Development of fatigue crack closure mechanism maps Part 1 - Basic concepts and boundary equations

The influence of various mechanical, metallurgical, and environmental parameters on fatigue crack growth behaviour has been broadly explained elsewhere using the crack closure concept. In this paper the concept of a crack closure mechanism map is proposed in order to predict crack closure mechanisms operating under a given set of loading conditions for any alloy/microstructure. The domains of plasticity induced, roughness induced, and oxide induced crack closure mechanisms are mapped in Kmax-ΔK space using various boundary equations. In Part 1 of this paper, the boundary equations are derived from conditions related to the loading conditions.