Failure Mode Prediction of Resistance Spot Welded Quenching and Partitioning Steel

Abstract

In recent years, a novel Advanced High-Strength Steels called quenching and partitioning (Q&P) steel has been applied in the automotive industry because its good combination of strength and ductility. In this study, an experimental setup by adopting digital image correlation (DIC) method was firstly developed to establish the constitutive relationship of fusion zone in the spot welds produced by Q&P980. Stress-strain relationship extracted from the tensile bar within the fusion zone and compared the results to that of base metal. The fusion zone of Q&P980 found to have a higher tensile strength and similar elongation compared with base metal. A numerical model established to predict the failure mode of joints generated by Q&P980 after obtaining the constitutive relationship of fusion zone. The predicted failure mode was in good coherence with the experimental results under the lap-shear test conditions. The developed FE model was proven efficient in tensile strength and failure mode characterization of spot welded specimen. This study could provide solutions to maintain or even improve vehicle crashworthiness of lightweight vehicle structures.