Fatigue life prediction based on equivalent stresses for laser beam welded 6156 Al-alloy joints under variable amplitude loading

Abstract

In the present work, a simple fatigue life prediction approach is proposed using fracture mechanics for laser beam welded Al-alloy joints under variable amplitude loading. In the proposed approach, variable amplitude loading sequence is transformed into an equivalent constant amplitude loading using the root mean square model. The crack growth driving force K* is chosen to describe the fatigue crack growth rate. The influences of residual stress and its relaxation on fatigue life are taken into account in the proposed approach. The fatigue lives are also predicted using the traditional approach based on the S-N curves and the rainflow counting method. The predicted results show that the proposed approach is better than the traditional approach.