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In this numerical study, three dimensional transient heat transfer analysis of Friction Stir Welding of two 8mm-thick AA-6061-T651 (an aluminum alloy) slabs has been performed. The numerical tool is the commercial package Comsol © where the domain is modeled as a rectangular aluminum slab with a moving heat source along the centerline, as was the case in the experimental setup whose results have been compared to those of Comsol. Comparison has shown that moving heat source boundary condition to account for the heat input from the tool shoulder generates realistic results and thus can be a standard in similar problems. The findings of this work are believed to be a reference for future research on this area.

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Hard-facing process is widely used for improving the wear resistance of mild steel. During the application of hard-facing, due to high temperatures, residual stresses and deformations may occur. The tensile residual stresses may cause crack propagation on the hard-faced part. The purpose of this study is to utilise minimum computer work for minimizing these residual stresses and deformations during the hard-facing of mild steel. The fully coupled transient heat transfer and structural analysis was performed for calculations. The double-ellipsoidal moving heat source was utilised to simulate the heat input from the gas metal arc welding (GMAW). Only eight numerical simulations were performed to minimize the computer work; the grey relational analysis was used for minimizing both the residual stresses and deformations. Welding speed, welding current, and welding pattern were considered as changing parameters. At the end of the numerical and statistical solutions, it is observed that heat input should be kept minimum to minimize the stresses and deformations. But it is obvious that the heat input must provide a temperature greater than the melding point. Straight patterns always produce better results for minimizing stresses and deformations. Transverse stress at the beginning and end of the longitudinal path gets higher significantly after cooling. Cooling does not affect the total deformation.