Fracture Process Zone in Cracked Nonlinear Orthotropic Body

The first basic plane stress state problem of the equilibrium of a nonlinear orthotropic body with a mode I intrinsic crack is stated in the terms of displacement vector components. It is supposed that there is a fracture process zone at the vicinity of each crack tip. In deriving invariant equations, the model of the fracture process zone in form of an open slit with a stress vector on its surfaces was used. The state of the fracture process zone is described by equations including a scalar function with two constants. The solution of the boundary-value problem has shown that the single non-zero component of the stress vector at points on the body surfaces, specific fracture energy as well as the single non-zero component of the stress vector at points on the slit surfaces, and the slit opening depend on the above constants. It is established that these constants affect the shape of the nonlinearity zone adjacent to each crack tip. An experimental-theoretical method to determine the constants is proposed.