Sliding Contacts in Rolling Bearings

“Smearing” or “galling” type failures similar to those which occur at sliding contacts in rolling bearings were studied using a number of lubricants in a two-ball sliding tester. The rolling speed, sliding speed, oil flow rate, ambient temperature, rate of increase in load, and ball surface roughness were found to influence the load at which smearing occurred. The results suggest that an elastohydrodynamic film of lubricant plays a major role in determining the load at which smearing occurs. This conclusion was supported by measurements of the oil film thickness using an X-ray transmission technique. Extrapolation from thermocouple measurements indicated that the onset of smearing was not characterized by a constant critical value of the maximum contact temperature.