bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cyclic alkyl disulphides as tribological additives
Authors: Verma V. K. , Singh R. , Bhattacharya A. , Tripathi A. K. 
Published: July 2006

AbstractThe use of sulphurised natural oils, fats, hydrocarbons, terpenes and aromatic sulphides, disulphides and poly‐sulphides, as antiwear and extreme‐pressure lubricant additives, has already been established. However, the potential of cyclic disulphides merits attention.The present paper describes the synthesis and evaluation of 0.5% solutions of certain cyclic disulphides as tribological additives, namely 3‐alkylimino‐5‐(N‐methylphenyl)amino‐1,2,4‐dithiazolines, in paraffin oil, on a four‐ball test rig with 12.7 mm diameter steel bearing balls as test specimens.All the additives in general, and 3‐propylimino‐5‐(N‐methylphenyl)amino‐1,2,4‐dithiazoline in particular, exhibited remarkably good antifriction and EP activity, showing a decrease in the coefficient of friction and an appreciable increase in the load‐carrying capacity of the lubricant as indicated by a higher load wear index. The wear surface topography of the used test specimen was studied using scanning electron microscopy.
Zinc and molybdenum dithiocarbamates — antioxidant additives
Authors: Parenago O. P. , Vipper A. B. , Kuz'mina G. N. 
Published: July 2006

AbstractZinc and molybdenum dithiocarbamates are used as effective additives in lubricants of various types. Following earlier reported investigations on their antifriction and antiwear properties, it was found that zinc and molybdenum dithiocarbamates had some antioxidant capabilities, so investigations have been carried out to compare the influence of zinc and molybdenum dithiocarbamates and dithiophosphates on the antioxidant properties of lubricating oils over a wide range of temperatures. The antioxidant activity of a number of synthesised additives was determined by a kinetic method in model conditions; the antioxidant properties of these additives were also compared in more severe conditions. It was found that the effectiveness of metal dithiocarbamates depends on the oxidation test conditions. The influence of zinc and molybdenum dithiocarbamates on the antioxidant properties of lubricating oils increases in the presence of zinc dithiophosphate and calcium phenate.
Preparation and tribological performance of lanthanum alkoxyborate
Authors: Fenfang Li , Boshui Chen , Junxiu Dong 
Published: July 2006

AbstractLanthanum isooctoxyborate (LaIOB) was prepared as an additive, and the antiwear and friction‐reducing properties of base oil containing the compound were evaluated with an MS‐800A four‐ball friction tester and HQ‐1 friction machine. The chemical states of tribochemical species on the rubbing surfaces were determined by X‐ray photoelectron spectroscopy (XPS). The results indicate that LaIOB possesses good antiwear and friction‐reducing properties. The XPS analysis shows that LaIOB can be triboreduced to La2O3 and B2O3 during friction.
Role of complexation in the interaction between antiwear and dispersant additives in lubricants
Authors: Guerret‐Piécourt C. , Grossiord C. , Le Mogne T. , Martin J.‐M. , Palermo T. 
Published: July 2006

AbstractChemical interactions between antiwear and dispersant additives have been investigated in the case of mixtures of molybdenum dithiophosphates and nitrogenous compounds. Different types of behaviour have been observed in the friction measurements: in some cases, the additives led to antagonistic effects; in other cases, no (or weak) interactions occurred. Complementary analyses by infrared spectroscopy, transmission electron microscopy, and surface analysis were performed in order to understand the mechanisms of these interactions and to provide new insights that cannot be obtained otherwise. The explanations for these different types of behaviour include: the formation of molybdenum complexes in the bulk oil phase; the stability of those complexes; and the significance of steric effects. The goal of this work is to discover the means to optimise the structure and the nature of oil additives in order to limit the antagonistic effects between these additives.
Effect of alkenes on the antiwear mechanism of dialkyl hydrogen phosphites
Authors: Minami Ichiro , Hong Hyun‐Soo , Mathur Naresh C. 
Published: July 2006

AbstractThe antiwear performances of dialkyl hydrogen phosphites were investigated using a pin‐on‐disc tester under boundary lubrication. Pure phosphites were synthesised, and simple model lubricant systems were used to obtain clear observations. Di(cyclohexyl) hydrogen phosphite in squalane showed excellent antiwear performance, whereas di(n‐hexyl) hydrogen phosphite showed poor performance. Surface analyses were performed, which suggested that: (1) effective antiwear performance was achieved by the formation of a protective film of iron phosphate on the rubbing surface; (2) alkenes were effective in preventing corrosive wear, so better antiwear performance can be achieved when there are alkenes in the solution; and (3) di(cyclohexyl) hydrogen phosphite may undergo pyrolysis to eliminate cyclohexene, which plays an important role in anti‐wear behaviour.
Aggregation of carbon black particles in oil in the presence of olefinic copolymers and an ashless dispersant
Authors: Bezot P. , Hesse‐Bezot C. , Diraison C. 
Published: July 2006

AbstractThe simultaneous action of olefin copolymers (with (DOCP) or without (OCP) a dispersant function) and an ashless dispersant, polyisobutylene (PIB) succinimide, on the aggregation kinetics of carbon black (CB) suspensions, chosen to model sootladen oils, has been studied. It was observed that OCP or DOCP alone does not stabilise the suspensions, whereas the presence of PIB succinimide alone stops aggregation after one hour, during which, however, a slight increase in the mean size of the aggregates is noticeable. The addition of OCP or DOCP to PIB succinimide does not modify the long‐term stabilisation of the suspension, but avoids the slight increase in the mean size of the aggregates observed during the first hour after the addition of PIB succinimide.
Polyfunctional PIB succinimide type engine oil additives
Authors: Bartha L. , Deák Y. G. , Hancsók J. , Baladincz J. , Auer J. , Kocsis Z. 
Published: July 2006

AbstractThe physical and chemical properties of polyisobutylene (PIB) succinimide and polyisobutylene polysuccinimide type dispers‐ants for engine oil have been studied. Differences in the enhancement or diminution of detergent‐dispersant, viscosity‐index‐improving, and antiwear effects were observed for different combinations of various functional additives and succinimide dispersants, depending on their chemical structure. Owing to the higher concentration of performance packages presently required for engine oils, the detrimental interactions of additives might increase, resulting in a reduction of the detergent‐dispersant, viscosity‐index‐improving, and antiwear efficiency, as well as unfavourable gelation processes. Fourier‐transform infrared spectrometry, gel permeation chromatography, and bench tests for screening engine oil additives were used to determined relationships between the properties of lubricating oils and the composition of additives. The advantages of well balanced and selected succinimide combinations in a performance package with high detergent‐dispersant efficiency were demonstrated.
Tribology in electrical environments
Authors: Bhel Har Prashad 
Published: July 2006

AbstractThis paper presents an overview of the author and others' work on the analysis of bearings and lubricants in electrical environments, and discusses recent advances in the study of the behaviour and response of rolling‐element bearings, hydro‐dynamically lubricated journal and thrust bearings, and lubricants, under the influence of an electric current. Bearings operating in electrical environments undergo specific and complex phenomena that affect bearing life, e. g., through crater formation and lubricant deterioration, and thus have to be studied in particular ways.
Antifriction action of engine oil additives
Authors: Vipper A. , Zadko I. , Karaulov A. , Ermolaev M. 
Published: July 2006

AbstractThe mechanism of the antifriction action of engine oil additives remains unclear. In order to elucidate this, tribological tests of various additives were carried out using friction machines and a multi‐cylinder engine. Investigation of the friction surfaces was carried out using Auger electron spectroscopy. Comparative tests revealed compounds capable of increasing the thermal stability of the lubricating layers and decreasing the friction coefficient over a wide range of temperatures. An interrelation was established between the efficiency of the antifriction action of additives and their influence on the composition and thickness of the surface layers. The most effective antifriction action is due to the localisation of tribochemical processes of formation of secondary structures in thinner surface layers. The results obtained can explain the behaviour of zinc and molybdenum dithiophosphates and dithiocarbamates, and detergents of different composition and basicity, and their influence on the antifriction properties of engine oils.
The effect of molecular composition on the oxidative behaviour of group I base oils in the presence of an antioxidant additive
Authors: Adhvary A. , Erhan Sevim Z. , Singh I. D. 
Published: July 2006

AbstractThe response of base oil hydrocarbons to additive molecules is fundamental to any lubricant formulation. To have this understanding it is important to have complete knowledge of the base oil hydrocarbon composition. The work reported here is a study of a series of API Group I base oils showing the effect of various structural parameters during oxidation with an antioxidant additive (zinc dialkyldithiophosphate, ZDDP). To understand this complex base oil‐additive interaction pattern, a combination of chromatographic and spectroscopic methods has been adopted. The results show that certain NMR‐derived base oil structural parameters can be used as an index of the additive response in conjunction with column chromatographic and FTIR absorption data. It is also observed that saturated molecules, i.e., iso‐ and normal paraffins and naphthenes, behave differently towards an antioxidant additive, and the total additive response is the result of all the interactions in the system.
Calculation of oil‐film thickness in journal bearings running at varying rotational speeds
Authors: Kozma Mihäaly 
Published: July 2006

AbstractThere are many methods of calculating the properties of lubricated hydrodynamic sliding bearings running at variable loads, but, in some cases, sliding bearings of heavy‐duty machines run under constant load and at variable speeds; this can lead to reduced film thickness in the bearing and boundary lubrication. The minimum oilfilm thickness in such a bearing needs to be calculated so that the proper lubricant viscosity can be selected to reduce solid‐solid contact during machine operation. In this study, a method is presented for calculating the film thickness of sliding bearings operating with alternating rotational directions. The results of the calculations show that the squeeze effect can develop enough load‐carrying capacity to prevent solid‐solid contact between the rubbing surfaces during operation, provided the change of direction of rotation is quick enough.
The influence of surface material and topography on the wall effect of grease
Authors: Czarny Ryszard 
Published: July 2006

AbstractThe phenomenon of grease slip in the boundary layer of a lubricating pipe or a journal bearing is discussed here. A correlation between this phenomenon and the grease structure has been found. Based upon earlier work, it has been shown that a generalised Casson rheological model as well as a proposed yield stress distribution in the lubricant wall layer are useful for an analytical description of the phenomenon. A Couette rheometer was used for testing. As a result of the investigations it is shown that the wall material significantly affects the yield stress distribution in the boundary layer. Essential differences in the stress values are found, especially for plastics and metals.
Temperature‐dependent effects in base oils: Carbon‐13 NMR spin‐lattice relaxation time and viscometry studies
Authors: Kapur G. S. , Sarpal A. S. , Bhatnagar A. K. 
Published: July 2006

AbstractCarbon‐13 NMR spin‐lattice relaxation time (T1) data have been used to study the molecular dynamic aspects of base oils with different physical properties. Relaxation time measurements have been carried out on a few model compounds and a number of mineral base oils at various temperatures (273–373 K). Effective correlation time (°C) and rotational mobility data obtained for the model compounds and base oils have provided evidence of relationships between molecular flexibility and the temperature dependence of viscosity. It is possible to determine the average carbon alkyl chain lengths and the molecular weights of the base oils from the ratio of the T1 values of Cβ and Cint carbons and the optimised value of the microviscosity factor (fr), respectively. A qualitative correlation between Arrhenius energies (Ea) for microscopic motion and macroscopic bulk properties such as viscosity and viscosity‐temperature characteristics has been observed. Base fluids having better viscosity‐temperature characteristics were also associated with lower values of Ea for micro‐ as well as macroscopic processes.
The antiwear synergism between an organotin compound and a ZnDDP
Authors: Junbing Yao 
Published: July 2006

AbstractA four‐ball tester was used to evaluate the antiwear performance of an organotin compound, stannic stearate, plus a zinc dialkyldithiophospate (ZnDDP). The results indicate that stannic stearate combined with ZnDDP exhibits excellent antiwear properties in a paraffin‐based oil. The tin compound could also improve the antiwear performance of two commercial engine oils, SH/CD 15W‐50 and SE 15W‐40, which resulted in a reduction of the oil temperature and less oxidation of the oils.
Formation and frictional properties of boundary lubricating and surface‐modified layers at elevated temperatures
Authors: Konchits V. V. , Korotkevich S. V. , Kim C. K. 
Published: July 2006

AbstractThe influence of heating on the properties of lubricating layers formed on steel by inactive and chemically active lubricant components has been studied by electrical probe methods. Model experiments combining X‐ray photoelectron spectroscopy analysis and measurements of friction and electrical characteristics in static and dynamic point contact have shown the approach to be promising in separate studies of the properties of the physically adsorbed layer (A‐layer) and chemisorbed layer (D‐layer) of deposits.It has been confirmed that D‐layers can be formed on metal surfaces at moderate temperatures (T ∼ 200°C) by both active additives and inactive components of mineral oil. Zinc dialkyldithiophosphate additives provide higher load‐bearing capacity of the A‐layer compared to pure mineral oil and can form D‐layers on steel at relatively low temperatures (of about 100°C). Lubricating layers with different physicomechanical and frictional properties can be formed depending on the chemical origin of the lubricating medium and the temperature regime.
The effects of surface irregularities on the performance characteristics of flexible finite journal bearings lubricated with couple stress fluids
Authors: Elsharkawy Abdallah A. , Guedouar Lotfi H. 
Published: July 2006

AbstractA numerical solution for the elastohydrodynamic lubrication of finite journal bearings is presented. Couple stress effects resulting from blending the lubricant with various additives are considered. Elrod's cavitation algorithm, which automatically predicts film rupture and reformation in the bearings, is implemented in the solution scheme. A simple elastic model is used to describe the elastic deformation of the bearing liner. Furthermore, the effects of surface waviness on the performance of the bearing are incorporated into the analysis. A comprehensive study illustrates the effects of couple stress, liner flexibility, and surface waviness on the steady‐state performance of finite‐width journal bearings. The results show that these effects should be considered at higher values of the eccentricity ratio.
Temperature, flow, and eccentricity measurements in a journal bearing with a single axial groove at 90° to the load line
Authors: Costa L. , Miranda A. S. , Claro J. C. P. , Fillon M. 
Published: July 2006

AbstractParametric experiments were conducted to analyse the influence of some supply conditions on the performance of a steadily loaded journal bearing. The temperature distribution on the internal surface, the flow rate, and the bearing eccentricity were measured for different sets of operating conditions, under variable supply conditions. Quantitative information was provided which showed the effect of both shaft speed and applied load on maximum bush temperature and flow rate. It was observed that flow rate was moderately affected by load and significantly affected by rotational speed, oil supply temperature, and supply pressure. The maximum bush temperature was moderately affected by supply pressure and load, and significantly affected by shaft speed. For low applied loads, the attitude angle was markedly affected by supply pressure. The experimental results also showed that for a small groove length there was a variation in bush temperature in the axial direction in the groove region.
A theoretical study of two‐dimensional grease flow in regions with discontinuities
Authors: Radulescu Alexandru V. , Bonneau Dominique , Hajjam Mohammed 
Published: July 2006

AbstractThis paper presents a theoretical analysis of two‐dimensional grease flow through an asymmetric discontinuity. The behaviour of the fluid is described using Navier—Stokes equations, numerically solved by the finite‐element method. The FLFI program was used for this purpose. For this type of discontinuity, the velocity profile in the lubricant film, the shape and the dimensions of the stagnant core, the flow capacity, and the pressure distribution have been obtained. The results are useful in the design of bearings, if one considers the discontinuities in the carrying region as orifices, canals, or pockets for lubrication.
Tribological properties of P‐ and N‐containing organic compounds as potential extreme‐pressure and antiwear additives
Authors: Xia Yanqiu , Liu Weimin , Xue Qunji 
Published: July 2006

AbstractAn amine salt of an alkoxylphosphate (a P‐ and N‐containing organic compound, PN) was synthesised. Its extreme‐pressure, antiwear, and friction‐reducing properties were evaluated as an additive in liquid paraffin and a mineral oil. Tests were performed on a four‐ball friction and wear tester with an AISI 52100 steel ball self‐mated pair and the results were compared with those of sulphurised olefin (SO), zinc di‐n‐butyldithio‐phosphate (ZDDP), and dibutylphosphite (DBP). The morphologies of the worn steel surfaces were observed using a scanning electron microscope, while the binding energies of some typical elements on the worn surfaces were determined using X‐ray photoelectron spectroscopy. The additives were found to increase the load‐carrying capacity and to reduce wear and friction coefficient considerably. PN as an additive exhibits better load‐carrying, antiwear, and friction‐reducing properties than SO, ZDDP, and DBP under the same test conditions.
Composition—property correlations in some lubricating oil base stocks
Authors: Khan H. U. , Anwar M. , Nautiyal S. P. , Agrawal K. M. 
Published: July 2006

AbstractThe dependence of properties on the composition of lubricating oil base stocks (LOBS) available from Indian refineries has been studied. It has been observed that pour point is greatly influenced by the saturated component of the base stocks, whereas viscosity and viscosity index are greatly influenced by the aromatic content. The effect of various components on the viscosity/shear stress versus temperature behaviour of LOBS samples has also been investigated.
An investigation into the molecular orientation of sheared liquid crystalline boundary films
Authors: Nakano Ken 
Published: July 2006

AbstractThe molecular orientation of a nematic liquid crystal (4‐pentyl‐4′‐cyanobiphenyl, 5CB) in a shear flow between parallel plates was examined using infrared absorption spectroscopy; surface anchoring, film thickness, sliding velocity, and voltage between the parallel plates were independently investigated. Infrared absorbance of the C‐N stretch vibration was measured at the point where the direction of the vibration coincided with the long axis of each 5CB molecule. The molecular orientation depended on the product of the sliding velocity U and the film thickness D, i. e., UD. The effects of surface anchoring appeared to be stronger for lower UD. Calculated results for absorbance, based on a continuum theory, agreed well with experimental ones. The effective viscosity under the same conditions was also calculated, and was increased by a low voltage for lower UD with parallel orientation surfaces. This indicated the possibility of active control of the friction coefficient. With perpendicular orientation surfaces, even without any voltage, the effective viscosity increased with a decrease of UD, which indicated the possibility of a ‘smart lubricant’ the viscosity of which could be adequately controlled by varying the operating parameters of the mating surfaces.
The behaviour of friction modifiers under boundary and mixed EHD conditions
Authors: Castle R. C. , Bovington C. H. 
Published: July 2006

AbstractThe behaviour of a range of model and commercial friction modifiers (FMs) has been evaluated under elastohydrodynamic (EHD) and boundary lubrication conditions. Using a series of long‐chain carboxylic acids, it has been shown that measured boundary friction coefficients (BFCs) decrease with increasing chain length, unsaturation level, temperature, and concentration. Base oil polarity was found to have no effect under these conditions. Commercial oleate esters in synthetic base fluids gave lower BFCs than nitrogen‐containing compounds under the same conditions. This difference was observed over a range of concentrations and temperatures. The friction performance of formulated oils under mixed and full‐film EHD conditions was found to be dependent on FM, base oil, and detergent type. Under boundary conditions, friction was found to vary with FM type, but the effect of changing the base oil and the detergent system was negligible.
An indirect electric field effect on the friction of boundary‐lubricated contacts
Authors: Jiang H. , Wong P. L. , Meng Y. , Wen S. 
Published: July 2006

AbstractTo achieve significant friction variations by means of an externally applied voltage, it is found to be more effective to impose an electric field on the area surrounding a tribopair rather than directly through the contact. Using a new applied electric field setup, the friction behaviour of ceramic‐metal tribopairs, lubricated with an aqueous emulsion, is investigated. The potential affects the surface characteristics during the instant that the surface is out of rubbing contact. Consequently, the nominal frictional behaviour differs from that with no potential effect. The unexcited, excited, and post‐excited friction results for six different ceramic‐metal couples using a pin‐on‐disc tester are presented, and their characteristics are summarised.