Numerical modeling and experimental investigation of material flow in friction spot welding of Al 6061-T6

Material flow during friction spot welding (FSpW) of the aluminum alloy Al 6061-T6 was examined by a combination of numerical modeling and experimentation. The finite element model was developed according to coupled Eulerian-Lagrangian formulations, where the Johnson-Cook equation was used to describe the dependence of stress on temperature, strain, and strain rate. The modeling results revealed that the hook defect was formed due to the insufficient material deformation and low material diffusion rate. A model of the material flow in FSpW was developed based on the numerical and experimental results. The onion structure near the sleeve periphery was formed during the plunge stage when materials beside and below the sleeve were combined.