Continuum damage model for low-cycle fatigue of metals: An overview

Abstract

This work aims to give a comprehensive and accurate view of those micromechanical models that have been developed over the past two decades by our research team. We hereby refer to the distinct capabilities and theoretical difficulties of such models published in various journals by discussing them in a more integrated manner. We also believe that our community can find a significant benefit from this work through below mentioned discussions, which answer many of the questions asked by researchers and those interested in this field. Returning to this work topic, the low-cycle fatigue (LCF) life is highly affected by microstructural instabilities, inhomogeneity and shear bands formation. The first type of damage is related to the nuclei of fatigue microcracks, for several FCC and BCC metals generally governed by continuous irreversible slips within the intensive slip bands. The second type of damage concerns ductile damage caused by cavitation induced by plastic strain and hydrostatic stress. Thereby, fatigue-failure is a relevant topic that requires further explanations to better understand the plausible damaging mechanisms of microcracks and/or microvoids at lower levels of observation. To model the microcracks initiation, some attempts were conducted via micromechanical models assuming, for example, that the microcracks initiate at the crystallographic slip system level describing the LCF response of metals under simple and complex loading paths. In this overview, the latest development of mixed approach with double character called Micromechanical Determinist-Probabilistic Model (MDPM) coupled with damage will be presented with its generalized structure.