Journal articles: 'Elastohydrodynamical lubrication'

1

Guo, F., and P. L. Wong. "An Anomalous Elastohydrodynamic Lubrication Film: Inlet Dimple." Journal of Tribology 127, no. 2 (April 1, 2005): 425–34. http://dx.doi.org/10.1115/1.1866165.

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This paper presents a deliberately designed elastohydrodynamical lubrication (EHL) experiment for the study of the individual effect of the limiting shear stress and wall slippage. Very slow entrainment speeds were employed to avoid influential shear heating and oils of high viscosities were chosen to ensure that the conjunction was under typical EHL. An anomalous EHL film, characterized by a dimple at the inlet region, was obtained. Literature revealed that this inlet dimple was reported in some numerical studies taking into consideration the limiting-shear-stress characteristics of the lubricant and wall slippage. It was found that even under the same kinematic conditions, different types of film shape would be generated by simple disc sliding and simple ball sliding. Simple disc sliding produces an inlet dimple with a comparatively thick inlet film thickness, which droops rapidly toward the outlet region. For simple ball sliding, there is also an inlet dimple but the central film thickness is rather uniform. However, by prerunning the conjunction at a zero entrainment velocity (at the same linear speeds but in opposite directions) before the sliding experiment, the slope of the central film of simple disc sliding becomes smaller. It is probably due to the modification of solid-liquid interface, i.e., the slippage level, by the highly pressurized and stressed prerunning conditions. With a prescribed prerunning, which can produce very similar films at simple disc sliding and simple ball sliding, variation of film thickness was studied and it was found that the inlet dimple film has obvious dependence on entrainment speeds, but was not sensitive to loads. The present experimental results can be considered as direct evidence for those numerical findings of the inlet dimple. Tentatively, an effective viscosity wedge is proposed to account for the formation of the inlet dimple.

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Auger, D. D., D. Dowson, J. Fisher, and Z.-M. Jin. "Friction and Lubrication in Cushion Form Bearings for Artificial Hip Joints." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 207, no. 1 (March 1993): 25–33. http://dx.doi.org/10.1243/pime_proc_1993_207_265_02.

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Two hip joint prostheses were designed and constructed to be elastohydrodynamically equivalent producing approximately equal initial contact areas and theoretical film thicknesses. One was made from conventional UHMWPE (ultra-high molecular weight polyethylene) and the other was a cushion component which had a low modulus layer introduced into the joint space. Friction measurements were carried out on a pendulum simulator apparatus and the two joints were compared. In addition the experimental results were compared with theoretical values of friction predicted from elastohydrodynamic lubrication theory. Values for the friction factor at peak load and peak velocity in the cushion cup (0.003–0.009) were much lower than in the UHMWPE cup (0.017–0.042). The low friction values in the cushion cup are consistent with fluid film lubrication in the contact with the thin lubricating film being preserved by microelastohydrodynamic action.

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Kim, Seong Su, Juh Wan Choi, Sung Soo Rhim, and Jin Hwan Choi. "Numerical Modeling of Piston Lubrication with Body Deformation through Modal Reduction Method." Key Engineering Materials 739 (June 2017): 193–201. http://dx.doi.org/10.4028/www.scientific.net/kem.739.193.

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An analysis for operating characteristics of piston lubrication system is performed based on the numerical model in this study. Dynamic piston lubrication characteristics such as oil film pressure and thickness distribution can be analyzed through a numerical model with an integration of elastohydrodynamics and multi-flexible-body dynamics (MFBD). In particular, the oil film thickness variation by elastic deformation is considered in the elastohydrodynamic analysis by using the modal reduction method in MFBD system. And this effect is reflected on the fluid governing equations to evaluate the oil film pressure in the lubrication region. A series of process proposed in this study is available for the analysis of realistic elastohydrodynamic lubrication phenomenon. A numerical example for the piston lubrication system is also demonstrated.

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Ji, Fen Zhu, Yu Chen Guo, Fa Rong Du, Shu Chun Yang, and Bin Xu. "Research on the Performance of Space Liquid Lubrication System with Oil-Storage." Advanced Materials Research 479-481 (February 2012): 2393–97. http://dx.doi.org/10.4028/www.scientific.net/amr.479-481.2393.

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The gravity oil feed method dose not suit for microgravity environment as the same way dose for ground lubrication system. It is the key problem to be solved that how to supply the oil to friction surface in space liquid lubrication system. It analyzed the lubricating manner. A space liquid lubrication system was designed based on a principle of using deformation energy to supply oil. In the analysis of its basic structure and operating principle, the film calculation mode was established based on the elastohydrodynamic lubrication theory. The lubricating performance was simulated by ANSYS finite element analysis software in microgravity. The calculation results show that: in the microgravity, it could achieve elastohydrodynamic lubrication on friction surface in this lubrication system. When the oil supply hole diameter is 2mm, the film-thickness ratio changes between 1.91 and 4.28. It belongs to elastohydrodynamic lubrication. The hole diameter decreases, the film thickness reduces. The minimum film-thickness ratio is 0.93 when the temperature changes widely from -50°C~+80°C. It belongs to boundary lubrication state.

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Choi, Juh Wan, Seong Su Kim, Sung Soo Rhim, and Jin Hwan Choi. "Numerical Model of Journal Bearing Lubrication Considering a Bending Stiffness Effect." Applied Mechanics and Materials 284-287 (January 2013): 854–60. http://dx.doi.org/10.4028/www.scientific.net/amm.284-287.854.

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An analysis for operating characteristics of journal bearing lubrication system is performed based on the numerical model. Dynamic bearing lubrication characteristics such as oil film pressure and thickness distribution can be analyzed through a numerical model with an integration of elastohydrodynamics and multi-flexible-body dynamics (MFBD). In particular, the oil film thickness variation by elastic deformation is considered in the elastohydrodynamic analysis by applying the bending stiffness effect of journal. And the oil film thickness variation by the bending stiffness effect is applied to the fluid governing equations to calculate the oil film pressure in the elastohydrodynamic lubrication region. A series of process proposed in this study is available for the analysis of realistic elastohydrodynamic lubrication phenomenon. Also, a numerical example for the journal bearing lubrication system is demonstrated and compared with the experimental results. The numerical results considering the bending stiffness effect show a good agreement with the experimental results.

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Yang, Fuqin, Dexing Hu, Qianhao Xiao, and Shun Zhao. "Experimental study on line-contact elastohydrodynamic grease lubrication properties of surface-textured rollers." Industrial Lubrication and Tribology 73, no. 3 (January 25, 2021): 477–84. http://dx.doi.org/10.1108/ilt-03-2020-0079.

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Purpose This paper aims to study line-contact elastohydrodynamic grease lubrication properties of surface-textured rollers as well as the effect of different crown widths (dw) on oil film thickness under textured conditions. Design/methodology/approach The laser processing method was used to make the micro-texture on the surface of GCr15 steel rollers; lithium grease was used as the lubricant, and line-contact elastohydrodynamic grease lubrication experiments under pure sliding conditions were performed on light interference elastohydrodynamic-lubricated experimental table. Findings The results show that the line-contact elastohydrodynamic grease lubrication is closely related to the textured crown width of steel rollers. At low speeds and light loads, texturing has an inevitable inhibitory effect on the formation of the lubricating oil film, and the smaller the width of the crown area, the more obvious the inhibitory effect, which is not conducive to the improvement of the lubrication condition. At high speeds and high loads, the textured roller with dw = 1 mm has the largest oil film thickness and shows better lubrication performance. Originality/value At present, there is little research on the surface texture of line-contact friction pairs. This work explores the effect of different textured crown width on the lubricating properties of line-contact elastohydrodynamic grease lubrication by experiment. It provides a new theoretical basis for the subsequent practical application of surface texture technology.

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Chang, L. "Traction in Thermal Elastohydrodynamic Lubrication of Rough Surfaces." Journal of Tribology 114, no. 1 (January 1, 1992): 186–91. http://dx.doi.org/10.1115/1.2920859.

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This paper studies the traction behavior of elastohydrodynamically lubricated line contacts between two rough surfaces. The study uses a thermal micro-elastohydrodynamic-lubrication (micro-EHL) model and obtains traction coefficients for a wide range of operating conditions and for film parameters as small as 1.50. The simulation results suggest that the traction is generally insensitive to the roughness structure and magnitude as long as the contact maintains a full EHL film. The results also indicate clearly that the lubricant squeeze induced by the motion and interaction of rough surfaces significantly affects the numerical solutions to thermal micro-elastohydrodynamic lubrication.

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Wang, S., Y.-Z. Hu, and Q.-C. Tan. "Frictional behaviour of engineering surfaces in overall lubrication regimes of point contacts." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 225, no. 11 (September 23, 2011): 1071–80. http://dx.doi.org/10.1177/1350650111414333.

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The aim of the present paper is to study experimentally and numerically the frictional behaviour of engineering surfaces within all lubrication regions of point contacts. For this reason, a numerical solution proposed elsewhere by the current authors, which can predict friction under the different lubrication modes of elastohydrodynamic, mixed, and boundary lubrications, is introduced. Based on a deterministic model of mixed lubrication, the solution was combined with the variation of the lubricating films’ physical state during the transition of lubrication modes. Results show that roughness amplitude has a great effect on the transition of friction regimes. In addition, it is also observed that variation of the friction coefficient has nearly the same trend as the true contact area ratio in the mixed lubrication state. Meanwhile, it is concluded that transverse roughness has better film-forming capacity than longitudinal roughness and thus leads to a lower magnitude of friction coefficient if the operating conditions are the same. Analysis of the mechanism of friction behaviour suggests that the true contact area ratio determines the friction behaviour of engineering surfaces in mixed lubrication. In smooth contacts, the comparison of experiment tests and simulation results suggests that friction variation results from gradual change of the liquid lubricant to solid-like matter with diminishing film thickness.

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Jia, Fuchun, Yulong Lei, Yao Fu, Binyu Wang, and Jianlong Hu. "Demand Analysis of Lubricating Oil in Spur Gear Pairs." Applied Sciences 10, no. 16 (August 5, 2020): 5417. http://dx.doi.org/10.3390/app10165417.

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Theoretical calculation and numerical simulation are used to investigate the lubricating oil demand of spur gears. In accordance with the function of lubricating oil during the meshing process, oil demand is regarded as the superposition of oil for lubrication and cooling. Oil for lubrication is calculated in accordance with meshing and elastohydrodynamic lubrication (EHL) theories. Oil for cooling is obtained from friction heat. The influence of different meshing positions on lubricating oil demand is analysed, and the effects of modulus, tooth number, transmission ratio, input speed and input torque on lubricating oil demand is investigated using a control variate method. Simulation results indicated that oil for lubrication and oil for cooling have two maxima each during a meshing circle. The influences of different gear parameters and working conditions on lubricating oil demand are compared. The results showed that the oil volume for lubrication increases and oil volume for cooling decreases as the modulus, tooth number and transmission ratio of the gear increase, the oil volume for lubrication and oil volume for cooling increases as the input speed and input torque increase.

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10

Miao, Nai Ming. "Research and Development of Overloading Velocity Jump Line Contact Elastohydrodynamic Lubrication Testbed." Applied Mechanics and Materials 713-715 (January 2015): 182–86. http://dx.doi.org/10.4028/www.scientific.net/amm.713-715.182.

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To research the lubricating property of line contact elastohydrodynamic lubrication under the working conditions of overloading velocity jump, based on the optic elastohydrodynamic experimental apparatus developed by the research group, an measuring equipment applicable to the oil film thickness and shape under the condition of overloading velocity jump is designed and developed. This testbed is mainly composed of glass block reciprocating motion system, ball or roller rotary rolling system, loading system, speed regulating system, light source system and image acquisition system. The motion part replaces the slider-crank mechanism with kad-screw mechanism and is driven by stepper motor, so as to realize the different working conditions of velocity jump. The developed platform was adopted to carry out the velocity jump line contact elastohydrodynamic lubrication test by the driving of the stepping motor, investigating the influence of line contact friction pair on the lubricating oil film at the moment of acceleration under the overloading working condition.

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11

Snidle, R. W., H. P. Evans, and M. P. Alanou. "Gears: Elastohydrodynamic lubrication and durability." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 214, no. 1 (January 1, 2000): 39–50. http://dx.doi.org/10.1243/0954406001522796.

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The paper presents a brief review of developments in understanding of gear tooth contact lubrication in relation to problems of surface durability and distress. Gear tooth contacts tend to operate under conditions where the lubricating oil film is thin compared with surface roughness. This feature is shown to have a significant effect on scuffing capacity and friction and is also thought to be a factor in micropitting. Recent developments in thin-film micro-elastohydrodynamic lubrication theory are described and these should lead to a better understanding of the behaviour and modes of surface distress in gears. The paper also describes the application of elastohydrodynamic analysis to other transmission components such as high-conformity gears and thrust cones.

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12

Greenwood, James A. "Elastohydrodynamic Lubrication." Lubricants 8, no. 5 (May 6, 2020): 51. http://dx.doi.org/10.3390/lubricants8050051.

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The development of EHL theory from its tentative beginnings is outlined, with an account of how Ertel explained its relation to Hertz contact theory. The problems caused by the failure of the early numerical analysts to understand that the film thickness depends on only two variables are emphasised, and answers of the form H = F ( P , S ) given. Early methods of measuring the film thickness are described, but these became archaic with the development of optical EHL. The behaviour of surface roughness as it passes through the high pressure region and suffers elastic deformation is described, and the implication for the traditional Λ -ratio noted. In contrast, the understanding of traction is far from satisfactory. The oil in the high pressure region must become non-Newtonian: the early explanation that the viscosity reduction is the effect of temperature proved inadequate. There must be some form of shear thinning (perhaps according to the Eyring theory), but also a limiting shear stress under which the lubricant shears as an elastic solid. It seems that detailed, and difficult, measurements of the high pressure, high shear-rate behaviour of individual oils are needed before traction curves can be predicted.

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Dyson, A., H. P. Evans, G. Karami, M. C. Paliwal, and R. W. Snidle. "Scuffing Failure of Steel Discs: Conditions for the Failure of Elastohydrodynamic Lubrication." Proceedings of the Institution of Mechanical Engineers, Part C: Mechanical Engineering Science 204, no. 2 (March 1990): 91–97. http://dx.doi.org/10.1243/pime_proc_1990_204_082_02.

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Scuffing tests run on circumferentially finished discs were analysed to determine the conditions for the failure of elastohydrodynamic lubrication according to Dyson's theory. The critical lubricant temperatures and viscosities derived from this analysis were compared with the temperatures and viscosities at atmospheric pressure and at the bulk temperature of the discs, as recorded by thermocouples embedded below the surfaces. Tests and corresponding calculations were made for three different lubricating oils and for two steels. The results of the comparison between measured and calculated critical temperatures and viscosities support the concept of scuffing failure as being related to the physical failure of elastohydrodynamic lubrication, even though the lubricants differed significantly in their scuffing behaviour.

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Lubrecht, A. A., W. E. Ten Napel, and R. Bosma. "The Influence of Longitudinal and Transverse Roughness on the Elastohydrodynamic Lubrication of Circular Contacts." Journal of Tribology 110, no. 3 (July 1, 1988): 421–26. http://dx.doi.org/10.1115/1.3261645.

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The effect of longitudinal and transverse roughness on the elastohydrodynamic lubrication of circular contacts was investigated numerically for two different lubricating conditions. The influence of the amplitude and the wavelength of the roughness texture was also studied. The results are compared with predictions from the flow factor method.

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Dowson, D. "Elastohydrodynamic and micro-elastohydrodynamic lubrication." Wear 190, no. 2 (December 1995): 125–38. http://dx.doi.org/10.1016/0043-1648(95)06660-8.

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Olver, A. V. "Gear lubrication—a review." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 216, no. 5 (May 1, 2002): 255–67. http://dx.doi.org/10.1243/135065002760364804.

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The lubrication of gear teeth is reviewed including some key aspects of recent theoretical research and current practice. A simple estimate of the thickness of the lubricating film in a typical pair of spur gears is presented on the basis of classical smooth-body isothermal, elastohydrodynamic lubrication theory. The deficiencies of this simple calculation are then discussed; these include roughness, friction, churning, starvation and contamination, all common features of practical gearing. Three simple methods are described for estimating the tooth temperature and its consequent effect on film thickness.

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Zhou, Ye, Degong Chang, and Songmei Li. "Analysis on grease lubrication properties of the tripod sliding universal coupling in automotive transmission shaft." Industrial Lubrication and Tribology 69, no. 4 (July 10, 2017): 598–604. http://dx.doi.org/10.1108/ilt-08-2016-0185.

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Purpose This paper aims to investigate the grease isothermal lubrication properties of the tripod sliding universal coupling (TSUC) in automotive transmission shaft and study its impact on a variety of factors to improve its grease lubrication properties. Design/methodology/approach Based on the simplified geometrical model, the research of grease lubrication properties of the TSUC was analyzed, and compared with oil lubrication in same parameters. Then the effects of effective radius, frequency (vehicle speed) and amplitude (angle between intermediate shaft and input shaft) on grease isothermal lubrication properties are theoretically investigated by using multigrid methods. Findings The results indicate that the grease isothermal elastohydrodynamic lubrication (EHL) film thickness shape and pressure distribution shape of the TSUC are similar to the oil lubrication, but the film thickness of grease lubrication is less than that of oil lubrication. Higher effective radius results in a wider pressure distribution, a lower center pressure and a thicker lubricating film. Higher frequency (vehicle speed) results in a remarkable second pressure peak and a thicker lubricating film. The effects of amplitude (angle between intermediate shaft and input shaft) and frequency have similar tendencies. Originality/value The numerical analysis research on grease lubrication properties of the TSUC is significant because the automotive transmission shaft is widely used. And it provides a new direction in designing TSUCs.

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Chu, Li Ming, and Hsiang Chen Hsu. "A Layered-Rheology Model for Thin Film Elastohydrodynamic Lubrication of Circular Contacts." Applied Mechanics and Materials 764-765 (May 2015): 160–64. http://dx.doi.org/10.4028/www.scientific.net/amm.764-765.160.

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The modified Reynolds equation for power-law fluid is derived from the viscous adsorption theory for thin film elastohydrodynamic lubrication (TFEHL) of circular contacts. The lubricating film between solid surfaces is modeled as three fixed layers, which are two adsorption layers on each surface and a middle layer. The differences between classical EHL and TFEHL with non-Newtonian lubricants are discussed. Results show that the TFEHL power law model can reasonably calculate the pressure distribution, the film thickness, and the velocity distribution. The thickness and viscosity of the adsorption layer and the flow index influence significantly the lubrication characteristics of the contact conjunction.

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Kingsbury, E. "Parched Elastohydrodynamic Lubrication." Journal of Tribology 107, no. 2 (April 1, 1985): 229–32. http://dx.doi.org/10.1115/1.3261026.

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A parched subregime of elastohydrodynamic lubrication is proposed, lying between starved and mixed. Parched EHL is necessary to describe instrument ball bearing behavior, for example: long term transients in film thickness. A parched bearing has the least driving torque demand and best spin axis definition possible from any lubrication regime. Some measurements made in a 40 mm bore bearing show that parched operation is not limited to small bearings.

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Yang, Peiran, Jinlei Cui, Motohiro Kaneta, and Hiroshi Nishikawa. "Influence of a Surface Bump or Groove on the Lubricating Performance and Dimple Phenomena in Simple Sliding Point EHL Contacts." Journal of Tribology 126, no. 3 (June 28, 2004): 466–72. http://dx.doi.org/10.1115/1.1691434.

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The influence of a transversely or longitudinally oriented surface bump or groove on the lubricating performance and dimple phenomena in the simple sliding point contact composed of a steel ball and a glass disk has been investigated theoretically with numerical solution of the thermal elastohydrodynamic lubrication (EHL) and experimentally with optical interferometry technique. Good agreement has been obtained between the theoretical and experimental results. It has also been discovered that the surface bump or groove is dangerously harmful to the lubricating performance and has a significant influence on the dimple phenomena.

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Chu, Li-Ming, Hsiang-Chen Hsu, and Chia-Hsiang Su. "POWER LAW FLUID MODEL INCORPORATED INTO THIN FILM ELASTOHYDRODYNAMIC LUBRICATION OF CIRCULAR CONTACTS." Transactions of the Canadian Society for Mechanical Engineering 39, no. 3 (September 2015): 547–56. http://dx.doi.org/10.1139/tcsme-2015-0042.

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The modified Reynolds equation for power-law fluid is derived from the viscous adsorption theory for thin film elastohydrodynamic lubrication (TFEHL) of circular contacts. The lubricating film between solid surfaces is modeled as three fixed layers, which are two adsorption layers on each surface and a middle layer. The differences between classical EHL and TFEHL with power-law lubricants are discussed. Results show that the TFEHL power law model can reasonably calculate the pressure distribution, the film thickness, and the velocity distribution. The thickness and viscosity of the adsorption layer and the flow index significantly influence the lubrication characteristics of the contact conjunction.

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Zhou, Ye, Degong Chang, and Songmei Li. "Grease thermal elastohydrodynamic lubrication properties of tripod sliding universal couplings." Industrial Lubrication and Tribology 70, no. 1 (January 8, 2018): 133–39. http://dx.doi.org/10.1108/ilt-11-2016-0277.

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Purpose This paper aims to improve the grease thermal elastohydrodynamic lubrication (TEHL) properties of the tripod sliding universal coupling (TSUC) under automotive practical conditions. For this purpose, the effect of effective radius was theoretically investigated. Design/methodology/approach Based on the simplified geometric model, the effect of effective radius on the pressure distribution, film thickness and temperature distribution of the TSUC was theoretically investigated using the multigrid and stepping methods. The TEHL properties were compared with the results obtained using the isothermal calculation method. Findings The results show that the thermal effect has a great impact on the film thickness and the pressure distribution of grease lubrication properties. Moreover, larger effective radius results in a wider but lower pressure distribution, a wider and thicker lubricating film and a lower temperature distribution. Originality/value The TSUC can be widely used in the front drive automotive transmission because it can transmit larger torque than before. The effect of effective radius on the thermal grease lubrication properties under automotive practical conditions provides a new direction for designing it.

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Ratoi-Salagean, M., H. Spikes, and R. Hoogendoorn. "The design of lubricious oil-in-water emulsions." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 211, no. 3 (March 1, 1997): 195–208. http://dx.doi.org/10.1243/1350650971542426.

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Oil-in-water emulsions, as used in metal working and fire-resistant hydraulic fluids, often show poor lubricating performance and one reason for this is their inability to form effective elastohydrodynamic films. This paper considers how the composition of an oil-in-water emulsion contributes to its lubricating properties. A key factor in oil-in-water emulsion performance lies in the ability of the dispersed oil droplets to wet polar metal surfaces and thus promote full elastohydrodynamic lubrication, without starvation, up to high speeds. In this paper it is shown how this ability can be quantified in terms of measurable surface chemical parameters. Based on this work, three rules for designing lubricious oil-in-water emulsions are proposed. Where possible (a) the emulsifier concentration used should be just below its critical micelle concentration value, (b) the base oil should be polar and (c) the base oil should be viscous. The first two of these factors will promote oil-phase surface wetting while the third will ensure thick-film formation in the full elastohydrodynamic regime.

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Masjedi, M., and MM Khonsari. "Mixed lubrication of soft contacts: An engineering look." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 231, no. 2 (August 5, 2016): 263–73. http://dx.doi.org/10.1177/1350650116652286.

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Mixed elastohydrodynamic lubrication of materials with low elastic modulus (soft materials) is investigated. Expressions for prediction of film thickness and the asperity load ratio in soft line-contact elastohydrodynamic lubrication are presented. The traction behavior of soft contact in mixed elastohydrodynamic lubrication regime is also studied in terms of the Stribeck curves.

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Zhang, Chaohui, Jianbin Luo, and Shizhu Wen. "A New Postulation of Viscosity and Its Application in Computation of Film Thickness in TFL1." Journal of Tribology 124, no. 4 (September 24, 2002): 811–14. http://dx.doi.org/10.1115/1.1456090.

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In this paper, a viscosity modification model is developed which can be applied to describe the thin film lubrication problems. The viscosity distribution along the direction normal to solid surface is approached by a function proposed in this paper. Based on the formula, lubricating problem of thin film lubrication (TFL) in isothermal and incompressible condition is solved and the outcome is compared to the experimental data. In thin film lubrication, according to the computation outcomes, the lubrication film thickness is much greater than that in elastohydrodynamic lubrication (EHL). When the velocity is adequately low (i.e., film thickness is thin enough), the pressure distribution in the contact area is close to Hertzian distribution in which the second ridge of pressure is not obvious enough. The film shape demonstrates the earlobe-like form in thin film lubrication, which is similar to EHL while the film is comparatively thicker. The transformation relationships between film thickness and loads, velocities or atmosphere viscosity in thin film lubrication differ from those in EHL so that the transition from thin film lubrication to EHL can be clearly seen.

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Zhang, Yongbin, and Guoshen Lu. "Model of Elastohydrodynamic Lubrication with Molecularly Thin Lubricating Films. Part II: Results for an Exemplary Lubrication." International Journal of Fluid Mechanics Research 30, no. 5 (2003): 558–71. http://dx.doi.org/10.1615/interjfluidmechres.v30.i5.80.

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Jin, Z. M., D. Dowson, J. Fisher, N. Ohtsuki, T. Murakami, H. Higaki, and S. Moriyama. "Prediction of transient lubricating film thickness in knee prostheses with compliant layers." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 212, no. 3 (March 1, 1998): 157–64. http://dx.doi.org/10.1243/0954411981533935.

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The transient lubricating film thickness in knee prostheses using compliant layers has been predicted under simulated walking conditions based upon the elastohydrodynamic lubrication theory. Qualitative agreement has been found between the present theoretical predictions and the experimental measurements using an electric resistance technique reported earlier. It has been shown that the contact geometry plays an important role in the generation of fluid film lubrication in knee prostheses using compliant layers. The maximum lubricating film thickness is predicted for the maximized contact area of a transverse conjunction where the semi-minor contact radius lies in the direction of entraining. The additional advantage of the transverse contact conjunction is that the possibility of lubricant starvation due to small stroke length can be minimized. All these factors, together with the kinematic requirements in the natural knee joint, should be taken into consideration when designing artificial knee joint replacements.

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Wang, Bao Ming, Xia Lun Yun, Xing Yao Liao, and Xue Song Mei. "Analysis of Thermal Effect on Elastohydrodynamic Lubrication in Angular Contact Ball Bearing." Applied Mechanics and Materials 741 (March 2015): 443–48. http://dx.doi.org/10.4028/www.scientific.net/amm.741.443.

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Based on the theory of point contact thermal elastohydrodynamic lubrication (EHL),the mathematical models for the thermal EHL of high-speed angular contact ball bearing are established. Multi-grid method and multigrid integration method are respectively used to calculate out the film pressure and film thickness respectively,and the column-by-column scanning method is used to calculate temperature rise of isothermal EHL and thermal EHL. The calculation results show that, under the pure rolling condition, temperature rise of oil film temperature is mainly caused by the compression work and shear heat at inlet and the heat in contact zone mainly comes from the inlet and the heat conduction around; the temperature rise results in oil viscosity lower and the lubricating film thinner ,in this way it reduces the lubrication performance in contact pair.

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Jin, Z. M., D. Dowson, J. Fisher, D. Rimmer, R. Wilkinson, and B. Jobbins. "Measurement of Lubricating Film Thickness in Low Elastic Modulus Lined Bearings, with Particular Reference to Models of Cushion Form Bearings for Total Joint Replacements: Part 1: Steady State Entraining Motion." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 208, no. 3 (September 1994): 207–12. http://dx.doi.org/10.1243/pime_proc_1994_208_372_02.

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The lubricating film thickness in a model of compliant layered bearings for total joint replacements has been measured by means of optical interferometry under entraining motion. The essential features of the present interferometry technique were off-normal incidence light, a combination of polyurethane elastomer and a crown glass plate as bearing surfaces and the use of silicone fluid or water as lubricants. The film thickness in the lubricated contact was measured for both water and silicone fluid under a range of entraining velocities. Reasonable agreement was found between the experimental measurements of the lubricating film thickness and the theoretical predictions based upon elastohydrodynamic lubrication analysis.

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Brodsky, Emily E., and Hiroo Kanamori. "Elastohydrodynamic lubrication of faults." Journal of Geophysical Research: Solid Earth 106, B8 (August 10, 2001): 16357–74. http://dx.doi.org/10.1029/2001jb000430.

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31

Huang, P., and S. Z. Wen. "Sectional Micro-Elastohydrodynamic Lubrication." Journal of Tribology 115, no. 1 (January 1, 1993): 148–51. http://dx.doi.org/10.1115/1.2920968.

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A method has been introduced to solve micro-EHL problems, with the discontinuous pressure distribution caused by high surface roughnesses. Treatments of inner boundary conditions, flow continuity, and deformation compatibility are given in detail. Examples of different sectional micro-EHL problems show that the method is efficient. The solutions of micro-EHL problems with the small film ratio are presented and discussed.

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32

Hutton, J. F. "Rheology and elastohydrodynamic lubrication." Journal of Non-Newtonian Fluid Mechanics 43, no. 2-3 (July 1992): 377–81. http://dx.doi.org/10.1016/0377-0257(92)80034-u.

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Hamilton, G. M. "Rheology and elastohydrodynamic lubrication." Tribology International 25, no. 4 (January 1992): 293. http://dx.doi.org/10.1016/0301-679x(92)90067-w.

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34

Liu, X.-L., P. Yang, and P.-R. Yang. "Analysis of the lubricating mechanism for tilting rollers in rolling bearings." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 225, no. 11 (September 23, 2011): 1059–70. http://dx.doi.org/10.1177/1350650111413839.

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In practice, the tilting roller occurs widely in rolling bearings. In order to investigate the lubricating mechanism of tilting rollers in rolling bearings, a contact between a tilting cylindrical roller and an infinite plane is assumed in the present paper. Using the multi-grid method, a numerical solution has been obtained for the isothermal elastohydrodynamic lubrication of the contact. The film thickness and pressure with different tilt angles have been given. Results show that the property of the tilting roller’s lubrication is different from that of the parallel roller contact investigated in the past, and asymmetry is common both for the film thickness and the oil pressure under tilting conditions. Moreover, the larger the tilt angle, the smaller the minimum film thickness, and the more easily the local wear occurs in bearings. The effects of the maximum Hertzian pressure, velocity parameter, and length and end profile radius of the roller on the lubricating performance of the contact have been discussed. The conclusion can be made that better lubrication of tilting roller contact needs light load, high velocity parameter, short length, and larger end profile radius of the roller. Comparisons between the starved and fully flooded lubrication in the tilting roller contact have been given, and it has been found that starvation status can worsen the lubrication and reduce the life of roller bearings.

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Boure´, Ph, D. Mazuyer, J. M. Georges, A. A. Lubrecht, and G. Lorentz. "Formation of Boundary Lubricating Layers With Water-Based Lubricant in a Concentrated Elastohydrodynamic Contact." Journal of Tribology 124, no. 1 (March 7, 2001): 91–102. http://dx.doi.org/10.1115/1.1398549.

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The lubrication with oil-in-water emulsions is usually supposed to be governed by the oil phase being concentrated in a reservoir that supplies the contact. In this paper, another lubrication process in an elastohydrodynamic ball/disc contact is presented. It is found that above a critical entrainment speed a thick film grows in the contact with time and reaches a limiting thickness. Viscous adherent boundary layers are formed and observed on both the surfaces. Pressure and speed are required for the film build-up. An additional sliding speed at constant entrainment speed induces a shearing at the interface between the boundary layers and the substrate that depends on the nature of the contacting surface. It is shown that these high viscosity boundary films ensure a starved lubrication. The modelling of the starvation process allows us to evaluate the viscosity of these boundary layers and their mean supply rate to the contact. A fine analysis of this latter parameter shows that the lubricating film results from the equilibrium between the flow rate of lubricating particles in the inlet zone and the amount of particles that cannot stay in the contact between two passages which strongly depends on the entrainment speed. A classical adsorption process does not seem responsible for the anchorage of the boundary films to the surfaces. The adherence of the films is explained by an approach based on electric interactions between ionic surfactants and the oxidized metallic surfaces according to the position of their isoelectric point compared to the pH of the emulsion.

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Shi, Xiujiang, Jiqiang Wu, Bin Zhao, Xuan Ma, and Xiqun Lu. "Mixed thermal elastohydrodynamic lubrication analysis with dynamic performance of aero ball bearing during start-up and shut-down." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 234, no. 6 (January 23, 2020): 873–86. http://dx.doi.org/10.1177/1350650119900401.

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In this study, a coupling model is developed to include the aero ball bearing dynamic performance in the mixed thermal elastohydrodynamic lubrication analysis, and the low-speed and heavy-load conditions during start-up and shut-down are involved. Based on the bearing quasi-dynamics, the inside motion state of the main loading surface is obtained, and the mixed thermal elastohydrodynamic lubrication is conducted to get bearing lubrication state and properties. The numerical lubrication model under low-speed and heavy-load conditions is validated against published tested data, which reveal well consistency in central film thickness. The lubrication properties between a single ball and inner race during start-up have been studied, which indicate the lubrication film transforms from boundary lubrication to unsafe mixed thermal elastohydrodynamic lubrication, and then goes into safe lubrication. The lubrication properties of the balls at different azimuths have been investigated during shut-down and compared with those in start-up, which have a similar opposite changing trend, but not a simple invertible process. The time in boundary lubrication region during shut-down is shorter, and the ball number in boundary lubrication region gets less, which means the lubrication properties are relatively better. At last, the parametric study on mixed thermal elastohydrodynamic lubrication properties during shut-down has been carried out. It is found that the small bearing curve coefficient and increasing ball number can reduce the boundary lubrication time and improve the bearing lubrication.

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Kharchenko, M. V., V. N. Kononov, and E. S. Zambrgitckaya. "Elastohydrodynamic Friction Mode as a Method of Surface Finishing Excluding Burnishing." Materials Science Forum 946 (February 2019): 732–38. http://dx.doi.org/10.4028/www.scientific.net/msf.946.732.

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Over the past decades the science of friction has got great development. Processes of friction and wear significantly depend on constructive junction design, selection of wear resistant materials and effective lubricants for them, as well as the conditions of the machinery operation. Currently, a large number of scientific works [7-11, 16-20] are devoted to the review of the contact interaction conditions with the use a lubricant. The method of elastohydrodynamic lubrication is of particular interest when studying different kinds of lubrication. According to the elastohydrodynamic lubrication theory, contact conditions of two elastic bodies are characterized by high pressures which cause the elastic deformation of solids and by the dependence of a lubricant viscosity from the pressure. When using the elastohydrodynamic lubrication the layer profile, the sum amount of elastic deformations, elastic deformations and the lubricant viscosity dependence from pressure are given by set equations [12-15]. The impact of elastohydrodynamic lubrication method on the surface layer of the contacting parts is of great interest.

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Du, Li Jun, Yao Yao Hong, and She Miao Qi. "Analysis of EHL Line Contact in Rapid Braking Motion." Applied Mechanics and Materials 318 (May 2013): 220–24. http://dx.doi.org/10.4028/www.scientific.net/amm.318.220.

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As is well known, almost all the machines need to start and brake. In this process, the lubrication state of their parts changes instantaneously. In this paper, an isothermal study for the line contact elastohydrodynamic lubrication (EHL), which is in rapid braking process and under a constant load, is carried out by using a simplified multigrid method. Numerical results indicate that the oil film thickness decreases and the oil film pressure increases with the decrease of the speed during the process of rapid braking. The oil film shrinks quickly and the oil entrapment occurs when the speed reduces to a certain range. Simultaneously, the distribution of oil film pressure tends to the central lubrication area. The size of the oil entrapment area and the changes of the oil film pressure are closely related to the braking time and the initial speed, which reflects the transient effects of the lubricating oil film.

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Zhao, Jin Zhi, Yuan Tao Liu, and Ze Xiang Zhao. "Research on Web-Based Elastohydrodynamic Lubrication Oil Theory of Rolling Bearing Type Planetary Friction Transmission Mechanism." Applied Mechanics and Materials 151 (January 2012): 155–59. http://dx.doi.org/10.4028/www.scientific.net/amm.151.155.

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Service mode and dynamic network interfere techniques are analyzed. An elastohydrodynamic lubrication oil thickness theory of rolling bearing type planetary friction transmission mechanism system based on web is presented.Elastohydrodynamic lubrication theory is adopted in rolling bearing type planetary friction transmission mechanism in this paper. Research indicates that elastohydrodynamic oil file lubrication can be realized while mechanical parts with connection between points or lines run under certain conditions. At the same time, surface disrepair of the parts has relation to lubrication state. Minimal oil film thickness formula is deduced based on the elastohydrodynamic lubrication theory. It is a part of He’nan Scientific Committee science and technology research projects 《research on collaborative design and manufacturing technique in gear manufacturing based on network and multi-Agent》

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40

Katyal, Puneet, and Punit Kumar. "A simplified approach for thermal elastohydrodynamic lubrication analysis of circular contacts using realistic lubricant properties." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 232, no. 12 (February 23, 2018): 1618–32. http://dx.doi.org/10.1177/1350650118760613.

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Thermal effect in elastohydrodynamic lubrication has been the subject of extensive research for several decades. The focus of this study was primarily on the development of an efficient numerical scheme to deal with the computational challenges involved in the solution of thermal elastohydrodynamic lubrication model; however, some important aspects related to the accurate description of lubricant properties such as viscosity, rheology, and thermal conductivity in elastohydrodynamic lubrication point contact analysis remain largely neglected. A few studies available in this regard are based upon highly complex mathematical models difficult to formulate and execute. The end-users may not have the specialized skill, knowledge, and time required for the development of computational codes pertaining to these models. Therefore, this paper offers a very simple approach to determine the distribution of mean fluid temperature within an elastohydrodynamic lubrication film. While it is an approximate method, it yields reasonably accurate results with only a little increase in computation time with respect to the isothermal case. Moreover, it can be added as a small module to any existing isothermal algorithm. Using this simplified thermal elastohydrodynamic lubrication model for point contacts, this work sheds some light on the importance of accurate characterization of the lubricant properties and demonstrates that the computed thermal elastohydrodynamic lubrication characteristics are highly sensitive to lubricant properties. It also emphasizes the use of appropriate mathematical models with experimentally determined parameters to account for the correct lubricant behavior.

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41

Fan, Zhi Min, and Zhao Qiang Zhang. "Study on Elastohydrodynamic Lubrication of Double Involute Gear Drive." Advanced Materials Research 753-755 (August 2013): 1723–26. http://dx.doi.org/10.4028/www.scientific.net/amr.753-755.1723.

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Double involute gear drive was a new type of gear drive, which had high bending strength, small vibration and low noise. In this paper, the lubrication characteristics of the new type of gear had been studied, the model of elastohydrodynamic lubrication had been simplified and analyzed by geometric, and the mathematical model used for numerical analysis of elastohydrodynamic lubrication had been established.

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MAWATARI, Toshifumi, Yohei SAKAMOTO, Zhang BO, and Nobuyoshi OHNO. "Study on High Pressure Physical Property of Lubricating Oil and Impact Elastohydrodynamic Lubrication." Proceedings of the Symposium on Evaluation and Diagnosis 2017.16 (2017): 118. http://dx.doi.org/10.1299/jsmesed.2017.16.118.

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Alakhramsing, Shivam S., Matthijn B. de Rooij, Dirk J. Schipper, and Mark van Drogen. "A full numerical solution to the coupled cam–roller and roller–pin contact in heavily loaded cam–roller follower mechanisms." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 232, no. 10 (December 9, 2017): 1273–84. http://dx.doi.org/10.1177/1350650117746899.

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In cam–roller follower units two lubricated contacts may be distinguished, namely the cam–roller contact and roller–pin contact. The former is a nonconformal contact while the latter is conformal contact. In an earlier work a detailed transient finite line contact elastohydrodynamic lubrication model for the cam–roller contact was developed. In this work a detailed transient elastohydrodynamic lubrication model for the roller–pin contact is developed and coupled to the earlier developed cam–roller contact elastohydrodynamic lubrication model via a roller friction model. For the transient analysis a heavily loaded cam–roller follower unit is analyzed. It is shown that likewise the cam–roller contact, the roller–pin contact also inhibits typical finite line contact elastohydrodynamic lubrication characteristics at high loads. The importance of including elastic deformation for analyzing lubrication conditions in the roller–pin contact is highlighted here, as it significantly enhances the film thickness and friction coefficient. Other main findings are that for heavily loaded cam–roller follower units, as studied in this work, transient effects and roller slippage are negligible, and the roller–pin contact is associated with the highest power losses. Finally, due to the nontypical elastohydrodynamic lubrication characteristics of both cam–roller and roller–pin contact numerical analysis becomes inevitable for the evaluation of the film thicknesses, power losses, and maximum pressures.

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44

Gao, L. M., Q. E. Meng, F. Liu, J. Fisher, and Z. M. Jin. "The effect of aspherical geometry and surface texturing on the elastohydrodynamic lubrication of metal-on-metal hip prostheses under physiological loading and motions." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, no. 12 (June 23, 2010): 2627–36. http://dx.doi.org/10.1243/09544062jmes2193.

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As an alternative material combination, metal-on-metal (MOM) hip replacement has attracted a revived interest due to its very low wear rates. In this article, an elastohydrodynamic lubrication analysis is performed for an MOM hip replacement with specific geometrical designs: a macro Alpharabola geometry of the cup bearing surface and micro-dimples on the head surface. The corresponding numerical methodology is presented and full numerical solutions are obtained. The effect of the macro- and micro-geometrical designs on the lubrication performance is investigated, under both simplified and physiological walking conditions. The real physiological loading and motion conditions are important to be considered when optimizing the conformity-associated geometry of hip bearings. The Alpharabola geometry of cup bearing surface is found to significantly improve the lubricating film thickness and reduce hydrodynamic pressure of MOM hip implants, when the Alpharabola minimum radius is aligned with the loading direction. Dimpled surface texturing has an adverse effect in a fluid film lubrication regime under the conditions considered in this study.

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45

Li, Linlin, and Jiajun Yang. "A study of dynamic behaviors of contact pair in lubricated ball linear guide." Industrial Lubrication and Tribology 70, no. 4 (May 8, 2018): 746–53. http://dx.doi.org/10.1108/ilt-07-2017-0198.

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Purpose This paper aims to predict the dynamic behaviors of contact between the steel ball and raceway in the elastohydrodynamically lubricated ball linear guide, thus providing a guidance for lubrication design for ball linear guide. Design/methodology/approach Based on the point contact elastohydrodynamic lubrication (EHL) theory, the free vibration model of contact pair is presented to qualitatively analyze the effect of vibration on the film characteristics. The models of the film stiffness and damping coefficient under the EHL condition are built to investigate the effects of the working conditions on the dynamic parameters. The full numerical solutions are obtained using the multigrid technique. Findings It is found that there exists damping from the decay of oscillations of the pressure and film thickness in the lubricated ball linear guide. Furthermore, the working conditions of the high load or low velocity can lead to the increase in the film stiffness in the steel ball-raceway contact, but there is a reverse variation trend for the film damping coefficient. Originality/value The contact pair has been usually treated as dry in past studies on dynamics of the ball linear guide, and the damping is neglected. This research considers the actual lubrication and working conditions and predicts the dynamic behaviors of contact pair.

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46

Yoshimura, Takao, Kyosuke Ono, Koˆ Inagaki, Hideki Kotsuka, and Atsushi Korenaga. "Analysis of Lubricating Characteristics of Rotary Compressors for Domestic Refrigerators." Journal of Tribology 121, no. 3 (July 1, 1999): 510–16. http://dx.doi.org/10.1115/1.2834097.

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We investigated the lubricating characteristics between a vane and piston lubricated with an oil-refrigerant mixture. Theoretical analyses were performed using mixed elastohydrodynamic lubrication analysis theory, taking metallic contacts into account. Lubricating conditions were evaluated by comparing the theoretical results of piston dynamics based on actual surface roughness distributions measured by SEM, with the experimental results measured under practical operation. We conclude that (1) lubricating conditions between the vane and piston can be assumed to be within the mixed lubricating zone, in which the coefficient of friction changes from 0.04 to 0.08, and the contact force is almost equally supported by oil film and metallic contact; (2) the coefficient of friction decreases as the contact force increases because the ratio of pressure rise of the oil film to the decrease in clearance is much greater than that for metallic contact pressure; and (3) in mixed EHL analysis, it is important not only to measure the actual surface roughness but also to select the appropriate contact model.

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Spikes, H. "The borderline of elastohydrodynamic and boundary lubrication." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 214, no. 1 (January 1, 2000): 23–37. http://dx.doi.org/10.1243/0954406001522787.

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There is a growing trend for lubricated systems to operate for much of their operating life with very thin lubricating films. This paper reviews our current understanding of such films, at the borderline between elastohydrodynamic and boundary lubrication. The nature and properties of these films are very complex, since the proximity of the solid surfaces influences the structure and rheology of thin liquid layers, while boundary films can, themselves, possess rheological characteristics that vary with thickness. Novel experimental tools, such as atomic force microscopy and ultra-thin-film interferometry have greatly accelerated our understanding of this area in the last few years and it has recently become possible to map lubricant film thickness within rough surface contacts. These tools are beginning to provide the level of understanding of thin-film rough surface behaviour required to develop accurate numerical and simulation models. The next 5 years should see a very rapid progression of our understanding of this important regime.

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Katyal, Puneet, and Punit Kumar. "Effect of arbitrary entrainment angle in elastohydrodynamic lubrication elliptical and circular contacts." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 234, no. 3 (July 27, 2019): 424–34. http://dx.doi.org/10.1177/1350650119863998.

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Conventional elastohydrodynamic lubrication models assume parallel surface velocities such as in cam-follower and ball bearing systems. However, many important machine elements like hypoid gear and spiral bevel, the sliding and entrainment velocities are along different directions that could possibly influence the elastohydrodynamic lubrication performance characteristics significantly. For such complex conditions, the existing film thickness formulae and shear-thinning correction factors available in the literature are not suitable. Therefore, this paper investigates the effect of arbitrarily oriented surface velocity vectors on elastohydrodynamic lubrication characteristics considering realistic rheological models and experimentally established viscosity–pressure and compressibility laws. The Reynolds equation employed herein includes the surface velocity components along both the reference axes in the plane of contact. The elastohydrodynamic lubrication film thickness is found to deviate up to a maximum of 61% with respect to its conventional value. This deviation in film thickness behavior is shown to be a function of ellipticity and shear-thinning parameters.

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Wongseedakaew, Khanittha, and Jesda Panichakorn. "Rough Air-Soft Elastohydrodynamic Lubrication." Applied Mechanics and Materials 420 (September 2013): 30–35. http://dx.doi.org/10.4028/www.scientific.net/amm.420.30.

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This paper presents the effects of rough surface air-soft elastohydrodynamic lubrication (EHL) of rollers for soft material under the effect of air molecular slip. The time independent modified Reynolds equation and elasticity equation were solved numerically using finite different method, Newton-Raphson method and multigrid multilevel methods were used to obtain the film pressure profiles and film thickness in the contact region. The effects of amplitude of surface roughness, modulus of elasticity and air inlet temperature are examined. The simulation results showed surface roughness has effect on film thickness but it little effect to air film pressure. When the amplitude of surface roughness and modulus of elasticity increased, the air film thickness decreased but air film pressure increased. However, the air inlet temperature increased when the air film thickness increased.

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Oh, K. P., C. H. Li, and P. K. Goenka. "Elastohydrodynamic Lubrication of Piston Skirts." Journal of Tribology 109, no. 2 (April 1, 1987): 356–62. http://dx.doi.org/10.1115/1.3261366.

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The elastohydrodynamic lubrication of an automotive piston was analyzed. The important effects of thermal and pressure distortions were demonstrated by analyzing two piston skirts which have different axial profiles but are otherwise identical. Results show that a significant reduction in friction can be realized.

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Journal articles on the topic 'Elastohydrodynamical lubrication'

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