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Том 63, № 4 (2018)
- Год: 2018
- Статей: 10
- URL: https://journals.rcsi.science/1028-3358/issue/view/12109
Physics
Reflection of an Ultrashort Pulse by an Ideally Conducting Cylinder
Аннотация
A technique for calculating the backscattering of ultrashort pulses of plane waves by an ideally conducting cylinder is described on the basis of the spectral representation. The Rayleigh solution in the Bessel function series representation is used to determine the scattering spectral components. The Gabor impulse reflection is investigated. A method for remote determination of the cylinder diameter from the shift of scattered field amplitude peaks is described.
139-141
Properties of Thin Films of Barium–Strontium Titanate Solid Solutions by Induced Piezoelectric Effect
Аннотация
Piezoelectric effect equations have been derived by linearizing the nonlinear equations of state of a thin film existing in a paraelectric phase in the presence of an external electrical field (induced piezoelectric effect). The behavior of the piezoelectric and elastic constants of thin films of a solid barium–strontium titanate solution BST065 (x = 0.65) in a planar field at different misfit strain values has been studied numerically.
142-146
Corrosion Wear under Vibrations
Аннотация
The algorithms of investigation and processing of results are described. The results of investigations of the vibration effect on corrosion wear of steel samples in an aqueous medium are presented. Cases of horizontal and vertical arrangement of samples are considered. It is noted that the samples subjected to vibration are affected by greater corrosion wear in an aqueous medium.
147-149
Technical Physics
The Effect of Stress Pulses on the Structure of Ice in an Intermediate Layer
Аннотация
The effect of stress pulses on the formation of an intermediate layer in freshwater ice under an impact and in the ice bulk at a shear under conditions of quasi-static compression is considered when applying finite-amplitude elastic waves and when the fronts of these waves collapse.
150-154
Mechanics
Laser Photoacoustic Microscopy of Vickers Indentations in Titanium
Аннотация
The images of Vickers indentations in titanium are obtained by photoacoustic microscopy with piezoelectric-signal detection. It is shown that the analysis of the photoacoustic-image features makes it possible to obtain information on the nature of internal stresses in metal. In the framework of the single-temperature model of material thermoelasticity, it is demonstrated that the detected changes in the structure of photoacoustic images may be caused by the dependence of the thermal-expansion coefficient on stresses and by the presence of stress concentrators within the indentation.
155-157
Modeling of Gas Flow through a Granular Bed of a Thermal Storage Phase-Change Material
Аннотация
A mathematical model and a numerical method for description of time-dependent gas flows through granular thermal storage phase-change materials (PCMs) have been proposed. Such granular PCMs are modeled as porous solid–solid phase-change media using the methods of heterogeneous continuum mechanics without detailing the processes inside individual particles. The calculation results are compared with the experimental measurements to show their good agreement with each other.
158-160
Semi-Inverse Solution of a Pure Beam Bending Problem in Gradient Elasticity Theory: The Absence of Scale Effects
Аннотация
The semi-inverse solutions of pure beam bending problems within the three-dimensional formulation of gradient elasticity theory as exact tests for the problem of estimating the efficient bending stiffness of so-called scale-dependent thin beams and plates due to the necessity of modeling sensing devices are presented. It is shown that the solutions within the gradient elasticity theory give classic beam bending stiffnesses and demonstrate the invalidity of the widespread results and estimates obtained in the past 15 years during study of scale effects within the gradient beam theories, according to which the relative bending stiffness grows by a hyperbolic law with decreasing thickness.
161-164
The Theoretical Basis of the Possible Application of a Kovalevsky Gyroscope as Three-Component Angular-Velocity Meter
Аннотация
Two schemes of the three-component angular-velocity meter based on the Kovalevsky gyroscope are described: on the electrostatic and mechanical spring suspensions. The gyroscopic degrees of freedom are restricted on the observation coordinates, and there is a rapid rotation around its principal axis. A mathematical model of the device motion along three translational coordinates and two angular coordinates is presented. The formulas for determining the two components of the mobile-object angular velocities lying in the equatorial plane are derived by using the signals in the channels of the radial interaxial correction as well as the algorithm of calculation with the help of an onboard controller of the angular-velocity component of rotation around the object axis, which practically coincides with the principal one. The algorithm includes the coordinates of the relative translational equatorial motions of the rotor and their first and second time derivatives. The algorithms of their determination with the interference filtering based on the Leuenberger observing identification device are given.
165-168
An Optimum Absorber of Vibrational Energy
Аннотация
Analytical expressions for the impedance characteristics inherent to an optimum absorber are derived. The results of the laboratory experiment in which the simplest optimum absorber is constructed and investigated are presented, and the validity of the analytical relations obtained is confirmed.
169-172
The Acoustic Gap as a Diagnostic Sign of Prefracture
Аннотация
The relation between the acoustic-gap period observed during the tension of previously loaded samples from steels 20 and 45 and the plastic-deformation work (the fracture magnitude) estimated from the area under the strain curve is established. It is shown that the gap period increases with the relative life.
173-176