Crack growth rates for short fatigue cracks in the vicinity of a low angle grain boundary

摘要

The interaction between a low angle grain boundary in front of a crack tip and the emerging plasticity from the tip of a microstructurally short edge crack subjected to fatigue loading has been studied. The modeling rests solely on discrete dislocations, were the geometry is described by dislocation dipole elements in a boundary element approach and the plasticity, restricted to one slip plane, together with the low angle grain boundary is modeled by discrete dislocations. It can be concluded that a low angle grain boundary heavily influences the dislocation movements in the plastic zone. One factor that determines the influence is whether or not the dislocations in the plastic zone have equal or opposite sign as compared to those forming the grain boundary. Another factor is how close the slip plane that holds the plasticity is to a dislocation in the grain boundary when crossing over the slip plane.