EXPERIMENTAL AND NUMERICAL ANALYSIS OF DEEP...

EXPERIMENTAL AND NUMERICAL ANALYSIS OF DEEP DRAWING PROCESS

MOHAMAD NAZRIN KOOY BIN MOHD DANIEL KOOY

Report submitted in partial fulfillment of the requirements

for the award of the degree of

Bachelor of Mechanical Engineering

Faculty of Mechanical Engineering

UNIVERSITI MALAYSIA PAHANG

DECEMBER 2010

ii

U�IVERSITI MALAYSIA PAHA�G

FACULTY OF MECHA�ICAL E�GI�EERI�G

We certify that the project entitled “Experimental and Numerical Analysis of Deep

Drawing Process” is written by Mohamad Nazrin Kooy bin Mohd Daniel Kooy. We

have examined the final copy of this project and in our opinion; it is fully adequate in

terms of scope and quality for the award of the degree of Bachelor of Engineering. We

herewith recommend that it be accepted in partial fulfillment of the requirements for the

degree of Bachelor of Mechanical Engineering.

(MUHAMMAD HATIFI BIN MANSOR)

Examiner Signature

iii

SUPERVISOR’S DECLARATIO�

I hereby declare that I have checked this project and in my opinion, this project is

adequate in terms of scope and quality for the award of the degree of Bachelor of

Mechanical Engineering.

Signature

Name of Supervisor : DR. AHMAD SYAHRIZAN BIN SULAIMAN

Position : LECTURER

Date : 6 DECEMBER 2010

iv

STUDE�T’S DECLARATIO�

I hereby declare that the work in this project is my own except for quotations and

summaries which have been duly acknowledged. The project has not been accepted for

any degree and is not concurrently submitted for award of other degree.

Signature

Name : MOHAMAD NAZRIN KOOY BIN MOHD DANIEL KOOY

ID Number : MA07101

Date : 6 DECEMBER 2010

vi

ACK�OWLEDGEME�TS

First and foremost I would like to express my sincere gratitude to my supervisor,

Dr. Ahmad Syahrizan bin Sulaiman for his invaluable guidance, ideas, constant

encouragement and continuous support in making this project possible. I am grateful for

his consistent support throughout the project with his patience and knowledge while

allowing me the room to work in my own. I would also like to thank him for the time

spent on proofreading and correcting the mistakes in the thesis.

My sincere thanks also go to the technical staffs of UMP Faculty of Mechanical

Engineering, who helped me in many ways especially in the operation of machines and

equipments. I would also like to express my special thanks to Mr. Zahari Anuar b.

Zakaria for his assistance in the fabrication of customized components for the deep

drawing die used in the present study, and also Mr. Mahdir b. Mohd Yusof for his help

in conducting the simulations after office hours. Certainly, not forgetting the UMP

Faculty of Mechanical Engineering for providing the support and equipment required in

the present study.

In addition, I would also like to acknowledge the kind support from SMP

System Sdn. Bhd. who helped fabricated the deep drawing die at a lowered price, which

greatly reduced the incurred expenses of the present study.

Last but not least, I would like to thank my loving parents for their continuous

support and guidance throughout my studies at Universiti Malaysia Pahang.

vii

ABSTRACT

One of the most common outcomes in deep drawing process is earing, or the formation

of uneven height at the top rim of a drawn part due to the material anisotropy. The

present study involves experimental and numerical studies of earing formation in deep

drawing process. The main objective of the present study is to determine the accuracy of

Hill’s 1948 and Barlat 1991 yield criteria in predicting earing using only uniaxial tensile

test data for FCC materials. The second objective is to investigate the effects of blank

diameter and blank holder force (BHF) on earing behavior. A deep drawing die for

cylindrical cup has been designed for the present study. For the experiments, two groups

of blanks made from aluminum alloy AA1100 and commercially pure copper were

drawn using two sets of BHF. The earing profiles were measured at every increment of

5 degrees from original sheet metal rolling direction, which were then symmetrized and

normalized for comparison. For the finite element analysis, the process is modeled as a

3 dimensional, quarter-model in MSC.PATRAN with MSC.MARC as nonlinear

implicit solver. Results showed that using only uniaxial tensile test data, Hill’s 1948

yield criterion was able to accurately predict earing behavior for aluminum. However,

Hill’s 1948 criterion did not accurately predict earing for copper due to simplifying

assumptions used in the FEA. The yield stresses and plastic flow curve should be

averaged for all orientations for materials with high angular yield stress difference such

as copper. Barlat 1991 criterion was observed to be unable to predict earing behavior for

both metals due to its dependency on yield stresses input only. It was also observed that

percentage earing increases with increasing blank diameter. BHF did not affect earing

behavior directly, but insufficient BHF were observed to cause wrinkling, resulted in

irregular height profiles. The results concluded that using only uniaxial tensile test data,

Hill’s 1948 criterion performed well in predicting earing profile for aluminum alloys,

which is significant to accurately predict earing behavior for aluminum alloys with yield

criterion approach using only uniaxial tensile test data in engineering applications.

viii

ABSTRAK

Salah satu hasil yang paling umum dalam proses penarikan dalam adalah earing, atau

pembentukan ketinggian tidak seragam pada bahagian atas produk yang ditarik yang

disebabkan oleh anisotropi bahan. Tesis ini membentangkan penyelidikan secara

eksperimen dan berangka terhadap pembentukan earing dalam proses penarikan dalam.

Objektif utama tesis ini adalah untuk menentukan ketepatan kriterium alah Hill 1948

dan Barlat 1991 untuk menjangka profil earing untuk logam FCC dengan hanya

menggunakan data daripada ujian tegangan ekapaksi. Objektif yang kedua adalah untuk

menyiasat kesan garis pusat contoh-kosong dan daya pemegang contoh-kosong terhadap

pembentukan earing. Satu acuan penarikan dalam telah direka untuk penyelidikan ini.

Untuk ekperimen, dua jenis contoh-kosong yang dibuat daripada aloi aluminium

AA1100 dan kuprum tulen komersial telah ditarik dengan dua set daya pegangan

contoh-kosong. Profile earing telah diukur pada sudut setiap 5 darjah dari arah

penggelekan asal kepingan logam tersebut, dimana ia kemudiannya disimetrikan dan

dinormalkan untuk perbandingan. Dalam analisis unsur terhingga, proses tersebut

dimodelkan sebagai model suku 3-dimensi dalam MSC.PATRAN dengan MSC.MARC

sebagai penyelesai tersirat tak linear. Keputusan menunjukkan bahawa dengan hanya

data daripada ujian tegangan ekapaksi, kriterium alah Hill 1948 dapat menjangka

pembentukan earing dengan tepat untuk aluminium. Walaubagaimanapun, kriterium

alah Hill 1948 tidak sesuai untuk menjangka earing untuk kuprum disebabkan oleh

andaian dipermudah yang digunakan dalam analisis. Bagi logam yang mempunyai

perbezaan tegasan alah antara sudut yang tinggi seperti kuprum, tegasan alah dan keluk

aliran plastik harus dipuratakan bagi semua orientasi. Kriterium alah Barlat 1991 juga

diperhatikan yang ia tidak dapat menjangka pembentukan earing untuk kedua-dua

aluminium dan kuprum kerana ia hanya menggunakan input tegasan alah sahaja.

Pemerhatian juga menunjukkan bahawa peratusan earing meningkat dengan

peningkatan garis pusat contoh-kosong. Daya pemegang contoh-kosong tidak memberi

kesan langsung terhadap pembentukan earing, tetapi daya yang tidak mencukupi akan

menyebabkan pengedutan yang akan mengakibatkan profil ketinggian yang rawak.

Keputusan yang didapati menyimpulkan bahawa dengan hanya data ujian tegangan

ekapaksi, kriterium alah Hill 1948 menunjukkan prestasi yang baik dalam menjangka

earing untuk aloi aluminium. Keputusan ini adalah penting dalam menjangka

pembentukan earing dalam aplikasi kejuruteraan dengan tepat untuk aloi aluminium

dengan kriterium alah dengan menggunakan hanya ujian tegangan ekapaksi.

ix

TABLE OF COTETS

Page

EXAMIERS’ APPROVAL DOCUMET ii

SUPERVISOR’S DECLARATIO iii

STUDET’S DECLARATIO iv

DEDICATIO v

ACKOWLEDGEMETS vi

ABSTRACT vii

ABSTRAK viii

TABLE OF COTETS ix

LIST OF TABLES xii

LIST OF FIGURES xiv

LIST OF SYMBOLS xviii

LIST OF ABBREVIATIOS xix

CHAPTER 1 ITRODUCTIO AD GEERAL IFORMATIO

1.1 Introduction 1

1.2 Problem Statement 2

1.3 Project Objectives 2

1.4 Scope of Project 3

1.5 Significance of Project 3

CHAPTER 2 LITERATURE REVIEW

2.1 Concept of Deep Drawing Process 4

2.2 Earing in Deep Drawing

2.2.1 Formation of Ears in Deep Drawing

2.2.2 Plastic Anisotropy of Materials

2.2.3 Prediction of Earing Profile in Deep Drawing

7

7

8

12

2.3 Limiting Drawing Ratio in Deep Drawing 14

2.4 Defects and Associated Variables in Deep Drawing

16

16

x

2.4.1 Wrinkles

2.4.2 Shell Fracture

19

2.5 Finite Element Analysis of Deep Drawing Process

2.5.1 Finite Element Modeling

2.5.2 Anisotropic Yield Criteria

22

22

25

CHAPTER 3 METHODOLOGY

3.1 Introduction 32

3.2 Design of Experiment 33

3.3 Designing Deep Drawing Die 36

3.4 Experimental Study of Deep Drawing Process

3.4.1 Blank Preparation

3.4.2 Experiment Procedure

3.4.3 Cup Height Averaging and Normalizing

39

39

39

40

3.5 Mechanical Properties 41

3.6 Finite Element Analysis of Deep Drawing Process

3.6.1 FE Modeling

3.6.2 Load Case, Boundary Conditions and Loads

3.6.3 Material Properties

3.6.4 Yield Criteria

45

45

46

47

48

CHAPTER 4 RESULTS AD AALYSIS

4.1 Experimental Results

4.1.1 Observations

4.1.2 Experimental Cup Earing Profile

50

50

53

4.2 Finite Element Analysis Results 58

4.3 Results Comparison and Analysis

4.3.1 Comparison between Experimental and FEA data

4.3.2 Results Comparison with Data from Previous Studies

61

61

66

4.4 Discussions

4.4.1 Summary of Comparison

4.4.2 Result Discrepancies

4.4.3 Limitations of Present Study

70

70

71

73

xi

CHAPTER 5 COCLUSIO

5.1 Conclusion 74

5.2 Recommendations 75

REFERECES 76

APPEDICES 80

A1 Recommended Punch and Die Radii for Given Blank Thickness 80

A2 Recommended Drawing Speeds for Single Action Draw 81

B1 Engineering Drawings of Deep Drawing Die 82

B2 Calculation Of Strain Ratios For Aluminum Alloy And Copper in

the Present Study

100

B3 Blank Holder Force Defined in Finite Element Analysis 102

C1 Calculation of Blank Holding Contact Area According to Blank

Diameter

103

xii

LIST OF TABLES

Table �o. Title Page

2.1 Average strain ratio for several common materials 11

2.2 Drawing parameters used in several studies in predicting LDR 14

2.3 LDR values for several materials obtained from previous

studies

15

2.4 Deep drawing parameters used in several previous studies 18

2.5 Comparison of BHF used in previous studies with

recommended BHF

18

2.6 Summary of experimental data required by various anisotropic

yield criteria

29

2.7 Advantages and limitations of various anisotropic yield

criteria

29

3.1 Material composition of AA1100 used in present study 34

3.2 Material composition of copper used in present study 34

3.3 Parameter setup for deep drawing process in the present study 36

3.4 Material properties required for FE analysis in the present

study

42

3.5 Parameters of tensile test in the present study 42

3.6 Strain ratio and yield stresses for materials used in present

study in respect to rolling direction.

43

3.7 Number of elements for mesh seeds for FE model according to

blank size

46

3.8 Boundary conditions applied on deformable blank 47

3.9 Parameters for Hill’s 1948 yield criterion in the present study 48

3.10 Parameters for Barlat 1991 yield criterion in the present study 49

xiii

4.1 Theoretical blank-holding pressure for materials used in

present study

52

4.2 Theoretical and utilized blank-holding force for deep drawing

experiment

53

xiv

LIST OF FIGURES

Figure �o. Title Page

2.1 A schematic illustration of deep drawing process: (a) Pure

Drawing; (b) Ironing

5

2.2 Constructional features of a typical deep drawing die 5

2.3 Schematic diagram of stresses operating upon cup deep

drawing and coordinate system utilized in the study.

6

2.4 Significant variables in a deep drawing operation 7

2.5 Earing in a deep drawn steel cup due to planar anisotropy of

sheet metal

8

2.6 (a) A (111)�11�0� slip system shown within an FCC unit cell.

(b) The (111) plane and three �11�0� slip directions indicated by arrows within that plane comprise possible slip systems.

9

2.7 Strains in tensile test specimen 9

2.8 Relation between width strain and thickness strain for different

R-values

10

2.9 Relation between width strain and thickness strain for different

R-values

13

2.10 Normalized earing profile for several aluminum alloys and

copper

13

2.11 Effect of average strain ratio on LDR for Deep Draw Quality

(DDQ) steel and Continuously-annealed Deep Draw Quality

(CA-DDQ) steel

15

2.12 Wrinkling of cups in deep drawing due to insufficient blank

holder force

17

2.13 Qualitative illustration of the BHF for successful part drawing 17

2.14 An example of shell fracture in deep drawing 19

2.15 Maximum drawing force obtained experimentally for stainless

steel and Al-killed steel

20

2.16 2D FE model of deep drawing process consisting of 1585

elements in SUPERFORM and DEFORM

22

xv

2.17 3-D FE model for (a) deep drawing and (b) redrawing process

in LS-DYNA3D

23

2.18 3-D FE model for square cup drawing process in LS-DYNA 24

2.19 3-D FE model for cylindrical cup drawing in LS-DYNA 24

2.20 Experimental and predicted cup height for Al-5%Mg (150µm

grain size, 80% cold reduction before annealing).

27

2.21 Illustration of Bezier interpolation (left) in Corus-Vegter yield

locus (right)

28

2.22 A comparison of yield locus obtained using several yield

criterions for IF-steel. (Yld2000 represents Barlat 2000

criterion)

30

3.1 Methodology flow chart for the present study 32

3.2 Basic deep drawing die dimensions for the present study 33

3.3 Coil springs used in the present study 35

3.4 Blank holder force profile in the present study 35

3.5 Temperature profile for annealing process in the present study 35

3.6 Experiment concept of the present study 36

3.7 Proposed design of deep drawing die for present study. (a)

Isometric view of die; (b) Cross-section A-A of the die

37

3.8 Simplified design of deep drawing die by SMP System Sdn.

Bhd. (a) Front cross-section of die; (b) Right view of the die

37

3.9 Hydraulic press used in the present study 38

3.10 Final design of deep drawing die used in the present study.

(a) Dimetric view die; (b) Cross B-B of the die

38

3.11 Deep drawing die setup using Spring B for BHF 39

3.12 Extensometer setup on tensile test specimen. (Left)

Longitudinal extensometer; (Right) Transverse extensometer

42

3.13 Some of the tensile test specimens after the test 43

xvi

3.14 Plastic flow curves obtained from tensile test for 0° orientation

from RD for (a) Aluminum, annealed 450℃, (b) Copper,

annealed 450℃

44

3.15 FE model for deep drawing process in the present study built

using MSC.PATRAN

45

3.16 Boundary conditions applied on deformable blank 46

4.1 Drawn cups for: (a) Aluminum and (b) Copper, annealed

450℃ using spring A (10N/mm) for blank holder force. From

left: Blank diameter 80, 85, 90 and 95mm

50

4.2 Drawn cups for: (a) Aluminum and (b) Copper, annealed

450℃ using spring B (16.3N/mm) for blank holder force.

From left: Blank diameter 80, 85, 90 and 95mm

51

4.3 Relation between blank holder contact area and blank diameter 52

4.4 Earing profile for deep draw experiment with BHF using

Spring A (10N/mm) for (a) Aluminum (annealed 450℃) and

(b) Copper (annealed 450℃)

53

4.5 Earing profile for deep draw experiment with BHF using

Spring B (16.3N/mm) for (a) Aluminum (annealed 450℃) and


54

4.6 Symmetrized earing profile for experiment with BHF using

Spring A (10N/mm) for (a) Aluminum (annealed 450℃) and


56

4.7 Symmetrized earing profile for experiment with BHF using

Spring B (16.3N/mm) for (a) Aluminum (annealed 450℃) and


57

4.8 Vector markers showing cup earing profile for 85mm annealed

aluminum blank for BHF using Spring A (10N/mm) using

Barlat 1991 criterion

58

4.9 Earing profile from FEA with BHF using Spring A (10N/mm)

for (a) Aluminum (annealed 450℃) and (b) Copper (annealed

450℃)

59

4.10 Earing profile from FEA with BHF using Spring B

(16.3N/mm) for (a) Aluminum (annealed 450℃) and (b)

Copper (annealed 450℃)

60

xvii

4.11 Comparison of experimental and FEA earing profile for

aluminum (annealed 450℃) with BHF using Spring A

(10N/mm) for blank diameter (a) 80mm, (b) 85mm and (c)

90mm

62


aluminum (annealed 450℃) with BHF using Spring B

(16.3N/mm) for blank diameter (a) 80mm, (b) 85mm and (c)

90mm

63


copper (annealed 450℃) with BHF using Spring A (10N/mm)

for blank diameter (a) 80mm, (b) 85mm and (c) 90mm

64


copper (annealed 450℃) with BHF using Spring B

(16.3N/mm) for blank diameter (a)80mm, (b)85mm and (c)

90mm

65

4.15 Comparison of normalized cup heights with previous studies

for annealed aluminum using Spring A (10N/mm) for blank

diameter (a) 80mm, (b) 85mm and (c) 90mm.

66


for annealed aluminum (annealed 450℃) using Spring B

(16.3N/mm) for blank diameter (a) 80mm, (b) 85mm, (c)

90mm and (d) 95mm

67


for annealed copper using Spring A (10N/mm) for blank

diameter (a) 80mm, (b) 85mm and (c) 90mm

68


for annealed copper using Spring B (16.3N/mm) for blank

diameter (a)80mm, (b)85mm and (c)90mm.

69

4.19 Relationship between percentage earing and blank diameter

for aluminum (annealed 450℃)

71

xviii

LIST OF SYMBOLS

� Blank diameter

� Punch diameter

� Drawing force

�� Blank holder force

ℎ Cup height

ℎ∗ Normalized cup height

� Strain hardening coefficient

Die corner radius

� Punch corner radius

� Strain ratio

∆� Planar anisotropy

�� Average strain ratio

� Blank thickness

� Yield strength

� Angle from rolling direction

� True strain

�� Strain in longitudinal direction in tensile test specimen

�� Strain in thickness direction in tensile test specimen

�� Strain in width direction in tensile test specimen

� Friction coefficient

� True stress, local stress

� Shear stress

xix

LIST OF ABBREVIATIO S

2-D Two dimensional

3-D Three dimensional

AA Aluminum Alloy

Al Aluminum

ann. Annealed

ASM American Society for Metals

B/Holder Blank holder

BA Batch annealed

BC Boundary condition

BHF Blank holder force

BHP Blank holder pressure

CA Continuously annealed

CQ Commercial quality

Cr Chromium

Cu Copper

DDQ Deep Draw Quality

EDD Extra Deep Drawing

Eq. Equation

FCC Face centered cubic

FE Finite element

FEA Finite element analysis

FEM Finite element method

HCP Hexagonal closed-packed

xx

Hill48 Hill’s 1948 anisotropic yield criterion

IF Interstitial-free

LDR Limiting drawing ratio

ND Normal direction

RD Rolling direction

SCC Stress corrosion cracking

SS Stainless steel

TD Transverse direction

UTS Ultimate tensile strength

Yld2000 Barlat 2000 anisotropic yield criterion




Zn Zinc

CHAPTER 1

I�TRODUCTIO� A�D GE�ERAL I�FORMATIO�

1.1 I�TRODUCTIO�

Deep drawing process is a sheet metal forming process where a punch is utilized

to force a flat sheet metal (blank) to flow into the gap between the punch and die

surfaces. As a result, the blank can be formed into the various shapes. A sheet metal

may be drawn into simple cylindrical-, conic- and boxed-shaped part and also

complicated parts which normally require redrawing processes using progressive dies.

Deep drawing is a popular selection due to its rapid press cycle times (Boljanovic,

2004). Its capability of producing complicated axissymmetric geometries and several

non-axissymmetric geometries in few operations with low technical labors requirement

is also an advantage in manufacturing applications. Examples of deep drawing

applications include containers of all shapes, sinks, beverage cans, automotive body and

structural parts and aircraft panels.

The important variables which affect the formability and outcomes of deep

drawing can be grouped into two categories: Material and friction factors; and tooling

and equipment factors. Proper selection of these variables is crucial in deep drawing to

maximize the formability of the sheet metal while reducing undesirable outcomes which

includes earing and defects such as wrinkling. In most cases, experimental studies are

conducted to determine the optimal variables for deep drawing operations as they

provide the most accurate results. However, such methods tend to be time consuming

and costly (Tzou et al., 2007). Hence, analytical approach such as finite element

analysis coupled with anisotropic yield criterion is often utilized as an alternative to

predict and analyze the variables and outcomes of deep drawing process. Many studies

2

have been conducted to improve the accuracy of yield criteria in predicting earing

behavior. While newer yield criteria may result in more accurate prediction, they tend to

require more material properties to be evaluated, which results in higher number of

required mechanical tests compared to earlier and simpler yield criteria. Thus, selection

of the appropriate yield criterion is important in predicting the earing behavior

accurately and practically.

1.2 PROBLEM STATEME�T

Earing is the formation of waviness at the top of a drawn cup caused by the non-

uniform strain-rate of the blank in different orientation due to anisotropic properties of

the material. It is one of the most common undesired outcomes in deep drawing as it

would require additional cutting operations to remove the ears, causing material

wastage, reduced production rate and increased production cost. Hence, finite element

analysis coupled with anisotropic yield criterion is commonly used to predict the earing

behavior of the material in deep drawing process. However, the accuracy of the yield

criterion in predicting the earing behavior is uncertain, depending on the blank material,

assumptions used and the mechanical tests available. Therefore, the accuracy of the

yield criterion in predicting earing behavior under a given limitations need to be

assessed before being applied in engineering applications.

1.3 PROJECT OBJECTIVES

(1) To design a deep drawing die for cylindrical cup drawing operation.

(2) To investigate the effects of blank diameter and blank holder force on earing in

deep drawing process.

(3) To determine a more accurate and suitable yield criterion to predict earing

behavior of FCC materials in deep drawing via finite element analysis using

only mechanical properties from uniaxial tensile test.

3

1.4 SCOPE OF PROJECT

(1) To conduct a deep drawing process with punch diameter of 50 millimeters with

punch and die corner radii of 6.36 millimeters.

(2) Blank material used will be limited to FCC materials: annealed aluminum and

annealed copper.

(3) Blank thickness of 1 millimeter is used in the present study as it is commercially

available.

(4) Blank diameter of 80, 85, 90 and 95 millimeters (corresponding to blank-to-

punch diameter ratio of 1.60, 1.70, 1.80 and 1.90 respectively) are used in the

present study as the LDR for most aluminum alloys and copper does not exceed

2.00.

(5) A finite element analysis using implicit non-linear code will be conducted to

predict the earing behavior of the deep drawn part based on the experimental

setup using quasi-static assumption (Strain rate is not time-dependant).

(6) Mechanical properties for FEA are obtained using only uniaxial tensile tests.

(7) Yield criterion used in finite element analysis will be limited to Hill’s 1948 and

Barlat 1991.

1.5 SIG�IFICA�CE OF PROJECT

In the present study, the earing behavior in deep drawing of FCC materials is

predicted using yield criterion approach in FEA using only material properties from

uniaxial tensile tests. As a result, the more accurate yield criterion to predict earing for

FCC materials using only data from uniaxial tensile test can be determined. In this case,

the comparison is between Hill’s 1948 criterion and Barlat 1991 criterion. The usage of

only uniaxial tensile tests for material properties in FEA allows the earing prediction for

deep drawing process to become relatively simple and cost effective. Since the usage of

aluminum alloys (FCC) in deep drawing applications is expanding, the results from the

present study could be applied to predict earing for a more complex deep drawn part

design. The investigation of the effect of blank diameter and blank holder force on

earing behavior in deep drawing also serves as one of the fundamentals in designing of

more complex deep drawn parts in industry.

CHAPTER 2

LITERATURE REVIEW

2.1 CO�CEPT OF DEEP DRAWI�G PROCESS

Sheet metal is a thin and flat piece of metal with thickness ranging between

0.15mm and 6.5mm (ASM, 1996). It is widely used in engineering to produce a large

variety of products which includes containers, beverage cans, household applications,

automotive parts, and aircraft panels. Sheet metal may be formed into desired geometry

using various processes which includes deep drawing, shallow drawing, bending,

blanking and stretch forming (Hosford and Caddell, 2007). The present study involves

the study of deep drawing process.

Deep drawing is a process to form sheet metals using deep drawing die. A punch

is used to force the sheet metal to flow into the gap between the punch and the die. As a

result, a cylindrical-, conical- or box-shaped part is formed in the die with minimal

material wastage (Boljanovic, 2004). One of the most common examples of deep

drawing is the cup-drawing operation. It is used to produce products such as cartridge

bases, zinc dry cells, metal cans and steel pressure vessels (Hosford and Caddell, 2007).

It is also used as a method for formability test of sheet metals such as the Swift cupping

test (Theis, 1999).

There are two types of process in deep drawing: Pure drawing and ironing. Pure

drawing is a deep drawing process without reduction of thickness of blank, whereas

ironing is a deep drawing process with blank thickness reduction (Boljanovic, 2004).

The layout of a typical deep drawing die is as shown in Figure 2.2 for pure drawing

process. However, some products cannot be drawn in a single draw and requires

5

secondary drawing operations (redrawing) which involve ironing process. As a result,

the design of the die will be more complicated as a progressive die is normally required

to allow multiple drawing operations under one production line.

Figure 2.1: A schematic illustration of deep drawing process: (a) Pure Drawing;

(b) Ironing.

Adapted from: Boljanovic, 2004

Figure 2.2: Constructional features of a typical deep drawing die.

Source: Szumera, 2003.

(a) (b)

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