Grain boundary influence on short fatigue crack growth rate

The influence from different grain boundary configurations on the crack growth rate of a microstructurally short edge crack, located within one grain and subjected to remote fatigue loading, is studied. The study is performed using a dislocation formulation, were the geometry is described by dislocation dipole elements in a boundary element approach and the plasticity by discrete dislocations, located along specific slip planes in the material. Plane strain and quasi-static conditions are assumed. The crack is assumed to grow in a single shear mechanism due to nucleation, glide and annihilation of discrete dislocations. Different grain boundary configurations in front of the growing crack are considered, including both high angle and low angle grain boundaries. It is shown that both grain boundary configuration and distance between the crack and a grain boundary has a pronounced influence on the crack growth rate