Center for Precision Forming
(www.cpforming.org
Taylan Altan, Director
(e-mail: altan.1@osu.edu)
A short Review
March 2014
1
INTRODUCTION
• The Ohio State University (OSU) has established the Industry/University
Cooperative Research Center (I/UCRC) on Precision Forming (CPF) focusing
on research needs of metal forming industry
•
Funding is provided
member companies.
by
National
Science
Foundation
(NSF)
and
• CPF (www.cpforming.org) benefits from research conducted at the
Engineering Research Center for Net Shape Manufacturing (ERC/NSM –
www.ercnsm.org)
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OBJECTIVES
• Improve existing metal forming processes/products and develop new
innovative processes, tooling and equipment
•
Conduct projects in close collaboration with industry and transfer the results
to the member companies
•
Train and educate engineers in the fundamentals and practice of metal
forming science and technology
3
CPF is supported by NSF and member companies,
interested in metal forming
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CURRENT PROJECTS
Project CPF-1.1 – Warm Forming of Al Alloys
Project CPF-1.4 – Forming of AHSS in a Servo Press – Die Design
Project CPF-2.1 – Material Properties and Formability
Project CPF-2.2 – Forming Al in a Servo Press
Project CPF 3.3 – Friction/Lubrication/Wear
Project CPF-5.1 – Bending and Springback in Forming of AHSS and Copper Alloys
Project CPF-5.2 – Blanking / Piercing
Project CPF-5.2 A – Hole Flanging and Edge Cracking
Project CPF-5.5 - Hot Stamping
Project CPF 5.6 Practical Method for Predicting Fracture Using FE Simulation
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CPF-1.1 - Warm Forming of Al, Mg, Ti & SS
in an Aida Servo Drive Press
Insulation plate
Die ring
Heaters
Sheet
Punch
Blank holder
Water inlet
Cushion pins
AZ31B-O
AA5754-O
T(°C)
RT
250
300
LDR
2.1 Velocity : 2.5-50mm/sec
2.5
2.9 Cup diameter: 40 mm
T(°C)
RT
275
275
LDR
2.6
3.2
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CPF-1.4 - Forming of AHSS in a Servopress
Forming of AHSS in Servo Press
980 MPa
(145 ksi)
590 MPa
(85 ksi)
440 MPa
(65 ksi)
270 MPa
(40 ksi)
Can we use servo drive properties to improve
formability and reduce springback in forming
AHSS?
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CPF-1.4 - Forming of AHSS
Forming of AHSS in Servo Press
Punch
Blank holder
Materials of interest:
DP 600
DP 980
And others
Die
Bottom die set
Die design (manufactured by Shiloh) for testing AHSS.
Top die set
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CPF-1.4 - Forming of AHSS in a Servopress
Forming of AHSS in Servo Press
1)
2)
3)
4)
5)
6)
Straight Bending
Shrink Flanging
Stretch Flanging
U-Bending
Curved U-Bending
Deep Drawing
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CPF-1.4 – Forming of AHSS in a Servopress
CPF/Shiloh die set (for 300 ton servo-press)
DIE
R1
R4
R3
R5
R6
R2
Parameter
Notation
Value
Concave side radius
R1
601.6 mm
Convex side radius
R2
598.4 mm
R3
51.6 mm
R4
56.6 mm
R5
61.6 mm
R6
66.6 mm
Cavity corner radii
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CPF-1.4 – Forming of AHSS in a Servopress
Example: Shrink and Stretch Flanging
BLANK
DIE
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CPF-1.4 - Forming of AHSS in a Servopress
Forming of AHSS in Servo Press
Thinning (%)
9.0
5.8
2.7
-0.4
-3.5
-6.6
-9.7
-12.8
Min =
Max =
Max. Thinning ~ 9%
-12.8
9.0
Deep drawn sample
DP 600, t0 = 0.83 mm
Draw depth = 50 mm
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CPF-2.1 Material Characterization
Viscous Pressure Bulge (VPB) Test
Laser Sensor
Downward
motion
clamps the
sheet
Continued
downward
motion forms
the bulged
sheet
Test Sample
Viscous Medium
Pressure
Transducer
Stationary Punch
Before Forming
After Forming
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CPF-2.1 Material Characterization – Flow
Stress
Viscous Pressure Bulge (VPB) Test
True Stress (MPa)
1000
Uniform Strain
from Tensile
Test = 0.16
800
True Stress (ksi)
145
Tensile data with Power Law
(σ=Kεn)
116
600
Useful strain 87
from Bulge
Test = 0.49
400
58
200
Material, DP600, 1 mm
0
0
0.1
0.2
0.3
True Strain
VP Bulge Test
29
Tensile Test
0.4
0.5
14
CPF-2.1 - Material Characterization – VPB Test
Test sample
Before bursting
After bursting
15
CPF-2.1 - Material Characterization – VPB Test
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CPF-2.1 - Determination of Sheet Formability
Using VPB Test
Graph shows dome height comparison for SS 304 sheet material from eight
different batches/coils [10 samples per batch].
Dome height before burst (in)
(mm)
1.6
40
(in)
1.6
Maximum bulge height before fracture
1.4
1.2
30
1.2
1
20
0.8
0.8
0.6
10
0.4
0.4
0.2
0
A
B
C
D
E
F
G
H
Coil/Heat/Supplier
Batch / Coil
/ Heat / Supplier ID
Highest formability  G , Most consistent  F
Lower formability and inconsistent  H
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CPF-2.1 - Materials Tested with VPB Test at CPF
(data available to CPF members)
St 14
St 1403
AISI 1018
AKDQ
1050
DR 120
DDS
BH 210
HSS
DP500
DP 590
DP 600
Steels
DP 780-CR
DP 780-HY
Bare DP 980 Y-type X
Bare DP 780 T-Si type
GA DP 780 T- AI Type
GA DP 780 Y-type U
GA DP 780 Y-type V
DQS-270F GA-Phosphate coated
DQS-270D GA-Phosphate coated
DP 780
TRIP 780
DP 980
Aluminum and Magnesium Alloys
AA 6111
AA 5754-O
X626 -T4P
AZ31B
AZ31B-O
Stainless Steels
SS 201
SS 301
SS 304
SS 409
SS 410 (AMS 5504)
SS 444
LDX 2101
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CPF-2.1 - Material Characterization – Dome Test
Dome Test (Frictionless)
When the
blank is well
lubricated, it
fails at the
center of the
dome.
Necking /
fracture moves
with increased
friction.
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CPF-2.1 - Formability
Stretch Bending
DP780
Underbody structural part
Challenge:
This type of fracture cannot be predicted using
conventional Forming Limit Curve (FLC).
DP980
B-pillar inner
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Ref: Shi and Chen 2007
CPF-2.2 - Forming of Al Alloys in a Servo Drive
Press (AIDA)
Die set built by Honda
Thinning (%)
28.4
20.5
12.7
4.9
-2.9
-10.7
-18.5
-26.3
Min =
Max =
-26.3
28.4
Material draw-in
Maximum thinning ~28%
Draw depth = 155 mm
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CPF-3.3 - Friction/Lubrication – Cup Draw Test
Evaluation of Lubricants
Performance
evaluation
criteria
(cups drawn to same depth):
i. Higher the Blank Holder Force (BHF)
that can be applied without fracture in the
drawn cup, better the lubrication condition
ii. Smaller the flange perimeter, better
the lubrication condition (lower coefficient
of friction)
22
CPF-3.3 - Friction – Cup Draw Test
Cup Draw Test
Lubrication performance:
Shorter Perimeter
Higher BHF before fracture
23
CPF-3.3 - Friction / Tribology
Temperatures in Cup Draw Test – DP 600
Contact area
with die
Challenges:
1) Higher contact pressure and higher temperature are detrimental for lubricants,
2) Temperature and pressure additives are needed
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Ref: Kim et al 2009
CPF-3.3 - Friction / Lubrication
Evaluation of Lubricants for Forming
Al 5182-0 (1.5 mm)
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CPF-3.3 - Forming of AHSS / Die Wear
Die Wear in Forming of AHSS
Die Insert
Press
Motion
Die Insert
r = 5 mm
t0 = 0.77 mm
Punch
(Stationary)
Press
Motion
r = 5 mm
r = 20 mm
Dp = 152.4 mm
Ironing
t ≈ 0.70 mm
Currently with DP590
In future, Stainless Steel
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CPF-5.1 – Bending and springback in Forming AHSS and Copper Alloys
Schematic of 3 point bending tooling at OSU
27
CPF-5.2 - Blanking/Piercing of AHSS
Blanking / Piercing
Schematic of piercing
Blanked edge
(obtained from FE simulations)
Roll over zone (Zr)
Shear zone (Zr)
Fracture zone (Zf)
Burr zone (Zb)
vp = punch velocity
fb = blank holder force
dp = punch diameter
dd = die diameter
rp = punch corner radius
rd = die corner radius
db = blank holder diameter
t = sheet thickness
Punch-die clearance (% of sheet thickness) = (dd-dp)/2t*100
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CPF-5.2 - Blanking/Piercing of AHSS
Reduction of strains at blanked surface
3
2.5
Single shear
Conical with flat tip
Effective strain
2
1.5
Flat
Humped
Conical
1
0.5
Conical with
spherical tip
Humped
0
0.6
1
1.5
2
2.5
3
3.5
3.6
Distance from the top surface of the sheet (mm)
29
CPF-5.2A – Hole Flanging/Edge Cracking
Hole Expansion Test
Schematic of hole expansion test
Before and After Hole Expansion
(conical punch)
dd
DIE
rd
dh
θ
dp
Blank Holder
fb
Punch
db
vp
vp=punch velocity
fb=blankholder force
θ=punch angle (conical)
dd=diameter of the die
db=diameter of blankholder rd=die radius
dh=diameter of pierced hole in the blank
dp=punch diameter (hemispherical)
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CPF-5.5 - Hot Stamping
Easier to Form
22MnB5
At ~950°C
(1750ºF)
Austenite
3-5 min.s
in Furnace
Less force and
springback
Mn-B alloyed steel
(As delivered)
Ferrite-Pearlite
Quenched in the die
>27°C/s (~49°F/s)
Quenched
Martensite
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Ref: Grote 2009, Gutermuth 2011.
CPF-5.5 - Hot Stamping
FE Simulation of parts with uniform properties
Colors other than gray:
Thinning >20%.
Part stamped at the participating
company
32
CPF-5.5 - Hot Stamping
FE Simulation of cooling channel analysis
Nodal temperature - Membrane
230
200
171
142
112
83
54
25
1.3 mm roof rail die,
After 10 stampings.
33
CPF-5.5 - Hot Stamping
FE Simulation of cooling channel analysis
After 10 stampings.
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CPF-5.5 - Hot Stamping
FE Simulation of parts with tailored properties
Soft zone:
310 – 330 HV
920 – 1020 MPa
(~135 – 150 ksi)
Literature:
[George 2011] , 400°C dies = 790-840 MPa
[Feuser 2011], 450°C dies = ~850 MPa
Hardened zone:
485 – 515 HV
1500 – 1590 MPa
(~220 – 230 ksi)
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Prediction of fracture/necking from strain or
thickness variations (tensile data from Jim
Dykeman-Honda HRA)
1400
0.6
1200
0.5
Major Strain (mm/mm)
Stress (MPa)
CPF–5.6 - New Project: Prediction of Fracture
1000
800
600
400
0.3
0.2
0.1
200
0
0.4
0
0
0.02
0.04
0.06
0.08
Strain (mm/mm)
0.1
0.12
0.14
0
50
100
Time (s)
150
200
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Questions / Comments?
For more information , please contact:
Dr. Taylan Altan (altan.1@osu.edu), Ph-614-292-5063
Center for Precision Forming –CPF (www.cpforming.org)
339 Baker Systems,1971 Neil Ave,
Columbus, OH-43210
Non-proprietary information can be found at web sites:
www.cpforming.org
www.ercnsm.org
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