Resistance spot welding and the effects of welding time and current on residual stresses

A 2-D finite element model is developed based on fully coupled electrical-thermal and incrementally coupled thermal-mechanical analysis. The growth rate of the weld nugget as a function of welding time and current is studied. Comparison of the predicted results with the experimental data shows good agreement. Contact area variations and pressure distribution between the sheets' faying surface and electrode-sheet interfaces during the welding process are studied. Compressive radial residual stress on the surface of the specimen obtained in the center region of the nugget while it becomes tensile and rises toward the nugget edge. The maximum tensile residual stress occurs outside of the nugget, near the edge region. The effects of welding time and current on distribution and magnitude of welding residual stresses are also investigated. The magnitudes of radial residual stresses in the inner and outer areas of the weld nugget grow with increasing the welding time and current while they decrease slightly in the edge regions of the weld nugget. The growth rate of the maximum residual stress reduces with increase in the welding time and current. This fact is more tangible for welding time.