bluuebunny/crossref_metadata_2025 huggingface dataset:
A system for wear prediction in lubricated sliding contacts
Authors: Stolarski T. A.
Published: July 2006

A 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

Wax 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

The 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

The 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

A 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

In 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 grease

The 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

There 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

The 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

Belt‐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

Most 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

This 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

The 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

Succinimide 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

Sulphonation 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

Oil‐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

About 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

Additives 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

The 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

This 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.
Triboemission as a basic part of the boundary friction regime: A review
Authors: Warsaw C. Kajdas , Furey M. J. , Ritter A. L. , Molina G. J.
Published: July 2006

This 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 apparatus.
Frictional performance of lithium 12‐hydroxystearate greases with different soap fibre structures in sliding contacts
Authors: Yamamoto Y. , Gondo S.
Published: July 2006

The effect of the fibre structure of the grease on the frictional performance of lithium 12‐hydroxystearate greases with different fibre lengths was investigated in face, line, and point contact sliding tests. At high sliding speeds where the lubrication regime was practically hydrodynamic, the coefficient of friction of the base oil alone was lower than that of the greases. The coefficient of friction was roughly estimated as follows: base oil < long‐fibre grease < medium‐fibre grease < short‐fibre grease. The supply or replenishing capability of the grease played a critical role in maintaining hydrodynamic lubrication. At high contact pressures, the short‐fibre grease was superior in frictional performance to the long‐fibre grease due to the firm fibre network structure of the latter. In mixed and boundary lubrication regimes, the greases were superior in frictional performance to the base oil, since the soap fibres of the greases had a superior load‐carrying capacity. The long‐fibre grease, with a firm fibre structure, offered better frictional performance than the short‐fibre one.
Thermal effects in cylindrical journal bearings of high‐speed gearboxes
Authors: Strzelecki Stanisław , Spałek Jacek
Published: July 2006

The 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 gearboxes.
Effects of lubricant viscosity on the mixed lubrication of a piston ring pack in an internal combustion engine
Authors: Hamatake Toshiro , Wakuri Yutaro , Soejima Mitsuhiro , Kitahara Tatsumi
Published: July 2006

A theoretical analysis is presented of the mixed lubrication of a piston ring pack. The analysis comprises Patir and Cheng's average flow model and Greenwood and Tripp's asperity interaction model, and is developed to consider the shear thinning effect of a non‐Newtonian fluid, multigrade lubricant. The friction characteristics of the piston ring pack for both monograde and multigrade lubricants are investigated. It is found that a decrease in the lubricant viscosity is effective in reducing the friction loss, although this increases the boundary friction at the beginning of the expansion stroke. The friction characteristics are markedly affected by the shear thinning effect when multigrade lubricants are used.
Transient thermo‐elastohydrodynamic lubrication of gear teeth
Authors: Mihailidis A. , Panagiotidis K.
Published: July 2006

During a gear mesh cycle, load, rolling and sliding velocities, curvature, and temperature change rapidly. In this paper, a transient, thermo‐elastohydrodynamic lubrication model is presented that has been used to study the lubrication parameters at 250 contact points along the path of a contact. The working flanks were assumed to be smooth. The line load was calculated at every contact point, using the finite‐element method. Dynamic loading was not considered. The steady‐state temperature field of the working flanks was used to obtain the surface temperature at the inlet of each contact point, determined by an experimental‐analytical method presented previously. In this model, the lubricant is considered to follow the Ree‐Eyring constitutive equation. The influences of both pressure and temperature on density, thermal conductivity, and specific heat of the lubricant are also taken into account. Results are presented for an FZG type A gear pair lubricated with an FVA No. 4 reference oil; these include film shape, pressure and temperature distributions, as well as friction coefficient.
Influence of temperature on the tribochemical reactions of hexadecane
Authors: Kajdas Czeslaw , Makowska Monika , Gradkowski Marian
Published: July 2006

This paper investigates the tribochemical reactions of n‐hexa‐decane proceeding in a tribosystem lubricated by n‐hexadecane at ambient and elevated temperatures. It is hypothesised that, at ambient temperature, reactions are mostly initiated by the mechanical action of the system, and at elevated temperature (200°C) thermochemical reactions should be dominant. An experimental study was performed using a ball‐on‐disc machine with steel‐on‐steel mating elements. To analyse wear tracks, Fourier transform infrared microspectrophotometry (FTIRM) and electron spectroscopy for chemical analysis (ESCA/XPS) were used. To investigate chemical changes in the bulk lubri cant, gas chromatography coupled with mass spectrometry (GC/ MS) was applied. The results provide clear evidence for the hypothesis that two types of oxygenation processes of n‐hexa ‐decane under boundary lubrication conditions should be considered. The first, at ambient temperature, is controlled by the mechanical action and the second is clearly controlled by temperature. The analytical techniques applied gave evidence of the formation of some reaction products from hexadecane under boundary lubrication conditions. These products include compounds having Fe‐O bonding (salts and chelates), carbonyl compounds, and iron carbide.
Tribological behaviour of Langmuir—Blodgett films of polymerised 22‐tricosenoic acid and 22‐tricosenoic acid/CdS nanoparticles
Authors: Zhang Pingyu , Xue Qunji , Du Zuliang
Published: July 2006

Langmuir—Blodgett (LB) films of 22‐tricosenoic acid and of 22‐tricosenoic acid polymerised in the presence of an electron beam, and in situ composite LB films of 22‐tricosenoic acid/CdS were prepared. The friction and wear behaviour of the LB films were investigated with a ball‐on‐block one‐way reciprocating friction tester. The structures and morphologies of the LB films were analysed and observed using atomic force microscopy. The wear resistance of the LB films was increased after polymerisation of the acid, and the composite LB film of 22‐tricosenoic acid/CdS showed better wear resistance because the inorganic nanocores of CdS acted to resist wear and to carry load. The LB film of the acid experienced structural changes during the friction process.
Optimisation of molecular structure for traction fluids
Authors: Tsubouchi T. , Hata H. , Yoshida Y.
Published: July 2006

According to the guidelines for the molecular design of traction base fluids obtained from a previous study, more than 100 chemical compounds have been synthesised. Employing 61 naphthenic compounds whose chemical structures have been clearly identified, the optimisation of molecular structure has been studied regarding the compatibility of high‐temperature traction coefficient and low‐temperature fluidity. As a result, the requirements for molecular structures for high‐performance traction base fluids have been clarified.
Lubricant oils additivated with polymers in EHD contacts: Part 1. Rheological behaviour
Authors: Bercea M. , Paleu V. , Bercea I.
Published: July 2006

This paper reports on the influence of a polymer additive on the traction behaviour of a mineral oil investigated using a two‐disc machine at different temperatures and contact pressures. A semi‐empirical approach was used for determining the effective lubricant rheological parameters ‐ the elastic shear modulus, the viscosity of the lubricant, and the limiting and Eyring stresses ‐ in elastohydrodynamic contacts. Using this approach, the effect of polymer concentration on the rheological parameters that appear in both the Johnson‐Tevaarwerk and Bair‐Winer models was quantified. The influence of operating conditions, such as pressure, oil temperature, and polymer concentration, on the traction coefficient, limiting shear stress (from the Bair‐Winer model), Eyring stress (from the Johnson‐Tevaarwerk model), shear modulus, and apparent viscosity was also investigated.
Tribological properties and tribochemical mechanism of lanthanum and boron compounds in oil
Authors: Jiang S. , Wei Y. L. , Cheng X. Y. , Chen B. S.
Published: July 2006

Lanthanum dialkyldithiophosphate (LaDDP) was synthesised. The tribological properties of a combination additive of LaDDP and an organo‐borate (OB) in oil were evaluated with a four‐ball test machine. The results show that the combination of LaDDP and OB gives better load‐carrying capacity and anti‐wear and friction‐reducing properties than the individual components. Rubbed surfaces after the friction tests were investigated using X‐ray photoelectron spectroscopy, Auger electron spectroscopy, and microhardness testing. The results indicate that a boundary film is composed of deposit films (including La2O3 and B2O3), chemical reaction films (including FeSO4, FePO4, and FeS), and a tribodiffusion layer (including La and B). Lanthanum can promote the decomposition of OB and the tribodiffusion of boron. From a mass spectroscopy analysis a tribochemical mechanism is suggested.
Action mechanisms of boundary lubrication additives ‐ a review, part II
Authors: Choudhary R. B. , Jha M. K.
Published: July 2006

A wide range of literature hs been published in the period 1950–2000 concerning emerging concepts of the action mechanisms of boundary lubrication additives. Some aspects of these additives in terms of chemical nature, surface adsorption, surface film generation, thermal stability, thermodynamics of contact surfaces, and rise in surface temperature, as reported in this literature, are reviewed in the present paper.

Part I of this paper appeared in Lubrication Science, 16, 4 (2004) 405–19.

It has been observed that the chemical constituents of boundary lubrication additives, particularly of organosulphur and organo‐sulphur‐phosphorus origin, are very complex in nature and no comprehensive details are readily available. Regarding action mechanisms, researchers have suggested different mechanisms for different conditions. However, information on the thermodynamics of surfaces and thermal stability of additives is not easily obtainable. Other details, such as the effect of sliding speed, operating load, surface roughness, and material design, are not covered here. Overall, the literature reveals that attempts to correlate additive characteristics with boundary lubrication activity have met with limited success, and efforts aimed at achieving ever‐increasing performance levels continue.

In the first part, the authors examined the chemical nature of boundary lubrication additives, surface films, and surface temperature. In this second part, they look at thermal stability, and antiwear and extreme‐pressure activity.
Extending the retention of friction‐reducing capability in low‐phosphorus engine oils
Authors: Jensen R.
Published: July 2006

In advanced fuel‐efficient engine oils containing molybdenum dialkyldithiocarbamate, Mo(dtc)2, as a friction‐reducing additive, the friction‐reducing capability is gradually depleted with mileage accumulation and is dependent on the presence of other additives, such as zinc dialkyldithiophosphate, Zn(dtp)2. Indeed, it has been shown that the loss of the friction‐reducing capability of Mo(dtc)2 coincides with the depletion of Zn(dtp)2. The next generation of oils will specify a lower phosphorus content (e.g., 0.08% in ILSAC GF‐4 and even lower in the specification after GF‐4) to reduce the detrimental effects of phosphorus on catalyst systems. This will necessitate the use of less Zn(dtp)2, which could have an adverse effect on the retention of friction‐reducing capability.

The aim of this study was to determine if the retention of friction‐reducing capability could be maintained or even increased at 0.05% phosphorus with newer molybdenum trinuclear, Mo3S7(dtc)4, additives. To facilitate the study, a modified laboratory‐based ageing test was developed which correlated with the loss of friction‐reducing capability in the Sequence VIB engine test. This ageing test was used to evaluate model blends of Mo3S7(dtc)4 with Zn(dtp)2 at 0.05% phosphorus and added antioxidants. The results indicate that it is possible to extend the retention of friction‐reducing capability. However, whether or not it can be extended beyond the current drain intervals is still an open question.
An extended FE strategy for transition from continuum damage to mode I cohesive crack propagation
Authors: Comi Claudia , Mariani Stefano , Perego Umberto
Published: July 2006

An integrated strategy is proposed for the simulation of damage development and crack propagation in concrete structures. In the initial stage of damage growth, concrete is considered to be macroscopically integer and is modeled by a non‐symmetric isotropic non‐local damage model. The transition to the discrete cohesive crack model depends on the local mesh size and is driven by an analytical estimate of the current bandwidth. When a crack is introduced in the model an extended finite element approach is used to follow the propagation path, independent of the background mesh. The proposed methodology is tested on a notched tension specimen and then applied to the analysis of a wedge splitting test. Copyright © 2006 John Wiley & Sons, Ltd.
Effects of molecular characteristics and processing conditions on melt‐drawing behavior of ultrahigh molecular weight polyethylene
Authors: Kakiage Masaki , Yamanobe Takeshi , Komoto Tadashi , Murakami Syozo , Uehara Hiroki
Published: July 2006

The effects of molecular characteristics and processing conditions on melt‐drawing behavior of ultrahigh molecular weight polyethylene (UHMW‐PE) are discussed, based on a combination of in situ X‐ray measurement and stress–strain behavior. The sample films of metallocene‐ and Ziegler‐catalyzed UHMW‐PEs with a similar viscosity average MW of ∼107 were prepared by compression molding at 180 °C. Stress profiles recorded at 160 °C above the melting temperature of 135 °C exhibited a plateau stress region for both films. The relative change in the intensities of the amorphous scattering recorded on the equator and on the meridian indicated the orientation of amorphous chains along the draw axis with increasing strain. However, there was a substantial difference in the subsequent crystallization into the hexagonal phase, reflecting the molecular characteristics, that is, MW distribution of each sample film. Rapid crystallization into the hexagonal phase occurred at the beginning point of the plateau stress region in melt‐drawing for metallocene‐catalyzed UHMW‐PE film. In contrast, gradual crystallization into the hexagonal phase occurred at the middle point of the plateau stress region for the Ziegler‐catalyzed film, suggesting an ease of chain slippage during drawing. These results demonstrate that the difference in the MW distribution due to the polymerization catalyst system dominates the phase development mechanism during melt‐drawing. The effect of the processing conditions, that is, the including strain rate and drawing temperature, on the melt‐drawing behavior is also discussed. The obtained results indicate that the traditional temperature–strain rate relationship is effective for transient crystallization in to the hexagonal phase during melt‐drawing, as well as for typically oriented crystallization during ultradrawing in the solid state. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2455–2467, 2006
Sense of coherence as a protective factor for demoralisation in women with a recent diagnosis of gynaecological cancer
Authors: Boscaglia Nadia , M. Clarke David
Published: July 2006

Background: Demoralisation is a dysphoric mood state commonly seen in the medically ill. Its core features comprise hopelessness, helplessness, loss of purpose and meaning, despair, and existential distress. Sense of Coherence (SOC) is a quantifiable dispositional orientation that captures the character traits likely to protect against demoralisation. In this study, we hypothesised on theoretical grounds that a strong SOC would be associated with lower levels of demoralisation in the context of gynaecological cancer (GC).

Method: One hundred and twenty women with a recent (<12 months) diagnosis of GC were recruited from outpatient clinics. Participants were interviewed and completed questionnaire measures of demoralisation and SOC. A multiple regression analysis was performed using the five subscales of the Demoralisation Scale as predictor variables and SOC as the dependent variable.

Results: Together, the five subscales of the Demoralisation Scale accounted for 60% of the variance in SOC.

Conclusions: The results supported the hypothesis, suggesting that SOC may be protective against demoralisation in the context of serious illness. Larger, multivariate studies that examine additional variables (such as coping) would be required to further clarify the relationship between SOC and demoralisation. In the meantime, clinicians may want to consider efforts to enhance SOC in patients. Copyright © 2006 John Wiley & Sons, Ltd.
Adenovirus pneumonia in infants and factors for developing bronchiolitis obliterans: A 5‐year follow‐up
Authors: Castro‐Rodriguez Jose A. , Daszenies Cecilia , Garcia Marianela , Meyer Rodolfo , Gonzales Ramiro
Published: July 2006

To describe clinical, pulmonary function, and chest tomography profiles in a 5‐year follow‐up of infants with adenovirus pneumonia and determine the factors that potentially contributed to the development of bronchiolitis obliterans (BO). We prospectively assessed 45 hospitalized infants with adenovirus pneumonia with additional follow‐up for 5 years. At the end of the study, pulmonary function by impulse oscillometry technique (IOS) and chest tomography were performed in the 38 surviving patients (mean 5.7 years of age). We divided the population between those who developed chest tomography evidence of BO and those who did not. Most of the children developed adenovirus infection before 2 years of age. During the 5 years of follow‐up, almost half (47.4%) developed BO. Children who developed BO had significantly more respiratory compromise (intensive care admission, need for mechanical ventilation and for oxygen therapy, and systemic corticosteroid and beta agonist use) during their adenovirus pneumonia episode than those who did not develop BO. Only 33.3% of children with BO had normal impedance compared with 85% in the no BO group. Children who developed BO had significantly higher levels of Zrs, R5, X5 and predicted Zrs, R5, and X5 and frequency. However, there were no differences in the beta 2 agonist response between the children with and without BO (94% vs. 80%, respectively). This study represents the spectra of adenovirus pneumonia ranging from relatively mild to severe and fatal cases. Children with severe pulmonary compromise are usually more prone to develop BO. Pediatr Pulmonol. 2006, 41:947–953. © 2006 Wiley‐Liss, Inc.
Quantification of siderophages in bronchoalveolar fluid in transfusional and primary pulmonary hemosiderosis
Authors: Priftis Kostas N. , Anthracopoulos Michael B. , Tsakanika Constantina , Tapaki Georgia , Ladis Vassilis , Bush Andrew , Nicolaidou Polyxeni
Published: July 2006

Transfusional iron overload may occur in the lungs. We hypothesized that quantitating siderophages in the bronchoalveolar fluid (BALF) of heavily transfused patients may prove to be a useful tool in determining lung iron overload in transfusion‐dependent patients. The study included six patients (7–20 years) with thalassemia major (TM) who had received multiple blood transfusions, one with hereditary spherocytosis (four blood transfusions) and one with sickle cell disease (never transfused); they were compared to three children with idiopathic pulmonary hemosiderosis (IPH) (2.5–7.0 years) as positive controls. Fiberoptic bronchoscopy with bronchoalveolar lavage was performed in seven patients under general anesthesia for elective surgery and the rest were bronchoscoped electively under sedation. Spirometry was also performed in eight patients. There was no significant difference between children with TM and IPH in siderophages as percentage of total count (95% CI −31.0 to 1.5, P = 0.068). There were positive relationships between both mean serum ferritin values during the preceding year and the total number of units of transfused blood, and percent siderophage count among multiply transfused patients (P = 0.010, P = 0.052, respectively); similar findings were noted for the Golde score (P = 0.001, P = 0.031, respectively). None of the patients showed lung function impairment. In conclusion, in this small study, we found that the BALF of multiply transfused patients with benign hematological disorders contain similar numbers of siderophages to that of patients with IPH; this is strongly suggestive of secondary pulmonary hemosiderosis. The correlation between the patients' serum ferritin, and the BALF siderophages suggests that the later may serve as a marker of pulmonary iron overload in patients requiring blood transfusion and appear to be more sensitive than standard pulmonary function tests. Pediatr Pulmonol. 2006, 41:972–977. © 2006 Wiley‐Liss, Inc.
Magnetic history dependence of the AC susceptibility of GdSr2RuCu2Oz
Authors: Polichetti M. , Adesso M. G. , Zola D. , Vecchione A. , Gombos M. , Ciancio R. , Fittipaldi R. , Cimberle M. R. , Pace S.
Published: July 2006

The AC susceptibility of GdSr2RuCu2Oz samples has been measured as function of the temperature, at different AC field amplitudes (from 1 to 16 G) and frequencies (in the range [10‐103 Hz]), applied parallel to the major axis of the sample, and without any additional DC magnetic field. In particular we have analysed the temperature region above the Superconducting critical temperature Tc, and around the magnetic transition temperature Tm. Our attention has been focused on the differences between the curves measured after cooling the sample in zero AC field (Zero AC Field Cooling or ZAFC) and those measured after cooling in presence of a non zero AC field (AC Field Cooling or AFC). Clear differences between the ZAFC and AFC susceptibility curves appear in the temperature range between Tc and Tm, and they depend on the measuring field amplitude and frequency. Finally, indications of a spin glass behaviour in Ru‐1212 system observed from its AC magnetic response are reported (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Correct dissociation limit for the exchange‐correlation energy and potential
Authors: Gritsenko Oleg , Baerends Evert Jan
Published: July 2006

Local and semilocal functionals like the local density (LDA) and generalized gradient approximations (GGA) fail to provide correct behavior during the dissociation of electron pair bonds: the asymptotic potential energy curve is wrong, the dissociation in the heteronuclear case leads to partially ionic instead of neutral atoms, and the time‐dependent density functional theory (TD‐DFT) excitation energies behave incorrectly upon bond stretching. We demonstrate that such errors can be avoided by the use of an orbital‐dependent exchange‐correlation (xc) functional. Such a functional needs to incorporate, in contrast to the popular exact exchange functional, the electron correlation effects. The demonstration is given for the electron pair bond of a diatomic molecule AB with just one orbital on A and one on B. This simple two‐orbital model affords an analytical inversion of the density response function, which is used to show that the orbital‐dependent xc functional described previously, possesses the correct dissociation limit for the xc energy and potential. The correct potential (xc hole potential in the symmetric case AB, for example, for the dissociating H2 molecule) properly describes strong nondynamical (left–right) electron correlation, while in the heteroatomic case (A ≠ B) it develops an additional “counter‐ionic” step behavior in its response part, which is needed to ensure proper covalent dissociation of the AB bond (and proper covalency at long bond distances). © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006