Nonlinear dynamic behaviors of a shaft-bearing-pedestal system with outer ring slip and damage

Bearings often experience ring slip and raceway damage due to fit looseness, which induces abnormal dynamic behavior. In this study, a dynamic model of the shaft-bearing-pedestal system with outer ring slip and damage is developed based on the Hertz contact theory and the lumped parameter method. A three-degree-of-freedom model for bearing ring slip is proposed, and the fractal function is used to characterize the damaged surface morphology of the bearing raceway. The effects of fit looseness on system dynamic response and the damage vibration of the bearing outer ring are investigated through simulation. The typical dynamic characteristics are verified by experiments. The results indicate that an increase in looseness degree leads to a noticeable rise in higher frequencies of the rotating frequency, as well as odd-multiple frequency components appearing in the spectrum. The system undergoes bifurcation, transitioning from periodic motion to chaotic motion. Under the severe looseness condition, sub-harmonic frequencies and continuous spectra further appear in the system. The strong nonlinear impact force between the outer ring and the pedestal is the main reason for the instability and chaotic motion of the system. Due to the outer ring slip caused by bearing looseness, there is a decrease in bearing damage frequency value. This work provides valuable insights for operation, maintenance, and early fault warning related to bearings.