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Results of experimental studies of diffusion combustion of hydrogen microjets performed in recent years are presented. Specific features of the hydrogen flow structure and hydrogen combustion are studied for various shapes of the nozzle, jet exhaustion velocity, and gravitation. Hydrogen combustion in mixtures with other gases and periodic actions on microjets (in the case considered, by external acoustic disturbances, is also considered.

In this study, the burst pressure of thin-walled pressure vessels made of carbon steel is numerically simulated and verified by experimental results. The effect of the length-to-diameter ratio on the burst pressure is analyzed. The numerical and experimental results are compared.

The combustion of 12 composite propellants of the following composition was studied: 60% ammonium perchlorate of the sieve fraction (180-250 μ m)-20% active combustible binder- 20% titanium of different particle size and nature (with spongy particles of size d =32-71 μ m and with rolled pseudospherical particles of size d = 71-500 μ m). Burning rates and agglomeration parameters of the metal component at pressures 0.35 MPa in nitrogen and 0.1 MPa in air were determined. It has been found that agglomerates with minimal sizes are formed when using titanium powders with particles of the smallest sizes.

A generalized mathematical model for the non-isothermal filtration of natural gas in a porous medium and a modified quasi-stationary model of gas hydrate formation (deposition) in pipelines were used to solve a conjugated problem for the case of joint operation of the “gas-bearing reservoir-well” system and predict the changes in temperature, pressure, gas moisture content, and well flow area. It is found that the presence of a thick permafrost layer accelerates hydrate formation inside the well. It is shown that when taking into account the salinity of formation waters, the duration of complete plugging of the well with hydrates increases

In this study, nonlinear forced vibrations of a bimorph piezoelectric nanobeam are investigated by using the nonlocal elasticity theory. This nanoactuator is modeled using the Euler-Bernoulli beam theory. The Hamilton principle is used to obtain the equations of motion. The derived equations are discretized by applying the mode shapes of multi-span beams as test functions in the Galerkin decomposition method. The discretized equations are then solved using the perturbation method. A parametric study is conducted to show the significance of size effects on the dynamic behavior of nanoactuators. The results show that an increase in the nonlocal parameter leads to a decrease in the fundamental natural frequency of the nanobeam and to an increase in the response amplitude.

By solving the plane problem of the mechanics of a rod strip having a fixed finite-length section on one of its front surfaces, it has been shown that when studying deformation processes with consideration of the compliance of the fixed section, it is necessary to take into account the change in the stress-strain state parameters and the mathematical models used for their description. This change occurs across the boundary between the unfixed and fixed sections. Within the framework of the classical Kirchhoff-Love model, it is impossible to take into account the compliance of the fixed section of the rod. However, within the framework of the simplest refined Timoshenko shear model, this is possible if the section is fixed only on one of the front surfaces. Exact analytical solutions of two simplest linear problems of static transverse bending of a flat rod with fixed sections of finite length on one of the front surfaces are found. One-dimensional finite elements for modeling unfixed sections of flat rods and sections on one of the front surfaces were constructed using the refined Timoshenko shear model. Numerical experiments were performed, showing the necessity of taking into account the change in the rod strain-stress parameters across the boundary between the fixed and unfixed sections.

The boron nitride nanosheet (BNNS), a graphene-like structure with excellent mechanical properties, is one of the most promising candidates for a reinforcement element to design innovative nanocomposites. Herein, we have investigated the BNNS, which serves for surface enhancement of the aluminum matrix via molecular dynamics simulations. The results show that the boron nitride nanosheet coating enlarges the critical yield strength, hardness, and modulus of elasticity. With an increase in the number of boron nitride layers, the strengthening effect is more significant. Meanwhile, a higher system temperature degrades the interfacial energy and weakens the mechanical properties of the BNNS/Al systems.

The problem of stability of cylindrical shells made of composite material, taking into account momentum and nonlinearity of their subcritical stress-strain state. Geometrically non-linear the stability problem is solved by finite element methods and linearization of Newton -Kantorovich. Critical loads are determined in the process of solving a nonlinear problem using Sylvester's criterion. Hypothesized Timoshenko finite elements of composite cylindrical shells natural curvature, in the approximation of displacements of which in explicit form, rigid displacements are highlighted, which significantly affects solution convergence. The stability of the circular cylindrical shell made of polymer composite material, under combined loading by torsional and bending moments and internal pressure. Studied the influence of the laying method monolayers, non-linearity of deformation, internal pressure on critical loads at which buckling occurs shells

This paper proposes a model of static transverse elastic deformations of a magnetic gel sample shaped as a strongly elongated cylinder, which is under the action of a transverse uniform magnetic field and the force of gravity. Theoretical results obtained within the framework of the proposed model are in qualitative agreement with the results of laboratory experiments

The flows of incompressible media with tensor-linear defining relations, including an arbitrary scalar nonlinearity in the form of a monotonically increasing hardening function. There are two types of media: without yield strength (nonlinear-viscous liquids) and with a yield strength (viscoplastic bodies), and the media of the second type are interpreted as finite perturbations of the corresponding media the first type. On the example of the problem of one-dimensional stationary shear flow in round pipe shows the influence of the method of perturbing the limit fluidity at maximum speed and flow. The values of these quantities depend on the sign of the second derivative of the hardening function, i.e. on what material the unperturbed medium is: pseudoplastic or hardening