Russian Physics Journal最新文献

Within the framework of the Lagrangian approach, the numerical finite element method is employed to study both normal and oblique high-speed and hypervelocity impacts (HVIs) of an aluminum particle simulating space debris on solid aluminum, steel mesh (discrete), and two-layer metal-ceramic screens consisting of an upper layer made of ceramic B₄C and a lower layer composed of either monolithic aluminum or a steel mesh. All screen types had identical surface densities. Simulations were conducted using the authors’ proprietary three-dimensional software package EFES ensuring mass conservation under failure conditions. The implemented failure algorithm enables accurate description of material fragmentation and formation of new contact boundaries without distortion of the computational grid. Evaluation of the effectiveness of protective properties for various protective screens was carried out within a velocity range spanning from 3 to 10 km/s.

When drilling into rock containing a productive hydrocarbon reservoir, it is often necessary to select the appropriate drill bit diameter for the cutting tool. In this paper, a dynamic finite-element method is used to simulate drilling of carbonated core containing healed fractures. The elastic-brittle model is used. An analysis of the results shows that for all the considered sets of cores with healed fractures, the ratio of the number of fractured elements to the total number of fractured elements in 80 mm diameter cores exceeds that for 100 mm diameter cores. Therefore, drilling with a 100 mm diameter drill bit will reduce the probability of core damage compared to an 80 mm diameter drill bit.

The study presents a comparative analysis of the microstructure and phase composition of a Ti4Al3V alloy fabricated by wire electron beam additive manufacturing, in the as-quenched and normalized states at 1050 °C. Quenching leads to the formation of martensitic α′ phase with a high density of crystallographic defects, resulting in increased strength and microhardness. Normalization produces an equilibrium α + β microstructure characterized by coarse α‑phase plates and an increased volume fraction of β‑phase, which slightly reduces microhardness. XRD analysis after quenching revealed shifts in the diffraction peaks for an α phase, attributed to the dissolution of aluminum and vanadium into a β-matrix and the development of internal residual stresses. Thus, the choice of heat treatment regime for WEBAM-fabricated Ti4Al3V is strategic and depends on the intended application: quenching provides maximum strength, while normalization produces a more uniform microstructure with moderate strength and comparable ductility.

Finite element models of the porous structure of hydroxyapatite composite ceramics reinforced with multi-walled carbon nanotubes are developed and their mechanical characteristics are determined numerically using the finite element procedure. The effect of porosity and nanotube additives on the Vickers microhardness, compressive strength, and flexural strength of the model samples is investigated. It is shown that porosity and nanotube reinforcement have comparable effects on mechanical properties, which opens prospects for designing purpose-tailored biocomposites.

A computational model is presented to predict dynamic electric polarizability, magnetic susceptibility, permittivity, and permeability. We designed platinum macrocycles that function as molecular LC-circuits. Our results show a linear increase in the S₀→S₁ magnetic dipole transition moment with the number of phenyl subunits in platinum macrocycles. Furthermore, our analysis demonstrates that the achievement of negative permeability in molecular LC-circuits is critically dependent on the dipole transition moments, molecular concentration, and molecular environment.

High temperature hydrogen attack is one of the main problems of petrochemical equipment. The degradation process is considered to be irreversible during the steel decarburization. The paper presents research results of the type 09G2S steel samples cut from the wall of a petrochemical reactor, which is subjected to the brittle fracture with complete decarburization of the microstructure after 85 thousand hours of operation. Based on the data obtained, a method is proposed for the microstructure and mechanical property recovery using the two-stage heat treatment.

Ice crystal aggregates in cirrus clouds significantly disrupt precise satellite laser ranging to the GLONASS. This work proposed an efficient mathematical model for light scattering calculations of aggregates. This process is traditionally limited by computational resources of modeling such particles. The proposed model represents the aggregate scattering using the known solutions for individual particles. Computations by this model are much faster than direct numerical methods, while maintaining a maximum error of 20%. This accuracy is acceptable for calibration of satellite lasers. The model is validated against physical optics approximations and is also effective for studying the aggregate impact on the optical properties of cirrus clouds, which is useful for both atmospheric laser sensing and radiative transfer problems.

In the present paper, we report the photoluminescence (PL) and thermoluminescence (TL) of Ce doped Gd₂Zr₂O₇ phosphors prepared by using solid state reaction method. The Gd₂Zr₂O₇:Ce phosphors are found to have cubic structure and crystallite sizes in the nanometer range. Bonding between elements is determined by Fourier transform infrared (FTIR) spectroscopy. The PL study shows the blue emission of this phosphor, and 2 mol% gives the highest PL emission peak. The TL glow curve gives two peaks that determine the shallow and deep traps.

Ceramic matrix composites (CMCs) face persistent challenges related to wear reliability and crack sensitivity in advanced applications. This study investigates Al₂O₃–ZrO₂–TiOₓ composites fabricated using powder metallurgy, with alumina (Al₂O₃) fixed at 75 wt.%, zirconia (ZrO₂) varied from 20 to 10 wt.%, and titanium oxide (TiOₓ) varied from 5 to 15 wt.%. The powders were homogenized through high-energy ball milling and subsequently sintered at 1640 °C to achieve densification. Microstructural analysis (SEM and XRD) confirmed the formation of fine particles with stable crystalline phases. Tribological tests revealed composition-dependent behavior. A 75:20:5 wt.% composite exhibited excellent wear resistance, with wear stabilizing at 1.8–2.1 µm, a friction coefficient of 0.7, and a friction force of 6 kN. This performance was attributed to tribo-layer formation, ZrO₂ phase transformation, and the lubricating effect of TiO_x. A 75:15:10 wt.% composite demonstrated moderate wear (4–5 µm), with a stable but higher friction coefficient (0.8–0.9) and a friction force of 4–8 kN, reflecting strong surface grip. In contrast, a 75:10:15 wt.% composite stabilized at 4–4.5 µm wear, with a friction coefficient of 0.75 and a friction force of 4–4.5 kN, indicating variable sliding resistance but improved tribo-layer stability. Additionally, maintaining a specimen height-to-diameter (H/D) ratio of 3–4 minimized geometric errors, reduced crack initiation, and ensured reliable mechanical characterization. Inappropriate ratios, however, resulted in constraint effects, buckling, and edge cracking during cooling. Overall, the addition of TiOₓ to Al₂O₃–ZrO₂ composites improved the phase stability, crack resistance, and wear performance. Among the tested compositions, a 75:20:5 wt.% composite demonstrated the most balanced properties, making it a promising candidate for high-durability structural, high-temperature, crucible, and biomedical applications.

The paper studies formation features of dispersion-strengthened surface layers during low-energy, high-current electron beam (LEHCEB) processing of Cr-Zr and B‑Ti systems. It is found that pulsed LEHCEB processing leads to the formation of the surface structures, including nano- and sub-microcrystalline Cr₂Zr, TiB and TiB₂ strengthening phases. Control for the phase composition and morphology of strengthening particles in both systems, allows reaching a combination of the higher hardness and wear resistance. The threshold Cr content identified for the Cr-Zr system, is ≈37 at.%. An increase in this content, causes the formation of a microcrack network due to thermal stresses induced the difference in the thermal expansion coefficient between the intermetallic phase and the matrix. At the same time, rather a high (≈56 at.%) boron content in the B‑Ti system leads to the formation of uniform surface layers more resistant to cracking, which is associated with the high thermal compatibility of boride phases and the matrix.