Influence of outer ring crack and spalling on nonlinear dynamic behaviors of bearing-rotor system

Under high-speed conditions, the outer ring of the bearing is susceptible to crack propagation and surface spalling due to operational stress. And these defects significantly reduce the operational reliability and lifespan of the bearing-rotor system. Considering the characteristics of outer ring defects, a 10-degree-of-freedom dimensionless dynamics model is established. So it can be introduced the equivalent contact stiffness and impact force function. The vibration features of the bearings outer ring defects are researched. Meanwhile, the effects of various conditions on the bearing-rotor system are analyzed by utilizing phase trajectories, Poincaré maps and bifurcation diagrams. Ultimately, the effect mechanism of various parameters on the dynamic response of the bearings are obtained through experiments. It shows that for faulty bearing outer rings, the time-domain vibration signals of the experiment and the simulation are highly consistent, and the system appears bifurcation with changes in speed and transforms from periodic motion to chaotic motion. For fault-free bearing, due to the occurrence of outer ring defects, chaotic motion can appear earlier and significantly expand the unstable area of the system. Furthermore, the spectrogram allows the identification of frequency components related to the outer ring fault frequency. Finally, the maximum error in the frequency amplitude of the experiment and simulation is 5.8%. It can offer important theoretical foundation for the work, maintenance and fault recognition of bearings.