Dynamic Characteristics of Rolling Elements in Cageless Bearings Based on a Nonlinear Dynamic Model

The main reason cageless bearings fail as protective bearings for magnetic levitation bearings is the uncontrolled motion of isolated rolling elements without a cage. This leads to sliding, friction, and collisions between the rolling element and the raceway, or among the rolling elements themselves. In this work, the universal nonlinear dynamic model of cageless bearings is established. The kinematic behavior of the rolling element in the cageless bearing is analyzed, and the sliding and discontinuous contact collision phenomena of the rolling element are explained from a kinematic perspective. Subsequently, the influence of different working conditions on the rolling-element contact behavior is demonstrated. In the model incorporating the randomness of rolling elements in cageless bearings, the numerical solution method is optimized. Experimental results confirm that the model is correct. The primary contact between adjacent rolling elements occurs in the transition zone between the loaded and unloaded zones. The higher the rotational speed, the less likely the rolling element is to collide and make contact. The larger the axial load, the more likely the rolling element is to rub continuously. The influence of radial load on the slip rate of the rolling elements is relatively small. These results provide a suitable operating range for cageless bearings.