Effects of electrode pitting morphology on resistance spot welding of aluminum alloy

The effects of two types of electrode pitting morphologies, ring type and hole type on resistance spot welding of aluminum alloy 5182 were investigated by the combination of finite element analysis and physical modeling methods. Results showed that when using ring pitting electrode, the contact radius at faying surface is increased while the current distribution is not affected notably, and the nugget diameter is increased. When using hole pitting electrode, the contact radius at faying surface is increased further and the current density is decreased in the contact region. In addition, electric current does not flows through the central part of faying surface under such conditions, consequently, central part does not melt and only donut shape nugget is formed. Hole type pitting reduces the joint strength significantly, and its detrimental influence on joint quality is much greater than that of ring type pitting.