Analysis of Film Thickness Effect in Slow-Speed Lightly-Loaded Elastohydrodynamic Contacts. Part III. Experimental Measurement of Lubricant Film Thickness.

摘要

This report presents a summary of a program conducted to study experimentally the factors contributing to the formation and maintenance of an adequate elastohydrodynamic oil film thickness in bearings operating in space hardware. Another objective of the study was to investigate the influence of the oil film thickness on bearing-lubricant life expectancy in typical despin mechanical assembly-type bearings operating in vacuum. Results of elastohydrodynamic film thickness measurements for DMA-type bearings operating in vacuum and having various ball-retainer materials as well as different retainer/bearing processing variables are presented and discussed. Also, the effects of frequency and extremes of temperature variation on these bearings are presented. Model studies using an EHD optical tester to perform fully flooded and starved lubrication experiments are also presented and discussed. The results from long-duration tests with DMA-type bearings having ball-piloted retainers and operating in vacuum are also presented. There were no long-term bearing failures and examination of the bearings after test termination reveals that substantially full EHD lubrication (not flooded, but separation of bearing surfaces) at the ball-race contacts apparently prevailed for the duration of the tests. (Author)