Computational analysis of thermo-mechanical characteristics in refill FSSW of thin AA7075-T6 sheets using smoothed-particle hydrodynamics

A 3D thermo-mechanical model was developed employing the smoothed-particle hydrodynamics (SPH) technique to simulate the refill friction stir spot welding (refill FSSW) process and its tool plunging variants. SPH is a Lagrangian particle-based approach that can directly trace field variables� histories, handle large material deformations, and capture moving interfaces. These features of SPH make it appealing for the refill FSSW process, where the change of field variables is challenging to monitor experimentally. The numerical model of the shoulder-plunging variant (SP-refill FSSW) was validated by comparing results to experimental thermal data from the published literature. The temperatures correspond well with the experimental thermal data, and the model accurately predicted temperatures in the weld zone with an error of 0.52. The thermal distribution, plastic strains, and material flow behaviours of the SP-refill FSSW and probe plunging variants (PP-refill FSSW) during the process are presented. The hook formation in connection with the material flow of the process is explained. The SPH numerical model can simulate refill FSSW, withstand severe deformations, and efficiently predict the field variables that help in a deeper understanding of the thermo-mechanical characteristics and joint formation in refill FSSW. © 2023, The Author(s) under exclusive licence to OWZ.