摘要:

AbstractAdditive‐additive interactions between zinc dialkylphosphorodithioates and ashless alkylaminophosphorodithioates have been studied with the object of reducing the zinc level in the lubricant formulations. Various combinations of these components were evaluated for their antiwear and antioxidant properties using four‐ball and differential scanning calorimetry techniq

ISSN:0954-0075    

DOI:10.1002/ls.3010140402

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThis paper describes a theoretical investigation of the rheological effects of couple stress fluids on the performance of narrow porous journal bearings. A most general modified Reynolds equation is derived for narrow porous journal bearings using the Stokes constitutive equations for couple stress fluids. The fluid in the film region and in the porous region has been modelled as a couple stress fluid. The analysis takes into account velocity slip at the porous interface using the Beavers‐Joseph criterion. A closed‐form expression for field pressure is obtained for narrow journal bearings. Eigen‐type expressions for field variations are obtained. The dimensionless load‐carrying capacity, attitude angle, and coefficient of friction are presented for different operating parameters. It is observed that narrow porous journal bearings with couple stress fluids as lubricant show a significant increase in load‐carrying capacity with reduced coefficient of friction as compared to the Newtonian case. The present study predicts the effects of the percolation of polar additives (microstructures) into the porous matrix on the bearing pe

ISSN:0954-0075    

DOI:10.1002/ls.3010140403

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractBorate esters possess friction‐reducing, antiwear, and anti‐oxidant characteristics when blended in lubricating oils. However, borate esters are susceptible to hydrolysis. The formation of a stable five‐member ring structure in the ester molecules, involving coordination of nitrogen with boron, contributes substantially to the resistance to hydrolysis of borate esters. The susceptibility of borates to hydrolysis can be reduced by introducing N,N‐dialkylaminoethyl groups with alkyl radicals containing more than three carbon atoms. X‐ray photo‐electron spectroscopy and X‐ray diffraction reveal that the borate ester can be adsorbed on the rubbing surface, and some of the adsorbed borate film degrades and forms boron nitride. Four‐ball wear tests indicate that the combination of oil‐soluble copper, tin, and cadmium compounds with organoborates gives better antiwear properties than the components separately. An antiwear synergistic mechanism is postulated in which borates with electron‐deficient boron p orbitals catalyse the tribo‐reduction of the metal compounds on the rubbing surfaces, produ

ISSN:0954-0075    

DOI:10.1002/ls.3010140404

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractRecent technological developments have revolutionised the lubricant industry by spurring a widespread quality improvement in both base oils and additives, giving superior finished lubricants. The upgrading of base oils is being brought about by more demanding requirements from original equipment manufacturers (OEMs), by government regulations, and through consumer awareness, environmental concerns, decreasing supply of high‐quality lubricant‐bearing crudes, and expanding markets worldwide.Present‐day lubricant demand is for maximum oxidation stability, superior low‐temperature performance, low volatility, and improved additive response, which are difficult to achieve through conventional processing. Conventional solvent lubricant refining produces base oils with a viscosity index (VI) of 100 with a fair amount of sulphur and aromatics, i.e., Group I base oils only. The current requirements of high‐performance base oils can conveniently be met through the hydroprocessing route. Depending upon the severity level, hydroprocessing is able to produce base oils of VI 95–110, in addition to low sulphur and high saturates content (Group II and Group III) by transforming the undesirable molecules into more useful structures. In countries such as India, a hybrid approach offers a technical solution to meet current demands for lubricant quality. This approach can be implemented in existing lubricant refineries without entailing major changes in refinery configuration, besides being cost‐effective.This paper describes the current requirements of modern lubricants in relation to API Groups and trends in these, and describes a sequence of technologies involving solvent refining, a cost‐effective hybrid scheme, and more recent hydroprocessing that allows a cost‐effective upgrading of Group I refining process. A case study is given that discusses the adoption of the hybrid scheme in

ISSN:0954-0075    

DOI:10.1002/ls.3010140405

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractNew engine design changes and ever‐increasing engine requirements make the design of gear oils challenging. A proper understanding of fundamental lubrication theory and formulation knowledge is necessary to develop new gear oils. This paper provides an overview of the fundamentals of lubrication theory and the functions of each additive. Key technical issues facing gear oils are also discusse

ISSN:0954-0075    

DOI:10.1002/ls.3010140406

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

摘要:

AbstractThe influence of heating on the properties of lubricating layers formed on steel by inactive and chemically active lubricant components has been studied by electrical probe methods. Model experiments combining X‐ray photoelectron spectroscopy analysis and measurements of friction and electrical characteristics in static and dynamic point contact have shown the approach to be promising in separate studies of the properties of the physically adsorbed layer (A‐layer) and chemisorbed layer (D‐layer) of deposits.It has been confirmed that D‐layers can be formed on metal surfaces at moderate temperatures (T ∼ 200°C) by both active additives and inactive components of mineral oil. Zinc dialkyldithiophosphate additives provide higher load‐bearing capacity of the A‐layer compared to pure mineral oil and can form D‐layers on steel at relatively low temperatures (of about 100°C). Lubricating layers with different physicomechanical and frictional properties can be formed depending on the chemical origin of the lubricating medium and the t

ISSN:0954-0075    

DOI:10.1002/ls.3010140407

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY

ISSN:0954-0075    

DOI:10.1002/ls.3010140401

出版商:John Wiley&Sons, Ltd    

年代:2002

数据来源: WILEY