Numerical Simulation of Failure Behavior of B1500HS Hot-Stamped Steel Spot Weld

Resistance spot welding tests were conducted on B1500HS hot-stamped steel. A test matrix encompassing tensile, shear, bending, torsional, and coupled loading conditions was designed, and failure tests of the spot welds were performed. The failure behaviors of spot welds was studied under different loading conditions. A partitioned finite element model of the spot welds was established, which simultaneously considered the failure of both the weld nugget and the heat-affected zone. A coupled damage-failure constitutive model was proposed to describe the failure surface of the weld nugget. The model parameters were determined and the accuracy of the model in simulating spot weld failure behavior was verified through the correlation of test and simulation results. The results show that the B1500HS hot-stamped steel spot welds exhibited two failure modes under the test matrix conditions, including the weld nugget failure and the heat-affected zone failure. The failure locations of the spot welds simulated by the established model under the test matrix conditions were consistent with the test results. The average relative errors for the peak load and fracture displacement between the simulation and test results were 4.0% and 5.0%, respectively, meeting the accuracy requirement for full-vehicle crash simulation （less than 15%）. This demonstrated that the proposed partitioned modeling approach for spot welds and the coupled damage-failure constitutive model for the weld nugget could effectively predict the mechanical behavior of B1500HS hot-stamped steel spot welds during crash failure processes.