Journal of Applied Mechanics and Technical Physics最新文献

The pressure field problem in an oil and gas reservoir with a hydraulic fracture connecting an injection well and a production well has been solved. The solution is developed in the Laplace–Carson image space using an asymptotic method. Analytical expressions for the pressure field in the fracture are obtained in a quasi-steady-state approximation. An approximate formula for calculating the fracture pressure field is proposed. Computational experiments were performed using numerical inversion algorithms and the derived analytical expressions. Spatiotemporal pressure distributions are plotted for realistic reservoir and fracture parameters. Based on an analysis of the calculation results, the regularities of pressure field formation in a reservoir with a hydraulic fracture are refined. A comparison of numerical calculations and analytical dependencies shows that the proposed analytical formula is sufficiently accurate for practical applications within a time frame comparable to the productive life of real oil and gas fields.

An equilibrium equation for a thin isotropic nanoplate with boundary conditions is obtained using the nonlocal theory of microstructural deformation of thin plates. An approach is proposed to construct a solution to this equation for a rectangular nanoplate hinged at the ends using 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.

A VT-6–10% B₄C metal–ceramic composite was fabricated using direct laser deposition. The effect of postheat treatment on the microstructure and properties of the composite was investigated. It was found that after heat treatment, the ((alpha + gamma )) structure of the matrix is transformed to the ((alpha + beta )) structure, (beta )-Ti stabilizes, the concentration of secondary phases (TiB, TiC(_{{1 - x}}), TiB₂, V₂B₃) increases, and an ({{alpha }_{2}})-Ti₃Al intermetallic compound is formed. Postheat treatment leads to an increase in microhardness (to ({text{H}}{{{text{V}}}_{{0.3}}} = 651)) and wear resistance (the wear volume decreases by 7%, and the friction coefficient by 0.08). The results of the study confirm the effectiveness of the heat treatment of additively manufactured titanium matrix composites for optimizing their structure and increasing wear resistance.

This paper presents experimental results on the effect of impact energy on the residual compressive strength of high-endurance laminated carbon fiber composite specimens. To investigate how the level of impact-induced residual stresses affects the residual strength of the specimens, additional studies are conducted using electronic speckle interferometry combined with the probe hole drilling method. Residual stress values are determined in the midplane of the specimens at the impact zone boundaries. Scatter in the experimental data, caused by dispersed damage within the material structure, prevented establishing a correlation between residual stresses after an impact with an energy of 0–110 J and the residual strength of the specimens.

A numerical study was performed to investigate the effect of vibrational excitation and relaxation of sulfur hexafluoride (SF₆) molecules on the gasdynamic structure and stability of high-speed microjets exhausting from axisymmetric sonic micronozzles with a diameter of 10–110 µm. Direct numerical simulation of gas flow was based on solving three-dimensional unsteady Navier–Stokes equations using a two-temperature model of relaxation flows. The studies were conducted over a wide range of Reynolds numbers determined by the diameter of the micronozzles. The vibrational relaxation of gas molecules was found to influence the modal composition and spectral characteristics of perturbations, as well as the length of the laminar region of microjets.

A pseudodirect numerical simulation of turbulent natural convection in a nonuniformly heated closed square cavity filled with air is performed. The velocity vector components are calculated using the high-order lattice Boltzmann method. The analysis of thermodynamic characteristics is carried out through a finite-difference solution of the macroscopic energy equation using a fourth-order Runge–Kutta scheme. The developed hybrid algorithm simulating the direct numerical simulation method is tested on benchmark problems of turbulent natural convection. Numerical studies are performed for Rayleigh numbers ({{10}^{{10}}} leqslant {text{R}} leqslant {{10}^{{11}}}). It is found that increasing R increases the intensity of thermal plume generation on isothermal walls and the region of turbulent vortex formation. Stagnation zones of the coolant were identified in the vicinity of the horizontal walls. It is shown that the distribution of second-order statistics, except for temperature variance, depends on the thermal plume configuration.

The paper presents experimental results for the penetration of polyconical penetrators made of EP637 steel into M400 concrete blocks and sandy soil. The critical velocity is determined by successive iterations in the range of impact velocities characteristic of the transition of the penetrator from an undamaged state (reduction in model length by less than 5% neglecting cavitator blunting) to failure (reduction in length by more than 5% or structural failure). The critical impact velocity above which penetrator failure occurs is determined.

Approaches to the topology optimization of composite lattice structures are explored to improve their weight efficiency when used in rocket and space technology. Traditional winding methods and promising technologies, such as continuous fiber 3D printing are considered, which enable the design of microlattice structures with thin ribs and biomimetic properties. The application of the SIMP method for continuum and discrete models is demonstrated for a spacecraft cylinder. A comparison of various lattice structures shows that when using the SIMP method, the mass of these structures is 18.5% less than when using the traditional approach.

This paper presents the results of an experimental study of the deformation and fracture of nature-inspired cellular structures under high-velocity compression. Tests are conducted on specimens with Schwarz primitive structure with various volume fractions, as well as solid specimens. The specimens are fabricated from a polymer (polylactide) using 3D printing. An increase in ultimate strength and elastic modulus is observed with increasing deformation velocity at a constant volume fraction (varphi ). Specific energy absorption values are determined for the cellular structures studied. It is confirmed that the Gibson–Ashby relation is valid for cellular structures under high-velocity loading conditions.