Evaluation of Spot Weld Fatigue Damage Parameters

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Evaluation of Spot Weld Fatigue Damage Parameters

• HongTae Kang
• Department of Mechanical Engineering
• University of Michigan-Dearborn

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Introduction

• A/SP Fatigue Test Results
• Assessment of Fatigue Damage Parameters
• Rupp and co-workers
• Sheppard
• Kang
• Dong
• Swellam
• Summary

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Specimen Types
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Specimen Matrix
Materials Specimen Type Diameter (mm) Gage (mm) R-Ratio
DQSK TS/CP 7.0 1.6 0.1/0.3
IF TS/CP 7.0 1.6 0.1/0.3
MS 1300 TS/CP 7.0 1.6 0.1/0.3
DP 600/800/980 TS/CP 7.0 1.6/1.6/1.23 0.1/0.3
RA 830 TS/CP 7.0 1.35 0.1/0.3
HSLA 340 TS/CP 7.0 1.5/1.0 0.1/0.3
TRIP 600/800 TS/CP 7.0 1.5/1.6 0.1/0.3
Total specimens 540
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Test Results
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Failure Modes
Tensile Shear
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Assessment of Fatigue Damage Parameters for Spot
Welds

• Rupp and Co-workers
• Sheppard
• Kang
• Dong
• Swellam

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FE Models for Rupps, Sheppards, and Kangs
Parameter

• Tensile Shear

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FE Models for Rupps, Sheppards, and Kangs
Parameter

• Coach Peel

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Rupp and Co-workers

• Cracking in sheet metal due to radial stresses

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Rupp and Co-workers

• Cracking in sheet metal due to radial stresses

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Rupp and Co-workers
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Sheppard

• Assumptions
• Maximum structural stress range at a spot weld
  has direct relationship with fatigue life.
• Fatigue crack propagates through the sheet
  thickness.
• Nugget rotation is negligible.

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Sheppard
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Sheppard

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Sheppard
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Kangs Parameter
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Kangs Parameter
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Kangs Parameter
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Dongs Parameter
From Dongs Seminar notes
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Dongs Parameter
From Dongs Seminar notes
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Dongs Parameter
From Dongs Seminar notes
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Dongs Parameter
From Dongs Seminar notes
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Dongs Parameter
From Dongs Seminar notes
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Dongs Parameter
Tensile Shear
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Dongs Parameter
Coach Peel
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Dongs Parameter
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Swellam

• Assumptions
• Nugget edge as a crack tip
• LEFM
• Combinations of Mode I and Mode II loading

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Swellam

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Swellam
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Swellam
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Summary

• Rupp and co-workers, Sheppards, Kangs, Dongs
  and Swellams parameters were assessed with
  tensile shear and coach peel test data.
• All parameters were good for tensile shear data.
• However, all parameters have the scatter problems
  with coach peel data.
• All parameters correlate with the fatigue test
  results of spot welded joints with reasonable
  accuracy.

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Acknowledgement

• Auto/Steel Partnership
• Sheet Steel Fatigue Committee

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THANK YOU !!!