Abstract: The effect of electrode pitting on the welding quality in resistance spot welding (RSW) of aluminum alloy AA5182 is investigated using both finite element analysis and physical modeling methods. Results show that with the increasing of the pitted area at the electrode tip, the actual contact area at electrode/sheet interface does not change so much, while the contact area at sheet/sheet interface is increased significantly, therefore, the current density at the sheet/sheet interface is reduced greatly, and the thickness and diameter of the nugget formed are both decreased. Dimensions and shapes of the nuggets from physical modeling are in very good coincidence with numerical predictions. Only a donut shape nugget with very limited thickness is formed when the diameter of the pitting hole is 5.0 mm. These results reveal that the increasing of contact area at sheet/sheet interface by the increasing pitting hole diameter at the electrode tip is one of the major causes for worse and worse welding quality during RSW of aluminum alloys.

Key words: Aluminum alloys, Electrode pitting, FEM modeling, Resistance spot welding