A Multiaxial Fatigue Life Criterion Including the Mean Stress Effect Based on π-Plane Projection and Walker Equation

Critical parts of engineering structures are usually subjected to asymmetric multiaxial fatigue loads. In this study, a new multiaxial equivalent stress ratio is defined, combining multiaxial fatigue damage parameters (based on π-plane projection) with the Walker equation to enhance the methodology for considering the effects of mean stress on multiaxial fatigue life. The new mean stress criterion is applicable to biaxial and more complex asymmetric loading conditions. Subsequently, the predictive results of the new criterion are compared with those of three established criteria using experimental data of four commonly used materials reported in the literature. The results indicate that the new mean stress criterion effectively accounts for the mean stress effects in multiaxial fatigue, offering greater simplicity and accuracy than the existing criteria. Furthermore, a good linear correlation is observed between the multiaxial correction exponent and material constants. To further validate the material applicability of the proposed model, multiaxial fatigue tests were conducted on 304 stainless steel under varying loading paths. The results demonstrate that the new criterion possesses good predictive accuracy and applicability, showing significant potential for predicting multiaxial fatigue life in engineering structures.