A model for multiaxial small fatigue crack growth

摘要

This paper extends the critical plane multiaxial fatigue model of McDowell & Berard (1992) and McDowell & Bennett (1996) to encompass basic phenomena of microstructurally and physically small cracks,including interaction with microstructure and associated threshold conditions.amplitude and stress state dependence of the fatigue crack growth rate.Dependence on microstructure for small cracks under high cycle fatigue conditions is augmented by consistency with the LEFM threshold in the physically small crack regime to form a complete,stress state-dependent Kitagawa diagram. Crack growth rate relations which approximate the slip transfer model in the three regimes - (I) microstructurally small, (II) transition from microstructure sensitivity,and (III) physically small - are nondimensionalized above threshold in terms of applied stress and crack length to facilitate weighting of the regimes in accordance with the strain-life relations.Various aspects of the framework are discussed for multiaxial loading conditions.