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2 2017

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Optimization of the impact multi-mass vibration absorbers

Kernytskyy I., Diveyev B., Horbaj O., Hlobchak M., Kopytko M., Zachek O.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

2017

Vol. 26, No. 3

394--400

The problem of attaching dynamic vibration absorber (DVA) to a discrete multi-degree-of-freedom or continuous structure has been outlined in many papers and monographs. An impact damping system can overcome some limitations by impact as the damping medium and impact mass interaction as the damping mechanism. The paper contemplates the provision of DVA with the several of the impact masses. Such originally designed absorbers reduce vibration selectively in maximum vibration mode without introducing vibration in other modes. An impact damper is a passive control device which takes the form of a freely moving mass, constrained by stops attached to the structure under control, i.e. the primary structure. The damping results from the exchange of momentum during impacts between the mass and the stops as the structure vibrates. The paper contemplates the provision of the impact multi-mass DVA’s with masses collisions for additional damping. For some cases of DVA optimization such a design seems more effective than conventional multi-mass DVA with independent mass moving. A technique is developed to give the optimal DVA’s for the elimination of excessive vibration in harmonic stochastic and impact loaded systems.

Dynamic vibration absorbers – optimization and design

Pelekh Ya., Diveyev B., Hlobchak M.

ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes

2017

Vol. 6, No 1

23--30

The main aim of the paper is improved dynamic vibration absorbers (DVA) design, taking into account the complex rotating machines dynamics. It is often impossible to balance the rotating elements so as to reduce the vibration to an acceptable level. The paper considers the provision of DVA or number of such DVA. Such originally designed DVA reduces vibration selectively in the maximum mode of vibration without introducing vibration in other modes. The result is achieved at a far lower expense than would be required to replace the concrete and steel foundation with a more massive one. By installing DVA, one can minimize excitation virtually at the source. In order to be more effective, a vibration absorption system should react in all the frequency domains. The present absorber also has as an advantage that it can be constructed so that it has a wide-range vibration absorption property. This construction allows for an easy connection of the above rotor equipment. In order to determine the optimal parameters of DVA, the complete modeling of the rotating machine dynamics is obvious. The two degrees of freedom model are totally inadequate to accurately calculate the vibration frequencies of the construction and therefore, for a sufficiently accurate determination of its dimensional characteristics so as to determine such frequencies. It is therefore necessary in practice to dimension the construction through more complex modeling. In particular, concentrated mass and rigidity calculation methods may be adopted based on an even more accurate theoretical determination. The numerical schemes (NS) row is considered for the complex vibration-excited constructions. Methods of decomposition and the NS synthesis are considered on the basis of new methods of modal synthesis. Complex NS are obtained of discretely-continua type, which enables in the adaptive mode to calculate tension not only in the continuum elements, but in the places of the most tension concentration in joints. Traditional design methodology, based on discontinuous models of structures and machines is not effective for high frequency vibration. The present research develops a modern prediction and control methodology, based on complex continuum theory and application of special frequency characteristics of structures. Complex continuum theory allows to take into consideration system anisotropy, supporting structure strain effect on equipment motions and to determine some new effects that are not described by ordinary mechanics of the continuum theory. The absorbers in accordance with this paper may be applied not only to electric machines ore aeronautic structures, but also to any other type of vibration-excited structure, such as cars, chisel installation, optical, magneto-optical disks, washing machines, refrigerators, vacuum cleaners, etc.