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  • 11
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    Enhancement of perfluoropolyether boundary lubrication performance: I. Preliminary results (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A ball bearing simulator operating under starved conditions was used to evaluate the boundary lubrication performance of a perfluoropolyether (PFPE) Krytox 143 AB. Several approaches to enhance boundary lubrication were studied. These included: (1) soluble boundary additives, (2) bearing surface modifications, (3) 'run-in' surface films, and (4) ceramic bearing components. In addition, results were compared with two non-perfluorinated liquid lubricant formulations. Based on these preliminary tests, the following tentative conclusions can be made: (1) substantial improvements in boundary lubrication performance were observed with a beta-diketone boundary additive and a tricresyl phosphate (TCP) liquid surface pretreatment; (2) the use of rough Si3N4 balls (Ra = 40 micro-in) also provided substantial improvement but with concomitant abrasive wear; (3) marginal improvements were seen with two boundary additives (a phosphine and a phosphatriazine) and a neat (100%) fluid (a carboxylic acid terminated PFPE); and surface pretreatments with a synthetic hydrocarbon, a PTFE coating, and TiC coated 440C and smooth Si3N4 balls (R(sub a) less than 1 micro-in); and (4) two non-PFPE lubricant formulations (a PAO and a synthetic hydrocarbon) yielded substantial improvements.
    Keywords: NONMETALLIC MATERIALS
    Type: NASA-TM-106937 , E-9665 , NAS 1.15:106937 , the American Chemical Society; Mar 13, 1994 - Mar 18, 1994; US
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 12
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    Optical analysis of ball bearing starvation (1970)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Optical measurement of oil film thickness in elastohydrodynamic rolling point contact of ball bearing
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TM-X-52869 , PROPOSED FOR PRESENTATION AT LUBRICATION CONF.; Oct 12, 1970 - Oct 15, 1970; CINCINNATI, OH; UNITED STATES
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    NASA TECHNICAL REPORTS
  • 13
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    Elastohydrodynamic film thickness measurements of artificially produced surface dents and grooves (1978)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Elastohydrodynamic (EHD) film thickness measurements using optical interferometry were made of artificially produced dents and grooves under rolling and sliding conditions. These measurements are compared to stylus traces of the dent and groove profiles to determine the local deformation associated with micro-EHD pressure generation. The surface geometry associated with the dents and grooves became intimately involved in the lubrication process itself, creating local pressure variations that substantially deformed the local surface geometry, particularly under sliding conditions. The rolling results implied surface initiated fatigue, and the sliding results showed clearly the EHD surface interactions that must occur prior to scuffing failure.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-78949 , E-9693 , Joint Lubrication Conf.; Oct 24, 1978 - Oct 26, 1978; Minneapolis, MN; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 14
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    Influence of debris dent on EHD lubrication (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Film thickness measurements associated with a debris dent have been made with interferometry under static and dynamic conditions. The presence of a debris dent alters the shape of the inlet region so that the local film thickness at the leading edge of the dent can become substantially lower than the trailing edge. The pressure modifications associated with these local EHD effects are in line with the frequent occurrence of surface initiated fatigue spalls originating at the trailing edge of debris dents. The effectiveness of the EHD mechanism in reducing the stress concentrations at the shoulders of the dent is related to inlet dimensions and dent size.
    Keywords: MECHANICAL ENGINEERING
    Type: ASLE PREPRINT 76-LC-1A-3 , Lubrication Conference; Oct 05, 1976 - Oct 07, 1976; Boston, MA; US
    Format: text
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  • 15
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    Influence of debris dent on EHD lubrication (1975)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Film thickness measurements associated with a debris dent have been made with interferometry under static and dynamic conditons. The presence of a debris dent alters the shape of the inlet region so that the local film thickness at the leading edge of the dent can become substantially lower than the trailing edge. The pressure modifications associated with these local elastohydrodynamic (EHD) effects are in line with the frequent occurrence of surface initiated fatigue spalls originating at the trailing edge of debris dents. The effectiveness of the EHD mechanism in reducing the stress concentrations at the shoulders of the dent is related to inlet dimensions and dent size.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-X-73457 , E-8690 , Joint Lubrication Conf.; Oct 05, 1976 - Oct 07, 1976; Boston
    Format: application/pdf
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  • 16
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    Traction and film thickness measurements under starved elastohydrodynamic conditions (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Results of traction and film thickness measurements made for a point contact geometry under starved elastohydrodynamic rolling and sliding conditions are reviewed. These results indicate that the variation of film thickness with the location of the inlet lubricant boundary under combination rolling and sliding behaves identically with that found previously under pure rolling conditions. The maximum shear rate is shown to depend on the degree of starvation and has no theoretical limit. The relative increase in traction due to starvation is influenced by thermal and fluid rheological conditions within the Hertz region.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME PAPER 74-LUB-30 , American Society of Mechanical Engineers and American Society of Lubrication Engineers, Joint Lubrication Conference; Oct 08, 1974 - Oct 10, 1974; Montreal; Canada
    Format: text
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    NASA TECHNICAL REPORTS
  • 17
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    Elastohydrodynamic film thickness measurements of artificially produced surface dents and grooves (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Elastohydrodynamic (EHD) film thickness measurements using optical interferometry have been made of artificially produced dents and grooves under rolling and sliding conditions. These measurements are compared to stylus traces of the dent and groove profiles to determine the local deformation associated with micro-EHD pressure generation. The surface geometry associated with the dents and grooves is seen to become intimately involved in the lubrication process itself, creating local pressure variations that substantially deform the local surface geometry, particularly under sliding conditions. The rolling results have implications concerning surface initiated fatigue and the sliding results show clearly the EHD surface interactions that must occur prior to scuffing failure.
    Keywords: MECHANICAL ENGINEERING
    Type: ASLE PREPRINT 78-LC-1A-1 , American Society of Lubrication Engineers and American Society of Mechanical Engineers, Joint Lubrication Conference; Oct 24, 1978 - Oct 26, 1978; Minneapolis, MN
    Format: text
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  • 18
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    Elastohydrodynamic film thickness measurements of artificially produced nonsmooth surfaces (1979)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Optical interferometry is used to measure the elastohydrodynamic (EHD) film thickness associated with artificially produced nonsmooth surfaces. The nonsmooth surfaces are produced by modifying the surfaces of highly-polished balls with irregularities in the form of multiple grooves and dents. By closely spacing these irregularities it is possible not only to produce depressions on the surface of the balls but also to generate pseudo asperities. The average roughness wavelength of this artificially-produced, nonsmooth, surface approximates the average fundamental roughness wavelength found on surfaces of some mechanical elements operating under concentrated contact. By comparing the measured film thickness profiles to the stylus traces of the irregularities, it was possible to observe the local deformations associated with micro-EHD pressure generation. In both pure rolling and pure sliding conditions the artificially-produced asperities are deformed and complete separation exists between them and the mating surface. Such findings demonstrate the importance of local surface topography and resulting micro-EHD effects on the film thickness between rough surfaces in concentrated contact. Sliding data are presented which demonstrate a severe constriction, caused by the irregularities, at the exit of the Hertzian region.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-79214 , E-9977 , Joint Lubrication Conf.; Oct 16, 1979 - Oct 18, 1979; Dayton, OH; United States
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    NASA TECHNICAL REPORTS
  • 19
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    Diagnostics of wear in aeronautical systems (1979)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Maintenance costs associated with the transmissions and drive train greatly increase the maintenance burden and failure risk. Detection measurements fall under two general categories of vibration and particle detectors. The latter are more amenable to tracking wear. Wear debris analysis can supply a great deal of information such as: particle concentration, rate of change in concentration, composition, particle size and shape, principal metals, etc. It is not economically feasible to monitor all variables. At least one role of the lubrication and wear specialist is to provide guidance in selecting the most appropriate variables to monitor.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-79185 , E-052 , State-of-the-Art Symp. on Corrosion and Wear; Jun 04, 1979 - Jun 06, 1979; Washington, DC; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 20
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    Preliminary study of the use of infrared radiation to reveal lubrication behavior (1971)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Use of infrared radiation to reveal lubrication behavior between bearing surfaces
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TM-X-67883
    Format: application/pdf
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