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Al-Khwarizmi 

Engineering 

Journal 
 

Al-Khwarizmi Engineering Journal, Vol. 15, No. 4, December, (2019) 

P. P. 55- 63 

 

 

Effect of Pre-Tension and Orientation on the Springback Behavior of 

the Sheet Brass 65-35 
 

Aseel Hamad Abed*              Anwar Hassan Zabon** 
*,** Department of Production Engineering and Metallurgy Engineering/ University of Technology 

*Email: aseelmo1972@gmail.com  
**Email: anwar2238@gmail.com  

 
(Received 15 April 2019; accepted 9 September 2019) 

https://doi.org/10.22153/kej.2019.09.005 
 

Abstract 
    

One of the most important phenomenon that occurs in sheet metal forming processes is the spring-back, which 
causes several geometrical alterations in the parts. The accurate prediction of springback after bending unloading is the 
key to the tool design, operation control, and precision estimate concerning the part geometry. This study investigated 
experimentally the effect of pretension in three rolling direction (0, 90, 45 degree) on the springback behavior of the 
yellow brass, sheet under V shape bending die. The pre-tension ranges from five different levels starting of 11% to 55% 
from the total strain in each rolling direction by regular increase of 11 %, then bent on a V-die 90 degree for the 
springback estimate. From experiment the results revealat that the springback increment with increase pretension ratio 
and the springback in 45° rolling direction is considerable than the sbringback in 90° rolling direction and the 
springback in 90° is greater than the sbringback in 0° rolling direction. 
 

Keywords: Pretension, orientation, springback, Brass 65-35. 

 
 

1. Introduction 
 
Sheet-metal forming processes (SMFP) can be 

divided into two groups: cutting processes and 
plastic deformation processes. The advantage of 
the sheet metal parts that the material has a high 
yield strength (Yσ) and a high elastic modulus 
(E), so that the parts created can be tough to have 
a good strength-to-weight ratio. A large number 
of techniques used to make sheet metal parts. One 
of the most widely applied metals forming 
operation is bending. By this technology, 
materials can be processed with various cross 
sections (sheet metal, bars, rods, pipes, wires. 
However, bending of sheet metal) most frequently 
used in industrial practice. First of all is in the car 
and ship building industry, there are different 
types of metal bending operations, one of the 
uttermost significant sheet metal bending 
operations is the (V–Die) bending [1]. Statement 
of the closing shape of the part after unloading 

(loading taken away) is a actual problem In 
manufacturing operation, In further, is necessary 
to design suitable tooling so as to lessen the effect 
of elastic recovery or springback (SB) in sheet 
bending which is a widespread phenomenon in 
(SMFP), which leads to some geometrical 
changes in the parts [2]. After completing the 
bending process of the punch, the material 
attempts to return to its original state due to the 
elastic stresses occurring in the deformation zone 
of sheet metal but it cannot return due to the 
permanent plastic deformation. Therefore, the 
sheet metal opens backwards slightly and reveals 
the spring back [3]. Brass an alloy mainly include 
zinc (Zn) and copper (Cu), is wide used in diverse 
manufacturing due of their superior formability, 
strength to weight ratio, as well elevated corrosion 
resistance, and ductility. Auto manufacturing is 
without fail in need of swift and strong 
automotive piece consequence it is feasible to 
production various parts and manufactured for 



Aseel Hamad Abed                            Al-Khwarizmi Engineering Journal, Vol. 15, No. 4, P.P. 55- 63 (2019) 

 

56 
 

automobile implementation using the brass alloy 
[4]. In the past years, oversize of numerical and 
theoretical studies to foretell the (SB) 
characteristics of sheet metal had been carried out. 
Investigated experimental and numerical the 
effect of dwell time on springback value of sheet 
material in V shape bending with different rolling 
direction and holding time in work pieces material 
[5]. Springback reduces with increase in yield 
stress (Yσ), compression depth, strain hardening 
(n), Young’s modulus (E) and increasing 
thickness or decreasing the bending angle and The 
binders can be used to reduce springback effect 
and also helps to distribute the stress evenly [6]. 
Investigated a die angle optimization method for 
reduce of (SB) in Sheet metal bending operation 
in a (V-bending) die [7]. Studied the effect of 
orientation and widths of the bending parallel, to 
the rolling direction on the slab. Then extended 
the variation quasi-static parameter with different 
punch velocities in two steel materials [8]. 
Presented the evaluated springback effect under 
various thicknesses and angles and using finite 
element method (FEM) for (SB) statement of 
arbitrary form [9]. Studied the effect of three 
parameters (punch angle, die opening and sheet 
width) on springback in sheet metal V-bending of 
steel sheet and determine the contribution of each 
process parameters towards springback effect 
[10]. Introduced the cold-forming process using 
explicit dynamic (FEM) and discussed the effect 
of thickness and curvature on springback of hull 
sheets was [11]. Performed study and compare the 
spring back effect of two materials (AMS 5504 & 
Aluminum alloy) also investigated the causes for 
spring back effect and its remedial factors. So 
using finite element method in ANSYS software 
to approximation process is carried out [12]. It 
should be note that the previous research above 
studies the effect of many parameters on 
sbringback. The objective of present work is to 
know the behavior of the phenomenon of 
sbringback in case the sample used is 
predetermined in the pre-tension process in three 
rolling direction and their influence in the 
definitive shape of the product is positive or 
negative. 

 
 

2. Experimental Equipments 
2.1. Materials 

 
The yellow Brass Sheet Material was used in 

this work. It is called brass 65-35 (C26800) 
according to (ASM) American Society of 
Metallic, it has excellent cold workability and 

widespread usage in the industry [13]. With sheet 
thickness (0.7) mm, to know the material 
characterization of it must be testing Chemical 
composition, in Table (1) listed the results of the 
chemical composition carried out at the 
Specialized Institute for Engineering Industries in 
Iraq, with the ASM caracterization. 

Table 1, 

Chemical composition and the ASM for Brass 65-

35. 

Elements EXP. ASM 

Zn% 35.23 35 
Pb% 0.007 0 
Mn% 0.00 0 
Sn% 0.001 0 
P% 0.007 0 
Si% 0.001 0 
Fe% 0.021 0 
Ni% 0.001 0 
Al% 0.002 0 
Cu% 64.7 65 

 

 

2.2. Material Properties 
 

To determine the mechanical properties of the 
sheet must be performing to tensile test. the 
specimens were first cut from the sheet and then 
made according to ASTM (American Society for 
Testing of Materials) standard E-8M specification 
[14], as shown in fig. 1. 

 

 
 

Fig. 1. Dimensions of tensile specimen. 
 
   As shown in fig. 2. The specimens were fixed 
carefully by the gripper, on universal testing 
machine WDW-200E, model (200E) electro-



Aseel Hamad Abed                            Al-Khwarizmi Engineering Journal, Vol. 15, No. 4, P.P. 55- 63 (2019) 

 

57 
 

mechanical load frame with mechanical grips 
having maximum test force (200 KN) with 
accuracy of testing ±1% of indicated value, the 
relative error of displacement is ±5 %, and the 
speed range of cross beam is 0.1 mm/min ~ 500 
mm/min, valid testing space 600 mm. This test 
was done in Strength of Materials laboratory in 
Department of Production Engineering and 
Metallurgy /University of Technology. Strength 
of Materials laboratory, under cross head speed 5 
mm/min, the specimen it loaded until fracture 
occurred. Nine tensile specimens were tested in 
three directions (0°, 45°, 90°) by three samples in 
each direction in order to take the average values 
to reduce the errors obtained from the 
measurements, as shown in fig. 3. 
 

 
 

Fig. 2. universal testing machine WDW model 200E 

electromechanical load frame with mechanical 

grips. 

 

 
 

 
Fig. 3. Tensile specimens (a) before test (b) after test 

The Mechanical Properties of it in three directions 

Rolling (0 ̊), Diagonal (45 ̊) and Transvers (90 ̊). 
 

 

Taguchi Methods for Designing 

Experiments 

 
     The mechanical  properties of yellow brass as 
(ASM) illustrated in table 2. While the relation 
between the true stress and true strain of brass 
sheet in three different directions is depicted in 
fig. 4. 
 

 
 

Fig. 4. True stress-strain curves of Brass 65-35 sheet 

in three different directions.

Table 2, 

 Mechanical properties of in three directions. 

Property Yield 

Strength 

(MPa) 

Ultimate Tensile 

Strength 

(MPa) 

%Elogation  

to Failure 

Buisson,s 

ratio 

Rolling (0o) 89 293 61 0.353 
Diagonal(45o) 52 245 64 0.243 
Transvers(90o) 64 270 55 0.239 
ASM 97 317 65 0.355 



Aseel Hamad Abed                            Al-Khwarizmi Engineering Journal, Vol. 15, No. 4, P.P. 55- 63 (2019) 

 

58 
 

 

2.3. Dies Used 
 

This study examined V-die bending tool, 
which designed and manufactured according to 
the standard specifications and consisted of two 
sections (punch and general die) both of them 
formed from (CK45). The first one is the general 
die, which is called lower die of opened type 90° 
angle in bottom bending. It has a rectangular 
shape of (99 × 108) mm and the height (48) mm 
with bending depth about (19) mm and opening 
die (40) mm. the second one is the upper die, 
which called the punch having 90° angle, as 
shown in fig. 5. The fixed velocity of the upper 
die is about (25) mm/min. 

 
 

 
 

Fig. 5. The shape and dimension of Die and Punch. 

 

2.4. Springback Test Samples 
    

Evaluation of the springback amount by 
implementing a sequence of experiments was the 
base of this work. In order to perform the 
experimental work, the testes must be a 
rectangular platelet (50 x 100) mm, according to 
template user as shown in fig. 6. 

 

2.5. Pre-Tension   
    

The specimen was prepared following the 
rolling direction. Considering the maximum strain 
of 0.12 (where the local necking happens after this 
point) under the uniaxial tensile loading path, five 
pre-tension states are used of 11%, 22% , 33% , 
44% , and 55% , from the total strain in each 
rolling direction with a steady increase of 11%  
were selected to assign on the samples. The 
punching performed at a constant deformation 
rate of (5 mm/min) and then unloaded at the same 
deformation rate, as shown in fig. 7. 
 

 
 

Fig. 6. Dimension of specimen's springback. 

 

 
 

Fig. 7. Five different pre-tension levels used in three 

directions. 

 

 

 

 

 

 

 

 

 



Aseel Hamad Abed                            Al-Khwarizmi Engineering Journal, Vol. 15, No. 4, P.P. 55- 63 (2019) 

 

59 
 

 

2.6. Experimental Bending Devices 
     

Agene universal testing machine model 
WDW-200E was used in the experimental work 
for the specimens in bending which was standard 
with wedge-shaped stretching attached, 
compression and bending, with the user and other 
attached to the form, as shown in fig. 8.  

The bending tests worked at a (25 mm/min) 
deformation speed, before that, the die and punch. 
In were loaded, the beginning, nine specimens 
without tension were bending at rate of three 
samples for each direction to tack the average 
values of them in order to reduce the errors 
obtained from the measurements. Then, bending 
45 sample that were pre-tensioned with five 
different levels of three directions at a rate of 15 
sample for each direction (0, 45, 90) degree in the 
same old groove, where the sample without 
tension were bent as shown in fig. 9. 

 

 
 

Fig. 8. Bending Device. 
 

 
 

Fig. 9. Bending the Sample in Three Rolling 

Direction. 
 

2.7. Springback Measured 
  

The springback angle is the difference between 
sheet angle αf which formed after raising the load 
where the part tends to recover elastically after 
bending and its bend radius becomes larger when 
the tools are taken away the outer radius of the 

workpiece and punch angle αi or which called 
loading bending angle when punch / dies 
configuration in closed position, as shown in fig. 
10. 
Δα = αf ˗ αi                                                     …(1) 
    Will the springback factor is defined by the 
ratio of the final bending angle and to the loading 
bending angle, in case K = 1, it is refers to no 
spring back (αi = αf) but if K = 0 it refers to that 
complete elastic recovery of the bent material 
takes place     (αf = 0). 
K= α f / α I                                                      …(2) 
    By a Mitutoyo 187-907 tool universal bevel 
protractor with a magnifying glass was used for 
the precise reading of angles on workpiece 
features or setting angle on machine tools 
hardened stainless steel construction that has 
blade length 150 mm. A high precision angle 
gauge was used for the accurate angle 
measurement of all angles, as shown in fig. 11. 
 

 
Fig. 10. Illustrate the difference between the final 

bending angle αf and loading bending angle αi. 
 

 
Fig. 11 – a. The measuring device Mitutoyo 187-907. 

(b) The device while measuring the angle of the 

sample. 

 
 

3. Results and Discussions  
 
Mensuration of springback can be defined as a 

difference between the angle after loading and 
after unloading. The measured values of 
springback and the calculated values of 
springback factor (Ks) and values of pre-tension 
were measured for each specimen for the two 
directions as shown In Table (3). The results show 
that the higher Percentage of pre-tension has 
leaded to increase the change in length (∆L) and 



Aseel Hamad Abed                            Al-Khwarizmi Engineering Journal, Vol. 15, No. 4, P.P. 55- 63 (2019) 

 

60 
 

greater the springback factor so thus increasing 
the springback there were situations whereby the 
final bending angle becomes bigger.     Fig. 12 
show comparison between springback calculated 
with different direction to the rolling at different 
pre-tension. Where it is clear that the pre-tension 
is a positive relationship to the springbacks and 
spring backs factor, i.e. the springback increases 
with the increase in pre-tension. as well the 
springback is higher in 45 degree to the rolling 
direction than in 90 degree to the rolling direction, 
and the springback is higher in 90 degree to the 
rolling direction than in parallel rolling direction. 
The main reason to the springback due to increase 
of dislocation density, which lead to the variation 
of mechanical behavior. Strain is as well play big 
role in springback result, where the increasing in 
number of strain hardening will raise the value of 
springback due to Bauchignerʼs influence, which 
authorize the material to follow dissimilar route 
through (loading – unloading) cycles. Each of 
forming operation will happen in the plastic zone. 
wherefore to estimate or to analyses springback, 
nonlinear material attribute whose will adjust 
(stress - strain) relationship in the nonlinear region 
are indispensable [15]. 

 

 
 

Fig. 12. Variation of the measured spring back with 

pre-tension in three directions. 

 

    The pre-tension process has resulted in an 
increase in sample length from its original length 
(ΔL) as shown for each sample in table 3.  
Fig. 13 show the relation between the change in 
length and spring back in Parallel to rolling 
direction (0º), (45º) degrees to the rolling 
direction and (90°) respectively. Where, it is clear 
that the change in length has a positive 
relationship to the springback i.e. the springback 
increases with increasing change in length. This 
leads to decrease the thickness, and the thickness 
has an inverse relationship with springback. 
 

 

 
 

Fig. 13. Relation between the change in length and spring back in three rolling direction. 

 
Fig. 14 show comparison between springback 

degrees calculated with different direction to the 
rolling at different change in length, which shows 
that the springback is higher in 45 degree to the 
rolling Direction than in (90°, 0°) to rolling 
Direction respectively. The sheet metal is defined 
as having planar anisotropy when that give 
various flow strengths in various directions in the 
plane of the plate so the yellow brass is 
anisotropy, perpendicular, diagonal and parallel to 

the rolling direction assimilate the three vectors of 
the planar anisotropy. i.e. has different properties 
(Yield Strength, Ultimate Tensile Strength and 
Total tensile elongation) in different direction and 
that it has a great effect on the material properties 
this corresponds to the source no. [7]. Where 
proved that “the springback decreases with 
increase in yield stress, strain hardening but it 
decreases with increase in Young’s modulus and 
increasing thickness”. 

 

0

5

10

15

20

25

30

35

0% 11% 22% 33% 44% 55% 66%

sp
ri

n
g

b
a

ck
 a

n
g

le
s 

in
 d

e
g

re
e

 

pre-tension %

transver on rolling dirction

on rolling dirction

diagonal on the rolling dirction



Aseel Hamad Abed                            Al-Khwarizmi Engineering Journal, Vol. 15, No. 4, P.P. 55- 63 (2019) 

 

61 
 

Table 3, 

Experimental measurements of springback and springback factor.

 

 

 
 

Fig. 14. Comparison between relations measured 
springback with change in length on three rolling 
Directions.  
 

 

4. Conclusions 
 
The present work has reached the following 
conclusions:  
1. The pre-tension has a greater effect on the 

springback and springback factor, whereas the 
springback and springback ratio increase with 
the increase of pretension ratio so it has no 
positive effect on the springback 
compensation, and the pre-tension plays a 

remarkable role in the final sample geometry 
of the part.  

2. The change in length is positive relationship to 
the spring back whereas the springback 
increase with the of increase change in length.  

3. The orientation has a significant impact on the 
springback and springback factor. When the 
direction to the rolling angle is (45º), the spring 
back angle and spring back factor are higher 
than the (90º) for the direction to the rolling, 
while the lower spring back angle and lower 
springback factor resulted when the direction 
angle to the rolling is (0º). 
 

5. References 
 

[1] A. Ivaniševic, M. Milutinovi, B. Štrbac, and P. 
Skakun, “Stress state and spring back in v-
bending,” J. Technol. Plast., vol. 39, no. 2, pp. 
158–168, 2013. 

[2] D. K. Leu, “A simplified approach for 
distinguishing between spring-back and spring-
go in free U-die bending process of SPFC 440 
sheets,” Mater. Des., vol. 94, pp. 314–321, 
2016. 

[3] [M. Özdemİr, “Mathematical modeling of the 
effect of different parameters on spring back in 
sheet metal formability process american 
journal of engineering research (AJER),” no. 
10, pp. 198–205, 2017. 

Springback factor  Springback 

Pretention  
Workpiece Direction 

angle 
Change in 
length  (∆L) 
in mm 

Percentage of total 
 pre-tension 

1.088 8 ̊ 0 0  % 1 0° 
1.122 11  ̊3.11 11 % 2 

 
1.144 13  ̊6.2 22 % 3  
1.166 15  ̊9.3 33 % 4 

 
1.188 17  ̊12.4 44 % 5  
1.211 19  ̊15.5 55 % 6 

 
1.188 17  ̊0 0  % 1 45° 
1.211 19  ̊3.5 11 % 2 

 
1.244 22  ̊7.05 22 % 3  
1.277 25  ̊10.55 33 % 4 

 
1.311 28  ̊14.1 44 % 5  
1.344 31  ̊17.65 55 % 6 

 
1.44 13  ̊0 0  % 1 90° 
1.17 15  ̊2.95 11 % 2 

 
1.2 18  ̊5.95 22 % 3 

 
1.23 21  ̊8.93 33 % 4 

 
1.27 24  ̊11.9 44 % 5 

 
1.3 27  ̊14.85 55 % 6 

 



Aseel Hamad Abed                            Al-Khwarizmi Engineering Journal, Vol. 15, No. 4, P.P. 55- 63 (2019) 

 

62 
 

[4] S. K. Panthi, N. Ramakrishnan, M. Ahmed, S. 
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[6] M. Arunkumar, “Design and analysis of a 
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[7] A. Jabbari, “Springback reduction in sheet 
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[8] M. Krinninger, D. Opritescu, R. Golle, and W. 
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[9] M. S. Gupta and D. R. Reddy, “Design and 
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[10] R. D. Gedekar, S. R. Kulkarni, and M. B. 
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[12] Z. Yue, J. Qi, X. Zhao, H. Badreddine, J. 
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[13] V. Drossou-Agakidou et al., Administration 
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[14] W. Materials, R. Head, and W. Screws, 
“NOTICE: This standard has either been 
superseded and replaced by a new version or 
discontinued. Contact ASTM International 
(www.astm.org) for the latest information. 
Standard Test Methods for Mechanical 
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80–88, 2016. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
 

 

 

 

 

  



 )2019( 55- 63، صفحة ٤د، العد15دجلة الخوارزمي الهندسية المجلماسيل حمد عبد                                                                  
 

63 
 

 

 

 

رالرجوعية في صفيحة النحاس االصفاهرة ظتأثير الشد المسبق واتجاهية المعدن على سلوك   
 

**انوار حسن زبون                   *اسيل حمد عبد  
ةالتكنولوجي ةالجامع /م هندسة االنتاج والمعادنقس،***  

aseelmo1972@gmail.com : البريد االلكتروني* 
anwar2238@gmail.com : البريد االلكتروني** 

 
 

ةالخالص  
 

في االجزاء. ان التنبؤ الدقيق احد اهم الظواهر التي تحدث في عمليات تشكيل الصفائح المعدنية والتي تسبب عدة تغييرات هندسية ظاهرة الرجوعية  تعد
هذه الدراسة تحرت  للرجوعية بعد رفع الحمل بعملية الحني هي المفتاح  لعدة التصميم والسيطره على العمليات والتخمين الدقيق  فيما يتعلق بهندسة االجزاء

وك ظاهرة الرجوعية في صفيحة النحاس االصفر بعملية ) درجة على اتجاه الدرفلة على سل٠٬٤٥٬٩٠اتجاهات ( ةبثالثبشكل تجريبي تأثير الشد المسبق 
 %١١قابلية الشد الكلي  لكل اتجاه بزيادة منتظمة مقدارها  من %٥٥الى  %١١مستويات مختلفة تبدأ من  ة، تم الشد المسبق بخمس V الحني قي قالب شكل

هرت النتائج العملية ان الرجوعية تزداد بزيادة نسبة الشد وان ظادرجة لغرض تخمين الرجوعية ،  ٩٠زاوية  Vومن ثم تم حني العينات في قالب شكل 
درجة اكبر من الرجوعية باالتجاه  ٩٠درجة وان الرجوعية باالتجاه  ٩٠درجة على اتجاه الدرفلة اكبر بكثير من الرجوعية باالتجاه  ٤٥الرجوعية باالتجاه 

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