Influence of crack tip plasticity on the slope of fatigue curves for laser stake-welded T-joints loaded under tension and bending

The paper investigates the crack tip plasticity of laser stake-welded T-joints when loaded in tension and bending. Irwin's first-order plastic zone size is kept equal for the selected load levels, and finite element (FE) analyses are carried out to investigate the stress redistribution in the plastic zone varying the applied loads. The results allow us to explain why the fatigue slope m is different for bending and tension. Moreover, a new method is proposed that permits the number of cycles to failure under bending to be derived directly from the tension fatigue curve, employing an effective J-integral. The results prove that the method is able to give an estimation of the number of cycles to failure under bending with a very good approximation and acceptable errors.