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
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 at inner corner at inner corner 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
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
(a) 1st stage (b) 2nd stage
(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
Distance from center / mm
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
Increase in thickness
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
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 at inner corner 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
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
Outer punchOuter die
Inner die
Punch Die
Inner punch
Drawn cup with flange
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 thickness
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
Increase in thickness
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
Distance from bottom center / mm
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%
Deforming behavior for 3-stage forming of drawn cup with flange from tailor circular blank
2nd stage
(s=6.5mm, c=2mm)
14%
Deforming behavior for 3-stage forming of drawn cup with flange from tailor circular blank
3rd stage
(s=6.5mm, c=2mm)
11
3
Around innercorner
Distance from bottom center / mm
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
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 at inner corner 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
(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
Increase in thickness
Equivalent to inner corner
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
Drawn cup with flange
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
Increase in thickness
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%
Deformation behaviors of 2-stage stamping of tailor blank for s=8.5
1.5701.0000.9090.8180.7270.6360.5450.4550.3640.2730.1820.9090.000
Plastic equivalent strain
(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%
Deformation behaviors of 3-stage stamping of tailor blank for s=8.5
Plastic equivalent strain
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%
Plastic equivalent strain
(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%
Plastic equivalent strain
(c) 3rd stage
7.214.5
Distance from center / mm
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
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 at inner corner 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
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
Deformation behavior for multi-stage stamping of tailor square blank for θ= 55 °
14
model
(c) 3rd stage
Deformation behavior for multi-stage stamping of tailor square blank for θ= 55 °
Ditch
14
model
Ditch
Ditch
Ditch
1st thickened portion33% increase in thickness
Deformation behavior for multi-stage stamping of tailor square blank for θ= 55 °
(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
Chapter 5Multi-stage stamping of tailor square blank for increase in wall thickness at bottom corner of square cup
•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
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 at inner corner 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
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
(a) 1st stage (b) 2nd stage
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
(a) 1st stage (b) 2nd stage
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
Increase in thickness
Inner punch
High compression
Low compressionHigh
compressionLow compression
Increase in thickness
(c=2mm)
Photographs of deformed discs
(a) 1st stage (b) 2nd stage
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
Distance from center / mm
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
Outer punchOuter die
Inner die
Inner punch
Drawn cup with flange
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
Equivalent to inner corner
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
Chapter 5Multi-stage stamping of tailor square blank for increase in wall thickness at bottom corner of square cup
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
Plastic equivalent strain
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
Plastic equivalent strain
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
Distance from bottom center / mm
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
Distance from bottom center / mm
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