Papers by Keyword: Forced Oscillations

Abstract: The effect of the polyharmonic external excitation causes the emergence or onset of novel properties in the system. The article devoted into the oscillations induced in a rigid system by the polyharmonic external excitation. The analysis of the results obtained in this research confirms that the systems with the nonlinear elastic characteristics are rather sensitive to the changes introduced into the external excitation according to the law. Therefore, some assumptions, for instance, those concerning the monoharmonic nature of changes in the external excitation, which are commonly used in studying the real mechanical systems, are not always correct.

Abstract: The joint radial-axial oscilations of onemass model of rotor of high-speed pump are considered taking into account hydrodynamic forces, arising up in the radial clearance of annular seals. Connection of axial oscilations with radial is conditioned by dependence of conductivity of annular throttle, consequently, and axial force of balancing device, from the excentricity of shaft in the annular collar. amplitude and phase frequency characteristics of the forced oscilations, excited by harmonically changing pressure and static unbalance.

Abstract: The model of the hydropuls mechanism of drill machines is presented. The differential equations featuring mechanical and hydraulic processes for all cycle are given.

Abstract: A new algorithm OMI (Optimization in Multiple Intervals) for the computation of the logarithmic decrement from exponentially damped harmonic oscillations is described. This method is shown to be effective and computationally compact for high damping materials. A comparison between the OMI algorithm and the four classical methods usually used in the computation of the logarithmic decrement is reported. The OMI algorithm yields high precision in the computation of the logarithmic decrement and the smallest dispersion of experimental points on the plots of mechanical loss spectra. The effect of the acquisition parameters and the experimental conditions on the results of computations of the logarithmic decrement and the relative error is discussed.

Abstract: Extrinsic resonance effects observed in a low-frequency subresonant mechanical spectrometer are reported. High resolution of the mechanical spectrometer enables precise measurement of small values of the mechanical loss tangent ( tanϕ = 1- 2 × 10-4) and the apparent high values of the loss tangent detected for extrinsic resonance effects in the vicinity of the eigen frequencies of the spectrometer. Forced oscillations can be used as a ‘signal quality test’ to validate the quality of exponentially damped harmonic oscillations in the resonant mode.