A THREE-DIMENSIONAL FINITE ELEMENT ANALYSIS FOR A CRYSTALLOGRAPHIC CRACK NEAR THE INTERFACE OF AN INCOMPATIBLE BICRYSTAL

On the basis of modelling bicrystal deformation, using three-dimensional, anisotropic finite elements, the problem of a crystallographic crack approaching the interface in a 111] tilt bicrystals of 90? misfit angle under shear loads is solved. The influence of thickness direction material heterogeneity across the interface on the distribution of the stresses, strains and crack sliding displacements along the crack front near the interface has been revealed. As the crack approaches the interface, those mechanical parameters are considerably changed by the heterogeneity across the interface. Remarkable variations in the stresses and strains along the crack front have also been identified and are referred to the different constraint across the thickness. The maximum stress may shift from the crack tip to the interface ahead of it, where, as suggested by numerical results and previous experimental observation, a new fracture process core may be activated. The interface-induced crack shielding or antishielding under mode II and III loading is analyzed and discussed.