Crack tip deformation in LiF single crystals

In this report, mode I crack tip deformation has been studied. Dislocation distributions ahead of a crack tip for two different deformation modes are observed: the first blunts the crack front; jogs the crack front. These deformation modes involve different dislocations and slip characteristics. A dislocation-free zone has sometimes been found in both of these deformation modes. The results show that unloading contributes to deformation in the crack tip region, which is contrary to the usual assumption that removal of the applied load relieves the crack tip stress intensity factor