Monitoring of Dynamic Mechanical Parameters in Resistance Spot Welding of Aluminium

Dynamic electrode displacement and force were characterized during resistance spot welding of aluminium alloy 5182 sheets using a medium-frequency direct welding current. It was found that rates of increase in electrode displacement and force were both proportional to welding current. Both electrode displacement and force experienced a sudden drop when weld metal expulsion occurred. However, the rate of increase in electrode displacement did not reach zero during welding even for joints with sufficient nugget diameter, while electrode force peaked for the same nugget diameters. Possible strategies for process monitoring and control are also discussed.