## Theoretical and experimental studies of the stress-strain state of expansion bellows as elastic shells.

Published in category «Simulation of physical processes»

This paper studies a stress-strain state of the U-shaped expansion bellows under an internal-pressure induced load. The bellows is considered as a corrugated shell of revolution under axisymmetric load. The governing equations have been derived and the numerical calculations of the stress-strain state were carried out. A variant of the classical shell theory based upon Lagrangian mechanics was used. The finite-difference method was applied to solve the obtained system of ordinary differential equations. The ultimate internal pressure resulting in plastic deformations was determined. A simulation of the loss of equilibrium stability of the expansion bellows was performed. The ANSYS code was used for Finite-Element Method (FEM) in order to calculate the stress-strain state in the bellows.

## Calculations of the airfoil profile flow using two-dimensional RANS: an analysis of the reasons for the accuracy decrease.

Published in category «Simulation of physical processes»

Flows around sets of airfoils with different shapes and thicknesses have been numerically investigated at the relatively high Reynolds number (Re ≥ 106) and the low turbulence intensity (I ≤ 0.1 %) using two-dimensional (2D) Reynolds Averaged Navie-Stokes equations (RANS) in the combination with different semi-empirical turbulence models. The effects of different factors such as wind tunnel walls, the compressibility and the influence of the laminar-turbulent transition were investigated. The most probable reasons for the systematic disagreement between simulation and experimental data were established to be 3D effects impossible to be taken into account within 2D simulation or imperfection of the present-day semi-empirical turbulence models.

## Endwall heat transfer effects on the turbulent mercury convection in a rotating cylinder.

Published in category «Simulation of physical processes»

The obtained results of direct numerical simulation of the free mercury convection in a rotating cylindrical container heated from below are presented. Setting the Prandtl number equal to 0.025 and the height-to-diameter ratio equal to 1.0, effects of container rotation and heat transfer in horizontal solid walls have been studied. The effective Rayleigh number was close to 106. The Navier – Stokes equations, written with the Boussinesq approximation, were solved using the fractional-step method. The instant and time-averaged flow fields, the pulsation spectra and the integral heat transfer data were analyzed. The in-house code SINF/Flag-S results were compared with the available experimental data, and with the data obtained using the commercial software ANSYS Fluent 15.0.

## Geometric modeling of midi-fullerene growth from C32 to C60.

Published in category «Atom physics and physics of clusters and nanostructures»

Axonometric projections together the corresponding graphs for fullerenes are constructed in the range from 32 to 60. The growth of fullerenes is studied on the basis of a mechanism according to which a carbon dimer embeds in a hexagon of an initial fullerene. This leads to stretching and breaking the covalent bonds which are parallel to arising tensile forces. In this case, instead of a hexagon adjoining two pentagons, two adjacent pentagons adjoining two hexagons are obtained. As a result, there arises a new atomic configuration and there is a mass increase of two carbon atoms. We considered the direct descendants of fullerene. C32; namely, C2n where n = 17 – 30.

## Home-produced waveguide lasers of the LCD series and some features of their application.

Published in category «Experimental technique and devices»

The influence of various factors on stability of the performance data of compact CO2 waveguide lasers (the LCD series) produced by Plazma JSC in Russia has been considered for the first time. An angular misalignment of cavity mirrors was found to be the main reason for the relative instability of the laser emission in the frequency range of 0 – 0.5 Hz. These lasers work under RF excitation and have a power output from 3 to 50 W in a non-selective oscillating mode. Lasers can work at the fixed emission wavelength or in the wavelength-change mode. Preprogrammed dynamic control of the laser’s emission spectrum can be carried out in the automatic mode using the built-in servo-driver from the personal computer. The CO2 waveguide lasers of the LCD series can be used in laser lidar systems, particularly, for observation of small-sized objects and monitoring of the environment.

## A fiber-optic doppler blood flow-velocity sensor.

Published in category «Experimental technique and devices»

The mock-up of а fiber-optic Doppler blood flow-velocity sensor has been made and described. The principle of its operation is based on the recording of the Doppler shift of scattered radiation of a monofrequent single-mode semiconductor laser. The radiation was inserted into a blood vessel model using a fiber-optic probe. The performance data of the mock-up in the blood vessel model was measured. The designed apparatus was shown to make possible the reliable measurement of the blood flow velocity in the blood vessels through inserting the fiber optic probes. The measurement accuracy depends on the accuracy of the used recording equipment. The performance data of the designed apparatus, that obtained using the blood vessel model, meets all modern requirements.

## Quasi-polynomial 3D electric and magnetic potentials homogeneous in Euler’s sense.

Published in category «Physical electronics»

Electric and magnetic fields homogeneous in Euler’s sense are a useful instrument for designing the systems of charge particle optics. The similarity principle for the charged particle trajectories in these fields was applied by Yu.K. Golikov for the first time to create spectrographic charge particle optical systems in a more systematic and intelligence way when using the fields being homogeneous in Euler’s sense. This paper studies the Laplace potentials homogeneous in Euler’s sense. The coefficients of the polynomials are functions of the two rest coordinates; they are presented not by the polynomial but ought to be the functions harmonic and homogeneous in Euler’s sense. We have solved a finite chain of Poisson equations starting from the highest coefficients. By means of the proposed procedure we obtained new classes of potentials which provided a base for electric and magnetic spectrograph systems.

## On the quasi-polynomial 3D potentials of electric and magnetic fields.

Published in category «Physical electronics»

Spectrographic electron and ion optical structures markedly raise the possibilities of modern energy and mass analysis. Electric and magnetic fields which potentials are expressed by functions homogeneous in Euler’s sense are the effective instrumentation that is used for creating new spectrographic analytical devices with the determined working characteristics. This paper puts forward and discusses some methods for building 3D harmonic and homogeneous in Euler’s sense structures representable as the polynomials of finite degree with respect to one of variables. These strictly mathematical approaches provide a possibility of expanding significantly a class of quasi-polynomial potentials and of enriching modern analytical instrumentation by new spectrographic electrical and magnetic configurations.

## Dielectric properties of the nanocrystalline cellulose – potassium iodide composites

Published in category «Physical materials technology»

The linear and nonlinear dielectric properties of composites based on KIO3 and nanocrystalline Acetobacter Xylinum cellulose have been studied. This cellulose is structured so that it has a large amount of nano-channels with parallel arrangement and with diameters of 50 – 100 nm and the lengths being thousand-fold. The behavior of the linear dielectric permittivity of the bulk KIO3 was found to have four anomalies at the temperatures corresponding to phase transitions. The temperature elevations of 20 and 24 K, respectively, for the IV → III and III → II structural transitions were revealed for the KIO3 in the pores of the nanocrystalline cellulose relative to corresponding transition temperatures in the bulk KIO3. Possible causes for the revealed temperature elevations were discussed.

## The structure and morphological properties of clinoptilolite modified by manganese dioxide.

Published in category «Physical materials technology»

The chemical composition and morphological properties of сlinoptilolite-bearing materials modified by MnО2 have been studied using modern physical methods. The scanning electron microscopy, X-ray spectral microanalysis and optical reflection microscopy were applied. It was experimentally shown that MnО2-modified samples with high and low Si/Al ratios differed in such parameters as the layer thickness, the surface concentration, the degree of particle-surface dealumination, and did in morphological peculiarities of MnО2-phase. This phase in the samples with high Si/Al ratio exhibited the structure formed by nanorods of 10 – 20 nm in diameter and 500 – 700 nm in length. These nanorods are intermeshed in the net which is cross-linked with the surface of the clinoptilolite particles. The MnО2-modification of the samples was established to result in improving their mechanical and chemical strength as compared with the initial forms.

## An estimation of the strain-stress state under cyclic loading by the acoustoelasticity method.

Published in category «Mechanics»

The paper studies the applicability of the acoustoelasticity method to estimation of the strain-stress state under cyclic loading. It has been found that the uniform distributions of the acoustic anisotropy along the working part of the sample and of the velocities of longitudinal and transverse ultrasonic waves become non-uniform substantially with an increase in the number of stress cycles. Moreover, the largest absolute values of the acoustic anisotropy fell on the points with the largest plastic deformations, in particular, in the area of the sample dispersion. The effect was being recorded from the early stages of the sample loading till the fracture of the sample.

## Experimental investigation of the acoustic anisotropy field in the sample with a stress concentrator.

Published in category «Mechanics»

The behavior of the acoustic anisotropy and the longitudinal wave velocity in the case of multiaxial stress-strain state of the plate under inelastic deformation has been studied experimentally. The plate had a stress concentrator in the form of the central hole. The results for a number of deformation levels, and the results of finite element analysis of active stresses were presented. The qualitative agreement between calculated stress fields and the distribution fields of acoustic anisotropy was revealed. It was found that the maximum in magnitude of acoustic anisotropy values fell on the areas with the greatest stresses near the concentrator. It was supposed that the non-uniform distribution of the acoustic anisotropy in material testified to a possible stress concentration at the corresponding points.

## Verification and adaptation of the plasticity models under complex variable loading with intermediate complete and partial unloadings.

Published in category «Mechanics»

The experimental studies of elasto-plastic deformation of tubular steel samples under proportional and non-proportional (monotonic and cyclic) loadings, including partial and intermediate loadings, have been conducted with the aim of improving the accuracy of the description of the complex passive loading processes. The plastic strain accumulation was observed in the course of tests carried out under passive loading. However, this effect turned out not to be described by the plastic flow theory. This result required the development of an alternative material model. The comparisons of experimental results with the predictions of the structural (rheological) elasto-plastic model and the multisurface theory of plasticity with one active surface were made. Modifications of the constitutive equations were proposed in order to improve the accuracy of the material response prediction.

## Radio emission of the group of stars in the Aquarius and Cetus constellations.

Published in category «Astrophysics»

In the present work, the optical identification of a group of radio sources located in the Aquarius and Cetus constellations at a field of size 1.2 square degrees has been carried out. Ten radio sources under investigation were identified with stars and one object was identified with a diffuse image (ESO-538-10). It should be stressed that eight radio objects were found to have a non-thermal radio spectrum. This fact is likely to indicate the presence of the significant magnetic field in the atmosphere of the sources. Precise radio and optical coordinates of the identified objects were suggested. Significant radio refraction in the interstellar medium in the tested space direction was revealed.