A study of sheet metal stamping processes of lightweight partsplast.me.tut.ac.jp/sotsuken/tan07.pdf · Two-stage stamping of cold drawn magnesium alloy cup having small bottom corner

Two-stage stamping of cold drawn magnesium alloy cup having small bottom corner.

6.

Multi-stage stamping of tailor square blank for increase in wall thickness at bottom corner of square cup.

5.

Multi-stage stamping of high strength steel wheel disk having large inner corner thickness.4.

Two-stage stamping of tailor circular blank for increase in wall thickness of wheel disk.

3.

Multi-stage stamping of wheel disk having large inner corner thickness by means of conical punch.

2.Introduction.1.

ContentsChapter

A study of sheet metal stamping processes of lightweight parts

February 2008 Tan Chin Joo

Chapter 1 Introduction

FlatSmall thickness: low strengthLocal

thickening

Large thickness: high strength

Stamping

Tailor rolled blank

Long welding lines & high material lossTailor welded blank One-dimensional distribution

Control of thickness distribution of stamped products for reduction in weight

Proposed method for reduction in weightSmall thickness blank

Welding lines

Lightweight

Forming of lightweight material for reduction in weight of parts

• Density : 1/4 of mild steel• Specific strength : 2 times of mild steel

Advantages

• Low formability at room temperature• Formed at elevated temperature • Heating apparatus is expensive and

complicated

Disadvantages

Magnesium alloy


6.


5.


Two-stage stamping of tailor circular blank for increase in wall thickness at inner corner at inner corner of wheel disk.

3.


2.Introduction.1.

ContentsChapter


Chapter 2Multi-stage stamping of wheel disk having large inner corner thickness by means of conical punch

Steel Wheel

Welding

Roll forming

Bending, weldingMulti-stage stamping

Blanking

Disk forming Rim forming

Forming process of steel wheel

Relationship between weight of wheel and fuel consumption

Engine

Wheels

Drive shaft

• Reduction in weight of wheel• Less fuel consumption

Wheels directly driven by engine

Rim

Steel wheel

Local thickening at Strength Fatigue life

Inner corner

Blank thickness

Disk

Target portion of wheel disk for local thickeningHat portion

Drive shaft

Cracks in fatigue testRotating bending fatigue test

* K. Tanaka, K. Ishihara, H. Komatsu, Fatigue strength of car road wheels, SumitumoMetal, 39(4), p.325-336, 1987 (In Japanese).T. Yogo, Method for producing automobile wheel disk, Japan Patent JP2004074248, 2004 (in Japanese).

Forming of lightweight disk

*

(a) 1st stage

(d) 4th stage

(b) 2nd stage

(e) 5th stage(c) 3rd stage

Decrease in thickness

Flat punch Die

Flat punch Die

Drawn cup with flange

Outer punchOuter die

Inner punch

Inner punch

Outer punch

Die

Middle punchInner

punch

Inner die Outer

die

Outer punch

Inner die Equal

Conventional multi-stage stamping of wheel disk

Equivalent to inner corner

(c) 3rd stage(a) 1st stage (b) 2nd stage

Inner punch

Inner die

Outer die

Conical punch

Blank holder

Die

Conical punch

Die

Increase in wall thickness at inner corner by means of conical punches

φ58.6 R5 R7

φ64.6

φ48.4R5 R7

φ55.4

φ50.1R2 R3.8φ62.5

R3

~ 1/3.5 actual size of wheel disk

θθ

Increase in thickness

Large compression

Outer punch

Parameters for increase in thickness2. Drawn volume ratio1. Punch angle, θ

10 20 30

10

20

30

0Punch angle θ / °

Punc

h st

roke

in 2

nd st

age

/ mm

Drawn volume ratio, Vr0.470.44

0.410.38

Relationship between drawn volume ratio and punch stroke

Total volume, VT

Drawn volume,V

Vr=V/VT

After 2nd stage

Drawn volume ratio

Conical punch Die

(a) 1st stage

Deformation behaviors for θ =0º and Vr=0.44

(b) 2nd stage

(c) 3rd stage

Equivalent to inner corner Equivalent to

inner corner

-6.3%

3.7%

14.3%15.0%3.9%

8.5%2.6%

Inner corner

Deformation behaviors for θ =25º and Vr=0.44

(a) 1st stage (b) 2nd stage

(c) 3rd stage

Equivalent to inner corner Equivalent to

inner corner

-3.9%

9.2%

15%5.9%13.7%

-2%2.9%

Inner corner

Cross sections for θ =25º and Vr=0.44


(c) 3rd stage (d) 4th stage

(e) 5th stage~1/3 of 13 inch wheel disk

Thickness distributions of drawn cup having Vr = 0.41 for θ = 0º, 20º and 30º

(b) Experiment

Around inner corner

(a) Calculated

θ

Distance from center / mm

Cha

nge

in w

all t

hick

ness

/ %

Around inner corner

6%

0o

20o

30o

0 20 40 60-30

-20

-10

0

10

θ


Cha

nge

in w

all t

hick

ness

/ % Around inner

corner6%

0o

20o

30o

0 20 40 60-30

-20

-10

0

10

Change in wall thickness:(t - to)

tox 100%=

tHat portion

Hub hole Hub hole

Thickness distributions of drawn cup having Vr = 0.44 for θ = 0º, 20º and 30º

(a) Calculated (b) Experiment

6mm

Inner corner

Punch angle / o

After 2nd stage

After 3rd stage

Cha

nge

in w

all t

hick

ness

a

t inn

er c

orne

r / %

25

9.4%Maximum increase

0 10 20 30

-10

0

10

Cha

nge

in w

all t

hick

ness

at in

ner c

orne

r / %

10

0

10

100 20 30

After 2nd stage

After 3rd stage

Punch angle / oθ θ

Maximum increase9.0%

Average increase in wall thickness at inner corner for θ = 0º, 20º, 30º and different Vr

0 10 20 30-10

-5

0

5

10

15

Punch angleθ/ °

Ave

rage

incr

ease

in w

all

thic

knes

s at i

nner

cor

ner /

%

Vr=0.470.440.41

0.38

Stretching

Compression

10 20 30

5

10

15

20

25

0

50

100

150

200

250

0Punch angleθ/ °M

axim

um in

crea

se in

wal

l thi

ckne

ss

at in

ner c

orne

r / %

Max

imum

form

ing

load

in 3

rd st

age

/ kN

Forming load


Vr=0.47 Vr=0.44

Optimum condition

Optimum forming condition for increase in wall thickness at inner corner of wheel disk

Chapter 2Multi-stage stamping of wheel disk having large inner corner thickness by means of conical punch

• Average 10% increase in wall thickness around the inner corner of the wheel disk was successfully obtained by means of the conical punches.

• The optimum forming conditions θ =25º and Vr=0.44 were summarized.

• The blank thickness can be reduced without decreasing the strength of the wheel for the reduction in weight

Conclusions


6.


5.


Two-stage stamping of tailor circular blank for increase in wall thickness at inner corner of wheel disk.

3.


2.Introduction.1.

ContentsChapter


Chapter 3Stamping of tailor circular blank for increase in wall

thickness at inner corner of wheel disk

• High material loss.• Difficult to control laser welding process.• High cost.

Disadvantages

Thin blank

Thick blank

Welding

Laser welding of tailor circular blank

(a) 1st stage

(b) 2nd stage

(c) 3rd stage


Inner die

Punch Die

Inner punch


Blank holderPunch

Die

(b) 2nd stage

(a) 1st stage

2-stage stamping of tailor circular blank

3-stage forming of drawn cup with flange


Large inner corner thickness

Wheel disk

Punch Die

Punch Blank holder

Die

Stamping of tailor circular blank for increase in wall thickness at inner corner of wheel disk

Conditions for local thickening process

i) Stroke, s ii) Clearance between punch

and die, c

Parameters :

φ18φ54

R8 Blankc

Blank holder

PunchR4 R4

Die

DieRestricted by friction


c

Material was drawn into die cavity

PunchBlank holderφ68

s

(a) 1st stage

(b) 2nd stage

Low compression

High compression

Equivalent portion

Deforming behavior for local thickening process (s = 6.5mm, c=2mm)

(a) 1st stage

-3.1%

Deforming behavior for local thickening process (s = 6.5mm, c=2mm)

(b) 2nd stage

12%

Cha

nge

in w

all t

hick

ness

/ %

Distance from bottom center / mm

3.54.55.56.57.5

s / mm

Equivalentportion

0 20 40 60-30-20-10

0

102030

Calculated effect of stroke in 1st stage of local thickening process

Equivalent portion(c=2mm)

Distance from bottom center / mmCha

nge

in w

all t

hick

ness

/ %

s / mm

Equivalent portion

12

Flat

3.54.55.56.57.5

0 20 40 60-30

-20-10

010

2030

Effect of stroke in 2nd stage of local thickening process

(a) Calculated (b) Experimental

Equivalent portion


Cha

nge

in w

all t

hick

ness

%

3.54.55.56.57.5

s / mm

12

Equivalent portion

Flat

0 20 40 60-30-20

-100

10

2030

(c=2mm)

Effect of clearance in local thickening process

6.5Punch stroke in 1st stage s / mmM

ax. i

ncre

ase

in w

all t

hick

ness

in

targ

et p

ortio

n/ % c / mm

234

3 4 5 6 7 802468

101214

Tailor circular blank was formed with the conditions s = 6.5mm, c=2mm

Stroke in 1st stage s / mm

Max

imum

form

ing

load

in 2

nd st

age

/ kN

M

axim

um in

crea

se in

wal

l th

ickn

ess i

n ta

rget

por

tion

/ %

Load

Thickness

6.5

12

4 5 6 70

50

100

150

200

-30-20-100102030

Forming load in 2nd stage and increase in wall thickness at target portion

for different punch strokes in 1st stage(c=2mm)

15m

mφ58.6

13.5

mm

φ64.6

∼φ120

(a) 1st stage (b) 2nd stage (c) 3rd stage

φ36.82R3.8

R2.0 R19.4

φ50.1R8.0

Punch DieInner Punch

Outer punch

Outerdie

Inner die

Blank-holder φ48.4

φ55.4

Conditions for 3-stage forming of drawn cup with flange from tailor circular blank

1.6mmTailor circular blank

13.5

of actual disk∼

Punch Die

Deforming behavior for 3-stage forming of drawn cup with flange from tailor circular blank

1st stage

7.8%

(s=6.5mm, c=2mm)

5.9%


2nd stage

(s=6.5mm, c=2mm)

14%


3rd stage

(s=6.5mm, c=2mm)

11

3

Around innercorner


Cha

nge

i nw

allt

h ick

ness

%

tailorflat

0 20 40 60-30-20-10

01020

30

Wall thickness distribution of drawn cup with flange formed from tailor circular blank

Around inner cornerHub hole

Chapter 3Two-stage stamping of tailor circular blank for increase in wall thickness of wheel disk.

• Extra 8% increase in wall thickness at the inner corner of wheel disk was successfully obtained by the tailor circular blank.

• Extra 2 stages of the local thickening process were added to the conventional multi-stage stamping of wheel disk for the increase.

• The cross sectional shape of the drawn cup formed from the locally thick blank is almost the same with the one formed from the flat blank.

Conclusions


6.


5.



3.


2.Introduction.1.

ContentsChapter


(c) 3rd stage(a) 1st stage (b) 2nd stage

Inner punch

Outer punch

Inner die

Outer die

Conical punch

Die

Conical punch

Die

φ58.6 R5 R7

φ64.6

φ48.4R5 R7

φ55.4

φ50.1R2 R3.8φ62.5

R3

~ 1/3.5 actual size of wheel disk

25º25º



Large compression

25.2 25.2

(θ =25º and Vr=0.44)

Chapter 4Multi-stage stamping of high strength steel wheel disk having large inner corner thickness


Forming conditions：

Blank holder

1.41.6Blank thickness / mm

σ =943.7ε 0.18σ =629ε 0.15Flow stress / MPa

590 Mpa408 MPaTensile strength / MPa

High strength steel

Mild steelMaterial properties

Material properties

Thickness distributions of mild steel and high strength steel drawn cups

12.57.2

Mild

High strength

Around inner corner

Distance from center / mmCha

nge

in w

all t

hick

ness

/ %

1.61.4

Thickness / mm

0 20 40 60-40

-20

0

20

Inner corner

Less increase in thickness at inner corner!!!

Hub hole

Thickness distributions of drawn cups for different blank thicknesses

Blank thickness / mmMax

. inc

reas

e in

wal

l thi

ckne

ss

at i

nner

cor

ner /

%

Blank material=mild steel1.2 1.4 1.6 1.8 20

5

10

15

20

Inner corner

Decrease in blank thickness lead to small increase in thickness at inner corner

Conditions for 2-stage stamping of tailor circular blank for high strength steel wheel disk

φ18φ54

R8 Blank3

Blank holder

PunchR4 R4

Die

DieRestricted by friction


Material was drawn into die cavity

PunchBlank holderφ68

s

(a) 1st stage

(b) 2nd stage

Low compressionHigh compression

Equivalent portion

3

Punch stroke s is a parameter

1.4mm

-2%

Deformation behaviors of 2-stage stamping of tailor blank for s=8.5

(a) 1st stage

Plastic equivalent strain

0.8000.7330.6670.6000.5330.4670.4000.3330.2670.2000.1330.0670.000

13%


1.5701.0000.9090.8180.7270.6360.5450.4550.3640.2730.1820.9090.000


(b) 2nd stage

Punch stroke in 1st stage s / mm8.5

8.2A

vera

ge in

crea

ses i

n th

ickn

ess

at

equ

ival

ent p

ortio

n / %

Maximum

7 8 902468

101214

Influence of punch stroke in 1st stage on amount of local thickening

Equivalent portion

Forming of tailor blank using s=8.5mm

10%



1.9001.7401.5801.4201.2701.1100.9500.7920.6330.4750.3170.1580.000(a) 1st stage

Deformation behaviors of 2-stages stamping of tailor blank for s=8.5

1.0901.0000.9090.8180.7270.6360.5450.4550.3640.2730.1820.0910.000

5%


(b) 2nd stage

Deformation behaviors of 2-stages stamping of tailor blank for s=8.5

2.2602.0001.8201.6401.4501.2701.0900.9090.7270.5450.3640.1820.000

18%


(c) 3rd stage

7.214.5


Cha

nge

in w

all t

hick

ness

/ %

Around inner corner

Tailor

Flat

0 20 40 60-40

-20

0

20

Thickness distributions of drawn cups formed from tailor and flat blanks

Inner corner

Amount of thickening becomes double !!!

Hub hole

Tailor blank

(a) Disk formed from flat blank

φ94.1 21.9

mm

21.0

mm

φ94.1

(b) Disk formed from tailor blank

Wrinkle

Cross sections of miniature wheel disk formed from tailor and flat blanks

8mm

8mm

Chapter 4Multi-stage stamping of high strength steel wheel disk having large inner corner thickness

• The increase in wall thickness at the inner corner of the high strength steel wheel disk becomes small due to the decrease in blank thickness.

• The high strength steel wheel disk formed from the tailor circular blank has 2 times of degree of increase in thickness at the inner corner if compared to the one formed from the flat blank.

• The cross section of high strength steel wheel disk formed from tailor blank is almost the same with the one formed from flat blank.

Conclusions


6.


5.



3.


2.Introduction.1.

ContentsChapter


Local thickening method

Chapter 5Multi-stage stamping of tailor square blank for increase in wall thickness at bottom corner of square cup

Rotate 90 º for 2nd thickening operation

(a) After 1st stage (b) After 2nd stage1st thickened portion

Constraint

Compression

1st thickening operation

(c) Dimension of ditch in detail

Inner die

Punch46.034.032.0

48.0

0.15

0.15

Outer die

PunchHolder

Punch

Die

θ

R5.0R6.634.046.0

45.333.3 R5.0 R6.6θ

90.0

80.0

(b) 2nd stage

1st thickened portion 49.6

76.4

0.2Ditch

Stopper

1.6

(a) 1st stage

Inner die4.

6

Square blank

Conditions for thickening operation

θ=40º, 45º, 50º, 55º, 60ºParameter

symmetry along vertical axis

Deformation behavior for multi-stage stamping of tailor square blank for θ= 55 °

(a) 1st stage

14

model

(b) 2nd stage

20% increase in thickness


14

model

(c) 3rd stage


Ditch

14

model

Ditch

Ditch

Ditch

1st thickened portion33% increase in thickness


(d) 4th stage

14

model

X

YZ

Max. 33% increase in thickness

~1mm

~1mm

Bulging

75mm

75mm

Deformed tailor square blank obtained from simulation for θ= 55 °

14

model

(a) θ= 50 °

(b) θ= 55 °

(c) θ= 60 °

Buckling71.8

74.0

76.8

Cross sections of tailor square blank after 1st thickening operation for different θ

Thickness distributions of tailor square blank after 1st thickening operation for different θ

D istance from center / m m

Cha

nge

in w

all t

hick

ness

/ %

18θ / ο

Target portion

0 10 20 30 40

0

10

20

30

455055

Thickness distribution along 1st thickened portion of tailor square blank after 2nd

thickening operation

Distance along X=18 from Y=0

33

0 10 20 30 40

10

20

30

40 Cross between 1st and 2nd thickened portions

Less increase in thickness due to bulging

Portion equivalent to inner corner

Cha

nge

in w

all t

hick

ness

/ %

10% Increase in thickness

Deformation behavior for deep drawing of square cup from tailor square blank

XY

Z

R6

R636mm

Punch

Die

R6

75mm

36mm

R6

54mm 54mm

75mm

R6

R6

(a) Conditions (b) Deformation behavior

(a) Formed from tailor blank (b) Formed from flat blank

+10% -17%

Die

¼ of cup

Punch

Blank holder

Bottom corner

Cross sections of square cup formed from tailor blank and flat blank

High strength

Low strength

Thickness distribution of square cup formed from tailor square blank

Distance of bottom edge along X=18 / mm

Cha

nge

in w

all t

hick

ness

/ %

Cup formed from flat blank

Cup formed from tailor blank

Tailor blank

-17Bottom corner

10

0 10 20 30 40

-20

0

20

40


•The tailor square blank was successfully formed by stamping process.

•The tailor square blank having maximum 33% increase in wall thickness at the portion equivalent to the bottom corners of the square cup was formed.

• The square cup formed from the tailor blank have 10 % increase in wall thickness at bottom corners if compare to the one formed from flat blank having 17% decrease in wall thickness.

Conclusions


6.


5.



3.


2.Introduction.1.

ContentsChapter


Chapter 6Two-stage stamping of cold drawn magnesium alloy cup having small bottom corner

PunchBlank holder

Die

Coolant

Heater

Casing of laptop formed by hot stamping process

• Heating apparatus is expensive and complicatedDisadvantage

Conditions for two-stage stamping of cold drawn magnesium alloy cup having small bottom corner

(a) 1st stage

Die

Blank holder

Drawn cup

Outer punch

Container

Inner punch

Coil spring

（b）Rp=5mm

Crack

（a）Rp=1mm

Rp=5mmPunch

Drawn ratio =1.72 (b) 2nd stage

φ18.6φ20.0 R4

φ19.8φ18.8φ10.0

s

Small bottom corner

Deformation behavior for round magnesium cup having small bottom corner


Cross sections of round magnesium cup having small bottom corner

R1.1

7.2

φ18.9φ18.9

R5.0

9.4

（s=2.6mm）(a) 1st stage (b) 2nd stage

Height and bottom corner radius of round cup for different punch strokes in 2nd stage

0.5 1 1.5 2 2.5 3

2

4

6

8

10

0

1

2

3

4

5

6

0Punch stroke in 2nd stage / mm

Hei

ght o

f cup

/ m

m

Bot

tom

cor

ner r

adiu

s / m

m

Bottom corner radius

Height of cup

Crack at bottom corner

s=2.8mm

Limit for crack

Experimental

Calculated

2.8

（a） θ= 140°

(b)θ= 150°

Rｐ=5

R4φ20.0

φ18.6

Blank Holder

Ironing die

Conical punch

Blank

θ

Crack

φ19.69

Drawing die

Introducing conical punch and ironing die in 1st stage of cold stamping of round magnesium alloy cup

Maximum θ

to= 0.5

b

Ironing ratio, a= (to-b)/ to

R1.17.2

φ18.9

7.3Ｒ0.6

φ18.9

(a) By flat punch for s=2.6mm

(b) By conical punch for s=2.9mm

(c) By conical punch for s=3.4mm and a=20%

Straight

7.8

Ｒ0.5

φ18.7

Cross sections of round magnesium cup obtained from experiment

Conditions for two-stage stamping of magnesium square cup having small bottom corner radius

R3.4

R4

R4R4

18.8

18.8

20.0

20.0

(a) 1st stage(b) 2nd stage

Square cup

Outer punch

φ10φ18.8

φ19.8

Container

Inner punch

27

R8.1Square blank

Small bottom corner

R3.75.2 R0.63.8

Magnesium square cups obtained from experiment


Chapter 6Two-stage stamping of cold drawn magnesium alloy cup having small bottom corner

• The round and the square magnesium alloy cups having small bottom corners were successfully formed at room temperature.

• An extra stage is added for reducing the bottom corner radius.

• The employment of the conical punch and the ironing die improved the dimensions of the cup

Conclusions

List of publicationsReviewed journals:1. Chin Joo Tan, Yohei Abe, Ken-ichiro Mori, Takayuki Nonaka and Osamu Ebihara,

Increase of wall thickness around corner of multi-stage drawn cup with flange using conical punches, Key Engineering Materials, vol. 340-341, p. 761-766, 2007.

2. 安部洋平, Chin Joo Tan, 森謙一郎,藤岡武洋,野中孝之,海老原治,,円錐パンチを用いたフランジ付き多段絞り容器角部の増肉成形., Journal of Japan Society for Technology of Plasticity, vol. 48, no. 561, p. 55-59, 2007.

3. C. J. Tan, K. Mori and Y.Abe, Multi-stage stamping of high strength steel wheel disk, Journal of advanced manufacturing technology (Spec. ed.), vol. 1, no. 1, p.31-47, 2007. (ISSN:1985-3157).

4. C. J. Tan, K. Mori and Y.Abe, Forming of tailor blanks having local thickening for control of wall thickness of stamped products, Journal of Material Processing Technology, in press. 2007.

Reviewed Conference papers:5. C. J. Tan, K. Mori and Y.Abe, Increase in wall thickness at inner corner of multi-stage

stamping of wheel disk by locally thick blank, Proc. 2nd International Conference on New Forming Technology (ed. F. Vollertsen et al.), p.371-380, 2007.

6. C. J. Tan, K. Mori and Y.Abe, Forming of high strength steel wheel disk having large inner corner thickness. Proc. International Conference on Engineering & ICT, vol. 1, p.41-48, 2007. (Best paper award).

(b) 1st stage(a) Blank

(c) 2nd stage (d) 3rd stage

Drawn cup for θ =25º and Vr=0.44

12mm

Max

. inc

reas

e in

wal

l thi

ckne

ss

in

targ

et p

ortio

n / %

Angle of bulging ring / o θ43

c / mm234

0 10 20 30 40 50 60

2468

101214

Effect of angle of bulging ring in local thickening process

θ

Reason for decrease in thickness for s = 7.5mm

(i) s= 7.5mm (ii) s = 6.5mm

53º 43ºDie

Outer punch

DieOuter punchInner punch

Equivalent portion


Inner punch

High compression

Low compressionHigh

compressionLow compression


(c=2mm)

Photographs of deformed discs


10mm

2-stages local thickening process (s=6.5mm, c=2mm)

10mm

Drawn cup with flange(ii) Formed from

flat blank(i) Formed from

locally thick blank

Thickness distributions of drawn cups for different materials

Around inner corner

Mild

Highstrength


Cha

nge

in w

all t

hick

ness

/ %

Blank thickness = 1.4mm

0 20 40 60-40

-20

0

20

Inner corner

High strength steel has no influence on the increase in thickness

Forming of high strength steel drawn cup from tailor circular blank


Inner die

Inner punch


Blank holderPunch

Die

(b) 2nd stage

(a) 1st stage

2-stage stamping of tailor circular blank 3-stage forming of

drawn cup with flange

Increase in thicknessLarge inner corner thickness

High strength steel wheel disk

Punch Blank holder

Die

(a) 1st stage

Conical punch Die

Holder

Die

(b) 2nd stage

(c) 3rd stage


Die

PunchBlank holder

Forming load in 2nd stage for s = 8.5mm

2 4 6 8 10

50

100

150

200

0Punch stroke s / mm

Form

ing

load

/ kN

2nd

1st

(a) Formed from flat blank

10mm

10mm(b) Formed from tailor blank

Miniature wheel disks formed from tailor and flat blanks

Deformation behaviors of thickening operation for θ=55º

(b) 2nd stage(a) 1st stage

18% Target portion


80

40

6 6

40

(a) 1st thickening operation (b) 2nd thickening operation

90°rotation

6 6

1st thickened portion

2nd thickened portion

Equivalent to bottom corners of square cup

Double thickening

80

40

Equivalent to bottom edges of square cup

Distribution of thickness and hardness of round cup in two-stage stamping process

Thic

knes

s / m

m

2 4 6 8 10 12 14 16

0.2

0.4

0.6

0.8

1

0

20

40

60

80

100

0Distance from bottom center / mm

Har

dnes

s / H

vHardness

Thickness

1st stage2nd stage

Initial thickness

Around bottom corner

Deformation behaviors of cup for θ= 150°

(a) 1st stage

0.5490.5060.4630.4200.3770.3340.2910.2480.2050.1620.1190.0760.033


Deformation behaviors of round magnesium cup for θ= 150°

(b) 2nd stage

0.9500.8790.8080.7370.6660.5960.5250.4540.3830.3120.2410.1710.010


Relationship between height of cup and bottom corner radius for different punch strokes in 2nd

stage for a=20% & θ= 150°

1 2 3 4

2

4

6

8

0

0.5

1

1.5

2

0Punch stroke in 2nd stage s / mm

Hei

ght o

f cup

/ mm

Bot

tom

cor

ner r

adiu

s / m

mHeight

RadiusLimit for

crack

Crack

Distribution of thickness strain and hardness of cup after 1st and 2nd stage for a=20% & θ= 150°

0 2 4 6 8 10 12 14 16 18-0.3-0.2

-0.1

0

0.1

0.2

0.3

0

20

40

60

80

100


Thic

knes

s stra

in

Har

dnes

s / H

V

HardnessStrain

1st2nd

Bottom corner after 2nd stage

Distribution of thickness strain and of hardness along cross section of square cup

0 2 4 6 8 10 12 14-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0

20

40

60

80

100


Thic

knes

s stra

in

Har

dnes

s / H

v

Thickness strain

Hardness

1st2nd

Around bottom corner

10 20 30

50

100

150

200

250

0Punch angleθ/ °

Form

ing

load

in 3

rd st

age

/ kN

Vr=0.47

0.44

0.41

0.38

Relationship between forming load in 3rd stage and conical punch angle

Documents

A study of sheet metal stamping processes of lightweight partsplast.me.tut.ac.jp/sotsuken/tan07.pdf · Two-stage stamping of cold drawn magnesium alloy cup having small bottom corner