Numerical modelling of crack propagation in friction stir welded joint made of aluminium alloy

Abstract

In this work, fatigue crack propagation in thin-walled aluminium alloy structure with two friction stir welded (FSW) joints has been numerically modelled. Crack propagation in unstiffened part of the structure between two FSW joints is analyzed. Numerical method, so-called eXtended Finite Element Method (XFEM) has been used, including software Abaqus, as well as Morfeo, for modelling and results display. Tensile fatigue loading is applied, with stress ratio R=0. The analyzed model is made from aluminium alloy 2024-T351. Material properties in joints zones and geometry measures of FSW joint are adopted from available experiments. Following results are obtained by numerical analysis: stress-displacement state in the structure, where special attention is dedicated to the crack tip zone, coordinates of the crack front (x, y, z) for every propagation step, distributions of stress intensity factors - K-I, K-II, K-III and K-eq along the crack front for each propagation step, structural life in form of change of applied number of load cycles, N, for each step of propagation. Besides numerical results, Abaqus provides visualization of crack propagation in the structure. On the basis of obtained data, analysis of crack growth stability is done.