Nonlinear elastic constants of solids with cracks

Experimental data on a cracked medium exhibiting high acoustic nonlinearity is a commonly observed phenomenon. Here a physical model of a medium with cracks is suggested to explain the observed phenomena. The model is based on the assumption of uniform stress that is valid for a low concentration of cracks. The crack behavior is described using the model in which a crack is represented as an elastic contact of two rough surfaces, pressed one to the other under the action of internal stresses in the surrounding solid. Linear and nonlinear acoustic constants of the fractured medium are calculated. It is shown that, in this medium, negative values of the Poisson's ratio and anomalously high values of the nonlinear constants are possible. (C) 1997 Acoustical Society of America. [S0001-4966(97)05910-9].