Three-Dimensional Thermal Model of Resistance Spot Welding in Aluminum

A 3-D thermal model for resistance spot welding in aluminum is presented. The numerical model, validated with experimental findings, considers phase change and the associated weld-pool convection. A parametric study is performed to determine the influence of welding features such as faying surface (work-piece contact surface) contact resistance, current, electrode-work-piece surface-thermal-contact-conductance and electrode tip diameter. These parameters have significant effects on the nugget and heat-affected-zone geometry. The phase change morphology, including melting and solidification rates and weld pool dynamics, is also significantly influenced by the parameters studied. The strongest convection was observed at the center of the molten pool in a plane aligned with gravity. Although two prominent convection cells develop, the phase change morphology is not significantly affected due to the short welding time (less than 0.05 seconds) and low fluid velocity (smaller than 1 × 10−2 mm/s). The nugget grows nonlinearly with increasing current and faying surface contact resistance while diminishing with increasing electrode work-piece surface-thermal-contact-conductance. The influence of faying surface contact resistance on nugget size is less than that of the other parameters. Optimum selection of electrode tip diameter provides the best possible nugget. The duration of weld pool existence increases with the increasing current but decreases with the increasing electrode work-piece surface-thermal-contact-conductance.