A Hydrostatic Stress-Sensitive Relationship for Fatigue Under Biaxial Stress Conditions

Failure criteria for elastic- and plastic-strain controlled fatigue under biaxial loading are proposed. The criterion for elastic strain is defined in terms of the equivalent strain from the distortion energy theory and that for the plastic part as the corresponding equivalent plastic strain, but modified to include a function of the hydrostatic stress component. These criteria are incorporated into the derivation of a relationship for fatigue life in terms of the principal strain amplitude, analogous to a conventional form for uniaxial loading. An analysis of some limited available data from the literature shows the potential predictive capability of the relationship.