Crack growth rates for short fatigue cracks simulated using a discrete dislocation technique

The influence on the crack growth rate for a short edge crack under fatigue loading due to changes in crack length, grain size, load range and grain boundary configuration, is investigated under quasi-static and plane strain conditions. The geometry is modelled by distributed dislocation dipole elements in a boundary element method approach and the plasticity is described by discrete dislocations. The crack is assumed to grow due to nucleation, glide and annihilation of dislocations along slip planes in the material in a single shear mechanism. The results of the investigation are compared to typical growth rates for long cracks and it is found that the increase in growth rate due to a prescribed stress intensity factor range was much less pronounced as compared to what holds for long cracks.