Experimental and theoretical approaches for determining cage motion dynamic characteristics of angular contact ball bearings considering whirling and overall skidding behaviors

Cage stability is an essential indicator of the guaranteed efficiency and reliability of the rolling element bearing. Moreover, cage instability can greatly shorten the bearing's service life. The whirl characteristics of the cage caused by ball–cage collisions are closely related to the overall bearing skidding degree. To explore the stability and skidding characteristics of self-lubricated cages used in spacecraft angular contact bearings, a comprehensive bearing dynamic model focused on cage characteristics is proposed. The cage was divided into Nb (number of balls) segments owing to the low stiffness of the cage material (porous polyimide). The model comprised ball self-rotating and revolution motions with 4*Nb degrees of freedom (DOF) and cage motions with Nb + 3 DOF. In the latter, 3 represents the cage whirling motion in the translational and axial directions. The ball-pocket normal and tangential forces, ball-pocket axial collisions, the ball-raceway traction force and moment, imbalances, centrifugal force, and thin oil film lubrication are included in the model. A test bench for exploring the cage motion with a high-speed camera to capture cage images was developed. Three experimental case studies investigating the effects of operating speed and applied load validated the effectiveness and accuracy of the model. Several indicators describing cage stability and cage skidding degree were proposed based on the experimental and theoretical results. It was found that the rate of increase of the whirl radius reduced with a linear increase in the rotation speed. The whirling radius displayed an approximate hyperbolic downward trend with increasing axial force. The skidding results suggested that applying a large axial load to the bearing may have been counterproductive in preventing bearing skidding. In addition, the cage was prone to instability as the radial load increased owing to intensive cage-guide ring rubbing.