Post on 06-Jul-2018
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
1/28
w w w . a u t o s t e e l . o r g
AN INNOVATIVE SHEARING PROCESS FOR AHSS EDGE STRETCHABILITY
IMPROVEMENTS
Mike Shih
United States Steel Corporation
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
2/28
w w w . a u t o s t e e l . o r g
AHSS Edge Fracture
• AHSS Edge Fracture
• Conventional FLD fail to predict
Cause: – Material Property
– Die Condition
– Poor Sheared Edge Condition
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
3/28
w w w . a u t o s t e e l . o r g
Introduction Optimized Bevel Shear Hole Piercing
Hole Expansion Test
Evaluation of the Sheared Edge
Developmental Straight Edge Shearing
Adjustable Shearing Device
Sheared Edge Tension Test
Sheared Edge Dome Test
Sheared Edge Limit Strain
Conclusions
Outline
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
4/28
w w w . a u t o s t e e l . o r g
Shearing Processes
Hole Punching ( Hole piercing die)
Die
Clearance
Punch
Blank Holder
Sheet Metal
Blank Holder
Clearance
Punch
Bevel Shear
θ
Straight Edge Shearing ( Blanking die , Trimming die )
Shear Rake angle Q3
Front ViewUpper Blade
Clearance
Sheet Metal
Blade Rake Angle Q2
Back Cut Angle
(clearance angle)
Blank Holder
Q1Lower Blade
Introduction
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
5/28
w w w . a u t o s t e e l . o r g
Blank Holder
Clearance
Punch
θ
6 degrees
Specimen holding fixture
Die spring
Die
Punch
Pd
Dd
Punch
Die
Sheet Steel
Holder
Optimized Bevel Shear Hole Piercing
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
6/28
w w w . a u t o s t e e l . o r g
Punch Load vs. Die Clearance(DP980 1.2 mm, Longitudinal and Transverse)
0
1000
2000
3000
4000
5000
6000
7000
8% 13% 17% 21%
Die Clearance
P e a k
L o a d (
L b f )
03-L
3-T
6-L
6-T
9-L9-T
Over 50 load drop
Shear Load
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
7/28w w w . a u t o s t e e l . o r g
DP780 1mm
0%
10%
20%
30%
40%
50%
60%
10% 15% 20%
Die Clearance
H o l e E x p a n s i
o n
R a t i o
flat 3-L 3-T 6-L6-T 9-L 9-T
Hole Expansion Test
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
8/28w w w . a u t o s t e e l . o r g
Hole Expansion Test - DP980
0%
10%
20%
30%
40%
50%
5% 7% 9% 11% 13% 15% 17% 19%
Die Clearance (%)
H o l e E x p a n s i o n R a t i o
DP980 1.2 mm
DP980 2 mm
Best Shearing Condition
6 degrees Bevel Shear
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
9/28w w w . a u t o s t e e l . o r g
Optimized Shearing Condition- 6 Degrees, 15% DC, Longitudinal Shearing
0.0%
20.0%
40.0%
60.0%
80.0%
100.0%
120.0%
1Test Material
H o l e E x p a n s i o n
R a t i o
50XK-F
50XK-6L
Dp600-2mm-F
DP600-2mm-6L
Dp780-1mm-F
DP780-1mm-6L
TRIP780-1.6mm-F
TRIP780-1.6mm-6L
Dp980-2mm-F
Dp980-2mm-6L
F
F
F F F
50XK 1.4mm
DP780 (1mm)
Trip780 (1.6mm)
DP980 2mm
Optimized Shearing Condition
DP600 2mm40%
23%62%
25% 39%
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
10/28w w w . a u t o s t e e l . o r g
Concept Punch
6 degrees 6 degrees 6 degrees 9 degrees
Optimized : 6L Concept 1 : 6-6 Concept 2 : 6C Concept 2 : 9C
0.0%
20.0%
40.0%
60.0%
80.0%
100.0%
120.0%
140.0%
50XK-
F
50XK-
6L
50XK-
6C
50XK-
9C
600-
1-F
600-
1-6L
600-
1-6C
600-
1-9C
600-
1-66
600-
1.6-F
600-
1.6-
6L
600-
1.6-
6C
600-
1.6-
9C
600-
2-F
600-
2-6L
600-
2-6C
600-
2-66
Punch Condition
H o l e
E x p a n s i o n R a t i o
50XK
DP600 1mm DP600 1.6 mm DP600 2 mm
6-6
F
F FF
6L
6L6L 6L
6-6
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
11/28w w w . a u t o s t e e l . o r g
Evaluation of the Sheared Edge
(1) (2)
Burnish
Rollover
Optimized Bevel Shear - 15%
Fracture
(1) (2)
Rollover
Flat Head Punch - 15%
Burnish
Fracture
(1)(2)
Initial Contact
Point
Final Contact
Point
Section cut
Rolling
1/2 Burnish
200
220
240
260
280
300
320
340
360
0 100 200 300 400 500 600 700 800
Distance from SF[microns]
H V
Typical Optimized Conventional
Optimized
1/2 Fracture
200
220
240
260
280
300
320
340
360
380
0 100 200 300 400 500 600 700 800
Distance from SF[microns]
H V
Typical Optimized Conventional
Optimized
Microhardness profile of test DP780 , Chiriac, C. et al. 2011, MS&T 2011
Bevel
Shear
Rollover
(%)
Burnish
(%)
Fracture
(%)
HER
(%)
Side 1 12 21 68 53
Side 2 13 13 74
Flat
Head
Rollover
(%)
Burnish
(%)
Fracture
(%)
HER
(%)
Side 1 16 21 63 32
Side 2 16 21 63
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
12/28w w w . a u t o s t e e l . o r g
Shear Rake AngleQ3
Front View
Developmental Straight Edge Shearing
Upper Blade
Die Clearance
Sheet Metal
Upper Blade Rake AngleQ2
Back Cut Angle(clearance angle)
Holding Pad
Lower Blade
Lower Blade Rake Angle Q1
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
13/28w w w . a u t o s t e e l . o r g
Upper Blade
Lower Blade
Shear Rake Angle Q3
Adjustable Straight Edge Shearing Device
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
14/28w w w . a u t o s t e e l . o r g
Q3 = 1 degree
Q3 = 2 degrees
Q3 = 3 degrees
Q3 = 4 degrees
Q3 = 5 degrees
Effect of the Shear Rake Angle
Curve
Q3
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
15/28w w w . a u t o s t e e l . o r g
0
5
10
15
20
4 6 8 10 12 14 16 18
001
002003004
S h e a r L o
a d ( K N )
Displacement (mm)
4 degrees
1 degree
2 degrees
67% load drop
22% energy drop
3 degrees
78% load drop
19% energy drop
Shear Load Between Different Shear Rake AnglesQ3
Q3
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
16/28
w w w . a u t o s t e e l . o r g
Transverse Shearing
Sheet Metal
Longitudinal Shearing
Sheet Metal
Specimen Shearing Direction
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
17/28
w w w . a u t o s t e e l . o r g
600
700
800
900
1000
1100
1200
1300
1400
0 1 2 3 4 5 6
363-10%363-15%363-20%
S h e a r L o a d ( L b s )
Time (Sec)
1000
1050
1100
1150
1200
1250
1300
1350
1400
4 5 6 7 8 9
363-L363-T
S h e a r L o a d ( L b s )
Time (Sec)
Different Shearing DirectionDifferent Die Clearance
5.2% energy drop
15.8% energy drop
26.5% energy drop
Comparison of the Shear Load
321
θ,θ,θ : Shear Rake Angle 3θ: Lower Blade Rake Angle 1θ : Upper Blade Rake Angle 2θ
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
18/28
w w w . a u t o s t e e l . o r g
Milled Edge
Sheared Edge
Sheared Edge Tension (SET) Test
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
19/28
w w w . a u t o s t e e l . o r g
22
23
24
25
26
27
28
29
CV JIS 333 363 393 633 663 693 933 963 993
Shearing Condition
T
E ( % )
Conventional
ShearingJSTM
Milled
8% improvement
Total Elongation (TE) Between Different
Shearing Conditions
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
20/28
w w w . a u t o s t e e l . o r g
Tensile failureLocalized
Necking
Fracture
initiation
Edge crack +
Tensile failure
Tensile failure +
Localized Necking
Type (4)
Fracture
As-sheared
edge
Fracture Fracture
Type (3) Type (2) Type (1)
As-sheared
edge
As-sheared
edge As-sheared
edge
Different Failure Modes in the SET test
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
21/28
w w w . a u t o s t e e l . o r g
19
21
23
25
27
29
333 363 393 633 663 693 933 963 993
Shearing Conditions
T E
( % )
10%
15%
20%
12
Effects of Die Clearance
3
DP600, 1mm
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
22/28
w w w . a u t o s t e e l . o r g
Edge Fracture3D Stretching
Half Specimen Dome
Burr Up Condition
Sheared Edge Dome Test
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
23/28
w w w . a u t o s t e e l . o r g
25
30
35
40
45
50
333 363 393 633 663 693 933 963 993
Shearing Condition
D o m e H e i g h t ( m m )
10%
15%
20%
Comparison of the Dome Height
123 3
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
24/28
w w w . a u t o s t e e l . o r g
0%
5%
10%
15%
20%
25%
30%
35%
40%
333 363 393 633 663 693 933 963 993
Shearing Condition
F r a c t u r e
S t r a i n
10%
15%
20%
Comparison of the Strain at Failure
12 23 3
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
25/28
w w w . a u t o s t e e l . o r g
Sheared Edge Limit Strain (SELS)
o
f o
A
A Aq
1001
q
qSELS
Criterion
• The first through-thickness crack at the edge
• The onset of local necking
10
12
14
16
18
20
22
24
10 15 20
Die Clearance (%)
S h e a r e d E
d g e L i m i t S t r a i n ( % ) 333
363
DP980 1.2 mm
Best Shearing Conditions: 363, (333 or 663) with 15% die clearance
(Methodology: Wang, J. et al. 2008, International Conference on New Developments in Advanced High -Strength Sheet Steels)
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
26/28
w w w . a u t o s t e e l . o r g
Conclusions
The experiments confirmed that the use of the optimal hole shearing condition can result in
significantly better edge stretchability for all AHSS.
A computer controlled adjustable straight edge shearing device was successfully developed
based on the findings from the beveled shear hole piercing process.
The maximum shearing force and applied energy can be significantly reduced when proper shear
variables are used during shearing.
The shearing force also depends upon the die clearance, and the larger die clearance tends to
the decrease the shear force.
The sheared edge tension test and dome test confirmed that the optimal setup of the rake
angles in the straight edge shearing process would result in a significant improvement of edge
stretchability for test AHSS.
The optimal shearing condition for AHSS is using the rake angle setup (3,6,3) with 15% die
clearance.
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
27/28
w w w . a u t o s t e e l . o r g
8/17/2019 An Innovative Shearing Process for AHSS Edge Stretchability Improvements
28/28
w w w a u t o s t e e l o r gw w w . a u t o s t e e l . o r g
Great Designs in Steel is Sponsored by: