Publications
472 results found
Spikes H, 2006, Origins of the friction and wear properties of antiwear additives, Lubrication Science, Vol: 18, Pages: 223-230, ISSN: 0954-0075
Experimental techniques have been developed to measure the friction, antiwear film-forming and wear properties of lubricants in rolling-sliding contact. Friction measurements show that zinc dialkyldithiophosphates (ZDDPs) and also some other phosphorus-based additives increase friction in mixed lubrication. Film thickness measurements show that this increase in friction correlates with the thickness of antiwear film. They also reveal some of the drivers of antiwear film formation and removal. A novel wear tester is described which enables the mild wear resulting from ZDDP-containing oils to be monitored. Copyright © 2006 John Wiley & Sons, Ltd.
de Vicente J, Stokes JR, Spikes HA, 2006, Soft lubrication of model hydrocolloids, FOOD HYDROCOLLOIDS, Vol: 20, Pages: 483-491, ISSN: 0268-005X
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- Citations: 142
Spikes HA, 2006, Sixty years of EHL
The birth of EHL took place in 1945 and is graphically described by Cameron. Sixty years have elapsed since then, during which period EHL has progressed from infancy to maturity. A discussion presented at the 15th International Colloquium Tribology-Automotive and Industrial Lubrication (Ostfildern, Germany 1/17-19/2006), covers the development of EHL research; numerical solutions of the line contact EHL problem; and optical interference image from point contact.
Van Beek A, Van Ostayen RAJ, Spikes HA, 2006, Viscoelastic behavior of soft layered EHL curved slider bearings
The design of a water lubricated shaftless propeller bearing arrangement is presented. Because the bearing arrangement has to function in an aqueous environment, a polymer layer is applied at one of the bearing surfaces to obtain good start-stop conditions in the boundary lubrication regime and to obtain EHL at higher surface velocities. To properly design the bearing arrangement, consisting of multiple curved bearing pads sliding on the soft polymer layer, it is essential to be able to predict the effect of the viscoelastic material behavior on the formation of the thin lubricant film. The numerical model applied covers the hydrodynamic pressure distribution in a thin lubricant film and the elastic deformation of one of the slide surfaces. Both problems are coupled by the pressure distribution over the thin film. The pressure distribution depends on the film thickness profile and thus on deformation. The elastic deformation depends on the pressure. This is an abstract of a paper presented at the 15th International Colloquium Tribology - Automotive and Industrial Lubrication (Ostfildern, Germany 1/17-19/2006).
De Vicente J, Stokes J, Spikes H, 2006, Soft-EHL - The tribology of tyres and tongues
Thick hydrodynamic lubricant films can be formed in soft-EHL contacts, even by low viscosity lubricants such as aqueous solutions, and this has practical relevance in both engineering and biological applications. Work to measure the friction of simple Newtonian liquids in soft-EHL contacts over a wide range of entrainment speeds and viscosities is presented. A new technique is described for separating the rolling and sliding components of friction. To study the boundary lubrication regime, solutions of a surfactant Tween 80 (ethoxylated-60-sorbitan monostearate) are examined. This is an abstract of a paper presented at the 15th International Colloquium Tribology - Automotive and Industrial Lubrication (Ostfildern, Germany 1/17-19/2006).
Miklozic KT, Forbus R, Spikes HA, 2006, Friction performance of combined antiwear and friction modifier systems
A study on the friction and tribo-film properties when molybdenum dithiocarbamate (MoDTC) solution lubricates surfaces covered with previously-formed zinc dithiophosphate (ZDDP) film was carried out. For the MoDTC oil solution, a remarkable friction reduction of coefficient of friction was observed in the boundary lubrication regime. Some alteration of the previously-formed ZDDP film could be seen. This is an abstract of a paper presented at the 15th International Colloquium Tribology-Automotive and Industrial Lubrication (Ostfildern, Germany 1/17-19/2006).
Fujita H, Spikes HA, 2006, The study of antiwear film formation kinetics
Despite the demand for a progressive decrease in phosphorus concentration in engine oils to reduce impact on the de-NOx catalyst and diesel particulate filter, ZnDTP have not yet been replaced completely by other antiwear additives. A study on the influence of ZnDTP type and concentration of dispersant on the antiwear film formation process was carried out. ZnDTP type strongly affected the formation process. Dispersant inhibited the antiwear film from being generated on rubbed surface and this effect increased with dispersant concentration. Film formation models and formula were discussed, which stimulate the film formation process. This is an abstract of a paper presented at the 15th International Colloquium Tribology-Automotive and Industrial Lubrication (Ostfildern, Germany 1/17-19/2006).
Fan JY, Muller M, Spikes H, 2006, Reduction of wear using functionalised PAMA viscosity modifiers
The wear performance of dispersant polyalkylmethacrylates (d-PAMA) was studied under pure sliding and mixed sliding/rolling conditions. Reference base oil and blends of functionalized PAMA and non-functionalized PAMA were tested using Bi-direction Mini Traction Machine and Inductively Coupled Plasma Atomic Emission Spectroscopy. Significant reductions in wear could be produced by appropriate concentrations of some functionalized PAMA. This is an abstract of a paper presented at the 15th International Colloquium Tribology - Automotive and Industrial Lubrication (Ostfildern, Germany 1/17-19/2006).
de Vicente J, Stokes JR, Spikes HA, 2006, Rolling and sliding friction in compliant, lubricated contact, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY, Vol: 220, Pages: 55-63, ISSN: 1350-6501
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- Citations: 39
Cambiella A, Benito JM, Pazos C, et al., 2006, The effect of emulsifier concentration on the lubricating properties of oil-in-water emulsions, TRIBOLOGY LETTERS, Vol: 22, Pages: 53-65, ISSN: 1023-8883
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- Citations: 76
Spikes HA, Fan J, 2006, Design of polymeric lubricant additives to reduce friction and wear, 231st National Meeting of the American-Chemical-Society, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Fowell MT, Olver AV, Pegg IG, et al., 2006, Two mechanisms of hydrodynamic lubrication in textured bearings
There is currently great interest in the use of textured bearings, where many tiny micropockets are incorporated in one of the bearing surfaces. Such texturing has been found to enhance load support and to reduce hydrodynamic friction in low load conditions, when the two surfaces have very low or zero convergence ratio, i.e. are essentially parallel. It is not immediately clear from hydrodynamic lubrication theory how a bearing with parallel surfaces and internal pockets can entrain any lubricant to form a hydrodynamic film and thus support load. However in a recent technical note the authors have shown that the occurrence of cavitation within micropockets results in suction of lubricant into the bearing, because the pressure inside the pockets is less than the surrounding, atmospheric pressure [1]. For parallel or very low convergence ratio bearings, this supply process replaces fluid entrainment as the main mechanism by which lubricant is drawn into the contact. In previous work this suction mechanism was demonstrated using a simple analytical approach for a 1D parallel bearing having a single pocket. The current paper extends this analytical method to convergent bearings having a single pocket and then applies a numerical solution of the first order Reynolds equation to solve for flow in multi-pocketed bearings. This enables the contribution of fluid suction on the load support of low convergence ratio bearings to be investigated. Copyright © 2006 by ASME.
Choo JW, Olver AV, Spikes HA, et al., 2006, The influence of longitudinal roughness in thin-film, mixed elastohydrodynamic lubrication, TRIBOLOGY TRANSACTIONS, Vol: 49, Pages: 248-259, ISSN: 1040-2004
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- Citations: 22
Müller M, Topolovec-Miklozic K, Dardin A, et al., 2006, The design of boundary film-forming PMA viscosity modifiers, TRIBOLOGY TRANSACTIONS, Vol: 49, Pages: 225-232, ISSN: 1040-2004
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- Citations: 61
Olver AV, Fowell MT, Spikes HA, et al., 2006, 'Inlet suction', a load support mechanism in non-convergent, pocketed, hydrodynamic bearings, Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, Vol: 220, Pages: 105-108, ISSN: 1350-6501
Lee-Prudhoe I, Venner CH, Cann PM, et al., 2006, Experimental and theoretical approaches to thin film lubrication problems, IUTAM SYMPOSIUM ON ELASTOHYDRODYNAMICS AND MICRO-ELASTOHYDRODYNAMICS, Vol: 134, Pages: 241-+, ISSN: 0925-0042
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- Citations: 3
de Vicente J, Stokes JR, Spikes HA, 2006, Rolling and sliding friction in compliant, lubricated contact, Proceedings- Institution of Mechanical Engineers Part J Journal of Engineering Tribology, Vol: 220, Pages: 55-64, ISSN: 1350-6501
Hartinger M, Gosman D, Ioannides S, et al., 2005, CFD modelling of elastohydrodynamic lubrication, Pages: 531-532
The finite volume method was evaluated to model fluid behavior in rolling-element bearing systems. The effect of cavitation was modeled with a barotropic cavitation model. Two cases with a cylinder on a flat plate, one under rolling and one under sliding conditions, were studied. These solutions were compared to the Reynolds-EHL approach. Towards higher loads, stability problems were encountered and strategies for dealing with these were presented. This is an abstract of a paper presented at the World Tribology Congress III (Washington, DC 9/12-16/2005).
Olver AV, Glovnea R, Choo JW, et al., 2005, Elastohydrodynamic lubrication of multiple periodic ridges, Pages: 519-520
The lubrication of rolling contacts in which one surface has a roughness consisting of periodic transverse or longitudinal ridges has been widely investigated, both theoretically and experimentally. Results of these investigations now permit a substantially complete picture to emerge in which it is possible to characterize the state of lubrication by evaluating and comparing the (minimum) film thickness near the crests of the roughness to the corresponding thickness in the valleys. Crest and valley film thickness were studied over a wide range of non-dimensional speed. Two lubricants were used, both Group I mineral oils with viscosities of 22 and 453 cp and alpha values of 19.8 and 20.4/GPa. The elastostatic and asperity values agreed well with the corresponding measurements but both crest and valley measured film thicknesses exceeded the predictions of equation 4 for higher speeds. This is an abstract of a paper presented at the World Tribology Congress III (Washington, DC 9/12-16/2005).
Glovnea RP, Spikes HA, 2005, EHD contacts in low-amplitude oscilatory motion, Pages: 455-456
In some practical applications such as spline couplings or constant velocity joints, the machine components are subjected to a low amplitude lateral motion, very often oscillatory, so that conditions for a full elastohydrodynamic film to form are not completely realized. The questions that arise are what mechanism of lubricating takes place in such contacts and what is the influence of working parameters and lubricant properties on such mechanism? In the present study, a EHD contact formed between a flat and a ball is subjected to oscillatory-motion of amplitude ranging between one half to one contact diameter. High speed ultra-thin film interferometry is used to monitor the gap between the two solid surfaces. The influence of parameters such as load, frequency and amplitude of motion are investigated. Copyright © 2005 by ASME.
de Vicente J, Stokes JR, Spikes HA, 2005, The frictional properties of newtonian fluids in rolling-sliding soft-EHL contact, TRIBOLOGY LETTERS, Vol: 20, Pages: 273-286, ISSN: 1023-8883
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- Citations: 131
Fujita H, Glovnea RP, Spikes HA, 2005, Study of zinc dialkydithiophosphate antiwear film formation and removal processes, part I: Experimental, TRIBOLOGY TRANSACTIONS, Vol: 48, Pages: 558-566, ISSN: 1040-2004
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- Citations: 101
Cann PM, Spikes HA, 2005, Measurement of pressure distribution in EHL - Development of method and application to dry static contacts, TRIBOLOGY TRANSACTIONS, Vol: 48, Pages: 474-483, ISSN: 1040-2004
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- Citations: 11
Fujita H, Spikes HA, 2005, Study of zinc dialkyldithiophosphate antiwear film formation and removal processes, part II: Kinetic model, TRIBOLOGY TRANSACTIONS, Vol: 48, Pages: 567-575, ISSN: 1040-2004
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- Citations: 72
Braidic-Mitidieri P, Gosman AD, Ioannides E, et al., 2005, CFD analysis of a low friction pocketed pad bearing, JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME, Vol: 127, Pages: 803-812, ISSN: 0742-4787
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- Citations: 84
Mueller MA, Stoehr T, Eisenberg B, et al., 2005, Synthesis and characterization of polyalkylmethacrylate block copolymers and their application in high performance lubricants, 230th National Meeting of the American-Chemical-Society, Publisher: AMER CHEMICAL SOC, Pages: U4316-U4316, ISSN: 0065-7727
Cann PM, Spikes HA, 2005, In-contact IR spectroscopy of hydrocarbon lubricants, TRIBOLOGY LETTERS, Vol: 19, Pages: 289-297, ISSN: 1023-8883
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- Citations: 55
Dardin A, Hedrich K, Müller M, et al., 2005, Influence of polyalkylmethacrylate viscosity index improvers on boundary film formation and efficiency of lubricants, Tribologia, Vol: 24, Pages: 3-14, ISSN: 0780-2285
The efficiency of lubricated machine elements such as transmissions, crankcase engines, and hydraulic pumps depends strongly on the friction properties of the lubricant employed. For the design of modern, highly efficient lubricants it is thus essential to understand the influence of the components of the lubricating fluid in terms of boundary film formation and friction. PAMAs are well-known as viscosity index improve rs and dispersant boosters. This paper shows that PAMAs are able to adsorb from oil solution on to metal surfaces, to produce thick, viscous boundary films. These films enhance lubricant film formation in slow speed and high temperature conditions and thus produce a significant reduction in friction in engine and transmission lubrication. A systematic study of this phenomenon has made use of the highly flexible nature of PAMA chemistry. A range of dispersant and non-dispersant polymethacrylates has been synthesised having different functionalities, molecular weights and architectures. The influence of each of these factors on both boundary film formation and friction has been explored using optical interferometry and friction-speed charting. From the results, guidelines have been developed for designing PAMAs having optimal boundary lubricating properties. Bench tests which more closely simulate the proposed application of the lubricants have been used to measure their torque transmitting efficiency (FZG gear test). First results from these tests demonstrate that the identified structure-property relations can be transferred into real gear and ATF oils.
Glovnea RP, Olver AV, Spikes HA, 2005, Experimental investigation of the effect of speed and load on film thickness in elastohydrodynamic contact, TRIBOLOGY TRANSACTIONS, Vol: 48, Pages: 328-333, ISSN: 1040-2004
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- Citations: 17
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