nawaf h. saeid nh, ali mhbhm. effect of the metallic foam heat sink shape on the mixed convection jet impingement cooling of a horizontal surface (in press). journal of porous media 2017. 2. oosterhuis jp, timmer mag, bühler s, van der meer th, wilcox d. on the performance and flow characteristics of jet pumps with multiple orifices. journal of the acoustical society of america 2016;139:273240. 3. strykowski pj, niccum dl. the influence of velocity and density ratio on the dynamics of spatially developing mixing layers. physics of fluids a: fluid dynamics 1992;4:770-81. 4. yang y, crowe ct, chung jn, troutt tr. experiments on particle dispersion in a plane wake. international journal of multiphase flow 2000;26:1583-607. hasan, rahman, and alam (2018): international journal of engineering materials and manufacture, 3(2) 113-121 121 5. zhong w, yu a, liu x, tong z, zhang h. dem/cfd-dem modelling of non-spherical particulate systems: theoretical developments and applications. powder technology 2016;302:108-52. 6. azpiroz je, hendrix mhw, breugem wp, henkes rawm, editors. cfd modelling of bypass pigs with a deflector disk. bhr group 17th international conference on multiphase technology 2015; 2015. 7. zhalehrajabi e, rahmanian n, hasan n. effects of mesh grid and turbulence models on heat transfer coefficient in a convergent–divergent nozzle. asia‐pacific journal of chemical engineering 2014;9:265–71. 8. bayly ae, rielly cd, evans gm, hazell m, editors. the rate of expansion of a confined, submerged jet. 20th australasian chemical engineering conference, canberra; 1992. 9. devahastin s, mujumdar as. a numerical study of flow and mixing characteristics of laminar confined impinging streams. chemical engineering journal (amsterdam, netherlands) 2002;85:215-23. 10. hosseinalipour sm, mujumdar as. flow and thermal characteristics of steady two dimensional confined laminar opposing jets. part i. equal jets. int commun heat mass 1997;24:27-38. 11. wilson wm, imber rd, editors. cfd analysis of compact, high aspect ratio ejectors. proceedings of asme fedsm; 2001. 12. koh junyi nh. review of the factors that influence the condition of wax deposition in subsea pipelines. international journal of materials and manufacture 2018;3;1:1-8. 13. ishak ma, islam ma, shalaby mr, hasan n. the application of seismic attributes and wheeler transformations for the geomorphological interpretation of stratigraphic surfaces: a case study of the f3 block, dutch offshore sector, north sea. geosciences 2018;8:79. 14. zhalehrajabi e, rahmanian n, hasan n. effects of mesh grid and turbulence models on heat transfer coefficient in a convergent–divergent nozzle. asia‐pacific journal of chemical engineering 2014;9:265-71. 15. hasan n. cfd analysis of the mixing zone for a submerged jet system. asme fluids engineering 2001. 16. khan mn, fletcher c, evans g, he q. cfd modeling of free surface and entrainment of buoyant particles from free surface for submerged jet systems. asme-publications-htd 2001;369:115-20. 17. nurul hasan pw, geoffrey brooks,, nagle m, editors. design of supersonic nozzles for ultra-rapid quenching of metallic vapours. tms annual meeting; 2006. 18. hasan n. cfd modelling of heat transfer in supersonic nozzles for magnesium production. tms journal 2007. 19. naser j, alam f, hasan n, editors. evaluation of a proposed dust ventilation/collection system in an underground mine crushing plant. 16th australasian fluid mechanics conference (afmc); 2007: the university of school of engineering. 20. sern wk, takriff ms, kartom s, kamarudin mzmt, hasan n. numerical simulation of fluid flow behaviour on scale up of oscillatory baffled column. journal of engineering science and technology 2012;7:119-30. 21. harith rashid nh, m. iskandar m. nor. accurate modeling of evaporation and enthalpy of vapor phase in co2 absorption by amine based solution. separation science and technology 2014;49;9:1326-34. 22. rashid h, hasan n, nor m, iskandar m. temperature peak analysis and its effect on absorption column for co2 capture process at different operating conditions. chemical product and process modeling 2014. 23. shih t-h, liou ww, shabbir a, yang z, zhu j. a new k-epsilon eddy viscosity model for high reynolds number turbulent flows. computers and fluids 1995;24:227-38. 24. dupont v, pourkashanian m, williams a, woolley r. the reduction of nitrogen oxide (nox) formation in natural gas burner flames. fuel 1993;72:497-503. 25. henkes rawm, hoogendoorn cj. scaling of the turbulent natural convection flow in a heated square cavity. journal of heat transfer: transactions of the asme 1994;116:400-8. 26. menter fr. two-equation eddy-viscosity turbulence models for engineering applications. aiaa journal 1994;32:1598–605. 27. ferzieger jl, peric m. computational methods for fluid dynamics: springer-verlag, heidelberg.; 1996. 28. roache pj. verification and validation in computational science and engineering. first ed: albuquerque, n.m.: hermosa publishers; 1998. 29. hasan n. cfd studies on fluid-particle interactions on free surface flows. the university of new south wales, 2003. 30. gardin p, brunet m, domgin jf, pericleous k. an experimental and numerical cfd study of turbulence in a tundish container. applied mathematical modelling 2002;26:323-36. references international journal of engineering materials and manufacture (2019) 4(1) 33-40 https://doi.org/10.26776/ijemm.04.01.2019.05 t. s. ogedengbe 1 , p. awe 2 and o.i. joseph 3 department of mechanical and automotive engineering elizade university, ilara-mokin ondo state, nigeria 1 e-mail: temitayo.ogedengbe@elizadeuniversity.edu.ng 2 e-mail: peter.awe@elizadeuniversity.edu.ng 3 e-mail: ojotu.joseph@elizadeuniversity.edu.ng reference: ogedengbe, t.s., awe p. and joseph o.i. (2019). comparative analysis of machining stainless steel using soluble and vegetable oils as cutting fluids, international journal of engineering materials and manufacturing, 4(1), xxx-xxx. comparative analysis of machining stainless steel using soluble and vegetable oils as cutting fluids ogedengbe temitayo samson 1 , awe peter 2 , joseph ojotu ijiwo 3 received: 29 january 2019 accepted: 27 february 2019 published: 01 march 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract in this study, the performance of groundnut oil as an alternate cutting fluid was compared with that of soluble oil during machining of stainless steel. the temperature at the cutting zone, surface roughness and the chip formation were monitored under the two cutting conditions (soluble oil and vegetable oil). the machining parameters used were cutting speed (75 – 135 rev/min), feed rate (0.01 – 0.05 mm 3 /mm) and depth of cut (0.01 – 0.08 mm). the experiment was designed using taguchi orthogonal array of minitab 18 which generated a 9 run machining parameter mix for the experimentation. the physiochemical properties of the various fluids were also analyzed to determine the properties and constituent elements of the cutting fluids. the actual machining of the stainless steel bar was done using a colchester mastiff lathe machine. results show that feed rate and cutting speed had the most significant effect on surface roughness during machining of stainless steel both with groundnut oil and soluble oil. soluble oil was a better coolant but poorer in lubrication as vegetable oil reduced surface roughness more when used. surface roughness value improved from 9.21μm during machining with soluble oil to 3.84μm during machining with groundnut oil which represented a 58.3% improvement. hence, vegetable oil is therefore recommended as good alternative cutting fluid to soluble oil during machining of stainless steel. keywords: energy consumption, machine tools, machining processes, parameters 1 introduction machining is a material removal process used in the industrial sector to produce workpieces with required shape, dimensions, and surface finish [1]. cutting fluid (coolant) is any liquid or gas that is applied to the chip and/or cutting tool to improve cutting performance. a very few cutting operations are performed dry i.e. without the application of cutting fluids. generally, it is essential that cutting fluids be applied to all machining operations. cutting fluids have traditionally been used in machining operations to lubricate the chip-tool, tool-work piece interfaces, remove heat from the work piece and cutting zone, flush away chips from the cutting area, and inhibit corrosion. while each of these four functions can be employed as justification for cutting fluid usage, it is widely believed that the primary functions of a cutting fluid are lubrication and cooling [2]. currently, several types of conventional cutting fluids in used are classified according to their chemical formulation in straight oils and water soluble oils. straight oils or neat oils are non-water-soluble fluids formulated to reduce the friction between the tool and both the chips and work piece. they can be mineral (petroleum based) and animal oil. straight oils have excellent lubrication and corrosion resistance properties however, when inappropriately handled, they may result in skin problems and when cutting fluids evaporate they are distributed as vapor and micro-particles and may lead to breathing problems for the machine operator [3]. disposal of the used cutting fluid is also a major challenge [4]. to cope with these problems, the necessity of using biodegradable fluids has recently been emphasized [5], [6]. and many researchers have carried out different research on the use of vegetable oil as an alternative, vegetable oil is a biodegradable fluid that enhances the cutting performance, extend tool life and improve the surface finish. the effect of vegetable based cutting oil on cutting forces and power has been investigated [7]. results showed that vegetable based cutting oils were better than mailto:temitayo.ogedengbe@elizadeuniversity.edu.ng mailto:peter.awe@elizadeuniversity.edu.ng mailto:ojotu.joseph@elizadeuniversity.edu.ng comparative analysis of machining stainless steel using soluble and vegetable oils as cutting fluids 34 the commercial mineral oil. a review on use of soya bean, rape seed and sunflower oils as a potential cutting fluid has been performed [8]. the three oils were found to be promising alternatives for mineral based oils due to their environmental friendly characteristics. a review on the use of vegetable oil based metal working fluids has been carried out. it was reported that castor, coconut, rapeseed and canola oils have promising future as metal working fluids [9]. a comparative analysis of aisi 1050 steel using n5-soluble oil and arachis oil in metal cutting operation has been carried out [1]. result shows that arachis oil has a better lubricating performance than n5soluble oil. an investigation on the influence of vegetable based cutting fluids on cutting force during milling of aluminum metal matrix composites has been done [10]. their result shows that palm oil suits better than the other vegetable based cutting fluids in terms of minimum cutting force requirement and minimum vibration. the performance of vegetable based oils in drilling austenitic stainless steel has been studied [11]. the effect of six cutting fluids on the tool was investigated by examining tool life, cutting forces and chip formation using a cnc vertical milling center. it was reported that vegetable based oil produced better surface finish than the mineral oil based cutting fluids. efforts have been put into the development of local emulsifiers from local raw materials for cutting fluids [12]. seventeen emulsifiers were prepared and cutting fluids were developed to replace the general mineral oil based cutting fluids used during machining. it was reported that the emulsifier that exhibited maximum reduction of surface tension gave the more stable cutting oil emulsion formulation. mild steel has machined using palm oil and groundnut oil as cutting fluid with performance evaluation done to compare results [13]. results show that palm oil gave the highest thickness of 0.27mm due to its better lubricating property. the effect of use of vegetable-oil based lubricants on chip formation and tool wear in drilling processes has been investigated [14]. result showed that coconut oil gave the best machinability and least wear on the drill bit under same condition with others. a performance evaluation of melon and groundnut oils as metal cutting fluids has been carried out [15]. the cooling ability of the fluids were investigated while machining carbon steel through a close observation of the surface finish and the chip shape formed. it was reported that the use of melon oil resulted in the production of ductile and continuous chips. however, not much work has been done to compare the effect of semi synthetic oils and vegetable based oils on surface roughness and cutting temperature especially when machining stainless steel. the need to replace non-biodegradable mineral oils with a biodegradable oil as cutting fluid has therefore necessitated this study. this work is therefore, an approach at investigating the comparative effect of using vegetable oil (a vegetable based cutting fluid) and soluble oil as cutting fluids when machining stainless steel on a lathe machine. 2 methodology 2.1 workpiece material, machine and tools the design of experiment for this work was done. the work piece material used in this experimentation was a stainless steel bar of diameter 30mm and length 1000m acquired from oshogbo-osun state, nigeria (fig. 1). the turning of the workpiece was carried out on a manually operated center lathe (lathe colchester mastiff 1400). a high speed steel (hss), aisi m-42 type (fig. 2) with a nose radius of 0.5mm, back rake angle of 6˚, side rake of 10˚, end cutting edge of 12˚ and side cutting edge of 12˚ was used as the cutting tool. a data logger digital electronic temperature indicating regulator model ted-2001 was used to monitor the temperature at the cutting zone during the machining operation. the thermocouple wire was attached to the tool holder at a 0.5mm distance from tool tip to sufficiently capture cutting temperature during the machining process (fig. 3). figure 1: stainless steel bar figure 2: hss cutting tool ogedengbe, awe and joseph (2019): international journal of engineering materials and manufacture, 4(1), 33-40 35 figure 3: experimental set up for machining process (a) (b) figure 4: cutting fluids used for experimentation (a) soluble oil, (b) vegetable oil 2.2 cutting fluids the cutting fluids used in this study were soluble oil (figure 4a) and groundnut oil (figure 4b). groundnut oil is a vegetable based cutting fluid which contains no destructive material and is environmental friendly. soluble oil used for the experiment was sourced from the school workshop when mixed with water, the soluble oil formed an emulsion that gave a milky appearance. the high oil content provides excellent physical lubricity for the cutting operation as well as protection for the machine tool. the composition of the soluble oil was 80% water and 20% based oil. 2.2.1 analysis of cutting fluids the analysis of the cutting fluids used was done. relative densities (specific gravity) was tested by hydrometer method (astm d 1298), the flash-point by pensky-martens closed cup tester astm d93. ph was tested using the ph meter, and finally the acid value and saponification were carried out by titration. the same method was carried out for the two oil samples respectively. table 1 shows results of the analysis. 2.2.2. design of experiment the taguchi method from minitab software version 18.0 was used for this work and a l9 orthogonal array was generated. the process parameters used for this study were cutting speed, feed rate and depth of cut. the process parameters and their levels are shown in table 2. an orthogonal array was generated which guided the machining process as shown in table 3. comparative analysis of machining stainless steel using soluble and vegetable oils as cutting fluids 36 table 1: results of physicochemical analysis properties analyzed vegetable oil soluble oil mixed soluble oil ph value 5.6 7.1 6.8 saponification (mgkohg -1 ) 72 79 85 acid value (mgkohg -1 ) density (g) 3.2 40.65 6.2 41.34 5.5 42.65 flash point ( o c) 117 114 80 viscosity (40 o c) (mm 2 /sec) 80 46 68 table 2: process and their levels for dry and cooled machining factor spindle speed (m/min) feed rate (mm/rev) depth of cut (mm) level 1 75 0.01 0.01 level 2 100 0.03 0.05 level 3 135 0.05 0.08 table 3: orthogonal array for machining from minitab spindle speed m/min feed rate mm/rev depth of cut mm 75 0.05 0.1 75 0.10 0.5 75 0.40 0.8 100 0.05 0.1 100 0.10 0.5 100 0.40 0.8 135 0.05 0.1 135 0.10 0.5 135 0.40 0.8 2.3 experimentation the machining experiment was carried out by turning of the workpiece on a manually operated center lathe, each work piece was mounted on a three jaw self-centering chuck of the lathe machine and properly secured using the chuck key. the cutting tool was mounted on the lathe tool post or tool holder after it has been grounded to the correct clearance and rake angles and in each experimental run, a fresh cutting tool was used for a fixed cutting time of not more than 20 minutes. the tool post was adjusted until approximately perpendicular to the work piece. the cutting temperature (temperature at the cutting zone) was measured using the temperature monitor. the work piece (stainless steel) was machined using the orthogonal array as shown in table 3. the orthogonal array generated a 9-run machining mix which was used both for machining with soluble oil and groundnut oil as cutting fluids. the workpiece was measured before and after each machining step and weight values were recorded to calculate material removal rate. 3 results and discussions the experiment was performed and numerical values obtained, these values (results) were analyzed using minitab 18 based on signal-to-noise (s/n) ratio. smaller-is-better s/n ratio was chosen for surface roughness (sr) since smaller sr indicates better performance of the process. 3.1 mean effects of s/n on surface roughness tables 4 and 5 shows the experimental surface roughness result and response table for s/n ratio obtained for both machining with vegetable oil and soluble oil based cutting fluid. minitab 18 allocates ranks based on the delta values; rank 1 to the highest delta value, shows that the feed rate (rank 1) had the strongest effect on surface roughness, second highest (rank 2) which is spindle speed and lastly is the depth of cut (rank 3) for both machining condition as shown in table 5. based on the analysis of the s/n ratio, from the table the optimal machining performance for the surface roughness was obtained at 75m/min spindle speed (level 1); 0.40mm/rev feed rate (level 3); 0.05mm depth ogedengbe, awe and joseph (2019): international journal of engineering materials and manufacture, 4(1), 33-40 37 of cut (level 2) for vegetable oil based cutting fluid, and 75m/min spindle speed (level 1); 0.40mm/rev feed rate (level 3); 0.08mm depth of cut (level 3) for soluble oil based cutting fluid. for both machining condition feed rate has the greatest effect on the surface roughness of the workpiece. 3.2 surface roughness analysis the maximum and minimum surface roughness values during machining using soluble oil as cutting fluid were 16.17μm and 9.21μm, however during machining using groundnut oil as cutting fluid, the maximum and minimum surface roughness values were 8.26μm and 3.84μm this represented a 49% and 60% improvement in the surface profile. this improvement was due to the reduction in maximum temperature at the cutting zone which ensured a preservation of surface integrity. groundnut oil was therefore a preferred cutting fluid for the reduction of surface roughness during machining of the stainless steel. its ability to improve surface integrity more than soluble oil was due to the higher lubricating property it possesses. as seen in figure 5, the surface roughness was generally lower when machining using vegetable oil as cutting fluid than when using soluble oil as cutting fluid. the results of physicochemical analysis done (table 1) showed that vegetable oil had a larger viscosity (80 mm 2 /sec) than soluble oil which had a viscosity of 68mm 2 /sec. the higher viscosity of vegetable oil played a major part in its ability to reduce surface roughness because of its higher lubricating ability therefore reducing more friction between workpiece and tool during turning than soluble oil, with a lower lubricating ability. vegetable oil had a lower acid value (3.2 mgkohg -1 ) hence had lower corrosive impact on the work piece than soluble oil with an acid value of 5.5 mgkohg. 3.3 cutting temperature analysis the temperature at the cutting zone was monitored during the experimental runs. as shown in figure 6 and table 6, the maximum temperature reduced from 305.1 o c recorded during machining with groundnut oil to 172.1 o c representing about 43% reduction in heat at cutting zone. during machining with soluble oil, the temperature drop from 160 o c to 80.2 o c represented about 50% heat reduction. this result shows soluble oil has a better performance in heat removal from the cutting zone than groundnut oil when used as a cutting fluid. this result agrees with the results of previous work carried out by abdulkareem et al. [2], who reported that vegetable oil has better lubricating abilities than soluble oil when machining carbon steel and adekunle et al [15] who reported soluble oil as a better coolant than vegetable oil. however, the flash point value for vegetable oil (117 o c) was higher than that of soluble oil (80 o c) hence, vegetable oil was therefore a preferred cutting fluid because it had a lower volatility and therefore reduced the possibility of hazard during use. this results agrees with v. koushik [9]. table 4: experiment layout, results and s/n ratios of surface roughness using vegetable oil and soluble oil spindle speed (m/min) feed rate (mm/rev) depth of cut (mm) vegetable oil soluble oil surface roughness μm s/n ratio surface roughness μm s/n ratio 75 0.05 0.01 4.67 -13.3863 9.84 -19.8599 75 0.10 0.05 7.24 -17.1848 14.23 -23.0641 75 0.40 0.08 8.26 -18.3396 16.17 -24.1742 100 0.05 0.05 4.22 -12.5062 9.49 -19.5453 100 0.10 0.08 6.01 -15.5775 13.28 -22.4640 100 0.40 0.01 7.99 -18.0509 14.77 -23.3876 135 0.05 0.08 3.84 -11.6866 9.21 -19.2852 135 0.10 0.01 5.21 -14.3368 12.65 -22.0415 135 0.40 0.05 6.99 -16.8895 13.12 -22.3587 table 5: response table for signal to noise ratios level vegetable oil soluble oil spindle speed (m/min) feed rate (mm/rev) depth of cut (mm) spindle speed (m/min) feed rate (mm/rev) depth of cut (mm) 1 -16.31* -12.53 -15.26 -22.37* -19.56 -21.76 2 -15.38 -15.70 -15.53* -21.80 -22.52 -21.66 3 -14.30 -17.76* -15.20 -21.23 -23.31* -21.97* delta 2.00 5.23 0.33 1.14 3.74 0.32 rank 2 1 3 2 1 3 optimum level: * comparative analysis of machining stainless steel using soluble and vegetable oils as cutting fluids 38 table 6: temperature obtain at various machining condition run spindle speed m/min feed rate mm/rev depth of cut mm stainless steel temperature (℃) vegetable oil temperature (℃) soluble oil 1 75 0.05 0.01 201.3 100.4 2 75 0.10 0.05 186.4 91.7 3 75 0.40 0.08 172.1 80.2 4 100 0.05 0.05 271.1 120.4 5 100 0.10 0.08 268.4 111.3 6 100 0.40 0.01 260.1 103.7 7 135 0.05 0.08 305.1 160.1 8 135 0.10 0.01 287.3 151.2 9 135 0.40 0.05 264.9 132.7 figure 5: surface roughness for experimental runs suing various cutting fluids figure 6: maximum temperature attained during machining with various cutting fluids. 0 50 100 150 200 250 300 350 400 450 500 1 2 3 4 5 6 7 8 9 s u rf a ce r o u g h n e ss experimental run 0 50 100 150 200 250 300 350 1 2 3 4 5 6 7 8 9 m a xi m u m t e m p e ra tu re experimental runs vegetable oil soluble oil ogedengbe, awe and joseph (2019): international journal of engineering materials and manufacture, 4(1), 33-40 39 4 conclusions a set of experimental investigations to consider the effect of using soluble oil and vegetable oil as cutting fluid during machining stainless steel has been successfully attempted. the following conclusions have been reached at the end of the experiment: 1. feed rate and cutting speed had a significant effect on the surface quality of stainless steel during machining. feed rate was the most significant control factor on the surface roughness during machining using vegetable oil and soluble oil. depth of cut had no significant effect on surface quality of machined steel. 2. vegetable oil performed more favorably as a lubricant as it produced a workpiece with a better surface finish than soluble oil during machining of stainless steel. this improvement represented a 49% and 60% improvement in the maximum and minimum values of surface profile comparing both vegetable and soluble oils as cutting fluid. 3. soluble oil performed better in temperature reduction at the cutting zone as it reduced temperature at cutting zone by 50% while vegetable oil was only able to reduce temperature at cutting zone by 43%. the overall results are summarized below: however, it can be concluded that vegetable oil produced a better surface finish and hence it is evident that soluble oil based cutting fluid can be replaced with vegetable oil based cutting fluid. acknowledgement the authors wish to appreciate the efforts of mr olusoji ajayi of central laboratory of elizade university and mr. aladejana yezeed of mechanical engineering department of elizade university for their support and assistance during this study. references 1. bissey-breton s., vignal v., herbst f. & coudert j.b. (2016), “influence of machining on the microstructure, mechanical properties and corrosion behaviour of a low carbon martensitic stainless steel”, procedia cirp, 46, 331 – 335. 2. abdulkareem s., ogedengbe t.s., aweda j.o. & khan a.a. (2017). comparative analysis of aisi 1050 steel using n5-soluble oil and arachis oil in metal cutting operation, proceedings of the 30th agm and international conference of the nigerian institution for mechanical engineers. kaduna, 195 – 206 3. sokovic, m. & mijanovic, k. (2001). ecological aspects of the cutting fluids and its influence on quantifiable parameters of the cutting processes, journal of material processing technology, 109 (1-2), 181189. 4. deepak joel j. r., leo dev k., wins, anil raj & anuja beatrice b. (2014) optimization of cutting parameters and fluid application parameters during turning of ohns steel, 12th global congress on manufacturing and management, gcmm 5. lawal, s. a., choudhury, i. a., & nukman, y. (2012). application of vegetable oil-based metalworking fluids in machining ferrous metals—a review. international journal of machine tool and manufacture, 52(1), 1–12 6. krishna p. v., srikant, r. r., & rao, d. n. (2011). solid lubricants in machining. proceedings of the institution of mechanical engineers, part j: journal of engineering tribology, 225(4), 213-227. 7. belluco, w. & de chiffre l. (2001). testing of vegetable-based cutting fluids by hole-making operations. lubrication engineering, 57, 12–16. 8. shashidhara y. & jayaram s. (2010), vegetable oils as a potential cutting fluid— an evolution, tribology international, 43, 1073-1081. 9. vaibhav koushik a.v, narendra shetty. s & ramprasad.c (2012), vegetable oil-based metal working fluids-a review, international journal on theoretical and applied research in mechanical engineering (ijtarme), volume-1, issue-1, 2012, ppg 95-101. 10. shankar s., mohanraj t. & ponappa k. (2017). influence of vegetable based cutting fluids on cutting force and vibration signature during milling of aluminium metal matrix composites. jurnal tribology, 12, 1-17. 11. w. belluco and l. de chiffre, performance evaluation of vegetable-based oils in drilling austenitic stainless steel, journal of materials processing technology 148 (2004), pp. 171-176. 12. a. m. al sabagh, n. a. maysour , n. m. nasser & m. r. sorour (2006) some cutting oil formulations based on local prepared emulsifiers part i: preparation of some emulsifiers based on local raw materials to stabilize cutting oil emulsions, journal of dispersion science and technology, 27:2, 239 250, doi: 10.1080/01932690500267215 13. kolawole s.k. and odusote j.k. (2013) ―performance evaluation of vegetable oil-based cutting fluids in mild steel machining‖, chemistry and materials research, issn 22243224 (print) issn 22250956 (online), vol.3 no.9, page 35-45. comparative analysis of machining stainless steel using soluble and vegetable oils as cutting fluids 40 14. fairuz m.a., nuruladlina m.j., azmi a.i., hafiezal m.r.m., leong k.w., "investigation of chip formation and tool wear in drilling process using various types of vegetable-oil based lubricants", applied mechanics and materials, vols. 799-800, 2015, pp. 247-250. 15. adekunle a.s., adebiyi k.a., durowoju m.o. (2015). performance evaluation of groundnut oil and melon oil as cutting fluids in machining operation, acta tehnica corviniensis – bulletin of engineering, tome viii [2015] fascicule 1 [january – march], issn: 2067 – 3809 international journal of engineering materials and manufacture (2018) 3(4) 216-223 https://doi.org/10.26776/ijemm.03.04.2018.06 r. k. arief1 , q. nurlaila2 and armila3 1universitas muhammadiyah sumatera barat, padang west sumatera, indonesia e-mail: rudikarief@umsb.ac.id 2universitas riau kepulauan, batam kepri, indonesia e-mail: laila@ft.unrika.ac.id 3universitas muhammadiyah sumatera barat, padang west sumatera, indonesia e-mail: armila@umsb.ac.id reference: arief, r. k., nurlaila, q. and armila (2018). comparative study of conventional and quick die change stamping process: the issue of setup time and storage. international journal of engineering materials and manufacture, 3(4), 216-223. comparative study of conventional and quick die change stamping process: the issue of setup time and storage rudi kurniawan arief, qomarotun nurlaila and armila received: 16 september 2018 accepted: 22 october 2018 published: 01 december 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract metal stamping industry has quick die change (qdc) as a form of single minutes exchange of dies (smed) as an efficient production technique where the implementation depends on operator’s activities, clamping system, accessories type and position, etc. this qdc could apply to improve the process efficiency, control of inventory and reducing the cost. this research compared the traditional metal stamping process and qdc system (qdcs) of metal stamping. this research was using focused group discussion (fgd), direct observation and experiments, conducted in a private metal stamping company in wider jakarta region of indonesia. it was observed that the qdcs significantly reduces setup time, storage space and the cost. the setup time and cost reduced to one third of the conventional and the requirement of storage decreased by 70%. in addition, qdcs reduces the waste significantly. keywords: smed, qdc, process efficiency, lean manufacturing 1 introduction in the field of manufacturing industry especially metal stamping industry, the single minute exchange of die (smed) founded by shigeo shingo during 1950’s is the most widely used [1]. smed increased efficiency in metal stamping by moving the setup process of stamping die that usually held at the machine bed in outside area, which become a preset up process. due to high production rate, product variability, short product’s lifecycle and inventories, the smed technique become a popular method in metal stamping industries [2]. later, this smed technique also developed to other field of industry outside metal stamping. today’s trend required higher demand of product variation by the costumer. this has become a big problem for metal stamping company, since metal stamping required large quantity production to reduce the overall cost. large product variation required frequent change of tools (die set) and low scale production than usual which make company to focus on process innovation [3]. the main focus of smed is to eliminate wastes from tool setting activities by reducing the time less than 10 second [4]. in metal stamping industry, this smed technique also called by quick die change (qdc) with the concept of simplification of in-machine setup by the standardized activities and work sequence. most of the qdc techniques associated with machine and tools accessories, operator’s activities such as clearing area, clamping, setting, etc. [5], which reduces the waste and save 75% time and 50% manpower [6]. 2 quick die change the smed technique invented by shigeo shingo may increase production capacity up to 40% by making a clear arrangement of the production activities [1]. in 2002, a japanese fumio yamaguchi developed a new system of qdc (qdcs) by modifying the die stamping die itself [7]. qdcs has become further step of smed to reducing waste and mailto:rudikarief@umsb.ac.id mailto:laila@ft.unrika.ac.id mailto:rudikarief@umsb.ac.id comparative study of conventional and quick die change stamping process: the issue of setup time and storage 217 decreasing company’s expenses that modify the construction of metal stamping die. the concept of qdcs, in die construction point of view, is to separate main die or stamping function with the support function. parts with die stamping function are grouping as one assembly named quick die change dies / qdcd and group of parts with support function as the other assembly named quick die change housing / qdch as shown in figure.1. in the construction of conventional die, supporting and main components construct as one big assembly as shown in figure. 2. this cause higher cost to construct a die for a small component. with qdcs company only need to build the qdcd to be inserted into qdch and qdch may use for many of qdcd. this inserted and exchanging system of qdcs could save manufacturing cost for about 35% [8]. 3 methodology this research is to investigate the advantages termed as “efficiency” that might gain from the implementation of qdcs. investigation will include the efficiency gained from setup time, storage area and the cost for all of these. main data are collected from direct observation and interview. activities held in a metal stamping company near jakarta wider region. focused discussion group attended by manager and supervisor from department of engineering, quality control and production of designated company. time consumed by the operators to setup the dies has been counted and compared. dimension of dies and the storages has been measured. those two parameters have been converted into parameter of cost based to indonesian currency (rupiah / idr). figure 1: construction of qdcs. blue dashed line is showing the construction of qdch and yellow full line show the construction of qdcd. figure 2: construction of conventional die arief, nurlaila and armila (2018): international journal of engineering materials and manufacture, 3(4), 216-223 218 4 analysis of setup time efficiencies the qdcs is the combination of qdcd and qdch where qdcd is very light in weight so it can be carried by hand, while conventional dies must be carried by lifting device. observation will count the setup time from picking up dies from the storage, positioning on the table, machine’s height setup (inching), clamping, unclamping and unloading out of the machine. these steps from each die construction have been compared. 4.1 setup time of conventional die time counted from the first operator picking up dies from storage in different room by forklift. die operator then adjusted the position of dies according to applicable clamping groove. the machine height is adjusted to desired position and then operator start to clamps. dies were unclamped after production process is finished and took by forklift operator to put back to storage area where located 10 meters away. flow process shown by chart in figure 3. 4.2 setup time of qdch qdch must be setup before qdcd can be use. setup time is similar to conventional die since qdch has big construction as conventional die and placed in the same storage area. setup process also similar to the conventional die. 4.3 setup time of qdc qdcd as explained before will be placed inside of the qdch, so the observation condition is where the qdch already installed. qdcd has been picked up from the storage that located two meters away, and could pick up directly by hand. qdcd then easily positioned inside the qdch with help of guide rail provided. inching did not take long time because initial inching already done by setup of qdch. clamping devices have already been provided for quick clamping and unclamping activities. setup and uninstall process is shown in figure 4. figure 3: process chart for conventional die setup figure 4: process chart for qdcd setup comparative study of conventional and quick die change stamping process: the issue of setup time and storage 219 4.4 setup time comparison table 1 explained the comparison of setup time between two systems. from data presented in figure 5, shown huge differences between those two dies construction. qdcd setup is 69% faster compared to conventional die. however, qdcd is depends to qdch, so setup time of qdch must be added in order to know real efficiencies. data above shown that using one qdc is less efficient (-30.61%) because combination setup time of qdch and qdcd. however, after application of two qdcd that use directly after the first die, efficiency gap become wider. the increasing of gap percentages can be seen in table 2 as well as in figure 6. table 1: comparison of setup time activities qdcd (s) conventional die (s) pickup dies 13 90 positioning 5 26 inching 4 9 clamping 78 192 unclamps 66 152 unload dies 15 120 total time 181 589 3 minutes 9,8 minutes figure 5: setup time comparison chart table 2: efficiencies comparison number of die to be installed sequentially conv' die (s) qdcs (s) efficiency percentages qdcs to conv' die 1 9,8 12,8 -30,61% 2 19,6 15,8 19,39% 3 29,4 18,8 36,05% 4 39,2 21,8 44,39% 5 49,0 24,8 49,39% 8 78,4 33,8 56,89% 10 98,0 39,8 59,39% 15 147,0 54,8 62,72% 20 196,0 69,8 64,39% 13 5 4 78 66 15 90 26 9 192 152 120 0 50 100 150 200 250 pickup dies positioning inching clamping unclamps unload conv' die qdcd arief, nurlaila and armila (2018): international journal of engineering materials and manufacture, 3(4), 216-223 220 figure 6: efficiencies comparison’ chart, comparing setup time required for some number of dies. 4.4 setup time cost comparison setup process from the observation above then analysed into cost parameters. manpower and machine rate will be calculated as the parameter of direct cost. cost of electricity, maintenance, administration, factory rent, etc. will be ignorance. since observation conducted in indonesia the cost calculation will using idr by assuming 1 usd = 14.000 idr. observed stamping process was conducted with 80 tons manual stamping machine, operated by one person. observed company is located in kota bekasi, an industrial city near jakarta. only net wage will be calculated outside any allowance might offer by the company to their labour. current minimum labour wages (umr) for manufacturing industry in this area in 2018 is 3.900.000 idr with 26 days of working per month. lc = umr / 26 days/ 8hour/ 60minutes (1) = 3.900.000 /26 / 8/ 60 = 312,5 idr / minute. labour cost per minute is 312,5 idr. from table 1, we have data of setup time for qdcs is 3 minutes (st1) and conventional die is 9,8 minutes (st2). labour cost to performance the setup is labour cost per minutes times setup time. sc1 = st1 x lc (2) = 3 min x 312,5 idr = 937,5 idr. sc2 = st2 x lc (3) = 9,8min x 312,5 idr = 3.062,5 idr. eg = sc2 – sc1 (4) = 3.062,5 – 937,5 = 2,125 idr. where, umr= current minimum labour wages, lc= labour cost (idr/min), st1= setup time for qdcs (minutes), st1= setup time conventional die (minutes), sc1= setup cost for qdcs (idr), sc2= setup cost for conventional die (idr), eg= efficiency gap (idr). 1 2 3 4 5 8 10 15 20 conv die (minutes) 9.8 19.6 29.4 39.2 49.0 78.4 98.0 147.0 196.0 qdc (minutes) 12.8 15.8 18.8 21.8 24.8 33.8 39.8 54.8 69.8 0.0 50.0 100.0 150.0 200.0 250.0 se t u p ti m e (m in u te ) die qty (unit /pcs) comparative study of conventional and quick die change stamping process: the issue of setup time and storage 221 machine rate for 80 tons stamping machine is 170 idr per stroke, machine can perform 360 stroke per hour or 6 stroke per minute. spm = sph/60 (5) = 360/60 = 6 stroke/min. mc1 = st1 x spm (6) = 3 x 6 = 18 strokes. mf1 = mc1 x mr (7) = 18 x 170 = 3.060 idr. mc2 = st2 x spm (8) = 9,8 x 6 = 58,8 strokes. mf2 = mc2 x mr (9) = 58,8 x 170 = 9.996 idr. er = 100 % (100% x (mf2/mf1)) (10) = 100% (100% x (3.060/9.996)) = 100% 30,6% = 69,4%. where, sph= stroke per hour, spm= stroke per minute, mr= machine rate, mc1= machine cost for qdcs, mf1 = machine fee for qdcs, mc2= machine cost for conventional, mf2= machine fee for conventional, er= efficiency rate. converting to machine rate qdcd setup cost is 3.060 idr and conventional die 9.996 idr. qdcd successfully reduced direct cost by 69,4% compared to conventional die. summary of cost calculation is presented in table 3. table 3: cost efficiencies comparison parameters qdcs conventional manpower 938 idr 3.063 idr machine rate 3.060 idr 9.996 idr total cost 3.998 idr 13.059 idr 5 analysis of storage efficiencies smed technique not just increase productivity and reduce cost but also able to reducing inventories [2]. qdcd built with smaller size due to it’s insertable function while qdch is same in size but less height than the conventional die. the qdch only require 1 unit for each stamping machine, so the quantity is very less and qdcd will be more because manufactured 1 unit for each process. the size of qdcd and qdch is already standardized and conventional die will be analysed with minimum size that can be build. analyses is doing by simulating the data taken accordingly to the situation in designated company that owned 80 units of qdcd, 5 units of qdch and hundreds of conventional dies. analysis conducted by simulating the storage for 80 unit of dies. qdcd required 5 row and 16 column storages to store 80 units of die with total foot print consumed 1.680 meters (figure 7). conventional die needs 4 row and 20 column storages to store 80 units of die with total foot print 5.520 meters (figure 8). monthly factory space rent fee at designated company’s location is 40.000 idr /m. qdcd save rent fees 153.600.000 idr every month due to small storage area required. comparing with conventional die, qdcs reduce cost for storage to 70%; the details are shown in table 4. arief, nurlaila and armila (2018): international journal of engineering materials and manufacture, 3(4), 216-223 222 table 4: storage comparison for 80 units qdcs and conventional die a b c d e f g h =fxg i j=hxi die type die size (mm) space required (mm) storage rack (80 dies) space dimension (mm) total space (m) rent pe meter (idr) monthly rent fee (idr) row column width length qdcd 250 x 200 x 150 350 x 300 x 250 5 16 300 5.600 1.680 40.000 67.200.000 con'v die 500 x 360 x 300 600 x 460 x 450 4 20 460 12.000 5.520 40.000 220.800.000 figure 7: storage for qdcd figure 8: storage for conventional die comparative study of conventional and quick die change stamping process: the issue of setup time and storage 223 5 conclusions from the observation and analysis above qdcs could make efficiencies up to 70% compares to conventional die. amount of 153.000.000 idr might be saved by the sleek design of qdcs from storages area, so some other wide storage spaces may be used for other productive activities. but company must pay attention for production arrangement where this qdcs must be employed sequentially for at least two qdcd, otherwise efficiently of process may decrease to 31%. the qdcs must be employed sequentially in order to gain higher efficiency. with amount of efficiency achieved and plenty of money saved, metal stamping industry should be considering this system for their efficiency effort to produce more variable products with lower amount of quantity in a reasonable price. acknowledgement this research was funded by ministry of research, technology and higher education indonesia under research grant scheme of penelitian dosen pemula 2018 (project number: 013/kontrak-penelitian/lppm-umsb/2018). the authors are grateful to the management team and employees of pt. sanwa presswork indonesia where most of this research activities took place. this is the enhancement version of previous conference paper that has been submitted to cites 2018 international conference. references 1. shingo, s. (1985). a revolution in manufacturing: the smed system. productivity press, oregon. 2. yash, d. & sohani, n. (2012). single minute exchange of dies: literature review. international journal of lean thinking, volume 3, issue 2. 3. moreira, a. c., pais, c. g. s., (2011). single minute exchange of die. a case study implementation. journal of technology management & innovation, volume 6, issue 1. 4. abraham, ganapathi k. n., motwani, k. (2012). setup time reduction through smed technique in a stamping production line. sas tech journal, volume 11, issue 2, sep 2012. 5. solehah, s (2013). design and development of smed quick die change tools for small press dies. university malaysia pahang, malaysia. 6. yamaguchi, f. (2013). phillipine metal stamping sector study 2013. jaoan metals industry research and development center and philipine departemen of science and technology, taguing city. 7. arief, r. k. (2018). time and cost efficiency analysis of quick die change system on metal stamping industry.world academy of science, engineering and technology, international journal of industrial and systems engineering, vol:12, no:2, 2018. dai:10.1999/1307-6892/10009095. 8. suchy, i. (2006). handbook of die design”. new york, mcgraw-hill. 9. paquin, j. r., crowley, r. e., (1986). “die design fundamentals, 2nd ed”, industrial press inc., new york. international journal of engineering materials and manufacture (2021) 6(1) 60-80 https://doi.org/10.26776/ijemm.06.01.2021.06 samsul islam, md. shariful islam and mohammad zoynal abedin department of mechanical engineering dhaka university of engineering and technology gazipur 1700, bangladesh e-mail: abedin.mzoynal@duet.ac.bd reference: islam et al., (2021). review on heat transfer enhancement by louvered fin. international journal of engineering materials and manufacture, 60-80. review on heat transfer enhancement by louvered fin samsul islam, md. shariful islam and mohammad zoynal abedin received: 15 october 2020 accepted: 28 january 2021 published: 30 january 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract the heat transfer enhancement is recycled in many engineering uses such as heat exchangers, refrigeration and air conditioning structures, chemical apparatuses, and automobile radiators. hence many enhancing extended fin patterns are developed and used. in multi louvered fin, in this segment for multi-row fin and tube heat exchanger, an increase in heat transfer enhancement is found 58% for reh = 350. when the reynolds number is 1075, the temperature gradient is more distinct for greater louver angle that is the higher heat transfer enhanced for large louver angle. for variable louver angle heat exchanger, the maximum heat transfer improvement achieved by 118% reynolds number at 1075. in the vortex generator for the delta winglet vortex generator, the extreme enhancement of heat transfer increased to 16% compared to the baseline geometry (at redh = 600). for a compact louvered heat exchanger, the results showed that a regular arrangement of louvered fins gives a 9.3% heat transfer improvement. in multi-region louver fins and flat tubes heat exchanger, the louver fin with 4 regions and the louver fin with 6 regions are far better than the conventional fin in overall performance. at the same time, the louver fin with 6 regions is also better than the louver fin with 4-region. the available work is in experimental form as well as numerical form performed by computational fluid dynamics. keywords: heat transfer enhancement, louvered fin heat exchanger, vortex generator, compact heat exchanger, multi-region louver fin. nomenclature: abbreviation/symbol meaning lp louver pitch l louver length θ louver angle re reynolds number nu nusselt number t fin thickness h fin pitch nl number of louvers mrfthe multi row fin and tube heat exchanger dwvg delta winglet vortex generator ilfhe inclined louvered fin heat exchanger vlahe variable louver angle heat exchanger clhe compact louvered heat exchanger 1 introduction nowadays, researchers are concentrating on the improvement of the performance of heat exchangers having a high degree of surface compactness and optimal overall thermal-hydraulic performance. in gas to a fluid heat exchanger, the thermal resistance is dominant on the gas side which is up to 80% to that of total thermal resistance in a heat exchanger. therefore, the main reason for lower thermal performance on the gas side is attributed to the fact that approximately 10 to 50 times smaller heat transfer coefficient can be achieved for gas than that of fluid. hence, it is widely expected to enhance the researches in the field of heat transfer enhancement for future applications in the mailto:abedin.mzoynal@duet.ac.bd review on heat transfer enhancement by louvered fin 61 engineering fields. it is widely used in air conditioning systems, power generation, automobiles, and other applications. an air-cooled heat exchanger is much more essential nowadays. when hot fluid flows inside the tubes and airflow outside the tubes acts as a cold fluid. fins are usually used on the airside of air-cooled heat exchangers to increase heat transfer performance [1]. louvered fins are widely used for air side heat transfer surface of heat exchangers, such as automotive radiators, air cooled oil coolers, intercoolers, heaters and the like. heat transfer performance of louvered fins is largely affected by various and complicated flows changed by configuration and arrangement (length, angle, pitch). although many researchers have reviewed various experimental studies for louver-fin heat exchanger, the papers reviewed heat transfer enhancement for the single louvered fin, multi louvered fin, relatively high louver angle, low fin pitch and compact heat exchanger. the following section deals with the enhancement techniques with a detailed analysis. 2 enhancement techniques it can be divided into two groups. one is the “active technique” which requires an exterior power source to enhance heat transfer. the other one is the “passive technique” which requires no direct application of external power. the passive technique is an economical and widely used heat transfer enhancement technique. the heat transfer rate in heat exchanger is given by equation as, q = h a θm (1) where h is heat transfer coefficient, a is effective heat transfer surface area and θm is the mean value of temperature difference. the use of the passive technique to enhance heat transfer with considering the heat transfer equation is in the following manners. 1) increase the effective heat transfer surface area a per unit volume without appreciably changing heat transfer coefficient h e.g. uses of plain fin surface. 2) increase coefficient h without changing area a by using special shapes like crimped or ridged fins. that fin provides involvement due to subordinate flows and borderline coat parting within the channel. 3) increase both h and a e.g. interrupting fins like louvers. figure 1: typical louver fin pattern [2]. louver fin pattern is one of the most advanced enhanced extended surfaces which are essentially formed by cutting the sheet metal of the fin at breaks and rotating the strips of a metallic object so formed out of the fin. figure 1 shows the geometrical definition of a heat exchanger with louver fins. louver fin has geometrical parameters like louver pitch, louver height, louver depth, louver angle, number of louvers, number of louver regions. enhancement of heat transfer is dependent on geometrical parameters of louver fins hereafter researches are going on optimizing the thermo-hydraulic performance of heat exchanger with respect of louver type’s enhancer. in this paper, it has been discussed on heat transfer enhancement by different types of louvered fin and also gives a comparison of heat transfer enhancement of various enhancement types. islam et al., (2021): international journal of engineering materials and manufacture, 6(1), 60-80 62 3 single louvered fins 3.1 single and double row tubes with louvered fins in this study, simulations are performed for reynolds numbers (red), ranging from 400 to 4000. this is accomplished with the reynolds number range established on louver pitch (relp) of 60 to 1800. as outlined in experimental observations of antoniou et al., [3] have presented that the flow is laminar for up to a reynolds number of nearly 1300. although flow unevenness occurs upstream and downstream of the louver for relp = 1300, the flow remains principally laminar. to discourse this issue, three-dimensional models are achieved in the existing study with the rng k–ε turbulence model to estimate the heat transfer and pressure drop appearances and to verify the local turbulence behaviour of the flow field. the heat transfer results are found to be 6–7% higher than those without the turbulence model. since this difference is not so large, the assumption of laminar flow is retained for relp up to 1300. for relp > 1300, the turbulent flow equations are resolved. this study has implemented an arithmetical simulation of single and double row tubes with louvered fins. figure 2 shows the computational domain used in the numerical study. figure 2: computational domain louver fins [4]. it has been found that at a low reynolds number maximum of air flows through the gap between the fins rather than through the louvers. reynolds numbers, when it is higher the boundary layers everywhere the louvers are thinner and the flow is nearly united with the louvers. here heat transfer rate is upgraded with reynolds number. heat transmission and pressure drop features are obtained in terms of non-dimensional parameters, stanton number (st), and friction factor (f) as functions of reynolds number. there is a close contract is found between the computational results and experimental data at mid and high reynolds numbers. nonetheless, when reynolds number is low then there is huge deviance. the local nusselt number on the top surface of each louver in the flow direction along the length of fin for reynolds number red = 1000 is obtained; high nusselt number is gained at the tip of the fin, leading-edge and rambling edge of every louver. it has observed that heat transfer coefficient increases with louver angle and extents maximum value at (28 – 29) ◦ and then again falls with the rises in louver angle for fin pitch 2.17 mm also higher heat transmission coefficient is found at minor louver pitch, as lp=0.81 mm at optimal louver angle. by decreasing the fin pitch from 3.33 mm to 2.11 mm, the heat transfer rate increases. although an additional decrease in louvered fin pitch does not result in any additional development in heat transfer. 3.2 louvered fin and tube heat exchanger here the physical model and computational domain of the replicated louvered fin and tube heat exchanger are demonstrated in figure 3 simple constraints of this geometry for two cases of validation and sensitivity study are demonstrated in table 1. for specifying the effect of reynolds number on parameters j/j0 and f/f0, these parameters vs. louver angles are shown in figure 4. the velocity of air inlet was improved from 1 m/s to 6.5 m/s which produced in deviation of reynolds number from 1250 to 8100. it is demonstrated that maximum percentage changes of parameter j/j0 is approximately 10%, so the effect of reynolds number on parameter j/j0 can be ignored. this value is 16% for consideration f/f0 and it can also be unnoticed. review on heat transfer enhancement by louvered fin 63 figure 3: physical model and computational domain [5]. table 1: general geometric parameters of simulated louvered fin [5]. parameters general values for validation (flat fin) general values for validation (louvered fin) general values for parametric study tube collar outside diameter (dc) 10.23 mm 10.42 mm 10.42 mm tube row number 2 2 2 fin thickness (t) 0.13 mm 0.115 mm 0.115 mm length of louvered region (l) 15 mm 15 mm number of louvers 4 4 width of louvered region (w) 12.5 mm 12.7 mm fin pitch (fp) 2.24 mm 2.06 mm 3.75 mm longitudinal tube pitch (pl) 22 mm 19.05 mm 19.05 mm transversal tube pitch (pt) 25.4 mm 25.4 mm 25.4 mm louver angle (θ) 13.5° mm 0-60° figure 4: effect of reynolds number on parameters j/j0 and f/f0 in different louver angles [5]. islam et al., (2021): international journal of engineering materials and manufacture, 6(1), 60-80 64 4 multi louvered fins 4.1 multi row fin and tube heat exchanger the episodic geometry besides the tube and the symmetry alongside the airflow way has permitted for oversimplification of the model geometry. the geometric parameters of louvered fins are demonstrated in figure 5. the hastened line in figure 5 indicates the computational domain. a 3d design of the unit cell used in the condition of louvered fins is shown on figure 6. figure 6 shows the louvered fins solid body in impervious while the shaded volume indicates the fluid zone. the cad tool used allows for simplicity in adjusting the variable design parameters (l, lp, nl, θ). the values for the main design constraints are recorded in table 2 with the inconstant factors, as analysed in this paper, and are shown as ranges. figure 5: plane and side visions of louvered fins and explanations of geometric parameters [6]. figure 6: fluid zone (shaded) round the louvered fin (opaque) [6]. review on heat transfer enhancement by louvered fin 65 all results are showed as a function of the reynolds number reh with the length scale expressed concluded fin pitch. the louvered fin heat exchanger was analysed with fin parameters set as displayed in table 2 and with the resulting louver constraints l/2 = 6.25 mm, lp = 3.75 mm, and θ = 14°. the area-averaged temperature on the episodic surface of the model was used as the fluid bulk temperature (tb) to control the heat transfer coefficient the most difficult constraint to evaluate. in figures 7 and 8the experimental values are indicated with a 10% comparative error bar to visualize the accordance of the obtained numerical results. the mathematically projected pressure drop relates strangely well with the experimental results, as seen in the figure 8. the calculated averaged nusselt numbers are very comparable to the experimentally acquired values, but over emphasized by almost 10% over the total range of observed reh numbers showing in figure 7. table 2: the detailed geometry of the examined heat exchangers [6]. parameters values tube outside diameter 10.42 mm the number of tube row 2 longitudinal tube pitch (pl) 19.05 mm transverse tube pitch (pt) 25.4 mm fin thickness (t) 0.115 mm fin pitch (h) 2.06 mm number of louvers (nl) 4-5 louver angle (θ) 5-25° louver pitch (lp) 15 mm/nl louver length (l) 4-12 mm figure 7: comparison of numerically & experimentally achieved average nusselt number for the louvered fin [6]. islam et al., (2021): international journal of engineering materials and manufacture, 6(1), 60-80 66 figure 8: comparison of numerically & experimentally achieved average pressure drop for the louvered fin [6]. 4.2 multi-region louver fins and flat tubes heat exchanger nowadays, well-organized heat exchangers are compulsory for saving energy. because of high compactness and outstanding heat transmission enactments, the aluminium-brazed heat exchanger with multi-louvered fin and the flat tube is used widely in residential air conditioning systems, automotive, aviation, dynamical machine fields, and so on. davenport [7, 8], achaichia [9], achaichia and cowell [10] observed air-side heat transfer and flow performance for louvered fin heat exchangers and obtained j and f factors as occupations of the reynolds number. huihua and xuesheng [11] accompanied an investigational study by a scaled-up louvered fin model with dissimilar louver angles and pitches. their investigational results showed that both the strength of heat transfer and pressure drop improved with growths in oblique angle and plate length. aoki et al., [12] completed an investigational study on the heat transfer characteristics of dissimilar louver fin ranges such as louver angles and louver and fin pitches, reporting that the coefficients of heat transfer at low air velocity reduced with increasing fin pitch. rugh et al., [13] calculated heat transfer coefficients and friction losses for high-density louvered fin and flat tube heat exchangers (2000 fins/m) and suggested j and f correlations. it has been found from their study that a louvered fin heat exchanger formed a 25% increase in heat transfer and a 110% increase in pressure drop comparative to a plain fin. it has been implemented in this experiment on airside heat transmission and pressure drop features of heat exchangers with multi-region louver fins as well as flat tubes on the louvered pitch with reynolds numbers from 400 to 1600. figure 9 shows seven types of examples of heat exchangers with a different number of louver regions (0 to 6) and fin louver statures were verified. the j factor and f factor tend to reduce with an increasing reynolds number and tend to rise with the enlarged number of louver regions. the cause is that with the increased number of louver regions, the louver area of the fin rises. the results show that the louver fin with 4 regions and the louver fin with 6 regions are far better than the conventional fin in overall performance. at the same time, the louver fin with 6 regions is also better than the louver fin with 4-regions. 4.3 multi-louvered fin and flat tube heat exchanger an accurate valuation of probable air-side heat transfer surface geometries is a prerequisite for the best possible heat exchanger plan. a simplified and translucent analytical procedure for the evaluation of multi louvered fin and flat tube heat exchanger geometries that permit maximal performance for given borderline conditions has been developed [15]. figure 10 shows a schematic diagram of the test apparatus used in the study. the construction of this test apparatus contains a suction type wind tunnel, heat transfer fluid as water movement and control units, and a data acquirement system and is located in a continuous temperature and moisture compartment. review on heat transfer enhancement by louvered fin 67 figure 9: multi region louver fin patterns [14]. figure 10: schematic diagram of the test apparatus [16]. the study has been stated with investigate on the side of air in heat transfer as well as pressure fall features for the heat exchangers of multi louvered fin and flat tube. here the air adjacent thermal enactment data has analysed using the effectivenessntu method for cross-flow heat exchanger. here when using 16 mm flow depth then the heat transfer coefficients does not change more with respect to louver angle. in the other term, if used 24 mm flow depth then heat transfer coefficients increase with louver angle and extreme at 27°, and again fall with louver angle. the friction factors are increased with louver angle and the j factor increased with louver angle, but its effect on the j factor differs with flow depth. islam et al., (2021): international journal of engineering materials and manufacture, 6(1), 60-80 68 5 inclined louvered fins 5.1 inclined louvered fin heat exchanger air conditioning has evolved from a luxury item into a standard appliance during the past decades. at first, these units could only be found in office buildings, airports, supermarkets, etc. but now the main market for the air conditioning manufacturers in the domestic one. sales in this market have seen tremendous growth, no doubt due to the string of hot summers in europe and the united states, as well as to the continuous drop in price for this product. at this moment, about 80% of all us homes use air conditioning during the summer to improve domestic comfort [17]. the heat exchanger used in this research is part of a commercially available air conditioning unit and has continuous fins. the measurements were taken at solid-state conditions. through the measurements, the inlet temperature of the water varied faintly (temperature drop of ±1°c). this temperature was measured by a pidcontroller. once the motionless command was achieved, the rail was positioned behind the tubes. for each tube a series of 10–15 samples were taken and this for 15 second. during these samples, the signal of the water flow meter was logged continuously. in figure 11 measurements can be seen. all constraints of the current fin plan are fine within the sort of the verified examples, excepting the longitudinal fin pitch (22 mm) which is just outside the range (12.4 27.5 mm). from figure 11 it is strong that the external convective heat transfer coefficient is on average 2.3 times higher than that for a plain fin (reaching from 2.15 for small reynolds numbers to 2.5 for high reynolds numbers). as the reynolds number rises the flow becomes more turbulent (an indorsing combination of the bulk flow with the border layers) and the border layers become thinner. as a result, the flow can pass through the gaps between the different louvers and transferable louvers. both effects supplement the heat transmission. for great reynolds numbers, the difference is about 10%. for reynolds numbers lower than 1000, the correlation lies within the error margin of the measured values. for low reynolds numbers, it can therefore be decided that there is no solid dependence on the louver and tube bank constraints. for the higher reynolds numbers, the difference increases, indicating the rising importance of parameters not present within the correlation. it is clear that the much smoother profile (fewer protruding edges in the flow path) as studied by will induce less vortex detaching then the profile studied here. of course, it must be prominent that no clear choice of validity can be proven for this correlation, as it was determined using samples with a continuous transversal and longitudinal fin pitch. therefore, additional research is compulsory to inspect the effect of various parameters (high reynolds numbers versus low reynolds numbers). the current research focused on reynolds numbers fluctuating from 250 to 1300. this corresponds to an inlet velocity of 0.5–2.8 m/s. this heat exchanger usually functions amongst 0.95 m/s and 1.7 m/s, so the operating range is well covered. measurements were taken to a reynolds number as low as 100, the sharp drop in convection coefficient measured for reynolds numbers between 100 and 250 is probably due to a combination of these effects. more study is required to improve understanding for this low reynolds area. the friction characteristic was fixed using a series of differential pressure measurements. the pressure drop was measured for a range of reynolds numbers. the resulting error is shown as well in figure 12. the results were associated with the correlation for plain fins [18]. this correlation predicts for great reynolds numbers a friction factor only 10% lesser than the dignified values. figure 11: reserved values of colburn factor versus air side reynolds number compared to forecast values by the correlation for plain fins and the correlation for convex louvered fins [18]. review on heat transfer enhancement by louvered fin 69 figure 12: restrained values of friction factor against air side reynolds number compared to expected values by the correlation for convex louvered fins (re>1000) [18]. for the small reynolds numbers, the plain fin correlation forecasted friction factors up to 77% larger than the calculated values. this specifies that the connection for plain fins cannot be used for comparison, as the longitudinal tube pitch lies outside the range of verified parameters. if the correlation distributed for reynolds numbers greater than 1000 are estimated for lower reynolds numbers, the two friction curves remain to parallel up to a reynolds number of 800, after which they diverge. the fin has a clearly more open construction than the previously established type (by using louvers in its place of v-shaped interruptions channels are designed allowing for the flow to permit more easily), which should decrease the pressure drop. nevertheless, the better disposition results in larger recirculation zones, and the mirrored rearrangement louvers increase form drag. as renowned, the correlation of disregards fin parameters and was built using samples having quite different parameters, so it is difficult to control the range of its validity [18]. 5.2 variable louver angle heat exchanger for a typical fin-and-tube heat exchanger, the controlling thermal resistance is generally on the air or fin side. therefore, to efficiently recover the complete enactment of the heat exchanger, highly enhanced surfaces on the fin side are often fulfilled in the application. webb [19] delivers a review of the printed data and correlations. louver fin geometry is used extensively for heat transmission to the air in automotive and room air conditioning heat exchangers such as radiators, condensers, and oil coolers. the first dependable printed data on louvered fin surfaces was in 1950 by kays and london [20]. in the 1980s, davenport [21, 22] worked with smoke trace studies on a tentime scale model of a non-standard variant of the crenulated louvered fin geometry and established the heat transfer and friction correlations for the crenulated louvered fin geometry. webb and trauger [23] worked with visualization techniques to investigate the link between the flow arrangement and the geometrical parameters of the louver angle, louver pitch, and fin pitch. it was found that the degree of flow alignment at a given reynolds number is improved as the fin-to-louver pitch ratio is reduced. jang et al., [24] mathematically examined three-dimensional convex louver finned-tube heat exchangers. the effects of different geometrical parameters, including convex louver angles (h = 15.5, 20.0, 24.0), louver pitch (lp = 0.953 mm, 1.588 mm), and fin pitch (8 fins/in., 10 fins/in., 15 fins/in.) are examined in detail for the reynolds number reh ranging from 100 to 1100. it was presented that, for equal louver pitch, both the average nusselt number and pressure drop coefficient are improved as the louver angle is improved; while for equal louver angles, they are reduced as the louver pitch is improved. in this study, the 3-d thermalhydraulic examination with movable louver angle of louver fins heat exchangers. it has been tested five models (ae) having continuously improved or reduced louver angle patterns. in figure13the case models of verified heat exchangers. the heat transfer and pressure drop appearances for different models construed by colburn factor j and friction factor f. islam et al., (2021): international journal of engineering materials and manufacture, 6(1), 60-80 70 figure 13: different case models of heat exchanger [25]. it has been seen from this study that at reynolds number 1075, the temperature gradient is more distinct for larger louver angle that is the greater heat transfer performance for large louver angle. nevertheless, a greater louver angle would also donate to the rise in the pressure drop. it is also found that the temperature gradient is higher for sequentially variable louver angles than identical angles. it is also showed that together nusselt number nu and pressure drop coefficient cp for continually movable louver angles (cases a–d) are higher than those for the identical louver angle (case e). it is seen that border layers exist on both the upper and lower faces of the louvers at reynolds number 1075. the significant heat transfer improvement is due to stripper boundary layers that form at the leading edge of each louver. the current results indicated the consecutively variable louver angle patterns applied in heat exchangers could effectively improve the heat transfer presentation. 6 vortex generators 6.1 delta winglet vortex generators every day large amounts of heat are transferred in many industrial and domestic processes. as a result, any performance increase of the heat transfer will have a significant impact on energy use, fuel consumption, and the resulting greenhouse gas emissions. more energy-efficient heat exchangers like louvered fin and round tube heat exchangers thus help to meet the 20–20–20 climate and energy targets set by the european union [26]. in this procedure, the mentioned geometry with vortex generator is shown in figure 14. the flat landing stage and evolution part are chosen as the span wise dimensions of in [27], as 0.25lp for the smallest flat landing and 0.5lp for the transition part. episodic settings are applied on both sides of the domain as well as on the top and bottom. the height of the computational domain is equal to the fin pitch fp and the width is equal to transversal tube pitch pt. the fin surface is positioned in the centre with half fin positioning beyond the fin surface and half fin spacing underneath. the entry length upstream of the fin equivalents to 5 times the fin pitch fp and the dominion prolongs 7 times the tube diameter do downstream of the fin. the sizes of the multifarious heat exchanger are listed in table 3. the louver geometry, tube diameter, and tube pitches are nominated from the databank with louvered fin heat exchangers provided. the results are designed in figure 15. for the highest reynolds numbers the simulated friction factors do not fall within the uncertainty of the experimental measurements: the maximum over prediction is 10%. in general, there is an acceptable match between the simulations and the experiments within the considered uncertainty ranges (the mean deviation of the colburn jfactors is 6.2% and of the friction factors 5.5%). the colburn j-factors and friction factors are designed for the purpose of the reynolds number redh in figure 16. the reynolds number range 140–1220 matches up to inlet velocities of 0.63–5.25 m/s. figure 16(a) illustrates that the colburn j-factor rises when delta winglets are used. the maximum increase is 16% compared to the baseline geometry (at redh = 600). however, as is clear from figure 16(b), the delta winglets also cause a penalty in friction factor (up to 35% at the largest reynolds number (redh = 1220)). review on heat transfer enhancement by louvered fin 71 table 3: size dimensions of the multifarious heat exchanger (dw = delta winglet) [27]. parameters symbol value outer tube diameter dₒ (mm) 6.75 fin thickness tf(mm) 0.12 louver pitch lp (mm) 1.50 louver angle θ (°) 35 fin pitch fp (mm) 1.71 transversal tube pitch pt (mm) 17.6 longitudinal tube pitch pl(mm) 13.6 stream wise delta winglet position δx (mm) 0.5dₒ span wise delta winglet position δz (mm) ±0.3dₒ dw angle of attack α (°) 35 dw height h (mm) 0.9s dw base b (mm) 2h; 1.5 h figure 14: (a) three-dimensional computational domain& (b) top view showing the delta winglet position [27]. figure 15: comparison between the experimental data and the simulation results: (a) colburn j-factors and (b) friction factors [27]. islam et al., (2021): international journal of engineering materials and manufacture, 6(1), 60-80 72 figure 16: comparison of (a) the colburn j-factor and (b) the friction factor for the baseline geometry without delta winglets and the compound design with delta winglets [26]. 7 compact heat exchenger 7.1 compact heat exchanger with louvered fins as the demand for heat exchangers is rapidly increasing by production industries that are more capable, compact, and less costly, heat transfer enhancement has multiplied with great impetus. thus, engineers come out with one wonderful solution, at which one revolution device has been developed decades ago called compact heat exchanger (che). hence, compact heat exchangers are capable to transfer further energy in a very limited cost method than other types of heat exchangers with more energy-saving when compared to conventional technology [19, 28–29]. this study enclosed the examination, imitation, and the investigation of modifications in geometrical factors modifications of louvered fin compact heat exchanger, che. figure 17 shows the physical prototypical and computational dominion for the louvered fin che. for simple evidence, louver design is usually a design like a window with plane slats at which each one of the quadrilateral platters from figure 17 is considered with some disposition angles. this louver design is used alongside the fin of the che. in every coating of the fin, the configuration is planned as in figure 18 to develop the performance of heat elimination as the fin design plays the prime role in creating the utmost efficiency of the che. also, the movement for each instance will be presumed as a laminar flow for inlet air velocity ranged from 0.3 m/s to 15 m/s. as for this study, the enactment of louvered fin che on the thermal and hydraulic investigation is estimated by variable louver angle and fin pitch. figure 17: (a) the physical model (2d view in x-y plane) and (b) computational domain [30]. review on heat transfer enhancement by louvered fin 73 figure 18: five altered cases of consecutively improved and reduced louver angle (+2◦, +4◦, −2◦, −4◦, and uniform angle 20◦) [30]. to examine the effect of fin pitch on heat transfer performance of louvered fin che, the louver angle selected is immovable at 20◦ throughout along the fin but the fin pitch is now selected to be movable. it consists of three variables which are (1) case a (fin pitch = 1.0 mm); (2) case b (fin pitch = 2.0 mm); (3) case c (fin pitch = 4.0 mm). for each situation, the other measurements of the che are being permanent as indicated below. louver-pitch (1.00 mm); fin-thickness (0.05 mm); flow-length (9.00 mm); inlet air temperature (tin) (20◦c); inlet air pressure (pin) (0.0 pa); fin wall temperature (tw) (60◦c); frontal-velocity (uin) (0.3∼15 m/s); louver-angle (uniform angle of 20◦); for all circumstances of louvered fins of che considered, it is observed that the higher temperature section arises nearby the louvers at flow presence while the smallest temperature occurs in the region near the flow arrival regions. figure 19 shows the temperature supply of constant louver angle (20◦) with fin pitch of 1 mm (case a) at re = 500 renderings to the occurrences defined above. therefore, greater heat transfer performance is expected for a louvered fin with minor pitch. it may be presumed from figure 20; that the lowest fin pitch (case a) produces greater values of nu compared to case b and c. the reason why louvered fin with minor pitch provides improved heat transfer performance equated to the larger one is that the louver with minor pitch caused more turbulence inflow of the working fluid and the border layer comparative to the fundamental flat-plate surfaces [30]. islam et al., (2021): international journal of engineering materials and manufacture, 6(1), 60-80 74 figure 19: temperature delivery along the flow direction for identical louver angle (20◦) with fin pitch of 1 mm (case a) and re = 500 [30]. figure 20: the deviation of nu along the flow direction for variable fin pitch with uniform louver angle of 20◦ and re = 500 [30]. the averaged nusselt number (nu) delivery with reynolds number for altered fin pitch values (cases a–c) is shown in figure 21. it may be understood that as the reynolds number rises, nu for all the cases inspected also rises closely linearly. this is as the reynolds number is improved by growing the inlet velocity. as a consequence, there will be an increase in fluid velocity inside the flow over the fins. therefore, this increase bothers the flow, and the heat transmission is reinforced when the reynolds number is greater than before. from this figure, it is observed that the nu for case a is the highest followed by cases b and c at all numbers of reynolds number. the difference in nu between the cases a–c is more apparent at a higher reynolds number. this is as, at developed reynolds number, the border layers are thinner and the flow itself is almost allied with the louvers which cause the difference among cases a-c to be more substantial [30]. review on heat transfer enhancement by louvered fin 75 7.2 compact louvered heat exchanger this study has achieved an investigational study on automobile radiators to explore air-side heat transfer and pressure drop appearances of flow on louvered fins. here have been performed tests for irregular and regular arrangements of louvers which have shown in figures 22, 23 respectively. thermal hydraulic performance of radiator has examined for various geometrical and flow parameters and experimental results compared with effectiveness ntu results. it has been found that heat transfer rate tends to increase with an increasing inlet air velocity but at the same velocity the symmetrical pattern has a higher heat transfer rate than asymmetrical. the reason is that the regular pattern has more louvers per tube and the more the number of louvers with small pitch are the extra common areas between the fluid flows. by increasing air velocity, the pressure drop in the airside will be increased but the symmetrical pattern louvered fin behaves better in pressure drop performance. in the same conditions of temperature and mass flow rates for inlet air and water, the cooling rate of outlet water and heating rate of an outlet air temperature of a regular pattern is greater than an irregular one. the overall conclusion obtained from the above work is that regular louver fin organization found best in thermal-hydraulic performance than irregular organization hence it is vital to study geometrical constraints and physical structure of heat exchanger in order to enhance performance. figure 21: variation of averaged, nu versus re for variable fin pitch with uniform louver angle of 20◦ [30]. figure 22: asymmetrical arrangement of louvers [2]. islam et al., (2021): international journal of engineering materials and manufacture, 6(1), 60-80 76 figure 23: symmetrical arrangement of louvers [2]. 8 summary it has shown from figure 24 the greatest heat transfer enhancement is achieved approximately 118%for the louver fin heat exchangers with variable louver angle compared with general devices. the average value of heat transfer enhancement we studied about 58% for the multi-row fin and tube heat exchanger compared with regular devices. the minimum value of heat transfer enhancement is 9.3% for the compact louvered heat exchanger compared with general devices. table 4: observation of recent investigations on various types of louver fin at different working conditions in term of heat transfer enhancement. louver type louver arrangement ref. working fluid conditions observations single louvered fins single and double row tubes with louvered fins [4] air reynolds number from 400 to 4000. temperature s of the tube surface and inlet air maintained at 358k and 288k, respectively (1) the local nusselt number on the top surface of each louver in the flow direction along the length of fin for reynolds number red = 1000 is acquired. (2) the heat transfer coefficient was increased with the louver angle and reached a maximum value at 28-29 ◦ and then again decreased with the increase in louver angle for fin pitch value of 2.17 mm. (3) the higher heat transfer coefficient value is observed at a smaller louver pitch value of 0.81 mm at optimal louver angle. louvered fin and tube heat exchanger [5] air with constant properti es variation of reynolds number from 1250 to 8100 (1) in this study established correlations can describe 100% and 86% of totally 186 numerical simulation data within ±15% respectively in the extensive ranges of constraints. (2) the optimal louver angle was 21° for maximum increasing colburn factor and minimizing friction factor was gained by genetic algorithm using the developed correlations. review on heat transfer enhancement by louvered fin 77 multi louvered fins multi row fin and tube heat exchanger [6] air the range of reh numbers within 70-350. in this experiment, the increment in heat transfer performance of 58% was acquired with reh = 350 when using louvered fin in place of flat fins. multi-region louver fins and flat tubes heat exchanger [14] air reynolds numbers of 400–1600 (1) the results show that the louver fin with 4 regions and the louver fin with 6 regions are far better than the conventional fin in overall performance. (2) at the same time, the louver fin with 6 regions is also better than the louver fin with 4region. multilouvered fin and flat tube heat exchanger [16] air and water reynolds numbers of 100–600. velocity, of 100–600 water flow rate 0.32 m 3 /h. (1) in this part when used 16 mm flow depth then the heat transfer coefficients do not change much with louver angle. (2) on the other side, for 24 mm flow depth, the heat transfer coefficients rise with louver angle and maximum at 27° and again fall with louver angle. (3) and the friction factors rise with louver angle, the j factor rises with louver angle, but its effect on the j factor differs with flow depth. inclined louvered fins inclined louvered fin heat exchanger [18] air reynolds numbers varying from 250 to 1300 (1) in this study, the fin pattern is observed to have a greater friction factor (on average 18%) and convective heat transfer coefficient (on average 10%) for reynolds numbers >1000. (2) for reynolds numbers lower than 1000 the convex louvered correlation slightly over predicts the measured value, but the prediction lies within the error margin. variable louver angle heat exchanger [25] air reynolds number reh (based on the fin spacing and the frontal velocity) ranging from 100 to 1100. (1) when reynolds number is 1075, the temperature gradient is more prominent for a higher louver angle that is the greater heat transfer performance for large louver angle. (2) in case a (+2), case b (+4), case c (2) and d (4), the supreme heat transfer development inferred by j/j0 are 115%, 118%, 109% and 107%, and the corresponding friction factor ratio f/f0 are 116%, 119% 110% and 108%, correspondingly. (3) and the area fall ratios are all enlarged for five different cases of sequentially increased or decreased louver angle compared to plain fin surface and the extreme area reduction for case b (+4) can reach up to 25.5% vortex generators delta winglet vortex generators [27] air the reynolds number range 140– 1220 (1) the maximum increase is 16% compared to the baseline geometry (at redh = 600). (2) in this study delta winglets also create a detriment in friction factor {up to 35% at the largest reynolds number (redh = 1220)}. compact heat exchanger louvered fin compact heat exchanger [30] air reynolds number ranged from 100 to 1000. (1) here the highest value of the nusselt number for case b (+4 ◦ ). (2) in here the nusselt number and pressure drop coefficient increase with decreasing with fin pitch and increasing with reynolds number. here enhancement of heat transfer for minimum fin pitch (1 mm) is more specious at large reynolds number. islam et al., (2021): international journal of engineering materials and manufacture, 6(1), 60-80 78 compact louvered heat exchanger [2] air 2300 < re < 5000000 (1) results showed that when used symmetrical arrangement of louvered fins give a 9.3% of increment in heat transfer performance and an 18.2% minimization in pressure drop than the irregular organization of louvered fin. (2) for a constant rate of heat transfer and pressure drop, a 17.6% minimization of fin mass is perceived for the symmetrical arrangement of fins. the outcomes from this study designate that the arrangement of the louvered fins has the main influence on the heat transfer and pressure drop from that louver. figure 24: graphical representation of comparison of heat transfer enhancement of various enhancement types. 9 conclusions different kinds of louver patterns have been tested by researchers through its experimental and numerical studies. the heat transfer coefficient and pressure drop are two important characteristics used to optimize the thermal hydraulic performance of the louver fin heat exchanger. optimum heat exchanger bears maximum heat transfer coefficient and minimum pressure drop characteristics. the effects of various geometrical parameters such as louver pitch, louver regions, louver angle, louver numbers, louver height, and flow parameters like air velocities are considered on the performance of louvered fin heat exchanger. the main findings of this present review can be described as follows: 1) when we studied multi louvered fin, in this segment for multi-row fin and tube heat exchanger, an increase in heat transfer enhancement is found 58% for reh = 350. 2) in vortex generators for delta winglet vortex generators, the extreme enhancement of heat transfer increased to 16% compared to the baseline geometry (at redh = 600). 58% 16% 18% 118% 9.3% 0 20 40 60 80 100 120 140 mrfthe dwvg ilfhe vlahe clhe h e a t t r a n s f e r e n h a n c e m e n t ( % ) reference [6] [27] [18] [25] [2] review on heat transfer enhancement by louvered fin 79 3) for inclined louvered fin heat exchanger, the studied fin pattern is found to have a greater enhancement on average 18% for reynolds numbers lower than 1000. 4) for variable louver angle heat exchanger, the maximum heat transfer improvement achieved by 118%reynolds number at 1075. 5) when we studied compact louvered head exchanger the results showed that symmetrical arrangements of louvered fins give a 9.3% heat transfer enhancement. references [1] r.k. shah, d.p. sekulic (2003), fundamentals of heat exchanger design, john wiley & sons, 2003. [2] a vaisi, m esmaeilpour and h. taheria (2002). experimental investigation of geometry effects on the performance of a compact louvered heat exchanger, applied thermal engineering, 31, 2011, 33373346. manhoe kim and clark w bullard (2002). [3] a.a. antoniou, m.r. heikal, t.a. cowell (1990), measurements of local velocity and turbulence levels in arrays of louvered plate fins, in: proceedings of the ninth international heat transfer conference, jerusalem, 1990, pp. 105–110. [4] v p malapure, sushanta k mitra, a bhattacharya (2007). numerical investigation of fluid flow and heat transfer over louvered fins in compact heat exchanger, international journal of thermal sciences, 46, 2007, 199–211. [5] ali sadeghianjahromia, saeidkheradmanda, hossainnematib (2018). developed correlations for heat transfer and flow friction characteristics of louvered finned tube heat exchangers, international journal of thermal sciences, 129, 2018, 135–144. [6] čarija z., franković b., perčić m., čavrak m. (2014). heat transfer analysis of fin-and-tube heat exchangers with flat and louvered fin geometries, international journal of refrigeration, 2014. [7] c.j. davenport (1980), heat transfer and fluid flow in louvered triangular ducts, ph.d. thesis, department of mechanical engineering, lanchester polytechnic, 1980. [8] c.j. davenport (1983), correlation for heat transfer and friction characteristics of louvered fin, aiche symposium series 79 (25), 19–27, 1983. [9] a. achaichia (1987), the performance of louvered tube-and-plate fin heat transfer surface, phd thesis, department of mechanical and production engineering, brighton polytechnic, 1987. [10] a. achaichia, t.a. cowell (1988), heat transfer and pressure drop characteristics of flat and louvered plate fin surface, experimental thermal and fluid science 1,1988, 147–157. [11] z. huihua, l. xuesheung (1989), the experimental investigation of oblique angles and interrupted plate lengths for louvered fins in compact heat exchangers, experimental thermal and fluid science 2,1989, 100–106. [12] h. aoki, t. shinagawa, k.k. suga (1989), an experimental study of the local heat transfer characteristics in automotive louvered fins, experimental thermal and fluid science 2, 1989, 293–300. [13] j.p. rugh, j.t. pearson, s. ramadhyani (1992), a study of a very compact heat exchanger used for passenger compartment heating in automobiles, asme symposium series htd 201,1992, 15–24. [14] wei li and xialing wang (2010). heat transfer and pressure drop correlations for compact heat exchangers with multi-region louver fins, international journal of heat and mass transfer, 53, 2010, 2955-2962. [15] dragiantonijevic (2012). an engineering procedure for air side performance evaluation of flat tube heat exchangers with louvered fins, heat mass transfer (2013), 49, 2012, 117–127. [16] air-side thermal hydraulic performance of multi louvered fin aluminum heat exchangers, international journal of refrigeration, 25, 2002, 390-400. [17] t.p. wenzel, j.g. koomey, j.g. rosenquist, m. sanchez, j.w. hanford (1997), energy data sourcebook for the us residential sector, lbl-40297, lawrence berkeley national laboratory, 1997. [18] c. t joen, h.-j. steeman, a. willockx, m. de paepe (2006). determination of heat transfer and friction characteristics of an adapted inclined louvered fin, experimental thermal and fluid science, 30, 2006, 319–327. [19] r.l. webb (1994), principles of enhanced heat transfer, john wiley and sons, new york, 1994. [20] w.m. kays, a.l. london (1950), heat transfer and flow friction characteristics of some compact heat exchanger surfaces-part i: test system and procedure, trans. asme 72, 1950, 1075–1085. [21] c.j. davenport (1980), heat transfer and fluid flow in louvred triangular ducts, ph.d. thesis. cnaa, lanchester polytechnic institute, england, 1980. [22] c.j. davenport (1983), correlations for heat transfer and flow friction characteristics of louvred fin, aiche symposium series, 1983, pp. 19–27. [23] r.l. webb, p.a. trauger (1991), flow structure in the louvred fin heat exchanger geometry, exp. therm. fluid sci. 4 (1991) 205–217. [24] j.y. jang, k.p. shieh, h. ay (2001), 3-d thermal-hydraulic analysis in convex louver finned -tube heat exchangers, ashrae annual meeting, cincinnati, oh, usa, june 22–27, 2001, pp. 501–509. [25] ching-tsun hsieh and jiin-yuh jang (2006). 3-d thermalhydraulic analysis for louver fin heat exchangers with variable louver angle, applied thermal engineering, 26, 2006, 1629-1639. [26] european union, the eu climate and energy package, information collected from:<http://ec.europa.eu/clima/policies/package/index_en.htm>. islam et al., (2021): international journal of engineering materials and manufacture, 6(1), 60-80 80 [27] h. huisseune (2011). performance evaluation of louvered fin compact heat exchangers with vortex generators, ph.d. thesis, ghent university, gent, belgium, 2011. [28] p. gunnasegaran, n. h. shuaib, m. f. abduljalal, and e. sandhita (2012), “numerical study of fluid dynamic and heat transfer in a compact heat exchanger using nanofluids,” isrn mechanical engineering, vol. 2012, article id 585496, 11 pages, 2012. [29] k. y. leong, r. saidur, s. n. kazi, and a. h. mamun (2010), “performance investigation of an automotive car radiator operated with nanofluid-based coolants (nanofluid as a coolant in a radiator),” applied thermal engineering, vol. 30, no. 17-18, pp. 2685–2692, 2010 [30] p. gunnasegaran, n. h. shuaib and m. f. abdul jalal (2012). the effect of geometrical parameters on heat transfer characteristics of compact heat exchanger with louvered fins, international scholarly research network isrn thermodynamics, volume 2012, article id 832708, 10 pages. international journal of engineering materials and manufacture (2019) 4 (2) 77-84 https://doi.org/10.26776/ijemm.04.02.2019.05 h.m.shivaprasad 1 , g.giridhara 1 , v.arunkumar 2 1 b.m.s.college of engineering, bull temple road, bangalore-560 019 2 dr.ambedkar institute of technology, outer ring road, bangalore-560 056 e-mail: shivaprasad.mech@bmsce.ac.in reference: h. m. shivaprasad, g. giridhara, v. arunkumar (2019). static stiffness parametric studies of newly conceptualized inter shaft squeeze film damper (issfd) rings. international journal of engineering materials and manufacture, 4(2), 77-84. static stiffness parametric studies of newly conceptualized inter shaft squeeze film damper (issfd) rings h. m. shivaprasad 1 , g. giridhara 1 , v. arunkumar 2 received: 25 march 2019 accepted: 09 may 2019 published: 20 june 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract most of the modern gas turbine engine designs requiring super critical operations will often have squeeze film dampers (sfds) on the high pressure spool bearing as an inevitable feature. however, squeeze film dampers are not very common for inter-shaft bearing applications and are still in the research and development stage. the current effort concentrates on static stiffness parametric studies based on newly conceptualized intershaft squeeze film damper (issfd) ring design suitable for space constrained intershaft bearing application of a typical two spool configured system. the work involves static stiffness evaluation of three and four grooves issfd rings by varying the groove angle/groove length/subtended angle of groove & hence the overlapping angle of grooves by conducting static tests on a dedicated static stiffness evaluation test rig designed and fabricated for the purpose. the pattern of circumferential variation of stiffness of each ring is studied and the results revealed a typical trend of decreasing stiffness in issfd ring with the increase in groove angle and hence the overlapping angle of grooves. the static stiffness parametric studies has resulted in developing an ideal profile of issfd ring having six grooves that exhibited axisymmetric pattern of circumferential variation of stiffness. when used in a space constrained intershaft bearing plane of a typical two spool gas turbine engine, the ideal issfd ring profile would exhibit the best damping performance. keywords: inter shaft squeeze film damper (issfd), gas turbine engine, static stiffness, two spools, grooves. 1 introduction a squeeze film damper (sfd) is essentially a simple device consisting of an oil film interposed between the nonrotating outer race (sleeve) of a rolling element bearing and its housing. sfds are lubricated elements providing viscous damping in mechanical systems. they help in dissipation of vibration energy, isolation of structural components and improve the dynamic stability characteristics of inherently unstable rotor-bearing systems. for the high speed turbo machine rotors to work closer to critical speeds, damping is essential. off late, sfds have become very essential components of high speed turbo machinery because of their simplicity in design and high potential to deliver desired level of damping. while applications of sfd has become very common, the necessity of the same in an inter-shaft bearing plane has still not been realized from practical application point of view. it is observed that, in real practical sense, there is lot of potential for the development of newer versions of sfd design suitable for a space constrained intershaft bearing plane of two spool configured system. also, most of the work that is reported in the past doesn’t look to be feasible from practical application point of view of a typical space constrained gas turbine engine setup and the unavailability of sfd design for an intershaft bearing plane still continues. the concept of squeeze film damping is explained by luis san andres [1] and he has shown the necessity of squeeze film dampers along with the applications. he has explained various models of squeeze film dampers with design criteria and the recent developments in the domain of squeeze film dampers. gupta, et al. [2] tested an improved intershaft squeeze film damper (issfd) by considering two design modifications for analysis and tested them experimentally. zeidan, et al. [3&4] highlighted the advantages of squeeze film dampers and reported that over damped condition of the supports would reduce the effective damping in high speed rotating machinery. elshafei, et al. [5, 6, 7 & 8] showed that the intershaft squeeze film damper is unstable above the engine’s first critical speed. they have reported that the intershaft dampers are stable super critically only in a configuration in which the oil film does not rotate. e. j. gunter, et al. [9] reported that the effective stiffness and damping coefficients can be mailto:shivaprasad.mech@bmsce.ac.in static stiffness parametric studies of newly conceptualized inter shaft squeeze film damper (issfd) rings 78 determined using the values of rotor amplitude, phase angle and unbalance forces for a rigid rotor. m. jayaraman and v. arunkumar [10] have introduced the concept of flexible supports or flexible mounts which are mounted in between the bearing and the shaft in order to reduce excessive vibration levels in the machinery. h. m. shivaprasad and g. giridhara [11] conducted preliminary studies on newly conceptualized inter-shaft squeeze film damper (issfd) rings having desired number of discontinuous grooves in the annular space. to overcome the limitations and problems associated with the existing sfd models for intershaft bearing application, they have proposed new versions of issfd rings having circumferential grooves of very thin width which actually represents the squeeze oil film thickness. in a real practical sense, they have proposed a compatible component facilitating the radial squeezing mechanism, where squeeze film oil could be introduced, thus resulting in squeeze film damping. their simulation result and experimental result with regard to static stiffness value correlate well. hibner, et al. [12&13], alderson, et al. [14], qihan li, et al. [15&16], j.b. courage [17], shende, et al. [18] and many more researchers have reported their work related to intershaft squeeze film dampers. in this research work, static stiffness parametric studies based on newly conceptualized issfd ring design [11] is carried out by varying the geometric parameters viz., number of grooves, groove angle/groove length/subtending angle of groove and hence the overlapping angle of grooves. as such an attempt has been made here to develop practically feasible, ideal profile of issfd ring, suitable for intershaft bearing of a typical space constrained, two spool gas turbine engine. figure 1 shows the schematic of a typical two spool configured gas turbine engine. when mounted on intershaft bearing (bearing-4), an ideal issfd ring profile would exhibit the best damping performance and effectively attenuate vibrations amplitude in the intershaft bearing plane. figure 1: schematic of a typical two spool configured gas turbine engine 2 background an issfd ring is essentially designed to deform when a radial load is applied. when the circumferential variation of stiffness of issfd ring follows axisymmetric pattern, circumferential deformation of the ring will be axisymmetric. under axisymmetric pattern of circumferential deformation of the ring, squeezing of oil film will have axisymmetric pattern and hence the damping effect created by such an issfd ring will be very effective. under working conditions, an issfd ring with axisymmetric pattern of circumferential variation of stiffness would provide effective damping as the absorption of kinetic energy of the moving surfaces would happen in an axisymmetric pattern. therefore it is necessary to develop an issfd ring profile that exhibits axisymmetric pattern of circumferential variation of stiffness. with this background, static stiffness parametric studies is carried out with an intention to develop an ideal issfd ring profile that exhibits axisymmetric pattern of circumferential variation of stiffness. 3 manufacture of issfd rings for parametric studies, two sets containing four issfd rings in each set, one with three number of grooves and another with four number of grooves are fabricated by varying the geometric parameters and taken up for studies. the dimensions on issfd ring that would fit a typical two spool small gas turbine engine are chosen as; 68 mm outer diameter, 62 mm inner diameter and 20 mm width along the shaft axis. considering the radial thickness of the ring and after deliberations, the width/thickness of oil grooves is appropriately chosen as 0.3 mm. figure 2a shows the profile drawing of three grooves issfd ring with 135°groove angle. the groove angles considered for three grooves issfd rings are 135°, 150°, 165° and 180° that gives overlap angles of 15°, 30°, 45° and 60° respectively. the groove angle/groove length/subtended angle of groove and hence the overlapping angle of grooves is appropriately increased in steps of 15°, essentially to study the circumferential variation of stiffness. figure 2b shows the profile drawing of four grooves issfd ring with 105° groove angle. the groove angles considered for four grooves issfd rings are 105°, 120°, 135° and 150° that gives overlap angles of 15°, 30°, 45° and 60° respectively. here also the groove angle /groove length/subtended angle of groove and hence the overlap angle of grooves is h. m. shivaprasad et al., (2019): international journal of engineering materials and manufacture, 4(2), 77-84. 79 increased in steps of 15°. spring steel is selected as the material for issfd rings considering its high yield strength and capability to regain its original shape despite significant deflection. the rings are fabricated by carrying out cnc turning operation and wire edm processes. stress relieving is done to relieve the internal residual stresses developed during the machining process. figure 3 shows the photographs of sequence of operations performed during the fabrication of issfd rings. 4 static test rig the static test rig facilitates loading of the issfd ring and measurement of deflection along the load line. the main components of static test rig are; base plate, frame, two v-blocks, a mandrel for mounting of issfd ring, loading unit, load cell and a digital dial indicator. figure 4 shows different views of static test rig where in a mandrel along with the issfd ring is supported between two v-blocks which are mounted on the base plate. the loading unit includes the screw rod arrangement which is manually operated to apply load. the load cell connected to the loading unit measures the load applied on the ring. a digital dial indicator connected to the loading unit measures the deflection of the issfd ring. (a) 3 grooves-135° (b) 4 grooves-105° figure 2: drawings of 3&4 grooves issfd rings showing variation of groove angle (a) cnc turned component (b) groove cutting by wire edm (c) finished ring after drilling holes by edm figure 3: photographs showing sequence of operations performed during the fabrication of issfd rings figure 4. views of static test rig 1mandrel, 2 gantry, 3 screw rod, 4 screw rod nut, 5 – screw rod plate, 6 – bearing housing, 7 – load cell pin 8 l-plate, 9 – base plate, 10 – top cover, 11 – u handle, 12 – load cell, 13 – v block, 14 – issfd ring static stiffness parametric studies of newly conceptualized inter shaft squeeze film damper (issfd) rings 80 4.1 methodology of measurement  starting from the beginning of a groove, in steps of 15o, issfd ring is marked for the entire groove angle in radial direction along the length of groove using a height gauge and indexing head of milling machine. figure 5a shows the graphical representation of load line and marking of angular positions for three grooves issfd ring with 180°groove angle. figure 5b shows the photograph of a typical issfd ring with marked angular positions.  the mandrel along with the issfd ring is supported between two v-blocks which are mounted on the base plate and issfd ring is placed below the loading unit.  the screw rod is slowly rotated through hand wheel and thereby load is slowly applied in steps on the issfd ring and corresponding deflection of groove/slot is noted down at every marking created at intervals of 15°on the ring.  circumferential variation of stiffness at different marked positions is calculated by finding the slope of load vs deflection.  the response of stiffness vs groove angle gives a sense of circumferential variation of stiffness of issfd ring. 5 results and discussions experiments, parametric in nature were conducted to evaluate the stiffness offered by the issfd rings under static condition. the measurement values of load and deflection for all the angular positions of issfd rings at intervals of 15° are noted for each of the ring and the response of load vs deflection is plotted. to have accurate measurements, repeatability of the readings is ensured. figure 6a indicates the typical load deflection pattern for a three grooves issfd ring with 180° groove angle. it is observed that after a certain level of loading, there is no increase in the value of deflection at certain positions of groove and a close observation has revealed that it is due to closing of the groove happening under the applied load. figure 6b shows circumferential variation of stiffness up to 120° position. one can observe decreasing trend in stiffness from 0° to 60° position because of overlapping of grooves that has resulted in lesser stiffness and at 90° position of the groove, there is slight increase in stiffness as a result of single groove. almost, a mirror image of 0° to 45° circumferential variation of stiffness is seen from 45° to 90° and the maximum stiffness values are found at 0° and 90° positions of the groove. circumferential variation of stiffness at different marked positions is calculated and tabulated. table 1 provides the relevant values of stiffness. similar patterns are observed for all the other three grooves rings and similar reasons justify the patterns. figure 7a and figure 7b show the relevant results obtained for three grooves rings with different groove angles. (a) (b) figure 5: (a) graphical representation of load line & marking of angular positions for 3-grooves issfd ring with 180° groove angle and (b) photograph of a ring with marked angular positions (a) load v/s deflection pattern (b) circumferential variation of stiffness up to 120° figure 6: details of the results for 3grooves issfd ring with 180° groove angle h. m. shivaprasad et al., (2019): international journal of engineering materials and manufacture, 4(2), 77-84. 81 table 1: stiffness values for 3grooves issfd ring with 180° groove angle 3 grooves issfd ring with 180° groove angle (average k= 2508.86 n/mm) loading line position 0° 15° 30° 45° 60° 75° 90° 105° 120° stiffness (n/mm) 3373.61 2637.7 2 2204.9 0 2085.7 4 2006.0 5 2356.9 6 3070.2 2 2766.9 6 2188.60 3-grooves ring, 135° groove angle 3-grooves ring, 150° groove angle 3-grooves ring, 165° groove angle figure 7a: load v/s deflection curves for 3grooves issfd rings. 3-grooves ring, 135° groove angle 3-grooves ring, 150° groove angle 3-grooves ring, 165° groove angle fig 7b: circumferential variation of stiffness up to 120° for 3grooves issfd rings. 4-grooves, 105° groove angle 4grooves, 120° groove angle 4-grooves, 135° groove angle 4-grooves, 150° groove angle fig 8a: load v/s deflection curves for 4grooves issfd rings 4-grooves, 105° groove angle 4grooves, 120° groove angle 4-grooves, 135° groove angle 4-grooves, 150° groove angle figure 8b: circumferential variation of stiffness up to 90° for 4 grooves issfd rings table 2: average stiffness values of 3 and 4 grooves issfd rings 3 grooves issfd ring 4 grooves issfd ring groove angle 135° 150° 165° 180° 105° 120° 135° 150° stiffness (n/mm) 3514.08 3045.13 2758.97 2508.86 2704.63 2691.04 2634.29 2592.88 static stiffness parametric studies of newly conceptualized inter shaft squeeze film damper (issfd) rings 82 5.1 comparative study of stiffness on three and four grooves issfd rings a comparative study of the average stiffness values of issfd rings revealed a typical decreasing trend in stiffness value with the increase in groove angle/groove length/ subtended angle of groove and hence the overlapping angle of grooves for three and four grooves issfd rings. table 2 shows the average stiffness values of issfd rings. figure 9 shows the variation of stiffness for three & four grooves issfd rings for different groove angles. by increasing the groove angle/groove length/subtended angle of groove and hence the overlapping angle of grooves of issfd ring, stiffness value is seen to be decreasing. this study has revealed; stiffness of an issfd ring is inversely proportional to groove angle/groove length/subtended angle of groove and hence the overlapping angle of grooves. figure 10a and figure 10b show graphical representation of circumferential variation of stiffness for three and four grooves issfd rings. it is observed that, except for the four grooves issfd ring with 120° groove angle to some extent, all the other rings didn’t exhibit axisymmetric pattern of circumferential variation of stiffness. it is also observed that when the overlapping angle of grooves for 3 grooves ring is around 50% and that for 4 grooves ring is around 66%, the circumferential variation of stiffness is tending to be symmetrical. therefore increasing the overlapping angle of grooves would increase the axisymmetric pattern of circumferential variation of stiffness. at the same time it is also observed that increasing the overlapping angle would decrease the overall average stiffness value of the issfd ring. 5.2 development of six grooves issfd ring with 130° groove angle after observing the circumferential variation of stiffness trend on three and four grooves issfd rings, a 6 grooves issfd ring is developed with a maximum possible 116% overlap angle of grooves and fabricated. figure 11a shows the typical drawing & the photograph, figure 11b shows load v/s deflection curves and figure 11c shows circumferential variation of stiffness up to 60° for issfd ring having six grooves with 130° groove angle. for all the angular positions, the deflection is seen to be uniform and the load v/s deflection curves are smooth. figure 11c shows a plot of circumferential variation of stiffness that is seen to be having symmetric pattern with the profile of the groove. higher stiffness values are observed at angular positions of 15° & 45°. one can clearly observe that this ring exhibited axisymmetric pattern of circumferential variation of stiffness. therefore from static stiffness perspective, this ring is selected as an ideal profile of issfd ring and would exhibit best damping performance in an intershaft bearing plane. the average stiffness value of six grooves issfd ring is found to be 1.6 mn/m. table 3 shows the relevant results. figure 9: stiffness variation with groove angle/groove length & overlap angle of grooves figure 10a: graphical representation of circumferential variation of stiffness for 3 grooves issfd rings h. m. shivaprasad et al., (2019): international journal of engineering materials and manufacture, 4(2), 77-84. 83 figure 10b: graphical representation of circumferential variation of stiffness for 4 grooves issfd rings (a) drawing & photograph of 6 grooves issfd ring with 130° groove angle. (b) load v/s deflection pattern (c) circumferential variation of stiffness up to 60° (d) graphical representation figure 11: details of the results for 6grooves issfd ring with 130° groove angle table 3: stiffness values for 6 grooves issfd ring with 130° groove angle 6 grooves issfd ring with 130° groove angle (average k= 1596.49 n/mm) loading line position 0° 15° 30° 45° 60° stiffness (n/mm) 1396.06 1879.20 1512.86 1811.06 1383.26 6 conclusions 1. two sets of newly conceptualized three and four grooves issfd rings with four rings in each set have been fabricated by varying the groove angle/groove length/subtended angle and hence the overlapping angle of grooves as parameters. the rings have been tested on a dedicated static stiffness evaluation test rig and circumferential variations of stiffness of the rings have been studied. 2. the results revealed a typical trend of decreasing average stiffness values of issfd rings with the increase in groove angle/groove length/subtended angle and hence the overlapping angle of grooves. 3. none of the three and four grooves issfd ring exhibited axisymmetric circumferential variation of stiffness. static stiffness parametric studies of newly conceptualized inter shaft squeeze film damper (issfd) rings 84 4. a third variety of issfd ring having six overlapping grooves with 130° groove angle is fabricated and circumferential variation of stiffness is evaluated and it exhibited axisymmetric pattern of circumferential variation of stiffness. 5. as an outcome of static stiffness parametric studies, the profile of six grooves issfd ring qualifies as an ideal issfd ring profile. however the choice could be validated by conducting parametric dynamic tests so that the ring with an ideal profile would exhibit the best possible damping performance in an intershaft bearing plane. acknowledgement this research was funded by b.m.s. college of engineering, bull temple road, bangalore-560 019. the authors are grateful to b.m.s. college of engineering management and r&d centre of b.m.s. college of engineering for providing all the facilities required for this research work. references 1. dr. luis san andres, notes 13-squeeze film dampers: operation, models & issues, 2010. 2. gupta, k., and samir chatterjee, (2011). theoretical analysis of improved designs of intershaft squeeze film damper for aero engine applications. proceedings of the national symposium on rotor dynamics, nsrd-2011, 19-21, 179-190. 3. zeidan, f., (1995). application of squeeze film dampers. turbo machinery international, vol.11, 50-53. 4. zeidan, f., l. san andrés, and j. vance, (1996). design and application of squeeze film dampers in rotating machinery. proceedings of the 25th turbo machinery symposium, turbo machinery laboratory, texas a&m university, 169-188. 5. el-shefai and r.v. eranki, (1994). dynamic analysis of squeeze film damper supported rotors using equivalent linearization. asme journal for gas turbines and power, 1994/7/1, vol.116, 682-682. 6. el-shafei, (1991). stability analysis of intershaft squeeze film dampers. journal of sound and vibration, 148(3), 395-408. 7. el-shafei, (1998). a new design of intershaft squeeze film dampers. proceedings of the vibration institute, 88, 15-23. 8. el-shafei, (1977). stable intershaft squeeze film damper. united states patent number 4,781,077. 9. e. j. gunter, l.e.barrett and p.e.allaire, (1977). design of nonlinear squeeze-film dampers for aircraft engines. journal of lubrication technology, vol. 99, issue 1, 57-64. 10. m.jayaraman and v.arun kumar, (2007). compact flexible support for rotor bearing systems. project document from national aerospace laboratory. 11. h.m.shivaprasad and dr.g.giridhara, (2018). preliminary studies of newly conceptualized intershaft squeeze film damper (issfd) rings. international journal of applied engineering research, issn 0973-4562 vol. 13(7), 3045310 12. hibner, d.h., kirk, r.h. and buono, d.f., (1977). analytical and experimental investigation of intershaft squeeze film dampers, part 1-demonstation of instability. journal of engineering for power, trans. asme, vol. 99, issue 1, 47-52. 13. hibner, d.h., bansal, p.n. and buono, d.f., (1978). analytical and experimental investigation of intershaft squeeze film dampers, part 2-control of instability. journal of mechanical design, trans. asme, vol. 100(3), 558-562. 14. alderson, r.g., (1986). instability of an intershaft squeeze film damper in a two-spool rotor dynamics simulator, rotor dynamic instability problems in high performance turbo machinery. national air and space administration conference publications 2443, 315-323. 15. qihan li, litang yan and j.f. hamilton, (1986). investigation of the steady-state response of a dual-rotor system with inter-shaft squeeze film damper. journal of engineering for gas turbine and power, trans. asme, volume 108(4), 605-612. 16. qihan li, and j.f. hamilton, (1986). investigation of the transient response of a dualrotor system with intershaft squeeze film damper. journal of engineering for gas turbine and power, trans. asme, volume 108(4), 613-618. international journal of engineering materials and manufacture (2021) 6(4) 242-258 https://doi.org/10.26776/ijemm.06.04.2021.02 almeida, j. f. , mourarias, m. n., gerolamo, m. c. and coelho, r. t. department of production engineering, são carlos school of engineering, university of são paulo, av. trabalhador são-carlense, 400 – parque arnold schimidt, são carlos, 13566-590, brazil e-mail: julia.f.almeida@usp.br reference: almeida et al. (2021). the implementation of additive manufacturing in industries starting from organizational cultural characteristics – a review. international journal of engineering materials and manufacture, 6(4) 242-258. the implementation of additive manufacturing in industries starting from organizational cultural characteristics – a review almeida, j. f., mourarias, m. n., gerolamo, m. c. and coelho, r. t. received: 26 february 2021 accepted: 20 april 2021 published: 01 october 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract additive manufacturing (am), widely known as 3d printing, is a fabrication process to build 3d parts layer by layer directly from a virtual cad model. it is an innovative technology, with the potential to revolutionize the manufacturing industry completely. it is possible to manufacture complex shaped parts, shortening production sequence, reducing time to market and allowing mass customization. as one of industry 4.0 nine pillars, am has promoted an extensive number of researches. some of them identify organizational culture as a leading factor affecting its implementation in industries. like any change within companies, organizational culture can be a decisive factor for the successful implementation of am. however, few studies have thoroughly explored the subject to find which set of cultural characteristics can guide the whole organization. this research identifies, through a systematic literature review (slr) based on the prisma protocol, which set of cultural characteristics can guide the transition from conventional to am technology. the systematic literature review was capable of identifying a set of 41 cultural characteristics, which the company should present to implement am successfully. knowing which cultural characteristics can help am implementation companies will increase their chances of succeeding when moving towards am technologies within industry 4.0. keywords: additive manufacturing, organizational culture, innovation. 1 introduction new concepts, such as industry 4.0, are emerging bringing nine pillars: big data and analytics; autonomous robots; simulation; system integration; internet of things (iot); cyber security and cyber physical systems (cps); cloud computing; augmented reality and additive manufacturing (am). to couple with that, existing production systems will have to be transformed (vaidya, ambad, & bhosle, 2018). am, for example, is significantly changing the current production systems, presenting potential to transform the entire global market. with am many companies can move from a concept of mass production to the production of customized products, in smaller batches, made to order or even diversify its existing products. many investigations on several aspects of am have been carried out. for example, bourell et al. (2017); ngo, kashani, imbalzano, nguyen, & hui (2018) and singh, ramakrishna, & singh (2017) addressed materials used in am processes, biamino et al. (2011); casati, lemke, & vedani (2016); debroy et al. (2018); gaytan et al. (2010); gu, meiners, wissenbach, & poprawe (2012); khairallah, anderson, rubenchik, & king (2017); li, zhou, brochu, provatas, & zhao (2020); and vrancken, thijs, kruth, & van humbeeck (2012), analysed various existing am technologies, microstructures of the materials produced, as well as their mechanical properties. despite the enormous expectations created around am technology and its innovative effects in several sectors, the current literature is more concentrated on engineering, with few contributions related to the impacts suffered by industries regarding its organizational aspects (savolainen & collan, 2020). in such context, the organizational culture must be a factor to consider, since several studies indicate that it is one of the main responsible for improvements in performance (cameron, quinn, degraff, & thakor, 2006) and excellence achievements (schein, 1984). most people responsible for industrial organizations normally fear changes, such as, moving towards implementing am as a manufacturing technology. the impact of that manoeuvre on personnel must be considered almeida et al. (2021): international journal of engineering materials and manufacture, 6(4), 242-258 243 (dietrich, kenworthy, & cudney, 2019). to lead the necessary changes in a company dietrich, kenworthy, & cudney (2019) developed the eight-step model presented by kotter (1996), to promote a new approach in the company culture. through their experiences, those authors highlighted that “adopting and anchoring am change within the company culture is harder than it may seem”. if the manager underestimates the culture change requirements necessary to implement am in the organization, even when hiring an am expert, the implementation process could lead to failure (dietrich et al., 2019). this research work aims at identifying a set of cultural characteristics, through a systematic literature review (slr) based on the prisma protocol, which can lead to a successful implementation of am in many companies. the methodology resulted in a large set of identified cultural characteristics, which were discussed and analysed. the paper is organized as follows: section 2 contains the background of additive manufacturing and organizational culture. section 3 presents the research methodology. in section 4, the results are presented and discussed, and section 5 presents the conclusion. 2 backgrounds 2.1 additive manufacturing additive manufacturing (am) was a technology, initially named as rapid prototyping, that today is widely known as 3d printing (gibson, rosen, & stucker, 2015). the astm f2792 10 (2010) standard defines am as “process of joining materials to make objects directly from a cad (computer aided design) data, usually layer upon layer, as opposed to subtractive manufacturing techniques (machining, for example)”. am technologies can be divided into seven categories: binder jetting; directed energy deposition (ded); material extrusion; material jetting; powder-bed fusion (pbf); sheet lamination; e vat photopolymerization (american society for testing and materials, 2012), each one of them with a particular way of building parts, but with se same concept as defined by the standard. the am manufacturing process is performed in a series of steps that vary according to the am technology and equipment used. generally, the steps are: design in a cad software; conversion to stl; transfer to am machine and stl file manipulation; machine setup; build; removal; post-processing; and application (gibson et al., 2015). to evaluate the viability of using am, several factors must be analysed to define the most suitable manufacturing process. depending on the level of complexity, a traditional process would take too long or technologically it would be unsuitable for the whole part. additional factors are the level of customization, the size of a production batch, i.e., the production volume, what the costs would be, the production rate, etc. (bland & conner, 2015). the pace of adoption am in each sector depends on the characteristics of the company, level of regulation and characteristics of the leaders in relation to innovation acceptance and risk assuming (saunders, 2018). renishaw, a company that works with the pbf process, proposed a model to show the different levels of am adoption: rapid prototypes & tooling; direct part replacement; part consolidation; and dfam (design for am) optimized. the first level is the starting point for most companies to implement am in their production system. at the second level, the process is changed to am, eliminating traditional production sequences and making the supply chain more agile (saunders, 2018). the third level is the first in which parts are really modified and am starts to gain advantages thanks to its ability to produce complex, lighter shapes and with the possibility of small customizations. there is also the possibility of replacing several parts, previously assembled, with a single one, produced in a shorter period of time. finally, the fourth level, offers full use of am technology, by which everything can be improved, modified by topological optimization making the part lighter and more efficient, as well as the whole product. additionally, am allows mass customization without increasing cost and time (saunders, 2019). to achieve the highest levels, it will be required more maturity inside the organization and a greater commitment by the entire company to the development and qualification of new products, as well as with all the difficulties of a new manufacturing process. the benefits tend to increase and the more disruptive the technology incorporated into products, the more valuable they become (saunders, 2018). each company must analyse which stage it is in, and follow the steps to improve its product using am. 2.2 organizational culture organizational culture, as defined by schein (1984), “is the pattern of basic assumptions that a given group has invented, discovered, or developed in learning to cope with its problems of external adaptation and internal integration, and that have worked well enough to be considered valid”. several recent works around the world point, through empirical evidence, to the influence of organizational culture on the overall performance of most organizations. other works, moreover, point to the influence of organizational culture on companies innovation (stacho, potkány, stachová, & marcineková, 2016). in this context, to develop innovation, some studies indicate that companies need “knowledge, new skills, flexible working conditions; organizational climate and culture that support the development of innovations and the innovation potential of each individual” (vnoučková & urbancová, 2020). cultural characteristics (cc), such as, flexibility and support for positively change, influence creativity and, consequently, innovation within a company (shahzad, xiu, & shahbaz, 2017). as a consequence, some cultural characteristics need to be developed, such as, organizational values and their alignment with those of employees, team motivation and development, selection of employees and their commitment to innovation. (carro-suárez, sarmiento-paredes, & rosano-ortega, 2017 yu & shih, 2018) highlight that organizational culture influences the sustainability of a business, and the factors that most affect the sustainability, would be the mission, the vision, the the implementation of additive manufacturing in industries starting from organizational cultural characteristics – a review 244 presence of a goal and its consistency. employees should also be involved in knowing and meeting customer needs, learning new skills and creating changes (ali taha, sirkova, & ferencova, 2016; vargas halabi, mora esquivel, & ortiz acuña, 2015). cross-functional cooperation, with teams from different departments and different sets of knowledge and skills, facilitates the processes of communication, information sharing and cooperation, influencing the company success (lee, chong, & ramayah, 2018). many of these cultural characteristics covered by the publications are derived from models such as competing values framework by quinn & rohrbaugh (1983), organizational culture assessment instrument (ocai) by cameron, k. s.; quinn (1999); ocp model (organizational culture profile) by o’reilly, chatman, & caldwell (1991); model by hofstede (2001); cooke, r. a.; lafferty (1995) in organizational culture index (oci) (1995). quinn and rohrbaugh's cvf (competing values framework) and organizational culture assessment instrument (ocai), which define clan/collaboration, hierarchical/control, adhocracy/creation and market/competition culture, are the ones that most appeared in the publications. organizational learning, which is adept at creating, acquiring and transferring knowledge and modifying organizational behaviour to reflect new knowledge and perceptions (garvin, 1993), also impacts positively the results of innovations in organizations, (chang, liao, & wu, 2017; chatterjee, pereira, & bates, 2018; leal-rodríguez, eldridge, ariza-montes, & morales-fernández, 2019; mardiana & tjakratmadja, 2019; rezaei, allameh, & ansari, 2018; tang & yeh, 2015) with knowledge transfer being the mediator between organizational culture and the capacity for innovation (liao, hu, chen, & lin, 2015). the most flexible and supportive organizations (liao et al., 2015), such as those with an adhocracy or clan culture, are those with the highest rates of knowledge/learning transfer (chatterjee et al., 2018), unlike cultures market and hierarchical (leal-rodríguez et al., 2019; rezaei et al., 2018). however, during crises, the hierarchical culture can be great at offering support due to its strong leadership structure and rules that helps maintain the organization's cohesion (mardiana & tjakratmadja, 2019). with regard to organizational agility, the adhocracy culture and clan stand out, since these cultures are more flexible and adaptive, the latter to a lesser extent. as for the hierarchical culture, which is expected to have a negative effect in changes it can have a positive effect, because the stability, control and order promoted by it can be beneficial in scenarios of crises and uncertainties (felipe, roldán, & leal-rodríguez, 2017), including the presence of control systems can positively influence the management of innovations (alharbi, jamil, mahmood, & shaharoun, 2019). leadership can also be one of the factors that influence the innovative behaviour of employees. leaders must: stimulate innovation in employees, monitor the innovation process, motivate employees to be creative, be a leader in the implementation of innovative processes, planning and starting the innovation process (szczepańska-woszczyna, 2015). regarding the development of new products, the profiles of adhocracy culture and market are the ones that stand out the most. the adhocracy in the initial and implementation phases of a product, and the market only in the implementation phase (naranjo-valencia, jimenez-jimenez, & sanz-valle, 2017a). finally, although there are a large number of studies on organizational culture, there is still no common and integrated approach among these diverse works, which makes the definition of organizational culture and how to measure culture still imprecise. new work should go against this, avoiding the fragmentation of what is already known about organizational culture (chatman & o’reilly, 2016). 2.3 am and organizational culture companies with business models whose values focus on efficiency, usually, do not favour innovation (hock, clauss, & schulz, 2016), unlike those that adopt flexibility in operations (wu, huang, huang, & du, 2019). exploratory studies (alexe & alexe (2018) point out that companies related to technology give more importance to aspects favouring innovative environments compared to those of heavy industry (machines for example). (bercea, lakatos, & bacali, 2019) find that organizational culture of non-profit companies carries greater importance to innovation than those seeking for non-profit. although managers believe that the cultural aspect is important for the success of the business and that innovation can bring competitive advantages (dorin maier, robert bumbac, cristian ilie, & andreea maier, 2019), leaders must clearly understand how the available organizational behaviour can influence the company business (krupskyi & kuzmytska, 2020). in a scenario of massive digitalization and industry 4.0 (i4.0), culture impacts the success of these initiatives (sieber, 2019; ziaei nafchi, mohelská, & maresova, 2019), as it determines the development and survival of an organization (pietruszka-ortyl, 2019). even if some change takes months or years, making a culture more innovative is extremely important for organizations (bendak, shikhli, & abdel-razek, 2020) in a scenario of emerging technologies such as additive manufacturing (3d printing), robotics, among others (chang et al., 2017). although it has great potential innovation, am present several barriers to be implemented in companies. those barriers can be classified into eight distinguished classes: organizational, educational, technological, financial, quality; project, regulations, and environmental (almeida, 2021). these barriers have been extensively studied by researchers, but cultural characteristics of companies are another subject specifically related with people living and pushing the whole organization. a company culture can encourage or repress innovations and changes. companies must work to develop a culture strongly supporting innovative behaviour in employees (stacho et al., 2016). one innovative and disruptive technology, such as am, will have a great impact on most companies, especially in their organizational culture, which will certainly go through significant changes in the near future. almeida et al. (2021): international journal of engineering materials and manufacture, 6(4), 242-258 245 3 methodologies for the identification of cultural characteristics that may affect the adoption of innovative practices, such as am, a slr was carried out supported by the prisma protocol (mcinnes et al., 2018; stewart et al., 2015). to guide this review, the research question was defined: q1 what cultural characteristics/factors affect the adoption of innovative technologies such as am? to answer this question, the scopus and web of science (wos) databases were used for search. table 1 presents the terms and a search string. publications from journals and from congresses were used, in 3 languages: english, portuguese and spanish. thus 217 publications were selected after eliminating duplicates. title, summary and keywords of these documents were read identifying only those related to the research question (q1), remaining 57. those were fully read and 35 revealed clearly related with cultural characteristics aspects that affect the adoption of innovative initiatives, such as, am. figure 1 schematically shows the phases (identification, screening, eligibility and inclusion) and the results of the slr conducted at the present work. table 1: search string data base terms and operators string scopus “organizational culture” and “innovation” title (“organizational culture”) title-abs-key(“innovation”) limit-to (subarea, “business” or “engineering” or “decision sciences” or “multidisciplinary”) limit-to (pub year, 2015 to 2020) limit-to (language, “english” or “spanish” or “portuguese”) web of science (wos) “organizational culture” and “innovation” title (“organizational culture”) topic(“innovation”) limit-to (category, management or business or engineering environmental or economics or environmental studies or multidisciplinary science or engineering manufacturing or social work or engineering industrial or environmental science or business finance or engineering multidisciplinary) limit-to (language, english or spanish or “portuguese”) figure 1: the phases of the slr through the prism protocol of the research 4 results and discussions table 2 shows a list of the cultural characteristics affecting the adoption of innovative technologies, such as am, in organization, identified after slr. in addition, presents the type of analysis performed by the authors, the sample size the implementation of additive manufacturing in industries starting from organizational cultural characteristics – a review 246 and the country where these analyses occurred. generally, all selected publications, after slr, presented the analysis of some kind of cultural characteristics, but only those explicitly refereeing to them were inserted in table 2 (22 out of the 35). the results empirically demonstrate the impact of these cultural characteristics on the organizations. figure 2 presents a map with a distribution of the papers by quantities and countries. it is possible to notice a variety of countries, with emphasis on spain, czech republic and the slovak republic with two publications each one. figure 3 shows the type of analysis used in the samples to arrive at the conclusions. there is predominance of case studies (6) and regression (5). after the extraction of the characteristics / factors, these were analysed and the similar ones were merged or eliminated. table 3 presents the synthesis of the cultural characteristics / factors in alphabetical order, its definition and the responsible (organization, leader, team or employee). in total, 41 cultural characteristics were obtained in the literature. some of the definitions were not found in the original articles, so a definition is presented by the authors. the authors first propose to develop the organization responsibility characteristics, which has more resources to develop them, and later develop the leaders, the team and the employee’s characteristics. almeida et al. (2021): international journal of engineering materials and manufacture, 6(4), 242-258 247 table 2: cultural characteristics cited by the papers nº papers cultural characteristics/factors type of analysis sample country 1 (vargas halabi et al., 2015) openness and ability to absorb new ideas; emphasis on creativity; promoting risktaking; and freedom to express opinions. case study five company managers costa rica 2 (tang & yeh, 2015) support, creative, bureaucratic, and efficiency-driven cultures structural equation modelling (sem) 398 responses from public companies taiwan 3 (hock et al., 2016) speed, quality and competence, success, innovation and flexibility, openness of internal communication, interfunctional cooperation (homburg/pflesser, 2000, as cited in hock et al., 2016) structural equation modelling (sem) 305 small and medium-sized electronics industry germany 4 (stacho et al., 2016) open communication between subordinates and supervisors case study 3 companies slovak republic 5 (ali taha et al., 2016) plsek, 1997 as cited in (ali taha et al. (2016) identifies five factors that drive the need for creativity and innovation in organizations today: (1) superior long-term financial performance is associated with innovation; (2) customers are demanding innovation; (3) competitors are getting better at copying past innovations; (4) new technologies enable innovation; and (5) what used to work no longer works. regression 184 organizations slovak republic 6 (carro-suárez et al., 2017) mission, involvement, consistency and adaptability regression 1 ceramics industry mexico 7 (shahzad et al., 2017) external orientation, organizational climate, flexibility, support to change, teamwork and employee empowerment regression 215 responses from 29 software companies pakistan 8 (naranjo-valencia, jimenez-jimenez, & sanz-valle, 2017b) characteristics of cvf cultures by quinn & rohrbaugh (1983) and organizational culture assessment instrument (ocai) by cameron, k. s.; quinn (1999): clan, market, adhocracy and hierarchical: evaluation by external entities communication and information management; conflict / cohesion; control; growth; efficiency; emphasis on training & development; stability; flexibility / adaptation; moral; planning and goal setting; productivity; readiness; quality; use of the environment / acquisition of resources structural equation modelling (sem) 253 responses from 253 spanish manufacturing companies spain the implementation of additive manufacturing in industries starting from organizational cultural characteristics – a review 248 9 (naranjo-valencia et al., 2017a) characteristics of cvf cultures by quinn & rohrbaugh (1983) and organizational culture assessment instrument (ocai) by cameron, k. s.; quinn (1999): clan, market, adhocracy and hierarchical: evaluation by external entities communication and information management; conflict / cohesion; control; growth; efficiency; emphasis on training & development; stability; flexibility / adaptation; moral; planning and goal setting; productivity; readiness; quality; use of the environment / acquisition of resources regression 200 spanish manufacturing companies spain 10 (rezaei et al., 2018) characteristics of cvf cultures by quinn & rohrbaugh (1983) and organizational culture assessment instrument (ocai) by cameron, k. s.; quinn (1999): clan, market, adhocracy and hierarchical: evaluation by external entities communication and information management; conflict / cohesion; control; growth; efficiency; emphasis on training & development; stability; flexibility / adaptation; moral; planning and goal setting; productivity; readiness; quality; use of the environment / acquisition of resources structural equation modelling (sem) 133 responses from industrial technologybased companies and start-ups iran 11 (chatterjee et al., 2018) there are 16 transfer factors that are divided into four groups: trainee characteristics, motivation, work environment and capacity. holton (1996), as cited in chatterjee et al. (2018) describes the transfer factors related to the work environment as being composed of seven constructs, namely, performance coaching, supervisor support, supervisor sanctions, peer support, resistance to change, positive personal results and negative personal results. regression 159 responses, 98% from the private sector and 2% from the government india 12 (cui, liu, & mou, 2018) innovation, results orientation, respect for people, team orientation, stability, aggressiveness and attention to detail review 1479 publications 13 (mohelska & sokolova, 2018) organizational culture index (oci) by wallach, 1983, as cited in mohelska & sokolova (2018): risk taking, collaborative, hierarchical, procedural, relationshiporiented, results-oriented, creative, encouraging, sociable, structure, pressurized, ordered, stimulating, regulated, established solid, cautious, trusting, driving and power-oriented questionnaire answered by interns czech republic 14 (yu & shih, 2018) people-centred and value-centred approach: organization values and alignment; team motivation and development; innovation selection and commitment. case study 2 companies canada 15 (bercea et al., 2019) teamwork, participation and commitment. case study 2 for-profit and one non-profit companies romania almeida et al. (2021): international journal of engineering materials and manufacture, 6(4), 242-258 249 16 (pietruszka-ortyl, 2019) great freedom of action, teamwork and efficiency in communication, openness to changes and proactive attitudes. theoretical 238 replies poland 17 (sieber, 2019) connection, non-linearity, customer centricity, innovative, rapid experimenting, risk-taking, status-quo questioning, autonomy, bureaucratic, collaboration, control, coordination, cross-boundary, cross-functionality, discipline, hierarchy, participation, self-organization, soft-skills providing, talent investment, appreciation, flexibility, generativity, internal communication, mindset orientation, openness, subculture, success awarding, supportive review 9 articles 18 (ziaei nafchi et al., 2019) organizational culture index (oci) by wallach, 1983 as cited in ziaei nafchi et al. (2019): risk taking, collaborative, hierarchical, procedural, relationshiporiented, results-oriented, creative, encouraging, sociable, structure, pressurized, ordered, stimulating, regulated, established solid, cautious, trusting, driving and power-oriented and hofstede’s dimensions (2001): collectivism, longterm orientation, low distance of power, women's value, low degree of avoidance of uncertainty, short-term orientation, high distance of power, males values, individualism, a high degree of uncertainty. theoretical czech republic 19 (bendak et al., 2020) creativity, freedom, teamwork and risk-taking, such as availability of resources, customer orientation, employee participation, cooperation, guidance for continuous learning and flexibility. theoretical 3 midsize companies in abu dhabi city, united united arab emirates 20 (krupskyi & kuzmytska, 2020) 5 strategies: visionary, classic, adaptive, modelling, renewal case study 561 employees usa 21 (miletić, stanojević, jovanović, radivojević, & conić, 2020) collectivism, long-term orientation, low distance of power, women's value, low degree of avoidance of uncertainty, short-term orientation, high distance of power, males’ values, individualism, a high degree of uncertainty (hofstede dimensions) analytic hierarchy process (ahp) textile companies serbia 22 (parolin, bonfim, segatto, & espindola, 2020) flexible organizational structure; successful organizational culture based on technology and innovation; cohesion among its members; strategic management of human resources for the valorisation of people; decision-making process aiming at a clear orientation to the market, which adds value to r&d results (lau & ngo, 2004; tidd et al., 2008, as cited in parolin, bonfim, segatto, & espindola, 2020) case study 324 respondents from 58 large companies and 41 public and private research institutes. brazil the implementation of additive manufacturing in industries starting from organizational cultural characteristics – a review 250 figure 2: paper by quantities and countries figure 3: type of analysis table 3: synthesis of cultural characteristics extracted from literature nº cultural characteristics definition responsible 1 adaptability “the extent to which organizations focus on learning from competitors and customers and are able to change” (chatman & o’reilly, 2016). organization 2 aggressiveness “determination to win or succeed, and the use of forceful action to do this” (cambridge english dictionary, 2021a). organization 3 collectivism “is characterized by a focus on shared objectives, interchangeable interests, and team almeida et al. (2021): international journal of engineering materials and manufacture, 6(4), 242-258 251 nº cultural characteristics definition responsible commonalities among in-group members” (triandis, 1995, as cited in chatman & o’reilly, 2016). 4 commitment “willingness to give your time and energy to a job, activity, or something that you believe in”(cambridge english dictionary, 2021b). “ensures everyone’s participation in creating anything new (chatterjee et al., 2018). employee 5 communication “the process of sharing information, especially when this increases understanding between people or groups” (cambridge english dictionary, 2021c). organization/ team 6 competence “shows the prominence of having competent skills, knowledge and experience of the employees in performing the task-at-hand (lee et al., 2018)”. employee 7 connection to company values “the state of being related to someone or something else”(cambridge english dictionary, 2021d), in this case, related to the company's values. organization 8 consistency “internal consistency is based on whether an organization has espoused a set of values that are consistent and to which they visibly adhere, including interdepartmental coordination” (chatman & o’reilly, 2016). organization 9 continuous learning “the process of learning new skills and knowledge on an on-going basis” (valamis, 2019). employee 10 control of activities “organizations require control systems that define goals, assess variation from these, and provide feedback to individuals so they can adjust and coordinate their activities” (chatman & o’reilly, 2016). leader 11 cooperation “the process of working with another company, organization, or country in order to achieve something”(cambridge english dictionary, 2021e). organization/team 12 creativity “a complex, cognitive process that involves finding and developing solutions to novel, ill-defined problems that will enhance the organization in the form of its products, services, processes, and procedures” (mumford and gustafson, 1988, as cited in ali taha et al., 2016). team/employee 13 customer-focused “paying great attention to the needs and opinions of customers” (cambridge english dictionary, 2021f) organization 14 discipline “the ability to control yourself or other people, even in difficult situations” (cambridge english dictionary, 2021g) leader/team/employee 15 efficiency “a situation in which a person, company, factory, etc. uses resources such as time, materials, or labour well, without wasting any”(cambridge english dictionary, 2021h). organization 16 empower employees “the ways in which organizations provide their employees with a certain degree of leader the implementation of additive manufacturing in industries starting from organizational cultural characteristics – a review 252 nº cultural characteristics definition responsible autonomy and control in their day-to-day activities” (asq, 2021). 17 encouragement “words or behaviour that give someone confidence to do something”(cambridge english dictionary, 2021i). leader 18 flexibility “the ability to change or be changed easily according to the situation” (cambridge english dictionary, 2021j). organization 19 innovation “the successful development of new ideas or method, or the use of new ideas and methods” (mclean, 2005, as cited in ali taha et al., 2016;(cambridge english dictionary, 2021k). organization 20 leadership support “encourage someone or something because you want him or her to succeed (cambridge english dictionary, 2021v) , in that case, provided by the leadership. leader 21 low power distance this dimension defines how much a society accepts the unequal distribution of power (hofstede, 2001) organization 22 motivation “willingness to do something, or something that causes such willingness” (cambridge english dictionary, 2021m). employee 23 multifunctional teams “it is a team composed of people with the different skills required to complete the job” (ramiro, 2018). team 24 openness to new ideas “the quality of being able to think about, accept or listen to different ideas or people”(oxford advanced learner’s dictionary, 2021). leader/team/employee 25 people-centered (employees) “an approach in which people should be treated as individuals and receive appropriate and timely care that meets their needs (dictionarysegen’s, 2011) ”, in this case, related to employee. organization 26 personal growth “is a process of both understanding yourself and pushing yourself to reach your highest potential” (jackson, 2021) employee 27 proactive attitudes “taking action by causing change and not only reacting to change when it happens” (cambridge english dictionary, 2021n). employee 28 quality “the degree of excellence of something, often a high degree of it”(cambridge english dictionary, 2021o). organization 29 questioning (team always question what is being developed/ restlessness) “expressing doubts about the value or truth of something; showing that you want an answer about something” (cambridge english dictionary, 2021p). team/ employee 30 rapid experimentation (split project into steps) “rapid experimentation enables teams to build the minimum amount to test the most important questions. with this agile approach to product development, experiments are launched rapidly to validate assumptions, test hypotheses and to discover new ideas (airfocus, 2020)”. team 31 readiness “willingness or a state of being prepared for something” (cambridge english dictionary, 2021q). team/ employee almeida et al. (2021): international journal of engineering materials and manufacture, 6(4), 242-258 253 nº cultural characteristics definition responsible 32 recognition of work “public appreciation for a person’s or group’s achievements”(cambridge english dictionary, 2021r). organization/leader/team 33 risk taking “the activity of taking risks in order to start a company, increase profits, etc.”(cambridge english dictionary, 2021s). organization 34 personal autonomy “is the capacity to decide for oneself and pursue a course of action in one’s life, often regardless of any particular moral content”(internet encyclopedia of philosophy, 2021). employee 35 sociability “the quality of liking to meet and spend time with other people” (cambridge english dictionary, 2021t). employee 36 structuring “to plan, organize, or arrange the parts of something”(cambridge english dictionary, 2021u). organization/leader 37 talent investment “the act of putting money, effort, time, etc. into something to make a profit or get an advantage” in this case, related “to people who have a natural ability to be good at something”(cambridge english dictionary, 2021l). organization/leader 38 team cohesion “the strength and extent of interpersonal connection existing among the members of a group” (cfi, 2021) team 39 teamwork “employee participation and corporate commitment to employees” (rezaei et al., 2018). team/employee 40 trust between members and leadership “belief that you can depend on someone or something”, in this case, related to members and leadership (cambridge english dictionary, 2021w). team 41 value in people “the importance or worth of something for someone; to consider something important”(cambridge english dictionary, 2021x), in this case, related to people. organization the figure 4 shows the quantity of characteristics that must be developed by each responsible. figure 4: number of characteristics related to each responsible the implementation of additive manufacturing in industries starting from organizational cultural characteristics – a review 254 5 conclusions to answer the research question “what cultural characteristics/factors affect the adoption of innovative technologies, such as am?” this work performed a systematic literature review (slr) to identify organizational culture characteristics that can provide a path to successfully implement innovative technologies, which will be fundamental to survive throughout industry 4.0. in total, 41 cultural characteristics were selected and summarized. most people inside organizations usually fears changes. it becomes very important that companies develop some culture characteristics to assist their personnel during changes, helping them to understand how to adapt to new market demands. the incorporation of those characteristics by the organization can encourage innovation and help the implementation of innovative technologies and not only am. in future work these characteristics will be evaluated by am experts to determine which of them are most important to be developed. by knowing which cultural characteristics can make companies more susceptible to changes, they can be better prepared to implement am in an effective way, towards industry 4.0. acknowledgement this study was financed in part by the coordenação de aperfeiçoamento de pessoal de nível superior brasil (capes) finance code 001. fapesp 2016/11309-0 references 1. airfocus. (2020). what is rapid experimentation? definition and examples. retrieved 30 march 2021, from https://airfocus.com/glossary/what-is-rapid-experimentation/ 2. alexe, c. g., & alexe, c. m. (2018). similarities and differentiations at the level of the industries in acquiring an organizational culture in innovation. in procedia manufacturing (vol. 22, pp. 317–324). elsevier b.v. retrieved from https://doi.org/10.1016/j.promfg.2018.03.048 3. alharbi, i. b., jamil, r., mahmood, n. h. n., & shaharoun, a. m. (2019). exploring the relationships between organizational culture, management control system and organizational innovation. global business review, 097215091987034. retrieved 3 january 2021 from https://doi.org/10.1177/0972150919870341 4. ali taha, v., sirkova, m., & ferencova, m. (2016). the impact of organizational culture on creativity and innovation. polish journal of management studies, 14(1), 7–17. retrieved from https://doi.org/10.17512/pjms.2016.14.1.01 5. almeida, j. f. (in press) (2021). adoção de manufatura aditiva (ma) para metais em empresas: identificação de barreiras e proposta de roteiro para implementação. universidade de são paulo. 6. american society for testing and materials. (2010). astm f2792-10: standard terminology for additive manufacturing technologies. 7. american society for testing and materials. (2012). astm f2792 12a: standard terminology for additive manufacturing technologies. 8. asq. (2021). what is employee empowerment? job involvement & culture | asq. retrieved 29 march 2021, from https://asq.org/quality-resources/employee-empowerment 9. bendak, s., shikhli, a. m., & abdel-razek, r. h. (2020). how changing organizational culture can enhance innovation? development of the innovative culture enhancement framework. cogent business and management, 7(1). retrieved from https://doi.org/10.1080/23311975.2020.1712125 10. bercea, o.-b., lakatos, e.-s., & bacali, l. (2019). comparative study regarding organizational culture: nonprofit organization and profit-oriented organization (pp. 41–52). retrieved from https://doi.org/10.1007/978-3-319-89872-8_3 11. biamino, s., penna, a., ackelid, u., sabbadini, s., tassa, o., fino, p., … badini, c. (2011). electron beam melting of ti-48al-2cr-2nb alloy: microstructure and mechanical properties investigation. intermetallics, 19(6), 776– 781. retrieved from https://doi.org/10.1016/j.intermet.2010.11.017 12. bland, s., & conner, b. (2015). mapping out the additive manufacturing landscape. metal powder report, 70(3), 115–119. retrieved from https://doi.org/10.1016/j.mprp.2014.12.052 13. bourell, d., kruth, j. p., leu, m., levy, g., rosen, d., beese, a. m., & clare, a. (2017). materials for additive manufacturing. cirp annals, 66(2), 659–681. retrieved from https://doi.org/10.1016/j.cirp.2017.05.009 14. cambridge english dictionary. (2021a). aggressiveness. retrieved 30 march 2021, from https://dictionary.cambridge.org/pt/dicionario/ingles/aggressiveness 15. cambridge english dictionary. (2021b). commitment. cambridge english dictionary. retrieved 29 march 2021 from https://dictionary.cambridge.org/pt/dicionario/ingles/commitment?q=commitment 16. cambridge english dictionary. (2021c). communication. cambridge english dictionary. retrieved 29 march 2021 from https://dictionary.cambridge.org/dictionary/english/communication 17. cambridge english dictionary. (2021d). connection. retrieved 30 march 2021, from https://dictionary.cambridge.org/pt/dicionario/ingles/connection?q=connection 18. cambridge english dictionary. (2021e). cooperation. cambridge english dictionary. retrieved 29 march 2021 from https://dictionary.cambridge.org/pt/dicionario/ingles/cooperation 19. cambridge english dictionary. (2021f). customer-focused. cambridge english dictionary. retrieved 29 almeida et al. (2021): international journal of engineering materials and manufacture, 6(4), 242-258 255 march 2021 from https://dictionary.cambridge.org/pt/dicionario/ingles/customer-focused 20. cambridge english dictionary. (2021g). discipline. cambridge english dictionary. retrieved 29 march 2021 from https://dictionary.cambridge.org/pt/dicionario/ingles/discipline?q=discipline 21. cambridge english dictionary. (2021h). efficiency. cambridge english dictionary. retrieved 29 march 2021 from https://dictionary.cambridge.org/pt/dicionario/ingles/efficiency?q=efficiency 22. cambridge english dictionary. (2021i). encouragement. cambridge english dictionary. retrieved 29 march 2021 from https://dictionary.cambridge.org/pt/dicionario/ingles/encouragement?q=encouragement 23. cambridge english dictionary. (2021j). flexibility. cambridge english dictionary. retrieved 29 march 2021 from https://dictionary.cambridge.org/pt/dicionario/ingles/flexibility?q=flexibility 24. cambridge english dictionary. (2021k). innovation. retrieved 30 march 2021, from https://dictionary.cambridge.org/pt/dicionario/ingles/innovation 25. cambridge english dictionary. (2021l). investment. retrieved 30 march 2021, from https://dictionary.cambridge.org/pt/dicionario/ingles/investment 26. cambridge english dictionary. (2021m). motivation. cambridge english dictionary. retrieved 29 march 2021 from https://dictionary.cambridge.org/pt/dicionario/ingles/motivation?q=motivation 27. cambridge english dictionary. (2021n). proactive. cambridge english dictionary. retrieved from https://dictionary.cambridge.org/pt/dicionario/ingles/proactive 28. cambridge english dictionary. (2021o). quality. cambridge english dictionary. retrieved 29 march 2021 from https://dictionary.cambridge.org/pt/dicionario/ingles/quality?q=quality 29. cambridge english dictionary. (2021p). questioning. cambridge english dictionary. retrieved 29 march 2021 from https://dictionary.cambridge.org/pt/dicionario/ingles/questioning?q=questioning 30. cambridge english dictionary. (2021q). readiness. cambridge english dictionary. retrieved 29 march 2021 from https://dictionary.cambridge.org/pt/dicionario/ingles/readiness?q=readiness 31. cambridge english dictionary. (2021r). recognition. retrieved from https://dictionary.cambridge.org/pt/dicionario/ingles/recognition 32. cambridge english dictionary. (2021s). risk-taking. cambridge english dictionary. retrieved from https://dictionary.cambridge.org/pt/dicionario/ingles/risk-taking 33. cambridge english dictionary. (2021t). sociability. cambridge english dictionary. retrieved 29 march 2021 from https://dictionary.cambridge.org/pt/dicionario/ingles/sociability?q=sociability 34. cambridge english dictionary. (2021u). struturing. cambridge english dictionary. retrieved from https://dictionary.cambridge.org/pt/dicionario/ingles/structuring 35. cambridge english dictionary. (2021v). support. retrieved 30 march 2021, from https://dictionary.cambridge.org/pt/dicionario/ingles/support 36. cambridge english dictionary. (2021w). trust. retrieved 30 march 2021, from https://dictionary.cambridge.org/pt/dicionario/ingles/trust 37. cambridge english dictionary. (2021x). value. retrieved 30 march 2021, from https://dictionary.cambridge.org/pt/dicionario/ingles/value 38. cameron, k. s.; quinn, r. e. (1999). diagnosing and changing organizational culture: based on the competing values framework. 1st edition, ma: addison wesley. 39. cameron, k., quinn, r. e., degraff, j., & thakor, a. (2006). competing values leadership: creating value in organizations. 40. carro-suárez, j., sarmiento-paredes, s., & rosano-ortega, g. (2017). organizational culture and its influence in business sustainability. the importance of culture in corporate sustainability. estudios gerenciales, 33(145), 352– 365. retrieved 4 january 2021 from https://doi.org/10.1016/j.estger.2017.11.006 41. casati, r., lemke, j., & vedani, m. (2016). microstructure and fracture behavior of 316l austenitic stainless steel produced by selective laser melting. journal of materials science and technology, 32(8), 738–744. retrieved from https://doi.org/10.1016/j.jmst.2016.06.016 42. cfi. (2021). team cohesion overview, examples, strategies for team bonding. retrieved 29 march 2021, from https://corporatefinanceinstitute.com/resources/careers/soft-skills/team-cohesion/ 43. chang, w. j., liao, s. h., & wu, t. te. (2017). relationships among organizational culture, knowledge sharing, and innovation capability: a case of the automobile industry in taiwan. knowledge management research and practice, 15(3), 471–490. retrieved from https://doi.org/10.1057/s41275-016-0042-6 44. chatman, j. a., & o’reilly, c. a. (2016). paradigm lost: reinvigorating the study of organizational culture. research in organizational behavior, 36, 199–224. retrieved from https://doi.org/10.1016/j.riob.2016.11.004 45. chatterjee, a., pereira, a., & bates, r. (2018). impact of individual perception of organizational culture on the learning transfer environment. international journal of training and development, 22(1), 15–33. retrieved from https://doi.org/10.1111/ijtd.12116 46. cooke, r. a.; lafferty, j. c. (1995). organizational culture inventory. plymouth, mi: human synergistic international,. 47. cui, y., liu, y., & mou, j. (2018). bibliometric analysis of organisational culture using citespace. south african journal of economic and management sciences, 21(1). retrieved from https://doi.org/10.4102/sajems.v21i1.2030 the implementation of additive manufacturing in industries starting from organizational cultural characteristics – a review 256 48. debroy, t., wei, h. l., zuback, j. s., mukherjee, t., elmer, j. w., milewski, j. o., … zhang, w. (2018). additive manufacturing of metallic components – process, structure and properties. progress in materials science. retrieved from https://doi.org/10.1016/j.pmatsci.2017.10.001 49. dictionarysegen’s. (2011). people-centered. retrieved 30 march 2021, from https://medicaldictionary.thefreedictionary.com/people-centered+care 50. dietrich, d. m., kenworthy, m., & cudney, e. a. (2019). additive manufacturing change management. additive manufacturing change management. boca raton : taylor & francis, 2019. | series: continuous: crc press. retrieved from https://doi.org/10.1201/9780429465246 51. maier, d., bumbac, r., ilie, c., & maier, a. (2019). organizational culture – prerequisite of an innovative behavior in business. in international business information management association (ibima) . retrieved 3 january 2021 from https://ibima.org/accepted-paper/organizational-culture-prerequisite-of-an-innovativebehavior-in-business/ 52. felipe, c. m., roldán, j. l., & leal-rodríguez, a. l. (2017). impact of organizational culture values on organizational agility. sustainability (switzerland), 9(12). retrieved from https://doi.org/10.3390/su9122354 53. garvin, d. a. (1993). building a learning organization. harvard business review, july–augus. 54. gaytan, s. m., murr, l. e., martinez, e., martinez, j. l., machado, b. i., ramirez, d. a., … wicker, r. b. (2010). comparison of microstructures and mechanical properties for solid and mesh cobalt-base alloy prototypes fabricated by electron beam melting. metallurgical and materials transactions a: physical metallurgy and materials science, 41(12), 3216–3227. retrieved from https://doi.org/10.1007/s11661-010-0388-y 55. gibson, i., rosen, d., & stucker, b. (2015). additive manufacturing technologies: 3d printing, rapid prototyping, and direct digital manufacturing, second edition. additive manufacturing technologies: 3d printing, rapid prototyping, and direct digital manufacturing, second edition. springer new york. retrieved from https://doi.org/10.1007/978-1-4939-2113-3 56. gu, d. d., meiners, w., wissenbach, k., & poprawe, r. (2012). laser additive manufacturing of metallic components: materials, processes and mechanisms. international materials reviews, 57(3), 133–164. retrieved from https://doi.org/10.1179/1743280411y.0000000014 57. hock, m., clauss, t., & schulz, e. (2016). the impact of organizational culture on a firm’s capability to innovate the business model. r and d management, 46(3), 433–450. retrieved from https://doi.org/10.1111/radm.12153 58. hofstede, g. (2001). culture’s consequences: comparing values, behaviors, institutions, and organizations across nations. culture’s consequences: comparing values, behaviors, institutions, and organizations across nations. retrieved 29 march 2021 from https://digitalcommons.usu.edu/unf_research/53 59. internet encyclopedia of philosophy. (2021). autonomy. internet encyclopedia of philosophy. 60. jackson, r. (2021). the importance of self-improvement and personal growth | top practices. retrieved 29 march 2021, from https://www.toppractices.com/blog/the-importance-of-self-improvement-and-personalgrowth.cfm 61. khairallah, s. a., anderson, a. t., rubenchik, a. m., & king, w. e. (2017). laser powder-bed fusion additive manufacturing: physics of complex melt flow and formation mechanisms of pores, spatter, and denudation zones. in additive manufacturing handbook: product development for the defense industry (pp. 613–628). retrieved from https://doi.org/10.1201/9781315119106 62. kotter, j. p. (1996). leading change. harvard business review press. 63. krupskyi, o. p., & kuzmytska, y. (2020). organizational culture and business strategy: connection and role for a company survival. central european business review, 9(4), 1–26. retrieved from https://doi.org/10.18267/j.cebr.241 64. leal-rodríguez, a. l., eldridge, s., ariza-montes, j. a., & morales-fernández, e. j. (2019). understanding how organizational culture typology relates to organizational unlearning and innovation capabilities. journal of the knowledge economy, 10(4), 1497–1514. retrieved from https://doi.org/10.1007/s13132-015-0344-6 65. lee, w. l., chong, a. l., & ramayah, t. (2018). organizational culture and performance of malaysian manufacturing firms. international journal of advanced and applied sciences, 5(12), 59–66. retrieved from https://doi.org/10.21833/ijaas.2018.12.008 66. li, j., zhou, x., brochu, m., provatas, n., & zhao, y. f. (2020). solidification microstructure simulation of ti6al-4v in metal additive manufacturing: a review. additive manufacturing. retrieved from https://doi.org/10.1016/j.addma.2019.100989 67. liao, s. h., hu, d. c., chen, c. c., & lin, y. l. (2015). comparison of competing models and multi-group analysis of organizational culture, knowledge transfer, and innovation capability: an empirical study of the taiwan semiconductor industry. knowledge management research and practice, 13(3), 248–260. retrieved from https://doi.org/10.1057/kmrp.2013.46 68. mardiana, s., & tjakratmadja, j. h. (2019). exploring the linkage between knowledge management and organizational culture: a study of literature. journal of advanced research in dynamical and control systems, 11(3 special issue), 1003–1012. 69. mcinnes, m. d. f., moher, d., thombs, b. d., mcgrath, t. a., bossuyt, p. m., clifford, t., … willis, b. h. (2018). preferred reporting items for a systematic review and meta-analysis of diagnostic test accuracy studies the prisma-dta statement. jama journal of the american medical association, 319(4), 388–396. retrieved almeida et al. (2021): international journal of engineering materials and manufacture, 6(4), 242-258 257 29 march 2021 from https://doi.org/10.1001/jama.2017.19163 70. miletić, s., stanojević, š. z., jovanović, i., radivojević, m., & conić, v. (2020). ahp analysis of organizational culture in textile companies in serbia. industria textila, 71(2), 124–131. retrieved from https://doi.org/10.35530/it.071.02.1588 71. mohelska, h., & sokolova, m. (2018). management approaches for industry 4.0 – the organizational culture perspective. technological and economic development of economy, 24(6), 2225–2240. retrieved from https://doi.org/10.3846/tede.2018.6397 72. naranjo-valencia, j. c., jimenez-jimenez, d., & sanz-valle, r. (2017a). impact of organisational culture on new product success: an empirical study of spanish firms. european management review, 14(4), 377–390. retrieved from https://doi.org/10.1111/emre.12116 73. naranjo-valencia, j. c., jimenez-jimenez, d., & sanz-valle, r. (2017b). organizational culture and radical innovation: does innovative behavior mediate this relationship? creativity and innovation management, 26(4), 407–417. retrieved 3 january 2021 from https://doi.org/10.1111/caim.12236 74. ngo, t. d., kashani, a., imbalzano, g., nguyen, k. t. q., & hui, d. (2018). additive manufacturing (3d printing): a review of materials, methods, applications and challenges. composites part b: engineering. retrieved from https://doi.org/10.1016/j.compositesb.2018.02.012 75. o’reilly, c. a., chatman, j., & caldwell, d. f. (1991). people and organizational culture: a profile comparison approach to assessing person-organization fit. academy of management journal, 34(3), 487–516. retrieved from https://doi.org/10.5465/256404 76. oxford advanced learner’s dictionary. (2021). openness noun definition, pictures, pronunciation and usage notes. retrieved 30 march 2021, from https://www.oxfordlearnersdictionaries.com/definition/english/openness 77. parolin, s. r., bonfim, l. r. c., segatto, a. p., & espindola, t. (2020). organizational culture for cooperation in technological innovation between research institutes and firms. journal of technology management and innovation, 15(2), 23–40. retrieved from https://doi.org/10.4067/s0718-27242020000200024 78. pietruszka-ortyl, a. (2019). the impact of organizational culture for company’s innovation strategy. marketing and management of innovations, (3), 178–192. retrieved from https://doi.org/10.21272/mmi.2019.3-14 79. quinn, r. e., & rohrbaugh, j. (1983). spatial model of effectiveness criteria: towards a competing values approach to organizational analysis. management science, 29(3), 363–377. retrieved 29 march 2021 from https://doi.org/10.1287/mnsc.29.3.363 80. ramiro, m. (2018). why should your teams be multifunctional? paradigma. retrieved 29 march 2021, from https://en.paradigmadigital.com/techbiz/why-should-your-teams-be-multifunctional/ 81. rezaei, a., allameh, s. m., & ansari, r. (2018). effect of organisational culture and organisational learning on organisational innovation: an empirical investigation. international journal of productivity and quality management, 23(3), 307. retrieved 3 january 2021 from https://doi.org/10.1504/ijpqm.2018.089803 82. saunders, m. (2018). additive impact part #1 how additive manufacturing could disrupt your market. 83. saunders, m. (2019). additive impact part #2 how am could disrupt your market. 84. savolainen, j., & collan, m. (2020). how additive manufacturing technology changes business models? – review of literature. additive manufacturing, 32, 101070. retrieved from https://doi.org/10.1016/j.addma.2020.101070 85. schein, e. (1984). coming to a new awareness of organizational culture. sloan management review, winter, 3–16. 86. shahzad, f., xiu, g. y., & shahbaz, m. (2017). organizational culture and innovation performance in pakistan’s software industry. technology in society, 51, 66–73. retrieved from https://doi.org/10.1016/j.techsoc.2017.08.002 87. sieber, m. r. (2019). the role of organizational culture for information technology management in digitalization. in conference innovation management, entrepreneurship and sustainability (imes 2019) (pp. 805–819). vysoká škola ekonomická v praze. retrieved 22 january 2021 from https://www.ceeol.com/search/chapter-detail?id=785541 88. singh, s., ramakrishna, s., & singh, r. (2017). material issues in additive manufacturing: a review. journal of manufacturing processes, 25, 185–200. retrieved from https://doi.org/10.1016/j.jmapro.2016.11.006 89. stacho, z., potkány, m., stachová, k., & marcineková, k. (2016). the organizational culture as a support of innovation processes’ management: a case study. international journal for quality research, 10(4), 769–784. retrieved from https://doi.org/10.18421/ijqr10.04-08 90. stewart, l. a., clarke, m., rovers, m., riley, r. d., simmonds, m., stewart, g., & tierney, j. f. (2015, april 28). preferred reporting items for a systematic review and meta-analysis of individual participant data: the prisma-ipd statement. jama journal of the american medical association. american medical association. retrieved 29 march 2021 from https://doi.org/10.1001/jama.2015.3656 91. szczepańska-woszczyna, k. (2015). leadership and organizational culture as the normative influence of top management on employee’s behaviour in the innovation process. in procedia economics and finance (vol. 34, pp. 396–402). elsevier bv. retrieved from https://doi.org/10.1016/s2212-5671(15)01646-9 the implementation of additive manufacturing in industries starting from organizational cultural characteristics – a review 258 92. tang, l. l., & yeh, y. l. (2015). effect of organizational culture, leadership style, and organizational learning on organizational innovation in the public sector. journal of quality, 22(5), 461–481. retrieved from https://doi.org/10.6220/joq.2015.22(5).06 93. vaidya, s., ambad, p., & bhosle, s. (2018). industry 4.0 – a glimpse. procedia manufacturing, 20, 233–238. retrieved from https://doi.org/10.1016/j.promfg.2018.02.034 94. valamis. (2019). what is continuous learning? its importance & benefits. retrieved 29 march 2021, from https://www.valamis.com/hub/continuous-learning 95. vargas halabi, t., mora esquivel, r., & ortiz acuña, c. (2015). cultura organizativa e innovación: un análisis temático en empresas de costa rica (organizational culture and innovation: a thematic analysis in costa rica’s firms). tec empresarial, 9(2), 7. retrieved from https://doi.org/10.18845/te.v9i2.2358 96. vnoučková, l., & urbancová, h. (2020). setting organisational culture to develop potential and innovativeness. quality innovation prosperity, 24(1), 54–68. retrieved from https://doi.org/10.12776/qip.v24i1.1346 97. vrancken, b., thijs, l., kruth, j. p., & van humbeeck, j. (2012). heat treatment of ti6al4v produced by selective laser melting: microstructure and mechanical properties. journal of alloys and compounds, 541, 177– 185. retrieved from https://doi.org/10.1016/j.jallcom.2012.07.022 98. wu, l. f., huang, i. c., huang, w. c., & du, p. l. (2019). aligning organizational culture and operations strategy to improve innovation outcomes: an integrated perspective in organizational management. journal of organizational change management, 32(2), 224–250. retrieved from https://doi.org/10.1108/jocm-03-20180073 99. yu, o., & shih, r. (2018). developing an innovative organizational culture: a people-centered and valuefocused approach with case studies. in picmet 2018 portland international conference on management of engineering and technology: managing technological entrepreneurship: the engine for economic growth, proceedings. institute of electrical and electronics engineers inc. retrieved from https://doi.org/10.23919/picmet.2018.8481945 100. ziaei nafchi, m., mohelská, h., & maresova, p. (2019). industry 4.0: the organizational culture perspective. in hradec economic days 2019 (pp. 575–580). university of hradec kralove. retrieved from https://doi.org/10.36689/uhk/hed/2019-02-058 international journal of engineering materials and manufacture (2019) 4(1) 1-14 https://doi.org/10.26776/ijemm.04.01.2019.01 a n m mominul islam mukut and mohammad zoynal abedin department of mechanical engineering dhaka university of engineering & technology gazipur 1707, bangladesh e-mail: abedin.mzoynal@duet.ac.bd reference: mukut, a. n. m. m. i. and abedin, m. z. (2019). review on aerodynamic drag reduction of vehicles. international journal of engineering materials and manufacture, 4 (1), 1-14 review on aerodynamic drag reduction of vehicles a n m mominul islam mukut and mohammad zoynal abedin received: 06 december 2018 accepted: 22 december 2018 published: 01 march 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract due to higher price, limited supply and negative impacts on environment by fossil fuel, automobile industries have directed their concentrations in reducing the fuel consumption of vehicles in order to achieve the lower aerodynamic drag. as a consequence, numerous researches have been carried out throughout the world for not only getting the optimum aerodynamic design with lower drag penalty and but also other parameters that increase the fuel consumption. in this regard, relevant experimental and numerical outcomes on vehicle drag reduction considering various techniques such as active, passive and combined techniques in order to delay or suppress flow separation behind the vehicles have been considered in this review paper. furthermore, the effects of drag reduction and their applicability on the vehicles are also illustrated in this paper. therefore, it is conjectured that the drag reduction has been improved as much as 20%, 21.2%, and 30% by using the active, passive and combined control systems, respectively. keywords: aerodynamic drag reduction, flow control, flow separation, environmental impact, cfd 1 introduction earlier time when fuel supply was not the main concern, cars were manufactured for high speed and stylish look ignoring the aerodynamic stability and fuel consumption. however, due to the crisis in fuel price and environmental impacts from exhaust emission, the researchers have focused their concentration to design the cars aerodynamically in order to reduce the fuel consumption as well as lowering the pollution. the drag which affects the fuel consumption can be minimized by designing the car with proper aerodynamic characteristics and also with implementation of lightweight materials for the body frame, which would decrease not only the fuel consumption but also the vehicle weight. however, most of fuel is consumed due to aerodynamic drag and the drag can be classified as skin friction drag and pressure drag. it is observed through an assessment that the pressure drag or form drag or parasite drag has the 80% contribution in the total aerodynamic drag due to the geometry of vehicles that leads to form the boundary layer separation and formation of wake region behind the vehicles [1]. moreover, the car aerodynamic performances have been enhanced through the experimental and numerical approaches with extensive investigations [2-9]. among these researches, it is seen that the methods of reducing drag and shape optimization are considered to be an inexpensive way to improve the fuel efficiency [9]. to improve the fuel consumption it is necessary to control flow separation at the rear of vehicles by applying flow control mechanisms that help either to delay or preventing the separation effect. the mechanism can be classified as active or passive flow control. the active flow control system includes movable body, holes or slots which are placed on the vehicle surface and their numbers also depend upon the flow control requirements. it is found that the active flow control system uses the actuator which consumes power from the vehicle [10]. various systems like mechanical, electromagnetic, electric, piezoelectric or acoustic are used as the mechanism for the functioning of the system and it is observed that lower weight and smaller dimension are expected to reduce their negative impacts on vehicle performance [11]. on the other hand, conventional passive control systems consist of shape modification of vehicle or attachment of add-on devices to reduce the drag and it is seen that these arrangements of passive control systems show the significant advantages over the active control systems wherein the former systems are cheaper and consume no energy from the vehicles compared to the later systems [12]. review on aerodynamic drag reduction of vehicles 2 as the aerodynamic drag reduction and fuel consumption improvement are the main concern for the vehicles and the control mechanisms are necessary for the improved performance, various researches have been updated in these fields. hence, it is necessary to list up all the updates and outcomes from the existing techniques and above all from the updated techniques which are eagerly awaited. therefore, in the present review paper, it is analysed all the updates and outcomes from the existing techniques and above all from the updated techniques for the reduction of aerodynamic drag as well as for lowing the fuel consumption of the vehicles. the next section illustrates the aerodynamic drag impacts based on fuel consumption and their overall effects on environmental pollution. 2 impacts on fuel consumption and environmental pollution due to awareness regarding the environmental pollution, tremendous endeavours have been carried out in various sectors of automobile industries. consequently, automobile industries are seen to manufacture the aerodynamically sound-vehicles that emit low emission as well as provide better fuel economy. it is revealed that aerodynamic drag varies with the square of the vehicle velocity, in which 70% of this drag are found to be accumulated from overall vehicle resistance at high speed [13]. it is also seen that reduction of vehicle aerodynamic drag is essential to lower greenhouse gas emission. the amount of drag due to the vehicle shape i.e. pressure drag is the main contributor to total drag and it is noted that about 50% of vehicle’s fuel consumption is due to aerodynamic drag at highway speeds [14]. bellman et al. [15] extensively illustrated the analysis of reducing energy consumption of ground vehicles by active flow control. in these researches, it was also revealed that aerodynamic fuel efficient vehicles had good impact on fuel reserve as it could save 245 million gallons of fuel per year by improving 1% in fuel economy. in addition, more than 30% of co2 and other greenhouse gas (ghg) emissions were seen to be occurred by these ground vehicles due to their fuel consumption. moreover, most of the usable energy from the engine were responsible to overcoming the aerodynamic drag (53%) and rolling resistance (32%); only 9% were required for auxiliary equipment and 6% were used by the drive-train. it was also found that 15% reduction in aerodynamic drag at highway speed of 55 mph could result in about 5-7% in fuel saving. due to these numerous findings, researches on vehicles aerodynamic drag reduction have seen to be prime issue in the scientific community by using different flow control techniques. 3 impact of active flow control the active flow control is a mechanism that modifies the flow field in the wake region in order to reduce the aerodynamic drag by increasing static pressure. the pressure losses in the wake region has a great contribution to increase the aerodynamic drag, and hence, the penalty is maximum for square back vehicles. this could be minimized by proper designing of rear shape of the vehicles but there are limited options in this regard for automobile industries due to the customer demand in the case of outlook appearance, ergonomically design and stability of the vehicle. moreover, this could be achieved by introducing active flow control techniques which can alter the flow structure behind the vehicles without physical modification of vehicles. several active flow control techniques used for reducing vehicle aerodynamic drag have been investigated both numerically and experimentally [16-39]. the main advantage of this type of active control technique is attributed to be a method of quick response in a way that there is no externally added devices on the vehicles’ body which causes no penalty of parasite drag. in this method, the flow can be controlled actively by movable parts, synthetic jet, steady blowing, suction, plasma actuator of having some unique features. 3.1 movable underbody diffuser the movable underbody diffuser technology is used for reducing aerodynamic drag in the vehicle by controlling rear flow field. for instance, it is extensively revealed that the rear flow field of vehicle is influenced by the flow coming out under the vehicles which implies that the rear flow field can be modified by controlling the flow under the vehicles [16, 17]. kang et al. [18] developed a movable under body diffuser as shown in figure 1 and figure 2, and numerically investigated that the automobile’s aerodynamic drag could be reduced by an average of more than 4%, which would help to enhance the constant speed fuel efficiency by approximately 2% at a range of driving speeds exceeding 70 km/h. figure 1: basic concept of actively translating rear diffuser [18]. mukut and abedin (2019): international journal of engineering materials and manufacture, 4(1), 1-14 3 3.2 steady blowing vehicles’ aerodynamic characteristics have been greatly influenced by the shape of rear end, which also affects the stability and comfort. the effect of steady blowing has been investigated experimentally on a realistic car model by heinemann et al. [19], at three different position namely, (i) perpendicular top position air jet (ii) perpendicular bottom position air jet (iii) tangential bottom position air jet which are shown in figure 3. their results showed that rear axle lift was reduced by about 5% with coefficient of drag (cd) changes around 1%. another investigation has been carried out to evaluate the effectiveness of steady blowing on the wake structure of a simplified ¼ scale square back vehicles at a variety of angles on the roof trailing edge [20]. its effects were evaluated by implementing various flow and pressure measurement techniques and results showed that overall gains were achieved. but due to the requirement for large mass flow rate, this technique has limited applicability to road vehicles. the influence of steady blowing has also been investigated by both experimentally and numerically on an ahmed body at 25° slant angle and depending on reynolds’s number, and the drag reduction has been achieved from 6 to 10.4% [20, 21], 6.4% [22], 5.7% and 2.2% (at 90° slant angle) [23], respectively. the effect of blowing angle has been investigated numerically and it is found that 11.1% drag reduction has been obtained at a blowing angle 45° [24]. an array of blowing steady 53 micro jets as shown in figure 4 were also found to be effective on a model of a generic vehicle shape, the ahmed body with a 25° slant in reducing drag coefficient (9-14%) and lift coefficient (up to 42%) depending on reynolds number [25]. these arrays of steady micro jets were positioned at 6 mm downstream of the separation line between the roof and the slanted rear window. the use of small scale, steady jets (micro jets) in normal and tangential injection orientations has been investigated through experimental parametric studies and compared with numerical simulations on honda simplified body (hbs) and it is found that drag experienced by hsb is reduced by nearly 2.6% with net reduction in power consumption [26]. figure 2: effectiveness of actively sliding diffuser at three different angles [18]. figure 3: positions of blowing jets [19]. review on aerodynamic drag reduction of vehicles 4 3.3 synthetic jets synthetic jet actuator is generally formed by orifice, cavity and piezoelectric actuator or diaphragm where flow moves back and forth through a small opening by the movement of diaphragm. an experimental parametric study has been carried out by using an array of 12 synthetic jets on an ahmed model at two different slant angles and it is revealed that the aerodynamic drag is seen to be reduced to 4.29% for 25° slanted body, but increased for 35° model [27]. several experimental works have been carried out with synthetic actuator jets on an ahmed body as shown in figure 5 and it is found that maximum drag reduction depends on reynolds’s number which is equal to 8.5% for re = 1.2 × 10 6 and 6.5% for re = 1.9 × 10 6 [28] and 10% for re = 2.3×10 6 [29]. 3.4 pulsed jet effectiveness of pulsed jet has been investigated experimentally on the suppression of the rear slant recirculation bubble, without acting on longitudinal structures on an ahmed body with 25° slant angle and it is found that 6 8% maximum drag reduction is obtained depending on the geometric and jet exhaust configurations that show different sensitivity to the forcing parameters [30]. another investigation has been carried out with an ahmed body having 35° slant angle where 20% drag reduction is achieved that confirms the interest in using pulsed jets (shown in figure 6) in order to reduce aerodynamic drag and pollutant emission [31]. by acting on the kinematic of the wake, this control technique changes the wall pressure and shear stress distributions on geometry of vehicles and generates evolutions in energy dissipation per unit process [32]. figure 4: steady micro jet actuator array mounted on the rear, slanted window of the ahmed body [25]. figure 5: components of a synthetic jet actuator [28]. a b figure 6: (a) locations of actuator on the ahmed body and (b) longitudinal section with a view of the implementation of the pulsed jets [31]. mukut and abedin (2019): international journal of engineering materials and manufacture, 4(1), 1-14 5 3.5 steady suction automobile industries seek better solution to reduce pollution and fuel consumption, in this regard, active flow control techniques have got huge attention as it requires no shape modification of the vehicles. steady suction is an active flow technique which modify vortices that affects rear wake of the vehicle. the workability of steady suction has been evaluated by both experimental and numerical approaches on simplified fastback car geometry as shown in figure 7 and this technique is capable to suppress rear window separation and reduce drag more than 17% [33]. the contribution of this method towards separated region has been analysed by flow topology on an iso-surface of total pressure loss, which is shown in figure 8. it is found that suction is effective to eliminate the separated layer developed and reattachment of flow is obtained. the effect of suction around the lateral edges of a simplified car windshield has been tested experimentally in a water tunnel [34], which provides a drag reduction of 6%. a large eddy simulation (les) has been carried out on a 25° slant angle on an ahmed body, in a view to that the combined effect is advantageous over single alone as net zero mas flux [35]. in their studies, twelve slits were arranged in six pairs in which each pair provides blowing and suction as shown in figure 9 and a drag reduction of 9.5% has been found. the combined control of suction and blowing is seen to be effective on changing the rear window wake structure, in which streamlines of time average flow is separated (without control) and re-attached (with combined control) as shown in figure 10. another experimental and numerical studies have been conducted to evaluate the suction and blowing control on drag reduction on an ahmed body in three different ways namely, (i) only suction, (ii) only blowing and (iii) combination of both control [36]. the outcomes show that their combined effect enhances the drag reduction which is shown in figure 11 and an average of 10% drag reduction is recorded. a b figure 7: (a) schematic of the used geometry and (b) implementation of the control system [33]. a b figure 8: effects of suction on rear window (a) without control and (b) with control [33]. figure 9: arrangement of slits (a) along the upper rear edge, (b) slit positions and size, and (c) direction of blowing/suction [35]. a b c review on aerodynamic drag reduction of vehicles 6 3.6 plasma actuator plasma actuator (pa) is another effective means of active flow control due to its some advantages such as easier to construct, quick to response, requires no pump and holes. the performance of pa has been investigated experimentally on an ahmed body with 25° slant angle where 10 pas are used, among of them, 6 pas are placed on the separation region on the rear wind and four are placed in two-two pairs in the region where two longitudinal vortices are observed from both sides of the rear window [37]. these position of pas are actually based on the visualization of the topological structures of the skin friction field using oil film which is shown in figure 12. the research shows that pas have effective outcomes on suppressing the separation at the rear end of vehicles and 8% drag reduction is obtained. a b figure 10: streamlines of the time-averaged flow in the symmetry plane, (a) y = 0, for the reference flow and (b) the controlled flow; location of saddle point is marked [35] figure 11: effects of actuator on drag reduction [36]. a b figure 12: (a) separation zone and (b) location of ten dbd actuators relatively to skin friction field on the rear window [37]. mukut and abedin (2019): international journal of engineering materials and manufacture, 4(1), 1-14 7 another experimental investigation with single pa shows that it can reduce drag force in steady and unsteady actuations by 3.65% and 2.44%, respectively [38]. a series of experiments have been carried out on an ahmed body having 0° and 35° slant angles and each of these are further modified by rounding the edges with different radii at different air velocity [39]. in this study, it is found that 20% drag is reduced for a velocity below 15 m/s, and 3% reduction is obtained at the highest tested velocity of 20 m/s. it is concluded that in order to increase the drag reduction at a higher velocity it is required to maintain higher voltage in pa which is not possible as the models used are so small to be withstand with higher voltage. 4 impact of passive flow control the passive flow control system needs extra add-on device/devices which are attached permanently on the vehicle surface where flow control is necessary. although the active flow control technique is easier to construct and employ on the vehicle body, but it consumes energy from the vehicles, in that regard, passive flow control technique would be better alternative if this technique is properly applied on the vehicles. the following sections describes the different passive flow control techniques. 4.1 vortex generator vortex generators (vg) is an aerodynamic body permanently fixed on vehicle with a certain angle with flow direction. generally, vgs are placed in a group to create clock-wise or counter-clockwise vortices (as per their configuration) which add momentum to near wall surface where flow is separated, as a result, the separation is suppressed or shifted further downstream. an extensive experimental studies have been carried out to evaluate the performance of vgs on aerodynamic drag reduction [40]. in this research, three combinations of vgs namely, (i) complete line-22 vgs (ii) 4 vgs on each side (iii) 14 vgs in the centre were used on a modified ahmed body which is shown in figure 13. details of flow structure are captured by piv and hot-wire anemometry. parametric studies of vg has also been conducted to figure out the optimum outcome by considering the effect of angle of vg with flow direction, their placement, effect on re. among of the tested done with three configurations of vgs, complete line of vortex generators is the most effective as it reduces the drag and lift as 12% and 60%, respectively. the performance of a special type of vg known as pocket type vg has been investigated numerically on a minivan [41]. the aim of using this type of vg is to avoid additional drag that is arisen from then conventional vgs, as these are attached externally to the vehicle body. a pair of pocket type vgs are placed in the left and right side of the rear roof end of the low mass vehicle (lmv) to evaluate the effectiveness which is shown in figure 14. the outcome shows that it can reduce the drag of 2.2%. an experimental investigation has been carried out on an ahmed body with 25° slant angle at a free stream velocity of 20 m/s using cylindrical shape vgs [42]. among the tested various configuration of vgs, maximum drag reduction of 10% is found. a slight larger drag reduction (11.7%) is found in a numerical investigation of cylindrical shape vgs [43]. the effectiveness of vgs are also evaluated numerically on suv and ahmed body with a drag reduction of 4.2% and 10%, respectively [44]. on the other hand, an experimental and numerical investigation has been carried out on a sedan car using 3 delta type of vgs at different yaw angles [45], where the middle vg was kept stationary and remaining two were changed with their angle using smaller stepper motor as shown in figure 15. in the research, a maximum reduction of drag and lift coefficient have been found as 4.53% and 2.55%, respectively. in support of drag reduction by vgs, different turbulence model named as les, des and rans have been used in an open source computational fluid dynamics (cfd) of the ahmed body with a 25° slant angle [46]. the results are well validated with the experimental works done for 3d bluff body using coherent stream wise streaks [42]. 4.2 spoiler a spoiler is an external structure attached to the rear end of the vehicles to control the flow at downstream that helps to minimize the turbulence behind the vehicle and also append downward pressure which reduces the lift. the influence of spoiler on vehicle aerodynamics has numerically investigated on a toyota eco car model as shown in figure 16, and it is found that by using this spoiler at a speed of 30 m/s, drag and lift, respectively can be reduced by 5% and more than 100% [47]. figure 13: sketch of three configurations of vgs [40]. review on aerodynamic drag reduction of vehicles 8 figure 14: surface geometry of the low mass vehicle (lmv) with a pair of pockets [41]. figure 15: four different configurations of three vgs [45]. a b figure 16: location of spoiler attached to the back of a modified lmv (a) 3d view and (b) cross-sectional view [47]. 4.3 flaps flaps are another extended surfaces which are attached with vehicle body to reduce the drag and altering the flow at the rear of vehicles to enhance aerodynamic performances. the performance of flaps has been investigated with three different free stream velocities of 20 m/s, 30 m/s and 40 m/s, by placing two flaps on the side edges of the rear slant and two flaps on the top of the rear slant, and hence the reduction of drag has been found as much as 17.6% and 15%, respectively for the two arrangements of flaps [48]. a special type of flap called automatic moving deflector (amd) taking inspiration from birds had been tested experimentally on an ahmed body as shown in figure 17, by which the maximum drag reduction is achieved from the pressure recovery by amd which is 19% [49]. another numerical investigation has been carried out with configuration of flap structures at the four edges of slant surfaces for the angles of 80°, 40° and 20° in which the values of drag reduction are found as 21.1%, 21.2% and 17.9%, respectively [50]. mukut and abedin (2019): international journal of engineering materials and manufacture, 4(1), 1-14 9 4.4 body modification body modification is the passive technique to enhance aerodynamic drag reduction which helps to reduce fuel consumption. body modification includes vehicle body outline, front and rear part; underbody geometry of the vehicle, sometimes extra added surfaces or diffusers which alter the bottom geometry of vehicles. these diffusers actually increase the air velocity below the vehicles which reduce the air pressure. as a result vehicles stability is improved as the downward forces are increased. the bottom of a sedan and wagon had been modified which has an angle at the bottom rear that acts like an underbody diffuser [51]. the performance of underbody diffuser has been tested with varying angles shown in figure 18. results from this study showed a potential aerodynamic drag reduction of the sedan car approximately 10%, and the wagon car by 2-3 %. the effect of underbody diffuser with flaps and vanes has been numerically investigated on a formula sae car [52]. the addition of vanes with diffuser enhanced the pumping capacity of diffuser as well as increase up to 13% down force. the addition of a flap above the trailing edge of the diffuser also increased down force by 25%. a numerical investigation has been carried out with different underbody drag reduction devices like undercover, underfin, and side air dam on the actual shape of a sedan-type vehicle [53], among these underbody has the ability to reduce the aerodynamic drag by 8.4 %. shape optimization has been carried out on a sedan car by artificial neural network (ann), which focus on rear shape modification [54]. to achieve the aerodynamic goal by shape optimization, six local parts from the end of sedan have been chosen as design variables and an ann approximation model was established with 64 experimental points generated by the d-optimal methodology. due to these shape optimization, 5.639% lower coefficient of drag has been obtained. six parameters namely, (i) hood (ii) windshield (iii) rear window (iv) side window (v) rear-end shrinkage and (vi) trunk lid have been modified to optimize body shape numerically on a simplified sedan car [55]. a reduction of 13.23% aerodynamic drag has been achieved. numerical investigation has been carried out on an ahmed body with non-smooth dimpled surfaces on its slant back [56]. the geometry of non-smooth surfaces are shown in figure 19. in order to maximize the drag reduction performance of the dimpled non-smooth surface, an aerodynamic optimization method based on a kriging surrogate model was employed to design the dimpled non-smooth surface. four structure parameters had been selected as the design variables, and a 16-level design-of experiments method based on orthogonal arrays had been used to analyses the sensitivities and the influences of the variables on the drag coefficient; a surrogate model had been constructed from these. the results showed that the optimal combination of design variables can reduce the aerodynamic drag coefficient by 5.20%. a b figure 17: details of amd (a) attachment on ahmed body and (b) amd configuration [49]. figure 18: comparison of drag coefficient for sedan and wagon [51]. review on aerodynamic drag reduction of vehicles 10 figure 19: non-smooth dimpled surfaces [56]. 5 impact of combined flow control summary several flow control techniques have been investigated and implemented to reduce aerodynamic drag which is the main contributor to increase fuel consumption. each techniques has its unique advantages and disadvantages over each other. to achieve the best, combination of more than one technique would bring more advantages to obtain the desire drag reduction. the combination of blowing jets as active flow control and porous layer as passive flow control were implemented on an ahmed body and results showed that a drag reduction of 30% could be achieved [57]. 6 summary various flow control methods are discussed with their outcomes in the paper. some methods are applied individually and some are applied combined. to figure out the effectiveness of each control methods to reduce aerodynamic drag reduction, it would be better to represent them in a table with some graphical representation. a summary of drag reduction using various flow control techniques is shown in table 1. among various methods, it is found that combined control technique is more beneficial as it can reduce maximum drag reduction than single method. percentage of drag reduction by active and passive methods are graphically presented in figure 20 and figure 21 respectively. maximum contribution of drag reduction for different control methods is shown in figure 22. from the above analysis, it is seen that the drag reduction for active control system could be as much as 20% by using the pulse jet [31, 32] and plasma actuator [39] as shown in figure 20 and 22. on the other hand, for passive control system, the drag could be decreased to 21.2% by using flaps [50] as shown in figure 21 and 22. however, for combined flow control technique, the drag could be reduced as much as 30% by using blowing jets with porous layer [57] as shown in figure 22. table 1: summary of flow control methods on aerodynamic drag reduction types of control name of applied method percentage of drag reduction [reference] active flow control movable underbody diffuser 4% [18] steady blowing 1% [19], 6 to 10.4% [20, 21] , 6.4% [22], 5.7% [23], 11.1% [24], 9-14% [25], 2.6% [26] synthetic jets 4.29% [27], 8.5% (re = 1.2 × 10 6 ) and 6.5% (re = 1.9 × 10 6 ) [28] and 10% (re = 2.3×10 6 ) [29] pulsed jet 6 to 8% [30], 20% [31] and [32] steady suction 17% [33], 6% [34], 9.5% [35], 10% [36] plasma actuator 8% [37], 3.65% [38], 20% [39] passive flow control vortex generator 12% [40], 2.2% [41], 10% [42] and [46], 11.7% [43], 4.2% (sub) and 10% (ahmed body) [44], 4.53% [45] spoiler 5% [47] flaps 17.6% [48], 19% [49], 21.2% [50] body modification 10% [51], 8.4 % [53], 5.639% [54], 13.23% [55], 5.20% [56] combined flow control blowing jets with porous layer 30% [57] mukut and abedin (2019): international journal of engineering materials and manufacture, 4(1), 1-14 11 bar chart reference bar chart reference bar chart reference bar chart reference bar chart reference [18] [23] [27] [31] [36] [19] [24] [28] [33] [37] [20, 21] [25] [29] [34] [38] [22] [26] [30] [35] [39] figure 20: percentage of drag reduction by active control methods. bar chart reference bar chart reference bar chart reference bar chart reference [40] [44] [49] [54] [41] [45] [50] [55] [42] [47] [51] [56] [43] [48] [53] 0% 5% 10% 15% 20% 25% movable underbody steady blowing synthetic jets pulsed jet steady suction plasma actuator d r a g r e d u c t i o n ( % ) active control methods 0% 5% 10% 15% 20% 25% vortex generator spoiler flaps body modification d r a g r e d u c t i o n ( % ) passive control methods review on aerodynamic drag reduction of vehicles 12 figure 21: percentage of drag reduction by passive control methods. figure 22: maximum contribution of drag reduction for different control methods. 6 conclusions the vehicle aerodynamic drag is the main contributor to increase the fuel consumption which affects not only the world fuel reserves but also the environment. thereby, reducing aerodynamic drag is the best solution for the greener world as well as for the fuel hike. various flow control methods have been tested and validated numerically and experimentally of whose, most of the cases, simplified ahmed body has been chosen. the major findings from the present review analysis may be summarized as follows: 1. passive flow control methods employ the additional shape on the vehicle body which affect the flow field thus desirable impact on drag reduction. but these methods are sometimes added extra drag due to its shape. besides their attachment on vehicle body are little bit complex. 2. on the other hand, active flow control systems come in action only when it is necessary to control the flow. their attachments are little bit easier than passive flow control. main disadvantage of active flow control is that these require power to come in action which increase power consumption of vehicles. 3. the research outcomes about the drag reduction of vehicle from these control methods have been discussed in this review paper. it is conjectured that the drag reduction for active, passive and combined control systems could be as much as 20%, 21.2%, 30%, respectively. references 1. wood, r. m. (2004). impact of advanced aerodynamic technology on transportation energy consumption. sae technical paper, 2004-01-1306. 2. levin, j., & rikdal, r. (2011). aerodynamic analysis of drag reduction devices on the underbody for saab 9-3 by using cfd. master's thesis in automotive engineering, chalmers university of technology, sweden. 3. zhang, c., uddin, m., robinson, c., & foster, l. (2017). full vehicle cfd investigations on the influence of frontend configuration on radiator performance and cooling drag, applied thermal engineering, 130, 1328-1340. 4. regin, f. (2010). a numerical analysis on air-cooling performance of passenger cars. sae technical paper, 201001-0554. 5. aljure, d. e., calafell, j., baez, a., & oliva, a. (2018). flow over a realistic car model: wall modeled large eddy simulations assessment and unsteady effect. journal of wind engineering & industrial aerodynamics, 174, 225– 240. 6. matsumoto, d., haag, l., & indinger, t. (2017). investigation of the unsteady external and underhood airflow of the driver model by dynamic mode decomposition methods. international journal of automotive engineering. 8 (2), 55-62. 7. tian, j., zhang, y., zhu, h., & xiao, h. (2017). aerodynamic drag reduction and flow control of ahmed body with flaps. advances in mechanical engineering, 9(7) 1–17. 8. bansal, r., & sharma, r. b. (2014). drag reduction of passenger car using add-on devices. journal of aerodynamics, 2014, 1-13. mukut and abedin (2019): international journal of engineering materials and manufacture, 4(1), 1-14 13 9. mayer, w. & wickern, g. (2011). the new audi a6/a7 family aerodynamic development of different body types on one platform, sae international journal of passenger cars, 4(1), 197-206. 10. cattafesta, l. n., & sheplak, m. (2011). actuators for active flow control. annual review of fluid mechanics, 43(1), 247–272. 11. kourta, a. & gilliéron, p. (2009). impact of the automotive aerodynamic control on the economic issues. journal of applied fluid mechanics, 2(2), 69-75. 12. altaf a., omar, a., & asrar, w. (2014). review of passive drag reduction techniques for bluff road vehicles, iium engineering journal, 15(1), 61-69. 13. lee, s.w. (2018). computational analysis of air jet wheel deflector for aerodynamic drag reduction of road vehicle. microsystem technologies, 1–11. 14. hucho, w. h. & sovran, g. (1993). aerodynamics of road vehicles. annual review of fluid mechanics, 25(1), 485-537. 15. bellman, m., agarwal, r., naber, j., & chusak, l. (2010). reducing energy consumption of ground vehicles by active flow control. asme. energy sustainability, asme 4th international conference on energy sustainability, 1, 785-793. 16. song, j., yoshioka, s., kato, t. & kohama, y. (2006). characteristics of flow behind a passenger vehicle. sae technical paper series, 2006-01-1030. 17. hucho, w-h. (1990). aerodynamics of road vehicles-from fluid mechanics to vehicle engineering, butterworthheinemann, germany. 18. kang, s. o., jun, s. o., park, h. i., song, k. s., kee, j. d., kim, k. h., & lee, d. h. (2012). actively translating a rear diffuser device for the aerodynamic drag reduction of a passenger car. international journal of automotive technology, 13(4), 583-592. 19. heinemann, t., springer, m., lienhart, h., kniesburges, s., & becker, s. (2014). active flow control on a 1: 4 car model, exp fluids 55: 1738, 1-11. 20. mestiri, r., ahmed-bensoltane, a., keirsbulck, l., aloui, f., & labraga, l. (2014). active flow control at the rear end of a generic car model using steady blowing. journal of applied fluid mechanics. 7(4), 565-571. 21. roumeas, m., gilli´eron, p., & kourta, a. (2009). analysis and control of the near-wake flow over a square-back geometry. computers & fluids 38(2009), 60–70. 22. wassen, e. & thiele, f. (2008). drag reduction for a generic car model using steady blowing, 4th flow control conference, aiaa, 2008-3771. 23. krentel d., muminovic, r., brunn, a., nitsche, w., & king, r. (2010). application of active flow control on generic 3d car models. active flow control ii. springer, 108, 223-239. 24. wassen e., eichinger s., & thiele f. (2010). simulation of active drag reduction for a square-back vehicle. in: king r. (eds) active flow control ii. notes on numerical fluid mechanics and multidisciplinary design, 108, 241-255. 25. aubrun, s., mcnally, j., alvi, f, & kourta, a. (2011). separation flow control on a generic ground vehicle using steady microjet arrays. experiments in fluids. exp fluids (2011) 51, 1177–1187. 26. jonathan m., erik f., gregory r., rajan k., kunihiko t., farrukh a., yoshihiro y., kei, m. (2015). drag reduction on a flat back ground vehicle with active flow control. journal of wind engineering and industrial aerodynamics. 145 (2015), 292-303. 27. park, h., cho, j. h., lee, j., lee, d. h., & kim, k. h. (2013). aerodynamic drag reduction of ahmed model using synthetic jet array. sae international journal of passenger cars-mechanical systems, 6(1), 1-6. 28. kourta, a., & leclerc, c. (2013). characterization of synthetic jet actuation with application to ahmed body wake, sensors and actuators, a: physical. 192, 13-26. 29. tounsi, n., mestiri, r., keirsbulck, l., oualli, h., hanchi, s., & aloui, f. (2016). experimental study of flow control on bluff body using piezoelectric actuators. journal of applied fluid mechanics. 9(2), 827-838. 30. joseph, p., amandolese, x., & aider, jl., (2012). drag reduction on the 25° slant angle ahmed reference body using pulsed jets. exp. fluids, 52, 1169–1185. 31. bideaux, e., bobillier, p., fournier, e., gilliéron, p., el hajem, m., champagne, j.y., gilotte, p., & kourta, a. (2011). drag reduction by pulsed jets on strongly unstructured wake: towards the square back control. international. journal of aerodynamics, 1(3/4), 282-298. 32. gillieron, p., & kourta, a. (2013). massive separation control analysis of the pulsed jet actuators effects, mechanics & industry, 14, 441–445. 33. kourta1, a. & gilliéron, p. (2009). impact of the automotive aerodynamic control on the economic issues. journal of applied fluid mechanics, 2(2), 69-75. 34. lehugeur, b., gilliéron, p., & kourta, a. (2010). experimental investigation on longitudinal vortex control over a dihedral bluff body. exp. fluids, 48, 33–48. 35. wassen, e. & thiele, f. (2009). road vehicle drag reduction by combined steady blowing and suction. aiaa 2009-4174. 36. whiteman, j. (2016). active flow control schemes for bluff body drag reduction. msc engineering thesis, ohio state univ. 37. boucinha, v., weber, r., & kourta, a. (2011). drag reduction of a 3d bluff body using plasma actuators. international journal of aerodynamics, vol. 1(3/4), 262-281. review on aerodynamic drag reduction of vehicles 14 38. shadmani, s., nainiyan, s. m. m., ghasemiasl, r., mirzaei, m., & pouryoussefi, s. g. (2018). experimental study of flow control over an ahmed body using plasma actuator. mechanics and mechanical engineering, 22(1), 239– 251. 39. khalighi, b., ho, j., cooney, j., neiswander, b., corke, t., & han, t. (2016). aerodynamic drag reduction investigation for a simplified road vehicle using plasma flow control. proceedings of the asme 2016 fluids engineering division summer meeting. 40. aider, jl., beaudoin, j., & wesfreid, j. e. (2010). drag and lift reduction of a 3d bluff-body using active vortex generators. exp. fluids, 48, 771–789. 41. kim, i. & chen, h. (2010). reduction of aerodynamic forces on a minivan by a pair of vortex generators of a pocket type. international journal of vehicle design, 53(4), 300-316. 42. pujals, g., depardon, s., & cossu, c. (2010). drag reduction of a 3d bluff body using coherent streamwise streaks. exp. fluids, 49, 1085–1094. 43. krajnovic, s. (2014). les exploration of passive flow control around an ahmed body. journal of fluids engineering, asme transaction, 136(12), 1-28. 44. mazyan, w. i. (2013). numerical simulations of drag-reducing devices for ground vehicles. msc engg. thesis, american university. 45. shankar, g. & devaradjane, g. (2018). experimental and computational analysis on aerodynamic behavior of a car model with vortex generators at different yaw angles. journal of applied fluid mechanics, 11(1), 285-295. 46. filip, g., maki, k., bachant, p., & lietz, r. (2018). simulation of flow control devices in support of vehicle drag reduction. sae technical paper, 2018-01-0713. 47. kim, i., chen, h., & shulze, r. (2006). a rear spoiler of a new type that reduces the aerodynamic forces on a mini-van," sae technical paper 2006-01-1631. 48. beaudoin, jf. & aider, jl. (2008). drag and lift reduction of a 3d bluff body using flaps. exp. fluids, 44, 491501. 49. kim, d., lee, h., yi, w., & choi, h. (2016). a bio-inspired device for drag reduction on a three-dimensional model vehicle. bioinspiration & biomimetics, 11(2), 1-13. 50. tian, j., zhang, y., zhu, h., & xiao, h. (2017). aerodynamic drag reduction and flow control of ahmed body with flaps. advances in mechanical engineering, 9(7), 1-17. 51. marklund, j., lofdahl, l., danielsson, h., & olsson, g. (2013). performance of an automotive under-body diffuser applied to a sedan and a wagon vehicle. sae international journal of passenger cars, 6(1), 293-307. 52. unni, t. p. a. (2017). numerical investigation on aerodynamic effects of vanes and flaps on automotive underbody diffusers. sae technical paper, 2017-01-2163. 53. cho, j., kim, tk., kim, kh., &yee, k. (2017). comparative investigation on the aerodynamic effects of combined use of underbody drag reduction devices applied to real sedan. international journal of automotive technology, 18(6), 959–97. 54. song, k.s., kang, s.o., jun, s.o., park, h. i., kee, j. d., kim, k. h., & lee, d. h. (2012). aerodynamic design optimization of rear body shapes of a sedan for drag reduction. international journal of automotive technology, 13(6), 905–914. 55. hu, x., yang, b., lei, y., wang, j., li, x., liao, l., & xu, t. (2016). automotive shape optimization using the radial basis function model based on a parametric surface grid. proceeding of international mechanical engineering, part d: journal of automobile engineering, 1–14. 56. wang, y., wu, c., tan, g., & deng, y. (2016). reduction in the aerodynamic drag around a generic vehicle by using a non-smooth surface. proceeding of international mechanical engineering, part d: journal of automobile engineering, 1–15. 57. bruneau, ch., creusé, e., depeyras, d., gilliéron, p., & mortazavi, i. (2010). coupling active and passive techniques to control the flow past the square back ahmed body. computers & fluids, 39 (2010), 1875–1892. international journal of engineering materials and manufacture (2019) 4(1) 27-32 https://doi.org/10.26776/ijemm.04.01.2019.04 s. kamaruddin and m. a. h. a. latif department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia e-mail: shafie@iium.edu.my reference: kamararuddin and latif (2019). application of the bees algorithm for constrained mechanical design optimisation problem. international journal of engineering materials and manufacture, 4(1), 27-32. application of the bees algorithm for constrained mechanical design optimisation problem shafie kamaruddin and mohd arif hafizi abd latif received: 12 november 2018 accepted: 09 january 2019 published: 01 march 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 abstract optimisation is a technique or procedure to find the optimal or feasible solution whether it is to minimise or maximise by comparing other possible solutions until the best solution is found. nowadays, many optimisation algorithms have been introduced due to the advancement of technology such as teaching learning based optimisation (tlbo), ant colony optimisation (aco), particle swarm optimisation (pso) and the bees algorithm. the bees algorithm is considered as one of the best optimisation algorithms because it has been successfully solved different type optimisation problem from in various field. it is inspired by the foraging behaviour of honeybees in nature. this study applies the bees algorithm to minimise the mass of disc clutch brake in its design. to find the optimal solution for the multiple disc clutch design, the bees algorithm is applied and found better result compared to other optimisation algorithms that already have been used. keywords: bees algorithm, optimisation algorithm, multiple disc clutch problem 1 introduction in this era, many problems need optimisation regardless to minimise or maximise. for examples, minimise (cost, weight, time) and maximise (profit, performance). optimisation technique is a procedure to find the optimal solution whether it is minimisation or maximisation by comparing other possible solutions until the satisfactory solution is found. this technique finds the combination of parameters or variables to maximise or minimise objective functions subject to some constraints. one of the methods to solve the optimisation problem is using optimisation algorithms. there are many types of algorithms available today to find the optimal solution such as ant-colony algorithm, the bees algorithm, teaching-learning based optimisation and particle swarm optimisation. the bees algorithm is considered as among the best optimisation algorithms because it has been successfully solved different types of optimisation problems (hussein et al., 2016). it is inspired by the foraging behaviour of honeybees in nature. multiple disc clutch brake problem is one of the common problems faced in real world problem and it has been applied by other algorithms. this problem requires finding the best combination of design variables (optimal design) at a minimum weight. despite it has been applied by other algorithms, applying the bees algorithm on this problem would be interesting in term of exploring the capability of the bees algorithm in different problem. the significant of this research output would contribute in finding best design variables at minimum weight compared with other algorithms, which will improve the efficiency in product design management. for this reason, this problem was selected to test the performance of the bees algorithm. this study also provides other alternative algorithm in solving this problem. the main objective of this problem is to find the best combination of variables of multiple clutch brake design with minimum mass and satisfy all the constraints. 2 the bees algorithm 2.1 bees in nature a colony of bees always has some of its population to be used as scout bees to scrutinize the surrounding of their hive for potential patches of flower. the process of foraging starts when the scout bees are sent to the space and move randomly from one patch to another patch. then, the scout bees return to the hive and inform other bees in application of the bees algorithm for constrained mechanical design optimisation problem 28 the hive about the quality and location of a food source by performing a dance called “waggle dance”. it will recruit other bees to exploit high potential location while other scout bees will continue to find new patches (pham et al., 2009). in this foraging behaviour, the bees need to divide their workforce to each task with proper number of bees. they also must flexible enough to adapt to any environment changes. there are many mechanisms on how a colony of bees regulates the division of labour between the scouts and the recruits (beekman et al., 2007). based on these behaviours, several bees inspired algorithms have been established such as artificial bee colony (abc) algorithm, bee colony optimisation algorithm (bco) and the bees algorithm (karaboga & basturk, 2007; nikolić & teodorović, 2013; pham & castellani, 2015). although, all these algorithms are similar in term of inspiration from bees foraging behaviour, but each algorithm has its own work mechanism. this study focuses on one of the algorithms, which is the bees algorithm. 2.2 description of the bees algorithm the bees algorithm uses the same concept as the food foraging behaviour of honey bees in the nature. it was introduced by a group of researchers from cardiff university (pham et al., 2006). it works by sending the scouts bees to explore for potential solutions. then, the potential sites found are exploited and better solution will attract more recruits. this process continues iteratively until the best solution has been found. the flow chart of the bees algorithm is shown in figure 1 (pham & castellani, 2009). the first step of the bees algorithm is setting the parameters which are number of scout bees (n), number of best sites selected out of n sites(m), number of elite sites selected out of best sites(e), number of bees recruited for elite sites (nep), number of bees recruited for the other selected sites (nsp), patches size (ngh) and number of unselected scout bees (n-m). the next step of the bees algorithm is sending n scout bees randomly (random initialisation) across the search space. after that, each position visited by the scout bee is evaluated via fitness function and ranked according to it fitness value. once the positions visited by the scout bees have been ranked, local search is performed by sending recruit bees (nep and nsp) to selected elite sites and best sites. elite sites attract more recruit bees compared to best sites. these recruit bees are placed randomly across patch size of the selected sites. if the recruit bees found better fitness value compared to the followed scout bee of the selected site, it will replace the scout bee as the new scout bee. if the recruit bees failed to find better fitness value, the scout bee remains as scout bee for that patch. as for the remaining unselected scout bees, they are sent randomly across the space to find new patches (global search). at the end of each iteration, a new population is formed consists of best recruit bees from each patch and unselected scout bees. the stopping criterion can be set either based on predefined threshold or predefined number of iteration (pham & castellani, 2009). figure 1: flowchart of the bees algorithm kamaruddin and latif (2019): international journal of engineering materials and manufacture, 4(1), 27-32 29 2.3 multiple disc clutch problem the objective is to minimise the mass of the multiple disc clutch brake design, which consists of five discrete variables; inner radius, ri, outer radius, ro, thickness of the discs, t, actuating forces, f, and number of friction surfaces, z (rao et al., 2011). figure 2 shows the schematic of multiple disc clutch used for this application. the objectives function and constraints for this problem are shown in appendix. figure 2: multiple disc clutch schematic 3 methodology this study started with background study or reviewing the articles, journals and books related to the problem. the articles are about the optimisation algorithm, specifically the bees algorithm and the mechanical design problem, which is multiple disc clutch. then, writing the code in open source software known as r-software and run the code. most of optimisation algorithms require fine-tuning of parameters to find the best solution. thus, several set of parameters were selected for this experiment. for each set of parameters, the algorithm was run 100 times. the result of best fitness value, worst fitness value, mean, standard deviation and successful rate found over 100 runs of each set of parameters were recorded. the criteria in determining the best result is based on the mean of fitness values found over 100 runs. the set of parameters that generated the best result are shown in table 1. the stopping criterion for this experiment was set based on number of function evaluations, which are 1000 function evaluations. this means the algorithm was stopped once it reached maximum number of evaluations for each run. next, results of this experiment were compared with other optimisation algorithms available in the literature. the best result found was compared with other optimisation algorithms available in the literature. most of results in the literature do not provide the standard deviation value of their results. thus, the comparison is in term of mean value only. the value of variables and constraints are also shown and compared between those different optimisation algorithms. table 1: set of parameters of the bees algorithm parameters value n 14 e 2 nep 11 ngh 3 m 4 nsp 4 application of the bees algorithm for constrained mechanical design optimisation problem 30 4 results and discussions 4.1 results the multiple disc clutch brake design problem was also solved by nsga-ii, tlbo, abc, and apso. table 2 shows the statistical comparisons of other optimisation algorithm results with the bees algorithm. the best value of the mass of the multiple disc clutch brake found by the bees algorithm is 0.313657 kg. this value is similar with tlbo and abc, but better compared to the results of nsga-ii and apso. table 3 shows the combination of variables found by the bees algorithm corresponding to the best fitness value over 100 runs. in most cases, the combination of variables is similar with other algorithms as the best fitness value is similar with tlbo and abc. despite statistical result, comparison shows that tlbo achieved better successful rate (sr) compared to the bees algorithm, but the bees algorithm showed less variability of the result with standard deviation only 0.008631. in terms of other statistical results such as worst and mean fitness values found, the bees algorithm also shows better results compared with other optimisation algorithms. figure 3 and figure 4 show the comparison of convergence rate for the bees algorithm and abc algorithm respectively. from figure 4, it is observed that the convergence rate for the tlbo method is faster than abc in the early stage of the search. then, both found almost similar fitness value until at the end of the search. this could have contributed to better successful rate of tlbo compared to abc algorithm and the bees algorithm. table 2: result comparison with other optimisation algorithms best worst mean sr sd tlbo (rao et al., 2011) 0.313657 0.392071 0.327166 0.67 n/a abc (rao et al., 2011) 0.313657 0.352864 0.324751 0.54 n/a nsga-ii (debb & srivinasan, 2006) 0.4704 n/a n/a n/a n/a apso (ben guedria, 2016) 0.337181 0.716313 0.506829 n/a 0.09767 bees algorithm 0.313657 0.345022 0.320761 0.41 0.008631 table 3: values of objectives functions, design variables and constraints variables tlbo (rao et al., 2011) nsga-ii (debb & srivinasan, 2006) abc (rao et al., 2011) apso (ben guedria, 2016) bees algorithm x1 70 70 n/a 76 70 x2 90 90 n/a 96 90 x3 1 1.5 n/a 1 1 x4 810 1000 n/a 840 990 x5 3 3 n/a 3 3 f(x) 0.313657 0.4704 0.313657 0.337181 0.313657 g1 0 0 n/a 0 0 g2 24 22 n/a 24 20 g3 0.919428 0.9005 n/a 0.922273 999.902 g4 9830.371 9.7906 n/a 9.824211 9999793 g5 7894.697 7.894 n/a 7.738378 7894.697 g6 0.702013 3.3527 n/a 1.396611 3.23794 g7 37706.25 60.625 n/a 48.84837 59418.75 g8 14.29799 11.6473 n/a 13.60339 11.76206 kamaruddin and latif (2019): international journal of engineering materials and manufacture, 4(1), 27-32 31 figure 3: convergence plots for the multiple disc clutch brake using bees algorithm figure 4: convergence plots for the multiple disc clutch brake using the tlbo and abc algorithms (rao et al., 2011). 4.2 discussions the results of the bees algorithm were compared with the results of other algorithms to compare it performance. some of these optimisation algorithms also share almost similar work mechanism with bees algorithm. the abc, apso and the bees algorithm are in the same category of swarm-based optimisation. the bees algorithms and abc use the concept of exploration and exploitation, while apso focuses more on exploration. meanwhile, nsga-ii and tlbo have their own search mechanisms. tlbo uses the concept of learning process in a class with certain number of student (population) and subject (variable) and ngsa is a type of evolutionary algorithm. as shown it table ii, it is observed that three out of five (abc, tlbo and the bees algorithm) optimisation algorithms able to find similar best solution, which is 0.313657 kg. the remaining two algorithms (ngsa-ii and apso) found worse solutions where, apso obtained 0.337181 kg and nsga-ii obtained 0.4704 kg. in term of mean’s value and standard deviation’s value, the bees algorithm achieved better value, which is 0.320761kg and 0.008631 respectively. the successfulness of the bees algorithm and abc algorithm in finding the best solution could due their similarity of work. 5 conclusions in this work, a swarm based optimisation algorithm named the bees algorithm is applied to constrained mechanical design problem (multiple clutch brake problem) and its performance is compared with other algorithms. the results obtained show that the bees algorithm found similar best fitness value compared with other algorithms at similar computational effort (number of function evaluation). despite the best fitness, value found is similar with other optimisation algorithms such as tlbo algorithm and abc algorithm, the bees algorithm has fewer variations with better mean and standard deviation. in conclusion, this research showed: 1. the successfulness of applying the bees algorithm to find the best solutions for mechanical design optimisation problem. 2. despite the best fitness value is similar with other algorithms, the bees algorithm found better results in term of mean and standard deviation which are 0.320761kg and 0.008631 respectively. 3. the capability of applying the bees algorithm to more complex optimisation problem. application of the bees algorithm for constrained mechanical design optimisation problem 32 acknowledgement the authors are grateful to the department of manufacturing and materials engineering, international islamic university malaysia for giving the opportunity to complete this study. appendix: objective functions and constraints the objective is to minimize the mass of the multiple disc clutch brake using five discrete variables: inner radius (ri=60, 61, 62, . . . , 80), outer radius (ro= 90, 91, 92, . . . , 110), thickness of discs (t = 1, 1.5, 2, 2.5, 3), actuating force (f = 600, 610, 620, . . . , 1000) and number of friction surfaces (z = 2, 3, 4, 5, 6, 7, 8, 9). minimise: f (x) = π(ro 2 − r i 2 )t(z +1)ρ subject to: g1(x) = ro −ri − ∆r ≥ 0, g2(x) = lmax−(z +1)(t +δ) ≥ 0, g3(x) = pmax −prz ≥ 0, g4(x) = pmaxvsrmax−przvsr ≥ 0, g5(x) = vsrmax−vsr ≥ 0, g6(x) = tmax −t ≥ 0, g7(x) = mh−sms ≥ 0, g8(x) = t ≥ 0, where mh = 2 3 𝜇𝐹𝑍 𝑟𝑜 3−𝑟𝑖 3 𝑟𝑜 2−𝑟𝑖 2 , prz = 𝐹 𝜋(𝑟𝑜 2−𝑟𝑖 2) , vsr = 2𝜋𝑛(𝑟𝑜 3−𝑟𝑖 3) 90(𝑟𝑜 2−𝑟𝑖 2) , t = 𝐼𝑧𝜋𝑛 30(𝑀ℎ+𝑀𝑓 ) , ∆r = 20mm, tmax = 3mm, tmin = 1.5mm, lmax = 30mm, zmax = 10, vsrmax = 10 m/s, 𝜇= 0.5, s = 1.5, ms = 40 n m, mf = 3 n m, n = 250 rpm, pmax =1mpa, iz = 55 kg mm 2 , tmax = 15 s, fmax = 1000n, rimin = 55mm, romax = 110mm. references 1. beekman, m., gilchrist, a. l., duncan, m., & sumpter, d. j. t. (2007). what makes a honeybee scout? behavioral ecology and sociobiology, 61(7), 985–995. 2. ben guedria, n. (2016). improved accelerated pso algorithm for mechanical engineering optimisation problems. applied soft computing journal, 40, 455–467. 3. deb, k., & srinivasan, a. (2006). innovization: innovating design principles through optimisation. proceedings of the 8th annual conference on, 1629–1636. 4. hussein, w. a., sahran, s., & sheikh abdullah, s. n. h. (2016). the variants of the bees algorithm (ba): a survey. artificial intelligence review, 1–55. 5. karaboga, d., & basturk, b. (2007). a powerful and efficient algorithm for numerical function optimization: artificial bee colony (abc) algorithm. journal of global optimization, 39, 459–471. 6. nikolić, m., & teodorović, d. (2013). empirical study of the bee colony optimization (bco) algorithm. expert systems with applications, 40(11), 4609–4620. 7. pham, d. t., & castellani, m. (2009). the bees algorithm : modelling foraging behaviour to solve continuous optimisation problems, proceedings of the institution of mechanical engineers, part c: journal of mechanical engineering science, 223(12), 2919–2938. 8. pham, d. t., & castellani, m. (2015). a comparative study of the bees algorithm as a tool for function optimisation. cogent engineering, 2(1), 1091540. 9. pham, d. t., ghanbarzadeh, a., koc, e., otri, s., rahim, s., & zaidi, m. (2006). the bees algorithm–a novel tool for complex optimisation. proceedings of the 2nd international virtual conference on intelligent production machines and systems, 454–459. 10. pham, d. t., ghanbarzadeh, a., otri, s., & koç, e. (2009). optimal design of mechanical components using the bees algorithm. proceedings of the institution of mechanical engineers, part c: journal of mechanical engineering science, 223(5), 1051–1056. 11. rao, r. v., savsani, v. j., & vakharia, d. p. (2011). teaching–learning-based optimisation: a novel method for constrained mechanical design optimisation problems. computer-aided design, 43(3), 303–315. international journal of engineering materials and manufacture (2016) 1(2) 35-50 https://doi.org/10.26776/ijemm.01.02.2016.01 hasan, m. s. 1 . , mazid, m. a. 2 , and clegg, r. e. 3 1 science and engineering faculty, queensland university of technology, brisbane, australia 2 school of engineering and information technology, federation university, gippsland, australia 3 school of engineering and technology, central queensland university, rockhampton, australia e-mail: m2.hasan@qut.edu.au reference: hasan, m. s., mazid, m. a., and clegg, r. e. (2016). the basics of stellites in machining perspective. international journal of engineering materials and manufacture, 1(2), 35-50. the basics of stellites in machining perspective md shahanur hasan 1 , md abdul mazid 2 , and richard e. clegg 3 received: 28 october 2016 accepted: 24 november 2016 published: 20 december 2016 publisher: deer hill publications © 2016 the author(s) creative commons: cc by 4.0 abstract stellites are cobalt (co)-based superalloys available in two main combinations: (a) a tungsten (w) group with composition of co-cr-w-c, and (b) a molybdenum (mo) group containing co-cr-mo-c. stellites possess outstanding corrosion resistance, oxidation resistance, wear resistance, heat resistance, and low magnetic permeability. components made of stellites work well in highly corrosive environments and maintain these advantageous properties at elevated temperatures. components made of stellites are widely used in the oil and gas, automotive, nuclear power, paper and pulp, chemical and petrochemical, refineries, automobile, aerospace and aircraft industries. by virtue of their nonmagnetic, anticorrosive and non-reactivity to human body-fluid properties, stellites are used in medical surgery and in surgical tools, tooth and bone implants and replacements, heart valves, and in heart pacemakers. the hardness range of stellites is from 32 to 55 hrc, which makes stellites brittle materials but they have a low young’s modulus. due to their high hardness, dense but non-homogeneous molecular structure and lower thermal conductivity, machining operations for parts made of stellites are extremely difficult, categorising stellites as difficult-to-machine materials like ti-alloys, inconels, composites and stainless steels. usually, machine components made of stellites are produced by a deposition method onto steel substrates instead of expensive solid stellite bars. the rough surfaces of deposited stellites are then finished by grinding, rather than some other economic machining process, which is costly and time-consuming, making stellite products very expensive. this paper provides a basic overview of stellites applicable in engineering, their significances and specific applications, advantages and disadvantages in respect of machining processes. a brief review on experimental research on economically rational cutting parameters for turning operations of stellite 6 using coated carbide inserts is presented in this paper. interesting facts on the residual stresses induced by machining processes in stellite 6 are revealed and analysed. the microhardness variation of machined surfaces of stellite 6 using different tool geometries is investigated in this research review. it is revealed that coated carbide inserts with a medium-size nose radius perform better in respect of hardness changes and heat generation, producing minimum phase changes on machined surfaces of stellite 6. keywords: cobalt alloys; stellites; difficult-to-machine; residual stress; surface roughness; surface integrity; manufacturing processes. 1 introduction the machinability of a material largely depends on its physical, chemical and metallurgical characteristics. consequently the surface integrity (residual stress distribution, microhardness, phase changes, plastic deformation, micro-cracking, tears and laps related to built-up-edge formation) and surface topology (surface roughness and waviness) of machined parts are directly determined by these characteristics, as well as by the machining regimes/parameters selected, machine tool dynamics, cutting-tool material and geometry, and cooling fluid. as revealed, out of these variables, adequate and optimal cutting parameter selection plays the most significant role. the major quality assurance of machined parts checks geometric accuracy, surface roughness and residual stress levels of the machined parts. all these parameters and the factors related to surface integrity are largely dependent on the selected cutting regimes for machining a given material using a given cutting tool on a certain machine tool. the basics of stellites in machining perspective 36 therefore researching for optimal cutting regimes/parameters for machining a certain material using certain cutting inserts is the topmost priority in machining research. all other research relevant to machining would be accurate and effective if the optimal cutting regimes have been used for machining the samples under investigation. nevertheless, the selection of cutting regimes, the right cutting tools and adequate machine tools is the appropriate solution to the most economically effective and sustainable manufacturing. at the same time, it is always more effective to know about the science of a material (in respect of chemistry, metallurgy, strength properties, application perspectives and motivation) prior to starting dealing with it, particularly in the case of its processing or designing. this paper deals with the basic but essential knowledge and information on stellites that would be helpful for researchers, scientists, engineers and professionals dealing with cobalt-based alloys, particularly in machining these and other superalloys. 2 history of stellites stellites have an inspirational history since their origin. elwood p. haynes, known as one of the two first inventors who created the horseless cart for the first time in human history, in his laboratory, developed a number of cobaltbased metal alloys for producing various critical parts of internal combustion engines and for tougher lathe tools for machining his horseless cart’s components and he named these alloys "stellites" in the 1900s [1]. haynes derived this name from the latin word “stella” that stands for “star” because of their star-like lustre. the hardness of these alloys is very high in relation to other metals and metal alloys; they possess high wear resistance, corrosion resistance and ability to maintain these extraordinary properties at extreme temperatures for long periods of time. initially haynes developed a nickel-chromium (ni-cr) alloy and a cobalt-chromium (co-cr) alloy and got these two superalloys patented in 1907. following his subsequent research haynes produced two new groups of cobaltbased alloys with the addition of tungsten (w) and molybdenum (mo). he added these two new alloys under the group-name “stellites” and these were patented in 1912. haynes developed stellite alloys in his laboratory for producing new corrosion resistant and heat tolerant metals for automobile parts, dental instruments, surgery tools, sharp-edged tools, cutlery, metal machining tools, and many other applications requiring anticorrosion, high wear resistance, high hardness and heat tolerance for longer periods of time. haynes was granted another patent in 1913 for development of another complex superalloy of cobalt-chromium-molybdenum-tungsten-carbon (co-cr-mo-wc) known as haynes alloy 6b. nowadays, many stellite alloys are produced with combinations of various amounts/proportions of cobalt, chromium, molybdenum, tungsten, titanium, nickel, iron, aluminium, carbon, boron, manganese, phosphorus, silicon and sulphur. by virtue of their low magnetic permeability and excellent anticorrosive properties some of the stellites are extremely suitable for medical surgery, dental implants, bone replacement, artificial heart valves, and heart pacemakers. due to their high hardness and good ductility, highly dense molecular structure, harder and more regularly organised carbides, lower thermal conductivity, tendency to resist plastic deformation having lower young’s modulus, stellites and other cobalt-based alloys, like titanium alloys, are categorized as difficult-to-machine materials due to their poor machinability. the machinability of a material is defined by the surface roughness quality and the surface integrity obtained, the tool life, heat generation in the cutting zone, chip formation difficulties, material removal rate (mrr) and power consumption, machine tool dynamics, and other parameters involved in metal machining. difficult-to-machine materials are materials which produce excessive tool wear, excessive cutting forces causing high heat generation, difficulties in chip formation resulting in poor surface finish during machining operations. one of the important phenomena in machining of difficult-to-machine materials is excessive heat generation in the cutting zone causing very high temperature growth in the primary and secondary shear zones which in turn causes phase changes in machined surfaces and the built-up-edge (bue) causing, in turn, premature cutting-tool damage. due to the poor machinability of the co-alloys most components made of these alloys are produced by precision casting, powder metallurgy and sintering, and finished by grinding and unconventional machining techniques (edm, lbm, etc.) [2, 3, 4, 5]. this leads to lower productivity and a high manufacturing cost of coalloy components, especially for medical implants such as hip and dental implants. 3 chemical composition and mechanical properties of stellites stellites are cobalt (co)-based superalloys. cobalt is a tough silver-grey metal of low magnetic permeability with a faint bluish tinge. cobalt appears in a cph structure at below 421c, and above this temperature it appears in a fcc crystal lattice structure. cobalt has a high radioactive curie point/temperature (1121c) and it possesses a high damping characteristic due to its ductility. these properties make cobalt a useful ingredient/inclusion for alloys subjected to vibration and to high temperature [2, 3, 6]. cobalt exists in 26 isotopes ranging from co-50 to co-75. co-59 is the only stable isotope amongst them. cobalt has a magnetic permeability about 2/3 of that of iron, making cobalt alloys the second best non-magnetic biomaterials following ti-alloys. the density of cobalt is 8.90 gm/cc and the atomic mass is 58.9332 amu. the melting point of cobalt is 1495c [6]. all of these attributes are advantageously used in enhancing the properties of stellites (co-alloys). addition of cobalt to metal cutting tool materials contributes to a lower friction coefficient in the cutting zone (interaction of cutting tool and work-piece material) and it helps to maintain red hardness. cobalt-based alloys are useful in applications requiring higher corrosion resistance, wear resistance, high strength at elevated temperature, and they perform well in aggressive hasan et al. (2016): international journal of engineering materials and manufacture, 1(2), 35-50 37 chemical environments. stellites are also applicable in areas where high creep resistance, structural stability, resistance to thermal creep and resistance to thermal corrosion are required [2, 4, 7, 8]. as mentioned earlier, currently two main combinations of stellites are available. w-containing co-cr-w-c combinations: such as stellite 6, stellite 12, stellite 1 and stellite 190, and mo-containing co-cr-mo-c combinations: such as stellite 706, stellite 712, stellite 701 and stellite 790 [6, 9]. a higher percentage of chromium (cr) in them provides stellite alloys with high corrosion and wear resistance at high temperatures and good magnetic properties. chromium acts as a carbide former and is a most important strengthening element in the alloy matrix. chromium also provides the alloys with excellent corrosion resistance and anti-oxidation. tungsten (w) and molybdenum (mo) are major elements of stellites which enhance the strength of the alloy matrix. molybdenum contributes to improved hardness forming hard and stable carbides in alloys. molybdenum itself has the sixth-highest melting point (2623c) in known materials. tungsten (w) as an alloying element provides hardness with enough ductility, high density and high red hardness. carbon provides alloys with a lower electrical conductivity but the highest thermal conductivity. carbides in stellites provide high hardness and red hardness for alloys. the formation of hard carbides in stellite alloys provides sliding wear and abrasion wear resistance and the chromium carbide (cr-c) matrix provides resistance to galling, cavitations and corrosion. stellites exhibit excellent metal-on-metal anti-galling behaviour [3]. table 1 below shows the chemical composition of various grades of stellites while table 2 shows the mechanical properties of some of the stellites available [6]. as table 2 shows, the coefficient of elongation of stellites 1, 6 and 12 is very low while those of stellites 6b and 21 are high enough to suit various applications. accordingly stellites 6b and 21 have relatively lower hardness and a higher percentage of elongation providing higher ductility, making them suitable for purposes requiring less brittleness, while these stellites are used as excellent biomaterials. harder stellites, such as stellite 6, are used for hard-facing slurry valves for uses in alumina refineries where the wear and corrosion rates are very high [8, 9, 10, 11]. these valves need to be machined precisely in order to provide better matching of functional surfaces to prevent fluid leakage and to prevent excessive wear and corrosion in the valves. a better surface finish of machined surfaces also decreases the occurrence of corrosion and corrosion-based fatigue cracking. the excellent properties of co-alloys are attributed to the crystallographic nature of cobalt, the solid-solutionstrengthening effect of chromium (cr) and molybdenum (mo), the formation of extremely hard carbides and the corrosion and wear resistance imparted by chromium. tungsten (w) in cobalt alloys provides high density creating high hardness and red hardness with substantial ductility as well as high heat tolerance. molybdenum (mo) in cobalt alloys promotes hard and stable carbides in alloys. as mentioned earlier, molybdenum itself has the sixthhighest melting point (2,623c) within the known metals. table 1: chemical composition of stellites (weight %) trade name of alloy co cr w mo c fe ni si mn tungsten (w) containing stellite 1 48.2 30 13 …. 2.5 3 1.5 1.3 0.5 stellite 4 46.43 30 14 …. 0.57 3 3 2 1 stellite 6 43.2 29 4.5 …. 1.2 3 3 1.5 1 stellite 12 47.4 30 8.3 … 1.4 3 1.5 0.7 2.5 stellite 23 bal 24 5 … 0.4 1 2 0.6 0.3 stellite 31 bal 25.5 7.5 … 0.5 2 10.5 1 1 stellite 190 bal 26 14.5 …. 3.3 3 3 2 1 stellite 306 bal 25 2 … 0.4 … 5 … … stellite f bal 25 12.3 .… 1.75 3 22 2 1 stellite 6b bal 30 4 …. 1 3 25 0.7 1.4 molybdenum (mo) containing stellite 712 bal 29 … 9 1.8 2.5 2.5 1 0.5 stellite 21 bal 27 … 5.5 0.25 3 2.75 1 1 stellite 27 bal 25 … 5.5 0.4 1 32 0.6 0.3 table 2: mechanical properties of stellites trade names of alloys density, ρ (g/cm³) yield strength, sy (mpa) ultimate tensile strength, sut (mpa) melting range t ⁰c) hardness (hrc) % elongation thermal conductivity λ (w/m. k) tungsten (w) containing stellite 1 9.16 … 618 125555 <1 … the basics of stellites in machining perspective 38 1290 stellite 6 8.9 541 896 12851395 40 1 … stellite 12 9 649 834 12801315 48 <1 … stellite 6b 8.84 619 998 12651354 37 11 14.82 molybdenum (mo) containing stellite 21 8.8 494 694 11861383 32 9 14.5 stellite 712 8.7 … … 11281236 48 … … 4 industrial applications of stellites the justification behind using stellites in engineering industry is to provide a corrosion-resistant and wear-resistant surface which will help combat the wear and corrosion of mechanical components. however, wear-resistant materials having a uniformly distributed, dense carbide matrix are naturally difficult to machine due to their high carbide content. in some cases non-homogeneous hard carbide distribution, lower heat conductivity, and high hardness contribute to poor machinability for these materials [11]. cobalt-based alloys are sometimes non-magnetic, but high-strength materials. these alloys are renowned for their high wear, corrosion and heat resistance properties, possess high hardness but are ductile enough materials. these alloys nicely preserve their strength even at high temperatures for longer periods of time and they behave perfectly in corrosive and acidic environments. as mentioned earlier, cobalt-based alloys exhibit excellent resistance to degradation in the environment of human body fluid, which has led to their successful application in medical surgery and surgical implants. several medical tests have proven [1, 3, 9] that cobalt-based alloys are biocompatible and suitable for use as surgical implants and bone replacements. according to their applications the conventional co-alloys may be categorised [7] as follows:  wear-resistant alloys,  high-temperature alloys, and  corrosion-resistant alloys. stellite 6b and stellite 6k fall within the group of wear-resistant alloys possessing a high proportion (about 30%) of cr and about 65% of co. the high proportion of cr performs as the chief carbide former during alloy solidification, providing high strength. the excellent wear resistance for these alloys is attributed to the mostly uniform co-rich matrix of formed carbide grains. by virtue of its excellent wear resistance and toughness stellite 6 has been widely used in manufacturing of cutting bits for deep drilling equipment for mining purposes, rockcrushing rollers, cement and steel equipment, and conveyor systems, steam-turbine erosion shields, half sleeves and bushings where lubrication is inaccessible or effective lubrication is impossible. stellite 6k, having in its composition no molybdenum (mo) but 30% of cr producing quite high hardness (47 hrc), is highly suitable for producing cutting knives for uses in cutting of soft organic materials and vegetation materials such as tobacco. another alloy, stellite 3, containing 3 times as much tungsten (w) as stellites 6, 6b, and 6k, and having no mo is inferior to stellites 6, 6b and 6k in corrosive environments and is not recommended for uses in such situations. but by virtue of a higher carbon (c) content giving an increased volume fraction of carbides, stellite 3 is 3 to 4 times as wear-resistant as stellite 6 and twice as resistant as stellite 12. stellite 3 has a higher red hardness and resists galling like all stellite alloys. accordingly stellite 3 is recommended for manufacturing bearing balls and needles, sleeves and bushings, valve seat inserts in non-corrosive environments, surgical scissor inserts, burner nozzles, steelmill guide rolls and seaming rolls. stellites are highly useful and popular representatives of cobalt-based alloy groups. by virtue of their abovementioned superior mechanical properties stellites have, as mentioned earlier, applications in many industries such as oil and gas, automotive, aerospace, pulp and paper, food processing, wood and timber, nuclear industries and in medical surgery for producing surgical tools and human bone/part replacements. applications of stellites in various fields are summarized below industry-wise. oil, gas and mining industries most mechanical components in the oil, mining and gas industry are subjected to combinations of corrosion, abrasion, high pressure, galling and high temperature. cobalt-based alloys, such as stellites 6, 12, 21 and 6b, provide superior wear and corrosion resistance, consequently longer component life. wear-resistant stellites provide, it is said, peace of mind for oil, gas and mining exploration equipment manufacturers as well as for mineral explorers in the field [9]. the machine components made of stellites 6, 12, 21 and 6b commonly used in oil and gas industries are listed below: hasan et al. (2016): international journal of engineering materials and manufacture, 1(2), 35-50 39  mwd (measurement while drilling) and lwd (logging while drilling) internal wear tools such as rotors, stators, impellors, centralisers, erosion inserts, landing, wear and turbine sleeves, fishing heads;  filter screens;  kelly valve trim;  cages;  sucker rod couplings;  annular blow-out preventers;  balls and seats;  subsurface safety valves (flappers, darts);  drilling heads. as tables 1 and 2 show, stellites 6, 12 and 6b are tungsten (w)-rich alloys exhibiting very low coefficients of elongation (for metals close to 1%) and higher hardness ranging within 40-50hrc. stellites 6 and 12 contain a high percentage of chromium (cr) making them highly wear and corrosion resistant and improving hardness. all these properties make machine components highly survivable in the situation of on-shore and off-shore oil and gas plants and in deep drilling sites. chemical refineries, power and petrochemical industry wear and corrosion problems are said to be plagues in refinery industries. stellite 6 alloy solves this problem, giving longer life, reduced unplanned down time, and reduced maintenance expenditures. the major products made of stellites 6 and 12 for refineries and petrochemical industries are a variety of nozzles, thermowells, valves, valve seats, valve slides and balls, valve plugs, valve trim, components of fluidised catalytic cracking units and pump components. cast stellite pump casings and impellers exhibit maximum life. nozzles of various sizes and shapes are used in refining and petrochemical processing plants for injecting and introducing high-pressure steam, compressed air and hydrocarbon and other chemicals. air grid nozzles, reactor feed and other feed nozzles, regenerator air grid nozzles, steam stripping nozzles, orifice chamber nozzles are some of the nozzles made of stellites [9]. nozzles are designed and produced to retain their structural and dimensional integrity over a period of planned time. nozzles made of stellites 6 and 12 exhibit maximum life. these two cobalt-based alloys, as tables 2 and 3 suggest, contain in their composition about 30% of cobalt (co) while the chromium (cr) content is as high as 30% with a good percentage of tungsten (w). high proportions of co and cr in stellites 6 and 12 contribute to the longer life span of nozzles in refineries. various parts of power generation plants which are subjected to high heat, such as fuel nozzles, bushes, seals and retainers, diaphragms, shields, blades, and other critical parts are made of cobalt and nickel-based alloys, since parts of power plants require protection against high heat, wear, corrosion and fatigue. stellites 6 and 12 exhibit a very low coefficient of elongation (close to 1%) and so young’s modulus as well providing high hardness, dense microstructure, and very high anticorrosive and wear-resisting capabilities, providing the required physicomechanical properties for many parts in power and petrochemical industries and refineries. pulp and paper industry stellite alloys like stellites 6, 6b, 6k and stellite 12, delcrome 90 solve some of the pulp and paper industries’ toughest wear problems. examples of components made of these cobalt alloys used in pulp and paper industries are plug screw feeders, black-liquor spray nozzles, palm guides, steam nozzles, feed roll points, bottom slitter brands, sleeves and bushing. food processing industry stellites are used in components in the food processing industry where high wear resistance and excellent corrosion resistance are the main requirements. some examples of these products are various types of knobs, pins, bushes, plungers, cutlery, cooking ware, parts of food-processing machines and driver screws. wood and timber industry stellite-tipped disk-saw teeth give better surface finish and considerably longer operational times. although the stellite has a lower hardness than cemented carbide, it has greater wear resistance and it is tough and ductile enough to withstand shock. the products used in conjunction with automatic, long-life saw-tipping equipment are triangular and rectangular tips, round balls, triangular and trapezoidal rods. automotive industry the history of stellites has a direct link to the automobile industry. as mentioned at the beginning of this review paper, stellites were first developed by elwood p. haynes for producing various critical parts of his innovative horseless cart in 1900 in a township called kokomo in indiana. he used his newly patented cobalt-chromium alloys for producing parts of his internal combustion engines. haynes also found that some of these new cobalt alloys are more durable for lathe cutting tools than the stainless steels that he invented earlier [1]. usually stellite 6, stellite http://www.stellite.com/linkclick.aspx?link=249&tabid=242 http://www.stellite.com/linkclick.aspx?link=247&tabid=242 http://www.stellite.com/linkclick.aspx?link=244&tabid=242 http://www.stellite.com/linkclick.aspx?link=245&tabid=242 http://www.stellite.com/linkclick.aspx?link=246&tabid=242 http://www.stellite.com/linkclick.aspx?link=248&tabid=242 http://www.stellite.com/linkclick.aspx?link=248&tabid=242 http://www.stellite.com/linkclick.aspx?link=250&tabid=242 the basics of stellites in machining perspective 40 6b, stellite 12 and stellite f are used in automotive parts manufacturing nowadays and since the beginning of the twentieth century. some of these automotive parts are pins, bushings, spacers, shafts, wear inserts, washers, camshafts, cam lobes, valves, valve stem tips, valve seats, produced by various processes like casting, investment castings, powder metallurgy and plasma transferred arc (pta), and the thermal powder spray process is used for some parts [11, 12, 13, 14]. aerospace industry a variety of degradation problems exist in aircraft engines as a result of metal-to-metal wear, fretting, hot corrosion, particle erosion plus others. this degradation is accelerated due to the high temperatures involved. some stellite alloys, such as stellite 31, stellite 6, stellite 6b, stellite 3 and stellite 19, are used in order to increase the life of certain aircraft engine components [11]. parts produced using the above-mentioned stellites are flare castings, spacer sleeves, rod end bearings, ball bearings, bearing races, fuel nozzles, swirlers, washers, engine vanes, bearing supports and other static structural parts. stellite 21 and stellite 31 alloys are used for producing cast turbine blades which are used in military piston engines on a number of aircraft. medical implants, ancillary and instrumentation stellites are extensively used in medical equipment by virtue of their wear resistance and corrosion resistance. another auxiliary purpose of stellites invented by haynes was to produce cutlery, surgical and dental instruments, sharp-edged tools which have to be anticorrosive for easy cleaning and to keep the sharpness for the longer periods of time essential for surgical purposes. for surgical tools stellites are used for scissor inserts, needle-holder inserts and other surgical tools. stellites, and to a larger extent ti-alloys, have huge, and in some cases unique, industrial and biomedical applications summarized below. these days cobalt and nickel-based alloys are used to produce dental prostheses which are economically cheaper than gold and silver-based alloys but provide adequate quality. kennametal stellite produces various dental stellites for making dental crowns, bridges and dentures [3]. as stated, these are their cocr and nicr alloys they produce for the dental industry. in biomedical applications metallic biomaterials are used for manufacturing of 70-80% of implants. in implant manufacturing cobalt-based alloys (co-alloys) are improvements on ti-alloys by the criterion of biocompatibility [4]. in specific cases co-alloys perform better than ti-alloys by virtue of their ductility. cobalt-chromium alloys (cocr alloys) exhibit the highest wear resistance and higher strength compared with stainless steels and ti-alloys, though stainless steels have better ductility and cyclic twist strength than ti-alloys and co-alloys. on the other hand, ti-alloys contain nickel (ni) which has been recently proven to be toxic for the human body, making these alloys less biocompatible than co-alloys. other applications of stellites in human bone replacement and the surgical industry are unicompartmental tibial components, spacer tibial components, rotating tibial components for knee prostheses and press-fit ace tabular cups for hip prostheses. other fields of application stellites are applied in the nuclear industry, e.g. impeller bearings for slurry pumps operated in nuclear waste tanks. some products made from cobalt-based alloys are wires, plates and welding electrodes. stellites are used for making searchlight reflectors for the navy and are also used for making lathe cutting tools in rare cases. 5 stellite production processes as mentioned earlier, not many publications on the machining of stellites are available except some on precision casting, powder technology with sintering methods, and coating technology using stellites. stellite alloys are hard, wear and corrosion resistant, but producing stellite products is highly expensive. appropriate machining processes of stellites other than grinding have not been yet developed. a literature survey proves that a little work has been done on deposition, cladding, welding and spraying [15, 16, 17, 18]. stellites are used in most cases in the form of coating, powder and casting onto stainless-steel or mild-steel substrates. it is also possible to restore worn surfaces of structural and mechanical components to their original features by making stellite coatings. powder metallurgy processes are advantageously used to produce unique components of machines from stellite alloys. various processes of stellite deposition techniques are briefly described below. laser cladding in the laser cladding deposition method, powder particles are deposited onto the steel plate, and the powder is melted by the laser beam before reaching the surface. one, two or five consecutive layers are produced; samples are displayed below in figure 1 [15, 18]. surface treatment adds value to the products. this process is used for both used and new surfaces to revitalise the worn or damaged surfaces as well as to improve the surface quality for new products. the dimensional accuracy obtained with this method is low. therefore it becomes necessary to lay down larger amounts of filling materials than are actually needed and then the surface is ground and if necessary polished. this makes the production highly expensive. hasan et al. (2016): international journal of engineering materials and manufacture, 1(2), 35-50 41 plasma transfer arc (pta) as figure 2 shows, the specimen is placed under a plasma torch and the plasma jet uniformly traversed above the pre-placed layer. after cladding by this system, the specimen has to be slowly cooled down to avoid cracking during the cooling stage [15]. sodium water glass is used as binder for a pre-placed layer in this process. as a part of their research project on cutting parameter optimisation for stellite 6, hasan et al [19, 20, 21, 22] produced stellite 6 samples by the powder deposition method onto steel substrates using a plasma transfer arc (pta) system as shown in figures 3 and 4. the steel substrate of aisi 4140 was preheated to 260⁰c using an oxyacetylene torch and allowed to soak to an average preheat temperature of 150⁰c prior to deposition. as shown in figure 3, the stellite 6 powder was deposited at a rate of 11.5 gm/min using the pta system at 120 a and 26.2 v, while the bar was rotated at 1.5 rpm and the pta bead was moved along the bar at a pitch of approximately 8 mm to provide a continuous layer of stellite 6 on the bar of approximately 250 mm length. four bars of stellite 6, for machining experiments, were produced in this manner, with three bars having a single layer of stellite and one bar having two layers of stellite. one of the problems with a single layer of stellite is that dilution of the stellite by the predominantly iron substrate tends to alter the properties of the material, whereas the outer layer of the two-layer system will have significantly less dilution. sintering this is a method of producing machine parts from powder materials by compacting the powder in a mould and then heating the compressed parts in a sintering furnace. sintering strengthens the bonds between the powder metal particles. the sintering process is carried out in two ways. in one way, one of the constituents of the compact melts and in the other way the constituents of the compact do not melt. for example, sintering of cemented carbide is done above the melting point of the cobalt constituent. carbon atoms appear to dissolve into the cobalt at points of high energy levels to build bridges between the grains. as an example for none-melting constituents, sintering of iron, copper or tungsten powder is done at 60% to 80% of the melting temperature. the atoms at the points of contact blend together and transfer. spark sintering is another method which is carried out by placing loose powder in a die, passing a large current through it, and applying pressure at the same time. figure 1: schematic representation of powder-coated products figure 2: schematic diagram of plasma arc cladding process the basics of stellites in machining perspective 42 figure 3: plasma arc cladding unit figure 4: steel bar heating process 6 difficulties of stellite machining as stellite alloys are so hard and tough, it is very difficult to machine them, and as a result parts made of stellite alloys become highly expensive. generally, items made of stellites are precisely cast, so that minimal machining is required. in most cases, machining is done by grinding rather than by oblique cutting, which is another costly operation. by the nature of their deposition, stellites become difficult-to-machine. the major causes of poor machinability of stellites can be summarized as follows:  extremely hard carbides and non-uniform hardness along the surface due to non-homogeneous distribution of carbides;  non-homogeneous crystal structure; cobalt changes to fcc after 421c but at below 421c it appears as a cph crystallised structure;  hard cobalt-carbide growth in the structure of the machining zone subjected to high heat;  possible high-level residual stress development during cooling after deposition;  higher carbon content leading to dense carbide formation, making stellites have a relatively low thermal conductivity creating a relatively higher temperature in the cutting zone;  possible blow hole (micro and nano level) growth in the bulk material during stellite deposition. as mentioned earlier, a number of stellite 6 bars were produced using the plasma transfer arc (pta) method in this research. these stellite bars were used as sample work-pieces for a machinability study [19, 20, 21, 22]. the main theme of the current research was concentrated on optimal or rational cutting regimes (speed, feed rate, and depth of cut) development for stellite 6 that can achieve the least possible surface roughness for machining of stellite 6 using coated and uncoated carbide cutting tools but not compromising the geometric and surface quality and surface integrity. to prove that the newly developed optimal/rational cutting regimes are worthwhile, further research has been carried out to study the performance of the optimal cutting regimes in respect of the surface integrity, specifically the residual stress level developed in the machined sub-layer as a result of machining processes using the developed optimal cutting regimes for stellite 6. the current authors also examined and analysed the microhardness at various depths of the machined layer of stellite 6. this study gives an understanding of hardness variation, at various depths along and across the tested specimen, under the effect of the cutting forces and heat generated in the cutting zone. the heat generated in the cutting zone is capable of changing the metallographic phase, as well as the hardness, of machined surfaces. evidently there is a correlation between the residual stress level and the hardness of metal components. 7 residual stress development in the process of external static or dynamic loading (mechanical or thermal), materials are subjected to stresses. after removing the loading most of the stresses may be released but some portion of the stresses persists in the crystal lattice of materials and is called residual stress [21, 22, 23, 24, 25]. residual stresses are induced in sub-layers of machined surfaces due to the action of the cutting forces exerted by primary and auxiliary cutting motions which cause plastic deformation of the surface material during the machining processes. the heat generated in the cutting region is another major cause of residual stress development on the sub-layer of the machined surface. as a result of the cutting processes, residual stresses are developed in both longitudinal (direction of feed) and tangential (direction of cut) directions of the machined part. these unwanted residual stresses play a crucial role in the performance of machined parts and their durability. unfavourable residual stress development may cause hasan et al. (2016): international journal of engineering materials and manufacture, 1(2), 35-50 43 unacceptable deformation that may prevent the part from meeting the required dimensional tolerances. residual stresses can also affect the fatigue strength and fatigue life of the components. in a physical sense the crystal lattice is either compressed or strained in volume due to the residual stresses. accordingly residual stresses are considered as either compressive (positive) or strained (negative). the work of many researchers has revealed that both kind of residual stresses reside in the metal structure simultaneously, forming a neighbourhood. in metal machining processes the cutting forces, causing plastic deformation at the cutting zone to create chips and subsequently causing high temperature (in some cases up to 2900c) growth, contribute to the development of residual stresses in the sub-layer of machined surfaces. researchers agree that residual stresses affect only the upper/outer layer of a component to a depth of up to 500 µm, while at up to 50100 µm intense values of residual stresses are observed. it is known that the outer surface is more important for machine components in respect of all types of loadings (tensile, bending, moment, shear) as well as for wear and corrosion. that is why the quality and integrity of the outer surfaces of machine components are so crucial. negative residual stresses contribute to fatigue micro-crack creation as a result of creation (or a tendency to creation) of dislocation in the crystal lattice of machine components. it has been revealed that the residual stresses have a close relationship with the mechanical and metallurgical capabilities of parts, and these affect the phase transformation and topological states of machined parts. several authors indicate that strained or positive residual stresses may improve the surface integrity of products in certain cases. this is reasonable since it is assumed that the positive residual stress may contribute to some level of compaction of the crystal structure, improving the bonding and reducing or removing the dislocation in the crystal structure. at the same time it is logically understandable that both positive and negative residual stresses appear together in sequence. therefore a study of residual stress growth phenomena, and mechanical and metallurgical transformation in the sub-layer of machined parts, are equally vital for quality assessment of machined parts as are other parameters such as the surface roughness and geometric accuracy of the machined parts. at present various methods are available to measure residual stresses, such as incremental hole drilling, x-ray diffraction, hard x-rays, neutron diffraction, and ultrasonic waves. it has been revealed that the residual stresses on or in the machined surface greatly affect a part’s fatigue life, resistance to cracking, stress corrosion, static strength and magnetic properties [24, 25, 26, 27]. controlling residual stress development on the machined surface is a prerequisite for the successful application of materials, especially in the aerospace, automotive, nuclear, refinery and mining industries [27, 28]. pawade et al. established [33] that residual tensile stresses reduce the fatigue strength of machined parts, shortening the legitimate product life. it has been concluded that the residual stresses occur within a depth of 50 µm of the surface if sharp tools are used and up to 500 µm if worn tools are used. it has also been found that a build-up of residual strains can cause distortion of thin and/or long work-pieces. pawade et al. performed an experimental study on residual stress development for inconel 718 using an x-ray diffractometer method on machined surfaces using machining conditions of high cutting speed (475 m/min), low feed rate (0.05 mm/rev), medium depth of cut (0.5/0.75 mm) with a honed cutting edge, and they observed compressive residual stresses in sub-layer machined surfaces. likewise, hasan et al. found high-tensile residual stress when using a tool nose radius of 0.8 mm, and lower growth of residual stresses was observed at nose radii of 0.4 mm and 1.2 mm [19, 20, 21, 22]. outeiro et al. analysed [30] residual stresses of difficult-to-machine materials like inconel 718 and austenitic stainless steel aisi 316l along the round profile of the machined bar using x-ray diffraction after machining under various conditions with coated and uncoated cutting tools. they found that the occurrence of residual stresses is higher when machining with uncoated tools than with coated tools. they also found high-tensile residual stresses on the machined surface and compressive residual stresses in the subsurface. this phenomenon supports the proposition that both positive and negative residual stresses appear together. sailo et al. analysed residual stresses on turbine disks (made of inconel 718) of jet engines that were machined under various cutting conditions [35]. the tensile residual stresses were measured (ranging up to 800 mpa) on the disk surface and the authors deduced that these severely affected the life of the turbine disks. three different depths of cut (0.06 mm, 0.12 mm and 0.18 mm) were selected to investigate the residual stresses. as the graph in figure 5 shows, the worst condition was at the 0.06 mm depth of cut because this produced the lowest value of compressive residual stress (-100 mpa) and the highest value of tensile residual stress (800 mpa) [35]. the lowest tensile residual stress (500 mpa) was at the 0.18 mm depth of cut. it has been concluded that the residual stresses are one of the important parameters for measuring the quality and reliability levels of the machined surfaces and are more influential when machining critical structural components, which are widely used in nuclear power generation and in the aerospace industry [30, 32]. furthermore, residual stresses are a design factor for design engineers, especially for components for aerospace, nuclear and other critical engineering industries. component life is seriously shortened by residual stress development during machining. residual stresses may develop because of peening, machining, cold hole expansion, bending, welding, thermal stresses, and loading stresses. it can be seen that residual stress is an important parameter which can help to predict product life, quality and reliability. as mentioned it is a key parameter for design engineers and is a significant factor to consider when critical structural components are designed and manufactured, particularly for nuclear power generation and the aerospace industry. the basics of stellites in machining perspective 44 figure 5: residual stresses at different depths of cut 8 surface roughness and residual stress stellite 6 is a highly regarded engineering alloy and it has, as mentioned earlier, high heat resistance, corrosion resistance and wear resistance. as far as is known adequate machining techniques and processes have not yet been developed for stellite 6 other than that for grinding. a limited number of studies has been noticed in areas of machining of this valuable super alloy. ohtani et al. performed turning operations on stellite 6 using carbide inserts and cbn inserts and various cutting speeds, and found better values of surface roughness (ra) of 3.5 µm at 200 m/min cutting speed for cbn inserts and 4 µm at 30 m/min for carbide inserts [37]. the authors did not examine the effect of feed rate, depth of cut and tool nose radius on surface roughness. they also did not analyse the changes of surface properties of machined samples such as residual stress, microstructural changes and microhardness development on the machined surface. they did not analyse the chemical composition of the machined surface. recently, the current authors (hasan et al.) carried out [19, 20, 21, 22] a series of machining (turning) experiments on stellite 6 pta bars using titanium-nitride-coated inserts (figure 6: a, b, c) with various nose radii (0.4 mm, 0.8 mm and 1.2 mm), as shown in figure 6, on a harrison m400 lathe. other geometric parameters of these inserts are rake angle -6°, inclination angle -6°, lead angle 95°, clearance angle 0°, nose angle 80°. the results of the experiments are shown in the graphs in figures 7 and 8. the graph in figure 7 shows the variation of surface roughness obtained for different nose radii of the coated carbide inserts. it suggests that the use of cutting inserts with a higher nose radius reduces the surface roughness. a series of experiments was performed and it was found that the optimal tool nose radius for coated carbide inserts (for machining stellite 6) is 0.8 mm, which produced the best surface within the range of surface roughness ra = 0.6 µm 1 µm for variable cutting speed, feed rate and depth of cut. initially the optimal cutting parameters (speed, feed rate, depth of cut) for stellite 6 machining using different nose radii of coated carbide inserts to obtain the lowest value of surface roughness were established by a series of real-life experiments [19, 20, 21, 22]. the established optimal machining parameters to achieve the best surface roughness for machining stellite 6 using coated carbide inserts with various nose radii are recorded in table 3. moreover, hasan et al. experimented on and analysed [19, 20, 21, 22] the residual stress development in a machined surface of a stellite 6 bar using coated carbide inserts with three different nose radii (0.4 mm, 0.8 mm and 1.2 mm); the results obtained are shown graphically in figure 8. investigations with stellite 6 revealed that the measured values of residual stresses on the machined surface are lower for 0.4 mm and 1.2 mm nose radii (of coated carbide inserts) for both axis parallel and axis perpendicular x-ray deflection (xrd) methods as shown in figure 8. however, the stress values are comparatively higher for samples machined using a 0.8 mm nose radius of cutting tools. it has been observed that the maximum values of residual stress are 660 mpa and 300 mpa of strain for axis parallel and perpendicular directions respectively. the series of experimental investigations revealed the surprising fact that use of cutting tools with lower and higher nose radii for machining stellite 6 provides better results in the sense of residual stresses induced by the machining process, while a cutting tool with medium nose radius (0.8 mm) provides worse strain residual stress. hasan et al. (2016): international journal of engineering materials and manufacture, 1(2), 35-50 45 eventually, this may cause premature micro-crack initiation in sub-layers of components, which, in turn, reduces the fatigue life of products. the effect of machining or grinding will often produce a compressive residual stress in the surface of a component. guidance in the standard hs-784 residual stress measurement by x-ray diffraction indicates that even if a sample is mechanically polished to a 1 m metallographic finish, x-ray diffraction measurements typically measure a 50 mpa compressive residual stress induced by the polishing process, regardless of the underlying residual stress state. compressive residual stresses in the measurements here are therefore not unexpected, even though it is expected that the underlying residual stress state in the weld will be tensile in nature. table 3: optimal machining parameters for stellite 6 using coated carbide tools nose radius nr [mm] optimal machining parameters cutting speed v [m/min] feed rate f [mm/rev] depth of cut d [mm] 0.4 50 0.08 1.6 0.8 80 0.1 0.3 1.2 50 0.1 0.8 figure 6: coated carbide inserts figure 7: influence of nose radius on surface roughness the basics of stellites in machining perspective 46 figure 8: residual stresses, different nose radii, coated carbide 9 micro-hardness variation on machined surfaces residual stresses affect the hardness of the machined surface. also during machining the cutting zone of the workpiece is deformed plastically, causing work hardening of the machined surfaces. the micro-hardness in the machined surface region changes from the original hardness of the work-piece under all cutting conditions due to non-uniform heat generation and rapid cooling of the work-piece. as reported in [19], the author investigated the microhardness at various depths (up to about 500 µm) of a machined surface of stellite 6 that was machined by coated carbide inserts of three different nose radii (0.4 mm, 0.8 mm, and 1.2 mm). the microhardness at different points located at different depths of the machined surfaces was tested using a vickers hardness tester, model mh– 5. the results of the microhardness assessments are shown in graphical form in figure 9. the newly obtained optimal cutting parameters [19, 20, 21, 22] were used for preparing the samples for microhardness testing. this helped to assess the surface integrity of the newly established optimal cutting parameters for rational machining of stellite 6. as can be seen from the graph in figure 9, the surface microhardness is lower (39.6 hrc) at minimum depth for a sample which was machined using a 0.8 mm nose radius, and the microhardness values increase up to 48 hrc at 0.225 mm depth with increasing depth underneath the machined surface. for other samples produced using coated carbide inserts with 0.4 mm and 1.2 mm nose radii, the values of microhardness fluctuate slightly at various depths under the machined surface. higher values of microhardness have been observed on machined surfaces generated using a coated carbide insert with a 1.2 mm nose radius, and values increase with depth up to 0.25 mm. finally a downward tendency is found at large depth for all three samples. it is assumed that a small nose radius (0.4 mm) means that the sharp tool tip concentrates the cutting forces in a small area, which increases the strain on the machined surface. this causes a higher temperature in a small area and leads to hardness variations in the machined surface. on the other hand, a larger nose radius (1.2 mm) increases the cutting forces and produces more heat in the cutting zone. this heat causes plastic deformation and affects the surface hardness. 10 metallography of machined surface as been discussed above, there are changes in the residual stresses and microhardness of the machined surfaces, so changes in the metallographic microstructure have been observed in the investigation. a typical metallographic microstructure of a machined stellite 6 surface is presented in figure 10. the surface was produced [19, 20, 21, 22] by machining of stellite 6 pta using a coated carbide cutter and the optimal cutting regimes v = 50 m/min, f = 0.08 mm/rev, d = 1.2 mm and nose radius = 0.4 mm. the microstructure shows non-homogeneous carbide formation after the machining process. a series of experiments has revealed that the carbide formation is very different for samples machined with different cutting regimes. it appears that non-homogeneous hard carbide affects the surface roughness of the machined surfaces, which leads to rapid tool wear. it was also found that microstructural changes occurred due to the machining of stellite 6 using coated carbide inserts, because at and beyond 421c cobalt itself appears in a fcc crystal lattice structure rather than the cph structure which exists below 421c. as mentioned earlier the samples of stellite 6 bars were produced using the plasma transfer arc (pta) system by depositing a stellite 6 homogeneous mixture at the home of a local company. the composition used for manufacturing these sample bars agrees with the standard composition given in table 1. hasan et al. (2016): international journal of engineering materials and manufacture, 1(2), 35-50 47 figure 9: microhardness of machined surface of stellite 6 (using coated carbide inserts) figure 10: metallographic microstructure of stellite 6 in other works, the current authors performed a series of experiments [19, 20, 21, 22] using the manufactured samples of stellite 6 pta for optimisation of cutting regimes for stellite 6 using coated and uncoated carbide cutting tools, pcbn (poly-carbide boron nitride) and other advanced cutting tool materials by the way of real-life experiments. the surface integrity obtained after machining using the newly developed optimal cutting parameters/regimes has been also assessed and analysed. 11 conclusion this paper has attempted to provide an analysis of the superior and useful properties of stellites, a group of cobaltbased super alloys. it has focussed on specific applications of various grades of stellites, their mechanical and metallurgical properties and chemical compositions for many mechanically critical parts used in oil and gas industries, chemical refineries and the petrochemical industry, mining, pulp and paper industries, food processing the basics of stellites in machining perspective 48 industry, wood and timber industry, automotive and aerospace industries. it is believed that this paper will be an excellent and valuable source of basic but most essential information for researchers, scientists, engineers and professionals dealing with cobalt-based alloys. moreover this paper has attempted to briefly describe the applications of some ductile and low-magnetic-permeability cobalt alloys in dental implants and human bone replacements, manufacture of artificial heart valves and heart pacemakers. this scope may be further extended in another paper. chemical compositions and mechanical properties have also been collected in a table format for easy use for particular applications. there is a good prospect to improve the machining technique and the technology of stellites to overcome the machining difficulties. as parts made of stellites are widely used in various industries and very popular in specific applications, it is a big drawback that adequate machining processes for stellites have not yet been developed other than the costly and time-consuming technique of grinding. however, an attempt has been made to reveal the optimal machining parameters (cutting speed, feed rate and depth of cut) for a lower value of surface roughness for the purpose of successful machining of stellite 6 using new grades of coated and uncoated carbide inserts with various nose radii (0.4 mm, 0.8 mm and 1.2 mm). the observed phenomena relative to the machinability of stellite 6 are found to be directly related to the properties of stellites. an experimental study on residual stress growth on a machined surface of stellite 6 was performed in perpendicular and parallel to the directions of the axis of the machined bar. compressive residual stresses are observed (400 mpa and 300 mpa) for the nose radii of 0.4 mm and 1.2 mm. the residual stresses induced by the effect of the cutting process would have been superimposed on the residual stresses in the underlying weld structure, which are expected to be tensile and of a similar value to the yield stress of the stellite (approximately 600 mpa). the specimens machined using cutting tools with 0.4 and 1.2 mm tip radii appear to be more effective in masking the underlying residual stress state than the 0.8 mm tool tip. however, if compressive residual stresses can be induced in the surface of a component by manipulating machining parameters, this may be an effective way of reducing phenomena such as stress corrosion cracking and fatigue. from these experiments, it was found that cutting inserts with a 0.8 mm nose radius produced better values of surface roughness (figure 7) than with nose radii of 1.2 mm and 0.4 mm. however, 1.2 mm and 0.4 mm nose radii caused comparatively lower residual stress (figure 8) in the machined surface. a literature search found that not much has been published in relation to machining of stellites. stellites are useful for special purposes by virtue of their excellent physico-mechanical properties. due to their poor machinability stellites have been catagorised as difficult-to-machine materials. it is worthwhile to carry out more vigorous research on the machining and machinability of stellites for development of better machining processes and economically sustainable optimal machining parameters but not compromising the product quality and surface integrity of the machined products. acknowledgements the authors acknowledge the contribution of gary hoare at central queensland university australia and berg engineering, queensland, australia for their generous help in experiments. references 1. sponaugle, c. (2005). history of hynes international inc., pittsburgh engineer. quarterly publication of the engineers’ society of western pennsylvania winter, 7-9. 2. dhokia, s. v., & newman, s. t. (2012). environmentally conscious machining of difficult-to-machine materials with regard to cutting fluids. international journal of machine tools and manufacture, 57, 83-101. 3. marti, a. (2000). cobalt-base alloys used in bone surgery. injury, international journal of the care of the injured, 31(4), 18-21. 4. niinomi, m., nakai, m., & heida, j. (2012). development of new metallic alloys for biomedical applications. acta bimaterialia, 8, 3888-3903. 5. shao, h., li, l., liu, l. j., & zhang, s. z. (2013). study on machinability of a stellite alloy with uncoated and coated carbide tools in turning, journal of manufacturing processes, (15), 673-681. 6. asm handbook. (2009). retrieved from http://products.asminternational.org/hbk/index.jsp. 7. yao, m. x., wu, j. b. c., & xie, y. (2005). wear, corrosion and cracking resistance of some wor mocontaining stellite hard-facing alloys, material science and engineering a, 407, 234-244. 8. das, c. r., albert, s. k., bhaduri, a. k., & kempulraj, g. a. (2003). novel procedure for fabrication of wearresistant bushes for high-temperature application, journal of materials processing technology, 141, 60-66. 9. deloro stellite inc. (2009). retrieved from www.stellite.com. 10. bagci, e., & aykut, s. a. (2006). study of taguchi optimization method for identifying optimum surface roughness in cnc face milling of cobalt-base alloy (stellite 6), international journal of advanced manufacturing technology, 29, 940-947. 11. sims, c. t. (1972). cobalt-base alloys, the superalloys, john wiley and sons, 145. 12. yao, m. x., wu, j. b. c., xu, w., & liu, r. (2005). metallographic study and wear resistance of a high-c wrought co-based alloy stellite 706k. materials science and engineering: a, 407, 291-298. hasan et al. (2016): international journal of engineering materials and manufacture, 1(2), 35-50 49 13. ruml, z., & straka, f. a. (1995). new model for steam turbine blade materials erosion. wear, 186-187, 421424. 14. zhao, c., tian, f., peng, h. r., & hou, j. y. (2002). non-transferred arc plasma cladding of stellite ni60 alloy on steel. surface and coatings technology, 155(1), 80-84. 15. fouilland, l., el mansori, m., & gerland, m. (2007). role of welding process energy on the microstructural variation in a cobalt-based superalloy hardfacing. surface and coating technology, 201, 6445-6451. 16. barsoum, z., & lundback, a. (2009). simplified fe welding simulation of fillet welds – 3d effects on the formation of residual stresses. engineering failure analysis, 16(7), 2281-2289. 17. xueping, z., erwei, g., & liu, c. r. (2009). optimisation of process parameter of residual stresses for hard turned surfaces. journal of materials processing technology, 209, 4286-4291. 18. kaul, r., ganesh, p., tiwari, m. k., singh, a. k., tripathi, p., gupta, a., & nath a. k. (2002). laser assisted deposition of graded overlay of stellite 6 on austenitic stainless steel. laser in engineering, 12(3), 207-225. 19. hasan, m. s., mazid, a. m., & clegg, r. e. (2010). optimisation of the machining of stellite 6 pta hardfacing using surface roughness. key engineering materials, 443, 227-231. 20. hasan, m. s., mazid, a. m., & clegg, r. e. (2010). effect of cutting tool nose radius on surface roughness for stellite 6 machining using coated carbide insert. in proc. of the 6th australian congress on applied mechanics (acam 6 2010), perth, australia, 603-612. 21. hasan, m.s., mazid, a. m., clegg, r. e., & mcleod, a. (2010). residual stress analysis on machined surface in turning stellite 6. in proc. of the 6th australian congress on applied mechanics (acam 6 2010), perth, australia, 714-722. 22. hasan, m. s. (2011). optimisation of machining processes design for stellite 6, a wear resistant and difficult-tomachine material. master of engineering thesis, central queensland university, rockhampton, australia, 136. 23. hamiuddin, m. (1987). development of wear resistant strong and fully dense stellite by liquid phase sintering. powder metallurgy international, l 19(2), 22-26. 24. d’oliveira, a. s. c. m., da silva, p. s. c. p., & vilar, r. m. c. (2002). microstructural features of consecutive layers of stellite 6 deposited by laser cladding. surface and coatings technology, 153(2-3), 203-209. 25. guo, y. b., li, w., & jawahir, i. s. (2009). surface integrity characterization and prediction in machining of hardened and difficult-to-machine alloys: a state-of-art research review and analysis. machining science and technology, 13, 437-470. 26. arrazola, p. j., ozel, t., umbrello, d., davies, m., & jawahir, i. s. (2013). recent advances in modelling of metal machining processes. cirp annals – manufacturing technology, 62(2), 695-718. 27. jawahir, s., brinksmeier, e., m’saoubi, r., aspinwall, d. k., outeiro, j. c., meyer, d., umbrello, d., & jayal, a. d. (2011). surface integrity in material removal processes: recent advances. cirp annals – manufacturing technology, 60, 603-626. 28. brinksmeier, e., cammett, j. t., kbnig, w., leskovar, p., peters, j., & tonshoff, h. k. (1982). residual stresses measurements and causes in machining processes, annals of the cirp, 31(2), 491-510. 29. jang, d. y., watkins, t. r., kozaczek, k. j., hubbard, c. r., & cavin, o. b. (1996). surface residual stresses in machined austenitic stainless steel, wear, 194, 168-173. 30. wu, d. w., & matsumoto, y. (1990). the effect of hardness on residual stresses in orthogonal machining of aisi 4340 steel. trans, of the asme, j. of engineering for industry, 112(3), 245-252. 31. hua, j., shivpuri, r., cheng, x., bedekar, v., matsumoto, y., hashimoto, f., & watkins, t. r. (2005). effect of feed rate, workpiece hardness and cutting edge on subsurface residual stress in the hard turning of bearing steel using chamfer + hone cutting edge geometry. material science and engineering a, 394, 238-248. 32. wang, y. d., peng, r., wang, x. l., & mcgreevy, r. l. (2002). grain orientation-dependent residual stress and the effect of annealing in cold-rolled stainless steel. acta materialia, 50, 1717-1734. 33. pawade, r. s., joshi, s. s., & brahmankar, p. k. (2008). effect of machining parameters and cutting edge geometry on surface integrity of high-speed turned inconel 718. international journal of machine tools and manufacture, 48, 15-28. 34. outeiro, j. c., pina, j. c., m’saoubi, r., pusavec, f., & jawahir, i. s. (2008). analysis of residual stresses induced by dry turning of difficult-to-machine materials, cirp annals – manufacturing technology, 57, 77-80. 35. salio, m., berruti, t., & de poli, g. (2006). prediction of residual stress distribution after turning in turbine disks. international journal of mechanical sciences, 48(9), 976-984. 36. withers, p. j., & bhadeshia, h. k. d. h. (2001). residual stress part 1 – measurement techniques. material science and technology, 17, 355-365. 37. ohtani t., fujise, k., & yokogawa h. (1988). machining of stellite alloy with cbn and carbide tools, reports of the government industrial institute, chugoku (j) publisher, 30. 38. seco technical guide. (2009). turning difficult-to-machine alloys. 240. 39. radu, i., & li, d. y. (2007). the wear performance of yttrium-modified stellite 712 at elevated temperature. tribology international, 40, 254-265. 40. ning, y., patnaik, p. c., liu, r., yao, m. x., & wu, x. j. (2005). effects of fabrication process and coating of reinforcements on the microstructure and wear performance of stellite alloy composites. material science and engineering: a, 391(1-2), 313-324. the basics of stellites in machining perspective 50 41. costa, j. m., pires, j. t. b., antunes, f., nobre, j. p., & borrego, l. p. (2010). residual stresses analysis in ndyag laser welded joints. engineering failure analysis, 17(1), 28-37. 42. doyle, l., keyser, c. a., leach, j. l., schrader, g. f., & singer, m. b. (1985). manufacturing processes and materials for engineering, third edition, prentice-hall, inc., englewood cliffs, new jersey. 926. 43. yao, m. x., wu, j. b. c., xu, w., & liu, r. (2005). metallographic study and wear resistance of a high-c wrought co-base alloy stellite 706k. materials science and engineering: a, 407, 291-298. 44. cinca, n., lopez, e., dosta, s., & guilemany, j. m. (2013). study of stellite-6 deposition by cold gas spraying. surface and coating technology, 232, 891-898. 45. martin, c. l. (2007). alloys go with the grain (material science). nature, 445, 34-35. 46. benghersallah, m., boulanouar, l., le coz, g., devillez, a., & dudzniski, d. (2010). machinability of stellite 6 hardfacing. epj web of conferences 6, 02001 doi:10.1051/epjconf/20100602001. international journal of engineering materials and manufacture (2018) 3(4) 208-215 https://doi.org/10.26776/ijemm.03.04.2018.05 y. a. alazemi1 and e. y. t. adesta2 department of manufacturing and materials engineering international islamic university malaysia po box 10, 50728 kuala lumpur, malaysia 1e-mail: eng-yahya2000@hotmail.com 2e-mail: eadesta@iium.edu.my reference: alazemi, y. a. and adesta, e. y. t. (2018). implication of engineering project management in small and medium enterprise: malaysian perspective. international journal of engineering materials and manufacture, 3(4), 208-215. implication of engineering project management in small and medium enterprise: malaysian perspective yahya a. alazemi and erry y. t. adesta received: 31 august 2018 accepted: 13 september 2018 published: 01 december 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract integrated project management includes the collection, combination and coordination of project elements in becoming a set of project management. in this research, three important aspects of project management such as life cycles, success factors and areas of problem and solutions in small to medium enterprises (smes) are presented. a survey is conducted in malaysia in order to measure the degree of awareness and implementation of project management in smes. the collected data was analysed using statistical methods named statistical package for the social science (spss). the analysis showed that 80% of respondents with mean 1.20 and standard deviation 0.447 agree that project management is most important for company performance. only 66.7% respondents really understand the basics of project management. in terms of project goals, the most respondents stated that their project always met performance goals with 4.20 mean and 0.837 standard deviation. according to 80% of the respondents, planning and control are the main criteria to the success of projects and organization with 4.80 mean and 0.447 standard deviation. keywords: project management, life cycle, small and medium enterprise, sme, success factor 1 introduction nowadays, it is widely acknowledged that small and medium scale enterprises (smes) are the most important key in overall national development. they play an important role in the economy, both in terms of employment and economic development and growth. as a fact, according to sme annual report 2015/2016, smes consistently contributed to the increasing of percentage of gross domestic product (gdp), employment and export. smes contributed 36.3% to gdp in 2015 from only below 30% in 2005 while the employment share increase 8.7% from 56.8% in 2005 to 65.5% in 2015. in addition, exports also show better growth from 16.4% in 2010 to 17.6% in 2015 [1, 2]. back in 1996, small & medium industries development corporation (smidec) is a responsible agency to develop smes to be competitive in the global market. the year 2004 marks another chapter in smes history with the establishment of the national sme development council (nsdc) that responsible in formulating strategies, coordinating programs, encourage partnership and also to ensure the effective implementation in the development of smes across all economic factors. four years after nsdc was established, smidec took over again nsdc role in smes development. a year after, on 2 october 2009, smidec was officially rebranded to small to medium enterprise corporation malaysia (sme corporation malaysia) which now is the national organization central point regarding information and activities for the development of progressive smes through various platforms and programs. on the other hand, smes have various definitions with time, experience, country, context and global articulation of the smes catalytic role. according to economic census (2011), smes in malaysia are defined for only two sectors. the first one is manufacturing sector with a sales turnover of less than rm 25 million or less than 150 full time employees. the second one is service sectors which have a sales turnover of less than rm 5 million or less than 50 fulltime employee [3]. implication of engineering project management in small and medium enterprise: malaysian perspective 209 according to sme corporation malaysia in smes annual report 2015/2016, under manufacturing sector, they must have sales turnover not exceeding rm50 million or full-time employees not exceeding 200. apart from that, in services sales turnover not exceeding rm20 million or full-time employees not exceeding 75. to be specific about the definition, there are facts that all smes must be entities registered with ssm or other equivalent bodies. it however, excludes companies that are multinational corporations (mncs), government-linked companies (glcs) and state-owned enterprises [2]. smes need to build up their competitiveness and quality to match or exceed the competition where project management is the key for success and growth. project management was developed initially in the heavy engineering industries, particularly construction, defence, aerospace and shipbuilding [ 4 ] . it later evolved to address smaller projects and medium-sized projects in large firms [5] to establish discipline that helps in defining, plan and implement successful projects. the failure smes that practice project management is less in economic system. small firms have several disadvantages in innovation such as limited cash flow, knowledge and skills, and a low sales volume (rogers, 2004). in order to achieve economic development and growth, smes should spend 3 percent of their turnover on innovation. as such, the objectives of this research are as follows. 1. to measure the degree of awareness and implementation of project management in smes. 2. to identify problem areas in smes to apply integrated engineering project management. 3. to recommend solutions and way forward to apply integrated engineering project management for growth and sustainability of smes. the scope of this project is focusing on manufacturing sector of smes in malaysia and their practices with integrated engineering project management. a survey will be conducted using data collection questionnaire. then data will be analysed to make recommendations for applying integrated engineering project management. the significance of this study is that it will create awareness for the implementation of project management in smes manufacturing sectors. 2 literature review to define smes, according to the world bank, three quantitative criteria is used which is total assets in u.s. dollars, number of employees and annual sales in u.s. dollars. to be considered as micro, small or medium business, the enterprises must meet the requirement of those three criteria or at least one financial criteria. number of employees is the most common criteria that always use to define between medium, small and micro enterprise which is the largest number of sources to define smes in 2003, stated that smes must have a cut-off range of 0-250 employees. the european union has the most influence among all smes definitions. however, that definition is only limited for institutions and businesses seeking funding for it. according to the world bank statistics, out of 132 countries include in the research, 46 of them or a third define smes is an enterprise with less than 250 employees. however, each country has their own way to define smes specifically according to their own economy. table 1 shows the number of employees in different countries to classify the size of the company. concentrating on manufacturing, there is numerous number of sub-sectors as shown in table 2. from the statistics shown in table 2, the highest percent of the sector in smes is 24%, which is wearing apparel sector, drop to 15.14 per cent for food and beverages and 10.45 percent in metals products. these are top three sectors, which are more than 10 percent and have a high number of percent for a percentage of smes. on the other hand, the least concentration of smes that stay for two from the bottom were coke and refined petroleum products (0.17 per cent) and the last one is tobacco products (0.16 per cent). the regional orientation of manufacturing sector smes are listed in table 3. it shows that selangor has the highest number of smes with 8,314 establishments (22 %). this was followed by johor with 4,828 establishments (12.8 %) [1, 2]. table 1: size of firms by number of employees in different countries micro small medium sme large eu 1-9 10-49 50-249 1-249 250+ australia 0-9 10-49 50-199 0-199 200+ canada 0-9 10-49 50-499 0-499 500+ japan 4-9 10-49 50-249 1-249 250+ korea 5-9 10-49 50-199 5-199 200+ mexico 0-10 11-50 51-250 1-250 250+ new zealand 1-9 20-49 50-99 0-99 100+ turkey 1-19 20-49 50-249 1-249 250+ usa 1-9 10-99 100-499 1-499 500+ malaysia 1-4 5-74 75-200 5 200 200+ alazemi and adesta (2018): international journal of engineering materials and manufacture, 3(4), 208-215 210 table 2: number of smes in manufacturing sectors (economic census, 2011). sub-sector (manufacture) number of smes % smes wearing apparel 9,088 24.00 food products 5,731 15.14 fabricated metal products 3,958 10.45 printing and reproduction of recorded media 2,918 7.71 furniture 1,843 4.87 rubber and plastics products 1,756 4.64 wood and products of wood and cork 1441 3.81 other non-metallic mineral products 1,373 3.63 machinery and equipment 1,203 3.18 basic metals 1,083 2.86 chemicals and chemical products 961 2.54 textiles 959 2.53 repair and installation of machinery and equipment 913 2.41 paper and paper products 828 2.19 electrical equipment 622 1.64 computer, electronic and optical products 446 1.18 motor vehicles, trailers and semi-trailers 431 1.14 leather and related products 376 0.99 other transport equipment 328 0.87 beverages 285 0.75 basic pharmaceutical products and pharmaceutical preparations 192 0.51 coke and refined petroleum products 63 0.17 tobacco products 60 0.16 table 3: smes in the manufacturing sector by state (economic census, 2011) state in malaysia number of sme % of sme pahang 1,305 3.4 sabah 1,382 3.7 negeri sembilan 1,495 3.9 others 1,507 4.0 terengganu 1,782 4.7 kelantan 1,814 4.8 sarawak 1,977 5.2 pulau pinang 2,614 6.9 kedah 2,809 7.4 perak 3,833 10.1 w. p. kuala lumpur 4,201 11.1 johor 4,828 12.8 selangor 8,314 22.0 2.1 project management and life cycle classical management is usually considered to have five functions or principles which includes planning, organizing, staffing, controlling and directing. these days, project management can be defined in the view of short-term goals including planning, organizing, directing, and monitoring of company resources. in addition, it comes with a goal to complete particular goals and objectives that has been made earlier. the project management life cycle has four phases which is initiation, planning, execution and closure. macro and micro viewpoints are two different types of approach to determine the success of project management. in the macro viewpoint completion and satisfaction are the two criteria to measure project success. on the other hand, the completion criteria alone are sufficient for the micro viewpoint of project success. team members and project leader must discuss at the early stage of the project, which is initiation phase about the criteria in measuring project success. this will help them to prevent from heading in the wrong directions that will result in a failure of a project due to different objectives and goals toward a particular project [6]. many authors attempted to add more dimension to the basic elements o f p ro j e c t s u c c e s s . ex a m p le i n c lu de s customer satisfaction that is one of the most significant elements nowadays to measure performance along with the concept of total quality management (tqm) [7, 8]. http://www.method123.com/project-initiation-phase.php http://www.method123.com/project-planning-phase.php http://www.method123.com/project-execution-phase.php http://www.method123.com/project-closure-phase.php implication of engineering project management in small and medium enterprise: malaysian perspective 211 2.2 the way forward these ways forward proposing some solutions in dealing with problem areas associated with project management for successful economic growth in smes. 1. it has to be clear from the beginning that there will be regularly scheduled updates for the duration and tasks of the project. let everyone in the team know that status updates and progress are expected from them and they have to communicate clearly in any issues or delays in particular projects. 2. the project manager should start by calling the team together and delivering a presentation about the project management before execute and its significance towards everybody tasks. managers have to generate a sense of urgency about the project and how the project management will helps them to achieve objectives, leading the team to always think that they must always improve their knowledge in project management to complete their tasks in particular projects. 3. the project manager also responsible for figuring out who will be assigned to each task and for ensuring there's a fair allocation of talent and skills in each team member across projects. 4. an sme should have comprehensive reports and documentations on problem areas before project management implementations. this database could be used for planning and decision-making towards total elimination of all problems, especially regarding the project [ 9 . 5. for the government, there should be a law prohibiting noncertified project managers from handling projects to reduce failure in implementation of project management. with the best and certified project manager, rate of success will increase rapidly [9]. as a result, the problem of lack of knowledge and lack of experienced project manager will be decreased. 6. a successful project manager should always have weekly status meetings with team members, to check if everything was achieved as per the timeline, what issues happens that could disturb the project timeline. 7. to have more expertise in project management, higher educational levels should think to include project management as a compulsory subject especially in engineering program. they can consider putting this project management as a top program such as degree level [9]. 3 research methodology in the early initiative to boost the research knowledge, the author pursued literature search from related book, journal, research paper, dissertation, article, internet based reading material and anything related to any terms that was addressed. this is necessary for the author and the readers to understand what is project management and smes and the connection between project management and smes. the reviewed literature always regarding on project management, smes, and their connection. the history of project management as a starter, followed by definition and profile of smes. this paper also concludes project life cycle methodology, success factor and problem areas focusing on small to medium manufacturing (smes) area. at the end of the literature review, this paper gives the solution and ideas on how to solve the problem when applying project management in smes through a reading in journals and websites. to occupy in this research gap, the dissertation will combine all the facts, theories and others research paper gathered regarding project management and smes. to achieve the last objective, which is to measure the awareness and implementation of project management in small and medium enterprises (smes), survey will be conducted. the survey focuses on manufacturing related smes in the state of pahang and sarawak of malaysia. the company is chosen for sme corporation website. sme corporation malaysia is a central coordinating agency under the ministry of international trade and industry malaysia that formulates overall policies and strategies for smes and coordinates the implementation of smes development programs across all related ministries and agencies. subsequently, the company also must be in manufacturing related services. in this study, the company is chosen in pahang and sarawak only considering the largest state in peninsular east malaysia. data from respondent is gained through a questionnaire that was distributed to the engineer of the smes manufacturing companies. 3.1 questionnaire design a set of questionnaires have been designed in such a way to increase respondent’s interest regarding the topic, and easy to understand. the questionnaire is attractive, simple yet comprehensive and it is based on the objectives of the study. the beginning part in questionnaire aimed to identify the basic background of respondents, their position and experience in their company and to determine an organization of the company in general. in the first part, number of employees will be a key question in order to make sure that the respondents are in small and medium enterprises (smes). there are two sections in this questionnaire. section a is about project management in general. it is to measure the understanding of the respondents on project management concept. the respondents may hear and apply project management in their organization. section b is about the implementation of project management and whether respondents will be familiar with the project management tools or not. basically, section a and b are related to each other to make sure the reliability of the questions and also the results. alazemi and adesta (2018): international journal of engineering materials and manufacture, 3(4), 208-215 212 3.2 sample size one of the concerns in survey is the number of samples is needed. a larger sample can contribute to accurate results, but excessively big data is difficult to handle. there are many things that can affect how well our sample reflects the population and therefore how valid and reliable our conclusions will be [10]. the man characteristics of the company is the small and medium enterprises. to ensure that the company is smes, the company is chosen for sme corporation website. sme corporation malaysia is a central coordinating agency under the ministry of international trade and industry malaysia that formulates overall policies and strategies for smes and coordinates the implementation of smes development programs across all related ministries and agencies. subsequently, the company also must be in manufacturing related services. in this study, the company is chosen in pahang and sarawak only considering the largest state in peninsular east malaysia. data from respondent is gained through a questionnaire that was distributed to the engineer of the smes manufacturing companies. i. population size: in this report, the research only focuses on small to medium sized companies in the manufacturing sector. as a result, the population size for this research has been determined to be 50. ii. confidence interval: this confidence interval determines how close the answer of our sample to the true value in the population. the smaller confidence interval, the closer to the true value. in this survey, the confidence interval will be 5%. iii. confidence level: it defines the method to determine whether the sample accurately reflects the population. 95% confidence will be chosen and it will contribute to z score = 1.96 iv. standard of deviation: the value of variance expected in the response. the safest decision is to use 0.5. this is the most forgiving number and ensures that your sample will be large enough. 3.3 questionnaires distribution the set of questionnaires was distributed among the targeted respondent. type of respondent, which will be focusing on engineer position which was determined earlier so that it can meet the objectives with enough data to be collected. at first, the companies were selected on m a n u f a c t u r i n g sme. the details of engineer in sme and manufacturing companies were collected by a call to the company in the sme and as well as manufacturing. using google form that distributed through email. 3.4 survey analysis collected data were analysed using spss to ensure the reliability of the data. the data from the findings will be converted to mathematical data. it is more appropriate to have the data in mathematical form to allow greater understanding and efficiency. on the other hand, analysis can be done easily with mathematical data. the result from the software will stay as it is with the facts and figure provided by the software without any editing on its data to preserve the engineering ethics. 4 results and discussions a total number of 45 survey questionnaire has been distributed through email on november 2016 to study and measure the awareness and implementation of integrated project management in small to medium manufacturing companies (smes). to increase the number of possible respondents out of total distributed, the email was sent two times in one month by include form in an email and also by attaching the link in the email only. however, only five feedbacks received through giving the percentage 11.11% of the total survey distributed. the involved companies are: 4.1 reliability test in this study, reliability test is done in all area of study using statistical package for the social sciences (spss) software and value of cronbach’s alpha. ibm spss statistics version 23 was used in this study. from this software, value of cronbach's alpha is extracted to be use in analyzing the reliability of the data. in facts, cronbach’s alpha is a measure of internal consistency, that is, how closely related a set of items are as a group. it is considered a measure of scale reliability. this section discussed the reliability test on introduction to project management (section a). the number of items in section a is based on four statements of project management. all the 4 items in this section produce both 0.800 on cronbach’s alpha and cronbach’s alpha based on standardized items respectively. this section a also gives a mean value of 6, 0.5 for a variance and 0.707 for the standard deviation. in section b, number of items is based on all questions in that section. from the total time taken to finish a project, followed by project management tools. the remaining two are scale questions, which are on goals and objectives of a project according to a plan and also the important of success criteria in projects and organization (table 5). for both cronbach alpha and cronbach alpha’s based on standardized items giving the value 0.631 and 0.542. for all questions in this section, the value of the mean is 35.20, 10.200 for a variance and the last one is standard deviation which is 3.194 4.2 introduction of project management section a of the survey is related to introduction to project management. this section will be asked to achieve the last objectives, which is to measure the degree of awareness and implementation of project management in smes manufacturing companies. this introductory section is focused on awareness of project managements in small and implication of engineering project management in small and medium enterprise: malaysian perspective 213 medium manufacturing companies. the questions start with multiple-choice questions that asked the respondents either they have heard about project management and had implemented in their company or not. then, the following questions on a project management statement have a relation to the question before. the idea of this statement is about basic understanding and meaning of a project management. if the respondents have a basic knowledge and understanding of project management, they can answer the questions correctly. it is found that 80% of the respondents get the concept of project management clearly and the remaining need to improve to clear the confusion of project management. the majority has heard of project management and 80% on the next questions choose that project management is “very important” to their company performance. table 4: reliability test on implementation of project management (section a) reliability statistics cronbach's alpha cronbach's alpha based on standardized items no. of items .800 .800 4 summary item statistics mean minimum maximum range maximum / minimum variance n of items item means 1.500 1.200 1.800 .600 1.500 .120 4 scale statistics mean variance std. deviation n of items 6.00 .500 .707 4 table 5: reliability test on implementation of project management (section b) reliability statistics cronbach's alpha cronbach's alpha based on standardized items n of items .631 .542 12 summary item statistics mean minimum maximum range maximum / minimum variance n of items item m eans 2.933 1.400 4.800 3.400 3.429 1.937 12 scale statistics mean variance std. deviation n of items 35.2 10.2 3.194 12 4.3 implementation of project management time estimation to complete project leads the overall question in section b that is in the implementation of project management section. ‘iron triangle’ also includes in the life cycle elements of project management, which is planning, monitoring and control. it includes all aspects of a project to achieve the project objectives on time, within cost estimated and meet the quality and performance [7]. based on the results of time estimation question in the implementation of project management section, no respondents choose the answer not more than 12 months to complete a project from start to finish. this is a positive result, since they did not have to spend too much time on particular projects. therefore, the projects will achieve objectives that includes in ‘iron triangle’ that is completing a project on specific time. subsequently, respondents required to choose more than one answer on multiple-choice questions regarding project management tools. in a project, there are a large number of activities required in order to complete a project successfully. thus, to ensure alazemi and adesta (2018): international journal of engineering materials and manufacture, 3(4), 208-215 214 they are complete on schedule and to make sure that the project do not miss a deadline, project management tools is very helpful to be able to see everything that needs to be done. respondents will be able to choose this project management tool correctly if they are aware of project management. the type of questions that has specific answer will be able to measure the degree of awareness in project management. based on our data collected, 60% respondents answer this question correctly. it can be assumed that the respondents cannot differentiate clearly on project life cycle methodology and project management tools. they have some knowledge on project management, but it is not enough on particular aspects. schedule and performance as the project’s goals in five-scale question type, whether the following goals met the plan or not. the five scale points questions are divided into 1 = never met, 2 = seldom met, 3 = sometimes met, 4 = often met and 5 = always met. in addition, based on section a, 100% respondent’s response that they implemented project management in their project. therefore, this five-sca le question will be able to show us their effect on budget, schedule and performance when they apply project management. this can be one of the positive proofs when they apply project management in their project. based on the data collected, the least scale that chooses by the respondents is sometimes met which is scale 3. it is a good sign but its still cannot do 100% on scale 5 with budget, schedule and performance goals. from that response, they know and heard about project management but only apply a little bit of it. the following questions on the survey are still using fives c a l e question method. to be clear about the scale for the last part of the survey below, they are divided into 1 = not important, 2 = slightly important, 3 = important, 4 = fairly important and 5 = very important. there are 3 models of success factor criteria discussed in the literature review. there are pinto’s model of ten critical success factors, kerzner’s critical success factor and also belassi and tukel’s critical success factor. the implementation of project management will be shown from the results of four success criteria chosen generally. the first success criteria are top management support. in pinto’s model, top management support listed as one of the critical success factors in project management. kerzner’s model is using executive commitment and leadership approach that will be assumed as top management support from the executive and leadership words. the last one will be belassi and tukel’s model that divided the factors related to the project manager and the team members as well as organization. every single detail discussed in three models, explained about top management support. it is a strong point on critical success factor that will be a huge impact on the implementation of project management. based on the response in figure 5.5, it can be concluded that scale 4 and 5 only that had been chosen by the respondents. to get the support from top management support, project initiation must be applied. therefore, it is one of the proof that the respondent had implemented project management. to measure the degree of implementation of project management, success criteria can be part of the successful implementation of project management. clear goals and objective is chosen as one of the success criteria. according to figure 5.6, 80% choose clear goals and objectives as important to their projects and organization and the rest 20% choose very important in their response. project mission in pinto’s model, clear understanding of project management in kerzner’s model and factors related to the project from belassi and tukel’s model is included in clear goals and objective success criteria. to get clearer goals and objectives, they need to plan. planning is one of the aspect in the project management life cycle and it shows that they had implemented project management based on project planning. most of the respondents ( 80%) choose that it is very important for planning and control to their projects and organization. pinto’s model stated that project proposal and schedule as their critical success factor in their model. kerzner’s critical success factor stated the sixth points, w h i c h are commitment to planning and control and also belassi and tukel’s include factors related to the project and both for sure can be listed as critical success factors. again, project initiation and planning in project management life cycle involved in planning and control. the results indirectly show that all the respondents implemented project management when they choose fairly and very important planning and control of their projects and organization. more than half respondents, which are 60%, choose that it is very important to have an excellent project manager as success criteria for their projects and organization. personnel elements, monitoring and feedback element, communication element as well as trouble shooting element in pinto’s model need excellence project manager. on kerzner’s critical success factor, there is a strong point on excellent project manager. finally yet importantly, in belassi and tukel’s model, factors related to the project manager and team members are involved. thus, it can be assumed that excellence project manager leads to the positive results on the elements listed. based on the initiation phase in the project management life cycle, project manager and team are appointed. at this phase, it is very important to choose the most excellence project managers in order to make sure everything will be in control. as a conclusion, project initiation is involved and it shows that the respondents had applied the project management to their projects and organization. 5 conclusions and recommendations 5.1 conclusions the objectives of this project have been successfully achieved through the study of the project management approach for typical small to medium manufacturing companies in pahang and sarawak. these two states are selected because there is the largest state in peninsular and east malaysia. to start with the objectives of this implication of engineering project management in small and medium enterprise: malaysian perspective 215 report, this study helps to identify problem areas in applying project management in smes that focusing on manufacturing companies. the problem areas were discussed in general first before the scope of the topic is narrowing to be focused on small and medium manufacturing companies. when there is a problem, there is a way. therefore, to eliminate all the problems, this study also recommends solutions and ways forward against identified problem areas. finally yet importantly, the survey used in this study was to measure the degree of awareness and implementation of project management in small to medium manufacturing companies. in the survey, success criteria based on three success factor models in project management and smes operations were selected to design a question in section b. four success criteria are selected from success factor model listed in this literature review chapter. there are pinto’s, kerzner’s and also belassi and tukel’s critical success factors. these four criteria in threes u c c e s s factor model are selected because they give a huge impact on project management. using a survey conducted, data are collected and discussed. from our study, the level of awareness and implementation of project management especially is small and medium-manufacturing companies are quite satisfactory. most of the manufacturing companies are implementing project management, but the level is depending on the organization in the company itself. most of the problem and the solutions listed were from the organization itself. from top management to the workers itself, a project management concept must be fully understood by all levels in order to help the companies to gain the confidence that the project management can help the companies a lot to move forward. 5.2 recommendations it is strongly recommended that this project is taken for further analysis to increase the number of respondents as a number of manufacturers is increasing by the year. in facts, the respondents for this study have represented manufacturing companies with small to medium manufacturing companies because they are chosen from sme corporation malaysia website directory. sme corporation malaysia is the most reliable agency because it is a central coordinating agency under the ministry of international trade and industry malaysia furthermore; the respondents are from pahang and sarawak. this is because pahang is the largest state in peninsular malaysia and sarawak is the largest state in east malaysia. a further collection of data is needed not only the companies registered under sme corporation malaysia to increase the reliability of the findings. technique of conducting the survey must be improved since the response rates are low. apart from that, supporting letter from sme corporation malaysia also can be used as a platform to submit a survey questionnaire and develop communication with the respondent for further study. since the understanding of project management in small to medium manufacturing companies is considered quite satisfactory, introducing the new guidelines to apply the full concept of project management is necessary to develop interest and motivation for the companies to be applied in all areas within the organization. acknowledgement the authors would like express their sincere gratitude to all respondents for their time and effort. the authors also would like to appreciate very much the support from department of manufacturing and materials engineering to facilitate data collection and proving the analytical support. references 1. sme annual report 2014 /2015, retrieved from www.smecorp.gov.my/index.php/en/resources/2015-1221-11-07-06/sme-annualreport-2014/2-annual-report. 157. 2. sme annual report 2015 /2016, retrieved from www.smecorp.gov.my/index.php/en/resources/2015-1221-11-07-06/sme-annualreport/book/69-annual-report-2015-16/2-annual-report. 186. 3. economic census (2011) profile of small & medium enterprise. retrieved from https://www.statistics.gov.my/dosm/uploads/files/bancibe/penerbitan_profil_pks_20 11.pdf. 4. morris, p. w. g. (2011). a brief history of project management. 5. turner, r., ledwith, a., & kelly, j. (2010). project management in small to medium-sized enterprises: matching processes to the nature of the firm. international journal of project management, 28(8), 744-755. 6. bahnaier, w. w. (2001). scheduling guide for program managers. diane publishing. barron, m., & barron, a. (2009). history of project management. connexions, september, 7. atkinson, r. (1999). project management: cost, time and quality, two best guesses and a phenomenon, its time to accept other success criteria. international journal of project management, 17(6), 337 – 342. 8. kerzner h. (1998). in search of excellence in project management. john wiley and sons. 9. ihesiene, u. c. (2014). a survey-based study of project management problems in small and medium scale enterprises (smes) in nigeria. european scientific journal, 10(25). 10. sarah marley (2014). the importance and effect of sample size. retrieved october 28, 2016, from https://select-statistics.co.uk/blog/importance-effect-sample-size/ http://www.smecorp.gov.my/index.php/en/resources/2015-12-21-11-07-06/sme-annual-report-2014/2-annual-report http://www.smecorp.gov.my/index.php/en/resources/2015-12-21-11-07-06/sme-annual-report-2014/2-annual-report http://www.smecorp.gov.my/index.php/en/resources/2015-12-21-11-07-06/sme-annual-report-2014/2-annual-report http://www.smecorp.gov.my/index.php/en/resources/2015-12-21-11-07-06/sme-annual-report/book/69-annual-report-2015-16/2-annual-report http://www.smecorp.gov.my/index.php/en/resources/2015-12-21-11-07-06/sme-annual-report/book/69-annual-report-2015-16/2-annual-report http://www.smecorp.gov.my/index.php/en/resources/2015-12-21-11-07-06/sme-annual-report/book/69-annual-report-2015-16/2-annual-report https://www.statistics.gov.my/dosm/uploads/files/bancibe/penerbitan_profil_pks_2011.pdf https://www.statistics.gov.my/dosm/uploads/files/bancibe/penerbitan_profil_pks_2011.pdf https://www.statistics.gov.my/dosm/uploads/files/bancibe/penerbitan_profil_pks_2011.pdf https://select-statistics.co.uk/blog/importance-effect-sample-size/ https://select-statistics.co.uk/blog/importance-effect-sample-size/ abstract table 4: reliability test on implementation of project management (section a) table 5: reliability test on implementation of project management (section b) international journal of engineering materials and manufacture (2021) 6(4) 284-298 https://doi.org/10.26776/ijemm.06.04.2021.04 jain, s. 1 , hyder, j. 2 , corliss, m. 2 and hung, w. 1 1 texas a&m university ms 3367 college station, texas, 77843, usa 2 knust-godwin llc, katy, texas 77494, usa e-mail: hung@tamu.edu reference: jain et al. (2021). electrochemical polishing of extruded and laser powder-bed-fused inconel 718. international journal of engineering materials and manufacture, 6(4), 284-298. electrochemical polishing of extruded and laser powder-bed-fused inconel 718 srishti jain, james hyder, mike corliss and wayne hung received: 13 february 2021 accepted: 22 march 2021 published: 01 october 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract electro-chemical polishing (ecp) was utilized to produce sub-micron surface finish on inconel 718 parts manufactured by laser powder-bed-fusion (l-pbf) and extrusion methods. the l-pbf parts had very rough surfaces due to semiwelded powder particles, surface defects, and difference layer steps that were generally not found on surfaces of extruded and machined components. this study compared the results of electro-polishing of these differently manufactured parts under the same conditions. titanium electrode was used with an acid-based electrolyte to polish both the specimens at different combinations of pulsed current density, duty cycle, and polishing time. digital 3d optical profiler was used to assess the surface finish, while optical and scanning electron microscopy was utilized to observe the microstructure of polished specimens. at optimal condition, the ecp successfully reduced the surface of l-pbf part from 17 µm to 0.25 µm; further polishing did not improve the surface finish due to different removal rates of micro-leveled pores, cracks, nonconductive phases, and carbide particles in 3d-printed inconel 718. the microstructure of extruded materials was uniform and free of processing defects, therefore can be polished consistently to 0.20 µm. over-polishing of extruded material could improve its surface finish, but not for the l-pbf material due to defects and the surrounding micro-strain. keywords: laser powder bed fusion, selective laser melting, electro-chemical polishing, surface roughness, extrusion, inconel 718, microstructure. 1 introduction metal additive manufacturing (mam) have become more popular in industry and academia since it can produce complex shaped metal components using one platform without having to integrate many different manufacturing techniques. the inconel 718 (in 718) superalloy possesses properties suitable for extreme environments in nuclear, chemical, oil/gas and aerospace applications. owing to its superior properties such as corrosion and creep resistance at elevated temperatures, the in 718 are highly demanded material for complex engineering profiles, robust and with high dimensional precision [1]. consolidation of inconel powder by am techniques has helped in producing in 718 parts while preserving material properties and allowing more design freedom. a variety of powder-bed am methods such as electron beam melting, direct energy depositing, selective laser sintering, binder jetting, and selective laser melting (slm) –or laser powder bed fusion (l-pbf) -are suitable for this purpose. however, parts produced through these methods are far from finished products due to their rough surfaces and dimensional inaccuracy. the rough surface is a result of shrinkage, layer wise building sequence or “staircase effect,” partially welded powder particles, cracks and slags. optimizing the am parameters and scanning strategies can only improve the surface finish to some extent [2,3], but to achieve the required level of submicron surface finish would necessitate the need of post processing of mam parts. for examples, dimensioning accuracy and good surface finish are required for applications such as aircraft engines, high-pressure turbines, or medical implants. these post processing operations could include machining, buffing, grinding, lapping, chemical mechanical planarizing (cmp), magnetic particle polishing and electrochemical polishing (ecp). finish machining of in 718 can reduce the as-printed surface finish from 17-20 µm to about 1.5 µm jain et al. (2021): international journal of engineering materials and manufacture, 6(4), 284-298 285 sa but at the expense of tool wear [4]. another preliminary study showed that buffing can produce a submicron surface finish but corners and specimen details could be indiscriminately polished. similar issues are expected for the abrasive flow polishing. although grinding, lapping, cmp, or magnetic particle polishing can be applied to polish additively printed specimens, these processes are more suitable to large components with restricted or very specific and simple geometries. the ecp process is a promising technique due to its non-contact nature, non-consumable electrode, independence of workpiece strength and hardness, no surface damage, and no process-induced residual stress. this process can be applied locally to polish only a critical surface, or to improve the larger surface of an engineering component with customized electrodes. the ecp also eliminates additional deburring process compared to using a contact-method for surface enhancement. post processing techniques including ecp have been applied to inconel alloys that were fabricated by either extruding, rolling, forging, or casting but very limited published data were found for polishing of 3d-printed in 718. this research aims to: i. achieve submicron surface finish of in 718 by ecp, ii. compare the polishing results on in 718 samples fabricated by l-pbf or extrusion, and iii. correlate polishing results with the microstructural study on ecp specimens. 2 literature review inconel comes from a family of austenitic-nickel-chromium based superalloys. the high strength and corrosion resistance properties make them well suited for adverse environments subjected to pressure and heat. inconel 718 (50-55 wt% ni, 17-21 cr, 13.25-24.6% fe, 4.75-5.50 nb, 2.8-3.3 mo, 0.65-1.15 ti, 0.2-0.8 al, <1.0 co, <0.08 c) is a superalloy that can retain its mechanical properties at high temperature up to 650°c [5]. this precipitation hardenable material exhibits good creep and rupture strengths along with welding characteristics. it was reported that in an mam process, repeated melting and fast cooling of the molten powders would form the dendrite solid solution γ phase, nbc niobium carbide, and the laves phase [6-10]: liquid inconel 718 → γ + nbc + laves (1) further heating of adjacent regions in l-pbf led to aging of the γ phase to form δ precipitates, and other γ’ and γ” precipitates. compositions of the δ precipitate was reported as ni3nb, that for the laves was (ni, cr, fe) (nb, mo, ti), and those for the γ’ and γ” precipitates were ni3(al, ti) and ni3nb respectively [10,11]. the δ precipitates, typically needle shape of few-micron long, were formed primarily at grain boundaries and contained at least 6-8% nb. both the γ’ and γ” precipitates, in nanometre scale, can be seen with transmission electron microscopy (tem) and maybe visible with very high-resolution scanning electron microscopy (sem). the laves phases were the largest phase of all; contained at least 10%nb, although a very large percentage of 35%nb in laves was also reported [7]. the laves phases can be dissolved by homogenizing at 1100°c/hr before solution heat treating and aging to obtain the optimal mechanical properties of in 718 [10]. additional metal carbides were reported as m23c6 containing cr, mo, and nb. both the nbc and m23c6 carbides were stable; a nbc phase, with significant nb content, depleted nb atoms around it and prevented formation of the finer γ” precipitates [11]. both volume and surface defects on mam specimens had been reported in literature. even though l-pbf in 718 offered some advantages compared to subtractive methods, there were issues with pores, partially melted powder, shrinkage cavities, slags, and incomplete bonding between layers. other studies [12,13] found spherical gas-filled pores trapped in the molten metal, balling phenomenon, partially melted powder particles that adhered on the top surface or at the boundary between deposited layers. these defects, caused by improper scanning speed and linear laser density, would act as detrimental stress raisers and finally led to early failure under fatigue conditions. many researchers had made efforts to improve the surface quality of l-pbf manufactured parts by studying the effects of processing parameters on surface morphologies, microstructures, and material properties of in 718. they found that surface integrity varied significantly at different laser energies and scanning speeds. by reducing the scanning speed from 300 to 100 mm/s, the positive results with nearly dense materials and relatively smooth surfaces were obtained [3,14]. in another research, finish-turning of in 718 with three different types of coated carbide tools in minimum quantity lubrication (mql) were performed. three types of coating selected in this study were the chemical vapor deposited (cvd) three-layers coating of ticn/al2o3/tin, a physical vapor deposited (pvd) superlattice coating of tin/aln and a pvd monolayer coating of tialn. cutting speeds were selected at 1.0 and 1.5 m/s. amongst the three coatings there was always a trade-off between surface finish and the tool life. machining with tin/aln coated tools in mql provided the best surface finish amongst the three coatings but at the expenses of shorter tool life. the longest tool life was attained by using the ticn/al2o3/tin coated tools in wet-cutting but the surface finish was compromised [30]. few researchers had applied ecp as the post-processing method to improve surface finish of in 718. combinations of perchloric, sulfuric, phosphoric, and acetic acids were suggested for ecp of in 718 [15]. phosphoric acid ensured a slow and uniform dissolution at the appropriate working conditions without significant adverse effects of corrosion or erosion, whereas sulfuric acid increased current density by causing the initial dissolution of the surface of workpiece. neda et al. [31], proposed an innovative finishing technique combining chemical and abrasive flow polishing of electrochemical polishing of extruded and additively manufactured inconel 718 286 interior surfaces of tubular in 625 components for the aerospace industry. the results showed that by combining the chemical and abrasive flow polishing technique on the interiors surfaces, the surface roughness can be significantly improved from 17 µm to 2.3µm ra; and the semi-welded particles that adhered on the surface can be completely removed. another study using ecp process to improve the surface finish of l-pbf in 718 parts was performed. an anodic cylindrical part was position at centre of a cathodic cylindrical tank. the large 30-mm electrode gap was filled with stirred electrolyte (20% sulfuric acid and methanol). current density of 50 a/dm 2 was applied between electrodes for different intervals of 1-5 minutes. at optimal condition, the resulted surface roughness ra was reduced to 3.66 µm from 6.05 µm. nano hardness of the polished samples, however, was reduced due to dissolving of the strengthening precipitates during the etching/polishing process. the needle shaped δ-phase and carbide particles appeared in the grain boundaries after long polishing time of 5 minutes [17]. surface finish of electrochemically drilled holes in conventionally manufactured wrought in 718 was performed. the ø0.5 mm brass electrodes were used as the drilling tool. the authors varied the input variables (pulsed voltage, duty cycle, electrolyte concentration and types --nacl or nano3-and the electrode feed rate). surface finish inside an ø0.5 mm hole was measured with a non-contact probe. the study concluded that nacl should be used for high drilling rate, while nano3 should be used for fine surface finish. a surface finish range of 0.535-3.930 µm ra was reported [18]. the performance of ecp can also be enhanced by switching the applied direct current to pulsed current. the additional off-time in pulsed current allowed effective flushing of debris/ions and refreshing of new electrolyte to the anodic surface [19-23]. when combining with ultrasonic vibration, the cavitation effect led to effective flushing and improved surface finish of ecp parts [24]. electrochemical grinding was used as finishing process for in 718 [25]. high material removal rate could be obtained with brazed diamond wheel, high applied-voltage, feed rate and electrolyte temperature; however, the resulted surface finish was not included in the report. 3 experiments 3.1 sample preparation both the l-pbf and extruded in 718 samples were prepared for ecp process. • the l-pbf parts were laser printed to 15 x 20 x 5mm on a renishaw am250 system. the 15 x 20mm base surface was parallel to the scanning x-y plane while the 5mm thickness was along the building z-direction. the average diameter of in 718 powder was 50µm and the powder was fused together using a yag laser beam at 160w power with a hatching distance of 110µm in argon gas. the stripe scanning strategy was adopted for the manufacturing of these samples. • the extruded samples were cut from an annealed ø19.1mm bar using wire-type electrical discharged machining (wire edm) method. a sample was cut to the same size of 15 x 20 x 5mm with the 15 x 20 mm surface is perpendicular to the bar axial direction. due to inconsistent surface profiles of mam and extruded surfaces, each specimen surface was normalized by handgrinding with a fresh 180-grit sic paper in a uniform direction to achieve an even surface. the sanded samples were then cleaned ultrasonically for 5 minutes in isopropyl alcohol to remove any debris and contaminants before ecp. 3.2 experimental set-up the anodic workpiece (in 718) was then clamped in the esma ecp system with a sanded direction in vertical direction. a cathodic titanium electrode with hemispherical end was used to minimize orientation error. the titanium electrode was mounted on a teflon holder that electrically insulated it from the motor. a multimeter was used to detect the electrical contact of both clean and dried electrode/workpiece surfaces, after which the velmex bislide system with 5µm repeatability was used to move the electrode and position it 0.5mm away from the specimen surface (fig. 1). a minimum of at least 4 trials were performed to verify the repeatability of electrical contact of the two electrodes and the interelectrode gap. a full factorial experiment was conducted based on three ecp input parameters (current density, polishing time, and duty cycle) at three different levels. the numerical values of these levels were selected after completion of preliminary experiments. the duty cycles of 25, 50, and 75% were chosen to study the effect of off-time from current pulses. a longer off-time (low duty cycle) would allow more flushing time but reducing the polishing rate. thus, a total of 27 experiments with two replicates were conducted to polish the l-pbf and extruded in 718 samples. a commercial and proprietary mixture of phosphoric and sulphuric acids was used. it consisted of a high percentage of phosphoric acid about 40-80% and sulphuric acid with 5-35% by weight. although this electrolyte can be used up to 65ᵒc (150ᵒf), it was used at room temperature in this study, since a high testing temperature would lead to aggressive chemical reactions suitable for machining but not for polishing. a fresh electrolyte was used for every set of 27 experiments. table 1 lists all variables, constants, and equipment in this study while table 2 tabulates different samples and respective ecp parameters. after polishing, a workpiece with remnant electrolyte was first rinsed in running tap water, and then dried completely with compressed air. a schematic of polished specimen is shown in figure 2. after ecp’ed, rinsed, and dried, the surface of a specimen was studied in the rectangular zone of 3x3 mm 2 . both the olympus stm6 optical microscope and vegas scanning electron microscope (sem) were used for microstructure study. an energy dispersive spectroscopy (eds) system, jain et al. (2021): international journal of engineering materials and manufacture, 6(4), 284-298 287 integrated with the vegas sem, was utilized to identify different phases in the microstructure of polished samples. surface roughness was measured with the alicona g4 if profiler within a square zone of 1x1mm for area surface finish sa and a 1mm length for line surface finish ra. surface evaluation was repeated four times at each location in both directions, parallel and perpendicular to the sanding marks. figure 2 defines different zones and the coordinate system. the y-axis was chosen to be parallel to sanding marks while the x-axis was perpendicular to the sanding direction. figure 1: schematic of experimental set-up table 1: experiment design variables values current density (a/mm 2 ) 0.2, 0.7, 1.2 duty cycle (%) 25, 50, 75 polishing time (s) 90, 180, 270 constants and dependent variables on-time (ms) 10, 20, 30 peak current (a) 1.0, 3.5, 6.0 interelectrode gap (mm) 0.5 electrolyte commercial acid-based, ep 2000 electrode ø2.5mm commercially pure titanium equipment model ecp cell esma model e1085-1s power supply dynatronix (crs-lfp(r)) multimeter tenma 72-6202 3d optical profiler alicona if positioner velmex bislide mn10 optical microscope olympus stm6 scanning electron microscope vega3 tescan pulsed power supply multimeter granite table + _ electrolyte ti electrode specimen 2-axis positioner insulator electrochemical polishing of extruded and additively manufactured inconel 718 288 table 2: factorial design sample number current (a) current density (a/mm 2 ) time (sec) duty cycle (%) 1 1 0.2 90 25 2 3.5 0.7 3 6 1.2 4 1 0.2 180 5 3.5 0.7 6 6 1.2 7 1 0.2 270 8 3.5 0.7 9 6 1.2 10 1 0.2 90 50 11 3.5 0.7 12 6 1.2 13 1 0.2 180 14 3.5 0.7 15 6 1.2 16 1 0.2 270 17 3.5 0.7 18 6 1.2 19 1 0.2 90 75 20 3.5 0.7 21 6 1.2 22 1 0.2 180 23 3.5 0.7 24 6 1.2 25 1 0.2 270 26 3.5 0.7 27 6 1.2 figure 2: schematic of polished zone and surrounding area jain et al. (2021): international journal of engineering materials and manufacture, 6(4), 284-298 289 3 results and discussions 3.1 surface finish the average surface finish of as-printed samples on xy-plane was measured to be 17-20 µm sa, the measurement was even rougher in the building z-direction due to layer mismatching and partially welded powder particle on the surface (fig. 4a). alternate layers with different microstructures are shown on x-y plane (fig. 4b), additional defects like shrinkage cavities, microcracks, slags were also observed; therefore, each sample was normalized by sanding for a uniform surface before polishing (fig. 5a). ecp conditions: current density (a/mm 2 ), polishing time (s), and duty cycle (%) respectively. refers to figure 5 shows the success of ecp when all the sanding marks were completely removed. the repeatability of ecp system and the uniformity of ecp polished surfaces were confirmed: • repeatability. a set of 15 extruded samples were electropolished in a random order to check the repeatability of the ecp system. the average error was within ± 7% as shown in table 3. • isotropy. table 4 and fig. 6 show the uniformity of ecp polishing. the line surface roughness ra values, measured in both perpendicular and parallel to grinding marks, were practically the same since the data were statistically indifference. this implies (i) a grinding mark was polished completely as confirmed with microscopic observation, and (ii) the electrical field around the titanium electrode was uniform and symmetric so that ions are uniformly removed around the electrode; however, the distance from electrode tip to a specific location affected the material removal rate (fig. 7). the material was polished more at location just below the electrode, and the effect diminished away from the electrode. a larger electrode or control motion of electrode would solve this issue. table 5 shows the difference in surface finish of l-pbf and extruded in 718 parts. submicron surface finish was achieved in the polished zones; the process was repeated twice for each condition and the measured results –the average of four random measurements– were repeated within ± 8%. as expected, the duty cycle of 75% yielded better results for both the mam and extruded samples. at this optimal condition, the longer on-time allowed more material to be removed yet left sufficient off-time for flushing debris and replenishing of fresh electrolyte to the polished surface. the vertical position of polished anode also facilitated the removal of debris during polishing; an anodic workpiece in horizontal position would accumulate fine debris, especially the nonconductive contaminants, at the polishing zone and interfere with ion transport mechanism. figures 8a-c below compare the surface finish between the l-pbf and extruded specimens at different polishing durations at each duty cycle of 25%, 50% and 75% respectively. • polishing of l-pbf samples. at every duty cycle, 90 seconds of polishing duration produced the best surface finish, but the roughness increased after longer polishing time from 90 to 270 seconds. the issues were with microstructural defects such as pores and nonconductive intermetallic phases like carbide or laves. the ecp process would remove the conductive matrix according to faraday law, but would not affect the nonconductive “contaminants” in the materials. during the ecp process, ions from the conductive matrix were removed and exposed more nonconductive defects on the polished surface, thus degrading the surface texture. the best surface finish for l-pbf samples was 0.28 µm after ecp at 0.7 a/mm 2 current density, 90s polishing time, and 75% duty cycle. • polishing of extruded samples. the microstructure of extruded samples was more uniform. polishing of extruded samples after 270s gives the best surface finish at every duty cycle. the reaction equation (1) predicts significant microstructural changes in mam. such metallurgical reaction happened regardless of different am processes that utilize either laser, electron beam, or plasma arc to deposit successive layers of metal beads. the fast heating and rapid cooling of each layer formed the brittle intermetallic compound laves phases with combination of (ni, cr, fe) (nb, mo, ti). figures 4 b-c shows alternative layers of in 718 after melted, solidified, and reheated again when a laser scanned and melted adjacent beads. contamination of in 718 powder after repeated pbf cycles also contribute to irregularities in the microstructure of samples fabricated by l-pbf process. in contrast, the hot extruded materials are commonly performed at temperature approximately half of the absolute melting temperature of those metals. the metallurgical reaction (1) does not apply to in 718 at the relatively low temperature during hot extrusion, therefore, we would expect a more uniform microstructure with no porosity in extruded samples. the polishing results by ecp can be further explained when examining the microstructure of the polished samples. electrochemical polishing of extruded and additively manufactured inconel 718 290 figure 4: surface profile of l-pbf inconel 718: (a) partially welded powder particles on xz-plane, (b) secondary electron image of x-y plane, and (c) back-scattered electron image on x-y plane. the arrow in (b) indicates the laser scanning direction. figure 5: optical image of (a) sanded l-pbf inconel 718, and (b) polished zone after 0.70 a/mm 2 , 90 s, 50% duty cycle. the arrows point to different pores on the polished surface. figure 6: surface finish of measuring in direction relative to grinding marks. figure 7: effect of distance from electrode on polishing results showing (a) polished zone directly below the electrode, (b) transitional zone, and (c) unpolished zone. l-pbf specimen after 0.2 a/mm 2 , 180s, 50% duty cycle. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.2-90-25 1.2-90-25 0.2-270-25 1.2-270-25 0.2-90-75 1.2-90-75 0.2-270-75 1.2-270-75l in e r o u g h n e s s , r a ( µ m ) ecp conditions ra_parallel ra_perpendicular 100 µm a b c 100 µm a 50 µm 20 µm b 2 mm a b c b jain et al. (2021): international journal of engineering materials and manufacture, 6(4), 284-298 291 (a) (b) (c) figure 8: comparison of roughness at polished zone of am and wrought specimens. ecp at 25hz at (a) 25%, (b) 50%, and (c) 75% duty cycle. average of 4 data points. l-pbf l-pbf l-pbf extruded extruded extruded electrochemical polishing of extruded and additively manufactured inconel 718 292 table 3: repeatability of ecp results sample number current density (a/mm 2 ) time (sec) duty cycle (%) original ra (µm) repeated ra (µm) error (%) 1 0.20 180 25 0.77 0.75 -3% 2 180 75 0.58 0.55 -5% 3 270 25 0.73 0.69 -5% 4 270 75 0.55 0.53 -4% 5 0.70 90 75 0.54 0.58 7% 6 180 75 0.45 0.42 -7% 7 270 75 0.21 0.2 -5% 8 90 25 0.67 0.69 3% 9 180 25 0.63 0.65 3% 10 270 25 0.58 0.566 -2% 11 1.20 90 25 0.67 0.695 4% 12 90 75 0.43 0.46 7% 13 180 25 0.5 0.53 6% 14 180 75 0.45 0.465 3% 15 270 25 0.6 0.58 -3% table 4: data for parallel and perpendicular roughness comparison polishing condition * parallel σ for ra(1-4) perpendicular σ for ra(5-8) ra1 (µm) ra2 (µm) ra3 (µm) ra4 (µm) ra5 (µm) ra6 (µm) ra7 (µm) ra8 (µm) 0.2-90-25 0.425 0.64 0.4 0.42 0.11 0.57 0.53 0.61 0.55 0.06 1.2-90-25 0.61 0.58 0.48 0.47 0.09 0.62 0.58 0.63 0.59 0.11 0.2-270-25 0.57 0.65 0.69 0.49 0.09 0.67 0.63 0.57 0.53 0.06 1.2-270-25 1.18 0.66 0.78 0.99 0.24 0.97 0.93 1.05 0.61 0.22 0.2-90-75 0.73 0.67 0.49 0.57 0.11 0.74 0.7 0.82 0.71 0.08 1.2-90-75 0.59 0.53 0.66 0.69 0.07 0.65 0.59 0.51 0.75 0.10 0.2-270-75 0.77 0.5 0.71 0.63 0.12 0.69 0.65 0.45 0.75 0.13 1.2-270-75 0.94 0.84 0.78 0.81 0.08 0.93 0.89 0.94 0.85 0.07 * the three numbers refer to current density (a/mm 2 ), polishing time (s), and duty cycle (%) respectively. jain et al. (2021): international journal of engineering materials and manufacture, 6(4), 284-298 293 table 5: ecp results of l-pbf and extruded samples sample number current density (a/mm 2 ) time (sec) duty cycle (%) surface finish, ra (µm) l-pbf extruded 1 0.2 180 25 0.77 0.51 2 180 75 0.58 0.67 3 270 25 0.73 0.49 4 270 75 0.55 0.35 5 0.7 90 75 0.54 0.75 6 180 75 0.45 0.30 7 270 75 0.21 0.24 8 90 25 0.67 0.45 9 180 25 0.63 0.82 10 270 25 0.58 0.60 11 1.2 90 25 0.67 0.49 12 90 75 0.43 0.31 13 180 25 0.5 1.11 14 180 75 0.45 0.32 15 270 25 0.6 0.5 3.2 microstructures both samples –extruded and additively manufactured-were polished at the same ecp parameters for comparison. the extruded and annealed specimens had a uniform microstructure consisted of the matrix and  precipitates along the grain boundaries and did not exhibit any obvious material defects (fig. 9a). aghajani et al. [11] reported that ceramic carbides can be formed in the microstructure of in 718. the niobium carbides (nbc) combined and used niobium atoms from the surrounding matrix. defects in in 718 affected the polishing results due to: – inclusions. both metallic carbide m23c6, and niobium carbide nbc are seen in the microstructure. the metallic carbides were embedded into the surrounding matrix (fig. 10a), but the nbc inclusions contained niobium atoms, therefore, the etching rate of niobium depleted zone and the matrix of in 718 should be different. scanning electron microscopic observation shows nbc particles surrounded by dark zones that implied materials with different chemical compositions, or the different topography after electro-chemical etching (fig. 10b). in addition to the carbide phases, the segregated niobium also was shared by precipitates such as δ (incoherent ni3nb), γ’ (ni3al), γ’’ (ni3nb), and laves phases ((ni,cr,fe)2(nb,mo,ti)). the precipitates were dissolved in the etching solution due to their small sizes, but the larger and nonconductive carbides and laves particles had much lower etching rates as compared to that of the matrix. – voids. there was no porosity in extruded samples, but voids and smaller spherical pores were seen in the l-pbf samples. the geometry of voids/pores on polished surface degraded the surface roughness of mam samples. common pores and voids may have tiny cracks in grain boundaries (fig. 11b); materials at such irregular feature with sharper edges were removed at a faster rate due to higher current density in ecp. a crack within a pore, or between 3d-printed layers was enlarged after ecp as shown in figs. 11a and 12a. – strain-induced etching. microlevel strains were induced in the matrix by precipitates, inclusions, temperature difference, or grinding/machining actions. although in minute scales, such plastic train was significant enough to (i) lower the activation energy for electrochemical reaction, (ii) accelerate the local material removal rate, and (iii) degrade the overall surface quality of ecp samples. fig. 12b shows craters in the material matrix with inclusions (labelled #2) at the centre; but no surrounding craters with other inclusions (labelled #1). perhaps these inclusions were different in compositions and had different thermal expansion coefficients with that from the matrix, thus imparted different micro-strain levels at the corresponding circumferences. figures 13a-c show the evolution of a l-pbf surface. the vertical grinding marks on as-printed samples (fig. 13a) were gradually removed (fig. 13b) until the final step (fig. 13c). however, the plastic strain underneath a grinding mark was still present in the optical image and shown as residual grinding mark in electrochemical polishing of extruded and additively manufactured inconel 718 294 fig. 13c. the residual marks, that were not visible in scanning electron microscopy, indicated nonuniform electrochemical reaction rates. perhaps such residual marks can be quantitatively detected by atomic force microscopy. grain boundaries (fig. 13c) and scanning laser paths (fig. 13b) were also visible due to preferred and different etching rates due to high strain energy at grain boundaries and boundaries of laser melted seams. – electrical conductivity. the ecp process required control movement of ions and electrons to effectively remove and polish an anodic workpiece in atomic scale. nonconductive phases such as precipitates, voids/pores, cracks, inclusions, ceramic particles, slags/contaminants were not affected by ecp. even conductive phases with different electrical conductivities in an inhomogeneous matrix would have different etching rates and affect the surface finish of polished samples. submicron surface finish on both extruded and l-pbf materials was achieved in this study; however, the microstructure of each material contributed to final surface finish. referring to fig. 8 that compares surface finish of two materials, the l-pbf samples had the lowest surface finish of 0.25µm ra at 0.7 a/mm 2 , 75% duty cycle after 90s. longer polishing time and higher current density worsened the surface finish since more defects would be exposed after removing the matrix materials. in contrast, due to the more homogeneous microstructure and less defects, the surface of extruded samples can be further improved after longer time or by applying a higher current density. post processing techniques can be applied to the l-pbf material to improve its microstructure before polishing. pores can be reduced by modifying the scanning strategies [27], but it might be more cost effective when hot-isostatic pressing the bulk number of l-pbf parts. since laves phases and pores can be eliminated by homogenizing and hotisostatic pressing [6,8,10,28,29], these post processes could be applied before ecp to achieve a better surface finish. figure 9: (a) sem image of extruded sample, viewing along the extruding direction. the needle shape δ phases are visible along grain boundaries. ecp at 0.7 a/mm 2 , 270s, 75% duty cycle; and (b) optical image of extruded sample. ecp at 0.7 a/mm 2 , 270s, 50% duty cycle. figure 10: inclusions in extruded sample (a) metallic carbide, and (b) niobium carbide with depleted surrounding. ecp at 0.7 a/mm 2 , 270 s, 75% duty cycle. 20 µm 50 µm inclusion 50 µm 50 µm nbc a b m23c6 jain et al. (2021): international journal of engineering materials and manufacture, 6(4), 284-298 295 figure 11: enhanced defects of l-pbf samples; (a) enlarged crack within a pore after ecp at 0.7 a/mm 2 , 180 s and 75% duty cycle, and (b) typical crack within a pore before ecp. figure 12: enhanced defects after ecp of l-pbf samples; (a) crack after ecp at 1.2 a/mm 2 , 270 s and 50% duty cycle, (b) differential etching rates around different inclusions. ecp at 0.7 a/mm 2 , 180 s and 75% duty cycle. figure 13: evolution of surface polishing on l-pbf sample (a) ground surface, (b) partially polished surface, and (c) 0.45µm ra polished surface. ecp at 1.2 a/mm 2 , 180s, 75% duty cycle. 3.3 regression models regression models were derived for both extruded and l-pbf parts based on the experimental data for line roughness ra and area roughness sa. these models were built using the extreme values of the parameters (table 1) and then tested with the intermediate values to predict the accuracy of each model. • regression equations for l-pbf in 718: 𝑅𝑎𝐿𝑃𝐵𝐹 = 0.602 − 0.191 𝐽 − 0.00021 𝑡 + 0.0007 𝑑𝑐 − 0.0493 𝑑 + 0.0013(𝐽 × 𝑡) + 0.0014(𝐽 × 𝑑𝑐) +0.248 (𝐽 × 𝑑) (2) 𝑆𝑎𝐿𝑃𝐵𝐹 = 0.490 + 0.370 𝐽 + 0.00383 𝑡 + 0.0040 𝑑𝑐 − 0.0796 𝑑 − 0.00005(𝑡 × 𝑑𝑐 ) − 0.000329 (𝑡 × 𝑑) +0.00218(𝑑𝑐 × 𝑑) (3) a 5 µm 20 µm 10 µm b a 5 µm b 1 2 50 µm 20 µm 50 µm pore a b c residual grinding mark grain boundary electrochemical polishing of extruded and additively manufactured inconel 718 296 • regression equations for extruded in 718: 𝑅𝑎𝑒𝑥𝑡𝑟𝑢𝑑𝑒 = 1.06 − 0.193 𝐽 − 0.000635 𝑡 − 0.0041 𝑑𝑐 − 0.19 𝑑 + 0.075 (𝐽 × 𝑑) + 0.00273(𝑑𝑐 × 𝑑) (4) 𝑆𝑎𝑒𝑥𝑡𝑟𝑢𝑑𝑒 = 0.975 − 0.373 𝐽 + 0.00093 𝑡 + 0.00577 𝑑𝑐 − 0.0092 𝑑 + 0.0044 (𝐽 × 𝑑𝑐 ) + 0.1063 (𝐽 × 𝑑) −0.000056 (𝑡 × 𝑑𝑐) (5) where, ra : average line roughness (µm) sa : average area roughness (µm) j : current density (a/mm 2 ) t : polishing time (s) dc : duty cycle (%) d : distance from the polished zone centre (mm) table 6: fitness values of regression models model ra for l-pbf sa for l-pbf ra for extruded sa for extruded r 2 fitness value (%) 79 86 84 81 ─ line roughness: equations (2) and (4) both indicated the higher impact of current density j over polishing time t and duty cycle dc. a higher current density would polish surface more and reduce its line roughness as expected. ─ surface roughness: equations (3) and (5) also indicated current density as the most relevant parameter. when polishing the l-pbf samples, the positive signs for current density, polishing time, and duty cycle were due to accelerated etching rate of electrochemical reaction on (i) strained regions that surrounding defects such as nonconductive phases, pores and cracks, and (ii) the nb depleted zone surrounding an nbc phase. strain energy at a high dislocation density zone would lower the activation energy for chemical reaction to happen, therefore increasing the local etching rate. a high current density and longer time removed more matrix materials around the nonconductive phases, enlarge existing pores/crack while exposing additional defects embedded below the original surface. on the contrary when polishing the extruded samples, the negative sign of current density suggested more effective polishing to smoothen a surface since (i) the small precipitates (e.g., , ’, ”) were dissolved with matrix ions, and (ii) lack of larger “inert” defects (e.g., void, laves phases…) compared to the l-pbf samples. ─ during the line roughness measurement, a 1-mm line was drawn in the matrix and did not cross any defect, therefore, its value represented the best possible scenario and was lower than the surface roughness values that represented everything within a 1-mm 2 area. 4 conclusions and recommendations surfaces of inconel 718 fabricated by laser-based powder bed fusion (l-pbf) and extrusion were successfully polished to submicron level by pulsed electrochemical polishing (ecp) process. this study found that: 1. the pulsed ecp produced a desirable isotropic polishing effect. submicron surface finish was achieved within the ranges of chosen process variables for line roughness (ra) and area roughness (sa). 2. the niobium carbides, metallic carbides were found on both materials. however, the l-pbf samples contained additional laves phases and voids that degraded the surface finish after electrochemically polished. 3. for the l-pbf samples, the best surface finish was 0.25 µm ra when polishing at 0.7 a/mm2, 75% duty cycle after 90s. further polishing did not improve the surface finish due to the exposure of inherent nonconductive phases and defects in the materials. for the extruded samples, the best surface finish was 0.21 µm ra when polishing at 0.7 a/mm 2 , 75% duty cycle after 270s. the surface finish of extruded parts improved with higher polishing duration due to absence of material impurities beneath the surface. 4. regression models for both area and line surface finish were presented. the r2 values of all models were in the range 79-86%. such fitness value could be further improved with 5-level parameter experimental studies. 5. homogenizing and hot-isostatic pressing should be done to eliminate large laves phases and pores prior to ecp for a uniform polished surface. both of these thermal processes also anneal and eliminate any residual strains in the material, therefore, minimize the strain-induced accelerate etching at local areas. jain et al. (2021): international journal of engineering materials and manufacture, 6(4), 284-298 297 acknowledgement the authors thank the kgsbo for providing the printed mam samples, esma for the ecp equipment, ep system for the electrolyte, and the teacher participants who helped with experiments and collected surface finish data. part of this work was funded by the national science foundation under grant # 1711917. references 1. schafrik re, ward dd, and groh jr. application of alloy 718 in ge aircraft engines: past, present and next five years. superalloys; 2001, 718(625): p. 1-11. 2. choi jp, shin gh, yang s, yang dy, lee js, brochu m, and yu jh. densification and microstructural investigation of inconel 718 parts fabricated by selective laser melting. powder technology; 2017, 310: p. 6066. 3. jia q and gu d. selective laser melting additive manufacturing of inconel 718 superalloy parts: densification, microstructure and properties. journal of alloys and compounds; 2014, 585: p. 713-721. 4. sadiq ma, hoang nm, valencia n, obeidat s, and hung wnp. experimental study of micromilling selective laser melted inconel 718 superalloy. j. procedia manufacturing; 2018, 26:p. 983-992. 5. special metals, www.specialmetals.com, accessed dec 2018. 6. knorovsky ga, cieslak mj, headley tj, romig ad, and hammetter wf. inconel 718: a solidification diagram. metallurgical transactions a; 1989: 20a, p. 2149-2158. 7. trosch t, strößner j, völkl r, glatzel u. microstructure and mechanical properties of selective laser melted inconel 718 compared to forging and casting. materials letters; 2016, 164: pp. 428-431. 164 8. radavich jf. electron metallography of alloy 718. superalloys 718, 625, 706 and various derivatives. the minerals, metals & materials society; 1997, p. 17-26. 9. wang z, guan k, gao m, li x, chen x, and zeng x. the microstructure and mechanical properties of depositedin718 by selective laser melting; journal of alloys and compounds; 2012, 513: p.518-523. 10. tucho wm, cuvillier p, sjolyst-kverneland a, and hansen v. microstructure and hardness studies of inconel 718 manufactured by selective laser melting before and after solution heat treatment. materials science and engineering a; 2017, 689: p. 220-232. 11. aghajani a, tewes jp, parsa ab, hoffmann t, kostka a, and kloewer j. identification of mo-rich m23c6 carbides in alloy 718. metallurgical and materials transactions a, 47(9); 2016. p. 4382-4392. 12. zhang b, li y, and bai q. defect formation mechanisms in selective laser melting: a review. chinese journal of mechanical engineering; 2017, 30(3): p. 515-527. doi:10.1007/s10033-017-0121-5. 13. wang x, gong x, and chou k. review on powder-bed laser additive manufacturing of inconel 718 parts. proceedings of the institution of mechanical engineers, part b: journal of engineering manufacture; 2017, 231(11): p. 1890-1903. 14. shi sq, gu d, xia m, cao s, and rong t. effects of laser processing parameters on thermal behavior and melting/solidification mechanism during selective laser melting of tic/inconel718 composites. optics & laser technology; 2016, 84, p. 9-22. 15. huang ca and chen yc. the effect of water content on the electropolishing behavior of inconel 718 alloy in perchloric–acetic acid mixtures. corrosion science; 2009, 51(9): p. 1901-1906. 16. yang l, o’neil c, and wu y. the use of electropolishing surface treatment on in718 parts fabricated by laser powder bed fusion process; 2017. 17. baicheng z, xiaohua l, jiaming b, junfeng gp, wang cs, muiling n, guojun q, and jun w. study of selective laser melting (slm) inconel 718 part surface improvement by electrochemical polishing. materials & design; 2017, 116: p. 531-537. 18. geethapriyan t, kalaichelvan k, and muthuramalingam t. multi performance optimization of electrochemical micro-machining process surface related parameters on machining inconel 718 using taguchi-grey relational analysis. la metallurgia italina; 2016, 4: p. 13-19. 19. feng z, granda e, and hung np. experimental investigation of vibration-assisted pulsed electrochemical machining. procedia manufacturing; 2016, vol. 5, p. 798–814. 20. feng z, orona-hinojos jm, perez-villanueva p, lomeli p, and hung wnp. flushing enhancement with vibration and pulsed current in electrochemical machining. journal of engineering materials and manufacture; 2017, 2(4), p. 67-85. 21. bhattacharyya b, malapati m, munda j, and sarkar a. influence of tool vibration on machining performance in electrochemical micro-machining of copper. international journal of machine tools and manufacture; 2007, 47(2): p. 335-342. 22. rajurkar kp, zhu d, mcgeough ja, kozak j, and de silva a. new developments in electro-chemical machining. cirp annals; 1999, 48(2): p. 567-579. 23. bilgi ds and jadhav pv. enhancement of surface finish of pulse electrochemically machined (pecm) surface using rotating electrode. compuer communincation and information system; 2010, 2:1, p. 49-54. 24. patel jb, feng z, villanueva pp, and hung wnp. quality enhancement with ultrasonic wave and pulsed current in electrochemical machining,” procedia manufacturing; 2017, 10: p. 662-673. electrochemical polishing of extruded and additively manufactured inconel 718 298 25. qu ns, zhang ql, fang xl, ye ek, and zhu d. experimental investigation on electrochemical grinding of inconel 718. procedia cirp 35; 2015, pp. 16-19. 26. bern rc and salva rp. additively manufactured inconel alloy 718. 7th international symposium on superalloy 718 and derivatives, the minerals, metals & materials society, 2010, pp.455-469. 27. mancisidor am, garciandia f, san sebastian m, álvarez p, díaz j, and unanue i. reduction of the residual porosity in parts manufactured by selective laser melting using skywriting and high focus offset strategies. physics procedia; 2016, 83: p. 864-873. 28. qi h, azer m, and ritter a. (2009). studies of standard heat treatment effects on microstructure and mechanical properties of laser net shape manufactured inconel 718. metallurgical and materials transactions a; 2009, 40(10): p. 2410-2422. 29. wang z, zhou d, deng q, chen g, and xie w. the microstructure and mechanical properties of inconel 718 fine grain ring forging. superalloy 718 and derivatives; 2010, p. 343-349. 30. kamata y, obikawa t, high speed mql finish turning of inconel 718 with different coated tools. materials processing technology: 2007, p: 281-286. 31. neda m, sylvain t, and vladimir b, surface finish control of additively manufactured inconel 625 components using combined chemical-abrasive flow polishing. materials processing technology: 2018, p: 728-738. international journal of engineering materials and manufacture (2020) 5(4) 98-115 https://doi.org/10.26776/ijemm.05.04.2020.01 a. patil 1 , j. raval 1 , t. bangma 2 , i. edinbarough 3 , b. tai 1 , d. stephenson 4 , s. obeidat 1 and w. hung 1 1 texas a&m university, college station, texas, usa 2 unist inc., grand rapids, michigan, usa 3 university of texas, rio grande valley, brownsville, texas, usa 4 ford motor company, livonia, michigan, usa e-mail: hung@tamu.edu reference: patil, a., raval, j., bangma, t., edinbarough, i., tai, b., stephenson, d., obeidat, s. and hung, w. (2020). characterization and performance of minimum quantity lubricants in through-tool drilling. international journal of engineering materials and manufacture, 5(4), 98-115. characterization and performance of minimum quantity lubricants in through-tool drilling amla patil, jay raval, tim bangma, immanuel edinbarough, bruce tai, david stephenson, suleiman obeidat and wayne nguyen hung received: 15 june 2020 accepted: 19 august 2020 published: 20 october 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 abstract this study characterized airborne microdroplet diameters and size distribution from two commercially available lubricants a and b for internal minimum quantity lubrication (mql). the effects of air pressure, oil channel size, physical properties of lubricants on the resultant microdroplets and through-tool mql drilling performance were studied. airborne microdroplet diameters were highly sensitive to the coolant channel sizes and air pressure. cluster method was used to divide microdroplets into smaller clusters for comparison. experimental data show that the average airborne microdroplet of lubricant b was larger than that of lubricant a at different air pressures and channel sizes. the contact angle of lubricant a was at least 10° less than that of lubricant b when depositing on glass or aluminium. high-speed imaging showed the tendency of more viscous lubricant b sticking to the drill tip, and higher pressure and longer time was required to atomize this viscous oil. built-up-edges were less significant when drilling a380 aluminium with lubricant a. due to high machinability of a380 aluminium, variation of hole diameter and hole cylindricity were minimal when drilling with different lubricants. insignificant improvement in hole quality was observed when drilling with excessive amount of mql lubricants or high concentration of lubricant c in flood coolant. keywords: minimum quantity lubrication, microdroplet, contact angle, through-tool lubrication, hole quality. 1 introduction minimum quantity lubrication (mql) is an effective and environmentally friendly substitute to traditional flood cooling method, especially in high-aspect-ratio operation --such as gun drilling-where cutting fluid delivery to the cutting edges is challenging. although the topic of mql has been investigated by many researchers, most of the published literature are for external mql and very limited research papers were dedicated to internal or throughtool mql. to understand how lubricant properties would affect performance of internal mql, and possible benefits of high lubricant concentration in an aerosol mixture, this research study aimed to: (i) characterize and compare through-tool mql microdroplets of two commercially available lubricants (ii) study microdroplet formation and flow exiting from through-tool coolant holes of a twist drill (iii) verify the internal mql effectiveness with drilling experiments. 2 literature review published literature has shown the advantages of utilizing mql in traditional machining except for grinding. this cost-effective technique reduces the cost for disposing large quantity of used and contaminated flood coolant /lubricant. it is a clean, near dry machining process as less than 2 percent of fluid adheres to the metal chips [1]. in mql, cutting fluid can be delivered to the cutting zone externally via one or multiple nozzles or internally via internal channels of a tool. these nozzles supply the aerosol, formed by the combination of a suitable oil and compressed air, to lubricate the cutting zone while removing heat by evaporation when micron-size oil microdroplets are propelled and adhered to the hot metal workpiece or tool surfaces. the more sophisticated internal mql system patil et al., (2020): international journal of engineering materials and manufacture, 5(4), 98-115 99 supplies air-oil mixture to the cutting zone in the form of micromist through the machine spindle, tool holder, and internal channels of a cutting tool itself. the single-channel mql system first mixes oil and air outside of a tool assembly, then pumps the mixture into the tool assembly. on the other hand, the dual-channel mql system brings air and oil separately within parallel coaxial tubes inside a rotary union; the oil-air mixture is only formed inside the tool assembly and then flowed into the cutting tool channels to reach the tool cutting edges. although published data for high aspect ratio drilling [2-9], or machining with external mql [10-13] have been published, only limited published information for internal mql was found. stephenson and agapiou [14] compared the performance of oneand two-channel mql systems. the more sophisticated two-channel system offered numerous advantages: independence of oil quantity with air flow and spindle rotation speed (up to 40,000 rpm), shorter reaction time (0.1-0.3 s), lower required air pressure (400kpa), and higher threshold for lubricant viscosity (100 mm 2 /s maximum). khan et al. [15] simulated through-tool mql to study the impact of input air pressure on microdroplet sizes, and then investigated the effect of mql on surface finish and tool wear when micromilling selective laser melted inconel 718. the authors also included the effect of nozzle surface roughness on airborne drop sizes. two 3d-printed abs nozzles were used to deliver the mql mixture: one as-printed nozzle (16.8 μm ra surface roughness) and other acetone-polished nozzle (3.2 μm ra surface roughness). the haas om2 cnc milling system was used for milling. coolube 2210 ep was used as a coolant in the simulated mql system. milling parameters were kept constant as 13.6 m/min speed, 1.8 μm/tooth chip load, and 20 μm depth of cut. the flow velocity of compressed air was measured with the kanomax climomaster 6501 anemometer. the authors found that at the respectively increasing air pressure of 275, 415, and 550 kpa then the mql drop sizes from the smooth nozzle were 11.42, 9.31, 7.60 μm while the rough nozzle broke down the mql drop size further to 9.20, 7.25 and 4.69 μm. higher air pressure of 550 kpa generated small airborne microdroplets of about 5 μm and improved surface finish of the workpiece to approximately 1 μm. kao et al. [16] studied the effect of coolant channel sizes and shapes on the mist flow in through-tool mql drilling. mist flow was analysed experimentally and analytically for circular and triangular coolant channels of four identical drills. experiments were conducted on two channels with circular cross-section of 1.6 and 1.0 mm diameters; other two channels had an equilateral triangle cross-section with side lengths of 2.15 and 1.35 mm. the air pressure and the oil flow rate were 5 bars and 45 ml/hr respectively. a high-speed camera was used to capture the mist flow at the drill tip and an anemometer was used to measure the airspeed of the resultant micromist. the authors observed that the air flow rate of the mist varied according to the coolant channel size and shape. the airspeed was higher when exiting a larger channel. thus, for a smaller circular channel, lubricant microdroplets were found to coalesce to form larger microdroplets. the circular channels produced higher airspeed than those of triangular channels; and the lubricant accumulated more near the drill centre point on drill with circular channels. raval et al. [17-18] characterized mql micromist distribution in through-tool coolant twist drills that were fabricated with a vat photo-polymerization system. three coolant channel shapes were included in their study: circular, triangular and the reversed triangular. a unist dual channel mql system with a rotary union and an atomizing chamber was used. images from a high speed camera and data from numerical analysis were combined and compared. frame rate was constant at 1000 fps with a resolution of 512×512 pixels. axial velocity component of the drill was considered negligible. unist coolube 2210 oil was used in the study; its flow rate was maintained at 40 ml/hr for all the experiments. circular coolant channels had 1.6 mm diameter and equilateral triangular channels had 2.15 mm side length, such that the cross-sectional area of the coolant channel was same in both the cases. the study concluded that the coolant channel geometry and helix angle affected the mist flow distribution. in case of 0˚ helix angle, high flow velocity region appeared at the centre of the channel. for 30˚ and 45˚ helix angle, circular channel showed high velocity region away from the chisel edge, because of the centrifugal forces generated from the fluid motion in the channel. also, high velocity regions showed low mist concentration and vice versa. flow of aerosol mixture in multiple through-tool channels was studied by hughey and stephenson [19]. by modelling a channel as electrical resistance – the ratio of channel length and channel area-the flow and response time for complete development of mql flow can be accurately estimated. the cutting fluid emissions produced in through-tool drilling of steel, aluminium and cast materials were investigated. pure synthetic esters with various viscosities were used as lubricants. at a fixed drilling feed rate of 800 mm/min, the study showed that high emission of ester at cutting zone was found for fluid with low viscosity. it recommended a lubricant should have at least 10 mm 2 /s kinematic viscosity at 40˚c, flash point of at least 150˚c, and evaporation loss of maximum 65% at 250˚c for low emissions of aerosol in mql [20]. this recommendation was also cited in the german standard din en iso 2592. contact angle between a solid and liquid interface can directly affect the wettability of the liquid. a low contact angle between a solid and liquid interface results in liquid spreading over more area on the solid surface, improving the wettability of the liquid and its effectiveness as cutting fluid. li et al. [21] characterized micromist using a unist mql system and four lubricants, viz., coolube 2210, 2210ep, 2300hd, and 2200. these oils were tested on 316l stainless steel, titanium, and tungsten carbide to measure contact angles. input air pressure was varied from 200 to 600 kpa, and lubricant flow rate was maintained at 1.32 ml/hr. micromist flow was captured using particle image velocimetry (piv) and a hi-sense mkii ccd camera. the distance between the nozzle and the glass plate was 130 or 150 mm. the olympus stm6 microscope was used for droplet size measurement and contact angle measurements. characterization and performance of minimum quantity lubricants in through-tool drilling 100 airspeed of the micromist was measured using a 1 mm diameter needle probe of the kanomax climomaster 6501 anemometer. a high air pressure produced faster air speed exiting from the nozzle (up to 7000 m/min) and produced finer microdroplet sizes of 4-6 µm from the coolube 2210ep. this lubricant gave the smallest contact angles of 7±5° on 316l stainless steel as compared to 45±5° for distilled water. tai et al. [22] studied nine commercial mql fluids including biodegraded esters, renewable acid esters, synthetic esters, etc., and compared their thermal conductivity, wettability, lubricity, machinability and mist generation properties. the study showed that although wettability and lubricity improved for mql fluids, heat removal property was relatively weak. wettability was better for mql fluids that formed small contact angles about 8˚ to 27˚ on polished aluminium and tungsten carbide. however, the waterbased coolant trimsol with 5% concentration, showed contact angle of about 35˚ on the same polished solids. the a380 aluminium is die cast to make engine blocks in automobile industry. deep hole drilling at fast production rate using internal mql is required. this study compares two commercially available lubricants and finds optimal mql parameters for drilling this aluminium alloy. 3 experiments die cast a380 aluminium plates (420 x 175 x 24 mm thick) were commercially obtained. typical a380 aluminium alloy (wt% 7.5-9.5 si, 3-4 cu, 3.0 zn, 1.3 fe, 0.5 mn, and balance al) has 324 mpa ultimate tensile strength, 159 mpa yield strength, 3.5% elongation, and 80 hb hardness [23]. the following section describes setups and procedures to measure contact angles, characterize the resulting microdroplets, observe the forming of microdroplets out of the drill lubricant channels, drill the aluminium plate, and finally assess the drilled hole quality. 3.1. contact angle measurement sessile-drop technique was utilized to measure contact angles of both lubricants. the flat surfaces of a glass panel or a polished a380 cast aluminium block were cleaned with acetone before each experiment. microdroplets, 0.1 µl volume that dispensed from the socorex micropipette, were carefully deposited on the horizontal solid surface. the projected images of at least ten microdroplets were measured using the olympus stm6 measuring microscope with 0.1 µm resolution. coordinates of multiple points on a microdroplet perimeter were recorded for calculating the average microdroplet diameters. care was practiced avoiding microdroplets near a surface defect such as microscratches or pore on the cast aluminium block. 3.2. microdroplet characterization the unist system and setup, simulated a dual channel mql system, generated micromist microdroplets into a stationary drill with dual coolant channels (fig. 1). controlled pressured air, flowing through the unist system via a coaxial tube, mixed with the liquid lubricant and delivered the aerosol mixture at the drill shank. the mixture then flowed inside the dual channel drill following the tool helix angle and emitted out from two circular holes at the drill tip. details of the drills and lubricants are listed in tables 1-2. the unist system pumped 40 strokes/min that delivered 0.016 ml/stroke (38.4 ml/hr). the distance between drill tip and the horizontal glass panel was 355 mm for best distribution and collection of the microdroplets. the stationary drills and all experiments were conducted in still air, assuming (i) insignificant effect of drill rotation, and (ii) negligible evaporation of airborne microdroplets. the input air pressure was at three levels to study the resulting microdroplets and flow pattern: 413 kpa (4.13 bar, 60 psi), 551 kpa (5.51 bar, 80 psi), and 689 kpa (6.89 bar, 100 psi). air flow rates were fixed at 0.566 and 1.7 m 3 /hr for the 4 and 8-mm drills respectively. figure 1b: an ø8mm drill with symmetric lubricant channels. figure 1a: experimental setup for microdroplet characterization. where, a: unist coolubricator system, b: air filter/regulator, c: air flow meter, d: pressure gage, e: lubricant reservoir, f: copper tube, g: pressurized aerosol chamber, h: drill with dual internal coolant channels, and i: glass panel. a c e d b f g h i 1 mm lubricant channel 1st flank face 2nd flank face rotation patil et al., (2020): international journal of engineering materials and manufacture, 5(4), 98-115 101 table 1. specifications of tested drills specifications small drill [24] large drill [25] measured drill diameter (mm) 3.889 8.0 (nominal) drill diameter for lubricant c (mm) n/a 7.9950±0.0007 drill diameter for lubricant a (mm) n/a 7.9958±0.0008 drill diameter for lubricant b (mm) n/a 7.9952±0.0004 number of flutes 2 2 coolant channel diameter (mm) 0.7 1.0 distance between coolant channels (mm) 2.4 3.8 helix angle (˚) 20 15 included /point angle (˚) 140 135 table 2. tested oil-based lubricants properties lubricant a lubricant b kinematic viscosity at 40°c (mm 2 /s) 14.5 28 flashpoint (°c) 93 180 density (kg/l) 0.82-0.92 at 60°c 0.838 at 20°c thermal conductivity at 40°c (w/m °k) not available 0.1593 a glass plate (220 x 280 x 3mm thick) was divided into 8 different 25x25 mm zones, each at a unique radial distance and polar angle from the drill tip projection position (table 3). the glass plate was cleaned with ammonia-based glass cleaner and acetone before each experiment. after verifying the steady state of mql aerosol flow with visual oil wetting on a piece of paper, a diaphragm was opened for 2 seconds to allow optimal deposition of microdroplets on the glass plate below. the plate was immediately positioned under the olympus stm6 measuring microscope for capturing closed-up images of the microdroplets. five random pictures were taken within each zone for analysis. the built-in light of the microscope had minimum intensity in still air to minimize vaporization of oil microdroplets during this operation. the captured microdroplet images were enhanced and statistically analysed using adobe photoshop and imagej software. each picture was calibrated by comparing number of pixels and a known distance. the areas of projected microdroplets and known contact angle were used to calculate the airborne microdroplet sizes. the kmeans clustering method was used to characterize the microdroplets. before switching to a new oil, the reservoir and connecting hose of mql system were first rinsed with warm water and liquid soap, and then operated with dry air to flush out the water. after filling the reservoir with a new oil, the system was operated for at least 15 minutes to flush out any remained soapy water. table 3. different zones for microdroplet collection zone # 1 2 3 4 5 6 7 8 radial distance (mm from drill tip projection) 0 39 51 40 61 61 93 93 radial angle (°) 0 220 270 320 25 155 235 305 3.3. microdroplet formation and flow macro images of microdroplets and flow at the drill tip were captured for both lubricants. showing in fig. 2, a drill was positioned between the high-speed camera photron fastcam sa5 and the halogen work light e216569. three tandem extension tubes of 12, 20, and 50 mm were attached in front of the camera lens to reduce the effective focus length. a white paper sheet was placed on the lamp and optimally placed at a long distance from the drill for best background illumination while reducing heat to the aerosol. the unist system pumped at 40 strokes/min and delivered 0.016 ml/stroke. after the mql reaching its steady state, a diaphragm was unblocked, and the camera was kept on for 0.47 second to capture 42,000 frames/s at 1 µs shutter speed and 512 x 320 pixels/frame. the photron fastcam viewer version 4.0 was used to analyse subsequent images. figure 2. setup for viewing microdroplet formation and flow. where, a: photron video camera with extension tubes, b: drill, and c: light source. the distances were selected for optimal focus and lighting. 76 mm 280mm a b c characterization and performance of minimum quantity lubricants in through-tool drilling 102 3.4. drilling production rate drilling was implemented to drill the die cast a380 aluminium plate with 8 mm drills. each new drill was used with a different coolant while keeping drilling parameters constant 1 . the studies were carried out at two different locations where internal mql and lubricants were available. drilling with flood coolant and dry conditions were also experimented for comparison. table 4 details the drilling study and process parameters. two-level factorial experiments, with two replicates, were used to study the effect of air pressure (413, 620 kpa) and mql oil quantity (40, 60 ml/hr) on the hole quality. the experiments were then repeated at the same air pressure range but at much higher mql oil quantity (100, 400 ml/hr). the same drill was used to drill five consecutive holes at each condition, and a total of 80 holes were drilled for each lubricant with machines at locations a and b. at location c a new drill was utilized for drilling with flood coolant for a total of 20 holes, and the same drill was used for the final drilling at dry condition. table 4. drilling experiments location a location b location c cnc drilling machine haas vf2 grob 515 5-axis (b/a) fanuc robodrill, α d21lib5 spindle speed capacity (rpm) 15,000 16,000 10,000 cutting fluid type mql mql flood, water soluble cutting fluid lubricant a lubricant b coolant c cutting speed (m/min) 250 250 250 spindle speed (rpm) 9,950 9,950 9,950 chip load (mm/flute) 0.20 0.20 0.20 feed rate (mm/min) 3,980 3,980 3,980 mql oil quantity (ml/hr) 40, 60, 100, 400 40, 60, 100, 400 n/a flood coolant quantity (l/hr) n/a n/a 340, 5678 air pressure (kpa (psi)) 413, 620 (60, 90) 413, 620 (60, 90) n/a flood coolant concentration (%) n/a n/a 5, 10 flood coolant pressure (kpa (psi)) n/a n/a 76, 83 (11, 12) 3.5. metrology after machining, the profiles of drill cutting edges were scanned with the alicona optical 3d profiler for possible tool damage during drilling. the machined plate and all holes were cleaned with alcohol and blow-dried with compressed air before measuring. for each hole, its diameter and cylindricity were measured with the mitutoyo strato-apex 7106 coordinate measuring machine and programmed using the accompanying software (mcosmos-3 version 3.2 r6 edition 6). after setting the coordinate system on the plate with origin at one of the plate corners, five points were probed at hole depth level of 3, 9, and 15 mm from the top (drill entrance position) for hole diameters and hole cylindricity (fig. 3). figure 3. schematic of cylindricity measurement for each drilled hole. the typical numbers (1-5) represent probed points on a circle 3 mm below the drilled hole entrance. unit: mm 1 machinery handbook, 29 ed., p 1043. drill entrance drill exit patil et al., (2020): international journal of engineering materials and manufacture, 5(4), 98-115 103 4 results and discussion 4.1 contact angles figure 4. airborne microdroplet and a sessile microdroplet on a flat solid. in the sessile drop technique, a small microdroplet would form a spherical shape in air or on a flat solid surface to minimize its surface energy (fig. 4). it can be shown that the drop volume v of a sessile drop, its projection size p and the contact angle θ are related by [26]: 𝑃 𝑉1/3 = [( 24 𝜋 ) ( (1 − 𝑐𝑜𝑠2𝜃)3/2 2 − 3𝑐𝑜𝑠𝜃 + 𝑐𝑜𝑠 3𝜃 )] 1/3 (1) table 5. resulted contact angles solid substrate glass polished a380 lubricant a b a b projected diameter (mm) resulted from 0.1 µl oil drops 2.188 1.515 1.557 1.218 2.288 1.560 1.394 1.429 2.249 1.559 1.266 1.100 2.201 1.317 1.426 1.239 2.150 1.326 1.318 1.072 2.130 1.230 1.349 1.237 2.143 1.248 1.353 1.100 2.089 1.453 1.306 1.407 2.108 1.435 1.323 1.131 2.126 1.506 1.336 1.176 2.408 1.508 1.047 1.253 2.398 1.528 1.863 1.133 2.126 1.507 1.414 1.094 2.116 1.190 1.552 1.256 2.133 1.223 1.851 1.119 average diameter (mm) 2.190±0.101 1.407±0.135 1.424±0.212 1.198±0.110 contact angle (°) 5.60±0.70 21.49±6.31 21.81±8.63 33.16±7.27 since glass and a380 aluminium have different surface energies, it is expected and confirmed that the respective contact angles would be different on each material. table 5 shows that the lubricant a forms smaller contact angles than those of lubricant b on both glass (6° versus 21°) and aluminium (22° versus 33°). this implies that the former lubricant can (i) cover and wet a larger area for more efficient heat transfer and (ii) self-spread by capillary action to bring lubricant to a hard-to-reach area such as tool/chip interface. the better wetting of lubricant a was due to its lower surface energy and lower viscosity [14]. 4.2 airborne drop sizes a raw image of microdroplets deposited on a glass plate was enhanced using photoshop and then converted to binary format using imagej software (fig. 5). the area and projected size of each microdroplet can then be calculated and tabulated. assuming no evaporation of the lubricant, a spherical airborne microdroplet with volume va and diameter d would deposit on the glass plate and form a tiny sessile microdroplet with the same contact angle (fig. 4). define p: projected size of a sessile drop from micropipette v: volume of a sessile drop, set with the micropipette pa: projected size of an mql sessile microdroplet va: volume of an airborne mql microdroplet d: diameter of an airborne mql microdroplet characterization and performance of minimum quantity lubricants in through-tool drilling 104 since the ratio p / (v) 1/3 is a function of contact angle only, equation (1) yields: 𝑃3 𝑉 = 𝑃𝑎 3 𝑉𝑎 = ( 24 𝜋 ) ( (1 − 𝑐𝑜𝑠 2𝜃)3/2 2 − 3𝑐𝑜𝑠𝜃 + 𝑐𝑜𝑠3𝜃 ) = constant (2) since the volume of a spherical airborne microdroplet is the same with microdroplet volume deposited on the glass: 𝑉𝑎 = 𝜋 6 𝑑3 = 𝑉 ( 𝑃𝑎 𝑃 ) 3 (3) by combining equations (2) and (3), the airborne microdroplet diameter d can then be calculated as: 𝑑 = 𝑃𝑎 𝑃 ( 6𝑉 𝜋 ) 1/3 (4) (a) typical image of microdroplets at location 0 mm radial distance from the drill projection. (b) typical image of microdroplets at location 93.4 mm radial distance from the drill projection. figure 5. images of lubricant b microdroplets on glass after spraying at 413 kpa. left to right: raw images, after enhanced with photoshop, and after conversion to binary format with imagej. the distributions of airborne microdroplets due to different air pressures and drill diameters are presented in figs. 67. for mql drop size analysis, the main difference in drill size is the diameters of lubricant hole channels. the channel hole diameter on the larger drill is 1.0 mm while that for the smaller drill is 0.7 mm (table 1). the summary of all means and standard deviation of microdroplets from both figs. 6-7 is shown in fig. 8. it is found that:  the averaged drop size decreases with increase in air pressure. a higher pressure breaks down a lubricant drop into smaller drops as also experimentally shown in other studies [15, 21].  the larger drill with large coolant hole channel produces smaller drop size. the average air speed, exiting out of the larger lubricant hole, is about 300 m/s while that from a smaller hole is approximately 200 m/s (table 6). these air speed magnitudes in this study are very close to experimental data from different coolant hole channels and seem independent of the tested air pressure in the range 4.3-10 bars (430-1000 kpa) [27]. a highspeed air might flow turbulently in a helical channel and further break down large lubricant drops. similar conclusion was also obtained by others [15-17, 20, 28].  the smallest average airborne drop sizes (about 8 µm) can be produced with the 8 mm drill using lubricant a at 551 kpa pressure. these conditions also provide the most uniform drop size (minimum standard deviation). table 6. air speed calculation drill size (mm) coolant hole (mm) hole area (m 2 ) total air flow (m 3 /hr) air speed (m/min) air speed (m/s) 4 0.7 3.85 x 10 -7 0.566 12,256 204 8 1 7.85 x 10 -7 1.700 18,038 301 1 mm 1 mm 1 mm 1 mm 1 mm 1 mm patil et al., (2020): international journal of engineering materials and manufacture, 5(4), 98-115 105 air pressure (kpa) 4 mm drill (air flow rate 0.566 m 3 /hr) 8 mm drill (air flow rate 1.7 m 3 /hr) 413 551 689 figure 6. airborne drop size distribution. mean and standard deviation of lubricant a’s microdroplets at different air pressures. 0 100 200 300 400 500 600 700 800 900 1000 5 2 0 3 5 5 0 6 5 8 0 9 5 1 1 0 1 2 5 1 4 0 d ro p le t c o u n t 0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 5 2 0 3 5 5 0 6 5 8 0 9 5 1 1 0 1 2 5 1 4 0 d ro p le t c o u n t 0 100 200 300 400 500 600 700 800 900 1000 5 2 0 3 5 5 0 6 5 8 0 9 5 1 1 0 1 2 5 1 4 0 d ro p le t c o u n t 0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 5 2 0 3 5 5 0 6 5 8 0 9 5 1 1 0 1 2 5 1 4 0 d ro p le t c o u n t 0 100 200 300 400 500 600 700 800 900 1000 5 2 0 3 5 5 0 6 5 8 0 9 5 1 1 0 1 2 5 1 4 0 d ro p le t c o u n t droplet diameter (μm) 0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 5 2 0 3 5 5 0 6 5 8 0 9 5 1 1 0 1 2 5 1 4 0 d ro p le t c o u n t droplet diameter (μm) mean: 39 µm sd: 33 µm mean: 12 µm sd: 8 µm mean: 8 µm sd: 6 µm mean: 29 µm sd: 25 µm mean: 9 µm sd: 6 µm mean: 28 µm sd: 23 µm a b d c e f characterization and performance of minimum quantity lubricants in through-tool drilling 106 air pressure (kpa) 4 mm drill (air flow rate 0.566 m 3 /hr) 8 mm drill (air flow rate 1.7 m 3 /hr) 413 551 689 figure 7. airborne drop size distribution. mean and standard deviation of lubricant b’s microdroplets at different air pressures. 0 100 200 300 400 500 600 700 800 900 1000 5 2 0 3 5 5 0 6 5 8 0 9 5 1 1 0 1 2 5 1 4 0 d ro p le t c o u n t 0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 5 2 0 3 5 5 0 6 5 8 0 9 5 1 1 0 1 2 5 1 4 0 d ro p le t c o u n t 0 100 200 300 400 500 600 700 800 900 1000 5 2 0 3 5 5 0 6 5 8 0 9 5 1 1 0 1 2 5 1 4 0 d ro p le t c o u n t 0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 5 2 0 3 5 5 0 6 5 8 0 9 5 1 1 0 1 2 5 1 4 0 d ro p le t c o u n t 0 100 200 300 400 500 600 700 800 900 1000 5 2 0 3 5 5 0 6 5 8 0 9 5 1 1 0 1 2 5 1 4 0 d ro p le t c o u n t droplet diameter (µm) 0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 5 2 0 3 5 5 0 6 5 8 0 9 5 1 1 0 1 2 5 1 4 0 d ro p le t c o u n t droplet diameter (µm) mean: 26 µm sd: 23 µm mean: 19 µm sd: 18 µm mean: 17 µm sd: 15 µm mean: 24 µm sd: 23 µm mean: 18 µm sd: 16 µm mean: 24 µm sd: 22 µm a b d c e f patil et al., (2020): international journal of engineering materials and manufacture, 5(4), 98-115 107 figure 8 also shows that the numerical values of standard deviations are comparable to those of the mean airborne microdroplet diameters. a different approach was implemented for a better estimate. instead of considering the average value of the whole data set, the microdroplets were divided statistically into different clusters depending on their sizes for further analysis. due to the large variation in airborne diameters, the k-means clustering method was used to divide all microdroplets into groups or clusters with different diameter ranges. for results of all cases, the “elbow method” was used to plot the within-cluster sum of square against number of possible number of clusters k (from 1 to 15) [29-31]. figure 9 below shows typical elbow plots for airborne drop diameters of both oils with 4 mm drill operating at 551 kpa air pressure. there is a sudden drop in sum of squares at k = 3 in every case; therefore, the total number of clusters is chosen to be three for effective comparison in all the cases and avoid overfitting of the data. figures 10a-d summarize the average airborne diameters resulted from the 4 and 8 mm drills at different pressures and oil types. for both the lubricants, the number of microdroplets collected from 8 mm drill was much more than those from the 4 mm drill due to the larger lubricant hole and higher air speed. the drop sizes can be divided into 3 clusters: clusters 1, 2, and 3 are for small, medium, and large drop size respectively.  the variations within one cluster, shown as the error bars in fig. 10, are much smaller than the drop size deviation in fig. 8.  higher pressure reduces the average airborne drop size for all clusters, drill sizes, and lubricants. notice the logscale on the vertical axis. this trend was confirmed with data from other published studies [15, 32].  the larger drill size with larger channel hole generates smaller airborne microdroplets for lubricant a (figs. 10ab). similar results are seen for lubricant b (figs. 10c-d).  lubricant a produces smaller microdroplets than lubricant b for all clusters and drill sizes when operating at the same air pressure. figure 8. summary of mean and standard deviation of airborne drop size distribution. figure 9. elbow plots for airborne microdroplet diameters for both lubricants. 4 mm drill at 551 kpa air pressure. 0 10 20 30 40 400 500 600 700 a ve a ir b o rn e d ro p d ia m e te r (µ m ) air pressure (kpa) lubicant a, 4mm drill lubricant b, 4 mm drill lubricant a, 8mm drill lubricant b, 8mm drill 0 10 20 30 40 400 500 600 700 s ta n d a rd d e vi a tio n ( µ m ) air pressure (kpa) lubricant a, 4mm drill lubricant b, 4mm drill lubricant a, 8mm drill lubricant b, 8mm drill lubricant a lubricant b characterization and performance of minimum quantity lubricants in through-tool drilling 108 (a) lubricant a, 4mm drill (b) lubricant a, 8mm drill (c) lubricant b, 4mm drill (d) lubricant b, 8mm drill figure 10. clusters showing effects of drill size and air pressure on airborne microdroplets. 4.3 microdroplet formation and flow high speed imaging technique was used to capture the microdroplet formation and flow of lubricants at the drill tip. the camera was not synchronized with the unist pump; therefore, the time sequence of each picture was not corresponding with the pump frequency. due to the relative low resolution of the video camera, microdroplets smaller than 50 µm moving at high speed were not visible --although they were clearly visible with the olympus microscope after depositing on a glass plate as mentioned above. the smaller 4mm drill with 0.7 mm lubricant hole diameter was chosen in this part of the study since its smaller hole and spiral shape in space would be more difficult for the oil mist to flow. other factors that affected the flow would include hole shape, air pressure [16-18], oil viscosity, surface tensions of oil and drill materials. the aerosol flowing out of a stationary drill was shown to approximately equivalent to that from a rotating drill since the lateral speed due to spindle rotation was very small compared to the exiting air speed at the drill tip [16]. figure 11 captures the microdroplet formation of lubricants a and b at the drill tip. the two columns show the 265 th and 669 th image frames for lubricant a and b respectively.  it took the lubricant b a longer response time to flow out of small coolant hole due to its higher viscosity (28 mm 2 /s) compared to that of lubricant a (14.5 mm 2 /s). visible microdroplet formation is seen after 6 ms for lubricant a, but not until 16 ms for lubricant b.  at the low pressure of 413 kpa, visible large airborne drops of lubricant a are seen (fig. 11a) but a large amount of lubricant b is still adhered to the drill tip (fig. 11b). high viscosity and low surface tension promote the adhesion of lubricant b to the drill tip.  at the medium pressure of 551 kpa, both oil pools at the drill tip are broken up to form long string-like oil threads (figs 11c-d).  when further increasing the air pressure to 689 kpa, the oil thread is still visible for lubricant b (fig. 11f), but such oil thread is completely disintegrated into airborne microdroplets for lubricant a (fig. 11e). 2 0 8 2 2 1 1 1 6 5 6 1 2 7 1 5 4 9 1 0 7 1 10 100 1000 cluster 1 cluster 2 cluster 3 a ve ra g e a ir b o rn e d ia m e te r (µ m ) 413 kpa 551 kpa 689 kpa 7 1 7 3 5 5 1 2 2 3 5 1 2 2 3 1 10 100 1000 cluster 1 cluster 2 cluster 3 a ve ra g e a ir b o rn e d ia m e te r (µ m ) 413 kpa 551 kpa 689 kpa 2 2 1 3 8 6 4 3 1 8 7 1 2 3 1 1 8 9 3 2 8 2 1 10 100 1000 cluster 1 cluster 2 cluster 3 a ve ra g e a ir b o rn e d ia m te r (µ m ) 413 kpa 551 kpa 689 kpa 1 2 4 1 1 1 9 1 0 3 1 7 4 9 2 9 6 8 1 10 100 1000 cluster 1 cluster 2 cluster 3 a ve ra g e a ir b o rn e d ia m e te r (µ m ) 413 kpa 551 kpa 689 kpa patil et al., (2020): international journal of engineering materials and manufacture, 5(4), 98-115 109 air pressure (kpa) lubricant a (265 th frame at 6 ms) lubricant b (669 th frame at 16 ms) 413 551 689 figure 11. microdroplet formations at the 4 mm drill tip due to different air pressures. in this dual channel mql system, the aerosol was atomized in a small chamber just before entering the two coolant holes of the twist drill. upon entering the small channels, oil microdroplets must flow and impact the coolant channel wall since the channel axis was spirally downstream of the aerosol flow. it was postulated that most microdroplets would combine and become liquid flowing slowly downstream on the channel wall (fig. 11b). the motion of oil liquid in the channel was affected by competing factors among viscosity of the oil, wetting of the wall surface, surface finish of the wall, gravity, air pressure, and low air speed at the wall. when flowing out of the channel and accumulated at the channel exit near the drill tip, the oil was atomized again and formed new microdroplets into the air stream (fig. 11d); the oil atomization was cyclically activated since oil was pumped at the setup frequency of the unist system. in flight coalescence of microdroplets was also evidenced due to overlapping jet streams from two channels in front of a drill tip (fig. 11c). complete atomization is achieved at air pressure of at least 689 kpa for low viscous oil such as the lubricant a (fig. 11e). two microdroplet formation mechanisms are evident in the high-speed video. recall that the unist system operated at 40 strokes/min (0.67 hz) in this study. during the inactive stroke, the system sucked in 0.016 ml of lubricant from the reservoir and then pumped this volume to the air-jet stream during its active stroke. under a steady air flow, microdroplets are formed continuously, but additional microdroplets are formed during the active pump stroke. b 1 mm 1 mm a d c e f 1 mm 1 mm 1 mm 1 mm coolant hole 2x drill center line 2x characterization and performance of minimum quantity lubricants in through-tool drilling 110  during the inactive stroke some oil microdroplets deposit on the inner channel wall, form a stream of lubricant, flow downstream with additional gravity effect, and then collect as a lubricant pool at the drill tip. when the cumulative volume of lubricant is sufficient large, the air stream then breaks the lubricant pool into oil strings and large microdroplets (fig. 12a).  during the active stroke, a fresh volume of lubricant is pumped into the air-jet stream and atomized inside the aerosol reservoir positioned above the drill shank (label “g” in fig. 1a). the newly atomized aerosol then flows into both lubricant channels and exits out of the holes near the drill tip (figs. 12b, d). cyclic bursts of oil microdroplets can be seen in synchronicity with the pumping frequency. coalescence of airborne microdroplets are expected from the large microdroplets that come from the pool at drip tip and the smaller microdroplets that exit from the lubricant channels. notice that the fine aerosol streams are visible at each hole exits near the drill centreline. perhaps there are finer microdroplets at the exit holes away from the centreline, but such micronlevel airborne microdroplets are not captured due to insufficient resolution of the photron camera in this study. (a) inactive stroke, 507 th frame @12ms, 551 kpa (b) active stroke, 885 th frame@21ms, 551 kpa (c) inactive stroke, 730 th frame@17ms, 689 kpa (d) active stroke, 815 th frame@19ms, 689 kpa figure 12. effect of pump frequency on microdroplet formation. lubricant a, 4 mm drill, pump frequency 0.67 hz (40 strokes/min). 4.4 drilled hole quality define the “hole oversize” and “cylindricity” as: hole oversize = (measured hole diameter) (measured drill size) (5) cylindricity = radial deviation of all circles on a right cylinder (6) the hole oversize is due to one or combining effects of:  vibration of tool and/or workpiece  runout of machine tool spindle  defective drill  drill with poor cylindricity  travel error of the machine tool axis  thermal distortion during machining  redistribution of residual stress  tool degradation during drilling  material defects  etc… 1 mm 1 mm 1 mm 1 mm patil et al., (2020): international journal of engineering materials and manufacture, 5(4), 98-115 111 figure 13. average hole oversize and cylindricity of drilled holes. it is assumed that:  thermal effects are insignificant when copious coolant is used  insignificant carbide drill wear when machining the soft cast aluminium alloy  there is no performance difference among three different cnc drilling machines  cast defects, such as porosity, do not affect the drilling process or measuring results  low residual stress in the cast plate 8.4 5.7 5.1 7.4 8.2 5.9 6.5 8.7 0 2 4 6 8 10 0 5 10 15 20 40 ml/hr 60 ml/hr 100 ml/hr 400 ml/hr 40 ml/hr 60 ml/hr 100 ml/hr 400 ml/hr 413 kpa 620 kpa c yl in d ri ci ty ( µ m ) h o le o ve rs iz e ( µ m ) hole oversize cylindricitya. lubricant a coolube 7.4 8.6 6.3 7.5 4.3 5.6 6.0 6.5 0 2 4 6 8 10 0 5 10 15 20 40 ml/hr 60 ml/hr 100 ml/hr 400 ml/hr 40 ml/hr 60 ml/hr 100 ml/hr 400 ml/hr 413 kpa 620 kpa c yl in d ri ci ty ( µ m ) h o le o ve rs iz e ( µ m ) hole oversize cylindricityb. lubricant b 7.1 5.9 6.1 5.4 0.0 2.0 4.0 6.0 8.0 10.0 0 5 10 15 20 5% 10% 5% 10% 340 l/hr @76 kpa 5678 l/hr @83 kpa c yl in d ir ic ity ( µ m ) h o le o ve rs iz e ( µ m ) hole oversize cylindricity c. coolant c 9.8 31.2 8.2 0.0 0 10 20 30 40 0 2 4 6 8 10 hole #1 hole #2 hole #3 hole #4 c yl in d ri ci ty ( µ m ) h o le o ve rs iz e ( µ m ) hole oversize cylindricity d. dry tool failure characterization and performance of minimum quantity lubricants in through-tool drilling 112 the three different machines were used to avoid changing cutting fluids and possible cross contamination. only the last test was performed without coolant. the drilling parameters for production mode (250 m/min, 0.20 mm/flute) were referenced from the machinery handbook for carbide tool and a380 cast aluminium. no pecking was programmed to simulate a fast production environment. figure 13 plots the hole deviation and hole cylindricity for all test data. each data point is the average of measurements from five holes that were drilled at the same conditions and two replicates (total of 10 holes). drilling without coolant (dry condition) generated significant built-up edge and friction between the drill and workpiece. after drilling 3 holes on the plate, the drill was twisted off during drilling the 4 th hole. table 7 and figure 14 summarize the information from figure 13. the data suggest:  there is no significant impact of oil quantity to the drilled hole quality. it would be more cost effective and environmentally friendly to use either lubricant a or b at 40 ml/hr instead of 400 ml/hr. similarly, the concentration of lubricant c could be 5% instead of 10%.  drilling with lubricant b as mql oil provided the least hole oversize. the average of hole oversize for drilling all 80 holes was 5.0 µm.  drilling with lubricant c as flood coolant generated the best hole shape with 6.1 µm cylindricity and lowest standard deviation. perhaps the least amount of heat that generated during drilling in this water-soluble flood coolant would minimize thermal distortion in the workpiece [3, 33]. table 7. summary of hole oversize and cylindricity hole oversize (µm) cylindricity (µm) lubricant average standard deviation average standard deviation lubricant a 7.8 1.6 7.0 1.8 lubricant b 5.0 1.4 6.5 2.1 coolant c 6.4 1.5 6.1 1.0 dry 4.5 3.6 16.4 12.8 figure 14. summary of hole oversize and cylindricity cutting flute profiles of a drill were scanned after drilling in both mql lubricants. the tool used after flood cooling and dry drilling was not scanned since it was broken and embedded into the partially drilled hole. microscopic examination shows wear on one of the cutting flutes after drilling with lubricant a (fig. 15a). abrasive wear of the drill on one flute (i) might be caused by tool defect rather than normal tool wear in drilling since the other flute remains sharp after all tests, (ii) may cause imbalance and affect the hole oversize and cylindricity as measured and summarized in table 7. figure 15b shows significant built-up edges (bue) near the drill centre (chisel edge) after drilling with lubricant b; it is common to have bue on cutting tools when machining a soft material such as aluminium at low cutting speed – as seen at the drill centre [34-35]. however, such bue is minimum on the drill lubricated with lubricant a. lack of bue on tool with lubricant a could be due to the effective lubrication of this oil; recalled that lubricant a formed smaller contact angle on aluminium compared to lubricant b which implied better wetting and lubrication. surface finish would be affected by bues since they smear and deposit on drilled surface. it is true that tool coating could minimize bue and improve the part quality [13,36], but it would be cost prohibitive to recycle coated drills with through-tool mql channels. 7.0 6.5 6.1 16.4 0 5 10 15 20 0 2 4 6 8 10 lubricant a lubricant b coolant c dry c yl in d ri ci ty (µ m ) h o le o ve rs iz e ( µ m ) hole oversize cylindricity 1.8 2.1 1.0 12.8 0 4 8 12 0 1 2 3 4 5 lubricant a lubricant b coolant c dry c yl in d ri ci ty : s ta n d a rd d e vi a tio n ( µ m ) h o le o ve rs iz e : s ta n d a rd d e vi a tio n (µ m ) hole oversize cylindricity patil et al., (2020): international journal of engineering materials and manufacture, 5(4), 98-115 113 figure 15. drill edge profiles after drilling 80 holes. (a) abrasive wear on one flute after drilling with lubricant a and (b) built-up edges (bue) when drilling with lubricant b. published data on external mql have shown that smaller airborne drop size improved machinability [15]. in internal mql drilling the aerosol that exiting out of the coolant channels would flow against the drill rotation direction on the second flank face of the drill, and then fill the 3-dimensional space confined by a flute rake face and its spiral surface (fig 1b). smaller microdroplets with high wetting capability can (i) penetrate the interface between the chips and drill cutting edges, and (ii) cool the chip and tool effectively. thermal conductivity of an oil affects the cooling rate and reduces tool wear. viscosity affects the capillary motion; a less viscous lubricant penetrates the tool/chip interface and lubricates both cutting edges of the drill and reduces bue formation. the german din standard en iso 2592 [20] recommends the minimum viscosity of 10 mm 2 /s for mql oil. this limit is met for both oils in this study, however, the lubricant a’s viscosity (14.5 mm 2 /s) is about half of that for lubricant b (28 mm 2 /s). using a low viscosity oil may shorten the drilling cycle time since the less viscous oil reaches mql aerosol state faster (shorter response time) for each oil pumping cycle (fig. 11 a-d) and less time to flow from oil reservoir and along a long narrow tube to the atomization chamber. further regression and anova analysis of the hole oversize and cylindricity was performed. the models for hole oversize and cylindricity for each lubricants are shown below. for lubricant a: 𝐻𝑜 = 10.90 − 4.81 × 10 −3 𝐴𝑝 − 3.85 × 10 −3 𝑂𝑞 (7) 𝐶𝑦 = 4.99 + 2.86 × 10 −3𝐴𝑝 + 3.57 × 10 −3 𝑂𝑞 (8) for lubricant b: 𝐻𝑜 = 0.75 + 6.73 × 10 −3𝐴𝑝 + 2.13 × 10 −3 𝑂𝑞 (9) 𝐶𝑦 = 11.01 − 9.33 × 10 −3𝐴𝑝 + 2.31 × 10 −3 𝑂𝑞 (10) for lubricant c (flood coolant): 𝐻𝑜 = 5.20 + 9.8 × 10 −5 𝐹𝑓 + 0.119 𝐶𝑐 (11) 𝐶𝑦 = 7.94 − 1.35 × 10 −4𝐹𝑓 − 0.189 𝐶𝑐 (12) where, ho : hole oversize (µm) cy : cylindricity (µm) ap : air pressure (kpa) oq : oil quantity (ml/hr) ff : flood coolant flow (l/hr) cc : coolant concentration in water (%). the above models, however, were not conclusive since r 2 < 10% and p-value > 0.05. perhaps the data were affected by testing that performed on different machines with different rigidity, accuracy, repeatability, and spindle runout. any variation of machine tool conditions could invalid the above assumptions and affect measurement results of the drilled holes. it is also recommended that at least 3-level experiment with pressure values should be performed for drilling. 5 conclusions and recommendations this study characterized two commercially available lubricants a and b for internal minimum quantity lubrication (mql), and then performed through-tool mql drilling on a380 cast aluminium at fast production rate. drilling using flood water-soluble coolant c was also experimented for comparison. the research showed: 1) contact angles of lubricant a on glass and aluminium were at least 10° less than those from lubricant b. the low contact angle promoted wetting for effective lubricating and cooling. 2) statistical analysis of air borne microdroplets was completed. clustering method divided the airborne microdroplets into three clusters for comparison. the drop sizes were reduced due to higher air pressure and larger coolant channel. lubricant a microdroplets were smaller than lubricant b’s for all clusters, drill sizes at same operating conditions. 3) high speed video camera was used to observe the microdroplet formation and mql flowing out of a drill channel. lubricant a, with lower viscosity, flowed easily and was atomized at lower air pressure than lubricant b. in flight microdroplet coalescence was observed due to overlapping regions of the mql jet streams. high oil pumping frequency produced consistent quality of aerosol and should be used in high speed machining or high production mode. 1 mm 1 mm a bue drill center b wear bue characterization and performance of minimum quantity lubricants in through-tool drilling 114 4) drilled hole quality was measured by cylindricity and deviation of hole diameter. drilling in mql with lubricant b produced the most consistent hole size while drilling in flood coolant c produced the holes with best cylindricity. drilling with lubricant a reduced built-up-edge on the drill cutting edges. future studies should: a) minimize machining variation by drilling with one cnc machine to truly compare the effect of different mql lubricants assuming a rigid setup and no cross contamination of lubricants. b) consider surface finish as part of drilled hole quality since built-up edges on a tool could smear and degrade a machined surface. c) assess the effectiveness of internal mql by deep drilling engineering alloys with poor machinability such as tool steel, inconel or cobalt-chrome. acknowledgement the authors thank ford, unist, and mitutoyo for their kind supports. this material is based upon work supported by the national science foundation under the goali grant no. 1760985. references 1. dasch, j. m., & kurgin, s. k. (2010). a characterisation of mist generated from minimum quantity lubrication (mql) compared to wet machining. machining and machinability of materials, 7(1–2), 82–95. https://doi.org/10.1504/ijmmm.2010.029847 2. aized, t., & amjad, m. (2013). quality improvement of deep-hole drilling process of aisi d2. advanced manufacturing technology, 69(9–12), 2493–2503. https://doi.org/10.1007/s00170-013-5178-4 3. bono, m., & ni, j. (2001). the effects of thermal distortions on the diameter and cylindricity of dry drilled holes. machine tools and manufacture, 41(15), 2261–2270. https://doi.org/10.1016/s0890-6955(01)00047-5 4. kaplan, y., motorcu, a. r., nalbant, m., & okay, ş. (2015). the effects of process parameters on acceleration amplitude in the drilling of cold work tool steels. advanced manufacturing technology, 80(5–8), 1387–1401. https://doi.org/10.1007/s00170-015-7097-z 5. khan, s. a., nazir, a., mughal, m. p., saleem, m. q., hussain, a., & ghulam, z. (2017). deep hole drilling of aisi 1045 via high-speed steel twist drills: evaluation of tool wear and hole quality. international advanced manufacturing technology, 93(1–4), 1115–1125. https://doi.org/10.1007/s00170-017-0587-4 6. li, r., hegde, p., & shih, a. j. (2007). high-throughput drilling of titanium alloys. machine tools and manufacture, 47(1), 63–74. https://doi.org/10.1016/j.ijmachtools.2006.02.012 7. rahim, e. a., & sharif, s. (2006). investigation of tool life and surface integrity when drilling ti-6a1-4v and ti5a1-4v-mo/fe. jsme series c: mechanical systems, machine elements and manufacturing, 49(2), 340–345. https://doi.org/10.1299/jsmec.49.340 8. ramulu, m., branson, t., & kim, d. (2001). a study on the drilling of composite and titanium stacks. composite structures, 54(1), 67–77. https://doi.org/10.1016/s0263-8223(01)00071-x 9. zhang, p. f., churi, n. j., pei, z. j., & treadwell, c. (2008). mechanical drilling processes for titanium alloys: a literature review. in machining science and technology (vol. 12, issue 4, pp. 417–444). https://doi.org/10.1080/10910340802519379 10. sivalingam, v., zan, z., sun, j., selvam, b., gupta, m. k., jamil, m., & mia, m. (2020). wear behaviour of whisker-reinforced ceramic tools in the turning of inconel 718 assisted by an atomized spray of solid lubricants. tribology international, 106235. https://doi.org/10.1016/j.triboint.2020.106235 11. minh duc, t., the long, t., & van thanh, d. (2020). evaluation of minimum quantity lubrication and minimum quantity cooling lubrication performance in hard drilling of hardox 500 steel using al2o3 nanofluid. advances in mechanical engineering, 12(2), 1–12. https://doi.org/10.1177/1687814019888404 12. okafor, a. c., & nwoguh, t. o. (2020). a study of viscosity and thermal conductivity of vegetable oils as base cutting fluids for minimum quantity lubrication machining of difficult-to-cut metals. advanced manufacturing technology, 106(3–4), 1121–1131. https://doi.org/10.1007/s00170-019-04611-3 13. braga, d. u., diniz, a. e., miranda, g. w. a., & coppini, n. l. (2002). using a minimum quantity of lubricant (mql) and a diamond coated tool in the drilling of aluminum-silicon alloys. materials processing technology, 122(1), 127–138. https://doi.org/10.1016/s0924-0136(01)01249-3. 14. stephenson, d. a., and agapiou, j. s. (2016). metal cutting theory and practice. 3rd ed., chapter 15, boca raton, fl: crc press. 15. khan, w. a., hoang, n. m., tai, b., & hung, w. n. p. (2018). through-tool minimum quantity lubrication and effect on machinability. manufacturing processes, 34(march), 750–757. https://doi.org/10.1016/j.jmapro.2018.03.047 16. kao, y. t., takabi, b., hu, m., & tai, b. l. (2017). coolant channel and flow characteristics of mql drill bits: experimental and numerical analyses. asme 2017 12th international manufacturing science and engineering patil et al., (2020): international journal of engineering materials and manufacture, 5(4), 98-115 115 conference, msec 2017 collocated with the jsme/asme 2017 6th international conference on materials and processing, 2, 1–7. https://doi.org/10.1115/msec2017-3060 17. raval, j. k., kao, y.-t., & tai, b. l. (2019). characterizing mist distribution in through tool minimum quantity lubrication (mql) drills. manufacturing science and engineering, 1–16. https://doi.org/10.1115/1.4045799 18. raval j.k., hung w.n.p., and tai b.l, (2019). multiphase flow distribution in mql drilling using optical intensity distribution-based approach, msec2019-2926, asme 14 th . 19. hughey, e., and stephenson, d. (2019). oil delivery balancing and priming for multi-diameter minimum quantity lubrication tooling assemblies. 47th sme north american manufacturing research conference, procedia manufacturing, 34: 343-348. 20. fachausschuss information sheet no. 006. (2005). low-emitting metal working with minimum quantity lubrication. 21. li, q., lerma, i., alvarado, j., edinbarough, i., & hung, w. n. p. (2015). characterization of micromist for effective machining. asme international mechanical engineering congress and exposition, proceedings (imece), 2a-2015. https://doi.org/10.1115/imece2015-53632 22. tai, b. l., dasch, j. m., & shih, a. j. (2011). evaluation and comparison of lubricant properties in minimum quantity lubrication machining. machining science and technology, 15(4), 376–391. https://doi.org/10.1080/10910344.2011.620910 23. dynacast. (n.d.). https://www.dynacast.com/en/knowledge-center/material-information/die-castmetals/aluminum-die-casting-metals/aluminum-alloy-a380 24. star su llc. (n.d.). https://www.star-su.com/cutting-tools/gundrills/solid-carbide-twist-drills/ 25. sharon-cutwell co. inc. (n.d.). https://cutwell.com/ 26. kajaria s., (2009). modeling of tool life and micro-mist flow for effective micro-machining of 316l stainless steel. thesis, texas a&m university, pp 115-119. 27. stephenson, d., hughey, e., and hasham, a.a. (2019). air flow and chip removal in minimum quantity lubrication drilling. 47th sme north american manufacturing research conference, procedia manufacturing, 34: 335-342. 28. liu, z. q., cai, x. j., chen, m., & an, q. l. (2012). selection of minimum quantity lubrication (mql) parameters in milling of ti-6al-4v. advanced materials research, 426, 139–142. https://doi.org/10.4028/www.scientific.net/amr.426.139 29. james, g., witten, d., hastie, t., & tibshirani, r. (2017). an introduction to statistical learning: with applications in r. chapter 10, new york: springer. https://doi.org/10.1007/978-1-4614-7138-7 30. marutho, d., hendra handaka, s., wijaya, e., & muljono. (2018). the determination of cluster number at kmean using elbow method and purity evaluation on headline news. proceedings 2018 international seminar on application for technology of information and communication: creative technology for human life, isemantic 2018, 533–538. https://doi.org/10.1109/isemantic.2018.8549751 31. k-means cluster analysis, https://uc-r.github.io/kmeans_clustering#elbow, access 2 june 2020. 32. park, k.h., olortegui-yume, j., yoon, m.c., and kwon, p. (2010). a study on droplets and their distribution for minimum quantity lubrication (mql), machine tools & manufacture, 50:824-833. 33. tai, b. l., jessop, a. j., stephenson, d. a., & shih, a. j. (2012). workpiece thermal distortion in minimum quantity lubrication deep hole drilling-finite element modelling and experimental validation. manufacturing science and engineering, transactions of the asme, 134(1). https://doi.org/10.1115/1.4005432. 34. wang, z., kovvuri, v., araujo, a., bacci, m., hung, w. n. p., & bukkapatnam, s. t. s. (2016). built-up-edge effects on surface deterioration in micromilling processes. manufacturing processes, 24, 321–327. https://doi.org/10.1016/j.jmapro.2016.03.016. 35. kovvuri, v., wang, z., araujo, a., da silva, m. b., bukkapatnam, s., & hung, w. n. p. (2015). built-up-edge formation in micromilling. https://asmedigitalcollection.asme.org/imece/proceedingspdf/imece2015/57359/v02at02a057/2492078/v02at02a057-imece2015-53390.pdf 36. barnes, s., & pashby, i. r. (2000). through-tool coolant drilling of aluminum/sic metal matrix composite. engineering materials and technology, transactions of the asme, 122(4), 384–388. https://doi.org/10.1115/1.1288925. international journal of engineering materials and manufacture (2021) 6(2) 81-94 https://doi.org/10.26776/ijemm.06.02.2021.01 jungko moni chakma and mohammad zoynal abedin department of mechanical engineering dhaka university of engineering and technology gazipur 1707, bangladesh e-mail: abedin.mzoynal@duet.ac.bd reference: j. m. chakma and m. z. abedin (2021). review on heat transfer enhancement by rectangular fin. international journal of engineering materials and manufacture, 6(2), 81-94. review on heat transfer enhancement by rectangular fin jungko moni chakma and mohammad zoynal abedin abstract heat generation of engineering appliances has bad effect in handling the system can cause the trouble, short life cycle of machines, frequent maintenance requirements and low reliability of systems. the passive cooling technique has been widely used to solve such problems. this review work summarizes the heat transfer enhancement technique in a rectangular fin with economic way. so many research about the enhancement of heat transfer by rectangular fins experimentally and numerically and found very significant result. in this review, various types of rectangular fin structures are studied simultaneously. it is revealed through reviewing the related literature that the highest value of equivalent heat transfer enhancement is found the increase in average heat transfer performance of inverted triangular notched fin 50.51% as compared with plane rectangular fin and the perforated fin total heat transfer rate increased by 38.9% compared to regular fin. furthermore, by reduction of the optimal fin spacing, heat flux can be changed by 20% in standard rectangular fin when compared with regular fin spacing. also cooling performance of the inclined rectangular fin with 60° of tilt angle is seen to be as 6% higher than solid rectangular fin. this article can be considered as a benchmark in the practical application for enhances the heat transfer rates. keywords: heat transfer enhancement, rectangular fin, active method, various fin, passive method, fin geometry. 1 introduction heat generation of engineering appliances has bad effect in handling the system can cause the trouble, short life cycle of machines, frequent maintenance requirements and low reliability of systems. there are two methods are used to minimize the overheating problems. these are active and passive methods. in active methods, to maintain the enhancement mechanism of heat transfer external power is required. in passive methods, surface modification or geometrical shape changes are mostly performed in the existing material or additional devices like rough surface or extended surface are added in the system. in passive methods heat transfer rate is often increased by providing extended surfaces which increases the effective heat transfer area. this is done by adding fins, pins, or other extensions to the heat transferring surface. these methods have so many advantages than active methods so that it is preferred for widely used. as these have many advantages the fin arrays are commonly used in heat exchangers, air conditioning, chemical reactor and refrigeration systems and other application areas that require high heat flux removal rates [1, 2]. basic methods of the heat transfer are conduction, convection and radiation. convection is a widely used cooling technique. three types of convection and these are natural, forced and mixed convection [3]. several types of the rectangular fins, which are used to increase heat transfer in the literature, are given in figure 1 [4]. the parameters should optimize to enhance the heat transfer rate, these parameters are fin diameter, fin shape, fin height and inter fin distance. the present study investigated the heat transfer enhancement in various arrangements of several types of rectangular fin by using passive heat transfer technique and their impacts on different mediums and configurations. heat dissipation of parallel plates has been presented by elenbaas [5]. in 1963, starner and mcmanus [6] were carried out an experimental study with four sets of rectangular fins. number of fins in the array was changed between fourteen and seventeen and fin height and spacing was altered and found that space and height of the fin has a direct impact on heat transfer performance, and it was also insufficient number of fins to the surface provides lower heat transfer rates. it is also revealed that to reach maximum heat transfer rates, narrow fin spacing should be provided in the surface. an experimental investigation of free-convection heat transfer from rectangular-fin arrays was investigated by welling and wooldridge [7]. received: 12 december 2020 accepted: 15 march 2021 published: 15 april 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 mailto:abedin.mzoynal@duet.ac.bd chakma and abedin (2021): international journal of engineering materials and manufacture, 6(2), 81-94 82 figure 1. different rectangular fin types and schematic view of the fin arrays [4] 2 studies on standard rectangular fins the heat transfer enhancement of rectangular fin depends on fin geometry [3]. it has been concluded that heat transfer coefficients fell 10 to 30% below compared with parallel plates. it was also the arrays with 45 0 yielded results 5 to 20% below those of the vertical. a study on to see the effect on flow field of rectangular fin experimentally was performed by harahap and mcmanus [8]. chimney type flow pattern is observed for all of the cases and the researchers suggest choosing proper ratio of fin height to fin height to avoid sliding chimney strip flow. some experimental results on rectangular fin array arrangement optimization were presented by jones and smith [9]. in this research average heat transfer coefficients and spacing effects are reported in [5] and [7] in agreement with the found data from the experiment. it is also the correlation that was obtained by harahap and mcmanus [8], were compared with found data. data correlations suggest that, correlation parameters of ref [8] are debatable. leung et al. [10] compared the heat transfer characteristics of vertical and horizontal fin array. an experimental investigation to see the effect of increasing the fin length to the heat loss was performed by leung et al. [11]. in this research it was found that increase of the fin length and small fin separation distance causes large reduction in the heat loss. leung and probert [12, 13], conducted an experiment vertical and horizontal rectangular fin arrays. in these research it is concluded that when fin thickness is reduced, number of fins is increased at same base area condition so that heat transfer area is also increased. due to this confliction situation, authors claimed that there should be a critical fin thickness, which corresponds to a maximum heat transfer rate. bar and cohen [14, 15] predicted this critical value theoretically for free convection conditions. vertically and horizontally based non dimensional correlations are generated for vertical-finned systems [16-18]. the heat dissipation rate on steady state condition of stainless-steel, vertical rectangular fins, under natural-convection have been measured experimentally by ko et al. [19]. in this experiment two materials (duralumin and stainless steel) are used. results suggest that the duralumin fin array have higher heat transfer performance than stainless-steel fin arrays with similar geometries. babus’haget al. [20]. figure 2. (a) geometrical fin parameters (b) continuous and interrupted rectangular fin [3] standard rectangular fins inclined rectangular fins perforated rectangular fins interrupted rectangular fins rectangular fins review on heat transfer enhancement by rectangular fin 83 observed that a little effect had on heat transfer performance of fins material thermal conductivity. also, confirmed that fin material has no effect on fin spacing. fin geometry roles and base-to-ambient temperature difference on heat transfer performance of rectangular fin were investigated by yazicioglu and yüncü [21, 22]. it was concluded that the rectangular fin heat transfer performance depends on difference of base-to-ambient temperature and fin geometry. it was also convective maximum value of heat transfer rate from fin arrays as a function of fin geometry and a correlation of maximum heat transfer and fin spacing was developed. dogan and sivrioglu [23, 24] were concluded that the optimum transfer yields on the optimum fin spacing and value depends on fin height and modified rayleigh number. from numerical and experimental study hong and chung [25] it is observed that there is an optimal fin spacing range and when the optimal fin spacing increased then the prandtl number decreased. ayli et al. [26] showed that the turbulent fully developed flow and a correlation was developed and compared with experimental results. sana and sukhatme [27] analyzed the single chimney flow patterns of rectangular fin array and obtained an agreement with the experimental data. vollara et al [28] was concluded that the heat flux can be changed of 20% by reduction of the optimal fin spacing. arquis and rady [29] found high fin height, wide fin spacing make the finned surface more effective and when low rayleigh number, high fin height then linearly increases effectiveness. a theoretical investigation of the fin geometry and temperature difference between fin and surroundings was carried out by bakaya et al [30] and concluded that the optimum value in terms of overall heat transfer cannot be obtained. a numerical study of natural convection of air in a differentially heated horizontal rectangular enclosure with finned base plate, the variation of average with rayleigh number, for different fin length and spacing was investigated by pathak et al. [31]. it was observed that the heat transfer performance increases with increasing the number of fins, nusselt number and rayleigh. an experimental investigation to observe the heat transfer enhancement in duct with rectangular fin arrays was performed by islam and barsoum [32]. the researchers identified a promising configuration and expected the improved heat transfer performance from the end wall and the fin surface. partner and raseelo [33] showed that when increasing some parameters of fin then the heat rapidly dissipates to the ambient temperature. osman et al [34] results showed that extension of surface of fin geometries, enhanced the heat transfer coefficient, but this thing depends on the reynolds number of both fluids. 3 studies on interrupted rectangular fins in this part of the research, several researches about natural and forced convection heat transfer from interrupted vertical and horizontal rectangular fins are summarized. in continuous fin surfaces, rate of heat transfer decreases as flow becomes fully developed after critical length. on the other hand, interrupted fins disturb the thermal boundary layer and reset the boundary layer growth in each fin leading edge corner by this way a thermally developing flow regime is maintained which leads to higher heat transfer coefficients. also using interrupted fins provides lower weight and provides cost reduction to the manufacturers. a model to observe the thermal performance of rectangular heat sinks using at plate boundary layer was presented by culham, j et al. [35]. the researchers obtained an excellent agreement in comparisons between experimental data, the analytical cuboid and heat sink models of yovanovich and the conjugate model. an experimental investigation of rectangular fin mounted on a vertical base under natural convection heat was carried out by yuncu and anbar [36]. the results showed that the optimum value for the fin spacing maximized the heat transfer performance of fin array. interrupted fins are made by creating slots on solid continuous fins also interrupted fin provide lower weight and provides low cost to the manufacturers [37]. (a) (b) (c) figure 3: effect of fin length on nusselt number for different fin spacing: (a) s/h = 0.875; (b) s/h = 1.17; (c) s/h = 1.75 [31] chakma and abedin (2021): international journal of engineering materials and manufacture, 6(2), 81-94 84 ahmedi et al [38] was proposed a new compact correlation for calculating the optimum interruption length. kharce and farkade [39] concluded that the heat transfer rate in notched fins is more than the un-notched fins. it was also the copper gives more heat transfer rate than aluminum plate. in addition, as the notch area of fin increases the heat transfer rate also increases and the copper plate gives better heat transfer rate than aluminum plate. wange and metkar [40] were concluded that the heat transfer coefficient is more in notch fin array than without notch fin array. it was also appropriate selection fin geometry and depth of notch is needed for achieving superior heat transfer rate of fin. an experimental investigation to observe the effect of notch in the heat transfer performance was carried out by dixit and mishra [41]. it was found that when notch depth increases then heat transfer coefficient also increases. shehab [42] concluded that the convective heat transfer coefficient of notched fin array is 28% to 45% higher than un-notched fins at the same conditions. it was also found that average nusselt number is about 45% higher in case of 37% notched fins array than un-notched fins array. experimental investigations to observe the effect of different notch sizes on heat transfer coefficient was carried out by bakale et al. [43]. the study showed that as the notch size increases so does the heat transfer rate. singh and singh [44] studied on steady state heat transfer for notched fins for different heat inputs and different notch geometries. it was concluded that the inverted triangular notched fin, inverted trapezoidal notched fin, inverted circular notched fin and inverted rectangular notched fin average heat transfer coefficient performance increases fin are 50.51%, 36.81%, 37.98% and 26,01% respectively as compared with plane rectangular fin. kallanavar and kapale [45] concluded the heat transfer coefficient increases with increase in fin spacing. taji et al. [46] commented that rectangular notched fin arrays provide high heat transfer rate compared with triangular and semicircular notched structures. what’s more, it was revealing that with raising the fin spacing; heat transfer coefficient reaches an optimum value. after reaching the critical value, heat transfer starts to drop. an experimental investigation to observe the heat transfer coefficient of fin with different rectangular notch size for cylinder fins was investigated by beldar [47]. it was observed when notch percentage increasing then heat transfer coefficient and nusselt number also increases. figure 4: graphical presentation of effect of interruption length on the nusselt number for natural convection heat transfer from the fins, (numerical results), a) fin length l =12.5 mm, b) fin length l = 2.5 mm [38] figure 5: graphical representation of comparison of heat transfer coefficient for without notch and notch fins [39] review on heat transfer enhancement by rectangular fin 85 table 1: heat transfer coefficient for without notched and notched fins [40] # heat input in watt h for without notched fin (w/m 2 k) h for 20% notched fin (w/m 2 k) 1 50 8.0595 9.3397 2 60 8.2307 9.6269 3 70 8.5519 10.0100 4 80 8.7130 10.2790 avg 8.3887 9.8139 figure 6: heat transfer coefficient for fin arrays [40] 4 studies on perforated rectangular fins to improve ventilation and to create more turbulence in the fin array holes, cavities, grooves which are generally circular are introduced to the fin surface. essa et al. [48, 49] studied numerically to observe the heat transfer enhancement of a horizontal rectangular fin embedded with triangular perforations under natural convection. the first study [48] showed that perforated heat dissipation of perforated fin was improved of over the equivalent solid fin. furthermore, increasing the thermal conductivity of fin and its thickness as heat transfer also enhanced. second study [49] concluded that dimensions, the perforated fin enhance the heat transfer for certain values of triangular dimensions. it was also observed that the extension of heat dissipation rate of perforated fin was a complicated function of the perforation geometry. modeling natural on convection heat transfer from perforated plates was performed by zan et al. [50]. the researchers concluded that perforations can enhance heat transfer for isolated isothermal plate, vertical parallel plates with low h/s ratios, and vertical rectangular fins with specified dimensions. the researchers [51] showed the heat transfer power of heat sink increases by 16.7% compared with the prototype. furthermore, the heat transfer power of heat sink increases with the increasing number of holes and when the holes reach to a value, further increasing will not function properly. the perforated rectangular blocks heat transfer enhancement in a channel flow was studied by sara et al [52]. it was found that to achieve energy gains up to 40% by perforations opened in the blocks. the solid and circular perforations along the length of the rectangular fins array turbulent heat transfer performance was experimentally investigate by ehteshum et al. [53]. the perforated rectangular fin arrays heat transfer enhancement with different inclinations on natural convection experimentally investigated by awasarmol and pise [54]. it was concluded that the perforated fin heat transfer coefficient increases by 32% at the angle of orientation 45° as compared to the solid fin array and material saving by mass of nearly 30%. sahin and demir [55] experimental results showed that heat transfer performance can enhance by using the square pin fins. a research to investigate the heat transfer enhancement of a vertical rectangular fin embedded with circular perforations was carried out by muthuraja et al. [56]. the design and analysis of perforated rectangular fin array with varying percentage of perforation experimentally investigated by patil et al. [57]. analysis gives the idea about heat transfer and behavior of perforated fins. a research paper on effect of perforation area on temperature distribution of the rectangular fin under natural convection was studied by ibrahim et al. [58]. the experimental results [59] showed that square fins provide higher nusselt number when compared to circular perforated fins. prasad et al. [60] observed that the fin porosity can play a vital role to enhance the heat transfer. with increase in the number of perforations up to certain level the heat dissipation rate is increased in the range of 20% to 70%. chakma and abedin (2021): international journal of engineering materials and manufacture, 6(2), 81-94 86 figure7: 3d image of aluminium cylinder and perporated fin [60] figure 8: effect of perforation no. on heat transfer front the fin tip at varying voltage and effect of length on temperature distribution for varying perforations at constant voltage (220v) [60] huang et al. [61] has found that the perforated fin heat transfer coefficients better than without perforations. bassam and abu [62, 63] showed that the permeable fins compared to the solid fin with similar configuration can provide much higher heat transfer rate. [64] results showed that the circular perforations fins reduced pressure drop and have remarkable heat transfer enhancement. jonsson and moshfegh [65] found that the fin geometry, duct geometry, fin-to-fin distance and the nusselt number influenced the heat transfer rate. shaeri and yaghoubi [66] showed that performances and effectiveness of perforated fins increased with increasing number of perforations. represent numerical data is compared with the numerical and experimental results of ref [67] for solid fin structure. shaeri and jen [68] experimentally and numerically investigated the laminar flow from the leading edge of a flat and found data indicate that the boundary layer thickness and nature or blockage ratio had a strong influence on the structure of the laminar junction flow. a numerical study to investigate the turbulent convection heat transfer on a rectangular plate mounted over a flat surface had been performed by ismail et al. [69]. heat transfer analysis of lateral perforated fin heat sinks had been studied by shaeri et al. [70]. results showed that higher heat transfer performance provides the perforated fins in comparison with solid fins. vyas et al. [71] concluded heat transfer rate is high for rectangular shape of perforation decreasing with elliptical and circular shape. it shows that shapes with lower eccentricity have good heat removal capacity. so, eccentricity as low as possible should be manufactured when perforated fin are manufactured. it is also heat transfer from first some fins are high as compared to later fins. so increasing the number of fins in lateral direction had no effect on heat transfer rate especially when space and weight are constraints. ziaoqin et al [72] concluded that the total heat transfer rate of tube heat exchanger of perforated fin under the frosting condition is increased by 38.9% and the heat transfer coefficient 31.8%. aluminium cylinder perporated fin https://www.sciencedirect.com/topics/engineering/convection-heat-transfer https://www.sciencedirect.com/topics/engineering/convection-heat-transfer https://www.sciencedirect.com/topics/engineering/rectangular-plate review on heat transfer enhancement by rectangular fin 87 table 2: values of average heat transfer coefficient (hav) and nusselt number (nu) for different cases [71] geometry of perforation temperature difference (tout-tin) reynolds number (re) average heat transfer coefficient (hav) nusselt number (nu) rectangular 6.05194 2000 18.93 55.448 5.51926 4000 18.96 55.536 5.33691 6000 18.9803 55.595 elliptical 5.63324 2000 18.9601 55.536 5.31223 4000 18.9820 55.600 5.20923 6000 18.9890 55.621 circular 5.61295 2000 18.9615 55.540 5.30365 4000 18.9825 55.602 5.20309 6000 18.9894 55.622 figure 9: temperature distribution at outlet for rectangular shape and elliptical shape [71] figure 10: temperature distribution at outlet for circular shape [71] 5 studies on inclined rectangular fins due to the rotation of some devices or lack of available place in some scenarios, inclined oriented heat sink becomes compulsory to use instead of vertical or horizontal orientations. these possible scenarios motive the studies, which define an inclination to the finned surface. this part of the survey indicates that few studies are available on inclined fin arrays. heat transfer from a plate with arbitrary inclination under natural convection was experimentally studied by fujii and imura [73]. it was concluded that nusselt number was proportional to one-fifth power of ra number and slightly inclined heated plate and horizontal heated plate both facing downwards. it was also when larger the inclination of angle of fins then the inclined heated plate facing upwards. mittelman et al [74] showed that the heat transfer rate substantially enhanced when the fin array tilting beyond a certain angle. additionally, it was showed that the inclination angle did not depend on fin spacing and the researcher’s advice to create inclination greater than 10° in order to enhance heat transfer rates. an experimental investigation to observe heat flux under the natural convection heat transfer from rectangular fins with five different figures was carried out by khudheyer and hasan [75]. the researchers had been found the cfd and experimental results and a good agreement between both. it was also found empirical correlations for the average rayleigh number overall nusselt number versus overall nusselt number. an experimental investigation to investigate the effect of inclination of the fin array on heat transfer rate chakma and abedin (2021): international journal of engineering materials and manufacture, 6(2), 81-94 88 was performed by naidu et al [76]. it was found that a satisfactory agreement from the experimental data. rocha and ganzarolli [77] investigation showed the nusselt number can be evaluated by using a single correlation. it was also proposed a correlation for the local nusselt number for natural convection heat transfer. a research to observe the cooling performance of electronic devices using the horizontal tubes with tilted rectangular fins was carried out by lee et al. [78]. the researchers concluded that the inclined rectangular fin cooling performance with 60° of tilt angle is 6% higher than solid rectangular fins. in addition, the optimal cooling performance of the tilted finned tube is 9.2 times greater than that of the tube without fins. therefore, tilted rectangular fins may potentially be used for the cooling of various electronic devices. degao et al [79] observed that the inclination of vertical cross section rectangular fin does not reduce the convection heat transfer rate. figure 11: effect of inclination on convection heat transfer rate from a fin array [76] figure 12: comparison of the optimal cooling performances [78]. review on heat transfer enhancement by rectangular fin 89 6 summary heat transfer enhancement through various types of rectangular fin. fin type author type of investigation investigated properties observations standard rectangular fin starner and mcmanus [6] experimental fin spacing & fin height 1. fin height and fin spacing has a direct impact on heat transfer rates. 2. heat transfer rates become lower when compared to cases without a fin by insufficient applications of fins. 3. narrow fin spacing can enhance heat transfer coefficient. ko et al. [19] experimental fin material duralumin & stainless steel the duralumin fin arrays provide higher heat transfer performance than stainless steel fin array with similar geometries. babus’haget al. [20] experimental fin material the heat transfer rate had a small effect on thermal conductivity of the material. yazicioglu and yüncü[21] experimental fin length& fin height& fin spacing correlation is obtained for maximum heat transfer rate. dogan and sivrioglu[23] experimental fin spacing & fin height 1. to maximize heat transfer rate, fin spacing should be optimized. 2. up to the critical fin spacing value, heat transfer coefficient rises and then it decreases with the increase of fin spacing. dogan and sivrioglu[24] experimental fin spacing & fin height the correlations of nusselt number i.e., heat transfer rate is obtained. vollara et al [28] experimental fin surface by reduction of the optimal fin spacing, heat flux can be changed by 20%. pathak et. al. [31] numerical fin spacing & fin height nusselt number, fin thickness and fin height relationship is defined. osman et al [34]. experimental fin geometries by using different fin geometries with extending the surface enhanced the heat transfer coefficient. interrupted rectangular fin ahmadi et al. [38] experimental & numerical fin interruption length the correlation of heat transfer rate is obtained for fin interruption length. kharce and farkade [39] experimental fin material & notch effect 1. interrupted fins provide higher heat transfer rates. 2. heat transfer rate increases when aluminum plate is used instead of copper. 3. heat transfer coefficient rises at a level of 20% by using notch in the fin shehab [42] experimental fin spacing& fin number 1. heat transfer coefficient is higher in notched one when it is compared with un-notched. 2. when the removal area of the fin increases, the average heat transfer coefficient also rises and an increase in heat input causes a peak in the heat transfer coefficient. chakma and abedin (2021): international journal of engineering materials and manufacture, 6(2), 81-94 90 3. rising the fin spacing causes more fresh air entrance between the fins; therefore, heat transfer rate goes up. bakale [43] experimental notch length & notch material 1. heat transfer coefficient has direct proportion with the notch size. 2. the researchers reveal that a copper plate gives a better heat transfer rate than an aluminum one. singh and singh[44] numerical & experimental heat load & notch geometry 1. rectangular notched fins provide higher heat transfer rates. 2. the increase in average heat transfer performance of inverted triangular notched fin 50.51% as compared with plane rectangular fin. beldar [47] experimental notch geometry increasing notch percentage also increases heat transfer coefficient and nusselt number. perforated rectangular fin zan et al. [50] experimental perforation geometry the heat transfer rate increasing when perforations in the fin surface decrease the weight of the fin. meng et al. [51] experimental perforation geometry the heat transfer rate is 16.7 % increased with introducing the circular holes. awasarmol and pise [54]. experimental perforation geometry & holes are drilled 4 to 12 mm perforation fin with 12 mm hole and 45° angle of orientation creates 31% enhanced heat transfer while decreasing material weight by 30%. dhanawade et al. [59] numerical & experimental perforation geometry results square fins provide higher nusselt number when compared to circular perforated fins. prasad et al. [60] experimental perforation geometry with increase in the number of perforations up to certain level the heat dissipation rate is increased in the range of 20% to 70%. ismail et. al. [64] numerical fin and perforation length solid fins have higher nusselt number distribution than perforated ones. jonsson and moshfegh [65]. numerical & experimental perforation geometry solid fins have higher nusselt number than square and circular perforated fins and also solid fins have higher thermal resistances compared with the perforated fins. vyas et al. [71] numerical shape of perforation rectangular perforated fin arrays provide higher nusselt number distribution. ziaoqin et al [72] experimental fin tube heat exchanger the perforated fin total heat transfer rate increased by 38.9% and the heat transfer coefficient increased by 31.8%. inclined rectangular fin mittelman[74] numerical & experimental 0° to 30° inclination angle 1. higher heat transfer performance can achieve flow separation as compared with no flow separation along the fin array cases. 2. author’s advice to define inclination angle higher than 10° to enhance heat transfer rate. review on heat transfer enhancement by rectangular fin 91 khudheyer and hasan [75] numerical & experimental rectangular fins with 1,4 interruptions, inclination and v-fins interrupted fin surfaces have higher heat transfer coefficient than inclined fins. naidu et al [76] experimental inclinations (0°,30°,45°,60° and 90°) convective heat transfer rate increases with the rise of the inclination angle for the tested range. lee et al [78] numerical & experimental 30°,60° 90° inclination angle, number of fins the inclined rectangular fin cooling performance with 60° of tilt angle is 6% higher than solid rectangular fins. degao et al [79] numerical vertical and inclined plate the inclination does not reduce the convection heat transfer rate. it is revealed through reviewing the related literature that the highest value of equivalent heat transfer enhancement is found that the increase in average heat transfer performance of inverted triangular notched fin, inverted trapezoidal notched fin, inverted circular notched fin and inverted rectangular notched fin are 50.51%, 36.81%, 37.98% and 26, 01% respectively as compared with plane rectangular fin. the perforated fin total heat transfer rate increased by 38.9% and the heat transfer coefficient increased by 31.8% as compared with regular fin and introducing circular holes in perforated fin an enhancement of 16.7% in the heat transfer rate. also heat dissipation rate was increased in the range of 20% to 70% with increase in the number of perforations (24 to 60) up to certain level. furthermore, by reduction of the optimal fin spacing, heat flux can be changed by 20% in standard rectangular fin when compared with regular fin spacing. also cooling performance of the inclined rectangular fin with 60° of tilt angle is seen to be as 6% higher than solid rectangular fins. 7 conclusions this paper summarizes the literature review about rectangular fin structures which is one of the passive heat transfer enhancement techniques with low costs and high efficiency. the observations from many researchers can be summarized as given below: 1) in the standard rectangular fin, fin height and fin spacing has a direct impact on heat transfer rates. heat transfer rates become lower when compared to cases without a fin by insufficient applications of fins, narrow fin spacing can enhance heat transfer coefficient. the duralumin fin arrays provide higher heat transfer performance than stainless steel fin array with similar geometries. the heat transfer rate had a small effect on thermal conductivity of the material. also, to maximize heat transfer rate, fin spacing should be optimized. up to the critical fin spacing value, heat transfer coefficient rises and then it decreases with the increase of fin spacing. furthermore, by reduction of the optimal fin spacing, heat flux can be changed by 20%. 2) in the interrupted rectangular fin, interrupted fins provide higher heat transfer rates. the heat transfer rate increases when aluminum plate is used instead of copper. performed with notch and without notch fins it was seen that heat transfer coefficient raises at a level of 20%. the rectangular notched fins provide higher heat transfer rates than other investigated notch geometries. the increase in average heat transfers performance of inverted triangular notched fin 50.51% as compared with plane rectangular fin. 3) in the perforated rectangular fin, the heat transfer rate increasing when perforations in the fin surface decrease the weight of the fin. the circular holes provide an enhancement of 16.7% in the heat transfer rate. the perforated fin with 12 mm hole and 45° angle of orientation creates 31% enhanced heat transfer while decreasing material weight by 30%. the perforated fin total heat transfers rate increased by 38.9% and the heat transfer coefficient increased by 31.8%. 4) in the inclined rectangular fin, higher heat transfer performance can achieve flow separation as compared with no flow separation along the fin array cases. the interrupted fin surfaces have higher heat transfer coefficient than inclined fins. convective heat transfer rate increases with the rise of the inclination angle for the tested range. the rectangular fin cooling performance with 60° of tilt angle is 6% higher than solid rectangular fins. references [1] liu, s. & sakr, m. (2013). a comprehensive review on passive heat transfer enhancements in pipe exchangers. renewable and sustainable energy reviews, vol. 19, 64-81. chakma and abedin (2021): international journal of engineering materials and manufacture, 6(2), 81-94 92 [2] nagarani, n., mayilsamy, k., murugesan, a. & kumar, g. s. (2014). review of utilization of extended surfaces in heat transfer problems. renewable and sustainable energy reviews, vol. 29, 604-613. [3] mostafavi, g. (2012). natural convection heat transfer from interrupted rectangular fins. msc thesis, sımon fraser university. [4] aylı, e. & i̇nce, e. (2018). review of enhancement of heat transfer from rectangular fin arrays. mugla journal of science and technology, doi: 10.22531/muglajsci.445045. [5] elenbaas, w. (1942). heat dissipation of parallel plates by free convection, physica, 9, 1-28. [6] starner, k. e. & mcmanus, jr.h.n. (1963). an experimental investigation of free convection heat transfer from rectangular fin arrays. journal of heat transfer, series c,85, 273-278. [7] welling, r. j. & wooldridge, c. b. (1965). free convection heat transfer coefficients from rectangular vertical fins, journal of heat transfer, series c, 87, 439-444. [8] harahap, f. & mcmanus, jr. h. n. (1967). natural convection heat transfer from horizontal rectangular fin arrays. transactions of asme, 89, 32-38. [9] jones, c. & smith, l. (1970). optimum arrangement of rectangular fins on horizontal surfaces for free convection heat transfer. transactions of asme, 92, 6-10. [10] leung, c. w., probert, s. d. & shilston, m. j. (1985). heat exchanger design: optimal uniform separation between rectangular fins protruding from a vertical rectangular base. alied energy, 19, 287-299. [11] leung, c. w., probert, s. d & shilston, m. j. (1986). heat transfer performances of vertical rectangular fins protruding from rectangular bases: effect of fin length. allied energy, 22, 313-318. [12] leung, c. w. & probert, s. d. (1987). heat exchanger design: optimal uniform thickness of vertical rectangular fins protruding perpendicularly outwards. at uniform separations, from a vertical rectangular base, allied energy, 26, 111-118. [13] leung, c. w. & probert, s. d. (1988). heat exchanger design: optimal thickness (under natural convection conditions) of vertical rectangular fins protruding upwards from a horizontal rectangular base. allied energy, 29, 299-306. [14] bar-cohen, a. (1977). optimum natural convection cooling of electronic assemblies. american society of mechanical engineers, design engineering conference and show, chicago, ill., 9-12. [15] bar-cohen, a. (1989). fin thickness for an optimized natural convection array of rectangular fins. asme journal of heat transfer, 101, 564-566. [16] leung, c. w. & probert, s. d. (1987). natural convective heat exchanger with vertical rectangular fins and base: design criteria. proc.i.mech.e., 201(5), 365-372. [17] leung, c. w. & probert, s. d. 1989). steady state heat transfers from vertical fins protruding upwards from horizontal bases. j.inst. energy, 62 (451),94-101. [18] leung, c. w. & probert, s. d. (1989). heat-exchanger performance: effect of orientation. alied energy, 33(4), 235-252. [19] ko, y. m., leung, c. w. & probert, s. d. (1989). steady-state free convective cooling of heat exchangers with vertical rectangular fins: effect of fin material. alied energy, 34, 181-191. [20] babus’hag, f. r., probert,f. s. & taylor, r. c. (1993). heat transfer effectiveness’s of shrouded. rectangular fin arrays, alied energy, 46, 99-112. [21] yazicioglu, b. & yüncü, h. (2007). optimum fin spacing of rectangular fins on a vertical base in free convection heat transfer. heat and mass transfer, 44, 11-21. [22] yüncü, h. & güvenc, a. (2001). an experimental investigation on performance of rectangular fins on a vertical base in free convection heat transfer. heat and mass transfer, 37, 409-416. [23] dogan, m. & sivrioglu, m. (2009). experimental investigation of mixed convection heat transfer from longitudinal fins in a horizontal rectangular channel: in natural convection dominated flow regimes. energy conversion and management, 50, 2513-2521. [24] dogan, m. & sivrioglu, m. (2010). experimental investigation of mixed convection heat transfer from longitudinal fins in a horizontal rectangular channel, international journal of heat and mass transfer, 53, 2149-2158. [25] hong, h. h. & chung, b. j. (2016). variations of the optimal fin spacing according to prandtl number in natural convection. international journal of thermal sciences, 101, 1-8. [26] ayli, e., bayer, o. & aradag, s. (2016). experimental investigation and cfd analysis of rectangular profile fins in a square channel for forced convection regimes. international journal of thermal sciences, 109, 279290. [27] sane, n. k. & sukhatme, s. p. (1974). natural convection heat transfer from horizontal rectangular fin arrays. in proc. of 5th international heat transfer conference, tokyo, japan, 3, 114-118. [28] vollara, a. l,. grignaffini, s & gugliermetti, f. (1999). optimum design of vertical rectangular fin arrays. international journal of thermal science, 38, 525-529. [29] arquis, e. & rady, m. (2005). study of natural convection heat transfer in a finned horizontal fluid layer. international journal of thermal sciences, 44, 43-52. [30] baskaya, s., sivrioglu, m. & ozek, m. (2000). parametric study of natural convection heat transfer from horizontal rectangular fin arrays. international journal of thermal science, 39, 797-805. https://www.researchgate.net/deref/http%3a%2f%2fdx.doi.org%2f10.22531%2fmuglajsci.445045?_sg%5b0%5d=oah0dudv0-ijp0twvveihbn7euq_wpcthahhhjghth0oaxyxdyypecmefxy3pzn693mc_x7ng2ynw6oci2yqdk8p7g.sddfimbfc-dtsckqnqxtu00d7xzvh-p2jazhxnitq1vheidwb2oeyzvrzti1pn9rzw6ju4ile2okarfuionz0a review on heat transfer enhancement by rectangular fin 93 [31] pathak, m. k., mer, k. k. s. & pant, p. k. (2013). numerical analysis of natural convection in rectangular enclosure with heated finned base plate. international journal of research in mechanical engineering & technology, 3, 64-67. [32] islam, m. & barsoum, i. (2020). heat transfer enhancement in duct with rectangular fin arrays. gas turbine india conference, gtindia2019-2761, v001t03a019. [33] ndlovu, p. l. & moitsheki, jr. r. (2020). steady state heat transfer analysis in a rectangular moving porous fin. propulsion and power research, vol. 9, (2), 188-196. [34] osama m. a., muhannad, r. a. & basim, h. o. (2020). heat transfer enhancement in a double pipe heat exchanger using different fin geometries in turbulent flow. iranian journal of science and technology, transactions of mechanical engineering. [35] culham, j. r., yovanovich, m. m. & lee, s. (1995). thermal modeling of isothermal cuboids and rectangular heat sinks cooled by natural convection. ieee transaction on components, packaging and manufacturing technology, 18(3), 559-566. [36] yuncu, h. & anbar, g. (1998). an experimental investigation on performance of rectangular fins on a horizontal base in free convection heat transfer. journal of heat and mass transfer, 33 (5-6), 507-514. [37] kapade, t. t. & palande, d. d. (2015). review of natural convective heat transfer from interrupted rectangular fin array. international research journal of engineering and technology, 2(3), 823-829. [38] ahmadi, m., mostofavi, g. & bahrami, m. (2014). natural convection from rectangular interrupted fins. international journal of thermal sciences, 82, 62-71. [39] kharce, s. s. & farkade, s. h. (2012). heat transfer analysis through fin array by using natural convection. international journal of emerging technology and advanced engineering, 2(4), 595-598. [40] wange, s. m. & metkar, r. m. (2013). computational analysis of inverted notched fin arrays dissipating heat by natural convection. international journal of engineering and innovative technology, 2(11), 245249. [41] dixit, s. r. & mishra, d. p. (2014). heat transfer analysis through horizontal rectangular inverted notched fin array using natural convection by experimental method. international journal of scientific & engineering research, 4(7), 948. [42] shebab, s. n. (2017). experimental study of freeconvection from rectangular fins array on a heated horizontal plate with notch effect. alnahrain journal for engineering sciences, 20(1), 140-148. [43] bakale, r., baheti, k., dokade, c. & galande, p. (2016). experimental analysis of natural convection heat transfer from notched fin. imperial journal of interdisciplinary research, 2(6), 1211-1214. [44] singh, b. & singh, s. (2016). a research paper on heat transfer in notch fin and un-notch fin, international journal for research in alied science & engineering technology, 4 (9), 12-19. [45] kallanavar, s. & kapale, u. c. (2016). computational analysis of notched fin array using natural convection. international research journal of engineering technology, 3(5), 741-746. [46] taji, s. g., parishward, g. v. & sane, n. k. (2014). experimental investigation of heat transfer and flow pattern from heated horizontal rectangular fin array under natural convection, international journal of heat and mass transfer, 50, 1005-1015. [47] beldar, k. (2017). analysis of natural convective heat transfer from cylinder having rectangular notched fins. international journal of engineering research & technology, 6(4), 834-838. [48] essa. a. a. & widyan, m. a. (2014). enhancement of natural convection heat transfer from a fin by triangular perforations of bases parallel and towards its tip. allied mathematics & mechanics, 28, 10331044. [49] essa, a. a. & al-odat, m. q. (2009). enhancement of natural convection heat transfer from a fin by triangular perforations of bases parallel and toward its base. the arabian journal for science and engineering, 34 (2b), 531-544. [50] zan, w., lı, w., sun, z. j. & hong, r. h. (2012). modeling natural convection heat transfer from perforated plates. journal of zhejiang universityscience a (allied physics and engineering), 12, 353-360. [51] meng, x. r., ma, x. l., lu, j. f. & wei, x. l. (2011). a study on improving in natural convection heat transfer for heat sink of high-power leds. manufacturing science and technology, icmst, 383-390, 6834-6839. [52] sara, o. n., pekdemir, t., yapici, s. & yılmaz, m. (2011). heat transfer enhancement in a channel flow with perforated rectangular blocks. international journal of heat and fluid flow, vol. 22(5), 509–518. [53] ehteshum, m., ali, m., islam, q. & tabassum, m. (2015). thermal and hydraulic performance analysis of rectangular fin arrays with perforation size and number. procedia engineering, 105, 184-191. [54] awasarmol, u. v. & pise, a. t. (2015). an experimental investigation of natural convection heat transfer enhancement from perforated rectangular fin arrays at different inclinations. experimental thermal and fluid science, 68, 145-154. [55] sahin, b & demir, a. (2008). performance analysis of a heat exchanger having perforated square fins. allied thermal engineering, 28(5-6), 621-632. javascript:; javascript:; https://www.sciencedirect.com/science/article/pii/s2212540x20300171#! https://www.sciencedirect.com/science/article/pii/s2212540x20300171#! https://www.sciencedirect.com/science/journal/2212540x https://www.sciencedirect.com/science/journal/2212540x/9/2 javascript:; javascript:; javascript:; https://link.springer.com/journal/40997 https://link.springer.com/journal/40997 chakma and abedin (2021): international journal of engineering materials and manufacture, 6(2), 81-94 94 [56] muthuraja, c. s., aravindkumar & hanoca, p. (2015). experimental study of the perforated rectangular fins by natural convection. international journal of advanced technology in engineering and science, 3(1), 303-307. [57] patil, m. h., patil, s. v., deore, e. r. & chaudhari, g. a. (2016). design & analysis of perforated rectangular fin array with varying percentage of perforation. international advanced research journal in science, engineering and technology, 3(9), 26-31. [58] ibrahim, t. k., basrawi, f., mohammed, m. n. & ibrahim, h. (2016). effect of perforation area on temperature distribution of the rectangular fins under natural convection. arpn journal of engineering and alied sciences, 11(10), 6371-6375. [59] dhanawade, k. h., sunnapwar, v. k. & dhanawade, s. h. (2014). thermal analysis of square and circular perforated fin arrays by forced convection. international journal of current engineering and technology, 2, 109-114. [60] prasad, l., tewari, s. & kumar, a. (2016). an experimental study of heat transfer enhancement in the perforated rectangular fin, journal of integrated science & technology, vol. 4(1), 5-9. [61] huang, g. j., wong, s. c. & lin, l. p. (2014). enhancement of natural convection heat transfer from horizontal rectangular fin arrays with perforations in fin base. international journal of thermal sciences, 84, 164-174. [62] bassam, a. k. & abu, h. (2013). natural convection heat transfer from a cylinder with high conductivity permeable fins. asme journal of heat transfer, 125(2), 282-288. [63] bassam, a. k. & abu, h. (2003). enhanced forced convection heat transfer from cylinder using permeable fins. asme journal of heat transfer, 125(5), 804-811. [64] ismail, f., reza, o. m., zobaer, m. a. & ali, m. (2013). numerical investigation of turbulent heat convection from solid longitudinally perforated rectangular fins. procedia engineering, 56, 497-502. [65] jonsson, h. & moshfegh, b. (2001). modeling of the thermal and hydraulic performance of plate fin, strip fin. and pin fin heat sinks—influence of flow by pass, ieee transactions on components and packaging technologies, 24, 142–149. [66] shaeri, m. r. & yaghoubi, m. (2009). thermal enhancement from heat sinks by using perforated fins. energy conversion and management, 50(5), 1264-1270. [67] rouvreau, s., david, l., calluaud, d. & joulain, p. (2005). laminar junction flow at low reynolds number: influence of the upstream region on the comparison between experiments and calculations. comptes rendus mécanique, 333(3), 265–272. [68] shaeri, m. r. & jen, t. c. (2012). the effects of perforation sizes on laminar heat transfer characteristics of an array of perforated fins. energy conversion and management, 64, 328-334. [69] ismail, f., hasan, m. n. & saha, s. c. (2014). numerical study of turbulent fluid flow and heat transfer in lateral perforated extended surfaces. energy, 64, 632-639 [70] shaeri, m. r., yaghoubi, m. & jafarpur, k. (2009). heat transfer analysis of lateral perforated fin heat sinks. alied energy, 86(10), 2019-2029. [71] vyas, a., gupta, s. & gupta, s. (2016). determining relation among shape of perforation and convective heat transfer from lateral fin arrangement using simulation by computational fluid dynamics. international refereed journal of engineering and science (irjes),5, 24-31. [72] xiaoqin, l., jianlin, y. & yan, g. (2020). an experimental study on the air side heat transfer performance of the perforated fin-tube heat exchangers under the frosting conditions. applied thermal engineering,166, 114-634. [73] fujii, t. & imura, h.(1972). natural-convection heat transfers from a plate with arbitrary inclination. international journal of heat and mass transfer, 15 (4), 755-764. [74] mittelman, g., dayan, a., turjeman, k. d. & ullmann, a. (2007). laminar free convection underneath a downward facing inclined hot fin array. international journal of heat and mass transfer, 50(13-14), 25822589. [75] khudheyer, a. f. & hasan, z. h. (2015). effect of the fin’s configuration on natural convection heat transfer experimentally and numerically. international journal of energy and environment, 6(6), 607-628. [76] naidu, s. v., shorma,k. v., rao, b. g., sombabu, a. & sreenivasulu, b. (2010). natural convection heat transfer from fin arraysexperimental and theoretical study on effect of inclination of base on heat transfer. journal of engineering and alied sciences, 5(9), 7-15. [77] rocha, a. d. & ganzarolli, m. m. (2005). natural convection in an arbitrary inclined plate with protruding heated elements, 18th international conference of mechanical engineering, brazil. [78] lee, j. b., kim, h. j. & kim, d. k. (2017). thermal optimization of horizontal tubes with tilted rectangular fins under free convection for the cooling of electronic devices. alied sciences, 7(4), 352. [79] degao, h., xiaofeng, x. & qian, j. (2020). analysis of natural convection heat transfer from vertical and inclined plate fin heat sinks. proceedings of the seventh asia international symposium on mechatronics, 479-487. https://www.sciencedirect.com/science/article/abs/pii/s1359431119346861#! https://www.sciencedirect.com/science/article/abs/pii/s1359431119346861#! https://www.sciencedirect.com/science/article/abs/pii/s1359431119346861#! https://link.springer.com/book/10.1007/978-981-32-9441-7 international journal of engineering materials and manufacture (2018) 3(4) 237-244 https://doi.org/10.26776/ijemm.03.04.2018.08 t. s. ogedengbe1 , s. abdulkareem2 and j. o. aweda3 1department of mechanical and automotive engineering elizade university, ilara-mokin ondo state, nigeria 1e-mail: temitayo.ogedengbe@elizadeuniversity.edu.ng 2,3department of mechanical engineering university of ilorin kwara state, nigeria. 2e-mail: abdulkareem.s@unilorin.edu.ng 3e-mail: joaweda@unilorin.edu.ng reference: ogedengbe, t. s., abdulkareem, s. and aweda, j. o. (2018). effect of coolant temperature on surface finish during turning of titanium alloy ti6al4v. international journal of engineering materials and manufacture, 3(4), 237-244. effect of coolant temperature on surface finish during turning of titanium alloy ti6al4v ogedengbe temitayo samson, abdulkareem sulaimon and aweda jacob olayiwola received: 18 october 2018 accepted: 04 november 2018 published: 01 december 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract high temperature generated and stresses induced as a result of turning of ti6al4v results in poor surface finish. the aim of this study was to investigate the effect of coolant temperature on the surface roughness of ti6al4v which is a core material used as an implant. a cooling system was developed to reduce the temperature of the coolant (soluble oil) from room temperature to 2oc. ti6al4v was turned in dry and cooled (at temperatures 5, 7, 9 and 11 oc) conditions. the experiment was designed using central composite design of (response surface methodology) design expert 11.0 to generate an array and optimize the machining parameters. the machining parameters used were cutting speed, feed rate, depth of cut and coolant temperature. results analyses show that cutting speed and depth of cut had considerable effect on surface roughness of ti6al4v. surface roughness reduced when coolant temperature was reduced. the results of this study shows that turning ti6al4v at a very low cutting temperature will ensure a better surface finish. keywords: turning, coolant temperature, ti6al4v, surface roughness, machining parameter 1 introduction recent technological development especially in industries such as the medical, automobile and aviation is evidently driving the practical investigation into the use of light metals such as titanium, aluminium and manganese as prosthetics and general alternatives [1]. titanium alloys have wide applications in the engineering fields, which include the aerospace, marine, automobile and medical industries. ti6al4v alloy is widely used to manufacture implants because it possesses excellent strength characteristics and oxidation resistance [2, 3]. the present day research target is developing implants that can serve for much longer period or until lifetime without failure or revision surgery [4]. however, the high cutting temperature generated during high speed machining (hsm) may result in the deterioration of surface quality of machined components and wear at the tool tip surface [5]. this is because thermal stresses as a result of machining operations on work pieces affect the surface integrity of machined parts [6]. surface finish is an important quality characteristic for machined parts [7] and is influenced by various factors some of which include feed rate, cutting speed, work piece hardness, coolant application, and the cutting tool type [8 , 9]. since titanium alloys are generally used for a component, which requires the greatest reliability, therefore the surface integrity must be maintained [10]. various researchers have attempted the improvement of surface finish using various methods. the cutting forces under dry and wet environment for machining of ti-6al-4v using uncoated inserts has been investigated [11]. the use of inserts further increased machinability of the titanium alloy. the influence of coolant on machining ti-6al-4v has also been investigated [12]. findings showed an improved ra value of 1.3µm with coolant as against 1.4µm without coolant. the machining parameters of ti-6al-4v for electric discharge machining effect of coolant temperature on surface finish during turning of titanium alloy ti6al4v 238 using a neural network approach has been modelled [13]. a significant surface roughness value of 1.75µm and an improvement in material removal rate during machining was reported. a comparative study of the cutting forces in high speed machining of ti-6al-4v and inconel 718 has been carried out [14]. the similarities and differences both quantitatively and qualitatively in terms of force related quantities have been explained. the effect of process parameters on surface roughness in turning of titanium alloy under different conditions of lubrication has been examined [15]. an overall average ra value of 1.42µm with dry, and flooded cooling conditions was achieved. apart from flooded cooling method of coolant application, other methods such as minimum quantity of lubricant (mql) and cryogenic cooling have also been employed in the removal of heat during machining. generally, the term “cryogenic” refers to fluids that have boiling point lower than -150°c (238°f). the effect of cryogenic cooling during machining of medium carbon steel on a conventional lathe machine has been studied [16]. surface roughness, cutting forces, and friction coefficient were examined and the results for the cryogenic machining to wet and dry turning was compared. results showed that machining without cutting fluid or liquid nitrogen produced higher roughness depth and indicates that cutting with conventional cutting fluid provided a stable surface roughness within the range of speed studied (175.93 – 226.19 m/min). the effect of mql on cutting performance in turning medium carbon steel using uncoated carbide inserts using various speed feed combinations has been investigated [17]. the input parameters considered were cutting speed (68 – 266m/min), feed rate (0.10 0.20mm/rev) and depth of cut (1.0 1.5mm). the flow rate of the mql adopted was 150ml/hr with air pressure 23bar and oil pressure 25bar. there was significant reduction in tool wear rate, dimensional inaccuracy and surface roughness by mql over dry machining mainly through reduction in the cutting zone temperature and favourable change in the chip-tool and work-tool interaction. this work is therefore an attempt to improve the surface integrity of ti6al4v using coolant applied through a developed cooling system. 2 methodology 2.1 design of experiment the design of experiment for this work was done using design expert software, version 10.0. the central composite designs (ccd) of the response surface methodology was used for this work because its designs accommodated and suited the experimental approach which is needed to be able to achieve a 3-level experiment with sufficient array. three process parameters with three levels were used as the control factors for dry machining while a fourth parameter was introduced for cooled machining. the four control factors selected were cutting speed, feed rate, depth of cut and coolant temperature. the control factors and their levels are shown in table 1. table 1: control factors and their levels for dry and cooled machining factor speed (m/min) feed (mm/rev) depth of cut (mm) coolant temperature (oc) level 1 1178 50 0.1 5 level 2 1374 60 0.2 7 level 3 1570 70 0.3 9 dry machining: the orthogonal array (table 2) for three factors at three levels was used for the elaboration of the plan of experiments the array l20 was selected, which has 20 rows corresponding to the number of experiments. the first column was assigned to the cutting speed (m/min), the second column to feed rate (mm/min), and the third column to the depth of cut mm. the output (responses) studied were the surface roughness and the cutting temperature. cooled machining: a fourth factor was introduced to the plan of experiments and an array of 30 runs (table 3) was generated. this resulted from the addition of a fourth factor (coolant temperature) during the cooled machining process. 2.2 experimentation the work piece material used for this experiment was ti-6al-4v alloy cylindrical bar of 100 mm long and 20 mm diameter (fig 1.). the chemical composition of the work sample was checked and is given by table 4. the tool material utilized for this work is pvd coated ts 2000 (code snmg120408-mr3 ts2000), made of tungsten carbide hard micro grain abrasives as shown in fig. 2. an ajax–ev 310 model cnc machine with a computer interface unit from ge fanuc series d721-10 (fig 3) was used for this study. the temperature at the cutting zone was measured using a thermocouple meter. the thermocouple wire probe was attached to the cutting tool at a distance of 0.5mm from the edge of the tool to ensure a correct capture of temperature at the cutting zone during machining. a sample ti6al4v implant was acquired from a medical facility (fig.1 a) and the surface roughness was measured, a surface roughness value of 0.52µm was obtained. ogedengbe, abdulkareem and aweda (2018): international journal of engineering materials and manufacture, 3(4), 237-244 239 table 2: orthogonal array for dry machining from design expert cutting speed (m/min) feed rate (mm/rev) depth of cut (mm) 1570 50 0.3 1374 60 0.2 1178 50 0.3 1570 70 0.1 1374 60 0.2 1178 70 0.1 1374 60 0.2 1570 70 0.3 1570 50 0.1 1178 70 0.3 1178 50 0.1 1374 60 0.2 1044.37 60 0.2 1374 76.8179 0.2 1374 60 0.2 1374 60 0.2 1374 60 0.368179 1374 43.1821 0.2 1703.63 60 0.2 1374 60 0.0318207 a b figure 1: (a) ti6al4v implant (b) schematic for specimen (ti-6al-4v) ic = inscribed circle re = corner radius s = insert thickness l = cutting edge length a b figure 2: (a): pvd coated carbide insert (b) schematic for insert effect of coolant temperature on surface finish during turning of titanium alloy ti6al4v 240 table 3: orthogonal array for cooled machining from design expert cutting speed (m/min) feed rate (mm/rev) depth of cut (mm) 1178 50 0.1 1570 50 0.1 1178 70 0.3 1570 50 0.1 1178 70 0.1 1178 50 0.3 1570 70 0.3 1374 60 0.2 1374 60 0.2 1570 50 0.1 1178 70 0.1 1570 70 0.1 1570 70 0.3 1178 50 0.1 1178 70 0.3 1374 60 0.2 1178 50 0.3 1570 70 0.1 1374 60 0.2 1570 50 0.3 982 60 0.2 1374 60 0.2 1374 60 0.2 1374 80 0.2 1374 60 0.4 1374 40 0.2 1374 60 0.2 1374 60 0.2 1374 60 0.2 1766 60 0.2 figure 3: experimental setup showing probe attachment ogedengbe, abdulkareem and aweda (2018): international journal of engineering materials and manufacture, 3(4), 237-244 241 table 4: chemical composition of ti-6al-4v component al v c fe n o h ti % composition 5.99 3.97 0.03 0.1 0.01 0.14 0.005 balance 3 results and discussions the experimental results were analysed using signal-to-noise (s/n) ratio. smaller-is-better was chosen for surface roughness (sr) since smaller sr indicates better process performance. table 5 shows the anova of the dry and cooled machining results, with total error classified into pure error and lack of fit. results show that p-value was < 0.0001 which showed that the models where significant at over 99% confidence level. in both models for machining parameters (cutting speed, feed rate, depth of cut, cutting speed x feed rate, cutting speed x coolant temperature, feed rate x coolant temperature) showed a significant value (p ≤ 0.05). table 5: analysis of variance (anova) for dry and cooled machining results source sum of squares degree of freedom mean square f-value p-value dry machining model 1.81 9 0.20 44.05 < 0.0001 a-cutting speed 1.15 1 1.15 250.75 < 0.0001 b-feed rate 0.27 1 0.27 59.16 < 0.0001 c-depth of cut 0.15 1 0.15 33.42 0.1003 ab 0.011 1 0.011 2.30 0.0163 ac 0.014 1 0.014 2.98 0.1184 bc 2.112e-003 1 2.112e-003 0.46 0.5136 a2 0.059 1 0.059 12.90 0.0058 b2 0.020 1 0.020 4.42 0.0148 c2 0.17 1 0.17 36.88 0.0002 residual 0.041 9 4.569e-003 lack of fit 0.041 5 8.159e-003 0.042 0.0003 pure error 3.250e-004 4 8.125e-005 cor total 1.87 19 adjusted r-squared: 0.9556 cooled machining model 0.32 14 0.023 28.46 < 0.0001 a-cutting speed 0.25 1 0.25 311.06 < 0.0001 b-feed rate 0.022 1 0.022 27.62 0.0001 c-depth of cut 0.015 1 0.015 18.04 0.1008 d-coolant temp 0.014 1 0.014 16.84 0.0011 ab 1.562e-004 1 1.562e-004 0.19 0.6661 ac 7.562e-004 1 7.562e-004 0.94 0.3486 ad 1.806e-003 1 1.806e-003 2.25 0.0156 bc 5.256e-003 1 5.256e-003 6.54 0.0228 bd 5.625e-005 1 5.625e-005 0.070 0.0195 cd 5.625e-005 1 5.625e-005 0.070 0.7953 a2 2.800e-003 1 2.800e-003 3.48 0.0831 b2 3.407e-003 1 3.407e-003 4.24 0.0586 c2 2.976e-007 1 2.976e-007 3.702e-004 0.9849 d2 4.357e-003 1 4.357e-003 5.42 0.0354 residual 0.011 14 8.040e-004 lack of fit 0.011 10 1.116e-003 44.63 0.0012 pure error 1.000e-004 4 2.500e-005 cor total 0.34 29 adjusted r-squared:0.9321 effect of coolant temperature on surface finish during turning of titanium alloy ti6al4v 242 an interaction was observed between cutting speed and feed rate during surface roughness analysis for cooled machining. this shows that the effect of cutting speed during cooled machining depends on the level of feed rate used. however, cutting speed x depth of cut and feed rate x depth of cut were not significant parameters (p>0.05) for both models of dry and cooled machining. the surface roughness results obtained for all runs of the experimental design for the dry and cooled machining were represented by response surfaces (fig. 4). the responses were represented by a three dimensional surface plots of two factors; cutting speed and feed rate with their corresponding contour plots. feed rate and coolant temperature had a higher impact on the surface roughness of dry and cooled machined ti6al4v respectively, while the effect of cutting speed was lower. the effect of depth of cut on surface roughness was minimal. a b figure 4: response surface and contour plot for (a) dry machining and (b) cooled machining. d value 5 6 7 8 9 1178 1276 1374 1472 1570 0.1 0.2 0.3 0.4 0.5 0.6 0.7 s r ( um ) a: cutting speed (m/min)d: coolant temp (deg celc) d value d value 50 55 60 65 70 1178 1276 1374 1472 1570 1.6 1.8 2 2.2 2.4 2.6 2.8 s r ( um ) a: cutting speed (m/min)b: feed rate (mm/rev) ogedengbe, abdulkareem and aweda (2018): international journal of engineering materials and manufacture, 3(4), 237-244 243 figure 5: surface roughness during dry and cooled machining conditions. figure 6: cutting temperature during dry and cooled machining conditions. during dry machining, the highest and lowest surface roughness values were 2.80μm and 1.67μm respectively. results obtained (fig.5) after coolant temperature was reduced from room temperature to 5, 7, 9 and 11oc showed an improvement in the surface integrity of the workpiece with a highest and lowest surface roughness values further reducing to 0.61μm and 0.19μm respectively. these improvements were as a result of a decrease in heat generation. similar result was gotten by [18, 1] where they found that lubrication had a high effect on surface roughness. the surface roughness obtained during cooled machining showed a 63% improvement in surface integrity of ti6al4v during machining when compared with the surface roughness of the implant acquired and measured. the coolant temperature reduction also affected the temperature at the cutting zone as the tool tip temperature was reduced (fig. 6) from a maximum value of 909oc obtained during dry machining to 24oc during cooled machining. this represented an improvement of 97.4% a value better than that recorded by [1]. 4 conclusion an experimental investigation on the effect of coolant temperature on machining of ti6al4v alloy with a view to improve surface roughness using a cooled coolant was attempted. the following are the conclusions reached / key findings from research.  coolant temperature, feed rate and cutting speed had strong impact on the surface roughness and cutting temperature.  the effect of depth of cut was considerably low.  surface roughness for ti6al4v was improved to 0.19µm when the coolant temperature was reduced.  tool-work piece interphase was reduced by 97.4% during cooled machining. effect of coolant temperature on surface finish during turning of titanium alloy ti6al4v 244 therefore, when the temperature of coolant is reduced during machining of ti6al4v, the surface profile could be improved and cutting temperature reduced to ensure a safer and more reliable workpiece and part especially as a biomedical implant. acknowledgement the authors are grateful for generous support from to central engineering workshop, university of ilorin, kwara state, nigeria and central engineering laboratory/workshop, elizade university, ilara-mokin, ondo state, nigeria where this research has been conducted. references 1. ogedengbe t.s., abdulkareem s., aweda j.o. (2018). effect of coolant temperature on machining characteristics of high carbon steel, covenant journal of engineering technology, 1(1), 73-86. 2. oldani c. and dominguez a. (2012). titanium as a biomaterial for implants, recent advances in arthroplasty, dr. samo fokter (ed.), isbn: 978-953-307-990-5, intech, retrieved from: http://www.intechopen.com/books/recent-advances-in arthroplasty/titanium-as-a-biomaterial-for-implants. 3. andriya n., venkateswara r.p. and sudarsan g. (2012). dry machining of titanium alloy using pvd coated tialn tools, proceedings of the world congress on engineering, vol iii, wce 2012, london, u.k. 4. virginia s. v. and fuentes e, titanium and titanium alloys as biomaterials (2013). tribology – fundamentals and advancements, retrieved from http://dx.doi.org/10.5772/55860. 5. abdulkareem s., ogedengbe t.s., aweda j.o, khan a.a (2017). comparative analysis of aisi 1050 steel using n5-soluble oil and arachis oil in metal cutting operation, proceedings of the 30th agm and international conference of the nigerian institution for mechanical engineers. kaduna, 2017, 195 – 206 6. guesser w. l., pereira f. s. and boehs l. (2016). surface changes during turning of grey cast iron, int. j. machining and machinability of materials, 18(3), 313-324. 7. kalpakjian m., moss t. and kurat h. (2006), tool life and surface integrity in turning titanium alloy, journal of materials processing technology, 118, 231-237. 8. rao m. and venkatasubbaiah k. (2016). effect and optimization of edm process parameters on surface roughness for en41 steel. international journal of hybrid information technology, 9(5), 343-358. 9. ezugwu chinedu a. k., okonkwo ugochukwu c., sinebe jude e., okokpujie imhade p. (2016). stability analysis of model regenerative chatter of milling process using first order least square full discretization method, international journal of mechanics and applications, 6(3), 49-62. doi: 10.5923/j.mechanics.20160603.03. 10. che-haron c.h and jawaid m.l (2005). tool life and surface integrity in turning titanium alloy, journal of materials processing technology 188, 231-237. 11. hong, s.y., markus, i., jeong, w. (2011). new cooling approach and tool life improvement in cryogenic machining of titanium alloy ti-6al-4v. international journal of machine tools &manufacture, vol. 41, no. 15. p. 2245-2260, doi:10.1016/s0890-6955(01)00041-4. 12. nambi m. and davim p. (2011). influence of coolant in machinability of titanium alloy (ti-6al4v), journal of surface engineered materials and advanced technology, 1, 9-14. 13. rahman, m., wong y. s., and zareena a. r. (2003). machinability of titanium alloys. jsme international journal, series c: mechanical systems, machine elements and manufacturing. 46(1): p. 107-115. 14. yuan, s.m., yan l.t., liu w.d. & liu q. (2011). effects of cooling air temperature on cryogenic machining of ti– 6al–4v alloy. journal of materials processing technology, 211(3), 356-362. 15. ali s.m., dhar, n.r. & dey, s.k. (2011). effect of mql on cutting performance in turning medium carbon steel using uncoated carbide inserts using various speed feed combinations. advances in production engineering & management 6, vol. 3, pp. 185-196. 16. ramana m.v., vishnu a.v., rao g.k.m. & rao d.h (2012). effect of process parameters on surface roughness in turning of titanium alloy under different conditions of lubrication, recent advances in robotics, aeronautical and mechanical engineering, isbn: 978-1-61804-185-2, 83-91. 17. yap t.c, sivarao c. s. lim, j. w. leau (2015). surface roughness and cutting forces in cryogenic turning of carbon steel, journal of engineering science and technology, 10(7), 911–920 18. ali s.m., dhar, n. r. & dey, s.k. (2011): effect of mql on cutting performance in turning medium carbon steel using uncoated carbide inserts using various speed feed combinations. advances in production engineering & management 6(3), 185-196. 19. shetty, r., jose, t. k., revankar, g. d., rao, s. s., & shetty, d. s. (2014). surface roughness analysis during turning of ti-6al-4v under near dry machining using statistical tool. international journal of current engineering and technology, 4(3), 2061-2067. international journal of engineering materials and manufacture (2018) 3(3) 143-150 https://doi.org/10.26776/ijemm.03.03.2018.03 failure analysis of stainless steel lanyard wire rope aginaparru sambasiva rao and ashok kumar singh received: 26 june 2018 accepted: 21 july 2018 published: 15 september 2018 publisher: deer hill publications © 2018 the author(s) creative commons: cc by 4.0 abstract present work describes the failure analysis of aisi 304 stainless steel lanyard wire rope which has failed during application in humid atmosphere. the wire rope has 7×19 construction which means that it consists of seven strands and each strand having 19 wires twisted in a helical fashion. the microstructures and properties of failed wire rope have been investigated and compared with unused wire rope. both the periphery and fracture surface of the wire rope display the presence of corrosion debris enriched with o and cl. the fracture surfaces of the failed and unused wire ropes display intergranular and dimples, respectively. the lanyard wire rope has been exposed in corrosive atmosphere and failed in intergranular mode due to enrichment of o and cl along the grain boundaries. keywords: lanyard wire rope, stainless steel, epma, intergranular corrosion 1 introduction lanyard wire ropes or cable assemblies are cables comprised of many spiralled bundles of wire. these wire ropes have connector at each end for connecting the body support to fall arrestor, energy absorber, anchorage connector or anchorage [1]. this covers a very broad range of wire rope products, and wire rope lanyards can be extensively customized to meet the needs of a multitude of applications. these are commonly used in security, holding, hanging, attaching, anchoring, lifting, supporting and pulling. the wire ropes have been designed for specific purpose depending on a particular application [2]. wire rope consists of multiple strands of wire filament which themselves are twisted together before being wound helically around a core. the number of each set of strands depends on the strength requirements for proposed application [3]. the construction of lanyard wire rope is defined as n×p where n and p are number of strands and number of wires in each strand, respectively [2]. a common lanyard wire rope is represented by as 7×19 construction which suggests that this is made up of nineteen small wires being twisted together with seven other similar bundles [4]. among all other materials, stainless steel lanyard is usually found in unique work areas. apart from the other features, high strength, excellent abrasion resistance and corrosion resistance are the most important characteristics [1]. stainless steels are used in corrosive environment particularly in area of petrochemical industries and humid atmosphere [5]. these wires are also coated with different plastic materials to enhance both the functional as well as appearance. the major defects in wire ropes are by and large due to oxidation, corrosion, excessive heat, chemical degradation etc. [6]. in addition, environmental condition particularly humid atmosphere containing seawater also initiates the degradation of wire ropes. it is to be noted that the seawater contains chlorine that corrodes the metals in general and stainless steel in particular [7]. nonetheless, all the wire ropes fail in the zone which has been subjected to highest amount of fatigue and abrasion [8-12]. the present work is thus concerned with the failure analysis of a 7×19 construction lanyard wire rope which has failed during application in humid atmosphere. the microstructure and properties of unused wire has also been investigated and compared with the failed rope. 2 experimental initially, visual examinations of the broken lanyard wire rope were carried out and the photographs of the failed wire rope were captured using digital camera. the chemical composition of wire rope was analysed using inductively coupled plasma optical emission spectroscopy (icp-oes) and given in table 1. the interstitial elements such as c and s were measured using inert gas fusion technique. a. s. rao1 and a. k. singh2 materials science division, defence metallurgical research laboratory defence research & development organization, kanchanbagh, hyderabad, 5000258 india 1e-mail: sivadmrl@gmail.com, 2e-mail: singh_ashok3@rediffmail.com reference: rao, a. s. and singh, a. k. (2018). failure analysis of stainless steel lanyard wire rope. international journal of engineering materials and manufacture, 3(3), 143-150. failure analysis of stainless steel lanyard wire rope table 1: chemical composition of the failed wire rope. element c s ni cr mn si fe wt.% 0.08 0.002 8.2 19.7 1.8 0.92 balance it suggests that the material used for wire rope is austenitic stainless steel and conforms to aisi 304 grade. wires were cut from the failed wire rope near the actual fractures and prepared for metallographic examination. the polished surface was etched with aquaregia (50% hcl and 50% hno3 by volume). microstructural characterization was done using optical microscope (astm e-4). the failed wires at the fractured surface were separated from the long wire rope and then bound together with a copper wire. these wires were cleaned ultrasonically in acetone to remove any dirt and other lubricant residues over the fracture surface. the fracture surfaces of the multiple wire failed sections near actual fracture were examined under a fei make environmental scanning electron microscope (model: quanta 400) to evaluate the contaminated products over the fracture surface as well as mode of fracture. as received failed rope, wires were further examined using electron probe micro analyser (epma) to study the grain boundary constituents that have caused the degradation of microstructure. samples were prepared as per metallographic examination and analysed in un-etched condition for epma examination. back scattered electron (bse) image, elemental distribution mapping and line profile for different elements were analysed using cameca make, sx-100 model epma. quantitative analysis was carried out with an operating voltage of 20 kv and with a stabilized beam current of 20 na. a lif (lithium fluoride) crystal was employed to diffracting ti kα, mn kα and ni kα; pet (pentaerythritol) crystal was used for diffracting cr kα, mo lα, v kα, nb kα and cl kα and tap (thallium acid phthalate) crystal was employed for diffracting si kα x-ray lines. pseudocrystals of pc2 having 2d value of 98 å was utilized for oxygen analysis. x-ray intensities were obtained both on respective pure metallic standards and on samples with identical operating conditions. absolute elemental concentrations were attained using built in analytical software with essential zaf correction to get accurate weight/atom percentage of constituents in the respective sample. wire rope strands were separated from the rope and cut to desired length for tensile testing. tensile properties of failed, used (but not failed) and unused wire ropes were evaluated to know the maximum load bearing capacity. room temperature tensile tests (astm e8) were conducted with a strand containing 19 wires on screw driven instron (5500 r) testing machine (instron corporation, norwood, ma). three specimens were tested in each wire rope and average values are reported in table 2. fracture surfaces of tensile specimens were again examined under environmental scanning electron microscope (sem: fei quanta 400). 3 results the broken wire rope in as-received condition is shown in figs.1 (a-c). wire rope is made up of seven strands and each strand comprises 19 wires (rope length: 3 feet 6 inches). this displays dark brownish colour. the wire rope supplied with two broken ends (fig. 1a). this consists of many small diameter wires wound together into strands and then these strands are knit jointly into a wire rope. the end fittings of the wire rope are festinated with open swaged socket. broken end region displays several wires unwound and loosen from their strands (fig.1 b, c). figure 1: photograph of failed wire rope: (a) as-received condition, (b) one end of the broken rope, (c) another end of the broken rope displays several wires unwound from its strands and loosens from their strands. 144 rao and singh (2018): international journal of engineering materials and manufacture, 3(3), 143-150 optical microstructures of the wire rope are shown in fig. 2. this displays the presence of typical equaixed austenitic grains along with annealing twins (fig. 2a). the grain size near and away from failed appears to be same. very close to the fractured area, the microstructure exhibits extensive material degradation due to grain boundary weakening. the several pieces of material consisting of a few grains are dislodged from the periphery of the individual broken wire by breaking along grain boundaries (figs. 2b). bse image close to the fracture obtained in un-etched condition exhibits continuous thin film along grain boundaries (fig. 3). this observation is analogue to the optical microstructure (fig. 2). the x-ray elemental mappings of o, cl, cr, ni and mn elements of failed wire rope in un-etched condition obtained by epma are shown in fig. 4 (a-f). elemental distribution mapping reveals that the grain boundaries are enriched with oxygen, chlorine and chromium fig. 4 (b-d). on the other hand, uniform distributions of nickel and manganese are observed in the matrix fig. 4 (e-f). in order to confirm these results, x-ray line scan technique has been employed for oxygen chlorine and chromium elements and results are shown in fig. 5. this reflects evidently that the line scan profiles have validated the enrichment of oxygen, and chlorine at the grain boundary. line profile has also displayed the chromium enrichment at the grain boundary as well as the depletion at either side of the grain (i.e. at the vicinity of grain boundary). the fracture surfaces of failed wire rope near the actual fractures are shown in figs. 6 (a-d). thick layer of foreign material deposition is exhibited over the fracture surface of the individual wires and all around the surface of each wire. the fracture surfaces of the wire appear to be rough and the individual wire does not show distinctive mode of fracture features. these are similar to mud cracks with oxide layer (fig. 6 b-d). figure 2: optical micrograph of failed wire rope shows (a) austenite grain structure with few dislodged grains from the grain boundaries at the surface near fracture and (b) high magnification of figure a. figure 3: bse microstructure of the individual wire near failed end showing dislodged grain structure at the surface and dark network along grain boundaries. 145 failure analysis of stainless steel lanyard wire rope figure 4: (a) bse micrograph and x-ray elemental distribution mappings: (b) cr, (c) o, (d) cl, (e) ni and (f) mn obtained by epma technique. figure 5: epma line profile of the elements o, cl and cr across the grain boundary demonstrates as reflected in the x-ray mappings. 146 rao and singh (2018): international journal of engineering materials and manufacture, 3(3), 143-150 edax spectrum taken on fracture surface of the failed rope near the actual fractures has revealed the presence of chlorine and oxygen in addition to matrix elements (fig. 7). these results are well agreement with those obtained by epma analysis (fig. 4 and 5). tensile properties of failed, used (but not failed) and unused wire ropes are summarized in table 2. it clearly shows that the load bearing capacity of the failed wire has reduced nearly 1/4 and 1/2 times of the unused and used wires, respectively. the ultimate tensile strengths of the wires reported in table 2 also support the same. the fracture surfaces of tensile tested specimens of the failed and unused wires are shown in figs. 8 and 9. the flat fracture with no reduction in the cross sectional area is seen in the failed individual wire (fig. 8a). figure 6: sem fractographs of individual failed wire obtained at (a) low magnification and (b-d) high magnification show thick layer deposition of corrosion debris over the fracture surface. figure 7: edax spectrum taken from the fracture surface of the failed individual wire exhibits presence of o and cl in addition to matrix elements. 147 failure analysis of stainless steel lanyard wire rope fracture surface of tensile tested wire of the failed rope displayed a thick metallic layer covered around the circumference of the failed wire. however, a part of the thick layer of the individual wire has fallen away from close to tensile fracture during tensile deformation (fig. 8a). the fracture surface of the wire appears to be rough and clearly reveal the presence of intergranular fracture (figs. 8 (c and d)). the tensile fracture surface of the unused wire exhibits smooth surface finish around the rope outer surface (fig. 9a). the fracture features displays sufficient necking indicating typical ductile mode of failure (fig. 9b). table 2: tensile properties of the strands for unused, used (not failed) and failed wire ropes. sl. no. description max. tensile breaking load (kn) uts (mpa) 1. strand from unused wire rope 3.00 1490 2. strand from used (not failed) wire rope 1.35 685 3. strand from failed wire rope 0.70 378 figure 8: sem fractographs of tensile tested failed wire rope: (a) low magnification and (b-d) high magnification reveals flat fracture with intergranular mode of failure. figure 9: sem fractographs of tensile tested unused wire rope: (a) low magnification (b) high magnification showing considerable reduction in size with dimple mode of fracture. 148 rao and singh (2018): international journal of engineering materials and manufacture, 3(3), 143-150 4 discussions chemical composition of the wire rope indicates that the wires are made using austenitic stainless steel aisi 304 grade (table 1). presence of annealing twins within the equiaxed austenitic grains indicates that the wire rope is used in annealed condition (fig. 2a). this also suggests that the rope wires are initially prepared by wire drawing and subsequently annealed. the optical microstructure of the wire exhibits two features namely (a) overall grain size is nearly uniform from centre to periphery and (b) several cracks along the grain boundaries at the periphery of the wire rope. in addition, parts of material consisting of several grains have been dislocated from the wire (figs. 2 b). the dislocated materials have broken from the wire along the grain boundaries. this clearly reveals that that the grain boundaries have significantly weakened during service. the bse micrograph of un-etched samples resembles similar features to that of the optical microstructure. epma x-ray elemental mappings reflect that grain boundaries are enriched with cl, o and cr (fig. 4). the weakening of grain boundaries along with dislodged materials from the periphery of the wire therefore indicates that the rope is exposed to corrosive environment during the service. presence of cl and o at the grain boundaries in the form of thin film supports the same. in addition, the periphery of the individual wire is also surrounded by thick continuous layer of the corrosive debris (fig. 6 a-d). fracture surfaces of the failed rope have shown the presence of corrosion debris which in fact has masked the actual fracture (fig. 6). the edax spectrum of the fracture surface also supports the presence of cl and o (fig. 7). all the wires in the failed rope have shown similar behaviour. the results of the tensile tests of the used (but not failed) and unused wires have been utilized to explain the occurrence of typical fracture features of the failed wire rope. fascinatingly, the load bearing capacity of the failed wire has reduced to nearly 1/4 of the unused wire rope (table 2). the used (but not failed) wire on the other hand also displays reduction in breaking load nearly half of unused wire rope. this also reflects that the properties of the rope have deteriorated significantly during service. tensile tested fracture surfaces of the unused wires display entirely different features (fig. 9) than that of the failed wires in terms of mode of failure (fig. 8). the failed wire exhibits typical intergranular fracture in spite of the presence of corrosive debris. in addition, this also shows the presence of thick layers around the periphery (fig. 8a). on the other hand, fracture surfaces of unused wire rope exhibits smooth surface finish around the rope outer surface (fig. 9a). unused wire rope has undergone significant necking before tensile failure and finally failed in ductile mode. this clearly suggests that the wire rope has slowly deteriorated during service and then suddenly failed with intergranular fracture mode. it appears that the crack propagated along the weak grain boundaries during tensile test and finally failed in intergranular mode (fig. 8). when passive metals such as the stainless steels corrode, the corrosion develops where passivity has been destroyed. if there are halogenides such as chlorides present in the environment, these can interact with passive film locally and break it by introducing small isolated spots [13-14]. this is also termed as pitting corrosion. this type of corrosion is likely due to chlorine-induced pitting of the stainless steel material from the chloride containing humid environment. the chlorides can then react with chromium to form soluble chromium chloride following (crcl3) 2cr + 3cl2 = 2crcl3 reaction. as a result, cr at the grain boundaries is partly dissolved leaving only the corrosion prone iron [15]. this also introduces depletion of cr in neighbouring area of the grain boundaries which are prone to fail in intergranular mode (figs. 5 and 8). the occurrence of intergranular corrosion has also been reported even without the chromium carbide precipitates at the grain boundaries [16]. this has been attributed to high energy associated with the grain boundaries which are preferentially corroded (become anode) due to their low electrode potential in comparison to grain interior. the present lanyard rope has also failed in intergranular mode due to the formation of crcl3 in presence of humid environment. as mentioned above, microstructure of the failed wire rope exhibits thin film at the grain boundaries consisting of o and cl along with the dislodged materials containing a few grains. it appears that the presence of both the high o and cl at the grain boundaries can be ascribed to corrosive atmosphere. the chlorine ions from the water content / vapours from humid atmosphere have initially reacted with chromium oxide passive film formed on the surface of the wire and then diffused within the material along the grain boundaries. the depletion of the cr in vicinity of the grain boundaries supports the same (fig. 5). this has resulted in the failure of the wire rope in intergranular mode due to substantial weakening of grain boundaries. 5 conclusions 1. the failed wire rope near the actual fracture region consists of large amount of oxygen and chlorine which have served as initiation sites for cracks in the material. 2. the load bearing capacity of the failed wire rope strand has significantly reduced to nearly 1/4 times to that of the new unused wire rope in identical testing conditions. 3. fracture surfaces of tensile tested used and unused lanyard rope individual wires have shown intergranular and ductile dimple modes of fracture, respectively. 4. the lanyard wire rope has been exposed in corrosive atmosphere and failed in intergranular mode due to enrichment of o and cl along the grain boundaries. 149 failure analysis of stainless steel lanyard wire rope acknowledgements the authors wish to acknowledge defence research and development organization for financial support. we are grateful to dr. vikas kumar, director, defence metallurgical research laboratory for his kind encouragement. authors also thank electron microscopy, structure and failure analysis and mechanical behaviour groups of dmrl for their kind help. references 1. baszczyński, k. (2007). dynamic strength tests for low elongation lanyards. international journal of occupational safety and ergonomics, 13(1), 39–48. 2. costello, g. a. (1990). theory of wire rope. chapter 1. mechanical engineering series, 2nd edition. new york. 3. chaplin, c. r. (1995). failure mechanisms in wire rope. engineering failure analysis, 2(1), 45-57. 4. davis, g. j. (1997). wire rope user’s manual. chapter 3. committee of wire rope producers, american iron and steel institute. washington. 5. parrott, r. and pitts, h. (2011). chloride stress corrosion cracking in austenitic stainless steel. chapter 1. research report rr902. health and safety executive laboratory. 6. ren, z., lu, z., yu, q. and jiang, y. (2018). failure analysis and safety protection of a certain type of wire rope under high-speed impact loads. matec web conf., int. conf. on materials applications and engineering, 142, 03001, 1-8. (doi: https://doi.org/10.1051/matecconf/201814203001). 7. brown, b. f. (1977). stress corrosion cracking control measures, chapter 7. national bureau of standards monograph 156. 8. schrems k. k. (1994). wear-related fatigue in a wire rope failure, journal of testing and evaluation, 22(5), 490490. 9. balan k. p. (2002). failure analysis of a wire rope, practical failure analysis, 2(3), 71-74. 10. torkar, m., arzenšek, b. (2002). failure of crane wire rope, engineering failure analysis, 9, 227-233. 11. pal, u., mukhopadhyay, g., sharma, a. and bhattacharya, s. (2018). failure analysis of wire rope of ladle crane in steel making shop. international journal of fatigue, 116, 149–155. 12. kalentev, e., václav, s., božek, p., tarasov, v. and korshunov, a. (2017). numerical analysis of the stress-strain state of a rope strand with linear contact under tension and torsion loading conditions. advances in science and technology research journal, 11(2), 231–239. doi: 10.12913/22998624/71181. 13. bensalah n. (2012). pitting corrosion. chapter 7, corrosive effects of chlorides on metals, fong-yuan ma. 14. leffler b. (1998). stainless-stainless steels and their properties. chapter 3. 2nd edition. 15. tverberg, j. c. (2001). stainless steel in the brewery. mbaa tq. technical quarterly, 38(2), 67-82. 16. kodgire, v. d. & kodgire, s. v. (2013). material science and metallurgy for engineers. chapter 6. 32nd edition. 150 https://doi.org/10.1051/matecconf/201814203001 international journal of engineering materials and manufacture (2022) 7(1) 13-24 https://doi.org/10.26776/ijemm.07.01.2022.02 mrityunjoy hazra and ashok kumar singh defence metallurgical research laboratory (dmrl) p.o. kanchanbagh,hyderabad 500 058, india e-mail: mhazra@dmrl.drdo.in reference: hazra and singh (2022). fatigue behaviour of connectors used in cable harnessing through cavity formation related microstructural degradation: a failure investigation perspective. international journal of engineering materials and manufacture, 7(1), 13-24. fatigue behaviour of connectors used in cable harnessing through cavity formation related microstructural degradation: a failure investigation perspective mrityunjoy hazra and ashok kumar singh received: 23 february 2021 accepted: 16 august 2021 published: 01 january 2022 publisher: deer hill publications © 2022 the author(s) creative commons: cc by 4.0 abstract two separately failed electrical connector pieces during a vibration test were received for failure analysis. chemical composition, hardness values and microstructures of the each of the connector material indicate that the material of construction is a die cast aluminium-silicon type of alloy, closely matching with the standard ansi/aa b380 alloy. intergranular and faceted fracture features are observed and failure mechanism is found to be fatigue dominated. the connectors failed by impact fatigue arising out of the loosening of the connector assembly. this has happened by cavity formation and/or growth related microstructural degradation processes. initial casting pores as well as microstructural degradations such as interconnected pores have developed in service and their successive growth, decohesion and interconnection of each of primary si particles and al-fe-mn precipitates (along precipitate-matrix interface) have led the initiation of the crack under fatigue loading. brittle as-cast microstructure (as typified by the precipitate-matrix interfacial cracking), existing vibratory loading and absence of any rise in temperature in the system have assisted the initial cavity (crack) formation and/or growth. moreover, initial fitment related looseness is an additional factor in initiating and propagating this damaging mechanism. keywords: connector, die cast aluminium alloy, failure analysis, impact fatigue, microstructural degradation, pores. 1 introduction plated connectors meeting the quality assurance (qa) requirements for electrical performance and cleared by inspection agency are used for one system integration. the said connectors are employed for specific job of cable harnessing. the connectors are mated to each other and the whole system is subjected to vibration test. two connector pieces have found to be damaged and/or broken after the completion of vibration test at room temperature. present work describes the failure analysis of two such separately failed connectors. 2 literature review 2.1 cable harnessing and connector a cable harnessing system is an array of electrical cables or wires which transmit electrical power or mechanical/electrical signals [1]. it provides several advantages over loose wires and cables like: (i) better security against adverse effects of vibrations, abrasions, and moisture, (ii) optimum usage of space and (iii) reduced risk of a short. ipc's publication ipc/whma-a-620 for conforming and non-conforming requirements is consulted for this type of applications, unless it is customized by the user. for life-saving devices, military needs electronic products and for applications in harsh environments class 3 type of harnessing is required wherein its functioning is must for functioning of the whole assembly. a connector is a device used to create electrical circuit and join electrical termination and it is one of the important components of a harness system. connectors can be classified according to their functional operation and currentcarrying capacity into three groups: light, medium and heavy-duty connectors [2]. light duty connectors are devices operating at voltages up to 250 v and carries current below 5a. a stable and low contact resistance and right connector material is essential for a successful operation of the connectors. medium duty connectors operate at https://en.wikipedia.org/wiki/electrical_cable https://en.wikipedia.org/wiki/electrical_wiring https://en.wikipedia.org/wiki/electrical_short https://en.wikipedia.org/wiki/ipc_(electronics) hazra and singh (2022): international journal of engineering materials and manufacture, 7(1), 13-24 14 voltages up to 1000 v and carries currents above 5a. heavy duty connectors function at voltages up to hundreds of kv and carry currents up to tens of ka. 2.2 aluminium as connector material aluminium is available in a variety of suitable alloys and forms which allow for the optimum choice for the manufacture of electrical connectors [3]. aluminium alloys are defined by form, typical yield strength, minimum yield strength, elongation and percent of conductivity for specific applications. the alloys such as 6061-t6 in the extrusion form, 6063-t6 in the extrusion form, 356-t6 in the sand cast form, axs 679 (380a) in the die cast form have been traditionally used as connector for various application types. typical requirements of aluminium connectors for use with aluminium or copper conductors are: (a) adequate strength of the connector to prevent creep loss in the connection from exceeding the creep loss of the conductor, (b) strong enough clamping force (torque) to keep the connector operating temperature at a level below the operating temperature of the maximum size conductor and (c) high enough conductivity to provide adequate efficiency (minimum of 40%). reliability of power connections is dictated by: (i) reliability requirements, (ii) basic feature of electrical contacts, (iii) connector design, (iv) degradation of electrical contacts, (v) mitigating measures, (vi) new trends in electrical contact design and (vii) connector degradation. connector degradation, as of now, constitutes one of the most important parts of determining the reliability. degradation may have a highly deleterious effect on the operating cost of power network. fig. 1 depicts various factors influencing the reliability of a connector performance. 2.3 degradation of electrical connectors and contacts the damage of a connector proceeds relatively slowly and at a rate governed by the nature of a number of different processes operating along the contact zone and in the environment. this initial stage continues for a long time without causing any observable changes. however, when the contact resistance increases sufficiently to raise the local temperature, a self-triggering deterioration, resulting from the interaction of thermal, chemical, mechanical and electrical processes, would be in action and the contact resistance would rise again suddenly. thus, there happens to be a synergistic effect between temperature rise and combined effect of interactions among thermal, chemical, mechanical and electrical effects, as soon as a certain temperature level is reached in the system [3, 4]. hence, no deterioration would be noticed until the final stages of the connector life. important degradation mechanisms are given in fig. 2. some of those are briefly described below. 2.3.1 creep it is a stress-, timeand temperature-dependent phenomenon and manifested by a dimensional change. creep is an irreversible deformation offering the conductor termination by raising the potentials for overheating. aluminium’s tendency for creep is higher than those of the copper and many other conductors at normal operating as well as room temperatures. additionally, aluminium’s tendency to cold flow under pressure is significant. this leads to loosening of the terminals [2]. creep coupled with cold flow is a factor challenging termination of aluminium conductors and connectors. for this reason, aluminium should have its own regulations and standards for torque settings of terminals, connection and terminating methods [5]. figure 1: factors influencing reliability of a connector assembly. fatigue behaviour of connectors used in cable harnessing through cavity formation related microstructural degradation 15 2.3.2 stress relaxation it is also a stress-, timeand temperature-dependent phenomenon. however, it is manifested by a reduction in the contact pressure. it is higher for aluminium than those of the copper and other conductors. it occurs at high stress levels and is due to changes in metallurgical structure. it leads to reduction in contact pressure and consequently the increase in contact resistance. sometimes, resistance is raised to the point of failure by short. all metals are subjected to stress relaxation. therefore, it is important to select the alloy carefully. there are three mechanisms by which alloys are strengthened: (a) solid solution strengthened, (b) dispersion-strengthened and (c) precipitation-hardened. the stress relaxation behaviour is related to the strengthening mechanism. effect of cold deformation is nullified by time and temperature. solid solution alloys have been found to be suitable for low contact forces. higher contact forces in these alloys further require employment of cold deformation. dispersion-strengthened alloys have good resistance to relaxation but are capable of offering only intermediate contact force. they are useful when low contact forces are required for use at elevated temperatures. precipitation-strengthened alloys may be used for application requiring high contact force. 2.3.3 electroplasticity it is electricity induced enhanced plasticity event [6]. it increases creep / stress relaxation rates. combined effect of joule and electron-dislocation interaction makes the understanding of the governing mechanism behind electroplasticity quite complex. thus, exact controlling mechanism behind a particular happening is mostly unknown. it has been shown by numerous studies that separation of the joule heating and dislocation-electron interaction is possible. studies related to the use of constant amplitude direct current during plastic deformation are often reported in this regard. overall dislocation density has been found to decrease in this type of phenomenon. 2.3.4 oxidation and corrosion oxidation is accepted as the most serious degradation mechanism occurring in mechanical connectors. corrosion starts at an exposed metal surface with the formation of a corrosion product and continues as long as reactants can diffuse through the product layer and sustain the reaction. severity of the corrosion is determined by the composition and characteristics of the corrosion product layer. it may be caused by polluted atmospheres or by use of dissimilar metals in the contact. oxide films and the products of corrosion on the contact surfaces reduce real contact area and increase contact resistance. the resultant increase in temperature further accelerates the rate of attack. on the other hand, formation of insulating al2o3 is one of the most damaging factors, as it inhibits current flow, cause formation of hot spots in the contact spots. if contacts are designed to slide over each other (or wipe) when they are brought together or if connectors are frequently plugged and unplugged, the contact will have a self-cleaning action which helps to reduce contamination at the expense of increased wear. contact lubricants are useful in this case, provided they do not dissolve any aggressive pollutant to increase its surface attack. aluminium conductors have higher tendency for corrosion because of its low zero potential. the galvanic corrosion occurs by connecting aluminium with other metals having higher zero potential. it weakens the conductor and leads to contact failure. 2.3.5 fretting fretting is a surface damage occurring at the interface of contacting materials subjected to small oscillatory movements. it may occur at amplitude of less than 100 nm. a report by bock and whitley [7] in 1974 was clearly convincing to the research community on the importance of fretting damage in electrical connections, although the possible degradation mechanism in telephone relays and switches were proposed around 1964 [8]. it is commonly manifested by overheating. there is a common lack of awareness on fretting phenomenon in electrical and/or figure 2: schematic of degradation mechanisms in an aluminium connector assembly. hazra and singh (2022): international journal of engineering materials and manufacture, 7(1), 13-24 16 electronic industries, as visibility and effect of wear debris and oxides would be appreciable after a significant residence time. rapid increase in contact resistance and finally an open circuit is built up by accumulation of wear debris and oxides at contact zone between two connector surfaces over a time. fretting may not directly lead to the failure, but it is certainly a damaging phenomenon. it is omnipresent by the fact that the oscillatory movements of the connectors are produced by mechanical vibrations, differential thermal expansion of connecting materials, relaxation of loads and also by heat produced at junction by switching on and off of the power. 2.3.6 thermal expansion longitudinal expansion is important since it often leads to slip in the joint followed by loosening. it is important that long bars are provided with a flexible element so that the movement can take place elsewhere. aluminium has larger thermal expansion coefficient than the copper [2,4,5]. this may result in incompatible expansion between the terminal and a copper conductor. coupling dissimilar metals with varying thermal expansion coefficients leads to loosening of the connection over time and increase contact resistance which in turn leads to arcing and overheating of the surface. this challenges the safety and reliability of the connection [2,4,5]. 2.4 connector degradation, loosening, termination and failure 2.4.1 loosening both the creep and cold flow lead to termination of connection by overheating (through raising the potentials) and loosening, respectively. additionally, aluminium’s tendency to cold flow under pressure is significant, again leading to loosening of the assembly. this creates chances of fatigue failure and voltage drop. 2.4.2 corrosion, oxidation, contact resistance, temperature increment and contact failure oxide films and the products of corrosion on the contact surfaces reduce real contact area and increase contact resistance. this results in increase in temperature and further accelerates the rate of oxidation and corrosion attack. on the other hand, formation of insulating al2o3 inhibits current flow, cause formation of hot spots in the contact spots. as mentioned above, the galvanic corrosion weakens the conductor and leads to contact failure. 2.4.3 thermal expansion coefficient longitudinal expansion is important since it often leads to slip in the joint followed by loosening and increase contact resistance which in turn leads to arcing and overheating of the surface. this leads to contact failure. 2.4.4 issues with use of dissimilar metals at termination [2-10] using different metals at the termination join hampers handling high temperature, high vibration conditions and thermal shock due to aluminium’s high thermal expansion coefficient, leading chances of failure. the sequence of damaging phenomena beginning with entry of a connector assembly in service is described. a force is applied during termination and crimping which reduces the contact pressure resulting in non-gastight contact interface. at this point of time, corrosion and oxidation can occur even if the termination joint is sealed. this introduces loosening of the connection and increased contact resistance. it generates heat and further creep and cold flow of the conductor. increased contact resistance leads to rise in temperature and therefore chance of aggravating oxidation, corrosion, creep etc. it is to be noted that all of damaging phenomena continue in a synergistic manner along with contact resistance. additionally, increased resistance loosens the system and results into fatigue behaviour and high voltage drop. 2.5 feasible and cost-effective ways of combating connector degradation coating of the connection material is done for avoiding formation of insulating surface layer, mechanical wear and corrosion and promotes conductivity [10-14]. use of nickel, tin, silver etc. have been traditionally employed for this purpose [11-14]. aluminium, according to study done by otsuka [10], for stabilization of contact resistance, requires a higher crimping compression than the copper and many other conductors in order to improve the wire retention force that enable electrical connection. use of lubrication – the conductive area is essential for a reliable electrical contact. this is affected by both internal and external factors. one of the most simple and efficient ways of achieving large contact points are by lubrication and mechanical abrasion. this together with application of a contact aid (grease) prevents oxidation of the metal. 2.6 prognostic models for contact remaining life estimation of life time of a connector can be done by prognostic model where data collection of the component’s performance from initiation to the final stage is an important prerequisite. in case of remaining life assessment of a connector, the contact interface is assumed to be homogenous with circular shaped α-spots [16]. additionally, it is assumed that the oxygen intrusion and growth of oxide film is the main factor affecting conductivity of the surfaces. fatigue behaviour of connectors used in cable harnessing through cavity formation related microstructural degradation 17 3 experimental procedure the connectors were, at first, examined visually by naked eye and under magnifying glass. photographs in the asreceived condition were taken and preserved for future reference, during the course of analysis. the failed parts were then sectioned from the main components for its further analysis. later, those parts were put under forced air using air-blower to remove the loosely adhered particles and then examined under stereo microscope as well as scanning electron microscope (sem). fracture surface was cleaned ultrasonically in acetone after examination on probable surface corrosion debris and/or contamination, before fractographic study. after that, representative cross-sectional sample extraction from failed parts was carried out from near to the failed surface as well as from away from the failure location for detailed metallographic (optical microscopic and scanning electron microscopic) study. samples along both longitudinal as well as transverse directions were extracted and microstructural features were studied in both un-etched and etched conditions. bulk compositional analysis of the connector material was carried out by inductively coupled plasma-optical emission spectroscopy (icp-oes) type wet chemical analysis technique. dry combustion technique was used for hydrogen evaluation. compositional analyses on each of the connectors were carried out with electron dispersive spectroscopy (eds) attachment of the sem. samples were etched with keller’s reagent. vickers micro hardness readings at 500gf were taken on metallographically prepared samples to correlate those with the respective microstructures so as to obtain a reasonably complete idea about the material. 4 results 4.1 visual examination figs. 3-5 show photographs of the damaged components in as-received condition. fig. 3 exhibits one single received metal piece from a connector, named as connector 1 henceforth. as-received photographs of connectors 1 and 2 are displayed in figs. 4 and 5, respectively. a dull greyish coating (possibly of cadmium) covers the surfaces of both the connectors. fibrous type of fracture appearance seems to prevail on failed surfaces of both the connector 1 (figs. 3 and 4) and connector 2 (fig. 5). ample of rub marks are noticed on surfaces near to and away from the failed surfaces. figure 3: photographs of the as-received fractured metal piece of connector 1 in different views figure 4: photographs of the as-received connector 1 in different views hazra and singh (2022): international journal of engineering materials and manufacture, 7(1), 13-24 18 4.2 fractography figs. 6 and 7 show failed connectors and the metal piece as observed under stereo microscope. only the gross fibrous fracture appearance is visible in this stage (fig. 6). significant rubbing has been observed on the whole connector surfaces for both the connectors. figure 5: photographs of the as-received connector 2 in different views figure 6: the as-received fractured metal piece of connector 1 in different views, as seen under stereo microscope figure 7: as-received connectors in different views, as seen under stereo microscope. (a, b) connector 1, (c, d) connector 2. (a) fatigue behaviour of connectors used in cable harnessing through cavity formation related microstructural degradation 19 figs. 8-10 exhibit failed connectors and the metal piece as observed under sem. intergranular and faceted fracture features have been observed predominantly. indication of fatigue failure mechanism is clearly revealed in each of the fractographic images. secondary cracks with moderate frequency were noticed on fracture surfaces of both the connectors. significant rub marks have also been noticed here just adjacent to the fracture surfaces (figs. 8 and 10). 4.3 microstructure fig. 11 shows longitudinal and transverse metallographic sections of connector 1 in un-etched condition at various magnifications. the same for connector 2 has been presented in fig. 12. significant amount of casting porosity is seen in microstructure of both the connectors. moreover, few precipitates with appearance of fragmented particles are also noticed. figure 8: fracture surface of dislodged metal piece of connector 1 in different views, as seen under sem figure 9: fracture surface of mating part of connector 1 in different views, as seen under sem figure 10: fracture surface of connector 2 in different views, as seen under sem hazra and singh (2022): international journal of engineering materials and manufacture, 7(1), 13-24 20 the etched microstructure reveals typical heterogeneous cast appearance, consisting of dendrites and equiaxed grains (fig. 13). sem analysis displays well developed eutectic of al-si (phase a), as shown in figs. 14 and 15. al-cu rich phases (marked b) are observed at few peripheral and nodal regions of these eutectics. on the other hand, in some of the regions, the al-fe-mn rich phases (phase f) are found within the al-si eutectics. primary si particles of varying sizes and shapes (phase d) are observed within al-si rich matrix throughout the microstructure. besides, al-fe rich rod shaped phases (phase g) are found to be spreaded across the eutectic and matrix regions. occasional presence of w-fe rich foreign phases is observed. various types of cavities are seen, viz. (a) inherent casting pores of two types (marked e and e / ), (b) cavity formed by fracture of primary si particles and its interconnection (marked d / ), (c) those formed by fracture of al-fe-mn precipitates and its interconnection (marked f / and f // ). fractured, dislodged and interconnected al-fe-mn precipitates appear as grain boundary cracks (marked f // ). on the other hand, some inherent casting cracks and/or interconnected inherent pores (marked e / ) become visible as curvy line. a coating of average thickness 5 µm is observed on each of the connector surfaces, as represented by the sem image displayed in fig. 16. eds analysis on coating reveals that it is of ni-p type. various types of phases and cavities are enlisted in table 1. figure 11: optical microstructure of connector 1 for longitudinal (a) and transverse (b) sections in different magnifications. un-etched. figure 12: optical microstructure of connector 2 for longitudinal (a, b) and transverse i sections in different magnifications. un-etched. figure 13: representative optical microstructure of connectors (connector 1 here) for longitudinal (a) and transverse sections (b). etchant: keller’s reagent. fatigue behaviour of connectors used in cable harnessing through cavity formation related microstructural degradation 21 figure 14: representative sem microstructure of longitudinal section of connector 1 in different magnifications (a,b). etchant: keller’s reagent. figure 15: representative sem microstructure of connectors – (a,b) transverse section of connector 1, longitudinal section of connector 2 in se i and bse (d) modes, etchant: keller’s reagent. figure 16: one representative sem image showing coating on the connectors along with corresponding eds analysis, etchant: keller’s reagent. hazra and singh (2022): international journal of engineering materials and manufacture, 7(1), 13-24 22 table 1: list for various phases and cavities marked phases in figs. 15 and 16 description a al-si eutectic b al-cu rich phases c matrix d primary si particles f al-fe-mn rich phases g al-ferich rod shaped phases d / cavities formed by fracture of primary si particles e inherent casting pores, type i e / inherent casting pores, type ii f / cavities formed by fractured and dislodged al-fe-mn precipitates f // cavities formed by interconnection of cavity type f / table 2: chemical composition of failed connector materials content (wt. %) material cu si zn fe mn ni mg sn al h connector 1 2.69 6.97 0.47 0.77 0.33 0.089 0.055 0.023 rem. 0.0030 connector 2 3.39 9.98 1.40 1.10 0.29 1.07 0.13 0.023 rem. 0.0024 4.4 chemical composition and hardness table 2 reveals bulk compositions and hydrogen content of two failed connector material. vickers hardness value taken at 500 gf load for the connector materials (connector 1 and connector 2) is found to be  90 ± 03 hv. 5 discussions 5.1 material of construction for the connectors: identity and suitability chemical composition, hardness value and microstructure of the connector material indicate that the material of construction of the connectors is a die cast al-si type of alloy, closely matches with the standard ansi/aa b380 alloy [17,18]. coating of ni-p type of around 5 µm thickness is observed on the connector surfaces, while standard practice is to have ni coating of 20 µm thickness (min) followed by a 10 µm ag coating on top for lowering contact resistance arising out of aluminium oxides [19,20]. porosity is observed to be distributed quite uniformly throughout the microstructure. die cast aluminium alloys of this type has been traditionally recommended and popularly used in electronic connectors and housings, because of their excellent electrical performance and shielding properties. usually recommended and most popular aluminium alloy for electrical and/or connector is a380 [17,18]. b380 is a sub-class of a380 with restricted zn content (≈ 1 wt.%) as compared to that (≈ 3wt.%) in a380 alloy [18]. use of b380 probably suits better than the a380 in the present type of applications as the former has higher high temperature capability and lower susceptibility for hot tearing. different casting processes can lead to different amounts of porosity (both in terms of shrinkages and gaseous porosities) due to their specific peculiarities [18,21]. die cast products, especially high pressure die cast (hpdc) alloys usually contain higher amount of porosity than that is found in conventional and also in advanced casting processes. however, in absence of the intended specification of the material for connector type of applications, it is not possible to comment on the desirable level of porosities in the presently investigated material system. however, it should be noted that porosity affects fatigue properties of cast aluminium alloy very significantly. there are different sources of porosity and defects in aluminium casting [21]. these are (i) alloy related and/or (ii) process-related. alloy related issue concerns with the volume reduction associated to the liquid-solid transformation, which may result in macroporosities (due to the presence of hot spots) as well as in microporosities (interdendritic shrinkages). process related issue include (a) evolution of hydrogen and its entrapment within the material structure, due to strong decrease in its solubility during liquid to solid phase transformation of the material, (b) entrapment of gases (and of derived oxides) due to excessive turbulence in flow of molten alloy during the filling stage. combined effects of alloy and process related issues include: (a) establishment of stress states during solidification, causing cracks and hot tears into the cast alloy and (b) presence of inclusions and the development of gases from cores. 5.2 failure mechanism intergranular and faceted fracture features are observed. fracture surfaces of both the connectors have revealed evidence of fatigue dominated mechanism. the probable initiation regions of fatigue failure seem to be the cavities present in the microstructure [22,23]. cavities are present in various forms, viz. original casting pores, interconnected pores in service, cracking and decohesion of various microstructural precipitates. presence of ample of rubbed zones on connector surface at region close to the fracture as well as at regions away from the fracture (figs. 4,7,8 and 9) indicates continuous hitting between two mating connectors. this is due to initial fitment related looseness and/or by loosening of the system due to cavity formation related degradation processes of the connector material [22]. fatigue behaviour of connectors used in cable harnessing through cavity formation related microstructural degradation 23 however, based on background information received from the user, the fitment related looseness has a remote chance of occurrence. interestingly, in the present case, again by background information, chance of creep type of high temperature degradation is nil, as vibration tests are conducted at room temperature. also, there is no increase in temperature of the system as a result of increase in contact resistance by oxide formation and/or relaxation of the system over a time etc., as monitored continuously. thus, the above mentioned cavity formations and their interconnections are aided only by vibratory type of loading. the said repeated hitting of mating connector surfaces for presently used connector like cast materials with very low ductility (≈ 3% elongation value) resembles almost to phenomenon like repeated impact loading [17,18]. this indicates the presence of rapid rate of loading in cyclic (fatigue) mode. now, as is mentioned earlier, material weakness in form of various types of cavities (table 1) is observed in the microstructure. this weakness often appears like grain boundary cracking. few other areas are full of regions with decohesion of al-fe-mn precipitates. also, occasional contribution of unexpected phases containing fe and impurities like w (and expected to be brittle one) to the cracking phenomenon observed. this type of microstructure justifies very much the granular and/or layered fracture appearance of the failed connectors [22]. the fatigue type of loading evolved from connectors has in fact, aided enlargement and/or interconnection and/or alignment of the already present cavities along a particular direction. also, it aided the decohesion of al-femn precipitates. thus, the fatigue type of loading had substantial contribution to the type of fracture observed, along with original microstructural features (defects). on the other hand, low ductility of the material and thus its exposure to rapid rate of loading (under continuous hitting and rubbing of mating surfaces) has accelerated the failure process by accelerating the formation of crack of sufficient length for inducing high propagation rate by quick interconnection of cavities. simultaneous actions of fatigue as well as rapid rate of loading have produced intergranular and/or layered fracture appearance of an already defected microstructure without dimples. 6 conclusions this research investigates the fatigue failure perspective of connectors used in cable harnessing. based on this research the following conclusions were drawn. 1. the connectors have failed by fatigue arising out of the loosening of the connector assembly due to cavity formation related microstructural degradation processes. 2. initial casting pores and microstructural degradations such as interconnected pores developed in service, successive cracking, decohesion and interconnection of each of primary si particles and al-fe-mn precipitates have led the initiation of the crack under fatigue loading. 3. fatigue type was found to be of impact type. acknowledgement the authors would like to thank dr. g madhusudhan reddy, outstanding scientist and the director, dmrl for his constant encouragement to work on the present field. also, funding from drdo is gratefully acknowledged. references 1. www.cableharnessing.co.uk, last accessed on 27.02.2020. 2. braunovic, m. “power connectors,” in electrical contacts principles and applications, 2 ed., p. g. slade, ed., crc press taylor & francis group, 2014, 233-366. 3. hamedi, e. electrical connection for aluminium conductors in automotive applications: prestudy of available solutions for electrical connection methods of aluminium cables, inom examensarbete material design, avancerad nivå, 30 hp, stockholms verige 2017. 4. chapman, d. copper in electrical contacts, copper development association publication no 223, european copper institute publication no cu0169, july 2015. 5. ss-iso 6722-2. road vehicles-60v and 600v single-core cables-part 2: dimensions, test methods and requirements for aluminium conductor cables. 6. tiwari, j., pratheesh, p., bembalge, o.b., krishnaswamy, h., amirthalingam, m., panigrahi, s.k., microstructure dependent electroplastic effect in aa 6063 alloy and its nanocomposites, journal of materials research and technology, 2021, 12, pp. 2185-2204. 7. bock, e.m., whitley, j.h., “fretting corrosion in electrical contacts”, electrical contacts, 1974, illionis institute of technology, chicago, 1974, pp. 128. 8. braunovic, m., fretting damage in tin-plated aluminium and copper connectors, ieee transactions on components hybrids and manufacturing technology 12(2):215 – 223, 1989, doi:10.1109/33.31426. 9. wert, c.a., thomson, r.m. physics of solids, 2nd edition, mcgraw-hill book company, new york, 1970. 10. otsuka, t., hirai, h., ono, j. “crimping technology of alumium wire for automotive wire harness,” auto networks technologies ltd, tokyo, 2012. 11. yasuda, k., umemura, s., aoki, t. “degradation mechanisms in tinand gold-plated connector contacts,” ieee transactions on components, hybrids, and manufacturing technology, 1987, 10(3), 456-462. http://www.cableharnessing.co.uk/ https://www.sciencedirect.com/science/article/pii/s2238785421003392#! https://www.sciencedirect.com/science/article/pii/s2238785421003392#! https://www.sciencedirect.com/science/article/pii/s2238785421003392#! https://www.sciencedirect.com/science/article/pii/s2238785421003392#! https://www.sciencedirect.com/science/article/pii/s2238785421003392#! https://www.sciencedirect.com/science/article/pii/s2238785421003392#! https://www.sciencedirect.com/science/journal/22387854 https://www.sciencedirect.com/science/journal/22387854 https://www.researchgate.net/profile/milenko-braunovic https://www.researchgate.net/journal/ieee-transactions-on-components-hybrids-and-manufacturing-technology-0148-6411 https://www.researchgate.net/journal/ieee-transactions-on-components-hybrids-and-manufacturing-technology-0148-6411 http://dx.doi.org/10.1109/33.31426 hazra and singh (2022): international journal of engineering materials and manufacture, 7(1), 13-24 24 12. rolin, t. d. et al. salt spray test to determine galvanic corrosion levels of electroless nickel connectors mounted on an aluminium bracket. 2014. 13. fujiwara, h. a patent for manufacturing methods to produce automotive power cables with ni-layer.u.s. patent no. 20030111256. 2003. 14. cheerful, e. a method and compound for contacting an aluminium cable with a metallic,tinned contact clamp. d.e.patent no. 10223397a12004. 15. vogt, s., thalmeier, m., rill, d., kindersberger, j. “high voltage aluminium connector (leiko),” münchen, germany, 2013. 16. braunovic, m., izmailov, v., novoselova, m. “a model for life time evaluation of closed electrical contacts,” in proceedings of the fifty-first ieee holm conference on electrical contacts, 2005, doi: 10.1109/holm.2005.1518247. 17. alloy data: aluminium die casting alloys in die casting aluminium selection guide, pp. a-3-1-97–a-3-3-97, published by nadca. 18. wang, l., makhlouf, m., apelian, d. aluminium die casting alloys: alloy composition, microstructure, and properties-performance relationships, international materials reviews 1995, 40(06), 221-238. 19. hamedi, e. electrical connection for aluminium conductors in automotive applications prestudy of available solutions for electrical connection methods of aluminium cables, inom examensarbete materialdesign, avancerad nivå, 30 hp, stockholms verige 2017. 20. yu, m. aluminium cables in automotive applications, prestudy of aluminium cable uses in scania products & failure analysis and evaluation, examensarbete inom materialteknik, avancerad nivå, 30 hp stockholm sverige 2016. 21. talat lecture 1254: fatigue in al casting alloys: metallurgical aspect, by f. bonollo and r. tovo, european aluminium association, 1999. 22. jaglinski, t., lakes, r. creep behavior of al-si die-cast alloys, journal of engineering materials and technology, transactions of the asme, 2004, 126, 378-383. 23. zamani, m., seifeddine, s., anders e.w. j. effects of microstructure and defects on tensile and fracture behaviour of a hpdc component: potential properties and actual outcome of an ac-44300 alloy, light metals, tms (the minerals, metals & materials society), 2014, 1077-1083. https://doi.org/10.1109/holm.2005.1518247 international journal of engineering materials and manufacture (2020) 5(3) 76-84 https://doi.org/10.26776/ijemm.05.03.2020.02 s. islam and n. evans school of information technology and mathematical sciences university of south australia adelaide, sa 5000, australia e-mail: islsy004@mymail.unisa.edu.au reference: islam, s. and evans, n. (2020). key success factors of prince2 project management method in software development project. international journal of engineering materials and manufacture, 5(3), 76-84 key success factors of prince2 project management method in software development project saiful islam and nina evans received: 28 may 2020 accepted: 06 july 2020 published: 30 july 2020 publisher: deer hill publications © 2020 the author(s) creative commons: cc by 4.0 abstract project management uses many tools, techniques, and methodologies in project development. prince2 methodology set documentation which must be tailored to suit the occasion project. since software projects may often fail due to lack of well-structured project management method, it is necessary to identify the key success factors of prince2 method in software development project. the purpose of this research study is to identify key success factors of prince2 project management method in software development project. the researcher undertakes a case study in an organisation where software project is implemented in prince2 project management method. data has been collected from questionnaires and face-to-face interviews. documents review, and observation techniques were used as secondary data collection sources. the researcher has conducted template analysis with interview data and excels analysis with the questionnaires data. the researcher has then triangulated the data to get authentic and accurate findings. 20 factors have been identified as key success factors in this research study such as defined roles & responsibilities, scope management, manage by stages, well planning, top management support, time management, risk management, monitor project progress, change management, communication management, quality management, project team competency, managing product delivery, cost management, learn from experience, prioritizing task, assign work to right person, benefit realisation and being agile. key words: software development life cycle (sdlc), project management, projects in controlled environment (prince2), key success factor. 1 introduction since software development become under diverse and increasing pressure as technology has been changed, markets become more sophisticated and global competition raised, software vendors require well-organised project management in each area for information quality, system quality and user satisfaction (saad et al 2012). time, cost, quality, scope, risk and benefits of a project are managed by well-organised project management approach (commerce 2009). while prince2 project management methodology provides well-structured project management, many project managers often say that prince2 method involves complex processes which are time consuming and it is difficult for project managers to complete project within time frame and budget particularly in software development company. on the other hand, software projects may often fail due to lack of well-structured project management method (kruger & rudman, 2013). software projects are associated with risks. organisations who fail to manage the inherent risk associated with change, innovation and management of projects often end up with high proportion of project failures (whyte et al, 2016). change has become a way of life for organisations that need to remain effective and competitive in order to thrive. in order to manage these issues, software development projects have to be developed in a controlled environment (kruger & rudman, 2013). in this context, prince2 project management method plays a vital role in software development project. but it is necessary to identify the key success factors of prince2 project management method in software development project. but no research has been done yet on key success factors of prince2 project management method implementation in software development project. without knowing key success factors of software projects have less concentration on communication, team, project management and product related factors. the royal melbourne institute of technology (rmit) (a university in victoria) is reporting major problems with their implementation of erp system because of not knowing the key success factors (nielsen 2002). particularly it is important to know key success key success factors of prince2 project management method in software development project 77 factors of software project that is implemented in prince2 method as prince2 is a structured project management methodology, different levels of management are involved in the project and there was no such key success factors model was developed for software project that is i mplemented in prince2 method. hence, the purpose of this research is to evaluate key success factors (ksfs) for software development projects in prince2 method. this research is useful for organizations working on software projects. the project managers working in the industry can get benefit from the mentioned key success factors by concentration on them while planning and executing software projects. key success factors (ksfs) identify the most important issues/areas that need attention to perform properly for the business to flourish (majarian & putnam, 2015). if they are not performed well, it is unlikely that the mission, objectives, or goals of a business or project will be achieved. these factors can be used internally for assessment or prediction of success in a business or project. the ksfs are firm specific and prioritizing them can help managers to be aware of important aspects of success. therefore, this research project aims to identify key success factors of prince2 project management method in software development project. 2 an overview of prince2 and sdlc a project is managed in six aspects such as scope management, time management, cost management, quality management, risk management and benefit management (schwalbe, 2011). a prince2 has seven principles, seven themes and seven processes to manage, direct and deliver the project (commerce, 2009). apart from this, a sdlc project has six phases including system planning, system analysis, system design, system development, testing and deployment (shelly & rosenblatt, 2012). the activities of these six phases are accomplished within prince2 project management framework. 2.1 aspects of project management project management applies knowledge, skills, tools and techniques to project activities to meet the requirements of the project (atkinson, 1999). according to commerce (2009), five process groups are comprised of project management processes. these are initiating, planning, executing, monitoring, and controlling and closing (commerce, 2009). the project is accomplished by application of these processes that executed by project managers. according to project management institute (2008), there are some specific tasks to manage a project including identifying requirements, addressing the various needs, concerns and expectations of the stakeholders as the project is carried out and planned, balancing the competing project constraints such as scope, quality, schedule, budget, risk and resources. project management institute (2008) states that project management knowledge areas consist of project integration management, project scope management, project time management, project cost management, project quality management, project human resource management, project communication management, project risk management and project procurement management. according to schwalbe (2011), a project is managed in six aspects such as scope management, time management, cost management, quality management, risk management and benefit management. a prince2 project is also managed in six aspects including scope management, time management, cost management, quality management, risk management and benefit of the project (commerce, 2009). since the scope of this research study is prince2 project management method in software development, these six aspects are discussed in this dissertation. 2.2 principles of prince2 method prince2 is an integrated framework of processes that addresses the planning, delegation, monitoring and control of all these six aspects of project performance (kruger & rudman, 2013). according to commerce (2009), there are seven prince2 principles that can be summarised as continued business justification, learn from experience, defined roles and responsibilities, manage by stages, manage by exception, focus on products and tailor to suit the project environment. a prince2 project must have continued business justification (commerce, 2009). the project must have justifiable reason to start and the justification should remain valid throughout the life of the project (commerce, 2009). the justification is documented in a business case and approved. prince2 project teams learn from previous experience by seeking lessons, recording, and acting upon throughout the life of the project. project teams review previous or similar projects whether they can apply the lessons that learned from those projects. this learning process continues as the project progresses and closes. roles and responsibilities within organisation structure in a project facilitate to engage the business, user, and supplier stakeholder interests. a prince2 project must have that kind of defined and agreed roles and responsibilities within organisation structure (commerce, 2009). the project should be planned, monitored, and controlled on a stage-by-stage basis. prince2 method divides the project into several management stages, have a high-level project plan and have a detailed stage plan (kruger & rudman, 2013). the project has defined tolerance limits for each project objective including time, cost, quality, scope, risk and benefit to establish limits of delegated authority (commerce, 2009). prince2 project focuses on the definition and delivery of products including quality requirements. finally, prince2 project is tailored to suit the project’s environment, size, complexity, importance, capability, and risk (commerce, 2009). 2.3 prince2 themes all the themes of prince2 are addressed continually in such way which provides aspects of project management (commerce, 2009). project managers perform the role in a professional manner with the help of these themes (too & weaver, 2014). according to commerce (2009), there are seven themes in a prince2 project including business islam, s. and evans, n. (2020): international journal of engineering materials and manufacture, 5(3), 76-84 78 case, organisation, quality, plans, risk, change and progress. organisation is an important theme for a project to have potential value. business case enables organisational idea to be developed into a viable investment proposition. business case also enables project management team to maintain the objective of the organisation throughout the project (commerce, 2009). the roles and responsibilities in the prince2 project management team are defined and agreed by organisation theme. quality theme describes how the outline is developed so that project management team can deliver required products based on the quality attributes (schwalbe, 2011). prince2 projects progress based on a series of approved plan. projects entail risk. risk theme enables project team to manage all uncertainties of the project in its plans. change theme enables project management team to manage change (whyte et al, 2016). this theme addresses how project team assess and act upon issues including unanticipated general problems, requests for change or instances of quality failure that have a potential impact on the baseline of the project. the progress theme explains the decision-making process for approving plans, the monitoring of actual performance and the development process if events do not go per plan (commerce, 2009). 2.4 prince2 processes prince2 process is a structured set of activities defined to secure a specific objective. according to commerce (2009), “prince2 has seven processes that give the set of activities required to direct, manage, and deliver a project successfully”. these processes are starting up a project, directing a project, initiating a project, controlling a stage, managing product delivery, managing a stage boundary, closing a project. the objective of the starting up a project process is to justify business for initiating the project (bentley, 2015). this process ensures that all the necessary authorities exist for initiating the project and sufficient information is available to define and confirm the scope of the project. the key activities of starting up a project are to appoint the executive and the project manager, capture previous lessons, design and appoint the project management team, prepare the outline business case, select the project approach and assemble the project brief and plan the initiation stage (commerce, 2009). the activities within the directing a project process are project-board-oriented and are to authorise initiation, authorise the project, authorise a stage or exception plan, give ad hoc direction and authorise project closure. the activities within the initiating a project process are project-manager-oriented and are to prepare the risk management strategy, prepare the configuration management strategy, prepare the quality management strategy, prepare the communication management strategy, set up the project controls, create the project plan, refine the business case and assemble the project initiation documentation (commerce, 2009). the purpose of the controlling a stage process is to assign work to be done, monitor such work, deal with issues, report progress to the project board, and take corrective actions to ensure that the stage remains within tolerance. controlling a stage activities are project-manager-oriented and comprise authorising a work package, reviewing work package status, receiving completed work packages, monitoring and reporting stage status, highlighting report, capturing and examining issues and risks, escalating them and taking corrective action. the objective of the managing product delivery process is to ensure that work on products allocated to the team is authorised and agreed, team managers, team members and suppliers are clear as to what is to be produced and what is the expected effort, cost or timescales (commerce, 2009). team managers ensure that the planned products are delivered to expectations and within tolerance (bentley, 2015). this process ensures that accurate progress information is provided to the project manager at an agreed frequency to ensure that expectations are managed. the activities within the managing product delivery process are team-manager-oriented that are to accept, execute and deliver a work package. the objective of the managing a stage boundary process is to enable the project board to be provided with enough information by the project manager so that it can review the success of the current stage, approve the next stage plan, review the updated project plan and confirm continued business justification and acceptability of the risks (commerce, 2009). the activities within the managing a stage boundary process are project-manager-oriented that are to plan the next stage, update the project plan and the business case, report stage end and produce an exception plan (bentley, 2015). the objective of the closing a project process is to provide a fixed point at which acceptance for the project product is confirmed, and to recognise that objectives set out in the original project initiation documentation have been achieved and that the project has nothing more to contribute (commerce, 2009). the activities within the closing a project process are projectmanager-oriented that are to prepare planned and premature closure, hand over products, evaluate the project and recommend project closure (bentley, 2015). 2.5 systems development life cycle (sdlc) the systems development life cycle (sdlc) is a term used in systems engineering, information systems and software engineering to describe a process for planning, creating, testing, and deploying an information system. the systems development life-cycle concept applies to a range of hardware and software configurations, as a system can be composed of hardware only, software only, or a combination of both (shelly & rosenblatt, 2012). an sdlc aims to construct high quality systems that meet or exceed customer expectations, based on customer requirements, by delivering systems which move through each clearly defined phase, within scheduled time-frames and cost estimates. computer systems are complex and often link multiple traditional systems potentially supplied by different software vendors. to manage this level of complexity, a number of sdlc models or methodologies have been created, such as ‘waterfall’, ‘spiral’, ‘agile software development’, ‘rapid prototyping’, ‘incremental’ and ‘synchronise and stabilise’ (kay, 2002). in project management a project can be defined both with a project life cycle (plc) and an sdlc, during http://en.wikipedia.org/wiki/systems_engineering http://en.wikipedia.org/wiki/information_systems http://en.wikipedia.org/wiki/software_engineering http://en.wikipedia.org/wiki/software_engineering http://en.wikipedia.org/wiki/waterfall_model http://en.wikipedia.org/wiki/spiral_model http://en.wikipedia.org/wiki/agile_software_development http://en.wikipedia.org/wiki/software_prototyping#throwaway_prototyping http://en.wikipedia.org/wiki/incremental_development http://en.wikipedia.org/wiki/project_management http://en.wikipedia.org/wiki/project_life_cycle key success factors of prince2 project management method in software development project 79 which slightly different activities occur. the project life cycle encompasses all the activities of the project, while the systems development life cycle focuses on realising the product requirements (shelly & rosenblatt, 2012). according to shelly & rosenblatt (2012), the sdlc adheres to important phases that are essential for developers, such as planning, analysis, design, development, testing and deployment. 3 research design software development project is managed by well-structured project management method. each phase of software development including system planning, system analysis, system design, system development, testing and deployment is managed and controlled by project management method such as prince2. success of a project depends on how project team complete project within scheduled time, estimated cost, defined scope, expected quality and how they manage risk and benefit realisation. prince2 provides well-structured project management framework to manage software project in these six aspects. if a project fails to satisfy any one of these aspects, the project will face the risk of failure. so the key success factors of software project lie on project management method including prince2 that manage project in six aspects in every phase of software development life cycle. therefore, this research aims to prepare questionnaires and interview questions on project management method, software development phases and six aspects of the project. project time management, project cost management, project scope management, project quality management, project risk management and project benefit management are kept in grey box. these activities are performed in each phase of software development life cycle. this relationship is shown in theoretical framework with arrow symbol in figure 1. questionnaires were derived from various factors of principles, themes and processes of prince2 project management methodology and the participants of the case study were asked how these factors were worked in system planning, system analysis, system design, system development, testing and deployment of software development life cycle (sdlc). analysis of the respondents’ answers determines the key success factors. figure 1: theoretical framework of research design http://en.wikipedia.org/wiki/project http://en.wikipedia.org/wiki/requirement http://en.wikipedia.org/wiki/planning http://en.wikipedia.org/wiki/analysis http://en.wikipedia.org/wiki/design islam, s. and evans, n. (2020): international journal of engineering materials and manufacture, 5(3), 76-84 80 4 case study selection and background the researchers have been conducted in a software development company in india. they are a passionate team with a vast experience in financial domain and it sector especially in the lending vertical. the researchers have selected this company for the case study because they implement full cycle of software development managed by prince2 project management methodology. the researchers have selected loan management system integrated with accounting system and document management system which was their most successful and vast project where 45 team members worked. loan management system deals with loan application process, loan approval, loan disbursement, loan rescheduling and loan repayment. the accounting system deals with general ledger, accounts receivables and accounts payables. the loan management system is developed in java and oracle and run in web logic application server which is integrated with sap financial management system. the customers can access the system through both computer and mobile apps. there were 3 members in corporate management, 5 members in project board including executive, senior user and senior supplier, 1 project manager, 5 members as team manager, 29 members in development team and a project assurance officer and project support officer. the project was fully developed in two years. the project was developed in six phases including system planning, system analysis, system design, system development, testing and deployment. the other reason is that as the researchers were allowed to access data and were able to get detailed and in-depth interviews and questionnaires of the loan origination system development in this company. the loan origination system can perform loan quotation, loan application, loan approval, loan disbursement and loan collection in 220 branches of the client’s organisation. the system is integrated with sap accounting system and document management system. document management system captures the documents which are sent by customers during loan application process and save in the database. the documents can be retrieved by loan officers any time for the purpose of loan approval, disbursement and collection. the objectives of the project are: faster and more efficient payment collection processing, reduce human errors and potential leakages in collection, formal records for payments and loans, centralised and manage payment and collection processing, centralised and manage loan monitoring accounting system, centralised and manage loan application, real-time business control and management, real-time personnel tracking and planning, electronic payment collection processes and loan monitoring accounting system. the various core processes that are available within sap financial management system are: basic settings, master data, document control, posting control, clearing, cash journal, special g/l transactions, parking documents, automatic payment, correspondence, interest calculation, reporting in financial accounting, closing activities, receivables & payables, profit and loss etc. 5 results and discussions the data collected from interview have been qualitatively analysed by template analysis. once the initial template is created, the themes have been organized and modified into a smaller number of higher-level codes to develop the final template which are key success factors found by interview. the data collected by questionnaires have been quantitatively analysed and the higher ranked data are key success factors found by questionnaires. then data triangulation technique has been applied by comparing the findings of key success factors from questionnaires data with the findings of key success factors from interview data. data found from documents review and observation techniques have also been considered. once the findings from questionnaires with findings from interview are crosschecked, the overall key success factors in this research project have been found. total 20 factors have been identified as key success factors by data triangulation process. some of the factors are identified in all phases of sdlc including planning, analysis, design, development, testing and deployment and some of the factors are identified as key success factors in specific phases. the key success factors (ksf) that were identified are discussed below: defined roles and responsibilities: defined roles and responsibilities is a key success factor in this research study. this is a key success factor in entire software development life cycle including system planning, system analysis, system design, system development, testing and deployment. roles and responsibilities of business, user and supplier stakeholders were defined across the organisation according to objective of the project. each person’s knowledge, skills, experience, authority, credibility, commitment and availability are included to define their roles and responsibilities in the project that have great impact on the entire project. the project board’s roles and responsibilities are defined in such way that they provide overall direction. the project board is accountable for the success of the project. the project manager’s roles and responsibilities are defined to execute day-to-day management of the entire project. team member’s role and responsibilities are defined to deliver project product within defined quality, scheduled time and estimated budget. the project board was aware of their roles and responsibilities in this research project and directed the project efficiently. the project board regularly monitored the project and provided support for any requirements to make the project successful. the project manager called meeting to the team managers and members to monitor the progress of the project. the project manager was aware of the timeline of the project and maintained the schedule. the project manager controlled budget as a part of his responsibilities. as defined roles and responsibilities, the project manager identified and managed risk, delivered work at acceptable standard. he was aware of the benefit of the project. the project manager defined the scope of the project and distributed the work to the team manager properly according to agreed roles and responsibilities. manage by stages: manage by stages is a key success factor in this research study. this is a key success factor in entire software development life cycle including system planning, system analysis, system design, system key success factors of prince2 project management method in software development project 81 development, testing and deployment. this project was monitored, planned and controlled on a stage-by-stage basis. manage by stages provided the project board with control point with major intervals in entire project. the project manager updated project plan and business case that was vital for the project to be successful. at the end of each stage, the project manager produced stage end report and planned for the next stage. according to commerce (2009), “breaking the project into a number of stages facilitated the project team control over project in the extent of business priority, risk and complexity involved”. breaking the work package into a number of small packages enabled the project manager authorised work package to the right person. this helped project manager to receive completed work package on time. it was easier for project manager to review project status, capture and examine risk and take corrective action for any issue. this provided project manager control over project. quality management: quality management is a key success factor in this research study. this is a key success factor in entire software development life cycle including system planning, system analysis, system design, system development, testing and deployment. quality management provides project team coordinated activities to direct and control the project in the context of quality. a quality management process provides complete set of quality planning, quality control and quality assurance. quality management process of this project ensured that all necessary tasks of planning, analysis, design, development, testing and deployment are effective and efficient to satisfy the objective and performance of the project. quality management process of this project ensured that project meet stakeholder’s needs and expectations which was key for this project to be successful. time management: time management is a key success factor in this research study. although analysis phase was not completed within time frame due to addition of new requirements in the project scope during analysis phase, the project completed within time line as the project team was able to complete other phases before deadline and recovered delay in analysis phase. an ineffective time management would have had a negative impact on the project. any deviation from the project schedule could have influenced the cost and scope of the project. ineffective time management can lead the project to unsuccessful. the project manager was aware of timeline of the project and maintained the schedule. team managers delivered their job within deadline. so, an effective time management played a vital role in this project to be successful. scope management: scope management is a key success factor in this research study. this is a key success factor in entire software development life cycle including system planning, system analysis, system design, system development, testing and deployment. scope management process includes plan scope management, collect requirements of stakeholder’s needs, define scope which is detailed description of the project and product, create work breakdown structure that subdivide project deliverables and project work into smaller and more manageable components, verify scope that formalise acceptance of the completed project deliverables and control scope that monitor the status of the project and product scope and manage changes to the scope baseline. poor scope management can cause scope creep that may lead the project unsuccessful. the project manager controlled the scope in this research project throughout the life cycle of the project. monitor project progress: monitor project progress is a key success factor in this research study. this is a key success factor in entire software development life cycle including system planning, system analysis, system design, system development, testing and deployment. project needs to be monitored regularly otherwise it could go offtrack. project manager should keep the project on-track to make the project successful. project manager has to monitor the project budget, track the project scope, watch the project schedule and oversee the project resources. in this research study, the project manager regularly monitored the project including budget, schedule, scope and resources. therefore, he was able to provide support for any requirements. the project manager regularly called meeting to the team managers and members to monitor the progress of the project and compared the level of achievement with plans. well planning: well planning is a key success factor in this research study. this is a key success factor in entire software development life cycle including system planning, system analysis, system design, system development, testing and deployment. planning is a major important process and a project needs to well plan process to be successful. this research project had well planning of scope definition, project definition, task definition, task sequencing, duration estimating, schedule development, cost estimating, cost budgeting and plan integration. in addition, some facilitating processes were performed sporadically throughout the course of project planning including quality planning, role and responsibility definition, organisation planning, project staffing, communication planning, risk identification, risk assessment, solution development, procurement planning, solicitation and procurement. the project manager reviewed plans and options against future situations. the project manager updated project plan and produced exception plan. change management: change management is a key success factor in this research study. this is a key success factor in entire software development life cycle including system planning, system analysis, system design, system development, testing and deployment. any change in project impacts on project, task, process, structure, or job function. project management team manage change by using tools and techniques within the project. a prince2 project identifies, assesses and control any potential and approved changes to baseline. all issues and changes that could affect the project’s agreed baseline were identified, assessed and either approved, rejected or deferred in this research project. configuration management was active to create, maintain and control change of configuration throughout the life cycle of the project. the project used configuration management strategy, configuration item records, product status accounts, daily log, issue register and issue reports to establish and maintain the project’s islam, s. and evans, n. (2020): international journal of engineering materials and manufacture, 5(3), 76-84 82 controls for issues, changes and configuration management. configuration item records and daily log were maintained regularly. product status accounts and issue register were updated regularly. in addition, project team generated issue reports regularly. this procedure provided much improved performance and enhanced innovation to the product and reduces project cost. managing product delivery: managing product delivery is a key success factor in this research study. this is a key success factor in entire software development life cycle including system planning, system analysis, system design, system development, testing and deployment. the function of the managing product delivery is to confirm that the team is allocated authorised and agreed work package. team managers, team members and suppliers understand what they need to produce and what is the expected effort, cost or timescale. the planned product should be delivered according to expectations and within tolerance. the team provide accurate progress information to the project manager at an agreed frequency to ensure that expectations are managed. in this research study, the team manager ensured that product was developed and delivered to the project by accepting and checking authorised work package from the project manager. interfaces identified in the work package were maintained. team manager developed a team plan for this assigned work package and ensured that product was developed in accordance with development method specified in work package. in addition, team manager ensured that product met its quality criteria through the quality management process specified in product description. the team manager obtained approval from appropriate authorities for completed product. while delivering the product to the client, the project manager ensured that host site was able to support the product when project was disbanded. top management support: top management support is a key success factor in this research study. this is a key success factor in system planning, system analysis and deployment phase and overall this a key factor to project success. a prince2 project is successful when project board is aware of their and responsibilities and direct the project efficiently, monitor project regularly and provide support for any requirements. they have to provide management authority and control to remain the project viable. in this research study, the project board played an important role in system planning, system analysis and deployment phase. corporate management also adequately supported this project. the project board directed the project in system planning and analysis phase and regularly monitored the project. they provided necessary authorities to initiate the project. they gave new requirements during system analysis phase. they provided management authority and control to continue the project. the project team continued the project with this authority. the project board played an important role in deployment phase when the product was delivered to host site. they provided authority to deliver the project’s product and close the project. risk management: risk management is a key success factor in this research study. this is a key success factor in system planning, system analysis and system design phase and overall this a key factor to the project success. risk management process involves identifying and assessing risks, planning and implementing risk responses. risks should be identified, assessed and controlled for effective risk management. a risk management strategy should be developed to explain how risk management will be embedded in the project management activities. risk management provides information to project management so that project team can make informed decisions on issues critical to project success. in this research study, risk was identified, assessed and controlled properly. risk management strategy was prepared in planning phase. all risks were identified, assessed and controlled in planning, analysis and design phase. assessing and managing risks is the best weapon to make the project successful. there was no risk involved in development, testing and deployment phase. overall risk management is a key success factor in prince2 project in software development life cycle. communication management: communication management is a key success factor in this research study. this is a key success factor in entire software development life cycle including system planning, system analysis, system design, system development, testing and deployment. effective communication management process ensures timely and appropriate generation, collection, distribution, storage, retrieval and ultimate disposition of project information. in this research study, project manager communicated team members and other stakeholders to the project both internal and external and created a bridge between team members and other stakeholders including different levels of expertise to make a transparent communication to share their knowledge, skill and information which was key to project success. project team competency: project team competency is a key success factor in this research study. this is a key success factor in system planning, system design, system development and deployment phase and overall this a key success factor for this project. the primary requirement of a project team competency is to have a competent project manager. a project manager should be a project champion in order to make the project successful. in this research project, the project manager had general management skills including leadership. he was able to provide direction, vision, mentor team members, sound judgment, issue and conflict resolution, effective decision, communication, and team building. he had project management skills including project management tools and techniques. he had proven industry experience. he was strategic in approach and provided clear definition of requirements and time table. he was able to deliver project within time and budget. he managed the team to bring success. he managed project scope, quality and risk. he was organised and efficient in work processes. he was key to make this project successful. the other team members were competent particularly they were technically sound. their technical competencies were vital in planning, design, development, and deployment phase. learn from experience: learn from experience is a key success factor in this research study. this is a key success factor in system planning, system analysis, system design, system development and testing phase and overall this is a key success factors of prince2 project management method in software development project 83 key factor for this project to be successful. lessons should be sought, recorded, and acted upon throughout the life of the project to make the project successful. these lessons are helpful while project progressing. in this research study, the project team developed similar project before. they learnt lessons from their previous experience which was key factor for this project to be successful. assign work to right person: assign work to right person is a key success factor in this research study. this is a key success factor in entire software development life cycle including system planning, system analysis, system design, system development, testing and deployment. picking wrong person for project task is a major reason for failure. in this research study, the project manager assigned work packages to right persons who were capable of doing that particular work package. as a result, the team members were able to complete their assigned packages within timeline at acceptable standard which led to this project successful. cost management: cost management is a key success factor in system planning phase. project cost management involves three processes including cost estimation, budget determination and cost control. cost estimation and budget determination processes were developed during system planning phase in this research study. project board decide whether they will continue the project or not that depends on budget. then cost was controlled according to budget. prioritising task: prioritizing task is a key success factor in system planning phase. project manager prioritises tasks during development of project schedule and the most important tasks are preferred to complete before less important tasks. in this research project, the project manager collected the list of all project tasks, identified urgency, assessed value, ordered the tasks by estimated efforts, and then prioritised the tasks. hence the project manager managed teamwork load and deadline of the tasks. although task prioritisation was done in planning phase, it had impact on the entire project to make this project successful. benefit realisation: benefit realisation is a key success factor in system planning and deployment phase. project benefit realisation management process provides output that are new products or services delivered by the project and the objectives are achieved once the project concludes. the successful completion of a project provides benefits that are the value created for project beneficiary. benefits can be tangible or intangible. benefit realisation management process involves identifying benefits, execute benefits management and sustain benefits realisation. in this research study, benefits were identified during planning phase which was key success factor. project team executed benefits management throughout the life cycle of the project. it was important that benefits were realised during deployment phase which was key to project success. this project sustained benefits realisation since the objectives of the project product are achieved and satisfied the stakeholder’s expectation. being agile: being agile is a key success factor found in system planning and system analysis phase. the project needed to adopt tools, processes and a mind-set of being nimble and deliver value as fast as possible and as reasonable as possible during planning and analysis phase. in addition, the project management team required to accept a certain level of uncertainty in planning phase and perform validation on ideas and concepts ahead of the decision to implement the project. tailor to suit the project environment: tailor to suit the project environment is a key success factor found in deployment phase. a prince2 project should be tailored to suit the project’s size, environment, complexity, importance, capability, risk and user satisfaction. the project manager reviewed the performance of the project against its baseline at the end of deployment phase. the project was fit for purpose. the project manager ensured that provision had been made to address all open issues and risks. the product was installed in environment of host site and the host site was able to support the product when project was disbanded as all complexity of the product was resolved. the performance of the product was at expected level and users were satisfied with the system. 6 relevance to other fields these key success factors can be applied to different sectors but the importance of the ksfs will be different for different sectors. these key success factors are applicable to industrial plant erection project that is implemented in prince2 project management method. 7 conclusions this study targets on the different dimensions of prince2 project management method in sdlc context to investigate its impact on the project to be successful and provides comprehensive understanding of its implementation on software development project. the main contribution of this research is identification of key success factors of prince2 method in software development projects. these factors are applicable to all project phases and are adaptable to different types of projects and companies. the key success factors are unique in nature as the functionalities of these factors are same in different projects. this research study provides theoretical contribution by enriching prince2 project management method literature as it provided a comprehensive insight to the key factors that are considered important for successful implementation of sdlc project. the findings can assist the it practitioners such as senior executive, project manager, team manager, team members and other stakeholders who are in charge of sdlc projects to better anticipate the future challenges of the sdlc project progression and how to subsequently manage them. these ksfs can be used as model of project management methodology. senior executives, project managers, team managers, team members and other stakeholders of the project can follow this model for successful implementation of the project. this study is based on a single case, it has limited generalisation of the research results. but the finding of this case study research can be valuable to software practitioners in other islam, s. and evans, n. (2020): international journal of engineering materials and manufacture, 5(3), 76-84 84 countries as well. it can also help senior executives, project managers and team managers to manage sdlc project more efficiently and effectively. the findings of the research can lead future project executives, project managers and team managers to practice better project management process including better planning, both short-term and longterm, leading to more predictable outcomes. the findings may provide an indication as to how an organisation should adopt a project management methodology or when they should implement a standard methodology. this study found several factors that can all contribute to the success of a sdlc project in prince2 project management method. it is expected that the theory and research findings presented in this thesis can aid the development of the software project in prince2 project management method. references 1. atkinson, r. 1999. project management: cost, time and quality, two best guesses and a phenomenon, it’s time to accept other success criteria. international journal of project management, 17(6), 337-342. 2. bentley, c. 2015. the prince2 practitioner: from practitioner to professional. devon, uk: florence production ltd. 3. commerce, gb. 2009. managing successful projects with prince2 (5th ed). london, uk: tso. 4. kay, r. 2002. system development life cycle, computer world, viewed 1 july 2018, <https://www.computerworld.com/article/2576450/app-development/app-development-systemdevelopment-life-cycle.html>. 5. kruger, w. & rudman, r. 2013. strategic alignment of application software packages and business processes using prince2, international business & economics research journal, 12(10). 6. majarian, t. & putnam, d. 2015. the most common reasons why software project fail, infoq, viewed 7 october 2018, <https://www.infoq.com/articles/software-failure-reasons>. 7. nielsen, jl. 2002. critical success factors for implementing an erp in a university environment: a case study from the australian hes, griffith university, queensland. 8. pmi. 2008. a guide to project management body of knowledge (fourth ed). pennsylvania, usa: project management institute, inc. 9. saad, s. ibrahim, a. asma, o. khan, m.s. & akhtar, j. 2012. a case study on implementation of prince2 methodology in automotive industry in malaysia (a preliminary study). international journal of scientific & engineering research, 3(4). 10. schwalbe, k. 2011. information technology project management (6th ed). uk: course technology. 11. shelly, g.b. & rosenblatt, h.j. 2012. systems analysis and design (9th ed). cengage learning. 12. too, e. & weaver, p. 2014. the management of project management: a conceptual framework for project governance. international journal of project management, 32(8), 1382-1394. 13. whyte, j. stasis, a. & lindkvist, c. 2016. managing change in the delivery of complex projects: configuration management, asset information and big data. international journal of project management, 34(2), 339-351. https://www.computerworld.com/article/2576450/app-development/app-development-system-development-life-cycle.html https://www.computerworld.com/article/2576450/app-development/app-development-system-development-life-cycle.html international journal of engineering materials and manufacture (2021) 6(1) 1-21 https://doi.org/10.26776/ijemm.06.01.2021.01 feng, z.j. 1 , lomeli, p. 2 , and hung, n.p. 1 1 texas a&m university, ms 3367, etid, college station, texas 77843, usa 2 keysight technologies, santa rosa, california, usa. e-mail: hung@tamu.edu reference: feng, z.j., lomeli, p., and hung, n.p. (2021). computer simulation of low frequency vibration in electrochemical machining. international journal of engineering materials and manufacture, 6(1), 1-21. computer simulation of low frequency vibration in electrochemical machining feng, z.j, lomeli, p., and hung, n.p. received: 08 september 2020 accepted: 14 december 2020 published: 30 january 2021 publisher: deer hill publications © 2021 the author(s) creative commons: cc by 4.0 abstract this research studies how particles transport between low frequency vibrating electrodes during electrochemical machining (ecm). the ansys fluent software was used to study the particle speed while the star ccm+ software was utilized to study particle interactions during vibration-assisted ecm process. a series of simulations were conducted to calculate the particle average flushing speed. collided particles either gained momentum or deflected their trajectories to accelerate in the flow of electrolyte. simulation results showed that the highest average flushing speed of 0.4 m/s was obtained at 40 hz vibration frequency and 10 µm vibration amplitude. such higher flushing speed of particles improved machining depth (material removal rate) and produced a sharper machined profile. experiment results confirmed that the maximum machining depth and minimum taper angle were obtained when vibrating the anodic workpiece at 40 hz and 10 µm amplitude. machining depth and ecm material removal rate had a positive correlation with the average flushing speed. a sharper ecm’ed profile was achieved since the taper angle was favorably reduced at high average flushing speed. keywords: low frequency vibration, simulation, pulsed current, electrochemical machining, particle flushing. 1 introduction electrochemical machining (ecm), based on the principle of controlled anodic dissolution, has been used to fabricate complex shapes from an electrically conductive component. this is particularly useful to shape engineering alloys that are difficult to be machined such as tool steels, tungsten carbides and superalloys. this ecm process does not induce any thermal or mechanical residual stresses nor subsurface defects below a workpiece, generates no burr, has no tool wear, yet could achieve an excellent surface quality when the parameters are suitable for electrochemical polishing. since we can eliminate secondary processes for deburring and stress relieving when applying ecm, this process would be a promising technique to machine/polish metallic materials if a decent material removal rate (mrr) can be achieved. ion transport mechanism affects the removal rate in ecm. the movement of ions is controlled by three mechanisms: migration, diffusion and convection [1]. a high mrr requires fast ion and by-product movement rates (i.e. by increasing one or all of the migration rate, diffusion rate and convection rate). researchers have attempted to utilize different techniques to improve these transport rates with different approaches by: − applying a high voltage to increase migration rates [2-4] − applying pulsed current instead of using direct current [5-8] − increasing high electrolyte flow rates to increase diffusion rates [3,9] − vibrating of either workpiece or electrode at low vibration frequency to increase the convection rates [8,1014] − applying ultrasonic vibration of electrode or via electrolyte [13,15,16]. convection is the most significant factor that affects ion transport mechanism. the classical faraday’s law and published literature have shown that a higher voltage/current resulted in high mrr; however, the resulted byproducts and excessive heat must be removed, for example, with a costly electrolyte pumping system. an alternative solution is to incorporate pulsed current and vibration into ecm to improve the electrolyte flow while reducing its temperature. researchers have attempted to vibrate either electrode or workpiece at different vibration frequency feng et al. (2021): international journal of engineering materials and manufacture, 6(1), 1-21 2 and amplitude to enhance the process instead of installing an expensive pump for high volume electrolyte flow rate that might deflect a fragile or low compliance workpiece. although vibration-assisted ecm has been studied experimentally, the mechanism on how low frequency vibration improves mmr is yet to be investigated. the objectives of this paper are to: i) simulate the flow of by-product in a horizontally vibrated ecm system. ii) study the by-product interaction between electrodes. iii) verify the simulation study with experimental data. 2. literature review many researchers have performed experimental investigation on the effect of vibration on ecm. in an ultrasonicassisted ecm system, controlled vibration of either the tool electrode or electrolyte to agitate the abrasives suspended in the electrolyte had shown to improve surface finish of the workpiece [16]. a study of the geometry and type of electrode that resulted in a well-polished surface (0.7 µm ra) was reported and the effect of ultrasonic energy was acknowledged [17]. this energy was also responsible for the removal of debris from the machining zone and creation of optimal hydrodynamic conditions that affected the surface layers [18]. hybridization ecm with low frequency tool vibration provided a positive and beneficial effect by changing the physical conditions in the inter-electrode gap (ieg). the variation of the gap pressure led to the removal of the sludge products and allowed renewal of the electrolyte in the machining gap. the reciprocal motion between the tool and the workpiece surface enhanced the circulation of the electrolyte through the interface to permit the use of higher current densities in order to improve the quality of the resultant surface and faster removal rate. in traditional vibration-assisted ecm the anode/cathode were vibrated in the vertical direction, thus the resulted by-products, that deposited on either electrode due to gravity, would hinder ion transport mechanism. a horizontal and vibrationassisted ecm was proposed as a remedial solution [6,16,19-21], in which a workpiece vibrated in the horizontal direction instead of the vertical direction to facilitate flushing of the resulted by-products. for ecm and its variant processes, it is essential to estimate the volume of anode material removal during a specific time. the mrr is a function of current density distribution in the ieg where varying electrical conductivity of the electrolyte exists. electrolyte velocity and pressure field in the ieg affected the gas bubble formation and temperature distribution, hence degraded the properties of electrolyte properties and current density [22]. as the consequence, any numerical simulation model would include mass, momentum, heat, electric charge and energy balance equations [23,24]. due to the non-contact nature of the ecm process, it was essential to develop a simulation model to predict the anodic profile. the first electrode shape change simulation model was based on analytical techniques. an ecm tool design was suggested by using the “sine rule” [1]. this rule can be used to obtain an approximate shape but it failed when the tools had sharp discontinuities due to the neglection of stray current effects and the assumption of parallel flux lines. other authors suggested to use an analytical direct computation for twodimensional (2d) ecm, represented the workpiece by fourier’s series and validated their models with experimental work [25], or utilizing finite element method for the 2d computation of mrr in ecm [26,27]. the latter model took the effects of simultaneous changes in the electrolyte flow speed and temperature rise into consideration. numerical simulation of three-dimensional (3d) electrode shape changes obtained during the ecm processes based on the “marker” method was also proposed [28]. a complex 3d structure was fabricated by pulsed electrochemical micromachining (pecmm) using ultrashort pulses; the effect of unsteady phenomena in electrical double layer on final anode shape also included in this study [29]. numerical simulation of the ecm process included the temperature effects was studied in other investigations and the temperature distribution was found to have an influence on the shape of the anode [23,24]. for better accuracy and simplification of tool design, a small yet stable ieg (by reducing the nonuniformity of the electrolyte conductivity) was required. commercial software package was also used to predict the final anode shape [30]. a review of mass transfer issues and other problems associated with the ecm process was published [31] and the numerical modeling of the ecm process considering the hydrodynamics involved in the process was also studied [32,33]. the final anode shapes resulting after the ecm using a triangular shaped cathode and curved surface were modeled in these studies. another model was developed to predict the variation of gap in the ecm process using pulsed current with a stationary electrode and rotating workpiece. the model predicted the gap, evolution of anodic profile, and estimation of resulted surface roughness value [34]. simulation of heat generation during ecm process and its effective dissipation using electrolyte flow was studied; it was found that a hollow cathode and pulse voltages effectively helped to control the heat generation [35]. published literature did not cover the interaction of discrete particles between electrode gap and the effect of vibration frequency on particle flow in an electrolyte. the following sections describe details of two simulations using fluent and star ccm+ software. the simulation results are then compared with experimental and published data. computer simulation of low frequency vibration in electrochemical machining 3 3. simulation of particle flow 3.1 governing equations a successful ecm process depends on the efficiency of debris flushing and effectiveness of fresh chemical replenishment to anodic surface. the motion can be modeled using newton’s second law of motion; the governing equations for translational motion of discrete particle 𝑖 with mass 𝑚𝑖 can be written as: 𝑚𝑖 𝑑𝑣𝑖⃗⃗⃗ 𝑑𝑡 = ∑ 𝐹𝑖𝑗 𝑐⃗⃗⃗⃗ 𝑗 + ∑ 𝐹𝑖𝑘 𝑛𝑐⃗⃗⃗⃗⃗⃗ ⃗ 𝑘 + 𝐹𝑖 𝑓⃗⃗⃗⃗ ⃗ + 𝐹𝑖 𝑔⃗⃗⃗⃗ ⃗ (1) where, 𝑣𝑖⃗⃗⃗ : translation velocity of particle 𝑖 respectively (m/s) 𝐹𝑖𝑗 𝑐⃗⃗⃗⃗ : contact force acting on particle 𝑖 by particle 𝑗 (n) 𝐹𝑖𝑘 𝑛𝑐⃗⃗⃗⃗⃗⃗ ⃗ : noncontact force acting on particle 𝑖 by particle 𝑘 or other sources (n) 𝐹𝑖 𝑓⃗⃗⃗⃗ ⃗ : particle-fluid interaction force on particle 𝑖 (n) 𝑚𝑖 : mass of particle 𝑖 (kg) 𝐹𝑖 𝑔⃗⃗⃗⃗ ⃗ : gravitational force (n). during an ecm process, a typical removal rate of an anode is 45.3 mm 3 /min which is much less than the electrolyte flow rate of 2.5 l/min (2,500,000 mm 3 /min) [6]. it is assumed that by-product particle interaction is insignificant, so single particle instead of multiple particles can be used in simulation of debris flushing. therefore, the contact force and non-contact forces between particles can be neglected, the equation (1) can be simplified to: 𝑚𝑖 𝑑𝑣𝑖⃗⃗⃗ 𝑑𝑡 = 𝐹𝑖 𝑓⃗⃗⃗⃗ ⃗ + 𝐹𝑖 𝑔⃗⃗⃗⃗ ⃗ (2) once the forces in equation (2) are known, this equation can be readily solved numerically to determine the particle's trajectory and velocity. 3.2 particle-fluid interaction forces in addition to the buoyance force, various particle-fluid interaction forces will be generated during the particles interact with surrounding fluid. for example, the translation of particle was driven by drag force and resisted by stagnant fluid. thus, particle-fluid interaction forces could be considered [36]. several forces can be implemented in discrete element method in computing fluid dynamics, for examples drag force, pressure gradient force, unsteady force, and lift forces [37,38]. 3.2.1. fluid-particle interaction drag force for an isolated sphere particle suspended in a fluid, the newton’s equation was used to determine the drag resistance force. the particle-fluid drag coefficient cd is dependent upon reynold’s number re in addition to liquid properties. there are three regions: the stoke’s law region, the transition region, and newton’s law region. two methods were used to determine the particle-fluid drag force. the first method based on empirical correlations for either bed expansion [39] or bed pressure drop experiment [40]. the other method based on numerical simulations at microscale, where the technique used the direct numerical simulation [41]. the latter method, although rational, was limited by the current computation capability. numerical studies had been applied to relatively simple systems. a study that systematically investigated and quantified the differences among these correlations was published [42]; the results revealed that these correlations with similar predictive capability, although their accuracy may differ. in this study, the coefficient was adopted from another study [43], and the fluid-particle interaction drag force are defined as: 𝐹𝑑⃗⃗⃗⃗ = 𝑚 𝑉𝐹⃗⃗⃗⃗ − 𝑉𝑝⃗⃗ ⃗ 𝜏𝑟 (3) 𝜏𝑟 = 𝜌𝑝𝑑𝑝 2 18𝜇 24 𝐶𝑑𝑅𝑒 (4) 𝑅𝑒 ≡ 𝜌𝐹𝑑𝑝|�⃗� 𝑝 − 𝑉𝐹⃗⃗⃗⃗ | 𝜇 (5) 𝐶𝑑 = 𝑎1 + 𝑎2 𝑅𝑒 + 𝑎3 𝑅𝑒 (6) where, 𝐹𝑑⃗⃗⃗⃗ : drag force (n) 𝑉𝐹⃗⃗⃗⃗ : fluid phase velocity (m/s) feng et al. (2021): international journal of engineering materials and manufacture, 6(1), 1-21 4 𝑉𝑝⃗⃗ ⃗ : particle flow speed (m/s) 𝜏𝑟 : particle relaxation time (s) 𝜌𝑝 : particle density (g/m 3 ) 𝑑𝑝 : particle diameter (m) 𝜇 : molecular viscosity of the fluid 𝐶𝑑 : drag coefficient 𝑅𝑒 : relative reynold number 𝜌𝐹 : fluid density (g/m 3 ) 𝑎1, 𝑎2, 𝑎3 : constants that apply over several ranges of 𝑅𝑒 3.3. fluid-particle flow modeling simulations using complementary software were employed in this study. the ansys fluent software was used in this study to simulate single particle flow while neglecting particle-particle interaction forces. the star ccm+ software was used to simulate multiple particles flow which can capture the particle-particle interaction in a fluid-particle flow system. in the discrete element method of computational fluid dynamics (cfd-dem), the primary phase (fluid) flow was determined by the cfd on a computational cell scale and the second phase (particles) was obtained by solving newton’s equations of motion [44]. the governing equation for fluid was the navier-stoke equation which was the same as the two-fluid method (tfm). the cfd-dem technique was used in this study because of its superior computational convenience and capability to capture the particle physics, such as, trajectories and velocities. in the cfd-dem approach, the modeling of particles flow was at individual particle level and the modeling of fluid flow by cfd was at computation cell level. at each step, the dem would give information, such as locations and velocities of individual particle, for the evaluation of porosity and volumetric fluid drag force in a computational cell. the cfd would then use these data to determine the fluid flow field which then yield the fluid drag forces acting on individual particles. incorporation of the resulting forces into the dem will produce information about the motion of individual particles for next time step. at each time step, the fluid-particle interaction forces on individual particles in a computational cell were calculated first, and then the values were added to produce the particle-fluid interaction force at the cell scale, as shown in following equations. 𝐹𝑛𝑒𝑤 = 𝐹𝑜𝑙𝑑 + 𝛼(𝐹𝑐𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑 − 𝐹𝑜𝑙𝑑) (7) 𝑄𝑛𝑒𝑤 = 𝑄𝑜𝑙𝑑 + 𝛼(𝑄𝑐𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑 − 𝑄𝑜𝑙𝑑) (8) 𝑀𝑛𝑒𝑤 = 𝑀𝑜𝑙𝑑 + 𝛼(𝑀𝑐𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑 − 𝑀𝑜𝑙𝑑) (9) where, 𝛼 : under-relaxation factor for particles α = 0.9 for transient flow simulation with unsteady particle tracking α = 0.5 otherwise 𝐹 : force 𝑄 : energy 𝑀 : momentum 3.4. particle flow simulations in interelectrode gap this study utilized high strength low alloy (hsla) steel in experiments to confirm the simulation trends. since the major composition of hsla steel is iron (97-99%), during ecm process several possible reactions may occur at the workpiece and electrode. the reaction is the dissolution of iron at anode. 𝐹𝑒 → 𝐹𝑒2+ + 2𝑒− (10) at the electrode, hydrogen and hydroxyl ions are produced: 2𝐻2𝑂 + 2𝑒 − → 𝐻2 ↑ +2𝑂𝐻 − (11) thus, the overall reaction of iron in ecm process is: 𝐹𝑒 + 2𝐻2𝑂 → 𝐹𝑒(𝑂𝐻)2 + 𝐻2 ↑ (12) the ferrous hydroxide fe(oh)2 may further react with water and oxygen to form ferric hydroxide fe(oh)3. 𝐹𝑒(𝑂𝐻)2 + 2𝐻2𝑂 + 𝑂2 → 4𝐹𝑒(𝑂𝐻)3 (13) in the ecm process, the anodic steel would form iron hydroxide by-products that need to be flushed away for effective process. such by-product was assumed to be spherical particles with dimensions to be measured experimentally. the ansys fluent was used to simulate how the single particle would move in vibration assisted computer simulation of low frequency vibration in electrochemical machining 5 pulsed ecm. while star ccm+ was used to simulate how multiple particles would flow and interact in vibration assisted pulsed ecm. the effects of vibration frequency and vibration amplitude on particle average flushing speed are presented in the result section. 3.4.1. single particle simulation figure 1 shows the horizontal tubular electrode and workpiece with origin at the tube center. the workpiece surface is on the vertical yo-zo plane and is separated from the tubular electrode at a small interelectrode gap. consider a byproduct particle p between the electrode and workpiece and its free-body diagram. the particle, forming an angle ϕ with the horizontal axis, is subjected to gravity force, buoyance force, and drag force in flowing electrolyte. due to the axisymmetric electrode, the drag force is in radial direction away from the tube center. the sum of forces in the radial direction is: 𝐹𝑟 = 𝐹𝑑 − (𝐺 − 𝐹𝑏) sin 𝜑 (14) where, ϕ : polar angle of the particle 𝐹𝑟 : total force along radial direction (n) 𝐹𝑑 : drag force (n) 𝐺 : gravity force (n) 𝐹𝑏 : buoyance force (n) figure 1 free-body diagram of a particle between horizontal electrodes since the solid particle is heavier and sinks in electrolyte, the buoyance force of this particle is always smaller than its gravity force. the minimum value of radial direction force equals to 𝐹𝑑 − (𝐺 − 𝐹𝑏) when 𝜑 = 𝜋 2⁄ , and the maximum value of this force equals 𝐹𝑑 + (𝐺 − 𝐹𝑏) when 𝜑 = 3𝜋 2⁄ . the top most location (at 𝜑 = 𝜋 2⁄ ) is the most difficult location for solid by-products to be flushed away (location a in figure 2a). in this study, location a will be taken as the simulation cell zone. the thickness of the electrode is 0.3 mm (figure 1) and the initial distance between workpiece and electrode is 0.3 mm, thus the simulation zone is a 0.3 mm × 0.3 mm square box (figure 2b). let the new coordinate xyz with origin at the lower left corner of the simulation zone. the electrolyte flow speeds from a pump were set to 2, 3, and 4 m/s and assuming the workpiece vibration follows a sine waveform: 𝑥 = −𝐴𝑣 sin(2𝜋𝑓𝑡) (15) let x be the coordinate of the workpiece, the negative sign means the workpiece movement towards the left and away from the origin. where, 𝑥 : location of workpiece relative to the fixed origin. 𝐴𝑣 : anode workpiece vibration amplitude (m) 𝑓 : vibration frequency (hz). p feng et al. (2021): international journal of engineering materials and manufacture, 6(1), 1-21 6 (a) (b) figure 2 (a) side view of electrode and workpiece and (b) enlarged view at the top most position in the beginning, the particle center was located at lower left corner (figure 2b) with particle initial velocity of 0 m/s. the boundary conditions for this study are listed in table 1. a simulation procedure stopped when the 𝑦-coordinate of particle center was larger than 0.3 mm, i.e. when the particle was flushed away from the electrode surface. table 1 boundary conditions in simulation variables values vibration frequency 𝑓 (hz) 20, 30, 40 vibration amplitude 𝐴 (µm) 5.0, 7.5, 10.0 flow speed (m/s) 2.0, 3.0, 4.0 table 2 corresponding vibration amplitude and frequency for maximum input power vibration frequency (hz) vibration amplitude (µm) 10 160.00 20 40.00 30 17.80 40 10.00 50 6.40 60 4.44 70 3.26 80 2.50 90 1.98 100 1.60 110 1.32 120 1.11 130 0.95 140 0.82 150 0.71 175 0.52 200 0.40 500 0.065 1000 0.016 5000 0.00064 10000 0.00016 to investigate the influence of the vibration frequency, vibration amplitude, electrolyte flow speed, particle size and particle locations on average flushing speed, a series of simulations were conducted: 1) the first simulation was used to build a relationship between experimental results and simulation results. three input levels for each variable were set ( 2) table 1). thus, total number of simulation run was 33 = 27. computer simulation of low frequency vibration in electrochemical machining 7 3) the second simulation was used to theoretically investigate the maximum flushing speed for the experimental system. the electrolyte flow speed was fixed at 4 m/s, and input current for vibration table was fixed at its maximum value (7 a), the corresponding vibration frequency and vibration amplitude will follow 𝐴𝑓2 = constant based on the specifications of system and are listed in table 2. 4) the third simulation was used to investigate the particle size on average flushing speed. the electrolyte flow speed was fixed at 4 m/s, vibration frequency was fixed at 40 hz, vibration amplitude was fixed at 10 µm and particle sizes range from 2 µm to 10 µm. the discrete phase formulation used by ansys fluent assumed that (i) the discrete phase (ecm by-product) was sufficiently diluted, and (ii) particle-particle interaction and the effects of the particle volume fraction on the continuous phase were negligible. this implied that the discrete phase must be present at a low volume fraction, typically less than 10-12%. 3.4.2. multiple particles simulation the star ccm+ was used to capture the particle-particle interaction in multiple particles fluid-particle flow system. figure 3 shows the flow domain in yz-plane with the length of wt = 300 µm and width la = 20 µm. four particle injection locations (label “i” and “ii” at coordinates z = ±5, y = 50 µm; and label “iii” and “iv” at coordinates z = ±5, y = 0 µm) were continuously injecting particles of 2 µm diameter into the electrolyte between the electrode and workpiece. figure 3 particle injection locations in fluid domain due to the limitation of the simulation software, a triangular wave was used as the approximation of the sine wave (figure 4). during a vibration cycle the workpiece moved at a constant speed of 4𝑓𝐴𝑣 before changing its direction. the by-product particles in ecm were released from the workpiece surface, and their releasing locations changed continuously. to simplify the simulation, a vibration cycle was divided into 20 equal time intervals within which the releasing locations were fixed. when the workpiece moved away from the electrode, particle releasing locations were the same as their initial locations from each time interval; in the reversed direction of workpiece, the particle releasing locations were the ending locations of each time interval. in this simulation, the vibration was fixed at 40 hz at 10 µm. the workpiece travel speed was 4𝑓𝐴𝑣 = 1600 µm/s, and the article releasing rate was 105 particles/s. the complete list of particles releasing locations for one vibration cycle is listed in table 3. (a) (b) figure 4 (a) sine wave (b) approximation of sine wave in star ccm+ feng et al. (2021): international journal of engineering materials and manufacture, 6(1), 1-21 8 table 3 coordinates of particle injection locations simulation time (ms) location i (µm) (𝑥1𝑗,𝑦1𝑗,𝑧1𝑗) location ii (µm) (𝑥2𝑗,𝑦2𝑗,𝑧2𝑗) location iii (µm) (𝑥3𝑗,𝑦3𝑗,𝑧3𝑗) location iv (µm) (𝑥4𝑗,𝑦4𝑗,𝑧4𝑗) 0 – 1.25 (1, 50, 5) (1, 50, -5) (1, 0, 5) (1, 0, -5) 1.25 –2.50 (-1, 50, 5) (-1, 50, -5) (-1, 0, 5) (-1, 0, -5) 2.50 – 3.75 (-3, 50, 5) (-3, 50, -5) (-3, 0, 5) (-3, 0, -5) 3.75 – 5.00 (-5, 50, 5) (-5, 50, -5) (-5, 0, 5) (-5, 0, -5) 5.00 – 6.25 (-7, 50, 5) (-7, 50, -5) (-7, 0, 5) (-7, 0, -5) 6.25 – 7.50 (-7, 50, 5) (-7, 50, -5) (-7, 0, 5) (-7, 0, -5) 7.50 – 8.75 (-5, 50, 5) (-5, 50, -5) (-5, 0, 5) (-5, 0, -5) 8.75 – 10.00 (-3, 50, 5) (-3, 50, -5) (-3, 0, 5) (-3, 0, -5) 10.00 – 11.25 (-1, 50, 5) (-1, 50, -5) (-1, 0, 5) (-1, 0, -5) 11.25 – 12.50 (1, 50, 5) (1, 50, -5) (1, 0, 5) (1, 0, -5) 12.50– 13.75 (3, 50, 5) (3, 50, -5) (3, 0, 5) (3, 0, -5) 13.75 – 15.00 (5, 50, 5) (5, 50, -5) (5, 0, 5) (5, 0, -5) 15.00 – 16.25 (7, 50, 5) (7, 50, -5) (7, 0, 5) (7, 0, -5) 16.25 – 17.50 (9, 50, 5) (9, 50, -5) (9, 0, 5) (9, 0, -5) 17.50 – 18.75 (11, 50, 5) (11, 50, -5) (11, 0, 5) (11, 0, -5) 18.75 – 20.00 (11, 50, 5) (11, 50, -5) (11, 0, 5) (11, 0, -5) 20.00 – 21.25 (9, 50, 5) (9, 50, -5) (9, 0, 5) (9, 0, -5) 21.25 – 22.50 (7, 50, 5) (7, 50, -5) (7, 0, 5) (7, 0, -5) 22.50 – 23.75 (5, 50, 5) (5, 50, -5) (5, 0, 5) (5, 0, -5) 23.75 – 25.00 (3, 50, 5) (3, 50, -5) (3, 0, 5) (3, 0, -5) 4. experiments to carry out this investigation, a unique laboratory horizontal vibration-assisted pulsed ecm system was developed (figure 5). this ecm system can control electrolyte flow, vibration frequency and amplitude, square pulsed dc output and programmable tool feeding. the system (table 4) included micro workpiece vibration unit, controllable pulsed dc system, programmable feeding system, electrolyte circulation system, and ecm cell with flash guard, etc. figure 5 front and top views of the laboratory horizontal ecm system computer simulation of low frequency vibration in electrochemical machining 9 table 4 ecm set-up components # components name # component name 1 labworks electrodynamic shaker 11 longer wt600-2j peristaltic pump 2 bearing housing 12 positive electric wire 3 linear bearing 13 everlast 255ext power supply 4 stainless steel shaft 14 negative electric wire 5 workpiece 15 fresh-electrolyte tube 6 electrode 16 longer wt600-2j peristaltic pump 7 3-axis velmex positioner 17 fresh-electrolyte container 8 granite table 18 shaft coupling 9 used-electrolyte container 19 ecm cell with flash guard housing 10 used-electrolyte tube 20 electrode holder a workpiece plate (#5) was mounted with workpiece surface in vertical direction and an electrode (#6) traveled horizontally into the workpiece with feed rate controlled by a computer-controlled positioner (#7). workpiece vibration was precisely generated by an electrodynamic shaker (#1). a pulsed power supply (#13) and two high-flowrate pumps (#11, 16) completed the ecm cell. in this study, the constant concentration of potassium bromide (kbr, 1mol/l) was selected as electrolyte. each experimental run was started with filtered electrolyte temperature in the range 21-29°c. temperature of the electrolyte was measured and recorded by omega hh374 4-channel data logger thermometer. electrolyte conductivity, measured before each run using the hannah hi 8733 conductivity meter, was in the range of 111-121 ms/cm. during experimental, fresh electrolyte was pumped from fresh electrolyte container (#16) and flowed inside the cathodic electrode (#4). after machining, used electrolyte in the ecm cell (#5) was pumped out and stored in used electrolyte container (#8). although the metallic by-products in used electrolyte could be filtered using centrifugal method in small quality, the settling method was used for a large quantity of used electrolyte. in the latter method the used electrolyte, mixed with metal debris and by-products, was stored overnight so that the heavy metallic and salt-byproduct would be settled at the contained bottom. the clear electrolyte at the top was pump back to the fresh electrolyte container (#16) using a longer wt600-2j peristaltic pump (#15) and reused for subsequent experiment if its conductivity was still comparable with that of the fresh electrolyte. the everlast 255 ext dc power supply provides either dc or pulsed dc of 3-150 a up to 500 hz pulsed current frequency. since a high peak current may generate sparks that damage the workpiece and electrode, the constant peak current was set at 26 a, current frequency at 500 hz and 50% duty cycle. stainless steel tubes (𝜙9.5 mm od, 0.3 mm thick, #4) were selected as cathodic electrode. about 13 mm ends were commercially coated with teflon to form a nonconductive layer of 0.02 mm thick on both outside and inside diameters. the coated ends were carefully sanded off using 600-grit abrasive paper to make the cathodic electrode tube conductive. the labworks et-132-2 electrodynamic shaker was powered by the labworks pa-151 linear power amplifier that in turn controlled by an agilent 33250a waveform generator. the computer-controlled positioner included two velmex motorized frames, a rotary plate and a vxm-3 controller system. the system has a load capacity of 15.9 kg horizontally and 4.5 kg vertically with straight-line accuracy of 0.076 mm/25 cm, feed rate range 2.5-5000 µm/s, and repeatability of 0.0025 mm. the tenma 72-6202 multimeter was used to measure the conductivity between the cathodic electrode and the anodic workpiece. the velmex computer-controlled positioner was used to set the initial inter-electrode gap. at first, the multimeter was used to find the location of the cathodic electrode where in contact with the anodic workpiece since the resistance between the cathodic electrode and the anodic workpiece dropped to 0 (ieg = 0). after that, the cathodic electrode moved back 0.3mm and controlled by the velmex positioner. in this investigation, a constant feed rate was set to 15µm/s and the cathodic electrode traveled a distance of 2.5 mm. all experimental conditions are summarized in table 5. after ecm’ed, all samples were rinsed and cleaned with water in an ultrasonic bath for one minute and then dried with compressed air. all samples were positioned in a grass beaker in the bath with ecm’ed holes facing down to facilitate removal of residual particles from the hole. the alicona infinite focus 3d profiler was used to analyze the ecm’ed machined depth, surface finish and wall taper angle. the settled by-products were collected and washed with distilled water 10 times to remove the dissolved potassium bromide. two samples of by-products were prepared for sem and edx. the sample for sem was one drop of by-products solution placed on the titanium plate and dried in air. thin au-pd layer was sputtered coated on the surface of the titanium and specimens. the tescan vega 3 sem was used to capture the surface image of the by-products. the ecm sediment was washed, dried, and deposited on a carbon tape. the zeiss edx was used to analysis the by-products compositions. feng et al. (2021): international journal of engineering materials and manufacture, 6(1), 1-21 10 table 5 summary of experimental conditions variables values current frequency (hz) 500 electrode feed rate (µm/s) 15 electrode travel distance (mm) 2.5 electrolyte concentration (mol/l) 1 electrolyte conductivity (ms/cm) 111-121 electrolyte flow rate (l/min) 2.5 starting ieg (mm) 0.3 peak current (a) 26 vibration amplitude (µm) 0, 2.50, 4.44, 5.00, 7.50, 10.00 vibration frequency (hz) 0, 20, 30, 40, 60, 80 5 results and discussions simulation results from ansys fluent for flushing speed, the effect of vibration frequency, and electrolyte flow rate are presented first. the particle interaction results from star ccm+ simulation are then followed. experimental trends are finally presented and compared with the simulation data. 5.1. average flushing speeds recall that the simulation cell is 0.3 mm × 0.3 mm (figure 6a), and a simulation will be terminated if the 𝑦-coordinate of a particle center is larger than 0.3 mm, i.e, a particle is effectively flushed and traveled outside of the interelectrode gap. typical particle trajectory along 𝑦-direction as a function of time is shown in figure 6. the average flushing speed, 𝑉𝑎𝑣𝑒, is defined as the secant slope of particle path: 𝑉𝑎𝑣𝑒 = particle travel distance travel time = 300 µ𝑚 756 µ𝑠 = 0.396 𝑚/𝑠 (16) (a) (b) figure 6 particle movement in y-direction. vibration 40 hz at 10 µm, electrolyte flow rate 4 m/s. (simulation with ansys fluent at 𝑓 = 40 hz, 𝐴𝑣 = 10 µm, and 𝑉𝑒 = 4 m/s) the effect of vibration frequency on average flushing speed when the driving current for vibration table was set at 𝐼𝑣𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 = 7𝐴 is shown in figure 7. the average flushing speed decreases with increasing vibration frequency. neglecting the effect of the workpiece vibration on the particle movement along the cathodic electrode 𝑥-direction, the distance between workpiece and the particle center is given in equation (17) and illustrated in figure 8. 𝑑𝑔 = −𝐴𝑣 sin(2𝜋𝑓𝑡) + 𝑟𝑝 (17) where, 𝑑𝑔 : gap between particle and workpiece surface (≥ 𝑟𝑝) (µm) 𝐴𝑣 : vibration amplitude (µm) 𝑓 : vibration frequency (hz) 𝑟𝑝 : particle diameter (µm) computer simulation of low frequency vibration in electrochemical machining 11 figure 7 effect of vibration frequency on average flushing speed. (simulation with analys fluent at 𝐼𝑣𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 = 7𝐴) figure 8 illustration of the distance between particle center and workpiece surface. as shown in figure 7, 𝐼𝑣𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 is fixed at 7 a, the average flushing speed decreases from 0.5736 m/s (at 𝑓 = 10 hz, 𝐴𝑣 = 160 µm) to 0.3231 m/s (at 𝑓 = 10,000 hz, 𝐴𝑣 = 0.16 µm) when vibration frequency increases from 10 hz to 10,000 hz. for fixed vibration current or constant vibration power, the vibration amplitude and vibration frequency follow the relationship 𝐴𝑣𝑓 2 = constant 𝐵, and equation (17) becomes: 𝑑𝑔 = −𝐵 sin(2𝜋𝑓𝑡) 𝑓2 + 𝑟𝑝 (18) equation (18) suggests that the distance between particle center and workpiece dg decreases drastically with increasing vibration frequency f. therefore, for fixed current on vibration generator, a high vibration frequency would lead to a smaller gap, lower drag force and lower average flushing speed, as shown in figure 7. the relationship between particle size and average flushing speed is shown in figure 9. as the particle radius increases from 1 µm to 3 µm, the average flushing speed increases from 0.29 to 2.77 m/s. however, continue increase particle size to 5 µm, the average flushing speed changes slightly, from 2.77 to 3.08 m/s. this is because the gap 𝑑𝑔 feng et al. (2021): international journal of engineering materials and manufacture, 6(1), 1-21 12 in equation (18) increases with an increasing of particle radius. larger gap results in higher drag force and higher average flushing speed. figure 9 relationship between average flushing speed and particle radius. (simulation with anasys fluent at 𝑓= 40 hz and 𝐴𝑣 = 10 µm and 𝑉𝑒 = 4 m/s) this simulation results were confirmed with experiment results conducted in another study [12]. for a preset machining parameter combinations (4 µm, 6 µm and 8 µm vibration amplitude, 𝜙160 µm tungsten cathodic electrode with 5 µm insulate layer, 321 stainless steel workpiece with 0.5 mm thickness, 5 wt% nano3 + 0.8 wt% edta-na2 electrolyte, 6 v voltage with 50% duty cycle, 2 khz pulsed voltage and 15.6 µm ieg), after obtaining the maximum mrr at a 50 hz, the mrr decreased with increasing of vibration frequency, as shown in figure 10. figure 10 effect of vibration frequency on the mrr, reprinted from [12]. 5.2. effect of vibration on average flushing speed and part quality the effects of vibration frequency and amplitude on average flushing speed, depth of material removal, and taper angle are presented in this section. figure 11a,b show how the flushing speed and machined depth when varying the vibration parameters. at every vibration amplitude, the average flushing speed increases as the vibration frequency increases. the maximum average flushing speed, 0.396 m/s, is obtained at 40 hz vibration frequency and 10 µm vibration amplitude. for a specific vibration amplitude 𝐴𝑣, when the vibration frequency increasing, the gap between the anodic electrode surface and the particle center is increased, hence the drag force exert on the particle is increased which result in an increasing average particle flushing speed. at every vibration amplitude (5, 7.5, and 10 µm), a higher vibration frequency leads to faster average flushing speed and deeper machining depth. − when vibration frequency increases from 20 to 40 hz, the average flushing speeds increase by 5.4% (from 0.3423 to 0.3608 m/s), 7.8% (from 0.3517 to 0.3790 m/s) and 9.9% (from 0.3610 to 0.3968 m/s), at respective vibration amplitude. − improving of flushing speed changes machining depths by 2.9 % (from 1282 to 1319 µm), 9.9% (from 1308 to 1437 µm) and 18.6% (from 1336 to 1584 µm), respectively. v a v e ( m /s ) computer simulation of low frequency vibration in electrochemical machining 13 (a) av = 5.0 µm (b) av = 7.5 µm av = 10.0 µm figure 11a effect of vibration amplitude on average flushing speed (left vertical scale) and machining depth (right vertical scale) (a) f = 20 hz (b) f = 30 hz (c) f = 40 hz figure 11b effect of vibration frequency on average flushing speed (left vertical scale) and machining depth (right vertical scale) vibration-assisted ecm increases the machined depth of a hole while reducing the hole taper angle, therefore, enhancing the product quality. the effects of vibration frequency on average flushing speed and taper angle are illustrated in figure 12a,b. − at every vibration frequency (20, 30, and 40 hz), a higher vibration amplitude leads to faster flushing speed and smaller taper angle – therefore, straighter and sharper hole profile. when vibration amplitude increases from 5.0 to 10.0 µm, the taper angles decreases by 8.7% (from 31.92 to 29.15°), 12.8% (from 29.32 to 25.56°) and 43.4% (from 29.28 to 16.57°), at respective vibration frequency. − at every vibration amplitude (5, 7.5, and 10 µm), a higher vibration frequency leads to a smaller taper angle. when vibration frequency increases from 20 to 40 hz, the taper angles decrease by 3.4% (from 31.92 to 29.28°), 27.3% (from 29.81 to 21.67°) and 43.2% (from 29.15 to 16.57°) at corresponding vibration amplitude. (a) av = 5.0 µm (b) av = 7.5 µm av = 10.0 µm figure 12a effect of vibration amplitude on average flushing speed (left vertical scale) and taper angle (right vertical scale) feng et al. (2021): international journal of engineering materials and manufacture, 6(1), 1-21 14 (a) f = 20 hz (b) f = 30 hz (c) f = 40 hz figure 12b effect of vibration frequency on average flushing speed (left vertical scale) and taper angle (right vertical scale) the simulation results and experimental data trends presented above agree with other studies. simulation and experimental data suggest a negative correlation between average flushing speed and taper angle. the similar trend was also reported on hole shape after ecm (using brass tube cathodic electrode with 𝜙8 mm outer diameter and 𝜙3.5 mm inner diameter, 20 g/l nacl electrolyte, 6 l/min electrolyte flow rate, 1 mm/min cathodic electrode feed rate, 18 v applied voltage and 50 hz vibration frequency [11]); the conicity (slope of a cone) decreased from 3.95 to 3.25% when vibration amplitude increased from 20 to 100 µm. this trend can also be explained qualitatively: i. vibration of workpiece leads to a higher flushing speed that breaks up agglomerated groups of by-products into smaller chunks of particles. ii. the smaller chunks forming between two electrodes then travel up the wall of hole and outside of the interelectrode zone. the smaller coalesced particles would erode the wall less and result in smaller taper angle and sharper hole profile. low frequency vibration of workpiece increases the flushing speed, enhances ion transport rate and leads to more effective machining rate. similar results were also reported in other experimental studies in which an ecm system utilized 𝜙160 µm tungsten cathodic electrode with 5 µm insulate layer, 321 stainless steel anodic workpiece with 0.5 mm thickness, 5 wt% nano3 + 0.8 wt% edta-na2 electrolyte, 6 v voltage with 50% duty cycle, 2 khz pulsed voltage and 15.6 µm ieg, 3-14 µm vibration amplitude, and 50-200 hz vibration frequency [12]. that study reported that: i. at any vibration amplitude (4, 6, and 8 µm), the mrr increased when increasing vibration frequency from 0 hz to 50 hz. however, the mrr dropped when increasing frequency further to 200 hz. ii. at both vibration frequencies (50 hz and 100 hz), the mrr increased with increasing vibration amplitude in the range 0-8 µm. the maximum mrr was obtained when vibrating at 8 µm amplitude for any vibration frequency. 5.3. effect of electrolyte flow rate on average flushing speed the effect of electrolyte flow rates on particle average flushing speeds is illustrated with simulation data (figure 13a,b). − at 20 hz and 5 µm vibration, when the electrolyte flow rate increases from 2 to 4 m/s, the average flushing speed increases from 0.152 to 0.342 m/s. − at 40 hz and 10 µm vibration, the average flushing speed increases from 0.198 to 0.396 m/s. − for each combination of vibration frequency and vibration amplitude, the average flushing speed seems to be proportional to the electrolyte flow rate. for a single sphere particle in a fluid, newton’s equation is used to determine the drag resistance force. the particlefluid drag coefficient, 𝐶𝑑, is dependent upon reynold’s number, 𝑅𝑒, in addition to liquid properties. there are three regions: the stoke’s law region, the transition region and newton’s law region. by adopting the coefficients from another study [43], the fluid-particle interaction drag force can be modeled as: 𝐹𝑓⃗⃗ ⃗ = 𝐹𝑑⃗⃗⃗⃗ + 𝐹𝑏⃗⃗⃗⃗ = 𝑚 𝑉𝐹⃗⃗⃗⃗ − 𝑉𝑝⃗⃗ ⃗ 𝜏𝑟 − 𝑉𝑖𝜌𝐹𝑔 (19) 𝜏𝑟 = 𝜌𝑝𝑑𝑝 2 18𝜇 24 𝐶𝑑𝑅𝑒 (20) computer simulation of low frequency vibration in electrochemical machining 15 𝑅𝑒 ≡ 𝜌𝐹𝑑𝑝|�⃗� 𝑝 − 𝑉𝐹⃗⃗⃗⃗ | 𝜇 (21) 𝐶𝑑 = 𝑎1 + 𝑎2 𝑅𝑒 + 𝑎3 𝑅𝑒 (22) where, 𝐹𝑓 : particle-fluid interaction force on particle (n) 𝐹𝑑 : drag force (n) 𝐹𝑏 : buoyance force (n) 𝑚 : particle mass (𝑔) 𝑉𝐹 : fluid phase flow velocity (m/s) 𝑉𝑝 : particle flow velocity (m/s) 𝑉𝑖 : translation velocity of particle 𝑖 respectively (m/s) 𝜌𝐹 : fluid density (𝑔/mm 3 ) 𝜌𝑃 : particle density (𝑔/mm 3 ) 𝜏𝑟 : particle relaxation time 𝑑𝑝 : particle diameter (m) 𝜇 : viscosity of the fluid (pa∙s) 𝐶𝑑 : drag coefficient 𝑅𝑒 : reynold’s number for an increasing fluid velocity 𝑉𝐹, the particle-fluid interaction force on particle 𝐹𝑓 is increased, which leads to an increasing particle average flushing speed 𝑉𝑎𝑣𝑒. figure 13a effect of electrolyte flow speed on particle average flushing speed at every vibration frequency. figure 13b effect of electrolyte flow speed on particle average flushing speed at every vibration amplitude. feng et al. (2021): international journal of engineering materials and manufacture, 6(1), 1-21 16 5.4 multiple particle interactions this section presents the simulation results of possible interaction among ecm particles within an interelectrode gap. figure 14 illustrates the initial conditions of the simulation. the blue color bar on the left demonstrates the “particle residence time;” the segment (a) shows the anodic workpiece in the yz-plane and the cathodic electrode (not shown) is in the yz-plane toward the positive x-direction. the four green points, i, ii, iii and iv, represent the particle injection locations. the enlarged view of zone a is shown in segment (b), while segment (c) is the side view of segment (b). figure 14 the star ccm+ simulation results at t0 = 0 µs. (a) the workpiece surface in the yz-plane; (b) enlarged view of section a; and (c) side view of (b) to visualize and follow the motion of a particle at different time and location, define the particle with nomenclature 𝑃𝑋,𝑖(𝑡𝑗): where 𝑋 = 𝐼, 𝐼𝐼, 𝐼𝐼𝐼, 𝐼𝑉 is the particle injection location, 𝑖 = 1,2,3, … , 𝑛 is the particle injection order, and 𝑗 = 1,2,3, … , 𝑛 is injection time. for example, the particle 𝑃𝐼𝑉,1(𝑡1) represents the 1st particle released at location iv and at time 𝑡1. for simplification, only the right side (locations ii & iv) is presented since there is no interaction of particles releasing from ii and iv locations with those released at the i and iii locations. − at time 𝑡1 = 1 μs, the particle 𝑃𝐼𝑉,1(𝑡1) is just released from the anodic plate and it is still in contact with the surface (figure 15). figure 15 the star ccm+ simulation results at 𝒕𝟏 = 𝟏 µs. e l e c t r o l y t e f l o w computer simulation of low frequency vibration in electrochemical machining 17 the timely release of other particles includes: − the particle 𝑃𝐼𝑉,2 is released into simulation domain at time 𝑡2 = 71 µs, represented as 𝑃𝐼𝑉,2(𝑡2) − particle 𝑃𝐼𝑉,3 at time 𝑡3 = 81 µs − particle 𝑃𝐼𝐼,4 at time 𝑡4 = 91 µs − particle 𝑃𝐼𝐼,5 at time 𝑡5 = 141 µs − particle 𝑃𝐼𝐼,6 at time 𝑡6 = 151 µs − particle 𝑃𝐼𝐼,7 at time 𝑡7 = 211 µs recall from figure 2 that the simulation zone is at the top of a workpiece with 300 µm zone, and the electrolyte flow is upward along the positive y axis. thus, the motion of all particles will be in the upward direction of this horizontal ecm setup. − at time 𝑡7 = 211 µs, the locations of these particles are illustrated in figure 16. figure 16 the star ccm+ simulation results at 𝑡7 = 211 µs. as simulation continues, there are collisions occur between the particles. figure 17 and the closed-up figure 18 illustrate the interaction among particles 𝑃𝐼𝑉,2, 𝑃𝐼𝑉,3 and 𝑃𝐼𝐼,7. − at time 𝑡8 = 272 µs, the particle 𝑃𝐼𝐼,7 impacts the particle 𝑃𝐼𝑉,3 (marked with “*”). after collision, this particle 𝑃𝐼𝑉,3 obtains an acceleration along the 𝑦-direction and its flow speed along the 𝑦-direction is increased. the particle 𝑃𝐼𝐼,7 obtains an additional acceleration along the 𝑥-direction and it moves toward the cathodic electrode (not shown, but on the yz-plane in the positive x-direction), while it continues to move along 𝑦-direction due to the drag effect of the fluid. − at time 𝑡9 = 280 µs, the particle 𝑃𝐼𝑉,3 impacts the particle 𝑃𝐼𝑉,2. after collision, the particles 𝑃𝐼𝑉,3 and 𝑃𝐼𝑉,2 will combined and move together. the speed of particle 𝑃𝐼𝐼,7 along the 𝑦-direction is increasing due a higher electrolyte flow speed away from the anodic surface. − at time 𝑡10 = 287 µs, after colliding among particles 𝑃𝐼𝑉,2, 𝑃𝐼𝑉,3 and 𝑃𝐼𝐼,7, the particle 𝑃𝐼𝐼,7 passes the particle 𝑃𝐼𝑉,3. − at time 𝑡11 = 291 µs, the particle 𝑃𝐼𝐼,7 passes the particle 𝑃𝐼𝑉,2, and continue passes the particle 𝑃𝐼𝐼,6. − at time 𝑡12 = 322 µs, the particle 𝑃𝐼𝐼,7 impacts the particle 𝑃𝐼𝐼,5 and continue moves along the 𝑦-direction. − at time 𝑡13 = 353 µs, the particle 𝑃𝐼𝐼,7 has already passed the particle 𝑃𝐼𝑉,1. e l e c t r o l y t e f l o w feng et al. (2021): international journal of engineering materials and manufacture, 6(1), 1-21 18 figure 17 illustration of particle collisions within zone b from 𝑡8 = 272 µs to 𝑡13 = 353 µs. figure 18 enlarged view of figure 17. a “*” is marked on particle piv,3 for identification purpose. figure 19 illustrates the motion of particles 𝑃𝑋,1−6 from 𝑡14 = 512 µs to 𝑡16 = 940 µs. − at time 𝑡14 = 512 µs, the 𝑦 coordinate of the particle 𝑃𝐼𝐼,7 is larger than 300 µm, which means that the particle is flushed away from the interested simulation domain. the particle 𝑃𝐼𝑉,2 obtains an acceleration along the y-direction due to a collision and then its speed is larger than that of the particle 𝑃𝐼𝑉,3. hence, these two particles are separated and move independently. − at time 𝑡19 = 940 µs, the y-coordinate of the particle 𝑃iv,1 is larger than 300 µs, as shown in figure 19 and 20. there is no interaction of particles releasing from ii and iv locations with these from i and iii locations. thus, it is reasonable to use the right side of the workpiece to analysis the multiple particles flushing process. the average flushing speed of the particle 𝑃𝐼𝑉,1 is: 𝑉𝑎𝑣𝑒 = total travel distance travel time = 300 𝜇𝑚 940 𝜇𝑠 = 0.319 𝑚/𝑠 (23) the average flushing speed, calculated from star ccm+ (0.319 m/s showing above), agrees with the result calculated from the anasys fluent (0.396 m/s) shown in equation (16). see figure 18 pii,7 piv,3 piv,2 y z x e l e c t r o l y t e f l o w e l e c t r o l y t e f l o w * * * * computer simulation of low frequency vibration in electrochemical machining 19 figure 19 the star ccm+ simulation results from 𝑡14 = 512 µs to 𝑡16 = 940 µs figure 12 the star ccm+ simulation results at 𝑡16 = 940 µs. 5. conclusions and recommendations this research used both the ansys fluent and star ccm+ software to simulate particle transport process within interelectrode gap in the low frequency vibration-assisted electrochemical machining (ecm) process. a series of simulations were conducted to calculate the particle average flushing speed. the study aimed to find relevant process parameters to increase particle flushing speed, therefore, material removal rate and part quality after ecm. this study showed that: 1) simulations of the motion of a single particle using computational fluid dynamic are performed to track the particle motion and speed between two electrodes. flushing of the by-products is characterized by e l e c t r o l y t e f l o w e l e c t r o l y t e f l o w feng et al. (2021): international journal of engineering materials and manufacture, 6(1), 1-21 20 calculating of particle flushing speed when it exits inter-electrode gap. the maximum flushing speed of ~0.4 m/s was calculated for workpiece vibration frequency of 40 hz at 10 µm vibration amplitude. 2) since the particle generating rate is significant smaller than the electrolyte flow rate, it is reasonable to use a single particle for simulation instead of involving multiple particles in the simulation. 3) the simulation results indicate the average flushing speed in ecm would increase with: workpiece vibration frequency, vibration amplitude, electrolyte flow rate, and particle size. 4) the ecm experimental results show that the high flushing speed of by-products would enhance the process since it produces a deeper hole (increasing material removal rate) while forming a sharper hole profiles (increasing product quality). 5) the 2 µm spherical particles were used in this study, further study should consider the interactions between different shapes and different size of by-product particles. references 1. mcgeough, j.a. principles of electrochemical machining. chapman and hall: london, 1974. 2. acharya, b.r.; mohanty, c.p.; mahapatra, s.s. multi-objective optimization of electrochemical machining of hardened steel using nsgaii. procedia engineering 2013, 51, 554-560. 3. bhattacharyya, b.; sorkhel, s.k. investigation for controlled electrochemical machining through response surface methodology-based approach. journal of materials processing technology 1999, 86, 200-207. 4. senthilkumar, c.; ganesan, g.; karthikeyan, r.; srikanth, s. modelling and analysis of electrochemical machining of cast al/20%sicp composites. materials science and technology 2010, 26, 289-296. 5. schuster, r.; kirchner, v.; allongue, p.; ertl, g. electrochemical micromachining. science 2000, 289, 98-101. 6. feng, z.; granda, e.; hung, w. experimental investigation of vibration-assisted pulsed electrochemical machining. procedia manufacturing 2016, 5, 798-814. 7. bhattacharyya, b.; munda, j. experimental investigation on the influence of electrochemical machining parameters on machining rate and accuracy in micromachining domain. international journal of machine tools and manufacture 2003, 43, 1301-1310. 8. munda, j.; bhattacharyya, b. investigation into electrochemical micromachining (emm) through response surface methodology-based approach. the international journal of advanced manufacturing technology 2008, 35, 821-832. 9. senthilkumar, c.; ganesan, g.; karthikeyan, r. ecm of al/15% sicp composites through a response surface methodology-based approach. international journal of materials research 2012, 103, 378-382. 10. ghoshal, b.; bhattacharyya, b. vibration assisted electrochemical micromachining of high aspect ratio micro features. precision engineering 2015, 42, 231-241. 11. ebeid, s.j.; hewidy, m.s.; el-taweel, t.a.; youssef, a.h. towards higher accuracy for ecm hybridized with low-frequency vibrations using the response surface methodology. journal of materials processing technology 2004, 149, 432-438. 12. liu, z.; zhang, h.; chen, h.; zeng, y. investigation of material removal rate in micro electrochemical machining with lower frequency vibration on workpiece. international journal of machining and machinability of materials 2013, 14, 91-104. 13. bhattacharyya, b.; malapati, m.; munda, j.; sarkar, a. influence of tool vibration on machining performance in electrochemical micro-machining of copper. international journal of machine tools and manufacture 2007, 47, 335-342. 14. rebschläger, a.; kollmannsperger, r.; bähre, d. video based process observations of the pulse electrochemical machining process at high current densities and small gaps. procedia cirp 2014, 14, 418-423. 15. ruszaj, a.; zybura-skrabalak, m.; skoczypiec, s.; żurek, r. in electrochemical machining supported by electrode ultrasonic vibrations, 13th international symposium for electromachining, isem, spain, may, 2001; pp 9-11. 16. patel, j.b.; feng, z.; villanueva, p.; hung, w.n.p. quality enhancement with ultrasonic wave and pulsed current electrochemical machining. procedia manufacturing 2017, 10, 662-673. 17. pa, p.s. electrode form design of large holes of die material in ultrasonic electrochemical finishing. journal of materials processing technology 2007, 192-193, 470-477. 18. skoczypiec, s. research on ultrasonically assisted electrochemical machining process. the international journal of advanced manufacturing technology 2010, 52, 565-574. 19. feng, z.; izwan, n.s.l.b.; gutierrez, e.e.g.; hung, w. in energy comparative study for mechanical punching, electrical-discharge machining and electro-chemical machining, 5th international welding, industrial engineering and manufacturing congress, saltillo, coahuila, mexico, 2015; saltillo, coahuila, mexico. 20. feng, z.; orona-hinojos, j.m.; villanueva, p.p.; lomeli, p.; hung, w.n.p. flushing enhancement with vibration and pulsed current in electrochemical machining. international journal of engineering materials and manufacture 2017, 2, 67-85. 21. feng, z.; patel, j.; granda, e. process selection for energy efficiency. in american society for engineering and education (asee) conference, seattle, washington, usa, 2015. computer simulation of low frequency vibration in electrochemical machining 21 22. rajurkar, k.p.; sundaram, m.m.; malshe, a.p. review of electrochemical and electrodischarge machining. procedia cirp 2013, 6, 13-26. 23. deconinck, d.; damme, s.v.; deconinck, j. a temperature dependent multi-ion model for time accurate numerical simulation of the electrochemical machining process. part ii: numerical simulation. electrochimica acta 2012, 69, 120-127. 24. deconinck, d.; van damme, s.; deconinck, j. a temperature dependent multi-ion model for time accurate numerical simulation of the electrochemical machining process. part i: theoretical basis. electrochimica acta 2012, 60, 321-328. 25. alder, g.m.; clifton, d.; mill, f. a direct analytical solution to the tool design problem in electrochemical machining under steady state conditions. proceedings of the institution of mechanical engineers, part b: journal of engineering manufacture 2000, 214, 745-750. 26. prentice, g.a.; tobias, c.w. simulation of changing electrode profiles. journal of the electrochemical society 1982, 129, 78-85. 27. moarrefzadeh, a. finite-element simulation of dimensional limitation of ecm process. international journal of multidisciplinary sciences and engineering 2011, 2, 39-43. 28. purcar, m.; bortels, l.; van den bossche, b.; deconinck, j. 3d electrochemical machining computer simulations. journal of materials processing technology 2004, 149, 472-478. 29. kozak, j.; gulbinowicz, d.; gulbinowicz, z. the mathematical modeling and computer simulation of pulse electrochemical micromachining. engineering letters 2008, 16, 556-561. 30. bortels, l.; purcar, m.; bossche, b.v.d.; deconinck, j. a user-friendly simulation software tool for 3d ecm. journal of materials processing technology 2004, 149, 486-492. 31. volgin, v.m.; davydov, a.d. mass-transfer problems in the electrochemical systems. russian journal of electrochemistry 2012, 48, 565-569. 32. minazetdinov, n.m. a hydrodynamic interpretation of a problem in the theory of the dimensional electrochemical machining of metals. journal of applied mathematics and mechanics 2009, 73, 41-47. 33. minazetdinov, n.m. a scheme for the electrochemical machining of metals by a cathode tool with a curvilinear part of the boundary. journal of applied mathematics and mechanics 2009, 73, 592-598. 34. ma, n.; xu, w.; wang, x.; tao, b. pulse electrochemical finishing: modeling and experiment. journal of materials processing technology 2010, 210, 852-857. 35. wu, j.; wang, h.; chen, x.; cheng, p.; ding, g.; zhao, x.; huang, y. study of a novel cathode tool structure for improving heat removal in electrochemical micro-machining. electrochimica acta 2012, 75, 94-100. 36. zhu, h.p.; zhou, z.y.; yang, r.y.; yu, a.b. discrete particle simulation of particulate systems: theoretical developments. chemical engineering science 2007, 62, 3378-3396. 37. xiong, y.; zhang, m.; yuan, z. three-dimensional numerical simulation method for gas–solid injector. powder technology 2005, 160, 180-189. 38. li, y.; zhang, j.; fan, l.-s. numerical simulation of gas–liquid–solid fluidization systems using a combined cfd-vof-dpm method: bubble wake behavior. chemical engineering science 1999, 54, 5101-5107. 39. richardson, j. incipient fluidization and particulate systems. american press, london: 1971; pp 27-29. 40. ergun, s.; orning, a.a. fluid flow through randomly packed columns and fluidized beds. industrial & engineering chemistry 1949, 41, 1179-1184. 41. choi, h.g.; joseph, d.d. fluidization by lift of 300 circular particles in plane poiseuille flow by direct numerical simulation. journal of fluid mechanics 2001, 438, 101-128. 42. li, j.; kwauk, m. exploring complex systems in chemical engineering—the multi-scale methodology. chemical engineering science 2003, 58, 521-535. 43. morsi, s.; alexander, a. an investigation of particle trajectories in two-phase flow systems. journal of fluid mechanics 1972, 55, 193-208. 44. tsuji, y.; kawaguchi, t.; tanaka, t. discrete particle simulation of two-dimensional fluidized bed. powder technology 1993, 77, 79-87. international journal of engineering materials and manufacture (2019) 4(3) 124-136 https://doi.org/10.26776/ijemm.04.03.2019.05 hazra m. and singh, s. defence metallurgical research laboratory po: kanchanbagh, hyderabad 500 058, india e-mail: mhazra@dmrl.drdo.in reference: hazra, m. and singh s. (2019). failure analysis of diode components of electronic relay packages via thorough microstructural characterization. international journal of engineering materials and manufacture, 4(3), 124-136. failure analysis of diode components of electronic relay packages via thorough microstructural characterization received: 16 february 2019 accepted: 03 september 2019 published: 27 september 2019 publisher: deer hill publications © 2019 the author(s) creative commons: cc by 4.0 mrityunjoy hazra and satyapal singh abstract diode components used in the electronic relay packages of avionics of a weapon system had been found corroded. two sets of the complete assembly of the damaged diode parts consisting of diode body, plain washer, spring washer and mounting nuts were analysed for finding out the root causes of failures. detailed metallographic characterization of the failed materials was carried out using optical microscope, scanning electron microscope (sem), energy dispersive spectroscopy (eds) analysis within sem and microhardness study. it was found that inadequate electroless nickel (en) plating along with significant amount of porosity and presence of mns type of stringers affected the corrosion resistance of the diode body tremendously for both the sets. inadequate electroplated zn layer was observed on spring washer, plain washer and nut, wherein both uniform and pitting corrosion were detected. important recommendations included: (i) thicker (more than 25 µm) en coating with as-specified porosity level for diode body, (ii) replacement of electroplated zinc layers with galvanized zinc layer (of higher thickness) on all the fasteners, (iii) precaution in minimizing formation of galvanic couplings observed in the present system, like that between en-coated diode body and zinc coated fasteners, between mild steel and stainless steel fasteners etc. keywords: electronic relay package corrosion, electroless nickel plating, diode, spring washer, plain washer, nut. 1. background diodes of different sizes and capacities, used in the electronic relay packages of avionics of a weapon system had been found corroded, after qualification testing of the packages. two sets of the complete assembly of the damaged diode parts including diode body, plain washer, spring washer and mounting nuts along with few unused (asfabricated) ones were investigated for detecting root causes of corrosion. this report presents the results of the failure investigation. 2. literature survey 2.1 power diode a power diode has larger pn junction area as compared to its smaller signal diode cousin [1]. this results in a high forward current capability of up to several kilo-amps and a reverse blocking voltage of up to several kilo-volts. it is not suitable for high frequency applications above 1 mhz, but special and expensive high frequency high current diodes are available for the said purpose. they can also be used as free-wheeling diodes and snubber networks, due to their high current and voltage characteristics. the failed present diode system is a typical commercially available general purpose standard recovery high current rectifier 1n2131 200v 60a cathode stud type [2]. it usually comes with mounting hardware like plain washer, spring washer and nut (figure 1). it is usually used in applications such as dc power supplies, inverters, converters, ultrasonic systems, choppers and as a free-wheeling diode. 2.2 electrical/electronic relay package system there are varieties of electrical and electronic devices which are classed as output devices used to control or operate some external physical process. these output devices are also known as actuators. its basic function is to convert an electrical signal into a corresponding physical quantity such as movement, force, sound etc. an actuator is also classed as a transducer because it changes one type of physical quantity into another and is usually activated or operated by a low voltage command signal. actuators can be classed as either binary or continuous devices based upon the number of stable states their output has. failure analysis of diode components of electronic relay packages via thorough microstructural characterization 125 a relay is a binary actuator as it has two stable states, either energised and latched or de-energised and unlatched, while a motor is a continuous actuator because it can rotate through a full 360 o motion (figure 2). the most common types of actuators or output devices are electrical relays, lights, motors and loudspeakers. electrical relays can be divided into mechanical action relays called “electromechanical relays” and those which use semiconductor transistors, thyristors, triacs, etc., as their switching device called “solid state relays” or ssrs. 2.3 corrosion of electronic components corrosion of complex electronic equipment is an increasingly serious problem, causing extensive damage, while there is an enormous increase in number and variety of applications of electronic equipment in commercial, industrial, and domestic environments. literature survey has shown that the corrosion of electronic equipment is a serious problem, causing extensive damage which is estimated at $ 5 billion in the united states alone for equipment repairs, downtime and replacements [3]. it occurs throughout the entire life cycle during different stages of manufacturing, assembly, transport and storage of components and assemblies and during field operations of the equipment. presence of moisture, chloride, sulphur dioxide, hydrogen sulphide and other airborne corrosives, meteorological parameters etc influence the occurrence of corrosion. as electronics continue to shrink in size and grow in capacity, the importance of corrosion control increases [4]. miniaturization of systems based on integrated circuits and small size components, close component spacing, separable electrical contacts having lower voltages and contact forces than before have resulted in failures of electronic equipment due to the formation of small quantities of corrosion products. materials used in electronic equipment manufacture are used for their electrical or magnetic properties. complexity, moisture, airborne corrosives, impressed currents, etc. influence the occurrence of corrosion. alloying them with chromium is not possible with these devices/equipment due to deleterious effects on the properties of interest. the failures of thin film circuits and printed circuit boards are divided into two classifications – (i) dry electro migration occurring in the absence of moisture or electrolyte, (ii) simultaneous corrosion and electro deposition in the presence of moisture to yield electrolyte of reasonable conductivity. with the increasing rate of corrosion in these microelectronic equipment/devices/components there is slow deterioration of electronics which poses great threat in future with unpredictable consequences. in conclusion, a car can function even when pounds of metal are lost to corrosion but an electronic device fails with a minimum loss of 1 pico gram of the material. 2.3.1 causes for corrosion in electronic devices there may be one or more than one reasons for failure of a component. principle reasons for corrosion in electronic devices are: (i) service of devices such as integrated circuits (ic) in which metallic lines are often biased electrically relative to nearby lines, (ii) aggressive manufacturing processes, (iii) exposure to uncontrolled environments such as temperature, humidity and contamination, (iv) due to device miniaturization and its effect on the width and separation of metal lines on ics (have been cut in half approximately every 5 years and not less than 1 micron in the most advanced devices) [5,6], (v) reactive gaseous agents –nox, sox, o3, h2o2, nh3, h2s plus volatile organic compounds; suspended inorganic and organic acids (h2so4 hcl, hno3), suspended submicron hygroscopic ionic particles (nh4hso4, nh3no4, (nh4)2 so4 plus others); other inorganic compounds and metals – nacl, fe, al, mg, ca, k suspended in the air. figure 1: commercially available 1n2131 200v 60a cathode stud system, similar to the presently investigated systems. hazra and singh (2019): international journal of engineering materials and manufacture, 4(3), 124-136 126 figure 2: a typical electrical relay package circuit. 2.3.2 factors influencing the rate of corrosion some important factors influencing the rate of corrosion are: (i) presence of contaminants, (ii) contamination from assembly, (iii) contamination from handling and storage, (iv) presence of airborne contaminants. 2.3.3 corrosion control complexity in design, moisture, airborne corrosives, impressed currents etc. influence the occurrence of corrosion in electronic devices in such a way that protection against and control of corrosion becomes challenging. nevertheless, introduction of computer chip type of micro-devices has warranted development of new methods of corrosion protection for equipment exposed to outdoor or polluted environments [6]. prevention methods including hermetic sealing of components in cavities, use of protective coatings, encapsulation, use of noble metal plating, increased use of more corrosion resistant metal alloys and the use of moisture absorbing desiccants have all served to decrease, but not eliminate corrosion in electronic components. volatile corrosion inhibitors (vcis) provide an effective and probably the most suitable means of protecting electronic components from corrosion. vcis represent a method of chemically conditioning the environment that consequently become less corrosive to the metals. mixed inhibitors are best suited for the requirements of electronic industry. this direct method of corrosion protection by means of metal passivation in many cases is superior to traditional indirect methods of corrosion protection such as the use of drying agents and the protective coatings. the compounds capable of inhibiting both cathodic and anodic reactions have optimum effectiveness, when a phenomenon in electronic equipment is simulated by the design. 2.3.4 corrosion types in electronic devices there are some common examples of revelation of corrosion phenomenon in electronic industries. some of those are [6]: (i) micro pitting on aluminium on ic, (ii) voltaic corrosion in ics, (iii) pore creep in electrical contacts and metallic joints, (iv) solder corrosion, (v) printed circuit board (pcb). 2.3.5 method of analysis of corrosion in electronic devices various ways of corrosion analysis and monitoring are available. some of those are [6]: (i) water drop migration to analyse dendrite formation electrochemical techniques, (ii) ac impedance analysis of residues on pcbs, (iii) submicron dust particle exposure chamber, (iv) ion chromatography to determine ionic contamination, (v) corrosive gas test, (vi) field and laboratory corrosion methods for contact materials (gold and tin plated), (vii) determination of hermicity of electron devices by dye penetration. 3. experimental procedure all the received parts were, at first, examined visually by naked eye and under magnifying glass. photographs in the as-received condition were taken and preserved for future reference during the course of analysis. afterwards, the parts were held under forced air using a typical metallographic dryer, so as to remove the loosely held foreign matters, sitting on the surface as a result of consequential effect. then, all the parts were examined under scanning electron microscope (sem) to obtain the composition of the clearly visible surface corrosion debris. after that, representative cross-sectional sample extraction was carried out from the severely corroded regions for detailed metallographic (optical microscopic and scanning electron microscopic) study in both unetched and etched condition. compositional analyses on each part were carried out with eds attachment of the sem. bulk compositional analysis for all the components was carried out with the help of inductively coupled plasma optical emission spectroscopy (icp oes) technique. vickers microhardness readings on each of the samples were taken at 300 gf load value. failure analysis of diode components of electronic relay packages via thorough microstructural characterization 127 4. experimental results 4.1 visual examination photographs of all the as-received components are shown in figure 3 and figure 4 for set 1 and set 2 parts respectively. the observations are as tabulated below in table 1. it is to be noted that the spring washer among all the components of set 1 seems to have experienced least corrosion damage, while plain washer of set 2 assembly did not reveal any sign of corrosion. the appearance of cross-sectional samples after mounting in bakelite hot mount for detailed metallographic study is as shown in figure 5. it is to be noted that the stud part for diode body of set 2 assembly is tapered unlike that for set 1. table 1: visual observations as captured by photography nomenclature (identification) of the parts visual observations diode body set 1 diode shell is tarnished with a black product, while the stud seems to have experienced overheating. set 2 overall, it seems to be negligibly affected (no visible corrosion debris), while stud seems to have experienced overheating. plain washer set 1 major portion is severely corroded, having a rust-like appearance. set 2 it does not seem to be affected at all. spring washer set 1 it seems to be negligibly affected. set 2 major portion is severely corroded, having a rust-like appearance. nut set 1 major portion is moderately corroded. set 2 major portion is severely corroded, having a rust-like appearance. figure 3: (a) photographs of diode body, plain washer, spring washer and nut for set 1 diode assembly in the as-received condition showing corrosion with varying severity, (b-e) magnified views of the components. figure 4: (a) photographs of diode body, plain washer, spring washer and nut for set 2 diode assembly in the as-received condition showing corrosion with varying severity, (b-e) magnified views of the components. 4.2 metallographic examination set 1 corrosion product diode body the corroded debris on the shell surface was analysed by eds in as-received condition (figure 6). magnified views of the shell cross-section near the coated region are displayed in figure 6d,e. those analyses reveal the presence of corrosion debris on both the coating and in the interior, containing largely fe, o and small amount of cl, as is confirmed by the eds analysis of figure 6f. one more instance of observed corrosion debris is as shown in figure 6g,h, where there is an apparent absence of the coating. corrosion product on that place contains majorly fe and o, along with small amounts of cl, k and si, as is shown in figure 6i. not only that, it is also noteworthy that corrosion has occurred quite significantly along the mns stringer-matrix interface and on the stringer itself, resulting in the eating away of the shell material, as has been shown in figure 7a-c. many a times, the corrosion paths (cracks) followed by those stringers and stringer-matrix interfaces are matching with the ferrite grain boundaries. hazra and singh (2019): international journal of engineering materials and manufacture, 4(3), 124-136 128 plain washer the eds analysis on the corrosion products of the as-received part is as shown in figure 8b. it reveals the presence of zn, fe, o and si. the unetched as well as etched cross-sectional microstructure did not reveal the presence of any corrosion product. figure 8c shows one etched photograph along an edge, in which no penetration of corrosion product into the structure was observed. it is also to be noted that the corrosion mechanism seems to be of uniform type and no pitting mechanism is present in this case. spring washer this part does not seem to have experienced any corrosion, as is quite clear from the visual appearance. figure 9b is a cross-sectional optical micrograph of the part. figure 9c is an sem image. it is to be noted that there is a layer having different contrast to that of base material with average thickness of 5 µm. at locations, the layer thickness has been found to be as high as 20 µm. the eds analysis of the region reveals the presence of zn, fe and o, as shown in figure 9d. it was also observed to possess pitted surface, as is shown in figure 9e. nut the corrosion product of the as-received part is as shown in the eds result of figure 10a. it reveals the presence of zn, fe, o and ni. the etched cross-sectional microstructure at some of the corroded regions reveals the presence of pitting, as is shown in figure 10b. figure 5: cross-sectional samples after mounting in bakellite hot mount. figure 6: (a) magnified photograph of the diode shell of figure 3a,b in the as-received condition showing the corrosion, (b) eds results of the corrosion debris sitting on the shell, (c) optical micrograph of the corroded shell, (d,e) corrosion along the coating and deep inside the structure, (f) eds analysis for the corrosion product shown in figs. (d,e), (g,h) severe corrosion of the shell material along an edge in absence of coating, (i) eds analysis for the corrosion product shown in figs. (g,h). failure analysis of diode components of electronic relay packages via thorough microstructural characterization 129 figure 7: (a,b,c) optical, sem se and sem bse micrographs respectively showing mns stringer influenced corrosion along the stringer-matrix interface. figure 8: (a) as-received photograph of the plain washer of figure 3a,c showing the corrosion, (b) eds analysis result for the corrosion debris sitting on the surface, (c) etched optical micrograph along an edge in the cross-sectional view of the severely corroded region showing uniform corrosion and no penetration of the corrosion product deep into the structure. figure 9: (a) as-received photograph of the spring washer of figure 3a,d showing the corrosion, (b,c) respective optical and sem bse image showing corrosion products along an edge in the cross-sectional view, (d) eds analysis result for the corrosion product shown in figure 9c, (e) etched optical micrograph along an edge showing severe pitting. table 2: chemical compositions of investigated failed (corroded) components component chemical compositions (wt%) c s p mn ni cr v fe diode shell: set 1 and set 2 0.17 0.035 0.033 0.70 bal plain washer set 1 0.08 0.048 0.040 0.45 bal plain washer set 2 0.04 0.045 0.040 0.35 8.5 20 bal spring washer: set 1 and set 2 0.60 0.040 0.050 0.75 0.12 bal nut: set 1 and set 2 0.40 0.045 0.038 0.65 bal material diode material has three major parts. those are stud-head combination, ring and shell. the whole assembly was found to be coated by electroless nickel (en) coating with phosphorous in the lowest range (2-5 wt.%) . stud-head combination has been made from annealed bar stock of pure copper, while ring and shell have been made of annealed low carbon steel (figure 11) of grade aisi 1018. table 2 enlists the bulk chemical compositions for each of the components analysed in this investigation. the carbon steel of shell seems to be of free-machining variety, as evidenced by ample amount of mns stringers in the microstructure (figure 11). the shell and ring seems to be bonded by the diffusion bonding between two en layers on the surfaces, while ring is joined to the stud head with the use of ag-cu-pb filler alloy. fe-ni and fe-o-cl-rich products along some locations of the ring-shell interface may be the result of ingress of environmental o and cl at the micro-gap between side stud head and shell. plain washer has been machined from annealed low carbon steel bar stock conforming to aisi 1008 (figure 12). the material for spring washer is a carbon steel of grade sae 6160. it seems to be machined from an annealed bar stock and then hardened and tempered for use in service (figure 13). nut material has been machined from an extruded medium carbon steel (≈ 0.4 wt.% c) and design profiles were given afterwards (figure 14). this seems to correspond to aisi 1045. each of the washers and nut was coated with electroplated zinc layer, as indicated by the layer thickness (≈ 5 µm) [2]. hazra and singh (2019): international journal of engineering materials and manufacture, 4(3), 124-136 130 figure 10: (a) eds analysis result for the corrosion product sitting on the surface of nut (inset: as-received photograph showing the corrosion of nut) (b) etched optical micrograph along the threaded region showing moderate degree of pitting. figure 11: (a) cross-sectional optical micrograph of the diode stud portion in etched condition, etchant: acidified potassium dichromate, (b) magnified view of the encircled region in figure 11, (c) diode shell microstructure in etched condition showing mns stringers, etchant: 2% nital, (d) etched shell microstructure in higher magnification showing whitish coating. figure 12: (a) cross-sectional etched optical micrograph of the plain washer, etchant: 2% nital, (b) eds analysis of the base material for plain washer, (c) eds analysis of the coating for plain washer. figure 13: (a) cross-sectional etched optical micrograph of the spring washer, etchant: 5% nital, (b) eds analysis of the base material for spring washer, (c) eds analysis of the coating for spring washer. figure 14: (a-c) cross-sectional etched optical micrographs of the nut, etchant: 2% nital, (b) eds analysis of the base material for nut, (c) eds analysis of the coating for nut. inference: the diode shell has experienced severe corrosion with the as-received corrosion debris revealing the presence of zn, ca, k, fe and o beside the coating material (ni and p). presence of zn indicates its transfer through corrosion product of other zn-plated components in the assembly, while ca and k indicate the service environmental effect. however, presence of fe and o, at the same time, indicates slight rusting of the component. the cross-sectional micrographs along with the eds results clearly points out the localized perforated/corroded and/or eroded en failure analysis of diode components of electronic relay packages via thorough microstructural characterization 131 coating and subsequent rusting within the coating as well as shell body [7,8]. the rust has been observed upto 25 µm depth from the coated surface. additionally, one should note that coating perforation may have been also there as a result of improper plating process, as has been noticed in the high magnification sem images, thus aggravating the severity of corrosion on the shell. mns stringer-induced interfacial corrosion has also been observed here, likely due to the availability of the sufficient oxygen and presence of severe stress concentration along the interface. both plain washer and nut have been found to be rusted, as evidenced by the presence of fe and o in the corrosion product. nonferrous metals such as zinc, nickel, aluminium, and magnesium do not contain iron and will not ‘red rust’. red rust only becomes visible after the sacrificial metal has been depleted. therefore, the locations with the red appearance for the components plain washer and nut had definitely lost the sacrificial action of the coating because of its depletion and got exposed to the corrosive environment, resulting in rusting. spring washer has not shown any visual evidence for corrosion and looked quite shiny. however, it is noteworthy that zn-o rich phase (usually coming as a result of zn-plating) with trace amount of fe, as obtained during the cross-sectional microstructural examination indicates the inception of corrosion process at some localized areas. set 2 corrosion products the configuration, type of material and coating for diode body, spring washer and nut parts of set 2 have been found to be similar to those of set 1. therefore, detailed representation by figures and texts for those parts are not placed here for set 2 (whenever deemed inappropriate) for avoidance of the repetition and improving upon the readability of this report. diode body there was no corrosion debris sitting on the as-received diode body, as observed during visual inspection. however, corrosion product containing fe and o has been detected, up to a depth of 100 µm below the en coating, while examining the cross-sectional sample. this has been shown in figure 15a and corresponding eds analysis is given in figure 15b. plain washer there was no corrosion product observed on the surface of the as-received part, as is presented in figures 4a,c and 16a. figure 16b shows etched whole cross-sectional micrograph so as to look into and present the corrosion features of this part, if any. however, no signature of corrosion could be traced out, as is clearly seen in the micrograph. spring washer this part had experienced severe corrosion, as is quite clear from the reddish surface appearance observed during visual inspection (figure 4a,d and figure 17a). that reddish deposit has been analysed in as-received condition and found to contain product rich in fe and o, as is shown in figure 17b. figure 17c,d are the cross-sectional micrographs in unetched condition, revealing severe pitting of the part. figure 17e is an optical micrograph in etched condition, showing etched layers along the edge with different contrasts to that of interior. in this image, both uniform attack (of ≈ 100 µm depth) and pitting attack have been shown and the corrosion product has been found to be rich in fe and o for both the form, as is shown by the eds results in figure 17f,g. nut the corrosion product of the as-received part is as shown in the eds result of figure 18a along with the as-received photograph. severe corrosion has been evidenced by the reddish surface appearance as well as the eds results containing fe, zn, o, k, ca, s, si and al. the etched sem micrographs along the thread are shown in figure 18(b,c) and (d,e) in both se and bse modes. the imaging at different locations of the nut sample as well as the eds analysis confirms the presence of fe-o rich phases at both the threaded regions and deep inside the structure, as has been typified here. figure 15: (a) optical micrograph of the corroded shell showing corrosion deep inside the structure, (b) eds analysis for the corrosion product shown in figure 15a. (c) hazra and singh (2019): international journal of engineering materials and manufacture, 4(3), 124-136 132 figure 16: (a) as-received photograph of the plain washer of figure 4a,c showing no sign of corrosion, (b) optical micrograph of the whole cross-section with no trace of corrosion, etchant: aqua-regia. figure 17: (a) as-received photograph of the spring washer of figure 4a,d showing severe corrosion, (b) eds analysis result for the corrosion debris on the as-received washer, (c,d) unetched optical micrographs along an edge showing severe pitting, (e) etched optical micrograph showing uniform as well as pitting corrosion, (f,g) eds analysis results for the corrosion products shown in figure 17e. material diode material consisted of three major parts, stud-head combination, ring and shell. the whole assembly is protected by electroless nickel (en) coating with phosphorous in the lowest range (2-5 wt.%). stud-head combination has been made from drawn wire of annealed pure copper where upset forging type of operation has been applied for obtaining head part (figure 19). ring and shell have been made of annealed low carbon steel bar stock. the carbon steel of shell seems to be of free-machining variety with ample of mns stringers in the microstructure, conforming to aisi 1018, as was the case for set 1 (table 2). the shell and ring seem to be bonded by the diffusion bonding between two en layers on the surfaces, while ring is joined to the stud head with the use of cu-sn-fe base filler alloy. fe-nio-sand ni-fe-o-rich products along some locations of the ring-shell interface may be the result of ingress of environmental o and s at the micro-gap between side stud head and shell. the presence of fe-cu-p-snand fe-cuo-p-rich phases in the interface between ring and stud head have embrittled the structure locally and thus occasionally resulted in cracking, as has been seen through microstructural and hardness evaluation. plain washer has been machined from solutionized austenitic stainless steel bar stock of aisi 316 type (figure 20). the material for spring washer is a carbon steel conforming to sae 6160. it seems to be machined from an annealed bar stock and then hardened and tempered for use in service (figure 21). however, lower volume fraction of carbides and lower hardness value of the spring material for set 2 assembly than that for set 1 assembly indicates (low temperature) soft tempering treatment applied to the former unlike that to later. nut material has been machined from an extruded medium carbon steel of grade aisi 1045 and design profiles were given afterwards (figure 22). each of the washers and nut was coated with electroplated zinc layer. table 2 enlists the bulk chemical compositions for each of the components analysed in this investigation. failure analysis of diode components of electronic relay packages via thorough microstructural characterization 133 figure 18: (a) eds analysis result for the corrosion debris on the as-received nut, (b,c) scanning electron micrographs along the threaded region under respective se and bse modes showing presence of corrosion products, (d,e) scanning electron micrographs away from the threaded region and deep into the structure under respective se and bse modes showing presence of corrosion products, (f) eds analysis results for the corrosion products. figure 19: (a) cross-sectional optical micrograph of the diode stud portion in etched condition, etchant: acidified potassium dichromate, (b) magnified view of the encircled regions in figure 19a. figure 20: (a) cross-sectional etched optical micrograph of the plain washer, etchant: aqua-regia, (b) magnified view of the encircled region showing chain like δ-ferrite, (c) eds analysis of the base material for plain washer. figure 21: cross-sectional etched optical micrograph. figure 22: (a-c) cross-sectional etched optical micrographs of the nut, etchant: 2% nital. hazra and singh (2019): international journal of engineering materials and manufacture, 4(3), 124-136 134 table 3: vickers microhardness readings at 300gf (w.r.t. figures 3, 4) nomenclature (identification) of the parts vickers microhardness (hv0.3) diode body * set 1 56 (stud), 54 (head), 125 (shell), 315 (coating) set 2 118 (stud), 118 (head), 130 (shell), 310 (coating) plain washer * set 1 139 set 2 222 spring washer set 1 392 set 2 422 nut set 1 217 set 2 206 inference: the diode shell has experienced inception of corrosion internally presumably due to the presence of perforation in the en coating and/or local corrosion on coating and subsequently that of the shell material [7, 8]. another factor of great concern may be that the diode body was moderately corroded prior to the en plating. mns stringer-induced interfacial corrosion has also been observed here, likely due to the availability of the sufficient oxygen and presence of severe stress concentration along the interface. spring washer has shown rusting both in uniform and pit form. on the other hand, plain washer did not show any trace of corrosion due to the superior corrosion resistance of passivated/pre-oxidized aisi 316 type of stainless steel to that of zn-coated low carbon steel. nut has been found to be affected by corrosion deep into the structure and that manifested as reddish rusts on the surface. hardness micro hardness readings taken at 300 gf load are presented in table 3 with reference to figures 3-5. it is to be noted that each of the diode parts for both the sets revealed comparable hardness values except diode head and plain washers. conclusions 1. inadequate electroless nickel (en) plating along with significant amount of porosity and presence of mns type of stringers affected the corrosion resistance of the diode body tremendously for both the diode sets. 2. inadequate electroplated zn layer was observed on spring washer and nut, wherein both uniform and pitting corrosion were detected for both the diode sets. 3. inadequate electroplated zn layer was also responsible for corrosion of plain washer of set 1 diode assembly, while stainless steel made plain washer (without coating) of set 2 assembly did not corrode at all. 4. the selection of stainless steel for plain washer in that case may have been without any logic and an accident, which saved the said washer and in turn may have aggravated the corrosion of other fasteners in contact significantly due to galvanic effect. bulk material for each of the other fasteners for both the diode assemblies was of plain carbon steel type. 5. a summary of all the corrosion related findings for each fastener types for both the diode sets are tabulated in table 4 for a quick and easy reference. this table may also prove to be very useful for relative comparison between traits of set 1 and set 2 components. recommendations 1. there should be periodic inspection of the subject components by the non-destructive evaluation methods, such as conventional x‐ray fluorescence spectroscopy (xrf), automated contact resistance probe (acrp) etc. or advanced technique like scanning kelvin probe (skp) and its upgraded version scanning kelvin force microscopy (skpm), localised electrochemical impedance spectroscopy (leis) etc. [9]. this is to obtain quick ideas about the existence and nature of corrosion, if any, during service so as to avoid sudden failure of the subject component. these techniques can also contribute to the study of the galvanic effect in different materials, helping to the revelation of the precursor sites for the pit formation. the use of localised techniques can complement the results obtained with conventional electrochemical techniques, leading to a better comprehension of the corrosion processes. 2. steel of the diode shell should be manufactured and processed in such a way so that an optimum shape (aspect ratio) of the mns stringers is achieved for obtaining a balance between sufficient machinability and lower (matrixstringers) interfacial stress (and thus lower corrosion). 3. the electroless nickel coating applied on the diode body should be at least 25 µm thick and with almost nil porosity level, which would like to improve the general as well as galvanic corrosion resistance of the underlying material [10]. 4. the electroplated zn layer may be replaced with galvanized zn coating of higher thickness, so as to have better corrosion resistance, although aesthetic look may be of concern [2]. failure analysis of diode components of electronic relay packages via thorough microstructural characterization 135 table 4: nature of corrosion types of various fasteners of two diode assemblies in comparative mode nomenclature (identification) of the parts corrosion phenomena remarks visual observation microstructural observation diode body set 1 diode shell is tarnished with a black product, while the stud seems to have experienced overheating. localized perforations in electroless nickel (en) coating on diode shell. corrosion debris containing zn, ca, k, fe and o was found. frequently pitting and occasionally uniform corrosion was observed. rust was observed up to 25 µm depth from the coated surface. corrosion at mns stringer-base metal interfacial regions. defective en coating is the principle reason for macroscopically visible corrosion. presence of zn and ca, k indicate galvanic effect of zn-coated other fasteners and environment effect respectively. set 2 it seems to be negligibly affected (no visible corrosion debris), while stud seems to have experienced overheating. rust was observed up to 100 µm depth from the en coated diode shell surface. nil observation of perforation in en coating, pitting and/or uniform corrosion. occasional presence of mns-induced corrosion. diode body may have been moderately corroded prior to the en plating. plain washer set 1 major portion is severely corroded, having a rust-like appearance. rusting was evident by presence of fe and o in corrosion product. uniform corrosion type and no pitting was observed. localized in-service mechanical damage of zn coating may have been responsible for corrosion. set 2 it does not reveal any sign of corrosion. no trace of corrosion, while examined even microstructurally under sem. this is due to superior corrosion resistance of passivated/preoxidized aisi 316 type of stainless steel (both uniform and pitting type) to that of zncoated low carbon steel. spring washer set 1 it seems to be negligibly affected. zn-o rich principal phase constituent with trace amount of fe was seen in quite uniform thickness along major part of the cross-sectional microstructure. pitting type of corrosion was mainly seen. inception of corrosion process at some localized areas as a result of sacrificial action of the zn coating. set 2 major portion is severely corroded, having a rust-like appearance. this has shown rusting both in uniform and pit form. however, no product containing zn and/or o. mechanical damage of zn coating along major parts of the component prior to its installation in service may have been responsible for corrosion. nut set 1 major portion is light to moderately corroded and light-reddish rust like product was there in the threaded region. rusting was evident by presence of fe and o in corrosion product. frequent presence of pitting, and not uniform corrosion was observed. inception of corrosion process at threaded regions as a result of sacrificial action of the zn coating. in other regions, coating was intact and so no corrosion. set 2 major portion is severely corroded, having a strong reddish rust-like appearance. it was found to be affected by corrosion deep into the structure (100 µm from the surface) and that manifested as reddish rusts on the surface. frequent presence of uniform corrosion, and not pitting was observed. mechanical damage of zn coating along major parts of the component prior to its installation in service may have been responsible for corrosion. hazra and singh (2019): international journal of engineering materials and manufacture, 4(3), 124-136 136 6. the ni-coated and zn-coated components should not be in contact for minimizing the galvanic effect between them [11]. therefore, both the coating preferably should be of the same type. in this regard, ni coating for all the components (as applied on critical diode body here) seems to be the best solution [12], if not cost-prohibitive with respect to the expected minimized corrosion damage. 7. for set 2 assembly, there should be thorough inspection for the remaining unplated diode bodies of the same lot, where corrosion may be prevailing in each of those components, as is found in the present analysis. and, in case of the existence of confirmed corrosion, those components should not be used in either unplated or in plated condition in service. 8. for set 2 assembly, plain washer of aisi 316 stainless steel type should not be clubbed with zn-coated low carbon steel made spring washer and nut, wherein severe galvanic corrosion may result in. all those fasteners should be either of stainless steel type or of coated low carbon steel type. both zn-coated low carbon steel and passivated/pre-oxidized austenitic stainless steel may show same degree of corrosion resistance in some specific environments, however, the later would last longer than the former. 9. for set 2 assembly, stainless steel plain washer should not contain excess cr (≈ 20 wt.% in this case) than is required (12≤cr≤18, in wt.%, as in aisi 316 ) for reasonable corrosion resistance. this is to avoid brittle δ-ferrite phase formation, which may also affect the corrosion resistance of austenitic matrix by sucking more and more cr into it. schaffler diagram should be consulted for desired compositional balance in this regard [13]. also, solutionizing temperature should be maintained within 1050-1100 0 c and soaking time should be reasonably low to avoid that phase. reference 1. http://www.tesla-institute.com/, last accessed on 10.05.2018. 2. http://www.surplus-electronics-sales.com/, last accessed on 10.05.2018. 3. miksic, b.a., martin, p.j. proceedings of 6th european symposium on corrosion inhibitors; ferrara, italy; 1985; 941-950. 4. miksic, b.a., vignetti, a. vapour corrosion inhibitors: successful field applications in electronics. nace corrosion conference; march 2000; orlando; paper # 7, 2000. 5. lee wy, eldridge jm, schwartz gc. reactive ion ethching induced corrosion of al and al-cu films. j appl phys 1981; 52: 2994. 6. vimala, j. s., natesan, m. and rajendran, s. corrosion and protection of electronic components in different environmental conditions an overview. the open corrosion journal, 2009, 2, 105-113. 7. ilangovan, s. investigation of the mechanical, corrosion properties and wear behaviour of electroless ni-p plated mild steel, international journal of research in engineering and technology, 2014, 03(04), 151-155. 8. introduction to surface engineering for corrosion and wear resistance (#06835g), www.asminternational.org, last accessed on 10.05.2018. 9. leiva-garcía, r., sánchez-tovar, r., escrivà-cerdán, c., garcíaantón, j. role of modern localised electrochemical techniques to evaluate the corrosion on heterogeneous surfaces, in nanotechnology and nanomaterials, ed. m. aliofkhazraei, june 11, 2014, isbn 978-953-51-1586-1. 10. deng, h., moller, p. (1993), effect of substrate surface morphology on the porosity of electroless nickel coatings, transactions of the institute of metal finishing, 2014, 71(04), 142-148. 11. richard, t. barrett, fastener design manual, nasa reference publication 1228, 1990, last accessed on 10.05.2018. 12. ünal, h. i., zor, s., gökergil, h.m. corrosion behavior of zn and ni coated carbon steels in 3% nacl, protection of metals and physical chemistry of surfaces, 2013, 49(5), 591-596. 13. robert e. physical metallurgy principles, international student edition, 1972. (a) (d) (e) http://www.tesla-institute.com/ http://www.surplus-electronics-sales.com/ http://www.asminternational.org/