The effect of residual stresses on fatigue crack propagation in welded stiffened panels

This paper presents a method for predicting fatigue crack propagation in welded stiffened panels accounting for the effects of residual stresses. Well known power law models were employed to simulate fatigue life for a welded stiffened panel specimen damaged with a central crack. Stress intensity factor values (SIF) were obtained in finite element (FE) analyses by a linear superposition of the SIF values due to the applied load and due to weld residual stresses. The FE models included idealized, rectangular or triangular, residual stress distribution profiles. The effect of welding residual stresses on the crack propagation rate is taken into account by replacing the nominal stress ratio R in the power laws by the effective stress intensity factor ratio R-eff. The considered stiffened panel specimen, made of mild steel commonly used in ship structures and manufactured by electric arc welding process, was subjected to the fatigue test with constant amplitude loading until failure occurred. By using the presented method remaining fatigue life of welded stiffened panel specimen was analysed. The simulated crack growth rate was relatively higher in the region of tensile residual stresses and lower between the stiffeners where compressive residual stresses prevail, which is in good agreement with physical principles and experimentally obtained results.