Brittleness dependence of crack branching in ceramics

A linear correlation between the degree of overloading on the crack tip and brittleness was observed. The intercept, is identified with a minimum condition of overloading where branching occurs at twice the fracture energy. The slope was identified with the degree of plastic deformation at the crack tip necessary to nucleate the branching crack. A total crack tip strain criterion for crack branching in ceramics was investigated. This criterion is supported by the fact that average total elastic strain at the boundary of the yield zone is approximately equal to the square of the slope of the curve