Within the framework of a model for the piezoelectric structure with a coating made of a functionally graded material with a piecewise-continuous variation of properties, the problem of propagation of horizontally polarized shear surface waves was investigated. The influence of the polarization vector orientation and the nature of the coating inhomogeneity on the propagation of surface waves in an "acoustically homogeneous" structure was studied. © 2019, Peter the Great St. Petersburg Polytechnic University

In the framework of the linearized theory of the propagation of thermoelastic waves, a dynamic mixed coupled problem on the oscillations of an inhomogeneous medium under the action of a thermal load oscillating on its surface is considered. The medium is a thermoelastic prestressed layer rigidly coupled with a thermoelastic prestressed half-space. At the boundary of the medium, two types of thermal conditions are considered: ideal thermal contact and heat insulation. Using operational calculus methods, the boundary value problem with mixed thermal boundary conditions is reduced to an integral equation of the first kind with respect to the unknown distribution function of the heat flux in the contact zone. We studied the distribution of the poles of the Green's function of a medium, taking into account the effect of initial strains and preheating. It is shown that thermal conditions at the interface between the medium have little effect on the distribution of the vertical displacement of the layer surface in the natural state. At the same time, the condition of thermal insulation between the layer and half-space allows to compensate for the effect of body pre-heating on the formation of the surface wave field.

A problem on surface sh-waves' propagation in a piezoelectric structure with a coating from a functionally graded material is considered. As a "base" material, a piezoelectric of 6mm class hexagonal syngony is used. The problem solution is based on the approach, which combines analytical methods of constructing the solution for homogeneous components and numerical methods of constructing the solution for inhomogeneous components of a heterogeneous structure. For problems with an electrically open or closed free surface, the transformation of the surface wave field, depending on the character of the change of the coating properties, is studied. Peculiarities of the surface waves' behaviour at different combinations of the coating and substructure materials are investigated. It is demonstrated, that by means of a special change of the coating properties it is possible to obtain the structure, on the surface of which Love waves or Bleustein-Gulyaev waves (BGW) are propagated, or the structure in which surface waves are absent in a definite frequency range.