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Uniaxial tension and three-point bending tests were performed for polymer composite samples made of Crystal 85-5 epoxy resin modified with MHG-4E (average particle size 5-15 µ m) and FV-530D (average particle size 25 µ m) photoluminescent powders. The dependence of the elastic modulus on the filler concentration was obtained. The photoluminescent properties of the resulting composites were studied. The dependence of the has been established afterglow intensity on the filler content in the composite was determined.

A problem of mathematical modeling of a section of a fuel element (fuel element), including a number of fuel pellets and a shell fragment, in an axisymmetric formulation is considered. It is assumed that the shell is a thermoelastic-plastic body, and the tablet is a thermoelastic body, taking into account the cracking of the material. To numerically simulate the thermal and mechanical contact of tablets with each other and with the shell, various variants of the domain decomposition method were used. The results of calculations are presented, which describe the achievement of the nominal power of a section containing 10 pellets, the influence of cracking of pellets on the thermomechanical state of the fuel rod is assessed.

A new technique has been proposed and implemented that allows for time-frequency analysis of data obtained using the PIV method, taking into account the readings of the surface sensor of a hot-wire anemometer. The technique is based on calculating the correlation coefficients between the data obtained by the PIV method and the data from the hot-wire anemometer sensor, which were previously filtered in a given frequency range. Using this approach makes it possible to obtain data on the unsteady characteristics of flows throughout the entire measurement range in the frequency range, the boundaries of which extend beyond the boundaries of the frequency range of the PIV method. Using the proposed method, a study of non-stationary processes in the region of interaction of a shock wave with a boundary layer at the Mach number M = 1.43 was carried out.

The feasibility of joining of the 6061 aluminum alloy to double-layer oxygen-free copper (TU1) by laser welding technology is reported. The weld formation and microstructure of the Cu-Cu-Al welding joint for various technological parameters are analyzed. The assessment of experimental results is based on macro- and microstructure observations of the weld using the AxioObserver D1M and Gemini SEM 300 scanning electron microscopes. The width and depth of the molten pool and the mechanical properties of the Cu-Cu-Al welding joint are tested by the Eagle-MD semi-automatic image measuring instrument and the YH-9002 computerized tension and compression machine. Among the nine tested samples, the most favorable weld parameters values are obtained with a laser power at 1600 W and a welding speed of 90 mm/s. The aluminum side area has a richer metallographic structure than the copper side area after welding.

Various crossovers of the effective permeability of certain analytically treatable models of the Darcy flow in porous media are studied. They account for the critical behavior as well for the regimes with low concentrations of obstacles. Transverse permeability of spatially periodic arrays of impenetrable cylinders is found in an analytical form and accounts for various asymptotic regimes. Longitudinal permeability for a square array of cylinders is found as well. Transverse flows past hexagonal and square arrays of cylinders are also considered based on expansions for small concentrations and lubrication approximation for high concentrations of cylinders. Three-dimensional periodic arrays of spherical obstacles are considered as well. Formulas for the drag force exerted by various lattices of obstacles are derived from low-concentration expansions. The Stokes flow through two-dimensional and three-dimensional channels enclosed by two wavy walls is studied by means of expansions for small waviness amplitudes. Compact formulas for permeability are derived in the form of factor approximants for arbitrary values of waviness. Various power laws are accounted for in the regime of large waviness parameters, as well as the existing expansions at small amplitudes.

The classical time-harmonic plane strain problem for a fluid-loaded cylindrical elastic shell is revisited. The results of the low-frequency asymptotic analysis, including explicit formulae for eigenfrequencies, are presented. A refined version of the semi-membrane shell theory is formulated. It is shown that the shell inertia does not affect significantly the lowest eigenfrequencies. It is also demonstrated that the ring stress component has a parabolic linear variation.

The effective thermal characteristics of composite materials used in the theory of solid-state cooling are studied. Two classes of composites are considered: layered structures consisting of a large number of nano-sized layers and two-phase granular composites. It is assumed that the boundaries between media are imperfect. At these boundaries, the temperature experiences a Kapitsa jump. The effective characteristics of layered structures are obtained using the matrix averaging method. The Averaging of the characteristics of granular composites is based on the Bruggeman approach. Formulas taking into account the influence of the Kapitsa interlayer resistance on the average thermal characteristics of the structure are obtained. Expressions for average values of heat sources are derived.

A small-sized elastic isotropic strip-beam loaded with variable body and surface forces is considered. On the front surfaces, surface shear stress and inertia are taken into account within the framework of the Gurtin-Murdoch surface elasticity theory. Asymptotically correct equations describing the long-wavelength bending deformation of micro/nano-beams taking into account shears and surface effects are derived by asymptotic integration of the two-dimensional elasticity equations over the strip thickness. The influence of surface stress and inertia on the lower spectrum of natural vibrations of metal micro/nano-beams is studied. It has been shown that surface inertia has the same effect on the spectrum of natural frequencies of bending vibrations as surface stresses.

The process of buckling of the von Mises truss in the case of material instability, i.e., with allowance for the loss of ellipticity, is considered. Strain diagrams are constructed. Results that allow one to study buckling of thin-walled structures (arcs or shells) made of materials for which the loss of ellipticity of equilibrium equations is possible are obtained.

The problems of indentation of a rigid stamp of finite dimensions with a surface microrelief into a multilayer elastic strip are considered. Boundary variational formulations of problems using the Poincare-Steklov operator, which maps contact stresses into displacements, are presented. When approximating this operator, a discrete Fourier transform was used; to calculate the transfer function, an algorithm based on the variational formulation of the boundary value problem for displacement transformants was used. As a result of approximation of the original contact problem, a quadratic programming problem with constraints in the form of equalities and inequalities was obtained, for the numerical solution of which an algorithm based on the conjugate gradient method was used. A number of patterns of contact interaction have been established.