摘要:

AbstractThe response of base oil hydrocarbons to additive molecules is fundamental to any lubricant formulation. To have this understanding it is important to have complete knowledge of the base oil hydrocarbon composition. The work reported here is a study of a series of API Group I base oils showing the effect of various structural parameters during oxidation with an antioxidant additive (zinc dialkyldithiophosphate, ZDDP). To understand this complex base oil‐additive interaction pattern, a combination of chromatographic and spectroscopic methods has been adopted. The results show that certainNMR‐derived base oil structural parameters can be used as an index of the additive response in conjunction with column chromatographic andFTIRabsorption data. It is also observed that saturated molecules, i.e., iso‐ and normal paraffins and naphthenes, behave differently towards an antioxidant additive, and the total additive response is the result of all the interactions in the s

ISSN:0954-0075    

DOI:10.1002/ls.3010140202

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThe effectiveness of ‘far‐field’ vapour‐phase lubrication, in which areas of a bearing surface that are cycled through the contact are exposed to vapour while outside the contact, has been demonstrated in both sliding and combined roll slide tests using acetylene vapours to deposit pyrolytic graphite. Friction coefficients as low as μ = 0.008 have been measured for steel at 540°C with far‐field acetylene concentrations as low as 5%. Effective vapour‐phase lubrication depends on solid lubricant deposition that exceeds the contact's capacity to remove solid lubricant through wear. While the rate of removal is increased by increasing the sliding velocity, in far‐field vapour‐phase lubrication the rate of lubricant deposition, and therefore the lubrication effectiveness, is augmented by increased areas available for far‐field deposition, such as those provided by performing wear tests with increased wear‐track diameters. These geometric concepts may be considered in rolling‐element bearing and gear set applications where vapour‐phase lubr

ISSN:0954-0075    

DOI:10.1002/ls.3010140203

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThis paper reviews the current understanding of lubricated contacts and the origins of friction in terms of the Stribeck curve. It discusses the various ways that lubricant additives can modify friction in thin‐film lubricated contacts, examining both the nature and properties of the films formed by these additives, as revealed by film thickness measurements, and their consequent effect on the Stribeck friction curv

ISSN:0954-0075    

DOI:10.1002/ls.3010140204

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThe thickness and frictional characteristics of thin lubricant films are known to affect the fuel economy properties of oils. The base oil and polymer compositions of the lubricant are generally considered to be critical chemical factors that can influence these thin‐film lubricant properties in new oils. However, it is important to produce lubricants with good fuel economy properties that are maintained after the lubricant is degraded. Lubricants in use can undergo oxidation and mechanical shear degradation. The effect of oxidation degradation on thin‐film physical properties has previously been studied. This paper investigates the effect of mechanical shearing on thin‐film properties. Dispersant olefin copolymers are found to reduce thin‐film friction in simple mixtures and in fully formulated oils. In simple mixtures, shearing the dispersant olefin copolymers does not affect the friction‐reducing ability of these polymers. In fully formulated oils, even though shearing diminishes to a degree the friction‐reducing ability of dispersant olefin copolymers, these copolymers can still provide significant frictio

ISSN:0954-0075    

DOI:10.1002/ls.3010140205

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThere are many methods of calculating the properties of lubricated hydrodynamic sliding bearings running at variable loads, but, in some cases, sliding bearings of heavy‐duty machines run under constant load and at variable speeds; this can lead to reduced film thickness in the bearing and boundary lubrication. The minimum oilfilm thickness in such a bearing needs to be calculated so that the proper lubricant viscosity can be selected to reduce solid‐solid contact during machine operation. In this study, a method is presented for calculating the film thickness of sliding bearings operating with alternating rotational directions. The results of the calculations show that the squeeze effect can develop enough load‐carrying capacity to prevent solid‐solid contact between the rubbing surfaces during operation, provided the change of direction of rotation is quick

ISSN:0954-0075    

DOI:10.1002/ls.3010140206

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThis paper describes a study of the effect of aromatics in lubricant base oils on the efficiency of adsorptive additives in terms of lubrication and rust‐inhibition performance. The additives investigated were sulphurised isobutylene, tricresyl phosphate (TCP), sorbitol monooleate (Span‐80), and alkylene succinic acid. Four‐ball friction and wear tests, a modified ASTM D 665 rust test, an electrochemical test, and X‐ray photoelectron spectroscopy (XPS) were used to reveal the relationship between the aromatics and the additives. The results show that the aromatic hydrocarbons in the base oils reduce the surface activity of the additives; competitive adsorption between the polar compounds and the additives is not a key factor governing the behaviour of the additives under the test con

ISSN:0954-0075    

DOI:10.1002/ls.3010140207

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractBoron compounds are emerging as promising materials for a wide range of applications in automotive and industrial lubrication systems. Several studies conducted on boron compounds have revealed that they exhibit desirable properties for preparing stable and compatible lubricant components for a new generation of lubricating oil formulations. Boron‐containing lubricants have major tribological advantages, such as antiwear efficiency, good film strength, high‐temperature resistance, and self‐lubricating properties. The increasing number of patents concerning boron‐containing lubricants illustrates commercial interest in this area. Boron lubricants can be used in many forms, such as oxides, esters, and boric acid. Therefore, it can be expected that a new generation of lubricant formulations includes boron compounds. This paper presents an overview of various solid and liquid lubricants containing boron as an important ingredient, and is intended to aid the development of new lub

ISSN:0954-0075    

DOI:10.1002/ls.3010140208

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThis paper reviews selected phenomena related to the boundary friction process. The central thrust is on triboemission, defined as emission of electrons, charged particles, photons, etc., under conditions of boundary friction and/or surface damage caused by fracture processes. Low‐energy electrons are one of the most important particle components in triboemission. Accordingly, the triboemission process is of particular significance for (i) the boundary friction process as such, and (ii) the tribochemistry of the boundary lubrication process. This review considers all the major issues of triboemission and related phenomena/processes. It is shown that, in the boundary lubrication regime with hydrocarbon lubricants, charge intensities decrease with an increase in lubricant molecular weight. The paper also includes some recent information concerning research on triboemission along with a newly developed apparatu

ISSN:0954-0075    

DOI:10.1002/ls.3010140209

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThe phenomenon of grease slip in the boundary layer of a lubricating pipe or a journal bearing is discussed here. A correlation between this phenomenon and the grease structure has been found. Based upon earlier work, it has been shown that a generalised Casson rheological model as well as a proposed yield stress distribution in the lubricant wall layer are useful for an analytical description of the phenomenon. A Couette rheometer was used for testing. As a result of the investigations it is shown that the wall material significantly affects the yield stress distribution in the boundary layer. Essential differences in the stress values are found, especially for plastics and metals.

ISSN:0954-0075    

DOI:10.1002/ls.3010140210

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractA source of waste‐water pollution in machining is the lubricating/cooling fluid used. This study investigates the application of the flotation technique for the removal of emulsifiable oil. Research has been carried out on a process of selective separation of oil using mixtures of anionic/nonionic surfactants as collectors and a cationic surfactant as a de‐emulsifier (coagulant). The behaviour of the mixtures at the aqueous solution‐air interface has been studied, and the critical micelle concentration, efficiency, effectiveness, minimum surface area, and free energy of micellisation determined. The effect of the optimum mole fraction of the mixtures on oil separation has been discussed from the point of view of physical parameters. The selectivity achieved can be explained in terms of surfactant concentration and the structure of the mic

ISSN:0954-0075    

DOI:10.1002/ls.3010140211

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY