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Showing papers in "Lubrication Science in 2010"


Journal ArticleDOI
TL;DR: In this article, it is shown that specific ionic liquids have great potential to be used as additives for tribological applications, especially for 3-Octhylthiazolium and long term stability up to temperatures of 120°C.
Abstract: In this paper, it is shown that specific ionic liquids have great potential to be used as additives for tribological applications. The results promise a high load carrying capacity; especially for the cation 3-Octhylthiazolium and long term stability up to temperatures of 120°C is given. However, only extreme pressures/anti-wear properties are examined in detail with the selected test method. Friction modifier (FM) effectiveness cannot easily be demonstrated, because of the good performance of the selected base stock. Nevertheless, ionic liquids in general did not change the FM characteristic of the base oil in a negative way. A promising potential for ionic liquids to replace a majority of additives in tribological systems is given. Methods used are Schwing-Reib-Verschleis test according to DIN ASTM D 5706, and Four Ball Tests according to DIN 51360. Mechanisms related to additives in lubricants are investigated by X-ray photoelectron spectroscopy. Copyright © 2010 John Wiley & Sons, Ltd.

54 citations


Journal ArticleDOI
TL;DR: In this paper, a four-ball machine was modified to allow the test of rolling bearings and a 51107 thrust ball bearing was used to test two different greases and the corresponding base oils.
Abstract: The reduction of the power loss generated in mechanical transmissions and the use of low friction biodegradable lubricants has been attracting considerable attention in recent times. Therefore, it is necessary to develop methods to test and evaluate the performance of such lubricants and compare them with conventional ones. In this sense, a Four-Ball Machine was modified allowing the test of rolling bearings. A 51107 thrust ball bearing was used to test two different greases and the corresponding base oils. Friction torque and operating temperatures were continuously monitored to quantify the power loss and the heat evacuation for each lubricant tested. Copyright © 2010 John Wiley & Sons, Ltd.

48 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe the nature of stick-slip based on an analysis of a 1-DOF sliding system and derive the dimensionless parameters controlling the stickslip.
Abstract: In most practical mechanical systems, sliding surfaces are utilised under the assumption that they operate smoothly. Stick-slip motion can therefore be a serious nuisance that interferes with achieving high performance in mechanical systems. The present paper describes the nature of stick-slip based on an analysis of a 1-DOF sliding system. The dimensionless parameters controlling the stick-slip are clarified by deriving the dimensionless forms of the governing equations. For a friction model that considers the dependence of the kinetic friction coefficient on the relative velocity, we find three types of sliding systems with regard to stick-slip: the unstable system, the stable system and the robust-stable system. A criterion is proposed for the fundamental design of robust-stable systems; if a sliding system is robust stable, no matter how large a disturbance is, the energy of the disturbance is dissipated perfectly, and steady sliding without any vibration is ensured. Copyright © 2009 John Wiley & Sons, Ltd.

30 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a review of recent research in molecular dynamics studies of the traction properties of hydrocarbon fluids under elastohydrodynamic lubrication, focusing on the technical problems that arise on making predictions of an oil film with a submicron thickness at the actual sliding contacts of the machine elements by at a nanoscale molecular simulation.
Abstract: This paper reviews recent research in molecular dynamics studies of the traction properties of hydrocarbon fluids under elastohydrodynamic lubrication, focusing on the technical problems that arise on making predictions of the traction properties of an oil film with a submicron thickness at the actual sliding contacts of the machine elements by at a nanoscale molecular simulation. The effect of the oil film thickness and shear rate are examined including the result of a submicron thickness simulation of the oil film using a tera-flops computer. The mechanism of the phase transition of the fluids under high pressure, the boundary slip, and the momentum transfer related to the molecular structure of the fluids are also presented. Copyright © 2010 John Wiley & Sons, Ltd.

30 citations


Journal ArticleDOI
TL;DR: In this paper, the properties of polyurea greases were synthesized, having a different number of urea groups in per polyureal thickener molecule. And the results showed that properties of the polyurean grease vary with the number of Urea groups per polyUREa molecule.
Abstract: The thickener structure of polyurea grease has a crucial effect on its properties. Therefore, it is very important to study the relationship between a thickener structure and physical and performance properties. In this study, polyurea greases were synthesised, having a different number of urea groups in per polyurea thickener molecule. Properties such as dropping point, penetration, oil separation, shear stability and four-ball wear and extreme pressure (EP) were evaluated. The result shows that properties of polyurea grease vary with the number of urea group per polyurea molecule. Based on molecular theory, the mechanisms explaining these effects are briefly discussed. Copyright © 2010 John Wiley & Sons, Ltd.

24 citations


Journal ArticleDOI
TL;DR: In this paper, the friction and wear between the piston and cylinder linings significantly affects the performance of internal combustion engines, and the presence of a coating played an important role in the performance degradation.
Abstract: The friction and wear between the piston and cylinder liner significantly affects the performance of internal combustion engines. In this paper, segments from a commercial piston/cylinder system were tribologically tested using reciprocating motion. The tribological contact consisted of aluminium alloy piston segments, either uncoated, coated with a graphite/resin coating, or an amorphous hydrogenated carbon (a-C : H) coating, in contact with gray cast iron liner segments. Tests were conducted in commercial synthetic motor oils and base stocks at temperatures up to 120°C with a 2 cm stroke length at reciprocating speeds up to 0.15 m s−1. The friction dependence of these piston skirt and cylinder liner materials was studied as a function of load, sliding speed and temperature. Specifically, an increase in the sliding speed led to a decrease in the friction coefficient below approximately 70°C, while above this temperature, an increase in sliding speed led to an increase in the friction coefficient. The presence of a coating played an important role. It was found that the graphite/resin coating wore quickly, preventing the formation of a beneficial tribochemical film, while the a-C : H coating exhibited a low friction coefficient and provided significant improvement over the uncoated samples. The effect of additives in the oils was also studied. The tribological behaviour of the interface was explained based on viscosity effects and subsequent changes in the lubrication regime, formation of chemical and tribochemical films. Copyright © 2010 John Wiley & Sons, Ltd.

22 citations


Journal ArticleDOI
TL;DR: In this paper, the authors evaluated the relationship between the length of the carbon chain in the fatty acid and its effectiveness as an additive for a range of elevated temperatures, and found that the overall carbon chain length was not a consistent influence on the effectiveness of the additive.
Abstract: Vegetable oils are potential substitutes for petroleum-based lubricants because they are environmentally friendly, renewable, less toxic and readily biodegradable. The addition of free fatty acids has been shown to increase the lubrication performance of vegetable oils at elevated temperatures. The purpose of this study was to evaluate the relationship between the length of the carbon chain in the fatty acid and its effectiveness as an additive for a range of elevated temperatures. Stearic, arachidic and behenic fatty acid additives were added to commercial sunflower oil. All fatty acid additives were shown to be effective in lowering the wear rate and coefficient of friction in ball-on-disc tribological tests. The overall carbon chain length was not observed to have a consistent influence on the effectiveness of the additive. All additives were less effective at temperatures above 100°C. Copyright © 2010 John Wiley & Sons, Ltd.

19 citations


Journal ArticleDOI
TL;DR: In this article, the synthesis, characterization, and evaluation of synthetic esters were discussed and compared with VG-22 grade fire resistant hydraulic fluids (FRHF), and the potential use as FRHF was discussed.
Abstract: Hydraulic fluids based on mineral oils, though have an optimum performance and technical requirements as specified in the standards for hydraulic oils, fail to meet toxicity and biodegradability requirements. Synthetic esters are known to have better biodegradability, lower inflammability, better lubricity and fluidity, lower volatility and higher thermal and oxidation stability in comparison to mineral oils. These properties can be further enhanced through molecular design to suit the practical applications. Therefore, synthetic esters appear as promising candidates where environmental protection is of utmost importance. Polyol and carboxylic acids (C6-C14)both pwre and their mixtures, were used for synthesizing esters. The products were characterized for their physico-chemical properties and evaluated for their lubrication performance. These were then compared with VG-22 grade fire resistant hydraulic fluids (FRHF). The paper deals with the synthesis, characterization, and evaluation of the esters and discusses their potential use as FRHF.

18 citations


Journal ArticleDOI
TL;DR: In this article, the molecular interaction of oleic acid in different base oils at Elastohydrodynamic lubrication (EHL) contact was investigated by means of in-situ observation with micro-Fourier Transform Infrared Spectrometer (FTIR).
Abstract: The molecular interaction of oleic acid in different base oils at Elastohydrodynamic lubrication (EHL) contact was investigated by means of in-situ observation with micro-Fourier Transform Infrared Spectrometer (FTIR). Moreover, the effect of hydrostatic pressure was confirmed using a diamond-anvil cell (DAC). Poly-α-olefin (PAO) with non-polar, and Polypropylene glycol and Polybutylene glycol (PPG and PBG) which have ether group were used as base oil. When PAO was used, oleic acid interacts with itself to form a dimer. On the other hand, oleic acid interacts with PPG and PBG and exists mainly as a monomeric moelcule. The IR peak of C = O stretching mode of oleic acid dimmer was shifted to lower wavenumber at EHL contact region. The peak shift was not obvious in the case of the monomer. This result means that the hydrogen bonding of the dimer was stabilized under high pressure, but the hydrogen bonding of monomer was not. Copyright © 2010 John Wiley & Sons, Ltd.

16 citations


Journal ArticleDOI
TL;DR: In this paper, a comprehensive study has been conducted earlier in the authors' laboratory and various options of non-edible vegetable oil sources were explored, and a few potential vegetable oils were studied in the laboratory.
Abstract: For environmental reasons, as well as the dwindling source of petroleum, a new class of environmentally acceptable and renewable lubricants based on vegetable oils is available. Even though vegetable oils possess excellent lubricant-related properties, there are some concerns about using it as lubricant base oil. Still, unmodified and modified varieties of soybean, rapeseed, sunflower and canola oils have been in use in the USA and Europe. In India, with the shortage of edible oil, alternate sources of vegetable oils stocks are being explored. With this aim, a comprehensive study has been conducted earlier in the authors' laboratory. In this study, numerous options of non-edible vegetable oil sources were explored, and a few potential vegetable oils were studied in the laboratory. It was found that even though the oils performed much better in comparison with other vegetable oils, it still required improvement in thermooxidative stability. Therefore, in the later part of the study, different options were explored to improve thermooxidative stability. With a background on the initial studies of the authors as described above, the present paper deals with the studies on improvement of these non-edible candidate vegetable oils of Indian origin for lubricant by treating with selected antioxidants for applying them in lubricants. Copyright © 2010 John Wiley & Sons, Ltd.

15 citations


Journal ArticleDOI
TL;DR: In this article, a partially textured flat pin sliding on a rotating disc in the presence of a thin lubricating film of constant thickness was used to evaluate the collective hydrodynamic effect of partially textural surfaces.
Abstract: Despite a large amount of work dedicated to the study of the effects of textured surfaces in tribological pairs, there is still a need for accurate and convincing experimental results to prove the benefic effects predicted theoretically. This paper presents an original experimental set-up with a partially textured flat pin sliding on a rotating disc in the presence of a thin lubricating film of constant thickness. The texture was composed of a series of parallel grooves cut on the half of the pin front face. The main objective of the reported work was the experimental assessment of hydrodynamic performances (load capacity and friction force) for parallel, partially textured sliders and the comparison with a similar step slider. Preliminary results have clearly put in evidence the collective hydrodynamic effect of partially textured surfaces. The stepped configuration has shown greater load capacity with respect to textured configuration. Copyright © 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, a full numerical solution to the non-Newtonian transient thermal elastohydrodynamic lubrication (EHL) of gear is obtained by utilising the multi-grid method, which has strong numerical stability, a quick convergence rate and a high degree of accuracy.
Abstract: The lubrication design of gear is based on the assumption that the lubricant is an ideal Newtonian fluid. In fact, The Ree–Eyring fluid model is more in agreement with the lubricant rheological behaviour under medium or mild duty load. It is necessary for engineering lubrication design to study the non-Newtonian transient thermal elastohydrodynamic lubrication (EHL) of gear. In the paper, a full numerical solution to the non-Newtonian transient thermal EHL of gear is obtained by utilising the multi-grid method, which has strong numerical stability, a quick convergence rate and a high degree of accuracy. Copyright © 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, a new range of high-speed steel (HSS)-based self-lubrication composites, with an interpenetrating network, were fabricated by infiltrating Pb-Sn-Ag ternary solid lubricants into TiC-reinforced HSS pre-forms.
Abstract: A new range of high-speed steel (HSS)-based self-lubrication composites, with an interpenetrating network, were fabricated by infiltrating Pb-Sn-Ag ternary solid lubricants into TiC-reinforced HSS pre-forms. The microstructure and mechanical properties were investigated before and after infiltration. The tribological behaviour of the composites was investigated using a pin-on-disk, high temperature wear testing machine at different temperature (up to 800°C). Analysis indicated that Pb-Sn-Ag solid lubricants were well dispersed and embedded in the TiC-HSS matrix where both solid lubricant phase and matrix phase interpenetrating throughout the microstructure. The friction coefficient and specific wear rate of the composites decreased with the increase of the volume fraction of Pb-Sn-Ag solid lubricants up to 15 vol%. With further increases in Pb-Sn-Ag volume fraction, the friction coefficient decreased slightly while the wear rate increased rapidly. The reason is that a large degradation of mechanical properties occurred in samples with high Pb-Sn-Ag contents. Copyright © 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, a numerical investigation of the hydrodynamic lubrication of a porous squeeze film between two circular discs is presented. And the results show that the effect of the porous disc is to reduce the lubricating properties of the fluid film and this effect is increased during the squeezing action.
Abstract: The present paper deals with a numerical investigation of the hydrodynamic lubrication of a porous squeeze film between two circular discs. To this purpose, the thin film (reduced) Navier Stokes equations and a generalised porous medium model are solved. The numerical results show that the effect of the porous disc is to reduce the lubricating properties of the fluid film. This effect is increased during the squeezing action. In addition, it is shown that the film pressure, the load-carrying capacity and the velocity field based only on the Darcy model are predicted higher than those obtained from the generalised porous medium model. Copyright © 2009 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, a miniature mechanical seal with cooling water circulating system has been developed as a shaft seal for rotary blood pumps, and the estimation of the effect of the surface roughness on the shaft seal problems, especially in the increase of the friction and the leakage.
Abstract: A miniature mechanical seal with cooling water circulating system has been developed as a shaft seal for rotary blood pumps. The present paper describes the establishment of the experimental methods under blood sealing and the estimation of the effect of the surface roughness on the shaft seal problems, especially in the increase of the friction and the leakage. Micro-leakage rates of the blood and the cooling water were measured by an ion chromatography. In this method, the ion concentration was converted into the leakage rate. The frictional loss torque was measured by a torque meter. Results are provided with three types of surface roughness, Ra = 0.009 µm, Ra = 0.088 µm and Ra = 0.170 µm. It is shown that as the surface roughness increases the leakage decreases while the frictional loss torque increases under blood sealing. The best surface roughness in the torque and the leakage characteristics were different. Copyright © 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, a selection of additives and their performance and compatibility with a variety of copper alloys have been evaluated in an SRV test set-up, and the tests show a remarkable variation of tribological behaviour with a clear relation to both the type of lubricant / additive and the types of alloy.
Abstract: A selection of additives and their performance and compatibility with a variety of copper alloys have been evaluated in an SRV test set-up. The tests show a remarkable variation of tribological behaviour with a clear relation to both the type of lubricant / additive and the type of alloy. One ester-based additive showed outstanding friction and wear reduction for some groups of copper alloys. In order to better understand the fundamental mechanisms, we applied a variety of surface analyses, such as 3D confocal white light microscopy, scanning electron microscopy and X-ray photoelectron microscopy. Copyright © 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, the synthesis of new pyrimidine derivatives was studied using N-methylation using methyl iodide and phenyl hydrazine and thiosemicarbazide.
Abstract: Pyrimidine-5-carboxylate derivative Ia was utilised as a key intermediate for the synthesis of new pyrimidine derivatives. Thiopyrimidine derivative Ia undergo N-methylation using methyl iodide afforded III. Methylsulfanyl moiety in II was easily removed when reacted with phenyl hydrazine and thiosemicarbazide afforded pyrimidine derivatives IV and VI, respectively. The reaction on nitrogen atom in Ia using 1,3-dibromo-propane, benzoyl chloride, phosphorous oxychloride afforded VIII, IX and X, respectively. The reaction using 1,3-dibromo-propane or 1,2-dibromo-ethane furnished the formation of the corresponding fused cycles containing sulfur. Representative compounds of the synthesised products were evaluated as antioxidant and corrosion inhibitors for gasoline lube oils. Copyright © 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, three different lubricants were used viz. base oil with detergents (Oil-A), oil with ZnP-based additives (OIL-B) and oil with P-based additive (O-C), and the experiments were carried out on a ring-on-disc test setup on Fe/Fe- and Fe/Cu-based systems.
Abstract: The layer-forming properties of different lubricants on technically used tribosystems were investigated. The experiments were carried out on a ring-on-disc test set-up on Fe/Fe- and Fe/Cu-based systems. Three different lubricants were used viz. base oil with detergents (Oil-A), oil with ZnP-based additives (Oil-B) and oil with P-based additives (Oil-C). We measured the electrical resistance between the rubbing surfaces. Surface characterisation (light microscopy, SEM/EDX and XPS) and tribometric results show differences in wear and friction properties. Oil-B showed profound layer formation on steel counterparts and correlation in the amount of Zn and S, P and O, respectively; whereas, none of the above was observed with Oil-A. Oil-C, however, showed thin but tribologically effective layer formation on ferrous system and a superior performance for the Fe/Cu system. Copyright © 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, the stabilisation of hydrogen bonding of polypropylene glycol at elastohydrodynamic lubrication (EHL) contact was investigated by in situ observation with a micro-Fourier transform infrared spectrometer, and the effect of hydrostatic pressure on infrared (IR) spectra was confirmed using a diamond anvil cell.
Abstract: In the present work, the stabilisation of hydrogen bonding of polypropylene glycol at elastohydrodynamic lubrication (EHL) contact was investigated by in situ observation with a micro-Fourier transform infrared spectrometer, and the effect of hydrostatic pressure on infrared (IR) spectra was confirmed using a diamond anvil cell. Polypropylene glycols with different molecular weights were used as sample oils. Polypropylene glycol molecules interact with themselves by hydrogen bonding with their hydroxyl groups. Stability of the hydrogen bonding is observed by IR peak shift of the O–H stretching mode (3400–3700 cm−1). In the case of the dynamic condition under EHL, the C–H stretching mode shifted to a higher wavenumber, whereas the O–H stretching mode shifted to a lower wavenumber at the Hertzian contact region. This result means that the hydrogen bonding of polypropylene glycol was stabilised under high pressure, and the stabilisation of hydrogen bonding by pressure was dependent on the molecular weight of polypropylene glycol. Copyright © 2010 John Wiley & Sons, Ltd.


Journal ArticleDOI
TL;DR: In this article, a linear perfluoropolyalkylethers (PFPEs) with regularly sequenced repeat units are prepared by a four-step synthesis starting from simple glycols and tetrafluoroethylene.
Abstract: New linear perfluoropolyalkylethers (PFPEs) with regularly sequenced repeat units are prepared by a four-step synthesis starting from simple glycols and tetrafluoroethylene. The synthesis includes: (i) the reaction of glycols with tetrafluoroethylene to give bis(tetrafluoroethyl)alkyl ethers, (ii) the dehydrofluorination of the adduct with butyllithium to obtain bis(trifluorovinyl)alkyl ethers, (iii) the polymerisation of the trifluorovinyl ethers with glycols in the presence of base to make polyfluoroalkyl polyethers, and (iv) finally the fluorination of the polymers to provide PFPEs. The repeat units of the final PFPEs are altered by the variation of diols used in steps 1 and 3. Copyright © 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: An organic compound containing N, B and O was synthesized by reacting 3-hydroxymethyl-quinazolin-4-ones and formalin in 1, 4-dioxane solution, the resulting product then being reacted with butanol and boric acid in dimethylbenzene solution.
Abstract: An organic compound containing N, B and O was synthesised by reacting 3-hydroxymethyl-quinazolin-4-ones and formalin in 1, 4-dioxane solution, the resulting product then being reacted with butanol and boric acid in dimethylbenzene solution. The tribological performance of the novel compound when added to liquid paraffin was evaluated using a four-ball tester and a ring-on-block machine. The relationship between performance and concentration was analysed, and the results showed that the compound possesses good anti-wear, friction-reducing and load-carrying properties. The mechanism of action of the additive was investigated using X-ray photoelectron spectroscopy. Surface analysis indicated the formation of a protective film containing borate, Fe(3)O(4), and an organonitrogen compound. This protective film formed during sliding processes contributes to the increase in wear resistance. Copyright (C) 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, the rheological properties of solidified lubricant oils under pressure were evaluated by observing large plastic deformation of metal microspheres, occurring due to non-hydrostatic pressurisation in the oils when using a diamond-anvil cell pressure-generating apparatus.
Abstract: The rheological properties of solidified lubricant oils under pressure were evaluated by observing large plastic deformation of metal microspheres, occurring due to non-hydrostatic pressurisation in the oils when using a diamond-anvil cell pressure-generating apparatus. Defining the solidification pressure as the onset pressure of plastic deformation of aluminum sphere obtained solidification pressures for traction oils were about 0.5 GPa, whereas those for mineral and synthetic oils ranged from 1.2 to 2 GPa. By substituting the solidification pressures and pressure–viscosity coefficients in the Barus equation, viscosities at the solidification pressure were obtained. The values were different for each oil and were within the order of 106–108 Pas. Based on several assumptions, shear stresses of the solidified oils could be estimated up to 5 GPa from the deformed Cu spheres. The shear stresses for a traction oil were almost equal to the mean shear stress obtained from a traction test between 1.0 and 1.7 GPa. Copyright © 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, a hydrodynamic bearing with non-uniform herringbone grooves was developed for use with high-speed motor spindles, which gradually become narrower, shallower and less straight (curved) towards the herring-bone center along axial direction, resulting in an increased pumping effect of the spiral grooves.
Abstract: A hydrodynamic bearing with non-uniform herringbone grooves has been developed for use with high-speed motor spindles. The grooves gradually become narrower, shallower and less straight (curved) towards the herringbone centre along axial direction, resulting in an increased pumping effect of the spiral grooves. The optimum dimensions of the grooves for increasing the critical bearing number were clarified theoretically, and bearings with non-uniform herringbone grooves were found to increase the critical bearing number against the half-frequency whirl up to about 50% in comparison to bearings with uniform herringbone grooves. Experiments to investigate the suitability of the proposed bearing for high-speed spindles showed that the maximum rotational speed of a spindle with this bearing was about 20% higher, close to the theoretically predicted 23%, and thus proved that application of this bearing should enable spindles to achieve faster stable rotation as theoretically expected. Copyright © 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, it was found that transient film profiles depend on the non-Newtonian response of the oils and the type of motion, and that the running-in period has a crucial importance for the tribofilm formation, and is directly connected with the total energy dissipated from the contact region.
Abstract: The problem of a proper lubrication under low-speed small oscillatory movement can be a decisive factor for the reliability of various components. There is a need to characterise the lubricious behaviour of the interface under oil-bath fretting wear conditions for ball bearing applications. Fast and reliable methods to quantify this behaviour for broad range of mechanical conditions are proposed and validated. Pure sliding reciprocation induces mixed lubrication mode. It was found that transient film profiles depend on the non-Newtonian response of the oils and the type of motion. Running-in period has a crucial importance for the tribofilm formation, and is a result of the interplay of the oil-sliding surfaces interface and is directly connected with the total energy dissipated from the contact region. The stability of structured tribofilm in steady-state period relies on the balance between the competitive processes: replenishment of the oil to the contact and ejection of the oil pending the oscillatory movement. The phenomenon of starvation was observed when the system was moved away from dynamical equilibrium and the growth of the dissipated energy was spotted. A proposed methodology provides the evaluation of the lubrication properties of the oil in a quantitative way. Copyright © 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: Amorphous carbon nitride (a-CNx) coatings were deposited on SiC disks by using ion beam assisted deposition, and their bonding structure and hardness were determined using X-ray photoelectron spectroscopy and nano-indenter, respectively as discussed by the authors.
Abstract: Amorphous carbon nitride(a-CNx) coatings were deposited on SiC disks by using ion beam assisted deposition, and their bonding structure and hardness were determined using X-ray photoelectron spectroscopy and nano-indenter, respectively. The contact angles on the surface of the a-CNx coatings were measured with contact angle meter. The friction and wear behaviours of the a-CNx/SiC tribopairs in ethylene glycol aqueous solution were investigated with ball-on-disk tribometer. The results indicated that the a-CNx coatings contained 12at. % nitrogen and their bonding structure consisted of sp2C=N/C=C and sp3C–N bonds. The static contact angles on the a-CNx coatings decreased with the ethylene glycol concentration. The lowest coefficient of friction of 0.019 was acquired as the ethylene glycol concentration was 10vol. %. When the ethylene glycol concentration increased, the specific wear rate of the SiC ball fluctuated in the range of 5.9 × 10?10?1.1 × 10?9?mm3?Nm?1, while that of a-CNx coatings varied in the range of 3.3 × 10?8?7.8 × 10?8?mm3?Nm?1.

Journal ArticleDOI
TL;DR: In this article, a tribometer that undergoes significant changes at ultra-slow (>5.0 µm) to moderate (<20 µm−1) sliding speeds was developed in order to study the friction-speed characteristics of steel lubricated with oil.
Abstract: A novel tribometer that undergoes significant changes at ultra-slow (>5.0 µm s−1) to moderate (<20 cm s−1) sliding speeds was developed in order to study the friction-speed characteristics of steel lubricated with oil. Three different surface topographies were applied to the specimens, and the friction characteristics with an additive-free base oil (MO91) and a stearic acid-formulated oil (StA/MO91) were studied to understand the effects of surface textures on the lubrication performance of an adsorbed molecular layer formed by StA. Friction reduction behaviour of the adsorbed layer observed in the transverse direction was attributed to microscopic hydrodynamic action that maintained the load-carrying performance of the adsorbed layer. Copyright © 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, a stable numerical approach is developed for solution of problems for heavily loaded line EHL problems and the asymptotic equations of the problem in the inlet and exit contact zones.
Abstract: A stable numerical approach is developed for solution of problems for heavily loaded line EHL problems and the asymptotic equations of the problem in the inlet and exit contact zones. The numerical approach is based on two ideas: (i) It uses the form of the original and asymptotic EHL equations resolved for pressure involved in the equations for the gap between the lubricated solids; and (ii) It uses regularisation based on an asymptotic solution of the non-isothermal EHL problem. That allows for a stable solution of the EHL problem even for extremely high dimensionless pressure viscosity coefficients ranging from 0 to 40. Therefore, the paper consists of three parts: (i) Part 1 is devoted to development of an asymptotic approach to solution of heavily loaded EHL contacts and to numerical solution of these equations. This part is very essential as it paves the way to the asymptotic analysis of non-isothermal EHL problem and, consequently, to construction of a stable regularised numerical algorithm; (ii) Part 2 is devoted to asymptotic and numerical analysis of non-isothermal EHL problem for heavily loaded contacts; and (iii) Part 3 is devoted to development of regularised stable numerical solutions of the asymptotic and original equations for heavily loaded EHL contacts. Copyright © 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, a general analysis has been done to investigate the static and dynamic performance of short wavy journal bearing for both steady-and unsteady-state operations, and it has been shown that wave bearing has not only better load carrying capacity but also provides better stability at high speed than circular bearing.
Abstract: A general analysis has been done to investigate the static and dynamic performance of short wavy journal bearing. Reynolds equation is solved for both steady- and unsteady-state operations. The steady-state analysis has been done and compared with circular bearing with respect to their load capacity, flow rate, pressure distribution and friction factor. The unsteady-state analysis has been used to determine the rotor dynamic coefficients for various eccentricity ratios. These coefficients are used to determine the stability parameters, such as critical mass and whirl ratio, and prove that wave bearing has not only better load carrying capacity but also provides better stability at high speed than circular bearing. Copyright © 2010 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a quantitative calculation of slider bearings using the analytical solutions of energy equation and of the Reynolds differential equation, and the model consists in the transformation of the slider bearing pad into a journal bearing bush and the validation consists in comparing the pad's hydrodynamic parameters with those of the proposed journal bearing, calculated analytically.
Abstract: The present paper proposed a quantitative calculation of slider bearings using the analytical solutions of energy equation and of the Reynolds differential equation. The model consists in the transformation of the slider bearing pad into a journal bearing bush. The validation consists in comparing the pad's hydrodynamic parameters, calculated by means of numerical methods, with those of the proposed journal bearing, calculated analytically. The simplicity and accuracy of the method and the computing times of the order of seconds necessary for bearing estimation constitute important advantages of this model over the numerical methods. Copyright © 2010 John Wiley & Sons, Ltd.