Detailed model of spot-welded joints to simulate the failure of car assemblies

This paper presents the construction and the validation of a volumic crash detailed model of different spotwelded coupons using the finite element method. The goal of this detailed model is to provide input data for the validation of a simplified model, which will be later on implemented in the complete car model. First, by studying a weld’s cross section, three different areas (spot weld, heat affected zone and basis material) have been identified and characterized using the Vickers hardness test. Moreover, the geometry of the specimen has been carefully analyzed to construct an accurate FE-model. To reflect the different mechanical properties of each zone, a simple method based on the extrapolation of the tensile strength from the Vickers hardness has been used. To compute the damage and the rupture inside the specimen, the Gurson material model implemented in the explicit time integration method “LS-DYNA3D” has been used. The global accuracy of the detailed model is checked by comparing the simulated and experimental force/displacement curves and the weld’s rupture mode under a quasi-static load case of 10 mm/min. This study shows that detailed models of shear-tension, lap-shear and coach-peel specimens are validated for a mild steel.