Microstructure-Sensitive Computational Fatigue Analysis

Abstract

Previous sections focused on plasticity and damage formation and evolution under monotomic loading. Under cyclic loading, fatigue failure is a significant consideration. Historically, simple macroscopic fatigue correlations have proven quite useful in estimating fatigue crack initiation life of metallic components, based on measured or calculated stresses and strains at notches in components. The application of stress-based criteria for high cycle fatigue (HCF) or plastic strain-based criteria for low cycle fatigue (LCF) is typically based on transfer of results from tests on relatively small scale notched and unnotched laboratory specimens to larger components (cf. [1]). At the macroscale, fatigue of ductile materials has many common characteristics among alloy systems, leading to the utility of strain-life criteria. At the level of microstructure, fatigue is a complex, cycle-dependent process that differs in detail from one alloy system to the next. Often it is desired to understand mean fatigue resistance and scatter in fatigue as a function of microstructure in order to tailor microstructure to improve component level fatigue resistance. To this end, extension of fatigue analysis methods to microstructures is necessary as a means to augment and reduce the number of required experiments.