Vibrations in engineering and technology

Olshansky Vasiliy – Doctor of Physical and Mathematical Sciences, Professor of the Department Physic of Theoretical Mechanics Kharkov National Technical University of Agriculture named after Petr Vasilenko (St. Alchevskih 44, Kharkov, 61002, Ukraіne, e-mail: OlshanskiyVP@gmail.com).

Olshansky Stanislav – PhD in Physics and Mathematics, Kharkov National Technical University of Agriculture named after Petr Vasilenko (St. Alchevskih 44, Kharkov, 61002, Ukraіne, e-mail: stasolsh77@gmail.com).

Tokarchuk Oleksіі – PhD, Associate Professor of the Department of «Technologіcal Processes and Equіpment for Processіng and Food Productіons» of the Vіnnytsіa Natіonal Agrarіan Unіversіty (St. Solnyshchnaya, 3, Vіnnytsіa, Ukraіne, 21008, e-maіl: tokarchyk@vsau.vіn.ua.

The motion of an oscillatory system with one degree of freedom, described by the generalized Rayleigh differential equation, is considered. The generalization is achieved by replacing the cubic term, which expresses the dissipative strength of the equation of motion, by a power term with an arbitrary positive exponent. To study the oscillatory process involved the method of energy balance. Using it, an approximate differential equation of the envelope of the graph of the oscillatory process is compiled and its analytical solution is constructed from which it follows that quasilinear frictional self-oscillations are possible only when the exponent is greater than unity. The value of the amplitude of the self-oscillations in the steady state also depends on the value of the indicator. A compact formula for calculating this amplitude is derived. In the general case, the calculation involves the use of a gamma function table. In the case when the exponent is three, the amplitude turned out to be the same as in the asymptotic solution of the Rayleigh equation that Stoker constructed. The amplitude is independent of the initial conditions. Self-oscillations are impossible if the exponent is less than or equal to unity, since depending on the initial deviation of the system, oscillations either sway (instability of the movement is manifested) or the range decreases to zero with a limited number of cycles, which is usually observed with free oscillations of the oscillator with dry friction. These properties of the oscillatory system are also confirmed by numerical computer integration of the differential equation of motion for specific initial data. In the Maple environment, the oscillator trajectories are constructed for various values of the nonlinearity index in the expression of the viscous resistance force and a corresponding comparative analysis is carried out, which confirms the adequacy of approximate analytical solutions.

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