Accession Number:



Analysis of Film Thickness Effect in Slow-Speed Lightly-Loaded Elasto- Hydrodynamic Contacts. Part 2. Measurement of Film Thicknesses in Vacuum

Descriptive Note:

Final rept. 1 Jul 1974-15 Jun 1975

Corporate Author:


Report Date:


Pagination or Media Count:



This report presents a summary of the second years effort in a two- year program to study the influence of oil film thickness on bearing-lubricant life expectancy in despin mechanical assembly-type bearings operating in vacuum. Results of elastohydrodynamic film thickness measurements made by the optical interference technique in a SwRI optical tester are presented for seven oils, some of which have been employed in actual space flight hardware. These results show that the special oils formulated for vacuum use behave in a manner similar to ordinary straight mineral oils. Extensive experimental EHD film thickness data were obtained for DMA-type bearings operating in a vacuum and lubricated with various oils, and these results are presented and discussed. These film thickness measurements were made using a race displacement technique developed during the first years work at SwRI. The measurements show that, in general, lubricant starvation occurs in the bearings with the result that the EHD film thicknesses are less than those predicted by the theoretical equations for flooded EHD lubrication. The results from long-term tests with DMA-type bearings operating in vacuum are also presented. Two bearing failures occurred and these failures are attributed to problems associated with lubrication of the interfaces between the retainer and the other bearing components. 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.

Subject Categories:

  • Lubricants and Hydraulic Fluids
  • Machinery and Tools

Distribution Statement: