摘要:

AbstractThe piston ring is one of the main elements in an internal combustion engine. Together with the cylinder sleeve, the piston ring has two basic functions: (1) contacting the cylinder sleeve to prevent the gases formed above the piston from migrating to the crankcase and (2) as a translation couple, formed of the piston‐ring and cylinder‐sleeve assembly.Complex tribological phenomena occur in the piston‐ring and cylinder‐sleeve tribosystem, according to variations in sliding speed, gas pressure, and temperature.This paper presents a method of calculation of the thickness of the lubricant film in the piston‐ring and cylinder‐sleeve tribosystem, using the Reynolds equation, integrated in specific conditions. According to the Newtonian behaviour of the lubricant, the shear stresses in the lubricant film between the piston ring and cylinder sleeve are determined. A computational procedure to determine flash temperatures in the piston‐ring and cylinder‐sleeve tribosystem is presented. The theoretical results, including film thickness, sliding speed, gas pressure, and flash temperatures for a complete crankshaft cycle are

ISSN:0954-0075    

DOI:10.1002/ls.3010120202

出版商:John Wiley&Sons, Ltd    

年代:2000

数据来源: WILEY

摘要:

AbstractCapillary viscometry has been employed to measure the viscosities of dilute polymer solutions over the temperature range ‐10 to 150 °C. A Group II base oil containing 95% saturates was used as solvent for an olefin copolymer (OCP), a hydrogenated diene copolymer (HDP), and a polymethacrylate (PMA). These three polymers represent the three major families of viscosity index (VI) improvers used nowadays in lubricant formulations. Intrinsic viscosities and Huggins' constants were also determined. The thickening effects of the olefin copolymer and the hydrogenated diene copolymer were found to be higher at low temperatures (e.g., 40 °C) than at higher ones (e.g., 100 °C), which phenomenon was attributed to stronger intermolecular hydrodynamic interactions at low temperatures, as indicated by the Huggins constants. For the hydrogenated diene copolymer and the polymethacrylate polymer, the viscosity increased abruptly when the temperature went below 10 °C. This unusual observation was attributed to the crystallisation of a small fraction of the base oil. Based on the intrinsic viscosity data, it was concluded that at temperatures between 10 and 150 °C, the polymer coil dimension remains a constant for the olefin copolymer and the hydrogenated diene copolymer VI improvers, but increases with increasing temperature for the polymethacrylate VI im

ISSN:0954-0075    

DOI:10.1002/ls.3010120203

出版商:John Wiley&Sons, Ltd    

年代:2000

数据来源: WILEY

摘要:

AbstractThis paper considers the use of contact electrical conductivity to analyse boundary lubrication at various temperatures. The main mechanisms of contact conductivity within the temperature range typical of lubricated tribosystems are discussed. Special equipment is described for temperature investigation and experimental data are presented on electrophysical methods. Model experiments with static nominal point contacts bring to light some peculiarities of the behaviour of boundary films when heated. Analysis of electrical and frictional characteristics under sliding shows the contact resistance method to be promising in the thermal testing of boundary films.

ISSN:0954-0075    

DOI:10.1002/ls.3010120204

出版商:John Wiley&Sons, Ltd    

年代:2000

数据来源: WILEY

摘要:

AbstractThe ability of directed streams of three representative hydrocarbon gases ‐ acetylene C2H4, ethylene C2H4, and ethane C2H6‐ to provide extended‐duration lubrication to high‐temperature sliding contacts via surface deposition of pyrolytic carbon has been demonstrated. One order‐ and two order‐of‐magnitude reductions in friction coefficient and wear rate of self‐mated silicon nitride sliding contacts can be realised by this technique. The ability of these gases to provide ‘adequate’ lubrication at high temperature is illustrated through mapping the normal load/temperature/precursor flow rate space over which reduced friction may be maintained. Acetylene was the most effective precursor for pyrolytic carbon deposition, providing adequate lubrication over the broadest range of normal load/temperature/flow rate combinations, while ethane was the least effective. The boundary of the regions of adequate lubrication represents the locus of contact conditions with equal rates of lubricious carbon deposition and removal by wear. The shape of this boundary, as explored in the mapping study, supports a proposed model in which the removal rate is proportional to the product of normal load and sliding speed, while the deposition rate is proportional to the product of precursor flow rate and an Arrhenius tem

ISSN:0954-0075    

DOI:10.1002/ls.3010120205

出版商:John Wiley&Sons, Ltd    

年代:2000

数据来源: WILEY

摘要:

AbstractAn important and growing field of lubrication lies in the use of solid films, although they are in general more expensive than oils or greases, and require specialist attention both in mechanical design and in coating application techniques. In this paper, the general classification of solid lubricant types is reviewed, along with the reasons for choosing, and methods of depositing, solid lubricants, in particular MoS2. The best‐performing and most flexible technique for making MoS2films is by physical vapour deposition (PVD), and the variants of that technology are considered. The intrinsically lubricating, lamellar structure of pure MoS2is described, along with a brief summary of its wear and failure modes. Present applications for lubrication by MoS2in spacecraft and dry machining are outlined, as are anti‐adhesive uses in extruding and moulding. The current state of the art of modification of MoS2films consists in the addition of dopants (co‐sputtering), in multilayering as a series of films, each fulfilling a specific task, or in stacking repeating nano‐metre‐scale films. Composite films of MoS2islands in a hard film matrix are also being

ISSN:0954-0075    

DOI:10.1002/ls.3010120206

出版商:John Wiley&Sons, Ltd    

年代:2000

数据来源: WILEY

摘要:

AbstractFor some years, reports have been published on adding solid lubricant powder to oil to improve the tribological properties of the latter, but the results have not been satisfactory. In this paper, we describe the preparation of CaCO3nanoparticles in a microemulsion consisting of sodium dodecyl‐sulphate (SDS)/isopentanol/cyclohexane/water, and assessment of the tribological behaviour of CaCO3nanoparticles as additives for lubricating oils. The CaCO3nanoparticles were characterised by transmission electron microscopy (TEM), and their tribological performance was tested in a four‐ball machine; the rubbing surface was analysed with X‐ray photoelectron microscopy (XPS). The results indicate that the size of CaCO3nanoparticles increased with the concentration of aqueous reactant, and that CaCO3nanoparticles exhibited good load‐carrying capacity, antiwear and friction‐reducing properties. The tribological properties of lubricating oils could be improved significantly by dispersing CaCO3nanoparticles in 500SN base oil containing dispersants such as polyisobutene‐butanediimide (T154), calcium alkylsulphonate (T101) and methyl‐tricaprylamine chloride (aliquat 336). The improvements in friction and wear were concluded to be due to the formation of a film containing CaCO3and CaO in the rubbing region, and the presence of nanoparticles, which may act in the same way as ball bearings, to facil

ISSN:0954-0075    

DOI:10.1002/ls.3010120207

出版商:John Wiley&Sons, Ltd    

年代:2000

数据来源: WILEY

ISSN:0954-0075    

DOI:10.1002/ls.3010120201

出版商:John Wiley&Sons, Ltd    

年代:2000

数据来源: WILEY