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European Journal of Applied Sciences – Vol. 11, No. 3

Publication Date: June 25, 2023

DOI:10.14738/aivp.113.14862. Yang, C.-C., Sumampow, Y., & Cruz, S. N. D. (2023). The Cold Forming Analysis of Eccentric Parts. European Journal of Applied

Sciences, Vol - 11(3). 407-421.

Services for Science and Education – United Kingdom

The Cold Forming Analysis of Eccentric Parts

Chih-Cheng Yang

Department of Mechanical and Automation Engineering,

Kao Yuan University, Taiwan

Yoel Sumampow

Graduate School of Mechatronic Science and Technology,

Kao Yuan University, Taiwan

Sunshine Nazareno Dela Cruz

Graduate School of Mechatronic Science and Technology,

Kao Yuan University, Taiwan

ABSTRACT

In this study, a multi-stage cold forming process for the manufacture of eccentric

parts is studied numerically with low carbon steel AISI 1022. The forming

processes through five stages and four stages include two-step forward extrusion,

eccentric upsetting, and backward extrusion over a moving punch. The numerical

simulations of cold forming are conducted using the code of DEFORM-3D. The

formability of the workpiece is studied numerically, such as the effect on forging

load responses, maximum forging loads, effective stress and effective strain

distributions and metal flow pattern. The maximum effective stress of 819 MPa at

the third stage is the largest among the stages. The maximum effective stresses of

the last stages for the four-stage forming and five-stage forming are almost the

same. The effective strain distributions of the last stages for the four-stage forming

and five-stage forming are very similar. The flow line distributions of the last

stages both for the four-stage forming and five-stage forming are also very similar.

For the maximum axial forging force and forming energy, the third stage of

eccentric upsetting at the upper end is the largest among the stages. The total

maximum axial forging loads from the first to the last stages are 795.8kN for the

five-stage forming and 590.4kN for the four-stage forming; and the total forming

energies are about 0.751kJ for the five-stage forming and 0.671kJ for the four- stage forming. Although the total maximum axial forging loads and total forming

energy of the four-stage forming are smaller than those of the five-stage forming,

the maximum lateral forging force in the last stage of the four-stage forming is

almost five times that of the last stage of the five-stage forming. Increasing lateral

forging force may lead to wear and damage of the punch. Moreover, the inner

surfaces of the hexagonal cavity at the upper end are relatively uneven because of

simultaneous eccentric upsetting and backward extrusion in the last stage of the

four-stage forming.

Keywords: cold forming, eccentric parts, formability, forging load, lateral forging force.

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Services for Science and Education – United Kingdom 408

European Journal of Applied Sciences (EJAS) Vol. 11, Issue 3, June-2023

1. INTRODUCTION

Cold forging is performed at room temperature and is proverbially used in many industries,

especially in the manufacture of fasteners and special parts. Good tolerances, high mechanical

properties and good surface appearance are generally achieved without further machining.

Since the successful development of multi-stage forging machines, multi-stage cold forging

has been widely used to produce axisymmetric parts [1]. Multi-stage cold forging is a high- speed forming process in which billets are formed sequentially through multiple stations [2].

The cold forming process is widely used in the manufacture of various component products

such as screws, bolts, nuts, rivets and special parts. In cold forging, the dies are subjected to

higher stresses. Predicting forming loads and stresses is important for die design and machine

selection.

There are many researches and analysis on cold forming processes. Many cold forming

applications use numerical simulation to predict the forming design and the simulation

parameter settings. Altan and Knoerr [3] applied the 2D finite element method to investigate

suck-in type extrusion defects, bevel gear forging, stress analysis of forging tools and multi- stage cold forging designs. Oh et al. [4] discussed the features required to simulate cold

forging operations and provided example solutions to demonstrate the performance of the

DEFORM system. Joun et al. [5] proposed a numerical simulation technique for the forging

process with a spring-attached die. A penalty rigid-viscoplastic finite element method was

applied together with an iterative force-balancing method. They investigated significance of

metal flow lines for quality control and the effects of spring-attached dies on the metal flow

lines and the decrease in forming load. A three-stage cold forging process to form the spline

shape in the head of an aerospace fastener was proposed by MacCormack and Monaghan [6].

They gained insight into the operation by numerically analyzing the strain, damage, and flow

patterns for all three stages. Wu and Hsu [7] analyzed the effect of die shapes with different

draft angles and fillet radii on extrusion forging deformation using finite element method.

Two sets of dies with different shapes were performed and the results were compared with

the predictions of the finite element method for the same deformation mode. Cho et al. [8]

conducted a numerical study on the process design of cold forging operations for forward and

reverse extruded axisymmetric parts. The results of numerical simulation are in good

agreement with the experimental results. In order to analyze the formability of the multi- stage forging process, Park et al. [9] applied the finite element method to establish a

systematic process analysis method for the multi-stage forming of a constant velocity joint

outer race. Farhoumand and Ebrahimi [10] applied the FE code ABAQUS to the analysis of the

forward-backward-radial extrusion process to investigate the influence of geometric

parameters such as die corner radius and gap height and process conditions such as friction

on the process. The numerical results are compared with experimental data in terms of

forming loads and material flow in different regions. The hardness distribution of the

longitudinal section of the product was used to verify the strain distribution obtained from

the numerical analysis. Ji et al. [11] applied the numerical code of DEFORM_2D to study the

forming mechanism of a five-stage cold extrusion process for shaft parts used in gearboxes.

They showed that the five-stage cold extrusion process is feasible and obtained the forming

rules. Jafarzadeh et al. [12] applied the FE code of DEFORM-3D to study the transverse

extrusion process to analyze the effects of some important geometric parameters such as

initial billet dimensions, gap height and friction conditions on the required forging load,

material flow pattern and effective plastic strain distribution. They showed that the gap

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Yang, C.-C., Sumampow, Y., & Cruz, S. N. D. (2023). The Cold Forming Analysis of Eccentric Parts. European Journal of Applied Sciences, Vol - 11(3).

407-421.

URL: http://dx.doi.org/10.14738/aivp.113.14862.

height had the greatest influence on the forming load and material flow. This study analyzed

and compared 4 and 5 stages of fasteners. They used the FE code of DEFORM-3D to inspect

the effective stresses, strains and velocities of objects from billet material to finished material.

Yang and Lin [13] performed numerical and experimental studies on two forming modes for

two-step extrusion forming of AISI 1010 carbon steel. The numerical results for the effective

strain distributions are consistent with the hardness distribution measured in the experiment.

Kang and Ku [14] used spheroidized SCr420H billets to conduct a series of experimental study

on multi-stage cold forging for the outer race of a constant velocity joint with six inner ball

grooves. The results showed that with the proposed multi-stage cold forging process, the

outer race was well forged, and the dimensional accuracy of the forged outer race also met the

requirements. A new metal forming process was proposed by Winiarski and Gontarz [15] to

produce two-step outer flanges on hollow parts extruded by a movable sleeve. A two-stage

cold forging process was proposed by Ku [16] to manufacture AISI 1035 steel drive shafts

with internal spline and spur gear geometry. Al-Shammari et al. [17] designed a six-stage cold

forming process using a 3D geometric model to manufacture AISI 1010 steel shells of spark

plug. They applied numerical analysis to explore product part dimensions, forging loads,

effective stresses, contact pressures, and velocity fields. The actual product part dimensions

and forging loads of the six stages were compared with the FE simulation results to verify that

the analysis results were acceptable. Byun et al. [18] studied numerically on multi-stage cold

forging of SUS304 ball studs. They investigated the plastic deformation behavior of SUS304

from room temperature to 400°C and used a general method to express the flow stress as a

close-form function of strain, strain rate, and temperature. It is optimal at high strains,

especially during multi-stage cold forging. Winiarski et al. [19] performed a numerical study

on a six-stage cold forging process of 42CrMo4 steel hollow flanged parts using DEFORM

2D/3D to determine whether the proposed forging technique could be used to produce

flanged hollow parts. A multi-stage cold forging process using finite element analysis was

developed by Jo et al. [20] to manufacture a high-strength one-body input shaft with a long

body and no separate parts. They provided a proof-of-concept for the design and development

of a multi-stage cold forging process to manufacture a one-body input shaft with improved

mechanical properties and material recovery. Dubiel et al. [21] investigated the cold forging

process of flanged bolts to obtain consistent, acceptable and inconsistent grain flow patterns,

and correlated the FEM simulation results with the conducted experiments. Yang and Liu [22]

performed a numerical and experimental study on a five-stage cold forming process for

manufacturing relief valve regulating nuts with low carbon steel AISI 1010. The numerical

simulation and experimental results were in good agreement for the forming force growth

tendency. The effective strain distributions were consistent with the measured hardness

distributions. Highly compacted grain flow lines also led to higher hardness.

This study presents the analysis of multi-stage cold forming process for the manufacture of

eccentric parts. The forming process includes two-step forward extrusion, eccentric upsetting,

and backward extrusion over a moving punch. The numerical simulation of cold forming is

studied 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.