Critical Sliding in Rolling Bearings under Hydrodynamic Friction Conditions

Abstract—

Conditions for seizing during hydrodynamic contact between parts under rolling friction have been studied. For this purpose, a known friction model based on the generalized Eyring equation and taking into account the phenomenon of oil film self-heating has been used. The fact that a correct description of friction curves using this model is possible has been confirmed by comparison with published experimental data. Conditions are revealed, under which in the thermal zone of friction curves, despite a decrease in the friction coefficient, an increase in friction power loss continues. It is shown that the bearing seizing hazard occurs when the bearings operate in a thermal zone of the friction curves. A concept of critical slide–roll ratio that represents a boundary of the thermal zone of friction curves has been introduced, and its dependence on the contact pressure and temperature has been studied for PAO1 grade polyalphaolefin oil in the temperature range of 40–100°C and for MN-7.5u grade oil in the range of 60−140°C. It is shown that the critical sliding-to-rolling ratio increases with decreasing contact pressure in the bearing, as well as with increasing oil temperature. It is concluded that the conditions of contact between the rollers and the inner ring promote an increase in friction power loss to a greater extent than the conditions of contact between the rollers and the outer ring. This indicates a higher seizing hazard in the case of the inner ring than in the case of the outer ring, which is confirmed by the statistics of rolling bearing failures. In order to prevent seizing in bearings, it is necessary to provide a margin with respect to critical sliding at the bearing design stage.