Effect of start -stop motion on contact replenishment in a grease lubricated deep groove ball bearing

The impact of start-stops on the thickness of lubricating films in the Elasto-Hydrodynamic Lubrication (EHL) contacts in grease lubricated rolling bearings is different from that in oil lubricated bearings. This paper shows that the film thickness drops to zero quickly due to the absence of hydrodynamic effects during a stop. It quickly increases to an unexpected large value when the bearing is stopped for a long time and started up again, although this large value only lasts for a very short time. This is due to additional track replenishment during the stop leading to an initially thicker film than expected. This increase is found to be determined by the rotational speed of the bearing, stop-time, base oil viscosity and width of the contacts. The start-stop effect is similar for unidi-rectional and oscillating speeds, provided that the stopping time is long enough.

Automated summary

The impact of start-stops on the thickness of lubricating films in grease lubricated rolling bearings differs from that in oil lubricated bearings. The film thickness quickly drops to zero during a stop and unexpectedly increases to a large value when started again, due to additional track replenishment during the stop.