A coupled finite element model to study on mechanical and thermal features of resistance spot welding process with experimental verification

Resistance Spot welding (RSW) is a strong coupling process which involves electrical, thermal, and mechanical interactions. These make the whole welding procedure highly non-linear and difficult to model. In this paper, finite element analyzing tool, ANSYS, was used to simulate and model RSW. In order to improve accuracy, material properties were defined temperature-dependent and phase transformation was taken into account in simulation. The steel sheets in this study were AISI 1008 steel. The key parameters of the process including, contact radius, contact pressure, and temperature distribution were investigated. Also development of weld nugget during process was investigated and numerical calculations for nugget size showed good agreement with experimental results. This causes the weld nugget diameter abnormal variations and consequently reduces the weld strength. Therefore the tip of the electrode should be dressed in this process With these results, optimum settings for current, timing, and pressure of the spot welding machine can be formulated for different materials to produce the desired welding quality. In addition to magnitude of welding current, current shunting phenomenon affects the nugget size. In order to investigate the effect of electric current shunting, some tests were designed and simulated.