bluuebunny/crossref_metadata_2025_split huggingface dataset:
Action mechanism of 35S‐containing antiwear and EP additives
Authors: Herdan J. M. , Negoita N. 
Published: July 2006

AbstractAntiwear and extreme‐pressure additives labelled with 35S were synthesised by reacting 35S2Cl2 with isobutylene and treating the adduct with potassium xanthate, or by labelling the unlabelled compound with elemental 35S in boiling carbon di‐sulphide. Static adsorption tests of the labelled additives on iron or copper specimens show an adsorption increase with temperature. The data are in good agreement with the results of thermal analysis of the additive as such or mixed with iron or copper powder. The behaviour of the oil solutions containing labelled additives on a friction machine emphasised the formation of superficial layers on a metallic surface containing the reaction products of the additive decomposition compounds with the metal. The thickness of these layers remains nearly constant during the test but increases with normal load. Pyridine washing of the specimens removes adsorbed layers whereas chemisorbed layers remain on the metallic surface.
A hydrodynamic lubrication model for the deep‐drawing process
Authors: Mahdavian S. M. , He D. 
Published: July 2006

AbstractA steady hydrodynamic lubrication model that includes the pressure viscosity factor has been developed for the deep‐drawing process. Equations for lubricant film thickness, radial and drawing stresses are presented. Analysis reveals that the pressure viscosity factor has a significant influence on estimating lubricant film thickness and radial and drawing stresses.
Computer simulation of turbine oil oxidation. 1: Consumption of a hindered phenol antioxidant in model hydrocarbon systems at 115°C
Authors: Igarashi Jinichi , Yoshida Toshio 
Published: July 2006

AbstractComputer simulation of the inhibited oxidation of model hydrocarbon systems representing turbine oils of different composition, hexadecane/tetralin mixtures containing di‐tert‐butyl pcresol (DBPC), has been achieved using the kinetic and mechanistic information obtained from fundamental hydrocarbon autoxidation and inhibition studies. The oxidation life, the time to complete consumption of DBPC and its reactive intermediates, was calculated using previously reported and newly measured absolute rate constants for reaction involved. The results of this calculation of oxidation life were in good agreement with values experimentally determined. The oxidation life has been found to decrease with increasing amount of tetralin in the mixtures. This can be explained by the increased rate of consumption of antioxidants, caused by an increase in the rate of free radical formation, via the direct reaction of hydrocarbons with oxygen, and via the homolytic decomposition of hydroperoxides. The observed decrease in oxidation life, however, is not significant, despite the fact that the addition of tetralin considerably increases the rate of free‐radical formation. The relatively low sensitivity of oxidation life to the rate of free‐radical formation caused by the addition of an easily oxidisable substrate can be attributed to the occurrence of a direct oxidation of antioxidants. That is, kinetic analysis for the consumption of antioxidants disclosed that antioxidant consumption mostly occurred not through the inhibition of oxidation, but through direct oxidation. The direct oxidation of antioxidants obeys the rate equation ‐d[AH]/dt = k6[AH]1.0[O2]1.5 where k6 can be calculated, at various temperatures, from Arrhenius parameters obtained in this study (log (A/M−1s−1) = 9.6 and Ea = 22.6 kcall mol).
Tribological studies of some N, S, and Cl containing extreme pressure additives
Authors: Bhattacharya A. , Singh T. , Singh A. P. , Singh R. , Verma V. K. 
Published: July 2006

AbstractThe antiwear and EP properties of certain p‐chlorophenyl groups containing nitrogen and sulphur open‐chain and cyclic compounds, in paraffin oil, were evaluated in a four‐ball test. The performance of the additives were compared with a commercially available sulphur‐phosphorus reference additive. All the additives, in general, exhibited good EP activity at different loads as compared to paraffin oil and the reference additive. However, the cyclic additives, e.g., 2‐phenyl‐3‐phenylimino‐5‐p‐Cl‐phenylamino‐1,2,4‐thiadiazolidine, and 2‐amino‐5‐p‐Cl‐phenylamino‐1,3,4‐thiadiazole, were found to possess good antiwear and EP properties in comparison to the plain paraffin oil, reference additive, and open chain additives. The wear surface tribochemistry and topography were studied using Scanning Auger Electron Spectroscopy (AES) and Scanning Electron Microscopy (SEM) techniques, respectively.A comparative EP activity evaluation of 1‐p‐Cl‐phenyl‐2,5‐dithiohydrazodicarbonamide and 3‐p‐Cl‐phenylimino‐5‐(N‐methylphenyl)amino‐1,2,4‐dithiazoline on steel bearing balls of different composition was undertaken to assess the suitability of replacing chromium alloy steel balls with cheaper carbon steel balls. The additive, 3‐p‐Cl‐phenylimino‐5‐(N‐methylphenyl)amino‐1,2,4‐dithiazoline exhibited its effectiveness on the alloy steel as well as low carbon steel bearing balls.A plausible explanation for the enhanced activity of additives is suggested and efforts made to correlate the effect of substituents and structure on the efficiency.
New data on the mechanism of antiwear action of zinc dithiophosphates in lubricating oils
Authors: Vipper A. B. , Karaulov A. K. , Mischuk O. A. 
Published: July 2006

AbstractZDDP reacts with oil‐soluble copper salts to form complex compounds and these compounds can substantially surpass the initial additive in the effectiveness of antiwear and antioxidant action. Application of AES allows us to establish the influence of ZDDP and complex compounds formed by it on the structural state of the friction surfaces. The specific nature of action of these complex compounds lies in minimisation of the oxidation processes in the surface microvolumes of the lubricating medium, the consequence of which is the localisation of tribo‐chemical processes of secondary structure‐film formation in the thinner layers. On the whole, the results obtained offer evidence of the existence of certain interrelations and generality of the processes producing antiwear and antioxidant action by zinc dithiophosphate additives in lubricating layers.
The mechanism of synergism between ZDDP and CeF3 additives
Authors: Lian Yafeng , Xue Qunji , Zhang Xuxhou , Wang Hanqing 
Published: July 2006

AbstractThe interaction of zinc dialkyldithiophosphate (ZDDP) with cerium fluoride and cerium dioxide in lithium grease has been studied for friction, wear, and EP characteristics on a four‐ball and SRV tester. The combination of ZDDP and cerium trifluo‐ride has been shown to be beneficial in reducing wear, especially over a long period of friction and with increasing EP load. The test results show that adding cerium dioxide to lithium grease does not improve the antiwear and friction performance of the paste. The analytical results of X‐ray photoelectron spectrum (ESCA, XPS) reveal that ZDDP inhibits the decomposition of cerium fluoride and improves its film‐forming property. The wear scar reaches a minimum at an atomic concentration ratio of 3P:2Zn:1S:25F, and an atomic concentration ratio of 2S:2P:1Zn:4F gives the highest EP load. The scratch test results show that combining ZDDP with cerium trifluoride improves the tenacity of the surface film. The stabilisation of cerium trifluoride by ZDDP is proposed.
Friction and wear characteristics of organic thiophosphoro derivatives — a critical appraisal
Authors: Anand O. N. , Singh A. K. , Kumar Vijay , Bisht R. P. S. 
Published: July 2006

AbstractThe friction‐ and wear‐reducing characteristics of a number of oil soluble sulphurised and phosphosulphurised derivatives for automotive and industrial applications have been reviewed. A critical appraisal of the suggested causes and mechanism of friction reduction and antiwear characteristics has been made. A review of the investigations carried out so far indicates that the creation of in situ films of simple inorganic salts, such as molybdenum disulphide, iron sulphide or phosphates of low shear strength and lamellar structures, does not appear to be the primary cause of low friction and wear.The authors have, therefore, undertaken a programme to synthesise and study the chemistry and tribochemical reactions in relation to friction and wear characteristics of hydrocarbon‐soluble thiophosphoro derivatives of alkyl phenol, alcohols and fatty esters, in order to establish relationships between the reactivity, chemical nature and crystal structure of films formed on rubbing surfaces, and antifriction and antiwear characteristics. Molybdenum salts of various phosphorothio derivatives of pentadecylphenol and lauryl oleate of specific structures have been synthesised, and the friction and wear properties of their blends in mineral oil base stock have been studied. It can be clearly inferred from the results that type of bonding between sulphur, phosphorus and molybdenum, and reactivity of these derivatives with rubbing surfaces, determine their friction‐reducing and antiwear characteristics. Their reactivity with iron and the nature of films formed are under investigation.
Effect of coatings on thermal conditions of EHL
Authors: Bogdański Stanisław 
Published: July 2006

AbstractThe thermal EHD model of rectangular contact has been applied to analysing the effect of coatings on thermal conditions in EHL. The model takes into account variation of oil viscosity along and across the oil film according to the Barus formula. The solution has been obtained by means of the Newton‐Raphson method. The effect of the coating has been examined by comparison of the temperature distributions in the oil film and on the surfaces of rollers for the cases with and without coating. In addition, the oil film shapes and minimum values, the pressure distributions and traction coefficients, have also been compared.
Influence of oil‐soluble copper salts on catalytic oxidation of lubricating oil in laboratory conditions and in a single‐cylinder engine
Authors: Vipper A. B. 
Published: July 2006

AbstractDuring oxidation of an engine oil under laboratory conditions, and testing in a single‐cylinder gasoline engine, it has been found that oil ageing depends on the copper content, in particular the oil‐soluble copper salt content. The latter considerably intensifies engine oil oxidation, loss in bearing weight, and piston deposit formation. Several regularities in the oil ageing process were found. It was noted that interaction of copper naphthenate with zinc dithiophosphate essentially influences this process.
Colloidal thiophosphorus calcium salt as antiwear additive
Authors: Delfort Bruno , Born Maurice , Daoudal Bertrand , Chivé Agnes 
Published: July 2006

AbstractThis paper describes the synthesis of an oil‐soluble colloidal calcium thiophosphate by a direct route. It consists of the reaction of calcium oxide or hydroxide with tetraphosphorus decasulphide and water in the presence of a surfactant such as a calcium alkylaryl sulphonate in an organic medium. Reaction and micellisation occurred simultaneously according to a one‐step process. The product is characterised by a high calcium, phosphorus and sulphur content. The colloidal nature of the product has been confirmed by dialysis. The 31P‐NMR spectrum showed signals characteristic of a blend of different calcium thiophosphates, plus calcium phosphate. The product could be defined as a core of different calcium (thio)phosphates surrounded by a calcium alkylaryl sulphonate shell, according to a reverse micelle type association in oil. This compound was evaluated as an antiwear additive in a 130 Neutral Solvent mineral oil by anti‐wear and extreme‐pressure four‐ball tests. The extreme‐pressure characteristics depend on the concentration of mineral colloidal core in oil. The antiwear properties are a function not only of the concentration, but also of the colloidal core/surfactant shell ratio. Thermogravimetric analysis of these colloidal species shows a weight loss in the 350°C to 450°C range, due to surfactant degradation. The further evolution of weight loss up to 900°C demonstrates the high thermal stability of the colloidal calcium (thio)phosphate core.
Reducing the effect of three‐body abrasive wear by adding polymeric powder to lubricating grease
Authors: Ali W. Y. , Mousa M. O. , Khashaba M. I. 
Published: July 2006

AbstractThe present paper reports on work aimed at improving the abrasive wear resistance of surfaces lubricated with contaminated greases. The intended improvement can be achieved by reducing the effect of wear occurring between the abrasive particles and the rubbing surfaces. Different polymeric thickeners in powder form, such as high‐density polyethylene (HDPE), low‐density polyethylene (LDPE), polyvinylchloride (PVC), polyamide (PA6) and polymethylmethacrylate (PMMA), were added to lithiumbased grease.The wear resistance and the coefficient of friction of cylindrical steel specimens were examined using a cross‐pin test machine. The test machine provides concentrated contact under mixed lubrication conditions. Wear was measured on the stationary test specimen by the wear scar diameter, using an optical microscope, with an accuracy of ±1 μm. The frictional torque generated between the rubbing surfaces was measured using a full bridge strain gauge measuring cell attached to the stationary test specimen holder. The experiments were performed using clean and contaminated lubricating greases to which Air Cleaner Fine Test Dust (SCFTD) was added to the greases at a concentration of 10 wt.%.The results show that the effect of the abrasive contaminants can be reduced by the addition of polymeric powders. However, the addition of polymer to lubricating grease at relatively high concentration (more than 35 wt.%) has no effect on the antiwear action of the lithium grease. Further, the addition of polymeric powder with a particle size relatively greater than that of the contaminant can be considered as a useful method of eliminating the cutting process of the three‐body abrasive mechanism introduced by the presence of the hard contaminant particles.
Creep transport of grease subjected to low frequency vibrations
Authors: Lundberg Jan , McFadden Terry 
Published: July 2006

AbstractCreep transport is defined as the velocity of a mass of grease when it is subjected to vibrational and gravitational forces. The method developed to assess this, measured the time taken for the grease submitted to low frequency vibrations to creep, under the influence of gravity, a specified distance down a cylindrical tube. The vibrations were characteristic in frequency and amplitude to those commonly experienced by commercial rotating machinery. Vibrational excitation was found to have a widely varying effect on creep transport of grease, suggesting that this parameter may be important in the selection of greases for specific applications where vibration is present; in contrast, the NLGI number gave almost no indication as to the effect of vibration on a particular grease. A vibration number related to the creep rate is suggested for grease selection. The vibration number correlates to the yield stress of the grease, with higher yield stress correlating to higher creep rate. However, no correlations between creep rate and base oil viscosity or bleed rate were found.
Development of engine crank‐case oil formulations for oxidation stability using indigenously blended lubricant base‐stocks
Authors: Sharma R. K. 
Published: July 2006

AbstractWith changing engine design putting more emphasis on fuel economy, emissions control and low engine oil consumption, the quality levels of engine crank‐case oils are changing fast. With this in view, experimental work has been carried out towards the development of engine crankcase‐oil formulations meeting the required levels of oxidation stability.Three lubricant base‐stocks meeting the physico‐chemical characteristics of engine oils, prepared from lubricant streams obtained from different refined crude oils and one re‐refined engine oil base‐stock were used. The viscosity index of these base‐stocks ranged from 84 to 98, and carbon residue from 0.06 to 2.2. The antioxidant used in the formulation was of ZDDP type, and the detergents were calcium and barium sulphonates.The base‐stocks were evaluated using the IIP oxidation stability test, to determine their suitability in the formulation of engine crankcase oils. The base‐stocks were then dosed with additives, and tested again by the IIP Oxidation Stability Bench Test, for their additive response.The final formulations were then tested on a CRC‐L‐38 standard engine test prescribed in Indian Standard 13656:1993 for IC Engine Crankcase Oils with respect to bearing corrosion and piston deposit tendencies. It was observed that higher VI lubricant base‐stocks and the re‐refined engine oil base‐stock gave better test performance in both bench and standard engine tests.
Trends in gear oil additives
Authors: Herdan J. M. 
Published: July 2006

AbstractOf the total amount of additives produced and sold in the world, gear oil additives are the second largest group, after the engine oil additives. According to the purpose of the finished lubricant, these additives can be classed as either additives for automotive gear lubricants or additives for industrial gear lubricants. Although the main function of such additives is the same for both types of lubricants, namely to reduce friction and wear and avoid surface fatigue, permanent deformation of the tooth, and excessive wear, the requirements that these lubricants have to meet are different. The most important specifications for automotive gear lubricants are, in the USA, API GL‐1—GL‐6, and MIL L 2105 A—2105 D, respectively, whereas in Europe manufacturers tend to have taken GL‐4 or GL‐5 as a basis, and added their own supplementary requirements. Industrial gear lubricants are manufactured according to US Steel 224 specification, DIN 51517/3, and AGMA 250.04. The gear oil additives themselves are based on sulphur and phosphorus chemistry, but other chemicals are introduced into the additive packages to ensure oxidation stability, anti‐corrosion protection, copper compatibility and better seal compatibility. Boron compounds are shown to improve the antiwear and extreme‐pressure properties of the lubricants, as well as oxidation stability, thermal stability and detergency. Rig and bench tests demonstrate the benefits of adding boron compounds to fully formulated GL 5 oils and to classic sulphur‐phosphorus additive packages for automotive and industrial gear oils.
Exploring possible connections between tribology and osteoarthritis
Authors: Furey Michael J. 
Published: July 2006

AbstractThis paper is part of a continuing study aimed at exploring possible connections between tribology and mechanisms of synovial joint lubrication and degeneration. In a separate paper, the focus was on the tribological behaviour of natural and ‘normal’ synovial joints. The central thrust or purpose of the present paper is to stimulate discussion of ‘abnormal’ joint behaviour, in particular, degenerative joint disease or osteoarthritis, from the point of view of a tribologist, and in the light of our findings on cartilage wear. Some provocative questions are raised. For example, can a lack of ‘proper’ synovial joint lubrication or a specific biochemical ‘anti‐wear’ agent lead to degeneration of the joint or more rapid removal of articular cartilage? Does osteoarthritic articular cartilage have poorer resistance to wear than ‘normal’ cartilage? It is not argued that arthritis is a tribological problem. However, it would seem that tribological connections with degenerative joint disease — and possibly other forms of arthritis — are indeed possible, but complex.
The tribological behaviour and tribochemical mechanism of action of oxovanadium (IV)‐dithiophosphate
Authors: Guo‐Xu Chen , Ren‐Gen Xiong , Jun‐Xiu Dong 
Published: July 2006

AbstractVanadium (IV)‐oxo‐dicyclodithiophosphate (VDTP) was prepared and its additive properties evaluated using a four‐ball machine. The results show that VDTP exhibits better extremepressure performance, but lower antiwear activity, when compared with ZDTP. The reaction film composition, characterised by scanning Auger microscopy (SAM), X‐ray photoelectron spectroscopy (XPS) and diffractometer surface techniques, reveals that the antiwear and friction layer containing vanadium oxide, phosphate/phosphide, and sulphide, prevent the rubbing pairs from contacting directly, resulting in better extreme‐pressure and antiwear behaviour.
Formation, structure, and properties of lubricant‐derived antiwear films
Authors: Willermet P. A. , Carter R. O. , Schmitz P. J. , Everson M. , Scholl D. J. , Weber W. H. 
Published: July 2006

AbstractIn recent years, surface analytical methods that determine structure have been combined with methods that measure elemental composition and oxidation states, to yield an improved understanding of lubricant‐derived tribofilms. Methods assessing the mechanical properties of thin films have also been applied to tribofilms with thicknesses of the order of nanometres. These methods, in combination with chemical and physical studies of bulk lubricant systems and assessments of lubricant behaviour in tribological environments, have made it possible to describe comprehensively film forming mechanisms, structures and tribological properties. This paper outlines the initial results of such an attempt, focusing on zinc dialkyl dithiophosphates and overbased detergents in model systems and engine oils.
Comparison of the fretting wear of 100Cr6/100Cr6, Si3N4/Si3N4 and Si3N4/100Cr6 contacts in lubricated and dry conditions
Authors: Vižintin J. , Kalin M. , Podgornik B. , Novak S. 
Published: July 2006

AbstractThe fretting wear behaviour of bearing steel against bearing steel, silicon nitride against silicon nitride, and silicon nitride against bearing steel, was investigated under lubricated and dry conditions. Amplitudes in the intermediate 5 to 50 μm range, and test durations from 10 to 360 min, were studied. Light microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X‐ray spectroscopy (EDS) were employed to determine the detailed nature of the friction and wear processes.In the silicon nitride against silicon nitride contact, brittle fracture of Si3N4 grains, and tribochemical reaction creating an amorphous layer on the mechanically damaged surface, were found. The main mechanism of fretting wear in the case of bearing steel against bearing steel contact was delamination. In the silicon nitride against bearing steel contact, chemical reactions predominated.
Sleeve dampers for externally pressurised gas journal bearings
Authors: Uneeb M. , Gohar R. 
Published: July 2006

AbstractAn approximate small eccentricity analysis is presented, for finding the threshold of fractional speed whirl instability of an unloaded double plane admission hybrid gas journal bearing supported by a non‐rotating externally pressurised gas journal bearing sleeve damper. A line source is assumed at the feeding planes to the gas film with flow and load correction factors to account for the discreteness of the feed holes (details of these factors are presented in a related publication). The results show that, by careful selection of the design parameters, it is possible almost to remove fractional speed whirl instability from the bearing arrangement. Some practical designs of sleeve dampers are also presented.