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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.

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.

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.

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.

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.