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A technique was proposed and an experimental study of the dynamic characteristics of three-phase soils was carried out. The regularities of changes in the main indicators of the deformation properties of samples of quasi-thixotropic moraine soils, which are manifested under technogenic vibrodynamic loads, have been established. It has been shown experimentally that the accelerations arising in the soil change sharply at the beginning of the experiment. These accelerations are different from the accelerations transmitted from the vibrating table. Within a certain pressure interval, the modulus of total deformations of quasi-thixotropic moraine soils under dynamic loading is 4.7 times less than that under static loading. The obtained numerical value of the modulus of elastic deformations under dynamic loading conditions is comparable to the value of the modulus of restoring elastic deformation under static loading. As an example, the influence of the mechanical characteristics of the soil on the frequencies of natural vibrations of a three-layer beam was investigated. [ABSTRACT FROM AUTHOR]

The problem of thin-layered deformations lying on a massive base under conditions of uniform heating is considered. For calculations, a micro-dilatation model of thermoelasticity of porous structures is used taking into account the defectiveness of boundaries. Under the assumption of plane deformation, a closed formulation of the problem under consideration is obtained, which admits an analytical solution. A numerical and analytical solution of the problem is represented, which changes within the framework of the considered statement only over the thickness of the layers. Using the example of a structure, consisting of a graphite substrate and a ceramic coating, an analysis of the influence of non-classical model parameters on stresses and strains in the layers of the structure is carried out. It is shown that if compressive stresses act in the coating plane at ideal contact of the layers, then when defects appear at the interface between the layers, dangerous tensile normal stresses can arise, which can lead to destruction of the coating. [ABSTRACT FROM AUTHOR]

Graphite and graphite-containing materials having a high degree of anisotropy are widely used for thermal protection. When modelling the thermal state of products, made of anisotropic materials, it is necessary to take into account many factors and the presence of mixed derivatives significantly complicates the solution for the problems of anisotropic thermal conductivity. This paper examines the thermal state of a pyrolytic graphite plate in the presence of heat transfer at its free boundaries on the basis of an analytical solution of the second initial-boundary value problem of anisotropic thermal conductivity with general anisotropy (off-diagonal components of the thermal conductivity tensor are not equal to zero). This solution makes it possible to analyse qualitatively and quantitatively the thermal state of bodies, made of materials with a high degree of anisotropy, in particular, pyrolytic graphite. The analysis of the influence of the thermal conductivity tensor principal axes orientation on the temperature fields of plate corners has been carried out, as well as the degree of anisotropy -- the ratio of the maximal principal component of the thermal conductivity tensor to the minimum. It is shown that even a thin layer of pyrolytic graphite makes it possible to control heat fluxes only due to the orientation of the main axes of the thermal conductivity tensor during high-intensity heating of various structural elements. [ABSTRACT FROM AUTHOR]

An inverse unsteady boundary value problem of a plane oblique pressure wave diffraction on a convex surface in the form of a parabolic cylinder is considered. At the same time, approximate models of the interaction of a wave with a rigid obstacle in a liquid are constructed, based on the hypothesis of a thin layer, which makes it possible to obtain fundamental solutions in a closed-form. To obtain an analytical solution for the direct problem, a non-stationary diffraction problem for an acoustic medium is solved using the transient function of the obstacle surface influence. The operational method is used. In the inverse problem, the angle of the front of the oblique wave is determined based on the measured pressure in the reflected and incident waves on the body surface using the least squares method. Among the results of the study, an algorithm was proposed for solving the inverse boundary value problem of diffraction of a plane oblique pressure wave on a rigid obstacle in the form of a parabolic cylinder by determining the angle of the oblique wave front. [ABSTRACT FROM AUTHOR]

Most recently, the demand for using layered thin-walled structural elements in aircraft-, rocket-, machine-, instrument-, and shipbuilding, production and transportation of energy carriers has increased significantly. This leads to the development of mathematical models and methods for their calculation for various types of loads. The setting and solution of the boundary value problem of axisymmetric bending of an asymmetric elastic circular three-layer plate with a compressible filler is represented. Kirchhoff-Love hypotheses are accepted for thin bearing layers. In a relatively thick, compressible aggregate, Timoshenko hypothesis is valid, while the normal remains rectilinear, but it rotates through some additional angle, the radial displacements and deflection vary linearly in thickness. Differential equations of equilibrium in efforts are obtained using the variational Lagrange method. The statement of the boundary value problem in displacements is given in a cylindrical coordinate system. An analytical solution was obtained in the case of an aggregate, which does not resist shear and compression. A numerical analysis of displacements and deformations in the plate has been carried out. [ABSTRACT FROM AUTHOR]