One of them is the energy radiation from the crack front in each act of the rupture. These two factors, the discreteness and the loss of stability during the deformation of the breaking bond, are the basis of a number of phenomena that could not be detected in the framework of the continuum mechanics. The process of destruction is treated as a loss of stability of elastic equilibrium. In 1969, Novoghilov formulated the concept of a brittle fracture, which took account of the discrete structure of the body and suggested the necessary and sufficient criterion for the estimation of the strength of an elastic body weakened by a cut. In this theory, the mechanism of the transition is hidden, the microstructure role and the transition-associated dynamic effects are not reflected.Īs the next step is important for the present work, discrete models were introduced into consideration. One of them concerns the bulk-to-surface energy transition as the energy flux through the crack tip singular point (a line in the three-dimensional case).
Nevertheless, the Griffith theory leaves some questions unanswered.
So, the physical model by itself looks impeccable. It is important to note that the surface energy can be determined in an independent way. In this context, we recall that the theory of brittle fracture founded in 1920 by Griffith is based on the linear elasticity, in the framework of which the stress field is determined, and the energy criterion, which states that the energy release through the moving crack tip must be equal to the (double) surface energy of the material.
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