Bulletin of the Russian Academy of Sciences: Physics最新文献

We investigated the application of distributed fiber-optic sensors (DFOS) based on Rayleigh scattering for high-resolution strain measurements in heterogeneous materials under four-point bending tests. Experiments on potassium salt compare full-length and two-point bonding strategies, showing that bonding configuration significantly affects the measured strain variability and interpretation of material behavior. The strain profile over the height of the specimen during the four-point bending test was registered using DFOS and used to estimate the position of the neutral axis. The results highlight both capabilities and limitations of DFOS in geomechanical applications.

The shell structures made of prepreg-based composite materials are of particular interest in space applications. Due to incomplete matrix cure, the material retains elasticity sufficient for shaping structures directly in space conditions. Once the structure is fully deployed, the material is fully cured under heating by radiant energy, which makes it rigid and strong. The main sources of radiation in Earth orbits are the Sun and the Earth. The amount of radiation emitted by the Earth is less (but not negligible) than that of the Sun. The aim of this paper is to assess quantitatively the degree of impact of the Earth’s radiation on a space object in low Earth orbit. Emphasis is placed on studying the dependence of this impact on the position of an object relative to the Earth, including the change of day and night, and on its location over different parts of the planet (poles, equator).

Safe operation of a structure is provided by monitoring its deformation behavior. An important part of it is the vibration response characterized by amplitude-frequency and phase parameters. In this study, the natural frequencies and mode shapes of load-bearing elements of a building structure are evaluated by using FEM. Based on the long-term monitoring of the vibration response on one of the load-bearing reinforced concrete beams, the evolution of the natural frequencies of the structure was obtained. It should be noted that these structural elements were damaged and repaired, which determined the interest of the study. The results of in-situ and numerical experiments are analyzed with respect to the current seasonal changes.

Heat flows characterizing free thermoconcentration convection of air–gas mixtures with undecane or water vapor, exhibiting first-order phase transitions, were measured. In the case of undecane, the Nu(Ra) dependence closely matches that of dry air. It is shown that experimental data for humid air require supplementary numerical processing, accounting for intensive and complex diffusive mass transfer. The role of thermodiffusion and Stefan flow in humid air is discussed.

Liquid metal flows generated in a cylindrical cell by the alternating magnetic field of a continuous or a sectioned inductor are studied numerically. It is found that the inductor parameters significantly affect the energy distribution of liquid metal velocity fluctuations. The more intense fluctuations are shift to the cell ends and the intensity of the fluctuations decreases as the inductor length increases. Using a sectioned inductor consisting of a set of solenoids accumulates the effect of the end boundaries of each section and generates an intense flow distributed over a cylindrical cell. A sufficiently uniform distribution of the velocity fluctuation field along the cell can be obtained without increasing the total number of ampere turns.

The influence of cyclic loading on the residual mechanical properties of the polymer composite was studied. Three-stage diagrams of Young’s modulus reduction, two-stage and three-stage diagrams of tensile strength reduction were experimentally obtained. A previously proposed phenomenological model was successfully applied for describing experimental data. The dependence of the fracture type after static tension on number of preliminary loading cycles was analyzed.

A spatially periodic gradient magnetic field generated by cylindrical assemblies of permanent magnets and non-magnetic washers is investigated numerically. The study shows that the magnetic fluid is most efficiently retained within the coaxial gap between the assembly and the outer non-magnetic wall when the distance between adjacent magnets exceeds their height.

We summarized the papers in the field of mathematical modeling, deformable solid mechanics and mining engineering aimed at creating a methodology for monitoring and assessing the deformed state of underground main gas pipelines, which are subjected to technogenic influence. These linear objects are located in the zones of minerals development by hidden method and their actual deformed state is directly determined by the volume and speed of mineral reservoirs development. The study presents the results of numerical modeling of a large number of boundary value problems. The methodology for estimating the actual deformed state of underground pipelines under development is presented.

Additive manufacturing technologies are unlocking new possibilities for rapid prototyping and the production of customized devices, which is especially valuable in the field of biomedicine. This study is focused on validating the numerical models of the mechanical behavior of scaffolds designed for bone tissue replacement. Evaluations were conducted across multiple scales to ensure comprehensive analysis. The results demonstrate a good agreement between numerical simulations and experimental findings, confirming the reliability of the modeling approach.

The aim of the present study is to experimentally investigate the effect of complex loading conditions on deformation behavior, damage accumulation, and fracture mechanisms of fiberglass specimens containing pre-existing cracks. Particular attention is devoted to the influence of preliminary cyclic loading and superimposed torsional vibrations on the kinetics of damage evolution. The experimental methodology involves the application of ultrasonic and thermographic techniques, which enable the detection and characterization of delamination zones under various loading regimes. It has been established that torsional vibrations exert a substantial influence on damage evolution and crack propagation. This effect is of considerable practical significance for assessing the strength and durability of composite structures operating under pronounced vibration conditions.