CORRELATION OF ASPERITY CONTACT-TIME FRACTION WITH ELASTOHYDRODYNAMIC FILM THICKNESS IN A 20-MILLIMETER-BORE BALL BEARING

摘要

Elastohydrodynamic film thicknesses and asperity contact-time fractions were measured for a 20-mm-bore ball bearing by using the capacitance and conductance techniques. The bearing was thrust loaded to 90, 445, and 778 N (20, 100, and 175 lb). The corresponding maximum stresses on the inner race were 1. 28, 2. 09, and 2. 45 GPa (185 000, 303 000, and 356 000 psi). The test speed ranged from 400 to 15 000 rpm. The test bearing was mist lubricated with an MIL-L-23699A turbine oil. The temperature was 27° C (80° F). The experimental results were correlated to give the percent film (no-contact-time fraction) as a function of measured film thickness. Measurements were made for three test series that represented the test bearing in various conditions of run-in. The measurements show that the percent film changes with bearing run-in time. The experimental results agreed well with theoretical predictions based on surface trace analysis for a new bearing. For the run-in state, they agreed with previously reported experimental results. The results show that asperity contact existed at a film thickness-roughness ratio A of 6. 0 or less for a new bearing. After run-in, no asperity contact occurred at a A of 3. 5 or greater.