Studies on effects of pitting morphology in resistance spot welding of aluminium alloy

The effects of two types of electrode pitting morphologies, ring type and hole type, were investigated in resistance spot welding of aluminium alloy 5182 using both finite element analysis and physical modelling 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, no current 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 poses more significant detrimental influence on joint quality than ring type pitting. These effects should be attributed to the distinct influences on contact status and therefore current distribution from electrodes of different pitting morphologies.