The effect of residual stress on mixed-mode crack propagation behaviour in friction stir welded 7075-T6 aluminium alloy panel under biaxial loading

The effect of residual stress on mixed-mode crack propagation behaviour in friction stir welded (FSW) 7075-T6 panel under biaxial loading was investigated. Stress intensity factors (K_I and K_II) were used to study the effects of residual stress on crack behaviours with five different biaxial loading ratios. It was observed that residual stress has a considerable effect on the mixed-mode crack growth. In most cases, the crack deviation from the initial crack is mainly affected by residual stress at the beginning of crack propagation. The variation of crack path is strongly linked with the residual stress as well as the biaxial loading ratio. In addition, K_I and K_II are susceptible to residual stress under biaxial loading conditions. Residual stresses contribute to a higher proportion of K_II compared with that of K_I. K_I and K_II in the retreating side are more affected by the residual stress.