INVESTIGATION OF FILM THICKNESS OF GREASE-LUBRICATED THRUST BEARING: FROM BALL-ON-DISC TO BEARING

Rolling element bearings lubricated by greases represent the most used mechanical components in industry, thus the total volume of energy required to overcome their friction is enormous. Even small improvements can provide considerable savings. To reach these improvements, it is necessary to understand all the processes in the bearing, and especially those that take place in contacts of rolling elements. So far, most of the research was done on tribometers employing a ball-on-disc configuration. Tests on such devices are easy to perform but differ from conditions of actual bearings in some important aspects such as a contact geometry, presence of cage, number of contacts, spin motion of rolling elements, or action of centrifugal and capillary forces. The aim of this experimental study is to refer about film thickness during the initial running phase of simulated thrust rolling bearing and to reveal some patterns of lubricant behaviour for different conditions and greases. Measurements were carried out on unique apparatus of simulated thrust rolling bearing using optical methods with high speed camera. Results showed that the ball-on-disc configuration does not completely correspond to behaviour of actual bearings, mostly in terms of starvation and replenishment of grease. Multiple contacts in succession of simulated bearing do not tend to starve so rapidly and seriously during experiments as is presented in literature for ball-on disc configuration under similar conditions.