摘要:

A ball-on-disk adapter was employed to simulate the point contacts arising at the disk specimens with a thin layer of solid lubricant film. The disk specimens were prepared by various surface treatment methods on the substrates. Other factors affecting the properties of the lubricant films are the coating materials and the thickness of the solid lubricant films. These factors are believed to have an impact on the friction coefficient and are investigated from experiments. The experimental results reveal that the lowest friction coefficient exists in the film which is neither too thick nor too thin. The tests for the specimens with the molybdenum disulphide or the molybdenum disulphide+graphite film show that a film too thin or too thick isn't beneficial to the wear life. On the other hand, the coating film with the polytetrafluoroethylene shows the wear life is almost linearly proportional to the film thickness. For all three lubricant films, a higher friction coefficient is often accompanied with an elevation in wear coefficient. The specimens with the polytetrafluoroethylene film show the smallest friction coefficient and the lowest wear coefficient among the three solid lubricants under the same load.

ISSN:1040-2004    

DOI:10.1080/10402009908982259

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In this paper the authors present a post failure examination of the gear and disc tests reported in Ref (I) on a standard carburized steel (BS SI56), a temper resistant carburized steel (AISI M50NiL), and a carburized and nitrided temper-resistant steel (AISI M50NiL Duplex).

ISSN:1040-2004    

DOI:10.1080/10402009908982260

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A systematic study has been conducted to investigate the interactions between selected chemical compounds and silicon carbide under boundary lubrication conditions.A modified four-ball weartester was used to evaluate the additive effectiveness on silicon carbides lubricated with a paraffinic base oil containing one weight percent of additives. Friction, wear, and film morphology were observed for a range of chemical compounds containing chlorine, phosphorous, oxygen, and sulfur. Friction reduction was observed for chlorine containing compounds. At weight fraction of one percent under 40 kg load, wear reduction was obtained by all phosphorous containing compounds, polypropylene glycols, and oleic acid. At higher concentration and higher load, some sulfur containing compounds also reduced wear significantly. In general, all the effective wear reduction compounds generate films in the contact region. The films generated by phosphorous containing compounds appear to involve the iron impurity in the material.Presented at the 51st Annual Meeting in Cincinnati, Ohio May 19–23, 1996

ISSN:1040-2004    

DOI:10.1080/10402009908982261

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The effect of heat treatment, carburizing and plasma nitriding on the material-removal mechanisms and wear behavior of steels under boundary-lubricated conditions has been studied. A controlled procedure using mild abrasives under a light load was adopted in order to avoid long-term effects from severe wear in the running-in stage of pin-on-disc testing. Electron microscopy of the sliding surfaces showed that wear of the untreated steel took place by abrasive and adhesive mechanisms. Heat treatment by austenitizing, quenching and tempering (through-hardening) reduced the wear rate and carburizing produced a further reduction. The principal wear mechanisms in the both through-hardened and carburized steels was abrasive and delamination wear with adhesive wear being unimportant. Electron microscopy on cross-sections through the sliding surfaces of the carburized and through hardened steels showed extensive plasticity, cracks, and delaminated wear phenomena. The elimination of adhesive wear as a major wear mechanism is attributed to the influence of hardness on junction growth and the emergence of delamination wear to the effect of nano-crystalline carbides on fatigue life. Plasma nitriding resulted in an additional reduction in wear rate and the effective elimination of delamination wear. Electron microscopy on the plasma-nitrided steel revealed the presence of a dispersion of white layer regions, which raised the yield strength but also - resulted in micro-pitting due to a deformation mismatch with the matrix.Presented as a Society of Tribologists and Lubrication Engineers paper at the World Tribology Congress in London, United Kingdom, September 8–12, 1997

ISSN:1040-2004    

DOI:10.1080/10402009908982262

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

It is of utmost importance to know the friction loss of helical gears because they are produced quite widely used. However, basic research, e. g., load carrying characteristics of helical gears and friction loss, is extremely scarce.

ISSN:1040-2004    

DOI:10.1080/10402009908982263

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The experimental investigation was carried out for dry contact tribosystems to elucidate the ascertained, yet uncharacterized, relationship between the coefficient of friction, η and apparent contact geometry in sliders. This paper presents the results of various experimentally evaluated slider pad width to length ratios, B/L (L is signified with direction of motion), while maintaining the unit loading constant. The empirical data is intended to provide guidance in design and in theoretical prediction of optimum bearing geometry for solid/powder lubricated systems.

ISSN:1040-2004    

DOI:10.1080/10402009908982264

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

An analysis of the oil permeation from micro oil pits under the influence of bulk plastic flow has been developed. A series of rolling experiments was conducted and the experimental results were analyzed. It is found that the bulk strain rate can reduce the resistance of asperity to permeation and change the surface finish significantly. The influence of strain rate on the nondimensional specific permeation flux, which is defined as the permeation flux per unit relative sliding velocity and width of oil pit, is also studied. The average nondimensional specific permeation flux increases rapidly with increasing strain rate. For small reduction where the interfacial pressure is small, it is easy for the lubricant to seep into the contact area. The nondimensional specific permeation flux is therefore higher for smaller reduction and is saturated when the strain rate becomes sufficiently high.

ISSN:1040-2004    

DOI:10.1080/10402009908982265

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The heat conduction equations and sliding contact temperatures of an anisotropic half-space have been investigated. Equations for beth the two-dimensional (band heat source) and three-dimensional (rectangular patch heat source) cases are developed from the basic equations of anisotropic solid heat conduction and subsequently examined using thermophysical properties from typical polymer matrix composite materials of varying continuous fiber orientation and thermal conductivities. The results indicate a significant variation in the interfacial contact temperatures, depending on the orientation of the thermal conductivities. In general, the basic form of the temperature distribution in the plane of contact does not vary with thermal conductivity orientation, however, the magnitude of the relative temperature rise in the contact region does depend on this orientation. When the highest relative thermal conductivity direction is in the plane of contact and parallel to the sliding direction, the relative temperature rise is a minimum and the degree of penetration of heat into the subsurface region is relatively low. When thermal conductivity is highest normal to the plane of contact, or in the contact plane normal to the sliding direction, the relative temperature rise is considerably higher.Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982266

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The paper considers the effect of velocity slip in rough porous journal bearings operating in the hydrodynamic regime. On the basis of stochastic theory of hydrodynamic lubrication of rough surfaces developed by Christensen and incorporating Beavers and Joseph slip condition at the porous bearing interface, different forms of Reynolds—type equations, as applicable to porous bearings are derived for various types of surface roughness pattern. As an application of the theory, the case of an infinitely long porous journal bearing operating under steady conditions is analyzed. It is shown that roughness—slip interaction considerably affects the bearing performance.

ISSN:1040-2004    

DOI:10.1080/10402009908982267

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Air bearing sliders in the Tango class use load bearing pads with inlet-throttled leading edges to control the mass flux and lift. The influence of leakage or diffusion effects is always present in real sliders. In some designs such as railed taper flat designs leakage is dominant. The behavior of such sliders must be determined with numerical methods that obscure deeper understanding. Many aspects of the behavior of Tango class sliders can be understood with the vast simplification allowed by inlet throttling. In this paper such a simplified analysis is applied to describe a complete air bearing slider composed of two pads. The conditions for static level flight are determined, as well as the linear stability of heaving and pitching oscillations. Both stable and unstable modes are identified. Either damping or amplification can result from convective effects in the absence of mechanical damping. In real implementations of Tango class sliders instability has not been observed thanks to diffusion. The present analysis can serve as a guide to select initial choices for the operating parameters that correspond to maximum convective damping.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:10.1080/10402009908982268

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor