The operation of equipment in space has required a new evaluation of lubricants. To evaluate these lubricants, Lockheed Missiles and Space Company has conducted a test program of operating lubricated, instrument-size ball bearings in pressures of 10−7 to 10−9 torr.
Four classes of lubricants have been tested in the vacuum pressure range mentioned above. Bearings using the most successful of the oil and grease lubricants tested have operated continuously for over 1 yr. The most promising tests using special retainer materials have been 3 to 6 months in duration. Tests using dry-film lubricants have shown poor reproducibility and short life-times of only about 3 months.
Polymer jackets play an important protective role in distribution cabling by providing structure and resistance to moisture, heat, and exposure to harmful chemicals. Current methods of structural assessment, such as elongation at break (E-at-B), are inherently destructive. While other non-destructive methods such as indenter evaluation are available, they are not suitable for in-service use. We propose that second harmonic generation (SHG) could provide a non-destructive means of characterizing the aging of chlorosulfonated polyethylene (CSPE) cable jackets. SHG was used to study cables previously aged and characterized by the Electric Power Research Institute (EPRI). Comparative data between the SHG results and indenter modulus tests suggest that SHG can be used to qualitatively differentiate between minimally and significantly aged CSPE cable jackets. The results of this proof-of-concept study suggest additional work that could be done to better understand the mechanisms of the aging of CSPE cable jackets and how SHG could be used to monitor the aging process.
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