Thermal-mechanical modeling on friction stir spot welding of dissimilar materials based on Coupled Eulerian-Lagrangian approach

A model of friction stir spot welding (FSSW) between aluminum alloy 6061-T6 and TRIP 780 steel is developed in this work based on the Coupled Eulerian-Lagrangian (CEL) method, which considers the material flow at the dissimilar material interface and also the interaction between the welding tool and workpiece. The cross-sectional view from the numerical result agrees well with the experimental observations. The material distribution at different plunge depths calculated by the model illustrates the formation of the hook during the welding process. The force and thermal history generated by the numerical work also correspond well with the experimental data. A force history generated through a tool with a smaller shoulder diameter is studied to further validate the model. The developed model can be useful for better understanding the effect of the welding tool on FSSW and optimization of the tool geometry.