Effects of mean stresses on multiaxial fatigue life prediction based on fracture mechanics

A linear elastic fracture mechanics analysis is presented to explore the effects of mean stress on fatigue life prediction under multiaxial loading conditions based on uniaxial fatigue data. Material damage in the form of small cracks is assumed to exist in a material element of interest. The mixed-mode energy release rate or the J integral is used as the primary fatigue damage governing parameter. The uniaxial Goodman relation is generalized to demonstrate the effects of mean stresses on fatigue life under multiaxial loading conditions. The generalization is also applicable for nonlinear constant fatigue life relations in the Haigh diagram.