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.
Failure Modes of Friction Stir Spot Welds in Lap-Shear Specimens of Dissimilar Advanced High Strength Steels under Quasi-Static and Cyclic Loading Conditions
Sae Int. J. Mater. Manf
Sae International Journal of Materials and Manufacturing
SAE 2012 World Congress & Exhibition ; 2012
Sae International Journal of Materials and Manufacturing ; 5 , 2 ; 375-381
2012-04-16
7 pages
Conference paper
English
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