摘要:

AbstractAn analysis of circular contacts under elastohydrodynamic lubrication using a hybrid technique is presented. In particular, attention has been focused on the pressure distribution calculation. A versatile code has been developed to evaluate the pressure distribution starting from three‐dimensional film thickness maps obtained from the analysis of interferometric images. The code has been developed in C++ and is based on the multigrid technique. This hybrid technique has a basic advantage over the full numerical approach in that the pressure is obtained without making any assumptions about the lubricant itself. The main drawback of the method is that high‐resolution interferometric images are requi

ISSN:0954-0075    

DOI:10.1002/ls.3010170302

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractA series of hexadecyl polynuclear aromatic, decalin, and tetralin sulphonates have been synthesised. The critical micelle concentration (CMC) and surface and interfacial tension values at various concentrations above and below the CMC in both aqueous and non‐aqueous media have been determined. The micellar size and shape, the average number of monomers constituting these micelles, and the thermodynamic properties have also been estimated. These studies show that the CMC value in both aqueous and heptane media decreases with an increase in the number of aromatic rings in the sulphonates. The size and shape of the micelles do not change appreciably in heptane, although the number of monomers constituting the micelles changes with a change of structure of the aromatic moiety. The thermodynamic parameters do not seem to affect the surface activity and solubilising properties even though the free energy, enthalpy, and entropy decrease with an increase in the size of the aromatic moiety. The surface and interfacial tension values are the lowest with aqueous and non‐aqueous solutions of hexadecyl naphthalene sulphonate, but these values increase with an increase in the number of aromatic rings in the sulphonates. The sizes of the micelles of hexadecyl naphthalene sulphonate in aqueous solutions and the number of monomer molecules constituting the micelles are greater than for the other aromatic sulphonates. Although the sizes of micelles of hexadecyl benzanthracene sulphonate and hexadecyl pentacene sulphonate are comparable, the numbers of molecules constituting these micelles are the smallest. The solubilisation of alkanes in aqueous solutions of sodium naphthalene sulphonate containing electrolyte and isobutanol is the highest, but it falls off rapidly for all the other sulphonates. This shows the extreme sensitivity of solubilisation to the structure of the sulphonates. The detergency increases with an increase in the size of the aromatic moiety. The structure thus has a profound influence on the surface and micellar properties of these sulphonates. These studies are important from the point of view of the use of synthetic sulphonates as additives / surfactants in place of petroleum sulphona

ISSN:0954-0075    

DOI:10.1002/ls.3010170303

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractThe effect of surface roughness on traction performance was experimentally studied using a two‐roller tester. The nature of the contact was investigated using electrical resistance and electrical capacitance methods. Increased shear stress was observed in the viscous region, which could be attributed to a higher average shear rate and to greater viscosity under EHD contact conditions due to pressure fluctuations caused by the surface textur

ISSN:0954-0075    

DOI:10.1002/ls.3010170304

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractNanometric molybdenum disulphide particles of about 30 nm diameter have been prepared by the hydrodesulphurisation of molybdenum trisulphide obtained from acidifying a mixed solution of Na2MoO4and Na2S at ambient temperature using a quick homogeneous precipitation method (QHPM). Using X‐ray diffraction and transmission electron microscopy (TEM), the size and crystallisation of the nano‐MoS2obtained by hydrodesulphurisation at different temperatures have been investigated. In addition, the tribological performance of nano‐MoS2has been investigated by means of a block‐on‐ring tribometer, X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results show that base oils with nanometric MoS2as an additive provide higher wear resistance than other oils containing commercially available common MoS2. However, the friction reduction is not obviously improved. SEM characterisation reveals a worn, smooth surface when using the nano‐MoS2additive, and XPS analysis indicates a greater amount of molybdenum oxide and iron sulphide in the antiwear thin film formed on the r

ISSN:0954-0075    

DOI:10.1002/ls.3010170305

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractThis paper describes a simple analytical model for top piston ring lubrication. The model is constructed using the open‐end boundary condition hypothesis, with an assumption of minimum hydrodynamic pressure in the effective ring length equal to the saturation pressure. The analysis confirms that not all of the ring length is involved in the case of hydrodynamic lubrication, and the effective length is found to be less than 40–50% under some operating conditions. The results are in agreement with previous investigati

ISSN:0954-0075    

DOI:10.1002/ls.3010170306

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractEngine oil lubricants are formulated with a variety of additive components at different dosages to obtain the desired physico‐chemical characteristics. Antiwear, friction modification/energy efficiency, dispersancy, and detergency properties are normally achieved by the use of zinc dialkyldithiophosphate (ZDDP), molybdenum dithiocarbamate (MoDTC) and ashless alkyl phosphorodithioate, polyisobutylene succinimide (PIBS), and metal sulphonates / phenates, respectively. It has been reported that these additives interact with each other and affect the overall performance of a lubricant system. The additive‐additive interactions have been studied by nuclear magnetic resonance (NMR) and infrared spectroscopic techniques, where attention has been mainly focused on the ZDDP‐PIBS additive system in the presence or absence of other additives. The results have been used to relate the synergistic or antagonistic effects of such interactions to the overall performance of a lubricant.Recently, MoDTC has found wider application in lubricants as a friction modifier and energy‐efficient additive. However, no studies of the additive‐additive interactions of the PIBS‐MoDTC‐ZDDP additive system using analytical techniques have been reported. The present paper covers the fundamental and mechanistic aspects of additive‐additive interactions of ZDDP, MoDTC, PIBS, and sulphonate / phenate additives present in a lubricant system as studied by31P NMR, electron spectroscopy for chemical analysis (ESCA), and thermogravimetric analysis (TGA) techniques. ESCA, which is a surface analytical technique, has been used to provide basic evidence for the formation of various complexes through interactions occurring in the electronic binding energies of orbitals of various atoms of the additives. The ESCA studies have also revealed the actual atomic sites of interaction between the additives responsible for the formation of adducts or complexes. The differential scanning calorimetry profiles of blends have verified the interactions among the additives and shown that the stability of the additive system is quite different from that of the additives alone. The shifts in the31P NMR signals, the changes in the binding energies of the s, p, and d orbitals of additive elements, and the multistage decomposition profiles in the TGA thermograms of interacting systems due to complexion and adduct formation have enabled a mechanism of interaction

ISSN:0954-0075    

DOI:10.1002/ls.3010170307

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

摘要:

AbstractThis paper reports a theoretical investigation of transient elastohydrodynamic lubrication of a line contact. A time‐dependent Reynolds equation and elasticity equations for compressible solid‐liquid lubricants were solved using finite volume and multigrid techniques. The lubricants used were mineral oils mixed with very small solid particles, MoS2and PTFE, which can be treated as Newtonian fluids. The two surfaces were initially at rest and in contact. The transient oil film pressure and oil film thickness were calculated numerically. This simulation showed the significant effects of solid particles on the lubrication characterist

ISSN:0954-0075    

DOI:10.1002/ls.3010170308

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY

ISSN:0954-0075    

DOI:10.1002/ls.3010170301

出版商:John Wiley&Sons, Ltd    

年代:2005

数据来源: WILEY