bluuebunny/crossref_metadata_2025 huggingface dataset:
An approach to the study of elasto‐plastohydrodynamic lubrication in the wire drawing process. Part 2: Theoretical predictions
Authors: El‐Butsh A. M. A. , Ei‐Badrawy R. S. , Mokhtar M. O. A.
Published: July 2006

The generalised Reynolds' equation for Newtonian and non‐Newtonian fluids, as applied to the wire‐drawing process, together with the plasticity and energy equations have been adopted in solving the elasto‐plastohydrodynamic lubrication problem in the wire‐drawing process. The equations have been solved numerically using a finite difference technique with Gauss‐Siedel iterative scheme to predict hydrodynamic behaviour and to correlate the forming parameters to the lubrication behaviour in an endeavour to find the optimum operating conditions for maximum precision and productivity. The effect of using either Newtonian or non‐Newtonian lubricants on the process parameters has been also studied, to predict the most suitable lubricant type.

The results indicate that the increase in the flow behaviour index increases the pressure gradient in the work zone, with a consequential reduction in oil film thickness. Also the minimum film thickness is highly influenced by the drawing speed.

It can be concluded that the isothermal solution renders lower drawing stress than the adiabatic solution. The maximum shear stress, and hence the power loss, increases with the increase in die convergence angle.
The study and application of an anti‐adhesive wear lubricant for use in deep drawing
Authors: Hu X. , Xiang F.
Published: July 2006

This paper reports on an anti‐adhesive wear lubricant (NL2) used in deep drawing, containing as additives B, N compounds and zinc (cyclic) polymethylenedithiophosphate. It covers the synthesis of these additives, their properties, and the friction and wear mechanism of NL2 in the deep‐drawing process. These are studied by means of a strip bending drawing tester, a four‐ball tester, and IR, SEM, and EDAX analysis. The results show that the new additive gives good adhesive wear protection in deep drawing.
Visualisation of fuel‐lubricant interaction on the cylinder surface in the combustion chamber of SI engines
Authors: Kovács A.
Published: July 2006

Visualisation of fuel component penetration and release into the lubricating oil layer covering the combustion chamber wall has been achieved, using a laser‐induced fluorescence (LIF) test technique. Experimental data show that fuel component penetration into the oil layer contributes not only to unburnt hydrocarbon emissions in spark ignition (SI) engines, but also to engine oil degradation. Fuel components accumulated in the oil layer are transferred to the bulk in ring belt zones, after a measurable residence time. A significant difference in film thickness between the oil layer on the combustion‐chamber wall during the intake/compression sequence, as against the expansion/exhaust sequence, indicates that in the ring belt zones and above, engine oil viscosity, and hence load‐carrying capacity, is influenced by fuel absorption/desorption in the engine oil.
A study of the tribological properties of some 1,3,4‐thiadiazole type lubricant additives
Authors: Cao Lin , Wei Dan‐Ping , Wang Rulin
Published: July 2006

The synergistic effects between the group containing S and P, hydroxyl group and a 1,3,4‐thiadiazole ring in the same molecule have been studied by investigating the tribological properties of three 1,3,4‐thiadiazole derivatives. The possibility of predicting properties of additives from their chemical structures is discussed. The results indicate that introducing a long carbon chain with a hydroxyl group (LCCWHG) into the side chains of a 1,3,4‐thiadiazole ring can effectively enhance its antiwear ability and that dimercaptothiadiazole adduct of dialkyl thiaphosphoric acid (DAODTA) can have good extreme pressure performance and excellent antiwear properties.
The tribological properties and action mechanism of Schiff base as a lubricating oil additive
Authors: Wan Yong , Liu Wei‐Min , Xue Qunji
Published: July 2006

In this paper, an organic compound containing a nitrogen element, Schiff base, is synthesised, and its tribological characteristics are evaluated by four‐ball and Timken machines. Schiff base possesses friction‐reducing and antiwear properties, especially under low load. Results from X‐ray photoelectron spectroscopy (XPS) reveal that the binding energy of N1s increases in the boundary film. Differential thermal analyses (DTA) indicate that Schiff base reacts with iron powder, forming complex compounds through hydroxy and azomethine. An action mechanism, with surface‐complex compound films being formed on the surface, is proposed.
Microtribology, squeeze, and friction of the colloidal layer
Authors: Mazuyer Denis , Tonck Andrél , Georges Jean‐Marie , Loubet Jean‐Luc
Published: July 2006

Lubricant films containing colloidal overbased calcium salts have particular effects on detergency and on the wear process. The mechanical properties of such boundary films are very dependent on the process conditions, and are essentially a result of physico‐chemical transformations of the colloid. Three types of films were compared: a film obtained by the drying of the base solvent, a film due to the compaction of the colloid between two steel surfaces, and a friction film obtained with this type of lubricant. Adsorption, compaction, and shear transformations induce a solid film.

The pressure effect on the frictional behaviour of these colloidal films has been investigated using a surface force apparatus for low contact pressure (104 to 106 Pa), and using tribometers supporting heavy loads for the analysis of the high pressure domain. Above a critical pressure, evaluated at 106 Pa, the colloidal film does not flow, but forms a compacted mattress sliding on the surface plane and squeezing a molecular layer of lubricant.
Influence of aldehydes in make‐up oils on antioxidation properties
Authors: Minami Ichiro
Published: July 2006

The addition of more antioxidant to aged oils is not always effective in preventing autoxidation. To investigate this phenomenon, a solution of antioxidant and model oxide in hexadecane was examined by means of the induction period method. Aldehydes were found to be the most active species for reducing the antioxidation properties of zinc dialkyldithiophosphate (ZDTP), 2,6‐di(tert. butyl)‐4‐methylphenol (DBPC), and N‐phenyl‐1‐naphtylamine (PNA). Carboxylic acids, ethers, alcohols, and ketones to some extent reduced the induction period with these antioxidants. Esters showed almost no influence on reducing their antioxidant properties.

Reaction of ZDTP with aldehyde was studied by means of 31P‐NMR analysis. It was found that (a) aldehydes accelerate conversion of ZDTP, and thereby reduce its antioxidant performance. (b) Conversion of ZDTP in the presence of aldehydes under oxygen at 130° in hexadecane and no reaction was observed under nitrogen at the same temperature. Active intermediates derived by the autoxidation of aldehyde were suspected. (c) Reaction of peroxycarboxylic acid with ZDTP took place smoothly at 0°C under nitrogen to give bis(dialkylthiorophosphoro)disulphide and the corresponding carboxylic acid. Reaction of hydroperoxide with ZDTP took place at room temperature to give oxo‐hexa(dialkylphosphorothiorothionato)‐tetrazinc.

Two mechanisms for decomposition of ZDTP promoted by aldehydes, namely hydroperoxide and peroxycarboxylic acid mechanisms, are proposed. Reaction of peroxycarboxylic acid with DBPC or PNA barely took place at room temperature: for these antioxidants, the peroxycarboxylic acid mechanism would be excluded. Radical species derived by the autoxidation of aldehydes were considered as active intermediates.

It is considered that classification of the types of oxides that exist in used oils in the key to optimising the effect of re‐added antioxidants.
An investigation into the antiwear, antioxidation, and anticorrosion behaviour of some derivatives of 2,5‐dimercapto ‐1,3,4‐thiadiaxole
Authors: Wei Dan‐Ping , Cao Lin , Wang Lu‐Lin
Published: July 2006

It appears that the comprehensive performance of 2,5‐dimercapto‐1,3,4‐thiadiazole derivatives is dependent upon both the type and the structure of the chains attached to the carbon atoms in the 2 and 5 positions of the thiadiazole ring. For the side chain of the monosulphide type R‐S‐, the type and location of substituents have an important influence on additive performance. In the case of the side chain of the disulphide type, X‐SS‐, the presence of the phosphorus‐containing group has a significant effect on multifunctionality.
Local order in surface ZDDP reaction films generated on engine parts, using EXAFS and related techniques
Authors: Belin M. , Martin J. M. , Tourillon G. , Constans B. , Bernasconi C.
Published: July 2006

The study of reaction films generated in a mild wear lubricated process remains a topic of interest. We present in this paper the latest results obtained by the structural analysis of reaction films directly on friction surfaces. An experimental engine setup is used, in which a cam and follower system is externally driven without combustion. The system is lubricated with a base oil containing ZDDP (zinc dialkyl‐dithiophosphate). After the wear test, the engine parts are analysed by the EXAFS technique (Extended X‐Ray Absorption Fine Structure) in the Total Electron Yield configuration. It is found that the build‐up of the film greatly depends on the formulation of the lubricant, and on the test conditions. In the film formed with ZDDP, the initial Zn‐S bonding changed to ZN‐O in a completely amorphous arrangement. The nature of the wear debris is found to be very similar to the surface of the reaction film. These results are discussed in terms of microscopic wear mechanisms.
Piston ring friction loss behaviour for motored and fired reciprocating engines
Authors: Ting L. L. , Shih T. S.
Published: July 2006

A previously developed piston ring lubrication model has been further extended so that the piston ring frictional losses can be predicted in both hydrodynamic lubrication and metal‐to‐metal contact regions for various engine operating conditions. Ring friction results for two engine types are presented for both hot motoring and engine firing conditions. The hot motoring predictions were found to be in good agreement with tests. Results show that when the engine is motored, piston ring friction losses in the hydrodynamic lubrication region predominate. If the engine is fired, the losses in the metal‐to‐metal contact region become dominant due to high gas pressure and temperature effects. Ring friction loss can be significantly reduced by using low tension rings with a correct ring sliding face profile.
Effect of applied voltage on friction and wear characteristics in mixed lubrication
Authors: Yamamoto Yuji , Ono Bunji , Ura Akira
Published: July 2006

The effect of an electric field applied between rubbing surfaces on friction and wear characteristics was examined using a ballon‐disc testing apparatus under different lubrication conditions. The lubrication conditions were changed by changing the viscosity of the lubricants. By applying an electric field between the rubbing surfaces, the oxidation of the rubbing surface at the anode side is enhanced, and suppressed on the cathode side surface. The oxide film formed on the anode surface being harder than the bulk steel, the rubbing surface at the anode side was little worn, but that at the cathode side was abrasively worn. This wear characteristic could be utilised to attain favourable running‐in. The application of an electric field, however, is considered to promote the breakdown of any EHL film formed. Therefore the effect of the application of an electric field between rubbing surfaces is influenced by the lubrication condition that is being tested.
Zinc oxythiomolybdate (ZnMoO2S2) powder as a solid lubricant for high‐temperature rolling contact applications
Authors: Trivedi Hitesh K. , Gerardi David T. , Rosado Lewis
Published: July 2006

Conventional liquid lubricants being used in today's gas turbine engines will not be able to operate effectively in the hostile bearing environments expected in future turbine engines. The expected high operating temperatures (500–800°C) mandate new and innovative lubrication schemes to achieve success. Recent studies have demonstrated that a new class of solid lubricants, the complex chalcogenides or metal ocythiomolybdates, have good potential for high temperature lubrication. This paper describes the friction, wear and rolling contact endurance of three high‐temperature bearing materials using a zinc oxythiomolybdate (ZnMoO2S2) powder lubricant. Rolling contact tests were conducted using VIM‐VAR M50, micromelt T15 tool steels and silicon nitride (Si3N4) at temperatures ranging from 23°C to 649°C, using a modified ball‐on‐rod type rolling‐contact fatigue tester. Significant improvements in friction, endurance and wear were observed at all test temperatures, and with all three materials evaluated, when ZnMoO2S2 was used as a lubricant. Overall, silicon nitride exhibited the best frictional and antiwear performance. The lubricant powder exhibited the best tribological performance with T15 and M50 specimens between 177°C and 316°C. Energy Dispersive X‐Ray Analysis (EDAX) of wear tracks showed the presence of iron (Fe) on the Si3N4 specimens as well as the presence of zinc (Zn) on both the T15 and the M50 specimens.
Observation of microdispersed particles in overbased detergents
Authors: Fu X. G. , Li S. B. , Zhang J. H.
Published: July 2006

The results of electron microscopic determination of the colloidal structure of some typical lubricating oil detergents by an improved freeze‐etching method for specimen making are reported. The work establishes that the improved freeze‐etching technique provides a reliable means for observation of colloidal structure of detergents, where the conventional method does not.
Definition of the transition from fluid lubrication to mixed lubrication for rough surfaces
Authors: Liu K. , Liu X. J. , Xie Y. B.
Published: July 2006

Fluid lubrication and mixed lubrication can both be phenomena in the study of the lubrication of rough surfaces. In this paper, we take the surface as random process and, by studying the contact of surfaces which present roughness, we can put forward a method which defines the transition from fluid lubrication to mixed lubrication, by looking for the first contact point between the two surfaces. This study suggests that the transition between fluid and mixed lubrication relates to the number of asperities on the contacting surfaces, an advance on former methods. We also apply this method to piston ring/cylinder lubrication research. The results show that the transition changes with time.
The synthesis and antiwear action of tungsten dithiolate
Authors: Rengen Xiong , Junxiu Dong
Published: July 2006

Tungsten dithiolate was synthesised by the reaction of WO3 with toluene‐3,4‐dithiol (abbreviated to H2TDT), and its extreme‐pressure and antiwear properties were investigated on a four‐ball tester. The results showed that it possesses fairly good extreme‐pressure and antiwear abilities. Based on analytical results obtained by Scanning Auger Microprobe and Scanning Electron Microscopy, as well as Electron Ionisation Mass Spectra fragments, the antiwear mechanism of WTDT suggested that a permeating layer containing WC, WS2, and WO3 played an important role in the antiwear and friction‐reducing action.
Three‐dimensional incompressible flow of a gas through feed holes into an annular space of finite length
Authors: Uneeb M. , Gohar R.
Published: July 2006

This paper presents a theoretical model of the three‐dimensional flow of an incompressible gas in a concentric double‐plane admission externally pressurised gas journal bearing. Inertia effects and the discreteness of the feed holes are included. The flow map demonstrates the formation of a vena contracta at the commencement of the film, downstream of the feed holes, as well as detailed behaviour of the streaklines within the film. The pressure profile obtained shows a depression at the vena contracta, followed by a partial recovery which varies around the feed holes, depending on whether the local flow is exiting between the rows of holes or outboard towards atmosphere. A comparison is also made with a similar one‐dimensional incompressible flow solution to obtain flow and pressure factors, to account for the discreteness of the feed holes as well as inertia effects.
Lubricating oil additives and the environment — an overview
Authors: Herdan J. M.
Published: July 2006

In this paper are reported some practical considerations relating to lubricant additive manufacture, and to additivated lubricants' impact on the environment. Widely used engine oil additives are mainly dithiophosphates, overbased calcium sulphonates, succinimidic dispersants, and polymer VI improvers. Production of these additives creates a potential environmental problems due to the hazardous emissions such as H2S and HCl and sludge obtained during purification. New processes are described which lead to the reduction of toxic and other harmful pollutants.

Gear oil additives, although these may be used in lower amounts, also make for ecological problems. A high quantity of sulphur‐containing waste water is produced during manufacture of sulphurised EP additives. Some possibilities for recovering sulphur from this waste water are presented. The reduction of the chlorine content in EP additives is another important task, and new processes to produce EP additives with low residual chlorine content are discussed. Metal working fluid additives comprise emulsifiers, corrosion inhibitors, antiwear and EP additives. Their fabrication usually produces toxic and harmful residual products. Additivated lubricants may promote ecological injury. Oil leakage from engines working in harbours, parks, and entertainment areas are dangerous and difficult to avoid. To counter this, biodegradable base stocks were developed, but there are few data concerning the biode‐gradability of the additives used. Used oils are generally collected and recovered, but a significant quantity of used oil is directly burned. Burning of additivated used oils in incorrect equipment leads to dangerous emissions, such as sulphur oxides. Because sulphur‐containing additives cannot be replaced in engine oils or gear oils, the main ecological measure is the reduction of the quantity of used oils burned.
Interaction of PIB‐succinimides and other engine oil additives
Authors: Bartha L. , Deák Gy. , Kovács M. , Kocsis Z. , Vuk T.
Published: July 2006

The paper shows the results of investigations into the interactions between different types of succinimides and zinc dialkyl dithiophosphates. Various properties of additives in oil solutions were tested and examined by various methods, in order to show the existence of interactions of various strengths between different types of succinimide and ZnDDP.
Relationship between the structure of C60 and its lubricity: A review
Authors: Bo Feng
Published: July 2006

Based on analyses of the calculations of quantum theories, such as electron charge density, the energy level distribution of orbitals, and the forces between C atoms and between the molecules in C60 crystals, the author concludes that C60 crystal is a promising solid lubricant. Furthermore, owing to the unique spherical structure of its molecules, high chemical stability, and the phase transition of the crystal fullerene C60 may have some particular tribological properties that are superior to traditional graphite and MoS2, especially under crucial conditions such as high vacuum, high pressure or in a humid environment. The tribological tests that have been reported show the lubricity of fullerene C60, and the effects of the lubricating properties of C60 on some metals are also predicted.
Lubrication safety in high‐speed ball‐bearings
Authors: Olaru D. N. , Gafitanu M. D.
Published: July 2006

In a 7206 C high‐speed, mist‐lubricated ball‐bearing, both the film thickness and lubricant parameter λ in ball—race tribo‐systems have been analytically investigated in terms of starvation and thermal effects, and good correlations with experimental results were obtained for 5,000 to 35,000 rpm rotational speeds. Including a lubricant parameter in ball—race tribosystems as a safety criterion for ball‐bearings, friction losses, temperature, and limit speeds have been correlated with this criterion for a 7206 C ball‐bearing. Friction losses in ball‐outer race tribosystems have been computed for both EHD and mixed lubrication regimes. The influence of the bricant parameter on friction losses has been shown both theoretically and experimentally. A new speed limit concept including the lubricant parameter λ, has been developed by the authors.
Production of a transformer oil from paraffinic basestocks
Authors: Abou El Naga H. H. , Anis A. , Salem A. E. , Boghdady Y. M.
Published: July 2006

The work described in this paper is concerned with the production of a high quality transformer oil from local Egyptian paraffinic basestocks. Analysis showed that a neutral base oil 70N was most suitable for producing transformer oils. This neutral base oil was chemically treated with a sulphonation process. Optimum sulphonation conditions were achieved by using oleum or SO3 at a concentration of 6 wt. %. The sulphonation reaction was carried out in three stages, each with an equal portion of the sulphonating agent. The acidic oil was then neutralised with an alkaline solution. Oil colour improvement was effected using activated clay as an absorbent. Laboratory results and field trials indicated that such a treated neutral paraffinic oil meets the IEC 296 international specifications for transformer oils, with the exception of pour point (−12°C). However, such a pour point is not relevant in certain hot climatic conditions. Comparative evaluation of the treated oil with commercial transformer oils has shown its suitability.
Prediction of oxidation stability of inhibited base oils from chemical composition using an artificial neural network (ann)
Authors: Basu B. , Saxena D. , Kaul V. , Sastry M. I. S. , Mookken R. T.
Published: July 2006

Oxidation stability is the single most important characteristic of lubricants that affects their service life and high‐temperature applicability. The chemical composition of base oils determines to a large extent the oxidation stability of the lubricants. For steam turbine oils, oxidation stability is more important still, as the oil is expected to remain in the system for 10–20 years. Selection of appropriate base oils, therefore, is crucial for the formulation of turbine oils. The oxidation stability of turbine oils is estimated by three bench tests, ASTM D‐943, ASTM D‐2272, and IP 280, which vary in severity, and are all time‐consuming. In this context, the prediction of oxidation test performance (oxidation stability) of base oils from their chemical composition appears to be very attractive.
Additive—additive interaction: A study of the ep and AW performance of sulphurised jojoba oil and sulphurised xanthate in the presence of mocontaining friction modifiers
Authors: Gupta A. K. , Bhatia H. C. , Tuli D. K. , Verma A. S. , Rai M. M. , Bhatnagar A. K.
Published: July 2006

The extreme‐pressure (EP) and antiwear (AW) performance of three soluble molybdenum compounds (commercial molybdenum dialkyldithiophosphate, commercial molybdenum dialkyl dithiocarbamate, and synthesised molybdenum dialkyl dithiocarbamate), and two sulphur‐containing EP compounds (sulphurised jojoba oil and sulphurised O‐stearyl‐S‐oleyl xanthate) have been studied alone and in combination, using a four‐ball tester. The behaviour of the additives in combination has been found to be selective, and dependent on the chemistry and ratio of the additive components. In general, the addition of Mo‐type friction modifiers (FM) to sulphurised EP compounds has shown a synergism, of varying order, in their EP and AW properties.
The kinetics of degradation of styrene‐isoprene copolymer
Authors: Desai N. M. , Joshi N. C.
Published: July 2006

Viscosity modifiers are one of the most important components of multi‐viscosity grade lubricants. In use, the lubricant heats up and the ingredients degrade and deplete. In an attempt to understand the thermal and thermal‐oxidative behaviour of viscosity modifiers, we have studied the effects of heat in both inert and oxidative atmospheres. The paper describes the degradation of a styrene‐isoprene viscosity modifier studied with differential scanning calorimetry (DSC). Most of the kinetic parameters can be obtained by the application of Kissinger, Ozawa, and Augis and Bennett's simple expressions, which are special cases of Elder's formulations. The values of order, heat of degradation, and activation energy were +1.25, +1149 J·m, and 175 kJ·mole for thermal degradation in a nitrogen atmosphere, and +1.50, −6321 J·m, and 57 kJ·m for thermal‐oxidative degradation in air. The information concerning the degradation of the viscosity modifying polymers can be useful in selecting the correct polymers for envisaged application.
The effect of the aromaticity of base stocks on the viscometric properties of multigrade oils
Authors: Abou El Naga H. H. , Abd El Aziem M. W. , Mazin A. S.
Published: July 2006

The viscometric properties of multigrade oils containing base stocks with increased aromatic content have been studied. Various types of viscosity index improvers (VIIs) have been incorporated in these formulations. Viscosity measurements were carried out over a wide temperature range (from −10°C to 150°C).

The results show that increasing the aromaticity of blends induces a greater thickening effect with all types of VIIs incorporated, but by different magnitudes. This thickening effect is more pronounced at low temperatures. At high temperature and high aromaticity, the VIIs tended to acquire high swelling behaviour, which serves to mask the differences between them.

Limited changes were noticed for the viscosity index, thickening tendency, and specific viscosity of the blends tested. The shear stability of the VIIs was found to decrease with the increasing aromaticity of the blends. Such behaviour can be attributed to the swelling of the VIIs and the increase in their molecular volume, which consequently facilitated their shearing.
Friction reduction and antiwear properties of the complex of lanthanum and a phosphate
Authors: Shengrong Yang , Yubin Sun , Weimin Liu , Pingyu Zhang , Zefu Zhang
Published: July 2006

A complex of lanthanum and di‐(2‐ethyl hexyl) phosphate (DEHP) was prepared by an extractive method. The friction and wear behaviour of this complex (called LaDEHP) as an oil additive was evaluated using a four‐ball wear tester. For comparison, the friction reduction and antiwear properties of DEHP as an oil additive were also investigated. The chemical composition of the boundary film formed after wear tests was examined using X‐ray photoelectron spectrometry (XPS).

Four‐ball tests showed that the prepared LaDEHP was effective in reducing friction and wear as well as in increasing load‐carrying capacity. XPS analyses indicate the formation of iron phosphate and lanthanum oxide in the boundary films.
Rheological modification of base oils using a styrene‐isoprene copolymer
Authors: Desai N. M. , Joshi N. C.
Published: July 2006

In trying to understand the behaviour of solutions of polymer in mineral oils, a styrene‐isoprene copolymer and two mineral oils have been studied. The base oils showed Newtonian behaviour, and the polymer solution non‐Newtonian behaviour, in the temperature range 50–100°C. The variation of viscosity with shear rate can be approximated to a power law model within the same temperature range and 0–104 s−1 shear rate. The free energy of activation is used to explain the flow behaviour qualitatively.
Physical and chemical modification of zinc carboxylate‐containing lubricants by molecular structure changes
Authors: Andor J. A. , Berkesi O. , Dreveni I. , Varga E.
Published: July 2006

Twenty‐two samples of zinc carboxylates were prepared from saturated, non‐cyclic carboxylic acids with systematically altered hydrocarbon chain structures under well‐defined conditions. Essential temperature‐ and solvent‐induced changes concerning the coordination of the carboxylate group are shown using selected prepared samples, and general rules for systems containing zinc carboxylates in nonpolar media are presented.

It is shown that there are three possible structural forms for zinc carboxylates: polymeric sheet, polymeric chain, and closed tetranuclear oxo complex molecules. These forms are closely related through their physical and chemical transitions.

The results show that the spatial structure of the hydrocarbon chain is a crucial factor, besides physical and chemical conditions, limiting the possible forms of zinc carboxylates present in the system. The principles presented enable us to predict and design the behaviour of a system containing zinc carboxylate additives.
Effects of type of lubricant and shape of tooth profile upon efficiency of gear drives
Authors: Ishibashi A. , Sonoda K. , Mohammad H. Ali
Published: July 2006

To reduce energy consumption, it is important to increase the efficiency of gears used for power transmission. In the present work, the efficiencies of gear drives with standard and profile shifted involute gears are measured by changing the type of lubricating oil. A new equation for calculating efficiency is derived by taking into account the additional friction torque that depends on the shape of the teeth. The efficiencies calculated with the new equation agree well with those obtained by experiments conducted using two planetary gear drives with different tooth shapes and with different reduction ratios (u = 4. 89 and 151). The new equation is applicable to the design of gear drives with higher efficiency.
Lubrication behaviour of iron rhenate in relation to matching pairs at elevated temperatures
Authors: Dangsheng Xiong , Shizhuo Li
Published: July 2006

Iron rhenate was compounded by a chemical method, which can be reproduced during the wear process of Fe‐Re alloys at elevated temperatures. The friction coefficient of iron rhenate was determined using five types of ball material (Si3N4, Al2O3, glass, 440 C, and Hast C) matching seven types of disc material (Al2O3, 761 iron base superalloy, glass, stainless steel, bronze, copper, and Al‐Li), using a ball‐on‐disc device. The results show that the iron rhenate plays a role in lubrication from room temperature to 600°C. The lubrication behaviour is related to the nature of the matching pairs: the hardness of the materials, the compatibility of iron rhenate with the materials of the matching pairs, and the surface roughness of the disc most affect the lubrication behaviour of iron rhenate. The principle of tribologically matching pairs is proposed.
A review of ultrafine particles as antiwear additives and friction modifiers in lubricating oils
Authors: Sunqing Qiu , Junxiu Dong , Guoxu Cheng
Published: July 2006

This paper gives an overview of developments in the use of ultrafine particles in lubricating oils to reduce wear and friction. Work on several types of particles, such as graphite, MoS2, PTFE, BN, fullerene, and Cu, as well as more novel and unusual particles used as lubricant additives, is reviewed. The paper summarises the results of a number of workers in this field. The tribological mechanism by which ultrafine particles operate is considered, and some conclusions, including possible future directions for research, are drawn.
The influence of lubricating greases on rolling bearing failure
Authors: Rakić Radoslav , Rakić Zlata
Published: July 2006

Significant savings can be made by the correct use of lubricants in terms of energy consumption, replacement parts, maintenance costs and the reduction of machinery downtime, because the service life of machines is one of the most important aspects of engineering. Planned preventive maintenance means the minimisation of failures and of maintenance costs; the technology should allow identification of the tribomechanical systems in all operating conditions and of the tribological regime and duration of operation. Despite the enormous advances that have been made over the last thirty years in the theory of rolling bearing lubrication, the successful operation of rolling bearings remains highly dependent on empirical knowledge. The aim of the present study is to investigate the influence of lubricating grease on rolling bearing failure; the experimental work was carried out at a metalworking factory.
Preparation of medicinal petroleum Jelly using local petroleum Waxes
Authors: Battarjee S. M. , El‐Azim W. M. Abd , Mohamed A. A.
Published: July 2006

Petroleum waxes are mainly derived from paraffinic crudes. These waxes must be removed from lubricant base oils through a dewaxing process to avoid affecting oil performance at low temperatures. The waxes themselves have uses.

This paper describes successful attempts to select the optimum conditions for sulphonation and/or hydrogenation of local waxes to obtain medicinal macro‐ and microcrystalline waxes suitable for use in petroleum jelly blends that meet medicinal specifications.

Deoiling was carried out to separate the oil from the wax samples. Concentrated and fuming sulphuric acids were used as sulphonating agents. Sulphonation processes were carried out at different temperatures, stirring speeds, and digestion times. The optimum sulphonation conditions, which give 0.007 UV absorbance at 290 nm and the highest yield, were achieved using 28% concentrated sulphuric acid.

The optimum hydrogenation conditions were achieved using a Ni/Mo catalyst at 105°C and 60 bar for paraffin wax and 180°C and 100 bar for petrolatum, for 30 min for both types of waxes.

Analysis and field trials of the blended petroleum jelly showed that these blends meet British Pharmacopoeia specifications.
Viscometric properties of viscosity index improvers in lubricant base oil over a wide temperature range. Part I: Group II base oil
Authors: Lariviere D. , Asfour Abdul‐Fattah A. , Hage Alek , Gao J. Z.
Published: July 2006

Capillary viscometry has been employed to measure the viscosities of dilute polymer solutions over the temperature range ‐10 to 150 °C. A Group II base oil containing 95% saturates was used as solvent for an olefin copolymer (OCP), a hydrogenated diene copolymer (HDP), and a polymethacrylate (PMA). These three polymers represent the three major families of viscosity index (VI) improvers used nowadays in lubricant formulations. Intrinsic viscosities and Huggins' constants were also determined. The thickening effects of the olefin copolymer and the hydrogenated diene copolymer were found to be higher at low temperatures (e.g., 40 °C) than at higher ones (e.g., 100 °C), which phenomenon was attributed to stronger intermolecular hydrodynamic interactions at low temperatures, as indicated by the Huggins constants. For the hydrogenated diene copolymer and the polymethacrylate polymer, the viscosity increased abruptly when the temperature went below 10 °C. This unusual observation was attributed to the crystallisation of a small fraction of the base oil. Based on the intrinsic viscosity data, it was concluded that at temperatures between 10 and 150 °C, the polymer coil dimension remains a constant for the olefin copolymer and the hydrogenated diene copolymer VI improvers, but increases with increasing temperature for the polymethacrylate VI improver.
An experimental study of elastohydrodynamic central and minimum film thicknesses for various material parameters
Authors: Křupka I. , Poliščuk M. Hartl R. , Liška M.
Published: July 2006

A newly developed experimental technique, based on colorimetric interferometry, has allowed accurate measurement of central and minimum elastohydrodynamic (EHD) film thickness for a wide range of operating conditions. This study was aimed at determining the influence of various material parameters on central and minimum EHD film thicknesses. Obtained experimental data were compared with Hamrock and Dowson film thickness equations and a numerical solution presented by Venner. The results obtained confirmed that the ratio between the central and minimum film thicknesses changes significantly with both load and material parameters.
A tribological study of a ternary complex of zinc with dioxyethylenated octylphenol phosphate in water
Authors: Feng Lin , Mi Zhou , Yu‐kai Hu , Wen‐long Zhang , De‐Hua Tao
Published: July 2006

A novel aqueous antiwear additive, a ternary complex of zinc with dioxyethylenated octylphenol phosphate and triethanolamine (TXOZ + TEA), has been synthesised. Its tribological behaviour in water was evaluated using a four‐ball tester. The results indicate that the complex in water exhibits higher load‐carrying capacity than mineral oil plus ZDTP, and excellent antiwear behaviour. The elemental composition of its rubbed surface was investigated with Auger electron spectroscopy (AES), and the results of this analysis are presented in the paper. The action mechanism of the additive is also discussed.
Oil film thickness measurement by means of an optic lever technique
Authors: Glavatskikh Sergei B. , Larsson Roland
Published: July 2006

Oil film thickness in hydrodynamic bearings is a fundamental parameter influencing overall hydrodynamic bearing performance. Knowledge of this thickness allows bearing performance to be optimised. For the small hydrodynamic bearings that are usually used in laboratory test facilities, a very small sensor (e.g.,<2 mm) is required because of space limitations. Commercially available eddy‐current and capacitance sensors are too large to be mounted in the pad of such a bearing. An alternative approach is to use sensors based on optical methods, such as the optic lever technique. The main idea in this technique is to detect the intensity of a light beam reflected from a target surface. This intensity is a function of the distance between the sensor and the target. This paper reports the specific features of the optic lever technique as used for measurements of oil film thickness. The design, calibration procedure, and main characteristics of an optical sensor are discussed. A test rig for the calibration of oil film thickness sensors is also presented. The sensor response curve has two parts, linear and non‐linear; using the linear part results in high sensitivity in the micrometre range. The influence of different types of oil on the output signal of the sensor has also been investigated. Experiments with different target velocities have shown that this sensor can be used for accurate and reliable measurement of oil film thickness in hydrodynamic bearings.
Cyclic alkyl disulphides as tribological additives
Authors: Verma V. K. , Singh R. , Bhattacharya A. , Tripathi A. K.
Published: July 2006

The 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

Zinc 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

Lanthanum 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

Chemical 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

The 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

The 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

The 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

This 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

The 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.