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Impact Modeling of Spot WeldsIn High-Strength Steels
Dr. Robert YanceyMr. Warren PetersonEdison Welding Institute
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020406080
100120140160180200220
0 10 20 30 40 50 60
Engineering Strain (%)
Engi
neer
ing
Stre
ss (k
si)
Stress-Strain Curves
1330 MPa
315 MPa
700 MPa
966 MPa
Stress-Strain Behavior of Steel
Ref: SAE 2000-01-2681
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Cross Tension Sample
Ref: SAE 2000-01-2681
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Equipment
Drop Weight Impact Tester
Unique Sample DesignSpring
Strikerand
Load Cell
LockingMechanism
Sample
Ref: SAE 2000-01-2681
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Steel Strength on Absorbed Energy
Ref: SAE 2000-01-2681
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Steel Strength on Peak Load
Ref: SAE 2000-01-2681
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Absorbed Energy on Peak Load
Ref: SAE 2000-01-2681
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Impact Modeling Set-Up – Axial Load
Constraints
Initial Velocity
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Rigid Link Weld
• Standard Weld Connection
• Node to Node• Failure Criteria:
1≥⎟⎟⎠
⎞⎜⎜⎝
⎛+⎟⎟
⎠
⎞⎜⎜⎝
⎛m
s
sn
n
n
Sf
Sf
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Effect of Mesh Size – Axial Load
Smaller mesh size Longer Life
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Model Deformation - Axial Load
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Mesh Independent Welds
• Element to Element
• Contact Definition• Standard Failure
Criteria:
pfp εε ≥
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Effect of Mesh Size – Axial Load
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Effect of Weld Placement Configuration Axial Load
1
2
3
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Model Deformation – Axial Load
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Impact Modeling Set-Up – Offset Load
Constraints
Initial Velocity
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Rigid Link Weld
• Standard Weld Connection
• Node to Node• Failure Criteria:
1≥⎟⎟⎠
⎞⎜⎜⎝
⎛+⎟⎟
⎠
⎞⎜⎜⎝
⎛m
s
sn
n
n
Sf
Sf
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Effect of Mesh Size – Offset Load
Smaller mesh size Longer Life
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Model Deformation – Offset Load
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Mesh Independent Welds
• Element to Element
• Contact Definition• Standard Failure
Criteria:
pfp εε ≥
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Effect of Weld Placement Configuration – Offset Load
1
2
3
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Effect of Weld Placement Configuration – Offset Load
1
2
3
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Model Deformation – Offset Load
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Mesh Independent Welds
• Element to Element
• Contact Definition• Failure Criteria:
0122
=−⎟⎠⎞
⎜⎝⎛+⎟
⎠⎞
⎜⎝⎛
FFrr
rr
ττ
σσ
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Effect of Weld Placement Configuration – Offset Load
1
2
3
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Effect of Weld Placement Configuration – Offset Load
1
2
3
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Spot Weld Modeling Conclusions
• Rigid Link Elements are highly mesh dependent
• Mesh Independent Elements are highly dependent on Element location
• Test data is limited
Current Methods are Unreliable
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Modeling Vision
0
300
600
900
1200
0 0.05 0.1 0.15 0.2 0.25Total Strain
True
Str
ess
(MPa
)
Location 1 Location 2
Location 3 Location 4
Location 5
Material Properties
Weld Simulation
Structural Analysis
