GRAIN BOUNDARY INFLUENCE DURING SHORT FATIGUE CRACK GROWTH USING A DISCRETE DISLOCATION TECHNIQUE

We have studied the effect of a grain boundary in front of a short edge crack on its propagation under cyclic loading conditions in bcc iron. The used model is a combination of a discrete dislocation formulation and a boundary element approach where the boundary is described by dislocation dipole elements, while the local plasticity is modeled by discrete dislocations. The grain boundary is considered impenetrable, but dislocations positioned in the vicinity of a grain boundary give raise to high stresses in neighboring grains which, eventually, results in nucleation of dislocations and a spread of the plastic zone into the next grain.