Mean stress effect correction using constant stress ratio S–N curves

Abstract

This paper presents a stress based approach to take into account the influence of the mean stress value on fatigue strength of constructional materials. Elaborated model uses two S–N curves, i.e. for alternating stress (R=−1) and another one obtained under stress ratio R≠−1, for calibrating the equations of boundary condition. Two particular equations for the coefficient of intensification in stress transformations were proposed. The main advantage of the proposed solution is that the mean stress effect correction depends on the number of cycles to failure, what corresponds to the observed changes in experimental results presented in the literature. Proposed relations were compared with popular models for mean stress correction. The verification was made using selected series of experimental results taken from the literature. It was shown that the proposed solution is well correlated with experimental results.