A model for fatigue crack closure

The phenomenon of fatigue crack closure has attracted continued interest over recent years. This paper concerns itself with one aspect of the phenomenon namely the effects of a single asperity on the crack face close to the crack tip and under dominantly plane strain Mode 1 loading conditions. The model as developed is two dimensional in character but the nature of the closure processes allows it to be applied to real materials. The model illustrates the influence of asperity height, the distance from the crack tip of the asperity and rigidty of the asperity on the crack closure stress intensity. Application of the model to the case of microstructural asperities in nickel alloys and to oxide asperities in steels has met with reasonable success.