Failure Modes of Friction Stir Spot Welds in Lap-Shear Specimens of Dissimilar Advanced High Strength Steels under Quasi-Static and Cyclic Loading Conditions

Failure modes of friction stir spot welds in lap-shear specimens of dissimilar high strength dual phase steel (DP780GA) and hot stamped boron steel (HSBS) sheets are investigated under quasi-static and cyclic loading conditions based on experimental observations. Optical micrographs of dissimilar DP...

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Bibliographic Details
Published in:SAE International Journal of Materials and Manufacturing 2012-06, Vol.5 (2), p.375-381, Article 2012-01-0479
Main Authors: Hong, Seung-Hoon, Sripichai, Kulthida, Yu, Chia-Siung, Avery, Katherine, Pan, Jwo, Pan, Tsung-Yu, Santella, Michael
Format: Article
Language:English
Subjects:
Aluminum
Circumferences
Crack propagation
Experimental results
Failure modes
Fatigue
Fatigue life
Steels
Symmetry
Welding
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Summary:Failure modes of friction stir spot welds in lap-shear specimens of dissimilar high strength dual phase steel (DP780GA) and hot stamped boron steel (HSBS) sheets are investigated under quasi-static and cyclic loading conditions based on experimental observations. Optical micrographs of dissimilar DP780GA/HSBS friction stir spot welds made by a concave tool before and after failure are examined. The micrographs indicate that the failure modes of the welds under quasi-static and cyclic loading conditions are quite similar. The micrographs show that the DP780GA/HSBS welds mainly fail from cracks growing through the upper DP780GA sheets where the concave tool was plunged into during the welding process. Based on the observed failure modes, a kinked fatigue crack growth model is adopted to estimate fatigue lives. The fatigue life estimations are reasonably in agreement with the experimental results under low-cycle loading conditions but lower than the experimental results under high-cycle loading conditions.
ISSN:1946-3979
1946-3987
1946-3987
DOI:10.4271/2012-01-0479