A nonlinear dynamic model for the skidding and the over-skidding in industry scale angular contact ball bearing

The skidding phenomenon, consisting of sliding and spinning may between the rolling elements and the raceways of bearings, can reduce significantly the service life. In order to early predict the arising of the skidding in angular contact bearings, a dynamic model is introduced in this paper. The centrifugal force and the gyroscopic effect are also taken into account to determine the load distribution determined by the rolling elements. The model of the rolling element orbital kinematics considers the elasto-hydrodynamic (EHD) lubrication and its contribution to the friction forces, along with the lubricant oil drag effect, the rolling element gravity and the ball-cage interactions. The fourth order Runge-Kutta integration and Newton-Raphson iteration methods are employed to calculate the load distribution, and the dynamic motion of the rolling elements and cage. The comparison between the results obtained by means of the proposed model and some experimental data shows a general good agreement. The experimental data have been obtained in a test rig equipped by an industry scale angular contact ball bearing under different axial load. Under high load, the experimental speed ratio of the cage versus the bearing inner race exceeds the pure kinematically determined value: this phenomenon is defined as over-skidding behavior and it is also simulated by the proposed model. The pure rolling state of rolling elements are also predicted by the proposed model at high axial load. The mechanism of skidding and over-skidding are also discussed based on the proposed model. In the future, the model presented will be supplemented with a temperature analysis, considering the variation of the lubricant viscosity in a full thermo- elasto-hydrodynamic (TEHD) approach.