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  • 1
    facet.materialart.
    Unknown
    Some effects of composition on friction and wear of graphite-fiber-reinforced polyimide liners in plain spherical bearings (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Oscillating, plain spherical bearings with graphite-fiber-reinforced polyimide (GFRPI) liners were tested for friction and wear from 25 to 315 C. A condensation polymer was compared with an addition polymer, and a high-modulus fiber was compared with a lower cost, low-modulus fiber. All polymer-fiber combinations gave friction coefficients from 0.05 to 0.18 and low wear. Adding CdO and CdI2 reduced the wear of degassed bearings in dry air. These additives were not needed when the bearing liners contained adsorbed moisture. Although, at 25 C, MoS2 reduced the friction and wear of the base composite at unit loads above 70,000,000 N/m squared (10,000 psi), it had no beneficial effect at lighter loads.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-1229 , E-9296
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Plasma-sprayed, self-lubricating coatings for use from cryogenic temperatures to 870 deg C (1600 deg F) (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A plasma-sprayed coating is described with good lubricating properties over a wide temperature range. The coating, designated NASA LUBE PS101, contains silver, nichrome, calcium fluoride, and an oxidation protective glass. Oscillating tests were conducted of self-aligning, plain cylindrical bearings, in which the bore was lined with 0.025 cm (0.010 in.) thick coatings of PS101; these were conducted at a radial load of 3.5 x 10 to the 7th power N/sq m (5000 psi) in nitrogen gas at -107 C (-160 F), in vacuum at room temperature, and in air from room temperature to 870 C (1600 F). Friction coefficients were less than 0.25 in all cases and wear rates were low. The coating is not brittle, and it has adequate oxidation resistance in air to at least 870 C.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-X-71798 , E-8476
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Surface roughness effects with solid lubricants dispersed in mineral oils (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The lubricating effectiveness of solid-lubricant dispersions are investigated in both point and line contacts using surfaces with both random and directional roughness characteristics. Friction and wear data obtained at relatively low speeds and at room temperature, indicate that the existence of solid lubricants such as graphite, MoS2, and PTFE in a plain mineral oil generally will not improve the effectiveness of the oil as a lubricant for such surfaces. Under boundary lubrication conditions, the friction force, as a function of time, initially depends upon the directional roughness properties of the contacting surfaces irrespective of whether the base oil or dispersions are used as lubricants.
    Keywords: MECHANICAL ENGINEERING
    Type: ASLE PREPRINT 83-LC-4C-1
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Performance of PTFE-lined composite journal bearings (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: (Previously announced in STAR as N82-17263)
    Keywords: MECHANICAL ENGINEERING
    Type: ASLE PREPRINT 82-AM-1A-1 , Annual Meeting; May 10, 1982 - May 13, 1982; Cincinnati, OH
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Graphite-fiber-reinforced polyimide liners of various compositions in plain spherical bearings (1978)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A plain spherical bearing design with a ball diameter of 28.6 mm, a race length of 12.7 mm, and a 1.7-mm-thick, molded composite liner was evaluated. The liner material is a self-lubricating composite of graphite-fiber-reinforced polyimide resin (GFRPI). The liner is prepared by transfer molding a mixture of one part chopped graphite fiber and one part partially polymerized resin into the space between the bearing ball and the outer race and then completing the polymerization under heat and pressure. Several liner compositions were evaluated: two types of polyimide, condensation and addition; two types of graphite fiber, low and high modulus; and four powder additives - cadmium oxide, cadmium iodide, graphite fluoride, and molybdenum disulfide. The bearings were oscillated + or - 15 deg at 1 Hz for 20 kilocycles under a radial unit load of 29 MN sq m (4200 psi) in dry air at 25, 200, or 315 C. Both types of fiber and polyimide gave low friction and wear. A simple equation was developed to fit the wear-time data and adequately predicted wear to 100 kilocycles.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-78908 , E-9296 , Intern. Conf. on Solid Lubrication; Aug 14, 1978 - Aug 18, 1978; Denver
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    NASA TECHNICAL REPORTS
  • 6
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    Some load limits and self-lubricating properties of plain spherical bearings with molded graphite fiber reinforced polyimide liners to 320 C (1978)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Plain spherical bearings with molded liners of self-lubricating graphite fiber-polyimide composite were developed and their dynamic load capacities were determined. Liners were prepared by transfer molding a prepolymer resin-fiber mix into the space between the ball and outer race, the completing polymerization under heat and pressure. Bearing dynamic load capacities were in excess of 140 MPa (20,000 psi) from room temperature to 260 C and about 70 MPa (10,000 psi) at 320 C. Friction coefficients were about 0.20 at room temperatures and light loads and tended to decrease with increasing temperatures and loads to about 0.15. Thermal expansion of the liner at uniform bearing temperatures of 200 C or higher produced a bearing preload which could be alleviated by providing an initial internal diametral clearance of 0.05 to 0.10 mm.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-78935 , E-9678 , Joint Lubrication Conf.; Oct 24, 1978 - Oct 26, 1978; Minneapolis
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    NASA TECHNICAL REPORTS
  • 7
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    Tribological properties of self-lubricating fluoride-metal composites to 900 deg C /1650 deg F/ - A review and some new developments (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Keywords: MECHANICAL ENGINEERING
    Type: ASME PAPER 74-LUB-2 , 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
  • 8
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    Dynamics of solid lubrication as observed by optical microscopy (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A bench metallograph was converted into a 'micro contact imager' by the addition of a tribometer employing a steel ball in sliding contact with a glass disk. The sliding contact was viewed in real time by means of projection microscope optics. The dynamics of abrasive particles and of solid lubricant particles within the contact were observed in detail. The contact was characterized by a constantly changing pattern of elastic strain with the passage of surface discontinuities and solid particles. Abrasive particles fragmented upon entering the contact, embedded in one surface and scratched the other; in contrast, the solid lubricant particles flowed plastically into thin films. The rheological behavior of the lubricating solids gave every appearance of a paste-like consistency within the Hertzian contact.
    Keywords: MECHANICAL ENGINEERING
    Type: ASLE PREPRINT 76-LC-1B-4 , Lubrication Conference; Oct 05, 1976 - Oct 07, 1976; Boston, MA; US
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Dynamic load capacities of graphite fiber: Polyimide composites in oscillating plain bearings to 340 C (650 F) (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Load capacities were determined for plain spherical bearings with self-lubricating spherical elements of graphite-fiber-reinforced-polyimide, and for plain cylindrical bearings with thin-wall liners of the composite in the bearing bores. Composites consisted of a 1-to-1 weight ratio of graphite fibers and polyimide. Oscillation was at an amplitude of + or - 15 deg at a frequency of 1 hertz. Bearings with composite ball material had a load capacity of approximately 69 MN/sq m (10 000 psi) at room temperature 25 MN/sq m (3600 psi) at 340 C (650 F). Bearings with thin-wall composite liners had much higher load capacities of 280 MN/sq m (40 000 psi) at room temperature amd 240 MN/sq m (35 000 psi) at 320 C (600 F). Friction coefficients were in the range of 0.12 to 0.19. The addition of 10 wt.% graphite fluoride solid lubricant to the composition of the thin-wall liners reduced friction coefficients into the range of 0.10 to 0.12.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TN-D-7880 , E-8118
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Friction and wear of plasma-sprayed coatings containing cobalt alloys from 25 deg to 650 deg in air (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Four different compositions of self-lubricating, plasma-sprayed, composite coatings with calcium fluoride dispersed throughout cobalt alloy-silver matrices were evaluated on a friction and wear apparatus. In addition, coatings of the cobalt alloys alone and of one coating with a nickel alloy-silver matrix were evaluated for comparison. The wear specimens consisted of two, diametrically opposed, flat rub shoes sliding on the coated, cylindrical surface of a rotating disk. Two of the cobalt composite coatings gave a friction coefficient of about 0.25 and low wear at room temperature, 400 and 650 C. Wear rates were lower than those of the cobalt alloys alone or the nickel alloy composite coating. However, oxidation limited the maximum useful temperature of the cobalt composite coating to about 650 C compared to about 900 C for the nickel composite coating.
    Keywords: MECHANICAL ENGINEERING
    Type: ASLE PREPRINT 80-AM-6C-2 , Annual Meeting; May 05, 1980 - May 08, 1980; Anaheim, CA
    Format: text
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    NASA TECHNICAL REPORTS
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