Failure mode and fatigue behavior of friction stir spot welds in lap-shear specimens of dissimilar advanced high strength steels

Seung Hoon Hong, Katherine Avery, Jwo Pan, Michael Santella, Zhili Feng, Tsung Yu Pan

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Failure mode and fatigue behavior of friction stir spot welds made with convex and concave tools in lap-shear specimens of dissimilar high strength dual phase steel (DP780GA) and hot stamped boron steel (HSBS) sheets are investigated based on experiments and a kinked fatigue crack growth model. Lap-shear specimens with the welds were tested under both quasistatic and cyclic loading conditions. Optical micrographs indicate that under both quasi-static and cyclic loading conditions, the welds mainly fail from cracks growing through the upper DP780GA sheets where the tools were plunged in during the welding processes. Based on the observed failure mode, a kinked fatigue crack growth model is adopted to estimate fatigue lives of the welds. In the kinked crack fatigue crack growth model, the stress intensity factor solutions for fatigue life estimations are based on the closed-form solutions for idealized spot welds in lap-shear specimens. 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.

Original languageEnglish
Pages (from-to)286-292
Number of pages7
JournalSAE International Journal of Materials and Manufacturing
Volume6
Issue number2
DOIs
StatePublished - Apr 2013

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