NUMERICAL SIMULATION OF SPOT WELDED STEEL SHEETS

The welding process leads to heating of the very heterogeneous metal, volumes of material knowing the melting temperature levels. The subsequent cooling is heterogeneous from the point of view of the rate of change in temperature. The melted zone solidifies to reach the ambient temperature by changing the microstructure of the metal, the residual stresses and deformations. These are generated both by the heterogeneous nature of the temperature variations, by the crystal transformations related to the heat treatment induced by the welding and to the forces related to the lateral pressure imposed by the electrodes through which circulates the current required for the welding. This article aims to calculate the levels of stress encountered locally to justify the sites of initiation of fatigue cracks under tensile-shear load of specimens welded by point. Stress levels do not alone justify the fatigue behavior of a material when it does not exhibit homogeneous properties of fatigue resistance in the volume studied. Nevertheless, the distribution and stress levels encountered are a valuable contribution to the understanding of local fatigue damage, the sensitivity of stress levels and their spatial distribution in the welded spot and their immediate vicinity will be studied in relation to several geometric parameters which are variable in specimens. The aim of the numerical model implemented is therefore, to some extent, to identify the critical zones of the welded point and to quantify the influence of certain geometric hazards