摘要:

Rolling bearings used for transporting wafers and liquid crystals in the film-forming process of semiconductor and LC panel manufacturing are required to minimize the particles (originating from both lubricant and bearing material) they generate while in operation. The research reported in this paper focuses on the particle generation under different rotational conditions of ball bearings and ball screws coated with various solid lubricants and operating in a vacuum environment. The results of the tests indicated that a specially composed and applied polytetrafluoroethylene (PTFE) coating was superior in minimizing particle generation by ball bearings and ball screws. Observation of the bearing interior surfaces indicated that particle generation is primarily caused by wear of cage-pocket surfaces, while sudden and large increases in wear are the result of the balls making direct surface-to-surface contact with the raceways and cages due to erosion of the solid lubricant coatings.Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982203

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This paper presents the establishment of a parametric model describing the amount of metalcutting fluid departing from the machining area and permeating into the shop floor environment. The analysis focuses on the process of horizontal turning with overhead fluid jet application. The portion of fluid that leaves the machining area and does not land on the fluid pen is considered as the permeating cutting fluid that contributes to environmental contamination. The quantitative model developed in this analysis accounts for three primary mechanisms of which metalworking fluid enters into and endangers the shop floor environment. The three primary mechanisms are the evaporation of fluid resulting from high temperature in the cutting zone, spin-off of fluid from the workpiece due to rotational motion and the splash due to kinetic energy from fluid-workpiece impact. Process parameters and fluid properties found to affect these mechanisms include part diameter, rotation speed, fluid velocity, fluid viscosity and tool temperature. The validity of the model has been evaluated experimentally under both conditions of stationary and rotational work-piece.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Toronto, Ontario, Canada, October 26–28, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982204

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The feasibility of supporting a turbocharger rotor on air foil bearings is investigated based upon predicted rotordynamic stability load accommodations, and stress considerations. It is demonstrated that foil bearings offer a plausible replacement for oil-lubricated bearings in diesel truck turbochargers. Also, two different rotor configurations are analyzed and the design is chosen which best optimizes the desired performance characteristics. The method of designing machinery for foil bearing use and the assumptions made are discussed.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Toronto, Ontario, Canada, October 26–28, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982205

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

One uses atomic force microscopy to explore the surface morphology, frictional characteristics (i.e., friction mapping) and surface adhesive forces of boric acid-treated aluminum surfaces. In earlier studies, boric acid was shown to be an effective solid lubricant providing 0.02 to 0.1 friction coefficients to the sliding surfaces of metallic and ceramic materials. In this study, the authors mainly focused on the friction and wear behavior of cleaved single crystals of boric acid. Tests were performed on uncoated and boric acid-coated surfaces of aluminum substrates, as well as the bulk boric acid material. The nano-scale wear of the boric acid crystals manifested itself in the displacement of atomic planes which, in turn, resulted in the formation of the worn area grown by a spiral-growth mechanism. In addition, new crystals in the vicinity of the sliding contact areas were formed. These crystals formed by a spiral dislocation mechanism. The nanoscale friction measurements showed that the friction coefficient of a Si3N4tip against the boric acid single crystal, was in the range of 0.07 to 0.13, depending on the sliding direction with respect to the crystallographic orientation. The friction coefficients of the boric acid-coated aluminum substrates varied between 0.11 and 0.19. While these values were consistent with earlier findings and further demonstrated the lubricity of boric acid, they were higher than the previous measurements (i.e., 0.011–0.1) obtained on a pin-on-disk machine using steel or ceramic pins. An explanation is provided for this phenomenon.Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982206

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Analytical models are derived for the viscosity and the density of aerated oil in fluid-film bearings. The models account for the effects of fluid-film pressure, fluid-film geometry, oil aeration rate and bubble surface tension. The viscosity model confirms experimental evidence that the viscosity of aerated oil can be significantly higher than for non-aerated oil. The new models can be used with Reynolds' equation to predict the behavior of fluid-film bearings lubricated by aerated oil.

ISSN:1040-2004    

DOI:10.1080/10402009908982207

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The requirements placed on lubricating oils at the top ring reversal point are becoming increasingly severe due to recent changes in engine technology, most of which are driven by emissions regulations. As a result, revised engine tests to evaluate cylinder liner scuffing are being introduced to engine oil specifications. Despite the high cost and generally poor repeatability of full-scale engine data, no laboratory screener test is commercially available. In the present study, various lubricant characteristics were correlated with the level of scuffing in the Detroit Diesel 6V92TA engine test. Good initial agreement was obtained with lubricant volatility measured at 525°C, which is predicted to be the approximate contact temperature under the most extreme conditions likely to exist during normal operation.

ISSN:1040-2004    

DOI:10.1080/10402009908982208

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Porous anodic films containing molybdenum disulfide precursors were developed for self-lubricating purposes on aluminum by an initial anodizing and a subsequent re-anodizing process. The self-lubricating films were then examined with respect to the morphology, microstructure, and composition of the anodic film material and the lubricant, using X-ray diffraction, electron microscopy, energy dispersive X-ray analysis and X-ray photo-electron spectroscopy. The dry sliding wear of aluminum supporting such self-lubricating films was significantly reduced, as a result of greatly reduced coefficients of friction. The enhanced lubricity, due to the MoS2precursors contained within the porous anodic film, leads to wear mode changes from severe abrasive and adhesive wear for uncoated aluminum, to a mild film fatigue wear, for aluminum supporting the self-lubricating anodic films. The wear mechanism change is suggested by the wear and friction curves, as well as confirmed by wear track morphology.

ISSN:1040-2004    

DOI:10.1080/10402009908982209

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This paper presents measured results for the eccentricity ratios for two tilting-pad journal bearing. Comparison between a bearing with spherical seated ball and socket pad pivots and one with line contact rocker-back pad pivots is made. The bearings have a length to diameter ratio of 0.75, offset ratios of 0.50, preloads of about 0.320, a journal diameter of 70 mm and a radial machined pad clearance of 113.0 μm. Measurements were made for a range of speed-load conditions encompassing a Sommerfeld number range of 0.1 to 2.0. Comparison of the eccentricity magnitude for the two bearing agreed within uncertainty levels. For the bearing with rocker-back pad pivots, the journal attitude angle with respect to the applied load direction is nearly zero. Attitude angles range from 13° to 33° for the bearing with spherical seated ball and socket pad pivots. The deviation from zero attitude angle for this bearing increased with increasing speed. A hypothesis for larger pad pivot friction in the ball and socket pivot is presented to explain the variation in attitude angle between the two bearings.Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982210

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The dynamics and stability of tapered air bearing sliders used for computer hard disk drive magnetic recording heads is examined using analytical methods. Lubrication theory is applied to determine the lift on the slider from the Reynolds equation in the limit of large bearing number. The dynamics of the slider are given by a nonlinear integro-differential equation. Linear stability analysis of this model yields valuable insight into the behavior of the slider. Most significantly, it is found that convective effects can not be neglected and yield either damping or instability depending on the slider configuration. This analysis is also applied to determine the response of the slider motion due to deviations in the disk surface.

ISSN:1040-2004    

DOI:10.1080/10402009908982211

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The surface temperature of contact elements is one of the most important factors that influences the performance and life of tribological systems. Heat-pipe cooling seems to be a promising means for enhanced heat transfer. The heat input at the surface and the heat pipe as a heat sink represent a system of heat source/heat sink (HSHS). In this paper, the function of the heat pipe is mathematically described and the heat-transfer characteristics of the HSHS system are investigated. A semi-empirical model is developed to shed some light on the surface flash temperature control employing the HSHS system. Both steady-state and transient analyses show that heat pipes can be employed to reduce the flash temperature effectively. The possibility of applying this concept to composite materials is also analyzed.Presented at the 52nd Annual Meeting in Kansas City, Missouri May 18–22, 1997

ISSN:1040-2004    

DOI:10.1080/10402009908982212

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor