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

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.

In this study, methods for enhancing the structural strength of conical orthopedic transtibial exoprosthetic sockets are investigated through the implementation of non-planar reinforcement using structured rods made of continuous carbon fiber. Numerical modeling based on progressive failure analysis according to an instantaneous damage law, incorporating material property degradation models, effectively demonstrated the damage accumulation process in the examined structures.

Magnetohydrodynamic (MHD) stirring of liquid metal is used in the continuous casting of round aluminum ingots to improve an ingot structure during its crystallization. The MHD stirrers developed for this purpose excite the vortex flow of liquid metal in both vertical and horizontal directions. Such bidirectional MHD stirrers have two rotating and travelling magnetic field inductors, which is a decisive factor in design of these stirrers. In this paper, we describe the MHD stirrer with small dimensions and with only one inductor, namely, a rotating magnetic field inductor, which induces in the liquid metal not only its rotation, but also flows in the vertical direction. In this paper, the verification of the used mathematical model is performed. The results of numerical modeling of the considered designs showed that the proposed design with inclined poles can be comparable in efficiency with MHD stirrers of classical construction. This indicates the relevance of further research into the efficiency of the proposed design.

A numerical simulation has been carried out to evaluate the effect of Rayleigh damping on the efficiency of passive suppression of free and forced harmonic vibrations of a thin plate using piezoelectric element connected to a passive electric circuit of different configurations. The solution is constructed using a finite element algorithm, which is developed in the context of the proposed mathematical formulation. It has been found that the efficiency of the considered method of vibration damping decreases with increasing contribution of another dissipative mechanism existing in the system.