卷 60, 编号 4 (2019)

The Maxwell equations for a composite two-component laminated material with a periodic structure in the field of a time-harmonic source acting along the layers are considered. Two-scale homogenization of the equations is performed with allowance for complex conductivity of interfacial layers and their thickness. The boundary-value problem for systems of differential equations with boundary conditions is reduced to a problem in a weakly variational formulation. Unique solvability of the problem is established. The case of low frequencies of interfacial currents of different intensities with allowance for the frequency-dependent wave length and skin layer length is analyzed. Macro-equations are derived, and effective material constants are determined, such as the dielectric permittivity, magnetic permeability, and electrical conductivities. Conditions at which the effective parameters depend on interfacial currents are described. It is found that the effective dielectric permittivity can be negative at specially chosen parameters of interfacial layers if it is determined on the basis of the effective wave number.

A thermodynamically equilibrium model is applied for simulating thermodynamic parameters of shock loading of both pure materials and mixtures of homogeneous and porous materials. The model includes a modified equation of state, which has only one fitting parameter determined on the basis of experimental data. The thermodynamic parameters of shock loading of copper and copper-based mixtures with porosities of 1–10 at pressures above 5 GPa are calculated. The results of these calculations are compared to available experimental data (Hugoniot adiabats, double compression by shock waves, and temperature estimates). The possibility of modeling the compression of the mixture as a whole and each component separately is demonstrated.

Starting of an air-breathing engine with fuel injection distributed along the combustion chamber is numerically simulated. Issues of principal importance are the presence of a compressed ar jet generating a throttling effect and preliminary deceleration of the flow to transonic velocities. Averaged Navier-Stokes equations closed by the SST, SST k-ω, or k-ε turbulence model are solved. Hydrogen and ethylene combustion is simulated by one reaction. The computations are performed for various values of the turbulent kinetic energy in the flow. A pulsed transonic regime of hydrogen and ethylene combustion is discovered.

The influence of the shape of the jet head on its impact on a wall covered with a thin liquid layer has been studied. The conditions characteristic of the impact of the jet arising on the surface of a cavitation bubble upon its collapse near a wall have been considered. It has been established that a change in the shape of the jet head can lead to a significant change in the size of the maximum loading area of the wetted wall and in the magnitude and pattern of loading. In particular, with an increase in the degree of sharpening of the jet head, the wall pressure decreases and its spatial distribution becomes more uniform. Dependences of the maximum pressure and integral wall load on the jet shape were obtained.

Three-dimensional deformation of two bubbles and bubbles in a cluster in an ideal incompressible liquid in an acoustic field is investigated using the boundary element method for potential flows. The dependence of the dynamics of two interacting bubbles on the frequency and amplitude of the acoustic field and the distance between bubbles is studied. The parameters of the acoustic field and the cluster for which jets are formed and the bubbles are deformed or remain spherical are determined. The behavior of two central bubbles in a structured cluster in an acoustic field with different frequency and amplitude is investigated as a function of the distance between bubbles in the cluster. A comparative analysis of the deformation of the investigated bubbles in the presence and absence of adjacent bubbles is performed.

In this paper, we study the nonstationary process of extracting material from a porous body simulated by a system of semi-infinite capillaries into a moving liquid in which the transfer rate of the material in the flow is a linear function of the cross-flow coordinate. The case where the liquid velocity at the interface becomes zero is considered. It is assumed that the diffusion in the flow is quasi-stationary. Analytical dependences at the interface between the porous material and the flow region are found for mass transfer characteristics of practical interest (concentration, diffusion flow, total diffusion flux, and the total yield of the target component extracted through the cross section of the porous body).

The stress state in the neighborhood of the common edge of a simply-supported composite wedge-shaped plate under transverse load has been studied. The materials of the constituent plates are cylindrically orthotropic. The problem is solved using the classical theory of anisotropic plates. Equations are derived for a hypersurface which, in the space of physical and geometric parameters, is the boundary of the region of parameters for which the neighborhood of the common edge of the composite plate is in a low-stress state (the stresses at the points of the common edge of the composite plate are limited).

Nonlinear elasticity model in current state variables is used to study the plane strain dynamics of an incompressible body, and a system of nonlinear displacement and pressure equations is obtained. In the absence of bulk forces and in the assumption of quadratic elastic potential, the resulting equations that describe plane waves, self-similar motions, and stress fields in these motions are solved and studied. It is shown that several solutions of a certain type are possible both in wave and self-similar cases.

Ballistic experiments, numerical simulations, and theoretical model investigations of the penetration performance of homogeneous and jacketed rods into a semi-infinite target are presented. The striking velocities vary between 0.9 and 3.3 km/s. The effects of the jacket material, striking velocity, and initial kinetic energy on the penetration performance and damage mechanisms are analyzed. The results show that jacketed rods provide better penetration performance than homogeneous rods with the same initial kinetic energy. For a fixed ratio of the jacket radius to the core radius, it is preferable to use a jacket material with a lower density and strength that can provide the lowest required flexural stiffness.

A simplified two-dimensional model of an overlap adhesive joint is proposed. The problem of a stress state of an adhesive joint, along the surfaces of which unadhered regions are located, is solved analytically under the assumption that the cross-sectional displacements of carrier layers vanish. The resulting solution is a functional series, with eigenfunctions being nonorthogonal. It is shown that the presence of unadhered regions may significantly increase stresses near the edge of the adherend.

The influence of the laser beam parameters (power, motion velocity, and focus position) on the characteristics of the track being formed (size, elemental composition, and microhardness) is studied. If the difference in the laser radiation absorption coefficients in the heat conduction and keyhole regimes is taken into account, then the track sizes can be determined by a unified dependence on the energy parameter. The effect of the laser beam on the chemical composition and microhardness of cermet (WC-NiCrBSi) tracks is studied. Regardless of the track formation regime, these parameters are determined by a dimensionless parameter, which describes the degree of dilution of chemical substances. It is found that a track with the maximum mass fraction of tungsten and the greatest value of microhardness is formed at small values of the dimensionless parameter, which corresponds to the heat conduction regime. The microhardness of the deposited cermet structure is observed to be 4–5 times higher than the microhardness of the substrate material.

Metal shields of various thickness made of various steels and used to protect the shells of explosion chambers from damage by debris and reduce the loads on the structural elements have been studied. Dependences of the equivalent stresses in the protective shields and shells of explosion chambers and the final size of the gap between the shields and the shell on wall thickness, steel grade, and initial gap size were obtained by numerical simulation. Examples of explosion chamber designs with protective shields are given.