Home – Home – Jornals – Journal of Applied Mechanics and Technical Physics 2026 number 2

The behavior of a three-component electrolyte in a microdevice utilizing a spherical ion-selective granule under an applied electric field and a pressure difference is investigated. In practical applications, one of the electrolyte components corresponds to charged analyte particles present at an initially low concentration. It is shown that the analyte concentration can be increased in the wake of the granule, and the degree of concentration enhancement is independent of the initial concentration. The physical mechanism of this phenomenon is described. This paper also presents the parameter values-such as the potential difference, pressure difference, and the characteristics of the electrolyte and the granule-for which this enhancement is achievable.

Changes in the properties of a DC-excited gas-discharge plasma in uniform weak longitudinal magnetic fields are analyzed. The state and behavior of such a system in a weak magnetic field can be studied using the reaction-diffusion equation, which describes the ionization-recombination equilibrium in the plasma, together with modern concepts of ambipolar diffusion. It is shown that, in the presence of an external magnetic field, the transverse diffusion coefficient decreases, the coherence of emerging plasma states in the system is disrupted, noise or turbulence arises in diffusive and stratified regimes (including contracted ones), and the striation period increases. Complete destruction of the spatiotemporal structure of a striation occurs when the magnetic field strength exceeds a critical value. A similar effect is also achieved by increasing the working gas pressure. The presented findings allow all the above-mentioned behavioral features of the ionized gas to be interpreted as different manifestations of an integrated plasma-field system.

Some experimental results on the penetration of polyconical penetrators made of EP637 steel into M400 concrete blocks and sandy soil are presented. The critical velocity is determined through successive iterations over a range of impact velocities characteristic of the transition from an intact penetrator (defined as a reduction in model length of less than 5%, excluding cavitator blunting) to a failed penetrator (defined as a length reduction exceeding 5% or a breach of penetrator integrity). The critical impact velocity above which penetrator failure occurs is identified.

The amplification of a shock wave pulse transmitted through a sand layer is investigated as a function of layer thickness. It is shown that, as the sand layer thickness becomes somewhat higher, the amplitude of the probing pulse first increases and then decreases. Pressure peaks form almost simultaneously throughout the entire sand layer.

Results of an experimental study on the deformation and failure of nature-inspired cellular structures under compression at high strain rates are presented. Tests are conducted on specimens with the Schwarz primitive geometry, modeled with different volume fractions (ϕ), as well as on solid specimens. The specimens are fabricated from polylactide polymer using 3D printing. An increase in compressive strength and elastic modulus is observed with increasing strain rate at constant ϕ. Specific energy absorption values are determined for the cellular structures studied. The Gibson-Ashby relationship for cellular structures is confirmed to hold under high-strain-rate loading.

One-dimensional unsteady flows of an incompressible non-Newtonian viscoelastic fluid between parallel plates are considered within the framework of the Johnson-Segalman model with multiple relaxation times. A distinctive feature of the model is its hyperbolicity over a wide range of flow parameters. A general form of the model with n relaxation times (modes) is obtained, and a change of variables is introduced that allows the governing equations to be written in conservative (divergent) form. A series of unsteady flow simulations in various regimes is performed, demonstrating the occurrence of shear banding with increasing mean flow velocity. The dependence of the wall shear stress on the shear rate is obtained, as well as the dependence of the flow rate on the pressure gradient, for plane steady Couette and Poiseuille flows, respectively. The resulting diagrams are validated by comparison with a range of experimental data. The structure of steady-state solutions exhibiting shear banding, obtained as the numerical limit of unsteady solutions, is investigated. A criterion is formulated for selecting steady-state solutions that are asymptotically realized in numerical unsteady calculations. The phenomenon of hysteresis under cyclic variation of the flow velocity is analyzed.

Integration in Lagrangian variables is performed for a submodel describing steady-state motions of an ideal gas with constant pressure in the flow region. A general solution is obtained for the invariant submodel of steady-state rotational isobaric motions. Examples of helical gas motions with constant pressure are considered.

A numerical study is performed to investigate the influence of vibrational excitation and relaxation of sulfur hexafluoride (SF₆) molecules on the gas-dynamic structure and stability of high-speed microjets issuing from axisymmetric sonic micronozzles with diameters ranging from 10 to 110 μm. Direct numerical simulation of the gas flow is conducted by solving the unsteady three-dimensional Navier-Stokes equations using a two-temperature model for relaxing flows. The study is carried out over a wide range of Reynolds numbers determined by the micronozzle diameter. The influence of vibrational relaxation of gas molecules on the mode composition and spectral characteristics of disturbances, as well as on the length of the laminar region of the microjets, is observed.

Results of a numerical simulation and flow stability analysis of the boundary layer on a flat plate with surface microrelief in the form of long slots (grooves) oriented at different angles relative to the freestream flow at Mach number M = 2 are presented. Slots with a depth-based Reynolds number Re_h ≈ 1000 and a width small compared to the instability wavelength are considered. Using numerical simulation, the flow characteristics around the plate with inclined slots are determined, and the development of time-localized disturbances is studied. A flow stability analysis is performed within the framework of linear stability theory using averaged boundary-layer profiles. The computational results show that the presence of inclined slots leads to the emergence of crossflow in the boundary layer, which causes an increase in disturbance growth rates. The obtained data are in good agreement with experimental observations and explain the boundary-layer destabilization effect caused by inclined slots.

Предложен эффективный способ учета граничных условий методом решеточных уравнений Больцмана, основанный на трассировке лучей. Данный подход обеспечивает высокую точность расчетов для сложных геометрических форм с использованием только дискретных поверхностных сеток, что исключает необходимость аналитического описания кривизны. Разработан надежный алгоритм геометрического пересечения, в котором тесты луч - отрезок (2D) и луч - плоскость (3D) позволяют точно локализовать граничные точки. Алгоритм не требует предварительной обработки и сохраняет второй порядок точности за счет применения классической схемы отскока. Верификация на задачах обтекания двумерных цилиндров (Re =100), аэродинамического профиля NACA0012 (Re = 500) и трехмерных сфер показала, что полученные результаты хорошо согласуются (погрешность определения коэффициента сопротивления при использовании сеток с 64-128 вершинами не превышает 3 %; отклонение от высокоточных эталонных данных составляет менее 10 %). Простота реализации, точность и полная совместимость с CAD-моделями делают предложенный подход перспективным для применения метода решеточных уравнений Больцмана в задачах автомобилестроения, аэрокосмической отрасли и энергетики Полный текст статьи на английском языке публикуется в англоязычной версии журнала ПМТФ (J. Appl. Mech. Tech. Phys. 2026. V. 67, N 2).

A pseudo-direct numerical simulation of turbulent natural convection in a closed, nonuniformly heated square cavity filled with air is performed. The velocity components are calculated using the lattice Boltzmann method with high-order regularization. Thermodynamic characteristics are analyzed by solving the macroscopic energy equation using a fourth-order Runge-Kutta finite-difference scheme. The developed hybrid algorithm, which mimics the direct numerical simulation approach, is tested on benchmark problems of turbulent natural convection. Numerical simulations are carried out over a Rayleigh number range of 10¹⁰ ≤ R ≤ 10¹¹. It is found that, as R increases, the intensity of thermal plume generation on the isothermal walls becomes greater and the region of turbulent vortex formation expands. Stagnation zones of the heat transfer fluid are identified near the horizontal walls. The distribution of second-order statistics, with the exception of temperature variance, is shown to depend on the thermal plume configuration.

A solution to the problem of the pressure field in an oil and gas reservoir with a hydraulic fracture connecting an injection well and a production well is obtained. The solution is constructed in the Laplace-Carson transform space using an asymptotic method. Analytical expressions for the pressure field in the fracture are derived in the quasi-stationary approximation. An approximate formula for calculating the pressure field in a hydraulic fracture is proposed. Computational experiments are performed using numerical inversion algorithms and the obtained analytical expressions. Spatiotemporal pressure distributions are constructed for realistic values of reservoir and fracture parameters. Based on an analysis of the computational results, the patterns of pressure field formation in a reservoir with a hydraulic fracture are refined. A comparison of the numerical calculations with the analytical relationships shows that the proposed analytical formula provides accuracy sufficient for practical purposes over a time period comparable to the production lifetime of real oil and gas fields.

Results of experiments on the fabrication of a composite material based on PTS-1 titanium with a TiN reinforcing phase at volume fractions of 4, 8, 12, and 21% by hot pressing are presented. A powder mixture of titanium and titanium nitride, mechanically processed in a high-energy planetary ball mill, is sintered at temperatures of 1200, 1300, and 1400°C. The sintered samples are shown to contain primary (α-Ti and β-Ti) and secondary phases (δ-TiN and ε-Ti₂N). With increasing titanium nitride concentration, a polymorphic transformation (β ↔ α) occurs, forming the α-Ti-TiN eutectoid. Elevating the sintering temperature is found to increase the grain size of the β-Ti phase by 250%. Owing to the high titanium nitride concentration, the composite structure is transformed, leading to an increase in relative density to 99%, an improvement in material hardness by 97%, and an increase in elastic modulus by 63%.

Results of experimental investigations into the effect of impact energy on the residual compressive strength of high-strength laminated carbon fiber reinforced polymer specimens are presented. To study the influence of residual stress levels induced by impact on the residual strength of the specimens, additional measurements are performed using electronic speckle pattern interferometry in conjunction with the drilling of small probe holes. Residual stress values are determined in the mid-plane of the specimens at the boundaries of the impacted zones. The scatter in the experimental data, arising from distributed damage within the material microstructure, prevents establishing a correlation between residual stresses after impact with energies of 0-110 J and the residual strength of the specimens.

The nonlocal theory of microstructural deformation of thin plates is applied to derive an equilibrium equation for a thin isotropic nanoplate along with the corresponding boundary conditions. An approach to constructing a solution to this equation for a rectangular nanoplate with simply supported edges is proposed, employing Chebyshev polynomials of the first kind and the collocation method. The deflection of the nanoplate midplane and the bending moments are analyzed as functions of a nonlocal nanoscale parameter.

The mechanical properties of a new composite-diamane-reinforced copper-are investigated using molecular dynamics simulations. Young's modulus and tensile strength of the copper-diamane composite are determined to be 117 GPa and 16.4 GPa, respectively. These values can be greater provided that the number of diamane layers in the composite is increased.

An experimental study of hydraulic fracturing of thick-walled concrete cylinders with a central hole is conducted using a high-pressure fluid test setup. The cylinders are made of sand-based concrete with GTs 50 alumina cement. Estimates of the ultimate pressure obtained using local and nonlocal failure criteria are compared with experimental data. Satisfactory agreement between the calculated ultimate loads and the experimental failure data under nonuniform stress conditions is shown to be achieved with nonlocal failure criteria.

An exact solution to the two-dimensional Wiener-Hopf integral equation is obtained for the first time. This solution is used to solve mixed problems in acute-angled wedge-shaped domains. Mixed problems are considered for an arbitrary multilayer anisotropic composite. The block element method is employed in combination with topological and factorization approaches. The constructed solution has an integral representation that can be utilized in standard software packages for evaluating integrals in the study of anisotropic composites. The solution contains singular sets where it becomes infinite, which complicates the direct numerical solution of such mixed problems. An exact solution to the two-dimensional Wiener-Hopf integral equation is equivalent to solving the mixed problem in a wedge-shaped domain with an angle of 90°. This result may be used together with topological methods to solve these equations in arbitrary acute-angled wedge-shaped domains. A theory of contact problems for wedge-shaped punches with an acute angle is developed.

The propagation of a rectilinear crack at the interface of dissimilar materials is investigated. A two-parameter (dual) elastic-plastic failure criterion for mixed-type cracks is proposed. This criterion includes a deformation criterion formulated at the tip of the initial crack and a force criterion formulated at the tip of a fictitious crack. The lengths of the initial and fictitious cracks differ by an amount equal to the length of the process zone. Because the crack path at the interface between materials is curved, the fracture angle is determined using the maximum tangential stress criterion based on the asymptotic expansion of the stress field in the vicinity of the crack tip, taking into account non-singular terms. A modified Leonov-Panasyuk-Dugdale model of the end zone of a sharp internal crack is used to describe the process zone. The parameters entering the resulting analytical model are analyzed. The dimensionless geometric parameters of the structure are determined numerically using the finite element method. A system of two nonlinear equations is obtained for the critical length of the process zone and the critical load under mixed-type (complex) stress state conditions. The shape and dimensions of the process zone in the vicinity of the crack tip in a nonlinear elastic material are determined using the von Mises criterion.

A VT-6-10% B₄C cetmet composite is produced using direct laser deposition (laser additive manufacturing). The effect of thermal post-treatment on the microstructure and properties of this composite is investigated. After heat treatment, the (α+γ) matrix structure is found to transform into an (α+β) structure, β-Ti is stabilized, the concentration of secondary phases (TiB, TiC_1-x, TiB₂, V₂B₃) increases, and the α₂-Ti₃Al intermetallic compound is formed. Thermal post-treatment leads to an increase in microhardness (up to HV0.3 = 651) and improved wear resistance (wear volume decreases by 7%, and the friction coefficient by 0.08). These results confirm the effectiveness of heat treatment for optimizing the structure and enhancing the wear resistance of additively manufactured titanium matrix composites.

Approaches to the topological optimization of lattice composite structures aimed at improving their weight efficiency for use in rocket and space technology are investigated. Traditional filament winding methods and advanced technologies such as continuous-fiber 3D printing are considered; these enable the creation of micro-lattice structures with thin ribs and biomimetic properties. The application of the SIMP method in continuum and discrete models is demonstrated for a cylindrical spacecraft body shell. A comparison of various lattice structure designs shows that the weight of these structures is 18.5% lower when using the SIMP method compared to the traditional approach.

Results of the conceptual development of a vacuum aerodynamic facility based on the vacuum system of the AT-303 wind tunnel at the ITAM SB RAS are presented. The layout, geometry, design features, and advantages of the proposed facility are described. Its operating parameters and performance characteristics are evaluated.