Dynamic analysis of rolling ball bearing-rotor based on a new improved model

Dynamic analysis for a bearing-rotor system with the imbalance and the asymmetric gap is conducted in this paper. A new improved analytical model overall considering the gap, the varying compliance vibration and the time-dependent unbalanced force is established, especially the new model is more accurate and closer to reality by abandoning the assumption of the traditional model that the three center points of the inner ring, the outer ring and the rolling ball are collinear. More general vibration characteristics are described and the calculation results based on the new model are more universal than those based on the traditional model. The comparison of the calculation result between the improved model and the traditional model shows that the phase difference for the two results is obviously different from each other, the dominant frequency has no obvious difference between the two models and the amplitudes have somewhat difference. The parametric excitation vibration induced by the varying compliance force of the rolling ball on the inner ring-rotor is analyzed and then the influences of the rotating speed, the gap, the eccentricity and the mass of the rotor on the nonlinear responses are studied and some important conclusions are drawn. As the speed increases, the VC frequency gradually loses its domination of the frequency spectrum, and the rotational speed frequency and its combined frequency with the VC frequency dominate the vibration. The bearing-rotor system is susceptible to the variations of the rotational speed, the gap, the eccentricity and the mass of the rotor in certain ranges; the parameters can make the system in a relatively stable, stable and unstable state; the system shows the complex dynamic behaviors such as the periodical vibration, the quasi-periodic vibration, the chaotic motion and the jumping phenomenon, the bifurcation, sudden change. The research is significant for the quantitative calculation of the dynamic response for parameter designation and the fault diagnosis of the system.