A Unified Numerical Approach for Multiaxial Fatigue Limit Evaluation

A unified numerical approach to evaluate the endurance limit for general multiaxial fatigue loading, under proportional or nonproportional loading, is presented. A minimum circumscribed ellipsoid approach is proposed for computing the amplitude and mean value of the equivalent shear stress, and an efficient numerical algorithm is developed for solving the min–max problem by using a constrained optimization method. The approach is general and efficient, especially suitable for computer-aided design and optimization. With this approach, nonproportional loading effects can be taken into account, overcoming limitations of many other multiaxial fatigue criteria. Experimental results collected from the literature are compared with results predicted by the numerical approach proposed in this paper. The comparison shows that the predictions agree well with experiments for both proportional and nonproportional loading situations.