bluuebunny/crossref_metadata_2025_split huggingface dataset:
Grease lubrication in isothermo‐elastohydrodynamic line contact
Authors: Dong Daming , Kimura Yoshitsugu , Okada Kazumi , Liu Wenyi 
Published: July 2006

AbstractElastohydrodynamic analysis is conducted and a numerical solution is presented for the film thickness in grease lubrication in isothermal, fully‐flooded rolling line contact with or without slip. By making use of a perturbational method, a modified Reynolds equation is established, which can be used with various constitutive equations if the equivalent viscosity can be expressed as a function of the shear rate. Verification of this analysis is carried out by experimentally determining the minimum film thickness with an X‐ray transmission technique, with satisfactory agreement. The effect of temperature on the apparent viscosity of grease is also discussed.
On thin film lubrication
Authors: Wen  , Shizhu  
Published: July 2006

AbstractVarious phenomena are revealed under EHL and micro‐EHL conditions, such as the properties of the lubricant under high pressure, traction, and the load‐bearing capacity of the lubricant film, and are discussed in the present paper. A new lubrication regime, thin film lubrication, has been discussed. The theoretical and practical significance of research on thin film lubrication is elaborated. Finally, the characteristics describing thin film lubrication and its main research directions are suggested.
A system for wear prediction in lubricated sliding contacts
Authors: Stolarski T. A. 
Published: July 2006

AbstractA system of analysis is developed to predict the rate of wear in sliding contacts. The essence of the approach is the proposal that the rate of wear can be predicted only in probabilistic terms. Therefore, the estimation of the probability of wear, which can be regarded as synonymous with the probability of surface asperity contacts, precedes the calculation of the wear rate. Further, recognising the fact that wear takes place within the actual area of contact, it is argued that this area consists of plastic and elastic contacts between asperities which, in turn, have different shear strengths and contribute differently to the wear process. In the case of lubricated contact, a frictional film defect represents the influence of a lubricant on the wear process. Moreover, as in this type of contact the load is supported by both lubricating film and contacting asperities, a special procedure is provided to estimate the load supported by the asperities, because it is only that part of the load which contributes to the wear. The catastrophic form of wear in lubricated contacts, that is termed ‘scuffing’, is also considered, and the probability of scuffing, under a given set of operating conditions, is estimated. The predictive system has been tested and its predictions are compared with available experimental results.
Free chlorine fixation and the protective film in boundary lubrication
Authors: De‐hua Tao , Huai‐Liang Zhu , Zhi‐meng Hu 
Published: July 2006

AbstractWax chloride is an older type of additive which releases free chlorine when it is hydrolysed or when it is in conditions of boundary lubrication. The chlorine forms a protective film of ferro‐chloride but, on the other hand, it severely rusts the iron, the main reason for its discontinuance since the 1960s.In this paper, epoxy plant oil is recommended as a means to absorb effectively and fix the free chlorine, then transform it into chlorohydroxyl oil and polyether. Rust corrosion can be controlled, and the absorbent transformed into a ferro‐chloride protective film on the frictional surfaces of the iron during rubbing. The free chlorine can thus be transformed directly into a protective film.With a dynamic test for the reaction of absorption HCl, a friction test, an anti‐rust test, electron spectroscopy and infrared spectroscopy analysis, the underlying principles and effects of chlorine fixation have been confirmed. This method has been applied to cold squeezing, and tested with EP industrial gear oil. The price of wax chloride is much less than the standard additive containing sulphur and phosphorus, and its properties are almost the same. It is concluded that wax chloride could still be viable for use in lubricants.
Oxidation of mineral base oils of petroleum origin: The relationship between chemical composition, thickening, and composition of degradation products
Authors: Maleville X. , Faure D. , Legros A. , Hipeaux J. C. 
Published: July 2006

AbstractThe aim of this study was to improve understanding of high‐temperature oxidation of base oils used in automobile engine oil formulations. Various oils were investigated: oils from the Middle East and the North Sea, with high and low aromatic and sulphur contents respectively; a hydro‐isomerised polyalphaolefin oil with no aromatic or sulphur content; and a hydrocracked oil of intermediate composition.The influence of the aromatic and sulphur content and composition of the oils on thermo‐oxidative degradation is investigated. These compounds give base oils natural protection from oxidation, but, under severe oxidation conditions, in the presence of a catalyst such as iron, which is always present in an engine, they become precursors of deposits.The action of two types of additive, radical inhibitors and hydroperoxide decomposers, was studied through oxygen consumption and thin‐film oxidation tests.The oxidation products were identified; these provide insight into the degradation processes of the compounds during oxidation. They show too the influence of these processes on the formation of oxidised volatile species, on the increase in viscosity of the oil, and on the formation of oxidised species of high molar mass which, as they condense, contribute to the formation of insoluble compounds and deposits.
The synergistic effects of tricresyl phosphate oil additive with chemico‐thermal treatment of steel surfaces
Authors: Yansheng Ma , Jiajun Liu , Linqing Zheng 
Published: July 2006

AbstractThe addition of various extreme pressure and anti‐wear additives to lubricating oil is an important and effective way of reducing friction and wear. The application of chemico‐thermal treatments to material surfaces is another way to improve the tribological behaviour of rubbing pairs.The synergistic effects on the tribological behaviour of a tricresyl phosphate oil additive together with sulphurised, nitrided and oxy‐nitrided surfaces of 1045 steel were systematically studied on a ball‐on‐disc test machine. Good load bearing capacity and reduced friction and wear was obtained as a result. As well as presenting the promising results of this work here, the mechanism of this synergistic effect is discussed, based on micro‐analysis of the surface films by AES and XPS.
The kinetics of lubricant penetration action during machining
Authors: Godlevski V. A. , Volkov A. V. , Latyshev V. N. , Maurin L. N. 
Published: July 2006

AbstractA new model of cutting fluid penetration in the interface zone during metal cutting is proposed. This model includes three stages relating to processes in a single capillary: 1. liquid phase entry, 2. ‘micro‐droplet explosion’, and 3. filling the capillary by gas phase lubrication. Calculations of model parameters have been done for two different liquids: water and castor oil. The correlation between model data and known experimental results is also given.
The deterioration of lithium greases under the influence of electric current—an investigation
Authors: Prashad Har , Murthy T. S. R. 
Published: July 2006

AbstractIn the present work, we report on the analysis of the deterioration of lithium greases used in rolling‐element bearings by X‐ray diffractometry (XRD), X‐ray fluorescence spectrometry (XRFS), and atomic absorption spectrometry (AAS). These techniques give reproducible, reliable data with which to establish the severity of deterioration of greases recovered from the active zone of bearings. XRD appears more suitable for diagnosing quickly the chemical changes that have occurred in the soap residue of greases, even in small quantity, than other analytical and performance evaluation techniques.Fresh lithium greases, their chemical composition, and the formation of new compounds in the greases have been investigated after use in rolling‐element bearings run in the presence of electric fields, and also under pure rolling friction conditions without electric fields on a roller‐bearing test rig. The deteriorated greases recovered from various motor bearings have also been analysed and the results are compared with those for the greases from the test bearings.X‐ray diffraction analysis shows that the chemical composition of the soap residue of the fresh lithium grease, lithium stearate (C18H35LiO2), does not change in bearings operated without the effect of electric fields, under pure rolling friction. However, lithium iron oxide (Li5FeO2) peaks were detected after prolonged operation of the bearings. On the other hand, under the influence of electric fields, the chemical composition of the grease changed to lithium palmitate (C16H31LiO2), and peaks of gamma lithium iron oxide (Γ‐LiFeO2) and lithium zinc silicate (Li3.6Zn0.2SiO2) were detected. The surface of the bearings was found to be corroded after operation under electric fields. AAS showed a considerable increase in the lithium percentage, and lithium carbonate and lithium hydroxide in the used greases in aqueous solution, compared to the fresh greaseThe investigations reported in this paper, together with study of damaged/corrugated bearing surfaces, offer potential in diagnosing the cause of bearing failure in teh presence of electric fields, and in establishing the severity of deterioration of the lithium greases used in the bearings.
Tribological performance of molybdenum and zinc dithiocarbamates and dithiophosphates
Authors: Vipper A. B. , Parenago O. P. , Karaulov A. K. , Kuz'mina G. N. , Mishuk O. A. , Zaimovskaya T. A. 
Published: July 2006

AbstractThere is a basic interest in the activity of antifriction additives, which are important to fuel economy and the wear of engine components. This paper investigates the influence of some antifriction compounds, including molybdenum dithiophosphine and dithiocarbamine, on the layers formed on rubbing parts. It was found that there were differences in the antifriction performance of the oils containing the candidate additives, and the paper offers an explanation of the mechanism of action at work.
The tribological behaviour of mineral oils additivated with polyethylene
Authors: Bercea Maria , Bercea Ioan , Nelias Daniel , Olaru Dumitru 
Published: July 2006

AbstractThe paper investigates the elastohydrodynamic lubrication of concentrated contacts in a rolling bearing operating at moderate speeds. Two base oils with different characteristics, additivated with low‐density polyethylene were used as lubricants.Rheological and tribological tests were performed to study the influence of temperature, polymer concentration, and bearing speed. The influence of the addition of a polymer component on the film‐forming properties and on wear under high pressure was examined in a four‐ball test rig. Experimental data show that the polymer concentration added to the base oil plays an important role in obtaining greater film thicknesses and in preventing wear in elastohydrodynamic contacts.
The effect of ZDDP in CVT fluid on increasing the traction capacity of belt‐drive continuously variable transmissions
Authors: Kano Makoto , Mabuchi Yutaka , Ishikawa Takao , Sano Akio , Wakizono Tetsuo 
Published: July 2006

AbstractBelt‐drive continuously variable transmissions are already being increasingly used in Europe and Japan for small vehicles, but midsize vehicles will require greater torque capacity. This paper discusses the effect of ZDDP as an additive on increasing the traction obtained at the sliding interfaces between the elements and pulleys of a belt‐drive continuously variable transmission (B‐CVT). This effect stems from the higher friction coefficient at the sliding interfaces.Friction coefficients were measured in rig tests in which test pieces cut from actual CVT elements were slid against a disc in different types of CVT fluid (CVTF). After the tests, the adsorbed films on the specimen surfaces were investigated with electron probe microanalysis (EPMA), and compared with pieces cut from elements subjected to a high torque test conducted with the B‐CVT. The experimental results indicated that the higher friction coefficient at the sliding interfaces was due to the shearing of the tough adsorbed film. The film was blue in colour, and consisted mainly of zinc precipitated from the ZDDP additive.
Rebounding lubricant layers
Authors: Yin J. , Eissa K. I. , Gohar R. , Cann P. M. E. 
Published: July 2006

AbstractMost research in elastohydrodynamic lubrication has concentrated on the immediate contact area between the two elements. In the case of ball or cylindrical roller bearings, the finitely separated rolling elements may have, between them, a free‐surface lubricant film on each of their races. This film, formed by the wake emanating from one pair of elements, becomes the inlet boundary condition for the following pair. Its possible variation in shape with time is thus important when estimating the lubricant film thickness.With this practical situation in mind, the variation with time of the wake formed behind a ball sliding in a thin viscous lubricant layer on a plate has been studied. Using thin‐film theory and an initial wake cross‐section similar to those observed experimentally, the Navier Stokes equations are solved to yield solutions which describe the subsequent alteration in the wake shape with time. It was found that the track centre of the wake remains at, or slightly below, its chosen initial height for some time before commencing rebound towards the undisturbed layer condition.This behaviour is confirmed by some simple experiments carried out on a ball‐and‐plate machine which also indicate that the track centre height, measured just downstream of the ball, is initially less than the minimum film thickness under the ball and remains at or near this condition for some time before rebound commences.The experiments have also shown that time taken for the track centre height to regain the minimum height under the ball is found to depend on the lubricant properties, the undisturbed layer thickness and the depth of immersion of the ball.
Thermal effects and contact conductivity under boundaryZ lZuZbrication
Authors: Konchits V. V. , Korotkevich S. V. , Kim C. K. 
Published: July 2006

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.
Comparison of various C2Hx for high‐temperature lubrication by in situ pyrolysis
Authors: Holmes D. M. , Sawyer W. G. , Blanchet T. A. 
Published: July 2006

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 temperature dependence.
Preparation of magnesium borate succinimide and its characteristics as a lubricating oil additive
Authors: Shi Yonggang , Dong Junxiu 
Published: July 2006

AbstractSuccinimide has for a long time been widely used for ashless dispersants in engine lubricating oils. However, this kind of dis‐persant does not have particularly good antioxidant, antifriction, antiwear or acid neutralisation properties. In this paper, a method is suggested for modifying succinimide so as to obtain improved antioxidant, acid neutralisation, antifriction, and antiwear properties.Magnesium borate cannot be dissolved in mineral lubricating oil. In the presence of succinimide, however, it will exist in a lubricating oil in the form of a colloid or complex. Therefore, in the present work, magnesium oxide, boric acid, and water were mixed together with succinimide. In the reaction process, some of the magnesium borate formed in situ will be surrounded by succinimide, forming stable colloids; the remainder will react with the succinimide, forming well distributed complexes in the lubricating oil. The presence of water is very important for this process. At least four moles of water are needed for one mole of magnesium borate.The resulting material has been evaluated as a lubricating oil additive. The experiments have shown that this kind of material possesses good antioxidant, acid neutralisation, antifriction, and antiwear properties, apparently due to the introduction of magnesium borate. The introduction of the magnesium borate does not influence the good dispersant properties of the succinimide.
The economic utilisation of sulphonation process residues in the petroleum industry
Authors: Mohamed M. M. , Naga H. H. Abou El , Anis A. 
Published: July 2006

AbstractSulphonation process residues in the petroleum industry are not exploited in line with their scientific or economic potential. The traditional routes for disposal of these residues can contribute to pollution, whereas various chemical techniques can be used to produce valuable products with domestic and industrial applications. The present work deals with the utilisation of sulphonation process residues.It is found that economic utilisation of sulphonation process residues from the petroleum industry involves the following:
A comparative evaluation of the performance of the products obtained with other available products demonstrated their efficiency and value.
Production of highly paraffinic oils with low aromatic content, with potential for use as spray oils, and the utilisation of their residues in the preparation of oil‐soluble neutral and overbased calcium sulphonates, to be used as detergentdispersant additives for crankcase lubricating oils.
Regeneration of used lubricating oils and use of their residues in the preparation of water‐soluble sodium sulphonates for use as surfactants.
Reducing the aromatic and sulphur content of kerosene for eventual employment as a carrier solvent for household in secticide.
Performance characteristics of oil‐in‐water mixtures in a journal bearing using different bearing materials
Authors: Nabhan M. B. 
Published: July 2006

AbstractOil‐in‐water (o/w) mixtures have an interesting property that has attracted the attention of tribologists, namely, that they can form thicker hydrodynamic films than those inferred from their rheological properties. The oil phase is believed to separate out on the metal surface in concentrated contacts lubricated with o/w mixtures. In this paper the performance characteristics of water‐based oils have been systematically explored for their film‐generating capabilities. The lubrication properties of o/w lubricants are studied and compared in a journal bearing rig assembly with different bearing materials. The rig is run under increasing loads and speeds in conditions pertinent to hydrodynamic lubrication. The rig has been able to operate with o/w mixtures at a concentration as low as 10 vol.%. However, the results have shown that the bearings exhibited signs of high eccentricities with o/w mixtures compared to Engineering Sciences Data Unit (ESDU) predictions. This behaviour has been attributed to shear rate effects on water‐based lubricants.
Bearing grease deterioration
Authors: Gafitanu M. D. , Farcas F. , Hagiu G. D. , Tiron M. C. 
Published: July 2006

AbstractAbout 80% of bearing mountings are grease lubricated. This has many advantages, such as eliminating complicated oil cooling systems, and better organisation of the available space in machine tools and aircraft. However, the bearing service life is reduced by grease deterioration. Many papers give recommendations concerning regreasing intervals but information concerning grease deterioration and service life is poor. This paper presents theoretical and experimental work concerning grease film thickness estimation and its deterioration. An equation relating grease service life to the main influencing factors is proposed. We measured grease film thickness by the global electrical resistance method. Grease deterioration is illustrated by electron microscopy.
Thickening effects of interactions between engine oil additives
Authors: Bartha L. , Kis G. , Auer J. , Kocsis Z. 
Published: July 2006

AbstractAdditives of low and high molecular weight used as performance enhancers in engine oil formulations can interact through their polar functional groups to form associates and complexes. These often have a significant thickening effect that could substitute for viscosity and viscosity‐index improvers. We therefore investigated the stability of these associates to thermal degradation, oxidation, and mechanical decomposition, in an attempt to seek information about their feasibility.
Load‐carrying capacity of lubricated and dry sliding elements
Authors: Kozma Mihály 
Published: July 2006

AbstractThe factors influencing the load‐carrying capacity of tribological contacts are reviewed. The load‐carrying capacity depends in part on the lubrication regime, and hydrodynamic, hydrostatic, and elastohydrodynamic lubrication are discussed. In some circumstances, lubrication is not possible. The parameters of dry rubbing are described, and approaches to the design and operation of dry bearings are discussed, particularly the choice of suitable non‐metallic materials for use in the wear couple.
The effect of aromatic hydrocarbons in lubricant base oils on the efficiency of adsorptive additives
Authors: Tsinghua Rong Fu , Qiu Yansheng 
Published: July 2006

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 conditions.