FEM Model and Experiments for Friction Stir Spot Welding of AA6061-T4

Danut Iordachescu, Dan Birsan, Mihaela Iordachescu, Juan Porro, José Luis Ocaña

This paper presents a 3D model based on FEM, used to study the thermo-mechanical processes and the resulting state of strains and stresses after Friction Stir Spot Welding of AA6061-T6 aluminium alloy. An original 3D FEM model of Friction Stir Spot Welding was developed using the MARC Mentat 3.0 code. The heat source used for modelling was described by the friction between the material and the tool. The outputs of the model are the thermal, and the stresses and strain fields, respectively. To validate the thermal field results of the modelling, the literature references were used, both from experiments and other FEM analysis. On the other hand, experiments to validate the state of stresses were necessarily performed. Experimental determination of the strains and stresses field was performed both by using blind hole drilling method, and contour machining method, respectively. HV micro-hardness test were performed, based on the proved correlation between hardness and state of stresses. Microstructural analysis was meant supporting a detailed experimental analysis. The correlation between the calculated residual stresses of the processed zone and the process parameters, such as tool rotation and advancing speeds is presented. It is presumed that the model can be extended to optimize the FSP/FSW process in order to control the residual stresses of the processed zone, and in the weld, respectively.