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Nakhatakyan F.G.,RAS Blagonravov Institute of Mechanical Engineering
Russian Engineering Research | Year: 2017

An analytical method is developed for determining the contact parameters of cylinders when the contact geometry and structure are taken into account. If there is a gap in the roller bearing, this method permits determination of the maximum load on the roller, the roller displacement and rigidity, and the number of loaded rollers as a function of the gap width and external load. © 2017, Allerton Press, Inc.


Voronin N.A.,RAS Blagonravov Institute of Mechanical Engineering
Russian Engineering Research | Year: 2017

A method is proposed for calculating the elastic modulus of a thin hard coating from the loading curve in indentation, on the basis of modified Hertz theory. The results may be used in assessing the properties of hardened surfaces. © 2017, Allerton Press, Inc.


Bobrovnitskii Y.I.,RAS Blagonravov Institute of Mechanical Engineering
Acoustical Physics | Year: 2014

An approach is proposed to describe a general form of acoustic media, in particular, acoustic metamaterials, based on their modeling with the simplest discrete periodic structures. The parameters of the discrete models, determined from the dispersion equation, are taken as the effective parameters of the modeled media. Transfer to an effective continuous medium is achieved by uniform distribution of these parameters over the length of the periodicity cell. It is shown that all of the wave motion characteristics of the medium, including the energy characteristics, are expressed through the effective parameters thus introduced. The necessary formulas are derived. Examples are given. The proposed method is useful for designing acoustic materials with the given wave properties. © 2014 Pleiades Publishing, Ltd.


Bobrovnitskii Yu.I.,RAS Blagonravov Institute of Mechanical Engineering
Acoustical Physics | Year: 2013

The general formulas are derived for calculating the kinetic and potential energies and other energy characteristics of linear oscillatory systems, a portion of the degrees of freedom of which are internal, i.e., inaccessible for direct measurements and/or excluded from consideration. The energy characteristics are expressed by means of parameters pertaining only to the part of accessible (or selected for consideration) degrees of freedom. The formulas are derived based on the use of certain novel properties of the so-called Shur matrix complement. The obtained formulas are applicable for calculating the energy characteristics of the elements of acoustic metamaterials by means of their effective inertial-elastic parameters. The main focus is the case of negative values of these parameters. Proceeding from the nonnegativity of the kinetic and potential energies of mechanical structures, limitations on the character of the frequency dependences of the effective parameters are formulated. © 2013 Pleiades Publishing, Ltd.


Bobrovnitskii Y.I.,RAS Blagonravov Institute of Mechanical Engineering
Acoustical Physics | Year: 2015

For two-dimensional linear acoustic metamaterials and media represented in the form of periodic structures made of complex cells, a general model is proposed, formulas are derived for the effective parameters and energy characteristics, and the restrictions imposed on such media are formulated. They are divided into four main types, differing in general wave properties; the differentiating features of each type are shown. Several new schemes of negative and hyperbolic types of discrete and continuous metamaterials are presented, for which the dispersion dependences are constructed and the corresponding “wave” equations are written. © 2015, Pleiades Publishing, Ltd.


Kovriguine D.A.,RAS Blagonravov Institute of Mechanical Engineering
Archive of Applied Mechanics | Year: 2012

We analyze a classical problem of oscillations arising in an elastic base caused by rotor vibrations of an asynchronous driver near the critical angular velocity. The nonlinear coupling between oscillations of the elastic base and rotor takes place naturally due to unbalanced masses. This provides typical frequency-amplitude patterns, even let the elastic properties of the base be linear one. As the measure of energy dissipation increases, the effect of bifurcated oscillations can disappear. The latter circumstance indicates the efficiency of using vibration absorbers to stabilize the dynamics of the electromechanical system. The second section of this paper presents results of theoretical studies inspired by the problem of reducing the noise and vibrations by using hydraulic absorbers as dampers to dissipate the energy of oscillations in railway electric equipments. The results of experimental trials over this problem and some theoretical calculations, discussed in the text, are demonstrated the ability to customize the damping properties of hydraulic absorbers to save an electric power and to protect the equipment itself due to utilizing the synchronous modes of rotation of the rotors. © Springer-Verlag 2011.


Bobrovnitskii Yu.I.,RAS Blagonravov Institute of Mechanical Engineering
Acoustical Physics | Year: 2012

The paper introduces the concept of equivalent mass and elasticity. The physical sense of their negative values is explained, and it is demonstrated that they do not contradict the laws of conservation of energy and impulse. Formulas are introduced to calculate the energy of equivalent mass and elasticity. The limits on the character of their frequency dependences are formulated. In particular, it is noted that it is impossible for negative mass and elasticity to be independent of frequency. © Pleiades Publishing, Ltd., 2012.


Bobrovnitskii Yu.I.,RAS Blagonravov Institute of Mechanical Engineering
Doklady Physics | Year: 2012

An alternative theoretical solution to the problem of acoustic stealth, as well as the corresponding new approach to the development of acoustic metamaterials is presented. This approach seems to be rather promising and simple from the standpoint of its realization. The data of a laboratory experiment are also presented, which confirm the adequacy of the proposed impedance solution to the problem of acoustic stealth. The experiment has shown a high efficiency of the scattered field control. This was achieved by governing the surface impedances of the scattering body. The tomographic method being intensely developed in the framework of geological probing, medical acoustics, and other branches of science is more complicated but rather efficient. In this method, irradiation is realized from various sides, whereas the fields scattered in different directions are received synchronously by a certain group of receivers. Suppression of backward signals is insufficient for tomographic invisibility.


Ganiev R.F.,RAS Blagonravov Institute of Mechanical Engineering
Journal of Machinery Manufacture and Reliability | Year: 2014

The works presented at the meeting of the enlarged Academic Board devoted to the 75th anniversary of the Blagonravov Institute of Machine Science (IMASh RAS) are reviewed. The main stages of the scientific and reorganization activity of the institute are briefly described and both traditional scientific research lines and the results of the most advanced developments including applications of wave techniques in various industries are reported. © 2014 Allerton Press, Inc.


Verichev N.N.,RAS Blagonravov Institute of Mechanical Engineering
Journal of Sound and Vibration | Year: 2012

In this paper, torsional vibrations of imbalanced shaft driven by a limited power supply are studied. It is shown that mutual interaction of shaft and power supply may in particular result in chaotic self-oscillations that correspond to the strange attractors in the phase space of the coupled dynamical system shaftpower supply. In this particular model, strange attractors represent classical Lorenz and Feigenbaum attractors. Rotation characteristic of the power supply and resonance characteristic of the shaft rotational motion in one of the resonance zones are studied. It is shown that at certain intervals, these characteristics may be non-unique, which corresponds to the case of chaotic dynamics. Such non-trivial properties of the coupled system shaftpower supply could be used for a better understanding of complex vibrational phenomena in real applied systems such as problems related to the damping of the torsional vibrations. © 2011 Elsevier Ltd. All rights reserved.

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