Effect of cage pocket wear on the nonlinear dynamics of a full-ceramic bearing-rotor system under starved conditions

The high rigidity and small deformation of full-ceramic bearings make them essential components in high-end rotating machinery. However, at high speeds, the lubricant in the contact area between the ball and the raceway is constantly forced out, causing the full ceramic bearing to run out of oil. This leads to increased friction between the ball and the cage, accelerating cage wear. Using the lumped mass approach, a dimensionless model with ten DOFs is constructed to study the effects of cage wear on the dynamic properties of a bearing-rotor system with starved lubrication. The model accounts for the phenomenon of starved lubrication occurring when the ball and raceway come into contact, as well as the interaction between the worn-out cage and the bearing components. An analysis is conducted on the impact of the cage on the dynamic characteristics of the system at varying levels of wear. An analysis of the nonlinear vibration is conducted using a bifurcation diagram and a Poincare section. Ultimately, a comparison is made between the experimental data and the simulation results. The findings indicate that as rotational speed rises, the distribution of lubricating oil becomes uneven, and there is a noticeable decrease in both the volume fraction and thickness of the lubricating oil. After the cage wear is aggravated, the frequency component mfs +/- nfc becomes more abundant in the frequency diagram, and the concentration of vibration energy is primarily in the low-frequency range. The experimental results are largely congruent with the computational results, with a maximum frequency domain error of 5.88%. The model precisely characterizes the frequency features of cage defects resulting from wear due to starved lubrication in fullceramic bearings. It provides important information for fault detection and health status monitoring of fullceramic bearings.