Residual Stresses in Friction Stir Welding: Numerical Simulation and Experimental Verification

In the present paper the effects of the thermal and mechanical actions on the residual stress field occurring in friction stir welding (FSW) of AA7075-T6 were investigated. Both numerical and experimental analyses were carried out to highlight the metallurgical phenomena and induced residual stresses in FS welded blanks. The welding process was simulated using a continuous rigid-viscoplastic finite element model (FEM) in a single block approach through the software DEFORM-3D, Lagrangian implicit code designed for metal forming processes. Then, the temperature histories at each node of the FE model were extracted and transferred to a further FE model of the joint considering an elasto-plastic behavior of the AA7075-T6 material. The map of the residual stress were extrapolated from the numerical model along several directions. Thus the cut-compliance methodology was used to compare the residual stress profiles with those of the numerical model. The numerical-experimental comparisons have shown how the numerical model can be successfully used to predict the residual stress field in FSW joint by considering all the local mechanical action of the tool.