Accession Number : AD0675205

Title :   PRESSURE EFFECTS ON THE FRICTION COEFFICIENTS OF THIN-FILM SOLID LUBRICANTS.

Descriptive Note : Interim rept.,

Corporate Author : NAVAL RESEARCH LAB WASHINGTON D C

Personal Author(s) : Bowers,R. C. ; Zisman,W. A.

Report Date : 22 JUL 1968

Pagination or Media Count : 26

Abstract : To calculate the coefficient of fraction mu for thin solid films, the shear strength of the film material at the existing pressure must be known. Loads great enough to produce plastic flow of the film may still be well below the elastic limits of the substrate and superstrate. Measurements with paraffin films have revealed that at such loads the film distributes the pressure over the entire contact area; in the absence of a continuous solid film, pressure is concentrated at highly localized areas of asperity contact. Appropriate equations were derived to predict mu for both elastic and plastic substrate deformation for a spherical rider traversing a plane surface. Values of K1 and N for gold, silver, indium, lead, and molybdenum disulfide have been calculated from the shear strength-vs-pressure data of Bridgman, as well as of Boyd and Robertson. Sample calculations of mu were made for thin films of these materials under several specific conditions. These calculated values of mu agreed well with experimental values for materials for which experimental data were available (paraffin, gold, and MoS2). It is concluded that to advance theoretical and applied research in dry-film lubrication, shear strength-vs-pressure data should be obtained for a greater variety of materials, including the indicated organic polymers and various inorganic solids. (Author)

Descriptors :   (*LUBRICANTS, FILMS), FRICTION, PRESSURE, MOLYBDENUM COMPOUNDS, SULFIDES, WAXES, GOLD, SILVER, INDIUM, LEAD(METAL), LOADS(FORCES), SHEAR STRESSES

Subject Categories : Solvents, Cleaners, and Abrasives

Distribution Statement : APPROVED FOR PUBLIC RELEASE