Investigation of a growing fatigue crack by means of a discrete dislocation model

A growing fatigue crack under constant load amplitudes is described by means of dislocation mechanics. It is shown that the dislocations are arranged in slip bands which are separated by large dislocation free regions. The accumulation of the dislocations in the wake of the crack produces compressive stresses near the crack tip. During the loading history the closure stress intensity builds up and the crack growth ratio decreases until steady-state conditions are reached.