Elastic strains on the interfaces with the finite and infinitesimal dimensions

The problem of elastic waves propagation through the interfaces which are considered as a structure elements of inhomogeneous solid is investigated. An infinitesimal thin layer is the usual model of boundary in the classical mechanics. The considered interfaces are characterized by dimensions and the physical-mechanical properties that are different from ones of the contacting solids. The models of layered and block media are used for these interfaces description. Analytical expressions for the Fresnel coefficients allowing us to find the strain components on the interface are derived. The dependences of Fresnel coefficients and strain amplitudes as functions of interface thickness and elastic properties of the contacting solids are calculated at the normal incidence of P and SV waves on the boundary. Strains features on the interface are analyzed in the frame of two considered models.