Numerical and Experimental Study on Nugget FormationProcess in Resistance Spot Welding of Aluminum Alloy

The weld nugget formation in the resistance spot welding （RSW） of aluminum alloy was investigated inthe present study. The nugget formation process was directly observed by using a digital high-speed camera. Numericalsimulation was also employed to investigate the nugget formation process. The results showed that for the RSW oftwo aluminum alloy sheets, a nugget was first formed in the workpiece/workpiece （W/W） interface and grew alongthe radial direction and axial direction of the sheets, and then it became a large elliptical nugget. For the RSW of threealuminum alloy sheets, two small nuggets were firstly formed in two W/W interfaces and grew along the axial directionand radial direction; finally they fused into one nugget. Besides, there existed a critical welding time, after whichthe nugget size remained nearly unchanged. This indicates that a long welding time is unnecessary for the RSW ofaluminum alloy. In addition, the calculated nugget radius was compared with the experimental results, which showedthat the simulation results agreed well with the experimental results.