A simple theory for describing the transition between tensile and shear mechanisms in mode I, II, III, and mixed-mode fracture

Fracture of solids containing a crack is interpreted using basic material data such as the fracture stress in tension, sigma(C), and the fracture stress in shear, tau(C) both being determined from simple laboratory tests. Mode I, II, III, and mixed-mode I/II cases are analyzed individually to confirm the proposed theory. It is shown that the transition of fracture mechanism from tensile to shear, as observed for ductile materials but not observed for brittle materials in many fracture tests, can be properly explained and predicted by incorporating a material strength ratio defined as tau(C)/sigma(C).