Engineering model for the quantitative consideration of residual stresses in fatigue design of welded components

Residual stresses are one of the major factors influencing the fatigue strength of welded components. However, the current IIW bonus factor concept for the mean stress correction is limited to a qualitative evaluation of residual stress effects. By combining residual stress measurements and fatigue testing, the authors derive an improved bonus factor concept that considers residual stresses quantitatively. The proposed concept considers the combined effect of load mean stresses and cyclically stabilized residual stresses. It is pointed out that the yield strength is not a capable measure to determine whether residual stresses have “low” or “extreme” impact on the fatigue strength of welded steels. It is rather recommended to evaluate residual stress effects based on the effective stress ratio reflecting local loading conditions.