Local Mechanical Characterization and Fracture Prediction Modeling for Resistance Spot-Welded Joints of Advanced High-Strength Steel

Abstract

During resistance spot-welding of advanced high-strength steel (AHSS), heat-affected zones (HAZs) are formed and mechanical properties around the welding area are altered, causing a different mechanical response from that of the base metal. This study aimed to develop a finite element modeling method for welded AHSS. Hardness measurements were conducted for JSC590, JSC980, and JSC1180 steels through nano-indentation, and their local mechanical properties were identified using miniature tensile experiments. Then, the correlations between Vickers hardness, tensile strength, and strain were quantified and applied to the shifting of the altered mechanical properties at the HAZ. In the finite element method (FEM) simulations, the nugget parts and HAZ parts of the different FEM models were defined basing on the correlations identified previously. Eventually, the fracture behaviors were elucidated in combination with the MMC model. The simulation results indicate that the fracture strain and tensile stress of each material were predicted within a margin of 0.01 and 38 MPa, respectively. In addition, the behaviors of crack generation and propagation obtained through the simulation were highly consistent with the experimental results. Thus, the fracture behavior of spot-welded AHSS was accurately predicted by the more convenient hardness-based method.

Keywords: Advanced high-strength steel, Resistance Spot-Welding, CAE, Finite element analysis