Influence of fatigue load range on the growth of a microstructurally short edge crack simulated by a discrete dislocation formulation

Quasistatic propagation of a short edge crack, located within one grain of a bcc material has been studied using a discrete dislocation technique. The geometry is modelled by distributed dislocation dipole elements and the plasticity by discrete dislocations. The crack is assumed to grow through a single shear mechanism due to nucleation and annihilation of dislocations along preferred slip planes in the material. The change in growth rates due to different load cycles and due to a small single overload was investigated. It was found that the growth rates were strongly influenced by the applied load cycles, and that a single overload affects the growth differently depending on the number of cycles prior to the overload.