Vibration Characteristics of Rolling Bearings Caused by Flexible Cage Plastic Deformation and Crack Propagation

The cage is a component of the rolling bearing. It is used to isolate the rolling elements and rotates with the rolling elements. The collision and friction between the rolling element and cage may lead to plastic deformation and crack failure of the cage after a long period of operation. To investigate their effects on bearing vibration characteristics, a dynamic model of rolling bearing considering the cage plastic deformation and crack propagation is proposed. In this study, an equivalent model for calculating the stiffness of cage cross beam and side beam is presented. The cage crack is regarded as a switching crack. The stiffness of the cage cross beam and side beam in the open crack state is different from that in the closed crack state. Besides, the plastic deformation of the cage can be regarded as the dimensional change of the cage pocket in the bearing circumferential direction and the cage flexibility is simplified by the discrete mass method. The rolling element’s contact with the raceway, its collision with the cage pocket, and its interaction with the cage’s guide surface are all taken into account by the dynamic model. Furthermore, the model also considers the elastohydrodynamic lubrication state between the rolling element and the raceway. The governing equations of rolling bearing dynamics are formed by the Lumped parameter method and solved by the fourth-order Runge Kutta method. Subsequently, the effects of the cage’s plastic deformation size and the depth of cage crack propagation on the impact force of the rolling element-cage interaction, as well as the vibration characteristics of the bearing, are investigated. The results indicate that the presence of a cage crack alters the load distribution within both the cage beam and the side beam, thereby inducing changes in the vibration signal spectrum characteristics of the bearing cage. The results can provide theoretical support for early failure detection of rolling bearing cages.