73- 81 Al-Khwarizmi Engineering Journal,Vol. 11, No. Experimental Study Hydroforming Muthanna H *,**,***Department (Received Abstract Lightweight materials is used in the sheet manufacturing of complex structural components into a single body with high structural stiffness. Sheet hydroforming has been successfully developed in industry s The aim of this study is to simulate hydroforming process, stresses, and strains distribution) with for aluminum alloy (AA5652) sheets with (AHT) respectively in the circular die approaches show the same tendency that an improvement formability AHT for same metal. Keyword : sheet hydroforming , stress and strain distribution, aluminum alloy, forming limit diagram. 1. Introduction Hydroforming is a forming technology for tube and sheet material aiming at high part strength and the manufacturing of complex geometries in one process step. Even straining of the material caused by the fluid pressure leads to a uniform deformation in the sheet, which improves the dent resistance of the hydroforming part compared with conventional stamped parts and the uniform rise in yield strength in the used materials resulting in lower necessary wall thicknesses Lightweight materials, in particular, aluminum alloys have been widely used in automotiv aircraft industry as the high strength ratio of aluminum results in significant weight and fuel savings [2–3]. In addition to weight reduction, utilization of aluminum offers some other advantages such as better corrosion resistance, higher recyclability potential and Khwarizmi Engineering Journal,Vol. 11, No. 4, P.P. 73- 81 (2015) Study and Numerical Simulation ydroforming Process for Aluminum Alloy AA5652 Hamza Sadoon* Sadiq Jaffar Aziz Hiba AbdAli Jassim*** Department of Mechanical Engineering / University of Technology *E-mail: Dr.muthanna@yahoo.com **E-mail: zaqsam@hotmail.com ***E-mail: hibaabdali@yahoo.com (Received 31 March 2014 ; accepted 16 June 2015) in the sheet metal hydroforming process, because it can be adapted to the manufacturing of complex structural components into a single body with high structural stiffness. Sheet hydroforming has been successfully developed in industry such as in the manufacturing of the components of automotive simulate the experimental results ( such as the amount of pressure required to , and strains distribution) with results of finite element analyses (FEA with thickness (1.2mm) before heat treatment (BHT) circular die with cavity equals to (20mm) . The comparison of results by these two approaches show the same tendency that an improvement formability, also the plastic deformation is greatly enhanced sheet hydroforming , stress and strain distribution, aluminum alloy, forming limit diagram. Hydroforming is a forming technology for tube material aiming at high part strength and the manufacturing of complex geometries in one process step. Even straining of the material caused by the fluid pressure leads to a uniform , which improves the dent forming part compared with conventional stamped parts and the uniform rise in yield strength in the used materials resulting in lower necessary wall thicknesses [1] . Lightweight materials, in particular, aluminum alloys have been widely used in automotive and aircraft industry as the high strength-to-weight ratio of aluminum results in significant weight and . In addition to weight reduction, utilization of aluminum offers some other advantages such as better corrosion recyclability potential and increased energy absorption during a crash situation. 5XXX alloys, in particular, have the highest formability, and are used in automotive inner panels[4]. Automotive industry has a special interest in AA5754 because of its hig lightweight, strength and weldability properties [5]. However, because of their susceptibility to microstructural damage, aluminum alloy sheets generally exhibits a lower level of formability compared to typical sheet steels utilization of aluminum alloys in the automotive industry has been far behind of steel because of cost and formability issues at room temperature [7]. In this study, The sheet materials of al (AA5652 t = 1.2mm) was annealed by heavy electric furnace. The annealing temperatures considered for aluminum materials were 345°C. The holding time in the furnace was (1) hour and then cooled in the furnace. The specifications of Al-Khwarizmi Engineering Journal (2015) of Sheet AA5652 Sadiq Jaffar Aziz** nology because it can be adapted to the manufacturing of complex structural components into a single body with high structural stiffness. Sheet hydroforming uch as in the manufacturing of the components of automotive. the experimental results ( such as the amount of pressure required to nt analyses (FEA) (ANSYS 11) heat treatment (BHT) and after heat treatment The comparison of results by these two the plastic deformation is greatly enhanced sheet hydroforming , stress and strain distribution, aluminum alloy, forming limit diagram. increased energy absorption during a crash 5XXX alloys, in particular, have the highest formability, and are used in automotive inner . Automotive industry has a special interest in AA5754 because of its high ductility, lightweight, strength and weldability properties However, because of their susceptibility to microstructural damage, aluminum alloy sheets generally exhibits a lower level of formability compared to typical sheet steels [6]. Furthermore, utilization of aluminum alloys in the automotive industry has been far behind of steel because of cost and formability issues at room temperature In this study, The sheet materials of aluminum was annealed by heavy-duty electric furnace. The annealing temperatures considered for aluminum materials were 345°C. The holding time in the furnace was (1) hour and then cooled in the furnace. The specifications of Muthanna Hamza Sadoon furnace include maximum temperature 1000°C, 6.5 kW and 220 V to improve the softer metal and reduce internal stresses in addition to the change in the internal structure of the alloy homogeneity, making it more than it was before the fermentation process. Table 1, Chemical Composition of AA5652. Material Element %Si AA5652 Nominal composition 0.4 max. Actual composition 0.095 2.2 Uniaxial Tensile Test The uniaxial tensile test is the basis for defining mechanical properties of materials. It is standardized in ASTM standard E8M specification. The specimens were tested along the three directions, with the tensile axis being Fig. 1. Tensile specimen Table 2, Shows the mechanical properties of AA 5652 Material Young's modulus, E (GPa) AA5652 t = 1.2 mm BHT 70 AHT Al-Khwarizmi Engineering Journal, Vol. 11, No. 4, P.P. 74 furnace include maximum temperature 1000°C, improve the softer metal and reduce internal stresses in addition to the change in the internal structure of the alloy homogeneity, making it more than it was before the 2. Experimental Procedure 2.1 Chemical Composition The chemical compositions of sheet material were found out by spectrometry and are reported in Table (1). %Fe %Cu %Mn %Mg %Zn 0.4 max. 0.04 max. 0.01 max. 2.2-2.8 0.1 max. 0.197 0.002 0.013 2.33 0.018 The uniaxial tensile test is the basis for defining mechanical properties of materials. It is in ASTM standard E8M specification. The specimens were tested along the three directions, with the tensile axis being parallel (0o), diagonal (45 (90o) to the rolling direction (1) for specimens with round or rectangular cross sections. Table (2), illustrate properties of AA 5652 from tensile test after heat treatment respectively ensile specimen BHT and AHT( all dimension in mm). of AA 5652 from tensile test before heat treatment. Young's modulus, E (GPa) Strain hardening Index n Hardening coefficient K (MPa) 0.4 650 0.36 575 Khwarizmi Engineering Journal, Vol. 11, No. 4, P.P. 73- 81 (2015) Experimental Procedure Chemical Composition compositions of sheet material spectrometry and are reported %Cr %Al 0.15-0.35 Rem. 0.280 97 ), diagonal (45o), and perpendicular ) to the rolling direction as showed in figure for specimens with round or rectangular cross illustrate the mechanical from tensile test before and after heat treatment respectively . . Anisotropy factor R 0.77 1 Muthanna Hamza Sadoon Al-Khwarizmi Engineering Journal, Vol. 11, No. 4, P.P. 73- 81 (2015) 75 2.3 Hydroforming Sheet To find out the amount of applied pressure required for the hydroforming process and study the changes in stresses and strain generated in the sheet of aluminum AA5652 (t = 1.2mm) before and after annealing process. Hydroforming die consisting of two parts as show in Figure (2), upper and lower die. The depth of the lower die is (20mm) which was representing die cavity. While the upper die was represent chamber of oil. Blank holder force was 200N to prevent leakage between upper and lower die also to connect the sheet with lower die. Figure (3) shows the specimen shape before and after hydroforming process. (a) (b) Fig. 2. Hydroforming Die (a) lower die (b)upper die. Fig. 3. The specimen before and after hydroforming process. 2.4 Pressure and Depth Measurement A digital camera type Sony, model DSC- W670, 16.1 Mega pixels was used to record during the hydroforming process. The final results of applied pressure and forming depth can be obtained from the saved movie. In this work, gage pressure device is 600 bars used, the depth during the hydroforming process can be measured by a dial-gauge device. It is attached to the die by an adjective pin of (ф 3-0.006 mm) in diameter which is located in a deep drilled hole in lower half of die to be attached to the lower side of the aluminum sheet, the accuracy of dial-gauge is 0.01mm. 2.5 Forming Limit Diagram FLD represents the locus of the necked or fractured position of sheet metals in the space of in-plane principal strains, where ε1 is the major strain and ε2 is the minor strain. Fld was calculated to AA5652 BHT & AHT as shown in Fingers ( 4) & (5) to know formability of sheet metal also investigate the maximum strains can be endured without fractured . In order to be able to determine the local deformation of the formed sheet, line patterns with defined geometries (grids) are marked on the sheet specimens prior to forming. The subsequent forming process causes the line patterns to deform by an amount which depends on the local deformation experienced by the sheet part. Fig . 4. Forming limit diagram BHT. Fig . 5. Forming limit diagram AHT. ∈� % ∈� % ∈� % ∈� % Muthanna Hamza Sadoon Al-Khwarizmi Engineering Journal, Vol. 11, No. 4, P.P. 73- 81 (2015) 76 3. Finite Element Software Package ANSYS11 ANSYS is a commercial, finite element analysis, software package with capability to analyze a wide range of different problems [8]. For simulating the sheet hydroforming in a circle die processes, commercial FEA software ANSYS11 was used, in which the "Newton-Raphson" implicit approach was employed to solve nonlinear problem. In this approach, the stroke steps on outer surface of blank were defined explicitly over a time span. Within each step, several solutions (substepes or time steps) were performed to apply the pressure gradually. At each substep, a number of equilibrium iterations were performed to obtain a converged solution. Before each solution, the Newton-Raphson method evaluated the out-of- balance load vector, which was the difference between the restoring forces (the loads corresponding to the element stresses) and the applied loads. The 3-D 8-node structural solid element of SOLID95 was used for workpiece (blank).The tool set (die and blank holder) was modeled as rigid bodies. Fluid pressure was defined using a pilot node; this node was also employed to obtain the drawing force during the simulation. 4. Effective Stress & Strain Functions The work done in deforming the unit element is [9]: ��� . = ���� + ���� + ���� …(1) For a plane stress process, this becomes [9]: �� . = � ���� + � � �� � ��� …(2) �� � The plastic work done on a unit volume of material deformed in the tensile test to a true strain of ε1 (where σ2 = σ3 = 0) will be, from Equation (2). �� . = � ��� . = � � �� � ��� …(3) �� � i.e. the work done per unit volume is equal to the area under the true stress–strain curve. The plastic work done per unit volume in an increment in a process is given by Equation (1). It would useful if this could be expressed in the form ��� . = ��( �, �, �)���(��,��,��) …(4) As the element is yielding during deformation, a suitable stress function to choose is that given by the von Mises yielding criterion, which has already been shown to have the value of the flow stress. For plane stress this function is: [9] ��( �, �, �) = �√1 − " + "�# � …(5) This function is called the representative, effective or equivalent stress, , and if the material is yielding, it will be equal to the flow stress. For a general state of stress in an isotropic material the effective stress function is: % = &12'( � − �)� + ( � − �)� + ( � − �)�( …(6) In plane stress, the effective stress function is: % = * �� − � � + �� = +,1 − " + "�- � …(7) As indicated, if the material element is at yield, this function will have the magnitude of the flow stress, σf. The required strain function in Equation (4) can be found by substitution of the stress function. This function is known as the representative, effective or equivalent strain increment dε and for plane stress, the function is: ��%%% = ���(��,��,��) = */�'1 + 0 + 0�( ��� …(8) In a general state of stress it can be written as [9] ��%%% = &23'���� + ���� + ����( = &29'(��� − ���)� + (��� − ���)� + (��� − ���)�( …(9) In a monotonic, proportional process, Equations (8) and (9) can be written in the integrated form with the natural or true strains ε substituted for the incremental strains dε; i.e. [9] �̅ = &43'1 + 0 + 0�( �� …(10) �̅ = &23'��� + ��� + ���( …(11) �̅ = &29'(�� − ��)� + (�� − ��)� + (�� − ��)�( …(12) where, �,̅ is the representative, effective, or equivalent strain and it can be written in general form as the following5106. Muthanna Hamza Sadoon �̅ = 7 + 1√27 � 1&1 � 27 √7 � 10 � 0� Where, R represents an average normal anisotropy. The equation (14 ) is used to calculate the equivalent stresses [9] Ϭ9 � :�∈9�; 5. Results and Discussion Figure (6) shows the relationship between internal pressure and depth of AA5652 sheet before heat treatment at each load step. In this test the difference between the total internal pressure to form the sheet in both experiments is 4% .The total pressure is 120 bar in experimental test and 125 bar for simulation test. The maximum depth was (18 mm) in experimental test and (17.7mm) in simulation test. Fig. 6. Relationship between internal pressure and sheet depth (BHT). 0 20 40 60 80 100 120 140 0 5 10 p re s s u re ( b a r ) depth (mm) simulation experimental Al-Khwarizmi Engineering Journal, Vol. 11, No. 4, P.P. 77 …�13� an average normal The equation (14 ) is used to calculate the …( 14 ) shows the relationship between internal pressure and depth of AA5652 sheet before heat treatment at each load step. In this test the difference between the total internal pressure experiments is 4% .The total pressure is 120 bar in experimental test and The maximum depth was (18 mm) in experimental test and (17.7mm) Relationship between internal pressure and While Figure (7) illustrates the maximum depth is (19.8 mm) in experimental test and (19.4 mm) in simulation test of AA5652 sheet after heat treatment under applied pressure equals to that used in before heat treatment. Also, these figures illustrate the effect of heat treatment works cause rearrange the crystals of the metal and increases the formability of the metal for hydroforming which makes the depth of product AHT larger than the depth BHT with same pressure. Fig. 7. Relationship between internal pressure and sheet depth (AHT). Observed approach practical results as (3 ) and (4) with the results of the simulation program as shown in Figure calculating the highest stresses and strains is exposed as a result of the metal hydroforming process before and after heat treatment . Also shows the effect of heat treatment on the behavior of the metal during the hydroforming process, giving more ductility due to re the metal and lower resistance to the stresses to which it is faced.∈�,∈�, 15 20 simulation experimental 0 20 40 60 80 100 120 140 0 5 10 p re s s u re ( b a r ) depth (mm) Khwarizmi Engineering Journal, Vol. 11, No. 4, P.P. 73- 81 (2015) ) illustrates the maximum depth is (19.8 mm) in experimental test and (19.4 mm) in simulation test of AA5652 sheet after heat under applied pressure equals to that used in before heat treatment. Also, these figures illustrate the effect of heat treatment works cause rearrange the crystals of the metal and increases the formability of the metal for hydroforming epth of product AHT larger than the depth BHT with same pressure. Relationship between internal pressure and Observed approach practical results as Tables (3 ) and (4) with the results of the simulation Figures (8) and (9) for calculating the highest stresses and strains is exposed as a result of the metal hydroforming process before and after heat treatment . Also heat treatment on the behavior of the metal during the hydroforming process, giving more ductility due to re-crystallization of the metal and lower resistance to the stresses to ,∈�calculated from the 10 15 20 25 depth (mm) simulation expermental Muthanna Hamza Sadoon Al-Khwarizmi Engineering Journal, Vol. 11, No. 4, P.P. 73- 81 (2015) 78 grids on the cups , also �,̅ 9calculated by equations (13) and (14) .The observed results are in agreement with the finding of Ref. [ 11] . The reference used tube hydroforming processes of AA6060 while the current study fouced on sheet hydroforming of AA5652. Table 3, Experimental results of the final stage of half AA5652 (t =1.2mm) sheet BHT in a bulge region only. Table 4, Experimental results of the final stage of half AA5652 (t =1.2mm) sheet AHT in a bulge region only. (a) (b) Fig. 8. Relationship between internal pressure and equivalent stress of AA5652 (t =1.2 mm) sheet (a) BHT ( b ) AHT. 0 100 200 300 400 500 600 0 25 50 75 100 125 150 e q u iv e la n t s tr e s s ( M p a ) pressure (bar) before heat treat ment after heat treatment Pressure Grid mm Є1 Є2 Є3 <% =9 120 bar 0 0.3987 0.13914 -0.53784 0.5286 503 5 0.2613 0.09910 -0.3604 0.3521418 428 10 0.15651 -0.07823 -0.08028 0.156689 310 15 0.14188 -0.07323 -0.06865 0.14238 298 20 0.12321 -0.06823 -0.05498 0.124212 282 25 0.1159 -0.06011 -0.05579 0.116338 274 30 0.0965 -0.02356 -0.07294 0.0985923 257 Pressure Grid mm Є1 Є2 Є3 <% =9 120 bar 0 0.5115 0.2201 -0.7316 0.75069 518 5 0.3286 0.20449 -0.5331 0.53837 460 10 0.2931 0.1294 -0.4225 0.43289 425.3 15 0.2731 -0.1194 -0.1537 0.27381 361 20 0.253892 -0.083 -0.17089 0.2589 359.72 25 0.20054 -0.1205 -0.0800 0.20189 323.23 30 0.17800 -0.096 0.0817 - 0.17820 309 Muthanna Hamza Sadoon Al-Khwarizmi Engineering Journal, Vol. 11, No. 4, P.P. 73- 81 (2015) 79 (a) (b) Fig. 9. Relationship between internal pressure and equivalent strain of AA5652 (t = 1.2 mm) sheet (a) BHT (b) AHT. 6. Conclusions 1. Improving the elongation properties of the metal after heat treatment of the annealing process . 2. Upper value of equivalent stress and equivalent strain BHT were 503 and 0.5286 respectively while AHT become the equivalent stress and equivalent strain 518 MPa and 0.75069 . 3. The hardness increasing after hydroforming process because the work hardening that occur during the process . 4. The pressure required of hydroforming process was lowered AHT, because the characterization of the formability of metal improved . Notation σ1, σ2 , σ3 Principal stresses (MPa) ��, ��,�� Principal strains ------ % Effective stress (MPa) ̅ � ̅ Effective strain ------ α Stress ratio β Strain ratio L Specimen length mm w Specimen length mm dl Change in length mm dw Change in width mm dt Change in thickness mm 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 25 50 75 100 125 150 e q u iv a le n t s tr a in pressure (bar) before heat treatment after heat treatment Muthanna Hamza Sadoon Al-Khwarizmi Engineering Journal, Vol. 11, No. 4, P.P. 73- 81 (2015) 80 7. References [1] S. Novotny, M. Geiger, “Process design for hydroforming of lightweight metal sheets at elevated temperatures”, Journal of Materials Processing Technology 138, p.p594–599، (2003). [2] Verbrugge M, Lee T, Krajewski PE, Sachdev A, Bjelkengren C, Roth R, et al. Mass decompounding and vehicle lightweighting. Mater Sci Forum 2009;618– 619:411–8. [3] Montalbo T, Lee TM, Roth R, Kirchain R. Modeling costs and fuel economy benefits of light weighting vehicle closure Panels. 2008- 01-0370, SAE international; 2008. [4] Bolt PJ, Lamboo NAPM, Rozier PJCM. Feasibility of warm drawing of aluminum products. J Mater Proc Technol 2001;115:118–21. [5] Wowk DL. Effect of prestrain on the strain rate sensitivity of AA5754 sheet. Ph.D dissertation, Queen’s University, Canada; 2008. [6] Hosford W, Caddell R. Metal Forming. PTR Prentice Hall; 1993. [7] Ayres RA. Alloying aluminum with magnesium for ductility at warm temperatures (25–250 ºC). Metal Trans A 1979;10:849–54. [8] ANSYS9.0 manual. SASIP, INC, (2004). [9] Z.Marciniak, J.L.Duncan, and S.J.Hu, "Mechanics of the sheet metal forming". Second Edition, Butterworth-Heinemann (2002). [10] V. Gylienė and V. Ostaševičius, " Study of hydroforming by implementing necking criterion in FEM code" , ISSN 1392 - 1207. MECHANIKA. Nr.4(54) ,2005. [11] SAMI ABBAS HAMMOOD, "Numerical and Experimental Analysis of Tube Hydroforming in a Square Cross-Sectional Die " , M.S .C thesis , University of Technology, Department of Production and Metallurgy Engineering (2012). )EFG ،81 -73 )2015> 4، ا:.-د11-89> ا:BCارز7? ا:<5-/=> ا:7892 4567 123ة /.-ون 81 � ا����رو���� ا������ ����� ا��را� ا� ��� وا� �د ������ة ���ا$��#�"م � �� �� AA5652 ' *+*#( )�'ه � �ون', -� ***ھ 2 , � ,�� .��1 **�0دق . *،**،*** HIJ <=K=LMK=2:7.> / ا:<5-/> اM9:ا<=NB:B5KO:ا *?LوPOK:Qا -RPS:ا: Dr.muthanna@yahoo.com **?LوPOK:Qا -RPS:ا: zaqsam@hotmail.com hibaabdali@yahoo.com ***?LوPOK:Qا -RPS:ا : ا�045 <=:MT U ة-Y.2:ا Z[M=>:5=\ اWO: ]:وذ _`MFW:ا Z=Kab <=82T ?c زنB:ا اB8f2:ا jkl:2=> ا[ Z67 <=82.:ا m`MO5:ة اM[ME7 Bه ا:-را/> ھpھ q7 ان ا:<-ف ، m7MLPU m`MOL \7 تQM.FLQدات واM>NQا \RزBb 48T ا:BOا:? c? ) ا:ZSJ)P=2CO وU.- ا:87M.2> ا:PEارR> (mm 1.2)وK=S/AA5652 ]2IU> اB=52:Qم :q7 _`MFW (ANSYS11 )ا:Z=8EO ا:.-دي uY2T يP`دا v:MJ)20 mm (. ا:2.-نUMJ q=IEb w=3 q7 اT -.U 28.-ن: