Finite Element Analysis of Electrode-Tip Configurations in Resistance Spot Welding: Effects on Weld Quality in Dissimilar Aluminum Alloy/Steel Joints

Aluminum alloys are increasingly integrated into the conventional steel car body structures to reduce emissions and increase fuel efficiency. Joining of Al-alloy and steel sheets with the Resistance Spot Welding (RSW) is challenging due to their distinct electrical, thermal and mechanical properties, resulting in a severe heat imbalance between the dissimilar sheets during the process. In the past, a number of research groups have investigated experimentally and numerically the effects of RSW process parameters for similar and dissimilar thicknesses of the same sheets. The objective of the present simulation work is to develop a coupled model, and investigate the RSW of dissimilar Al-alloy/steel sheets with two different combinations of electrode-tip configurations (radius/radius—F/F, and radius/truncated—F/E), and compare the results in terms of current density and temperature distributions and the resulting nugget sizes, flow and residual stresses. The authors observed that the melting of the Al-alloy sheet occurred along the faying surface, while in the steel sheet, it occurred within it. The nugget sizes predicted from the simulations align closely with the measured data from the literature. Also, the residual stresses are lower with F/E electrodes than with F/F electrodes. Therefore, the present study can be further extended to predict the formation of intermetallics at the faying surface.