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

The influence of various mechanical, metallurgical, and environmental param eters on fatigue crack growth behaviour has been broadly explained elsewher e using the crack closure concept. In this paper the concept of a crack clo sure mechanism map is proposed in order to predict crack closure mechanisms operating under a given set of loading conditions for arty alloy/microstru cture. The domains of plasticity induced roughness induced, and oxide induc ed crack closure mechanisms are mapped in K-max-Delta K space using various boundary equations. In Part 1 of this paper, the boundary equations are de rived from conditions related to the loading conditions.