Modelling of anisotropic high-cycle fatigue of metals

A continuum approach for anisotropic high-cycle fatigue modelling for metals is described. The approach is based on the idea of an endurance surface moving in the stress space where the movement is described by a back-stress tensor. The movement of the endurance surface is governed by an evolution equation. Thereby, the back stress tensor memorizes the load history so that fatigue damage accumulation can be easily calculated under arbitrary complex loading conditions without cycle counting techniques. Orthotropy and transverse isotropy are treated using the invariant theory. Anisotropic forms for both endurance function and evolution equations for the back stress and damage, are considered. It is also shown that for proportional loading and infinite life time this approach leads to generalizations of Sines criterion to orthotropy and transverse isotropy. Identification of the model parameters is carried out for metallic materials with the experimental results available in the literature.