Numerical study of the mechanical behavior and fatigue in a weld bead by friction stir for a 6082-T6 aluminum alloy

Abstract

The process of friction stir welding is a significant advance in the field of research on the Friction welding technique known for several decades. This assembly technique has obvious originality since welding is performed in the solid state, which can help eliminate birth defects related to solidification phase compared to conventional welding. The numerical modeling of this type of process is complex, not only in terms of the variety of physical phenomena which must be considered, but also because of the experimental procedure that must be followed in order to verify and validate numerical predictions. In this work, a finite element model is proposed in order to simulate the crack propagation under monotonic loading in different areas of the weld seam of a specimen CT-50 aluminum alloy 6082-T6. Microhardness tests were performed to characterize the Vickers hardness profle in the vicinity of the weld area. Friction stir welding process leads to a decrease of the static mechanical properties relatively to base material. Detailed examination revealed a hardness decrease in the thermo mechanically affected zone and the nugget zone average hardness was found to be significantly lower than the base alloy hardness. Welded specimens show significantly lower lives than base material.