High cycle fatigue of 1045 steel under complex loading: Mechanisms map and damage modelling

A model of life prediction is proposed for a polycrystalline metal subjected to multiaxial complex loading in high cycle fatigue. In order to understand the mechanisms of plasticity and damage to be modelled, a campaign of experiments conducted on 1045 steel is carried out in the first part of the study. The modelling options are chosen according to this precise observation of mechanisms. The modelling focuses on the prediction of finite life regime (10 ⁵ –10 ⁷ cycles). In order to overcome a purely phenomenological description, a two-scale damage model (macro–meso) integrates a multiaxial fatigue criterion and is formulated in the framework of thermodynamics of irreversible processes allowing to capture as closely as possible degradation mechanisms at mesoscopic scale as well as phase shift effect and nonlinear fatigue damage accumulation. The incremental formulation of the proposed model is an asset to deal with variable amplitude loadings in future works.