A Method Based on Virtual Strain-Energy Parameters for Multiaxial Fatigue Life Prediction

A new method is proposed for multiaxial fatigue life prediction using correlation parameters based on virtual strain energy as a measure of fatigue damage on critical planes of fracture. The virtual strain-energy parameters are physically associated with two different modes of fatigue fracture planes. The critical plane leading to Mode I fracture is driven by the principal stress and strain, and the other, leading to Mode II fracture, is driven by the maximum shear stress and strain. The mode of crack initiation and propagation depends on material, temperature, strain range, and stress and strain histories, but not on the relative magnitude of the virtual strain-energy parameters. Biaxial fatigue data obtained from the literature were analyzed for Type 304 stainless steel tested at room and elevated temperatures and for SAE 1045 steel tested at room temperature under in-phase and 90° out-of-phase loading conditions. Comparisons are made between experimental data and theoretical predictions to show the effectiveness of the proposed method.