摘要:

AbstractNuclear magnetic resonance (NMR) spectroscopy has emerged as a powerful technique for studying the molecular composition of base oil matrices. The usefulness of this technique lies in its ability to explain the chemistry involved in the molecular changes observed in various lubricant refining and extraction stages. This paper discusses the use of this technique in understanding the variation of gross properties observed in base oils during lubricant processing steps. The variations in weight percent of sulphur, viscosity index (VI), Conradson carbon residue (CCR), characterisation factor (KUOP), etc., are explained at the molecular level using high‐resolution quantitative1H and13C NMR. A single well‐recorded quantitative spectrum of a sample can be used to generate sufficient information on the different properties used for the specification of base o

ISSN:0954-0075    

DOI:10.1002/ls.3010150102

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThe high rotational speeds and loads of gears operating in acceleration gearboxes causes problems related to the correct choice and design of journal or rolling bearings. In the case of journal bearings, these problems are connected with thermoelastohydrodynamic lubrication theory and the dynamics of the bearing system. However, of major importance is the problem of thermal effects in journal bearings. This has been considered for bearings used in a double‐helical gearbox with the pinion and output shaft operating in cylindrical journal bearings. The oil film pressure, temperature, viscosity distributions, and maximum and mean oil film temperatures have been determined. In calculations, laminar adiabatic and turbulent adiabatic models of oil films have been applied. The results of the calculations can be used in the design of cylindrical or other types of journal bearing in rotating machinery, including acceleration or reduction gearboxe

ISSN:0954-0075    

DOI:10.1002/ls.3010150103

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractInvestigations of railway wagons fitted with rolling‐element bearings have shown damage to the bearings from the passage of electric current. This also occurs in railway wagons without an electric energy consumption of their own, because of residual currents from electric locomotives. This phenomenon gives rise to technical, financial, and even safety problems. This paper reviews research in the field of rolling‐element bearings exposed to electric currents. The paper also reports on an ongoing study undertaken to understand the mechanism of current flow and the role of lubricants in the associated damage, and to identify the possibilities of minimising bearing damage. The obvious solution to this problem is to use optimised greases, i.e., with high electrical conductivity and good lubricating ability.In the preliminary work reported here a number of greases for railway use were tested to determine their electrical conductivity in static and dynamic situations. These tests were performed using specially designed apparatus, and significant initial information about the electrical properties of greases has been obtained in this research, for example, that there is a correlation between the electrical conductance under static and dynamic conditions. All the greases tested showed comparatively high resistivity values, which could be one explanation for the bearing damage obser

ISSN:0954-0075    

DOI:10.1002/ls.3010150104

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractA numerical solution for the elastohydrodynamic lubrication of finite journal bearings is presented. Couple stress effects resulting from blending the lubricant with various additives are considered. Elrod's cavitation algorithm, which automatically predicts film rupture and reformation in the bearings, is implemented in the solution scheme. A simple elastic model is used to describe the elastic deformation of the bearing liner. Furthermore, the effects of surface waviness on the performance of the bearing are incorporated into the analysis. A comprehensive study illustrates the effects of couple stress, liner flexibility, and surface waviness on the steady‐state performance of finite‐width journal bearings. The results show that these effects should be considered at higher values of the eccentricity ra

ISSN:0954-0075    

DOI:10.1002/ls.3010150105

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractTribopolymerisation, a novel concept of molecular design developed by Furey and Kajdas, involves the continuous formation of thin polymeric films on rubbing surfaces; the protective films formed are self‐replenishing. The antiwear compounds developed are effective with metals and ceramics and in the liquid and vapour phases. Furthermore, they are ashless and contain no harmful phosphorus or sulphur, and many are biodegradable. The potential applications are diverse and have cost, performance, energy, and environmental advantages.The present paper describes some applications of the concept of tribopolymerisation as a mechanism of boundary lubrication, including recent laboratory research and in‐plant industrial demonstrations. Applications include: (a) ashless antiwear or ‘lubricity’ additives for fuels; (b) ashless lubricants for automotive engines to reduce exhaust catalyst poisoning and environmental emissions; (c) lubrication of ceramic engines or ceramic components; (d) machining and cutting using thin films to reduce friction and ceramic tool wear; (e) vapour‐phase applications in high‐temperature gaseous systems or to counter fuel injector wear problems in natural gas engines; (f) special ‘minimalist’ pre‐treatment compositions for engine assembly and running‐in; and (g) enabling technology in the development of new engines and

ISSN:0954-0075    

DOI:10.1002/ls.3010150106

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThe relationship between the temperature and the lubricating properties of an organocopper compound used as a lubricant additive has been studied on steel‐steel rubbing pairs. The results showed that the organocopper compound significantly reduced both the wear and the friction of steel balls for different test temperatures, but that there is a distinction between the friction critical temperature and the wear critical temperature. Results showed that the organocopper additive could improve both the friction critical and the wear critical temperature of a mineral oil. For example, the friction critical temperature increased from 50 to 220°C and the wear critical temperature from 110 to 290°C. Micrographs of the wear scars at different temperatures were used to investigate the lubricating film's temperature characterist

ISSN:0954-0075    

DOI:10.1002/ls.3010150107

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

ISSN:0954-0075    

DOI:10.1002/ls.3010150101

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY