But then the conditions of the development of cracks are subordinate to the elastic laws in which normal stresses have a prevailing value.
As you know, the development of cracks occurs when the concentration of normal stresses at the end of the crack and the corresponding value of the energy of deformation reaches a critical value equal to surface energy on the surfaces of the integrity of the integrity. A feature of the consistent destruction under consideration with the high development of plastic deformations is only that this value of normal stresses depends on the speeds and values of plastic deformations, since normal voltage is its own voltage of the second kind along the sliding line, depending on these speeds.
The loosening of the structure is also of great importance in the process of destruction, as we have seen extremely significant during the period of destruction. During this period, it determines the intensive development of plastic deformations that are increasingly approaching the diffusion type. Local defects and weakening should be distinguished from this general loosening; the latter violate the uniformity of the distribution of plastic deformations, concentrating stresses, and this facilitate the process of destruction. However, they cannot be attached to the dominant value, since the process, despite the whole variety of defects, is extremely stationary and since the large -scale factor in the process of viscous destruction is not significant. The dominant value belongs to the general mechanical laws and the general loosening of the structure. Thus, the mechanism of viscous destruction is quite difficult. We see that the idea of the mechanism of destruction as a destruction from cutting is possible correctly as a general representation, since tangent stresses and plastic deformations are the main factor that determines the destruction, but the violation of integrity itself is obtained as a result of normal stresses acting along the sliding lines.
