plasticity, ideal, absolute, elasticity, stress, fluidity limit, coefficient, intensity, static definability.

The article is devoted to the problem of diffraction of the ultimate plastic wave on the convex surface. The stress state satisfies the condition Mises plasticity behind the flat longitudinal wave. The spherical surface was chosen as obstacle. The intensity of diffractional wave was calculated due to the «transfer» equation along the curved beams, that is forming sphere: δw cδt − Ωw = F. In order to solve Cauchy problem we must know the geometric characteristics of the diffractional wave, the first and second main curvatures. Due to that we can calculate the average curvature Ω(ε, t). The geometric characteristics of the diffractional wave are the functions of the time t and parameter ε. Parameter ε characterizes the position of the current point on the diffractional wave. The parameter ε adopted for the surface coordinate of this point in the plane ϕ = const. The second coordinate ϕ is arbitrary due to the exisymmetric problem. It is shown that intensity of diffractional wave exponentionally decreases due to its distribution along the meridian of the sphere and due to geometric attenuation deployment diffractional front. It is considered the calculation of the stress state in the case of the fall of the longitudinal wave in a ball of elastic material. The calculations are performed in the neighborhood of the forefront of the diffractional wave by the ray method. It is shown that longitudinal diffractional wave causes only longitudinal wave in the material of the obstacle. Its intensity differents from the intensity of the diffractional wave by coefficient, which depends on the ratio of the densities and on the ratio elastic parameters of the material elastic medium and material obstacle. The intensity of the diffractional wave in the space and in the material of the sphere decays with time at the place of contact of the diffractional and generated waves.

1. Bykova Ksenya Igorevna Postgraduate Student, Department of the theoretical and apply mechanics, Voronezh State University, Voronezh

2. Verveyko Nikolay Dmitrievich Doctor of Technical Science, Professor of the Department of the theoretical and apply mechanics, Voronezh State University, Voronezh