Effect of Variable Load on Centralized Dimple in an Opposite Sliding Condition

Abstract

In ball bearings without a cage, adjacent balls exhibit a zero-entrainment velocity (ZEV) contact condition, which is worse than typical pure rolling or rolling–sliding contact, and the contact between adjacent balls under periodic loading is notably more complicated. In this work, thermal elastohydrodynamic lubrication (EHL) numerical calculation is carried out under the condition of periodic impact and opposite sliding line contact over a wide range of surface speeds. The pressure is solved by a multigrid method, the elastic deformation is evaluated using a multigrid integration method, and the temperature field is calculated by a column-by-column scanning technique. The results show that the loading–unloading process exerts significant influence on the variation of the centralized dimple, pressure, and temperature rises as well as the oil characteristics. With the increase of surface speed, the effect of load fluctuations diminishes, and the central dimple exhibits the following evolutionary trend under ZEV conditions: no dimple at very low velocity—small central dimple—large typical dimple—no dimple at high velocity. The result indicates that under the ZEV condition of EHL stage, elevated velocities decrease the coefficient of friction and augment the film thickness.