摘要:

An optical microscope was used to study the lubrication and failure mechanisms of rubbed (burnished) MoS2films applied to three substrate surface finishes—polished, sanded, and sandblasted—as a function of sliding distance. The lubrication mechanism was the plastic flow of thin films of MoS2between flat plateaus on the rider and on the metallic substrate. If the substrate were rough, flat plateaus were created during “run-in” and the MoS2flowed across them. Wear life was extended by increasing surface roughness since valleys in the roughened substrate served as reservoirs for MoS2and a deposit site for wear debris. In moist air, the failure mechanism was the transformation of metallic-colored MoS2films to a black, powdery material that was found by X-ray diffraction to consist primarily of â-iron and MoO3powders. In dry argon, the failure mechanism was the gradual depletion of the MoS2film from the contact region by transverse flow. Analysis of the wear debris on the wear track at failure showed it consisted mainly of â-iron and some residual MoS2molybdenum oxides were found.Presented at the 36th Annual Meeting in Pittsburgh, Pennsylvania, May 11–14, 1981

ISSN:0569-8197    

DOI:10.1080/05698198208983076

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The “flash-temperature” concept is a means of accounting for the local maxima of frictional heat flux. This paper reviews how such maxima are often many times the apparent rubbing interface average hear flux. The physical and mathematical constraints on the flash-temperature concept are considered, along with the parametric sensitivities involved. In particular, a characteristic nondimensional rub time and nondimensional surface temperature are proposed to gauge the degree of flash-temperature effect in various rubbing configurations. As an aid to understanding the present result and a means of investigating this phenomenon further in the future, a computer program is documented which solves for nondimensional flash temperature vs time for an arbitrary set of uniform asperity sizes and spacing, rubbing-element material properties, and rub boundary conditions.Presented at the 36th Annual Meeting in Pittsburgh, Pennsylvania, May 11–14, 1981

ISSN:0569-8197    

DOI:10.1080/05698198208983077

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The wear of rigid polyvinyl chloride (PVC), was measured in a pin-on-disk apparatus as a function of PVC average number molecular weight (70 000 and 40 000), steel counterface roughness (0.15 to 1.27 μm Ra), and sliding speed (0.1 to 1.4 m/s). The lower molecular weight PVC had the higher wear at all test conditions except 1.4 m/s speed and 1.27 μm Ra. At this condition, the calculated interface temperature exceeded the glass transition temperature of 74°C for PVC. The wear rate increased for increases in both surface roughness and sliding speed. These results were explained in terms of the increased penetration of the steel asperities into the PVC necessitated by changes in these two factors.Presented at the 36th Annual Meeting in Pittsburgh, Pennsylvania, May 11–14, 1981

ISSN:0569-8197    

DOI:10.1080/05698198208983078

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A Hertzian contact is lubricated with dispersed graphite in mineral oils under boundary lubrication conditions. The contacts are optically observed under pure rolling, combined rolling and sliding, and pure sliding conditions. The contact is formed with a steel ball on the flat surface of a glass disk. Photomicrographs are presented which show the distribution of the graphite in and around the contact. In addition, friction and surface damage are shown for conditions when the base oils are used alone and when graphite is added to the base oils. Under pure rolling and combined rolling and sliding conditions, it is found that, for low speeds, a graphite film can form which will separate the contacting surfaces. In contrast, under pure sliding conditions, graphite accumulates at the inlet and sweeps around the contact, but very little of graphite passes through the contact. The accumulated graphite appears to act as a barrier which reduces the supply of oil available to the contact for boundary lubrication. Friction data show no clear short-term beneficial or detrimental effect caused by addition of graphite to the base oil. However, during pure sliding, more abrasion occurs on the polished balls lubricated with the dispersion than on those lubricated with the base oil alone. All observations were for the special case of a highly polished ball on a glass surface and may not be applicable to other geometries and materials, or to rougher surfaces.Presented at the 36th Annual Meeting in Pittsburgh, Pennsylvania, May 11–14, 1981

ISSN:0569-8197    

DOI:10.1080/05698198208983079

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The dynamics of MoS2particles in a mineral oil dispersion are studied in the same manner as reported in Part I for graphite dispersions. A Hertzian contact consisting of a steel ball in contact with a glass disk is lubricated with MoS2dispersions and observed by optical microscopy at various. slide/roll conditions. In general, the behavior of MoS2and graphite are similar. That is, the solids lend to enter the contact and form a film on the contacting surfaces whenever a rolling component of motion is used, but solid particles seldom enter the contact during pure sliding. MoS2has more pronounced plastic flow behavior than graphite. However, the polished steel ball is more readily scratched by MoS2than by graphite. Under the conditions of these studies, lower friction and wear are observed with pure oil rather than with the dispersions. However, under other conditions (such as different contact geometry or rougher surfaces), the solid-lubricant dispersions might be beneficial.Presented at the 36th Annual Meeting in Pittsburgh, Pennsylvania May 11–14, 1981

ISSN:0569-8197    

DOI:10.1080/05698198208983080

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Rolling-fatigue tests of 0.45 percent carbon steel rollers were carried out using a four-roller-type rolling-contact fatigue tester. Tangential traction and surface roughness of the harder mating rollers were varied and their effect was studied. The results of the study indicate that the fatigue life decreases when traction is applied in the same direction as that of rolling. When the direction of traction is reversed, the life increases over that obtained with zero traction. The roughness of harder mating rollers also has a marked influences on life. The smoother the mating roller, the longer the life. Microscopic observation of specimens revealed that the initiation of cracks during the early stages of life is more strongly influenced by the surface roughness, while the propagation of these cracks in the latter stages is affected mainly by the tangential traction.Presented at the 36th Annual Meeting in Pittsburgh, Pennsylvania, May 11–14, 1981

ISSN:0569-8197    

DOI:10.1080/05698198208983081

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

In an attempt to put irreducible representation of symmetry point group to use, the ligand group orbit of some transition metal dichalcogenides, the compounds TX2(T = Ti, Zr, Hf, V, Nb, Mo, W; X = S, Se) and their energies were evaluated. The level scheme of molecular orbitals of the TX2compounds and a simple model for bond structure is qualitatively given. The relationship between the structure of these compounds and their lubrication performance is discussed. It is indicated that pile-up type and symmetry type, configurations in which electrons occupy the d orbital, provide better lubrication performance.Presented at the 36th Annual Meeting in Pittsburgh, Pennsylvania, May 11–14, 1981

ISSN:0569-8197    

DOI:10.1080/05698198208983082

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Rolling contact fatigue life under debris- (or foreign particle-) contaminated lubrication is less than one-tenth the life under non-contaminated lubrication when the contaminating debris is hard, large particles (0.1 mm). A small “crevasse-type” crack initiates at the forward or backward side of a debris Particle indentation and grows into fatigue flaking. The size of the initial crack can be described by a parameter of the material called “crack sensitivity” in this paper. Relation between heat treatment conditions and the crack sensitivity of the ball bearing steel was investigated. The heat treatment which decreased crack sensitivity increased rolling contact fatigue life significantly not only under debris contaminated lubrication but also under noncontaminated lubrication.Presented at the 36th Annual Meeting in Pittsburgh, Pennsylvania, May 11–14, 1981

ISSN:0569-8197    

DOI:10.1080/05698198208983083

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The stability of a rigid rotor mounted in three-lobe bearings is theoretically studied for which the preload factor, offset factor, and load orientation are systematically varied. Rigid-rotor stability maps are presented. Results indicate that bearings with offset factors of 0.1 or less and moderate preload factors are often more stable than those with larger offset factors. Results also indicate that, for a given preload and load orientation, a particular offset factor exists which produces minimum stability (such bearing geometries should be avoided). Finally, increasing the preload factor was found to increase the rigid-rotor stability.Presented at the 36th Annual Meeting in Pittsburgh, Pennsylvania, May 11–14, 1981

ISSN:0569-8197    

DOI:10.1080/05698198208983084

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

95/5 hydraulic fluids (95 percent water, 5 percent additives) have a low viscosity, essentially that of water. In certain kinds of pumps, as the pressure is increased, the low viscosity of the 9515 fluids causes excessive internal leakage and loss of efficiency. In an effort to improve the efficiency of equipment and reduce leakage when using the 95/5 fluids, a polyoxyalkylene thickening agent was added to the 95/5 fluid. Flow rates in a pump system, shear stability, low shear viscosities, and effective high shear viscosities were measured for high-water fluids containing this thickening agent. Flow rates of an unthickened high-water fluid and of a water glycol fluid were determined in the same system for comparison. The thickened high-water fluid showed great improvements in volumetric efficiency over the unthickened high-water fluid. For example, at 4200 kPa pressure (600 psi) a 95/5 unthickened fluid had a 45 percent volumetric efficiency while a thickened 90/10 fluid had a volumetric efficiency of 78 percent in the same vane pump.Presented at the 36th Annual Meeting in Pittsburgh, Pennsylvania, May 11–14, 1981

ISSN:0569-8197    

DOI:10.1080/05698198208983085

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor