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European Journal of Applied Sciences – Vol. 13, No. 02
Publication Date: April 25, 2025
DOI:10.14738/aivp.1302.18421.
Yang, C.-C., Vien, T. T. T., & Lin, Y.-S. (2025). The Cold Forming Analysis of Stainless Battery Bolts. European Journal of Applied
Sciences, Vol - 13(02). 72-83.
Services for Science and Education – United Kingdom
The Cold Forming Analysis of Stainless Battery Bolts
Chih-Cheng Yang
Department of Mechanical and Automation Engineering,
Taiwan Steel University, Taiwan
Thi Thu Trang Vien
Graduate School of Mechatronic Science
and Technology, Taiwan Steel University, Taiwan
Yung-Sheng Lin
Graduate School of Mechatronic Science
and Technology, Taiwan Steel University, Taiwan
ABSTRACT
A multi-stage cold forming process for the manufacture of stainless battery bolts is
studied numerically with AISI 316 stainless steel in this study. The cold forming
process through five stages includes preparation and centering for backward
extrusion, backward extrusion over a die pin, two upsetting operations, and
square trimming. The numerical simulations of cold forming are carried out using
the finite element code of DEFORM-3D. The formability of the workpiece is studied,
such as the effect on forming force responses, maximum forming forces, effective
stress and strain distributions and metal flow pattern. In the five-stage forming
process, in the two upsetting and the square trimming forming stages, the effective
stresses in the head of the workpiece are significantly high, and the effective
strains are also significantly high due to large deformation. The flow line
distributions are also very complex in which the flow lines in the trimming region
of the upset head are severely bent, highly compacted, and eventually fractured
due to excessive trimming. For the maximum axial forming force, the fourth stage
of secondary upsetting to form a cylindrical head to a larger outer diameter is
347.2 kN, which is the largest among the five stages due to the large amount of
upsetting. However, for the forming energy, the third stage, which the workpiece is
firstly upset into a conical shape, is 530.1 J, which is the largest among the five
stages due to longer acted axial forming stroke. The total maximum axial forming
forces from the first to the last stages are 597.1 kN and the total forming energies
are about 1.36 kJ.
Keywords: cold forming, stainless battery bolt, square trimming, formability, forming
force.
1. INTRODUCTION
Cold forming processes are performed at room temperature and widely used in the
manufacture of various parts. Multi-stage cold forming is used in many industries, especially
in the manufacture of fasteners and special parts. High mechanical properties, good surface
appearance and good precision are usually achieved without further processing. Multi-stage
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Yang, C.-C., Vien, T. T. T., & Lin, Y.-S. (2025). The Cold Forming Analysis of Stainless Battery Bolts. European Journal of Applied Sciences, Vol -
13(02). 72-83.
URL: http://dx.doi.org/10.14738/aivp.1302.18421.
cold forming is a high-speed forming process in which the billet is formed sequentially
through multiple stations [1].
In the cold forming process, the prediction of forming forces and stresses is significance for
the design of punches and dies and the selection of forming machines. There are many cold
forming applications that use numerical simulation to predict and analyze the forming design.
Altan and Knoerr [2] applied two-dimensional finite element method to study suck-in type
extrusion defects, bevel gear forging, stress analysis of forging tools and multi-stage cold
forging design. Lee et al. [3] used the rigid-plastic finite element method to design a multi- stage cold forging process sequence to form a constant velocity joint housing with shaft. They
studied velocity distributions, effective strain distributions, and forging loads, which provided
useful information in process design. A numerical simulation technique for the forging
process with a spring-attached die was proposed by Joun et al. [4], which used a penalty rigid- viscoplastic finite element method with an iterative force balance method. They explored the
significance of metal flow lines on quality control and the influence of spring-attached dies on
metal flow lines and forming load reduction. Roque and Button [5] applied ANSYS commercial
finite element software to model a forming operation. They developed models to simulate ring
compression testing and upsetting operations, a stage in the manufacturing process for
automotive starter parts.
MacCormack and Monaghan [6] proposed a three-stage cold forming process to form the
spline shape of the head of aerospace fasteners. They gained insight into the operation by
numerically analyzing strain, damage, and flow patterns in three stages. To analyze the
formability of the multi-stage forming process, Park et al. [7] used the finite element method
to establish a systematic process analysis method for the multi-stage forming of the constant
velocity joint outer ring. Farhoumand and Ebrahimi [8] applied the FE code of ABAQUS to
analyze the forward-backward-radial extrusion process and studied the effects of geometric
parameters such as die corner radius and gap height as well as process conditions such as
friction on the process. The numerical results were compared with experimental data in terms
of forming loads and material flow lines in different regions. The hardness distribution of the
longitudinal section of the product was used to verify the strain distributions obtained by
numerical analysis. Jafarzadeh et al. [9] applied the DEFORM-3D finite element code to study
the lateral extrusion process and analyzed the influence of some important geometric
parameters such as initial billet dimensions, gap height and friction conditions on the
required forging loads, material flow patterns and effective strain distributions. This study
analyzed and compared 4 and 5 stages of fasteners. They used the DEFORM-3D FE code to
inspect the effective stresses, strains, and velocities from billet to finished product. An
application of finite element analysis in the prediction and optimization of bolt forming
process was presented by Paćko et al. [10]. They studied bolt forming process consists of six
stages, including shearing, three upsetting stages, backward extrusion, and trimming. Several
tool modifications were proposed and analyzed using numerical simulation. Yang and Lin [11]
conducted numerical and experimental investigations on two forming modes of two-step
extrusion of AISI 1010 carbon steel. The numerical results of effective strain distributions
were consistent with the experimentally measured hardness distributions.
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European Journal of Applied Sciences (EJAS) Vol. 13, Issue 02, April-2025
Ku [12] proposed a two-stage cold forging process for manufacturing AISI 1035 steel drive
shaft with internal spline and spur gear geometry. Francy et al. [13] used DEFORM-3D
software and Taguchi method to optimize the input process parameters in the extrusion
process. The simulations were performed using DFORM-3D software to predict the minimum
force achieved in cold forward extrusion process. Obiko et al. [14] applied DEFORM 3D to
perform three-dimensional finite element analysis to study the plastic deformation behavior
of X20CrMoV121 steel during forging process. They studied the effect of forging temperature
on the strain, stress and particle flow velocity distribution during forging process. Petkar et al.
[15] proposed the use of a multi-layer feed-forward artificial neural network (ANN) model to
determine the effects of process parameters such as billet size, reduction ratio, punch angle
and land height on the cold forging backward extrusion forming behavior (i.e., effective stress,
strain, strain rate and punch force) of AISI 1010 steel. Finite element simulation along with
the developed artificial neural network model scheme could help the cold forging industry to
minimize the cost and time of process development. Lee et al. [16] proposed the use of a
multi-stage cold forging process to reduce the manufacturing cost of the solenoid valve while
meeting dimensional accuracy and performance. The forming process is divided into six
stages to improve the dimensional accuracy of the armature outer diameter, overall length
and slot portion.
Yang and Liu [17] conducted numerical and experimental investigations on a five-stage cold
forming process of mild steel AISI 1010 relief valve regulating nuts. The numerical simulation
of the forming force growth tendency was consistent with the experimental results. The
effective strain distributions were consistent with the measured hardness distributions. The
highly compact grain flow lines also led to higher hardness. Yang et al. [18] conducted a
numerical study on the multi-stage cold forming process for manufacturing eccentric parts of
mild steel AISI 1022. The formability of the workpiece was numerically investigated, such as
the effect on forging load responses, maximum forging loads, effective stress and strain
distributions, and metal flow patterns. Although the total maximum axial forging load of four- stage forming was less than that of five-stage forming, the maximum lateral forging force in
the last stage of four-stage forming was almost 5 times that of the last stage of five-stage
forming. Increasing the lateral forging force might cause wear and damage to the punch. Tao
et al. [19] aimed to determine an appropriate cold forging process for thin-walled A286 super
alloy tube with ideal forming quality. The effects of two forging processes using reverse
forging sequence on the forming defects and hardness distribution of thin-walled tubes were
analyzed through finite element simulation. Based on the three-dimensional finite element
model, Wan et al. [20] analyzed the residual stress distribution around the cold extrusion
internal thread of 42CrMo4 high-strength steel plate hole structure under different edge
distance ratios. They established the multi-axial fatigue life prediction model of thread based
on the stress-strain method and the accuracy and feasibility of the prediction model were
further verified by fatigue experiments. The research showed that the improved fatigue
prediction model gave a satisfactory accuracy in predicting the fatigue life. Yang et al. [21]
presented a numerical analysis of three-stage cold forming process for the manufacture of
AISI 316 stainless steel Allen screws and hexalobular socket screws. In the three-stage
forming process, in the forming stages of two upsetting and one backward extrusion at the
upper face of the workpiece, the effective stresses in the head of the workpiece are
significantly high, and the effective strains are also significantly high due to large deformation.
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Yang, C.-C., Vien, T. T. T., & Lin, Y.-S. (2025). The Cold Forming Analysis of Stainless Battery Bolts. European Journal of Applied Sciences, Vol -
13(02). 72-83.
URL: http://dx.doi.org/10.14738/aivp.1302.18421.
In the three-stage forming process, including two upsetting and one backward extrusion
forming stages, the effective stresses at the upper face of the workpiece were significantly
larger, and the effective strains were also larger due to the larger deformation. Winiarski et al.
[22] proposed a new method for forming flanges in hollow parts. The process consisted of an
extrusion with two dies that moved in an opposite direction to that of the punches. This
particular kinematics of the tools made it possible to form two flanges simultaneously in a
single tool pass.
In this study, the numerical simulation of a five-stage cold-forming process for the
manufacture of AISI 316 stainless steel battery bolts is presented. The forming process
includes preparation and centering for backward extrusion, backward extrusion over die pin,
two upsetting operations, and square trimming. The numerical simulation of cold forming is
conducted using the FE code of DEFORM-3D. The forming load responses are calculated and
the metal flow pattern, effective stress and effective strain at various deformation zones are
analyzed.
2. MATERIALS AND METHODS
The manufacturing process of the stainless battery bolts is multi-stage cold forming through
five stages. A cold-forging quality AISI 316 stainless steel wire coil is used in the cold-forming
analysis. The chemical composition of the alloy steel wire is shown in Table 1.
Table 1: Chemical composition of AISI 316 stainless steel wires (wt.%).
C Mn P S Si Mo Ni Cr
0.08 2.0 0.043 0.025 1.0 2.5 10.0 16.0
The cold forming is numerically investigated using the finite element code of DEFORM-3D. A
billet of φ5.85mm × L43.5mm is cut by the shearing die and transfers to forming stations.
Figure 1 shows the three-dimensional and cross-section views for the initial billet and
product parts at five stages.
Due to cutting to length by shearing, both the ends of the cutoff billet are visibly deformed, as
shown in Figure 1. Therefore, the initial billet is no longer an axisymmetric cylindrical body.
For the first stage, as shown in Figures 1(a) and 1(b), the process includes flattening the billet
end and centering for the backward extrusion in the second stage. In the second stage, a cavity
of φ3.0 mm is formed at the bottom end with a depth of 5.0 mm by using a punch tool
mounted in the die and with a reduction in area of 25.6% for the backward extrusion. Then,
the workpiece is moved to the third stage in which the upper end of the workpiece is upset
into a conical shape, and then moved to the fourth stage where the workpiece is further upset
into an approximately cylindrical shape with a height of 4 mm. In the final stage, the
workpiece is trimmed into a thick square shape at the head. The deformation energy is
=
L
E Fdl
0
(1)
where F is forming force and L is total acted forging stroke.