The Theory of Brittle Fracture Initiation under Triaxial Stress Conditions?I

A calculation has been carried out of the conditions under which crack propagation is initiated in an isotropic, brittle solid of the Griffith type when the solid is subjected to a homogeneous, uniform but otherwise arbitrary triaxial system of stresses at infinity. The cracks have been taken to be flattened ellipsoidal cavities. The results are in broad agreement with results obtained in the two-dimensional treatment of the problem, and with experimental observations. Tensile and shear fracture is possible and the Mohr envelope is of parabolic form. Fracture initiation is shown to be independent of the intermediate principal stress.