Micromechanical modeling of low cycle fatigue under complex loadings. I: Theoretical formulation. II: Applications (Q1369811)

A micromechanical model of the early fatigue damage initiation is proposed based on the slip theory. For each slip system, a local micro-damage variable is introduced to describe globally all phenomena related to the level lower than the crystallographic slip system, such as dislocations, atoms, molecules, lattice defects, etc. of FCC polycrystalline materials. This transgranular damage variable is fully coupled with micro inelastic constitutive equations. It is supposed that the local damage appears when the dislocation density reaches some critical values. The obtained model describes the cyclic behavior of metallic materials under proportional and non-proportional loading paths neglecting the quasi-unilateral effect as well as the localization of the fatigue damage on the free surface of the specimen. A number of numerical tests are carried out to demonstrate the possibilities of the model.