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The fabrication of Al-metallic glass (Fe₆₆Cr₁₀Nb₅B₁₉) composites with low residual porosity and varying component concentrations is presented. During sintering, no interfacial interactions between the composite components are observed. The hardness and thermal conductivity of the Al-metallic glass composites are experimentally determined. The experimental data are compared with values calculated using the rule of mixtures. The measured thermal conductivity of composites containing 20 and 80 vol.% metallic glass closely matches values predicted by models for parallel and series phase connectivity, respectively. The hardness values for these composites are consistent with those calculated using the Reuss and Voigt models.

A numerical study of the effect of a perturbation generated by a vortex-generator fin on the local flow structure and turbulence of a bubbly flow in a planar channel behind a backward-facing step is performed. An Eulerian approach is employed to describe the flow dynamics and heat and mass transfer in both the carrier gas and dispersed phases. The problem is solved using the Reynolds-averaged Navier-Stokes equations, modified to account for the presence of bubbles. The influence of air bubble concentration, initial bubble diameter, and vortex generator height on the turbulent flow structure and the length of the separation region is investigated. The presence of the vortex-generator fin induces a significant (twofold) increase in the turbulence level in both single-phase and two-phase bubbly separated flows. The fin is found to exert a substantial effect on turbulence in the separated flow, with the turbulence level increasing by up to 60%. The addition of bubbles reduces the recirculation zone length (by 60% for ∆/H = 1/3).

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.

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.

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.

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.