Nonparametric modeling and vibration analysis of uncertain Jeffcott rotor with disc offset

Abstract

Uncertainty is extensively involved in the rotor systems of rotating machinery. The nonparametric modeling technique is first extended to the uncertain Jeffcott rotor with disc offset, and the random matrix model is established. Based on the Monte Carlo method, the effects of the dispersion parameters and the external bounded noise excitation on the vibrational characteristics of the system, such as the critical speed and the vibration amplitude, are investigated. Importance of different parameters is distinguished by sensitivity analysis of the first-order critical speed. It is shown that the critical speed increases with the increase of the offset degree of the disc and will also fluctuate due to the uncertainties, while the vibration amplitude fluctuates within the region enclosed by the upper and the lower envelopes of all the sample amplitudes, with the mean in ensemble close to the values calculated by the deterministic mean model. When the unbalanced force and the bounded noise excitation are imposed on the uncertain Jeffcott rotor, the fluctuation ranges of the critical speed and the vibration amplitude are further widened, and the maximum vibration amplitude can be more than double of the mean values. It is suggest that uncertainties of some sensitive parameters have to be treated carefully while others can be neglected.