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A Fatigue Life Prediction Method of Laser Assisted Self-Piercing Rivet Joint for Magnesium Alloys

Hong-Tae Kang1, A.K. Khosrovaneh2, Xuming Su3, Mike Guo4, Cindy Jiang5, Yung-Li Lee4, and Zhen Li1

1The University of Michigan- Dearborn2General Motors, LLC.3Ford Motor Company4Fiat Chrysler Automotive5AET Integration, LLC.

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• Fatigue Testing• Various Joints: Spot, SPR, FSLW, GMAW, Adhesive, Solder• TMF• Round Bar Specimen, 4-point Bending

• FEA based Fatigue life analysis• S-N• E-N• Structural Stress Approaches

Fatigue Analysis and Testing Lab in UM-Dearborn

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Challenge/project scope

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Fatigue Testing: Coupon

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Structural Stress Approach

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Structural Stress Approach

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Structural Stress Approach

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Structural Stress Approach

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Fatigue Testing: Sub-Structural Specimens

*Specimen design and fatigue testing wereconducted by AET Integration

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Fatigue Testing: Sub-Structural Specimens

*Specimen design and fatigue testing wereconducted by AET Integration

6,832 cycle

35,292 cycle

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Predicted Life vs. Experimental Life

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• Tensile shear and coach peel specimens were fabricated and tested to characterize the fatigue performance of magnesium LSPR joints.

• Based on the observation of the failure modes of the joints, it was assumed that the mechanics at the LSPR joint was similar to that of the electrical resistance spot weld joint.

• Therefore, the same structural stress parameter equations as used in spot welded joints were used to analyze Mg LSPR joints.

• The structural stress parameters were then used to predict the fatigue life of sub-structural (or component-like) specimens. Results of fatigue tests of sub-structural specimens and the prediction results were also compared.

Summary/Conclusions

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From this study, the following conclusions may be made:• While the test results (load range vs. Life) of Magnesium LSPR TS

and CP specimens are quite different, these differences are minimized once the data is presented as structural stress range versus life.

• In the high cycle fatigue regime, the failures in magnesium alloy LSPR appears as an “eyebrow” crack very similar to that observed in the fatigue of electrical resistance spot welds.

• Structural stress equations and methodology developed for electrical resistance spot weld are applicable to magnesium LSPR joints.

Summary/Conclusions

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• This material is based upon work supported by the Department of Energy National Energy Technology Laboratory under Award Number DE-EE0005660, with the United States Automotive Partnership LLC (USAMP). This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Acknowledgments

March 4-5, 2015 2015 HBM nCode Products User Group Meeting Livonia, MI (USA)

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2015 HBM nCode Products User Group Meeting

Thank you!

March 4-5, 2015 2015 HBM nCode Products User Group Meeting Livonia, MI (USA)

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