Publications
472 results found
Chang H, Spikes HA, Bunemann TF, 1992, The shear stress properties of ester lubricants in elastohydrodynamic contacts, Journal of Synthetic Lubrication, Vol: 9, Pages: 91-114, ISSN: 0265-6582
<jats:title>Abstract</jats:title><jats:p>This paper describes a systematic study into the influence of molecular structure on lubricant shear stress in elastohydrodynamic (EHD) contacts. An infrared emission technique has been employed to measure surface temperatures in an EHD contact and thence to determine the shear stress profile of lubricant films therein. The effect of structure on shear stress has been investigated by comparing the behaviour of a range of well‐characterised, closely related, ester base fluids. Considerable variations in shear stress response to EHD conditions have been observed, depending upon the type and structure of the ester.</jats:p>
CANN PM, SPIKES HA, 1992, FOURIER-TRANSFORM INFRARED STUDY OF THE BEHAVIOR OF GREASE IN LUBRICATED CONTACTS, LUBRICATION ENGINEERING, Vol: 48, Pages: 335-343, ISSN: 0024-7154
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- Citations: 16
Guangteng G, Cann PM, Spikes HA, 1992, A study of parched lubrication, Wear, Vol: 153, Pages: 91-105, ISSN: 0043-1648
CANN PM, WILLIAMSON BP, COY RC, et al., 1992, THE BEHAVIOR OF GREASES IN ELASTOHYDRODYNAMIC CONTACTS, INTERNATIONAL CONF ON FRONTIERS OF TRIBOLOGY, CELEBRATING THE 10TH ANNIVERSARY OF THE TRIBOLOGY GROUP OF THE INST OF PHYSICS, Publisher: IOP PUBLISHING LTD, Pages: A124-A132, ISSN: 0022-3727
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- Citations: 40
Cann PM, Williamson BP, Coy RC, et al., 1992, The behaviour of greases in elastohydrodynamic contacts, Journal of Physics D: Applied Physics, Vol: 25, Pages: A124-A132, ISSN: 0022-3727
The ability of grease to generate elastohydrodynamic (ehd) films has been studied and interpreted in terms of the response of grease structure to contact conditions. For most liquid lubricants, ehd film thickness depends upon the rheological properties of the fluid in the contact inlet. This mechanism is reasonably well understood for fluids that are Newtonian in behaviour. However, greases have complex bulk structures, the scale of which is larger than the dimensions of a contact inlet. The ehd performance of grease must therefore depend upon the response of grease structure to the high-shear inlet conditions. In this study, ehd film thickness has been measured for a range ol greases using optical interierometry. In parallel work, grease structural changes have been monitored directly in the inlet of ehd contacts using reflection-absorption infrared speciruswjpy. By using these two approaches in combination, changes in composition and loss of bulk grease structure have been observed and correlated with the ability of greases to form films under EHD conditions. © 1992 IOP Publishing Ltd.
Cann PM, Aderin M, Johnston GJ, et al., 1992, An Investigation into the Orientation of Lubricant Molecules in EHD Contacts, Tribology Series, Vol: 21, Pages: 209-218, ISSN: 0167-8922
There is growing evidence from infrared and from computer simulation work that the very high shear stresses associated with elastohydrodynamic (EHD) contacts result in the partial alignment of lubricant molecules. Such an effect has important implications with respect to the lubricant's EHD film forming and traction behaviour. In this Paper, the film formation and alignment of thermotropic liquid crystals are studied in an EHD point contact. Two complementary experimental techniques are employed, in-contact, infrared reflection absorption spectroscopy and polarised, thin film optical interferometry. The work shows the extent and direction of orientation of liquid crystal molecules in EHD contacts and indicates how similar effects can be studied in more conventional lubricants. © 1992, Elsevier B.V. All rights reserved.
Cann PM, Spikes HA, 1992, Film thickness measurements of lubricating greases under normally starved conditions, NLGI SPOKESMAN, Vol: 56, Pages: 61-67, ISSN: 0027-6782
A thin film optical technique developed to study starved grease lubrication is described. Film thickness measurements were taken from a rolling elastohydrodynamic contact operating under both fully-flooded and starved conditions for two lithium hydroxystearate greases. Evidence of residual lubricant films, capable of maintaining contact separation for extended running times is presented. The implications of these results in the context of existing theories of grease lubrication are discussed. (P.M.T.)
Barker DC, Johnston GJ, Spikes HA, 1992, Behaviour of Emulsion Oil Particles in Concentrated Contacts, Tribology Series, Vol: 21, Pages: 493-500, ISSN: 0167-8922
Oil in water emulsions are widely used as hydraulic fluids and rolling oils and need to be able to form lubricating films in these applications. Previous work has shown that some oil in water emulsions have the ability to form EHD films at low rolling speeds but that these collapse at moderate speeds. This paper uses new two techniques, short duration TV microscopy and ultrathin film interferometry, to examine the collapse of EHD films formed by oil in water emulsions as speed is increased. By examining the position of the oil pool meniscus in the EHD inlet it is shown that film collapse occurs due to starvation, of a form identical to that observed with water-free oil systems. Using the ultrathin film technique it is shown that the film in the contact does not reduce to zero as speed is increased but instead appears to reach a steady-state, speed-independent value of around 10 nm thickness. © 1992, Elsevier B.V. All rights reserved.
Saad A, Sayers CR, Wayte R, et al., 1991, Paper V (ii) Piston Ring Face Temperatures in a Firing Diesel Engine, Tribology Series, Vol: 18, Pages: 103-109, ISSN: 0167-8922
A set of sapphire windows have been inserted in the cylinder liner of a Petter AVI diesel engine. This has enabled the temperatures of the piston ring and piston land surfaces to be measured at various points in the cycle of a firing engine using an infrared emission microscope attached to a storage oscilloscope. In this paper the method is described and some results obtained at mid-stroke and top dead centre are presented. These are compared to previous measurements of the bulk temperature of piston rings taken by other workers. © 1991, Elsevier Inc. All rights reserved.
Gunsel S, Wayte R, Spikes HA, 1991, Measurement of the viscosity of thin films of lubricants on solid surfaces, SAE Technical Papers, ISSN: 0148-7191
This paper describes the development of a thin film rheometer able to measure the viscosity of lubricant films of the order of 200 μm thickness on flat, solid surfaces. The rheometer consists of a small cylinder mounted on a piezo bimorph which is divided electrically into two halves. When an AC voltage is applied to the one half of the piezo it causes the flat surface of the cylinder to oscillate in its own plane with an amplitude of a few microns. This motion produces an AC output from the other half of the piezo. The flat face of the cylinder is held parallel to an oily test surface and the latter is supported on a micrometer stage so that the gap between the two surfaces can be adjusted. As the gap is narrowed the oil film dampens the sinusoidal motion of the cylinder and the extent of this damping can be used to determine the viscosity of the oil film between the surfaces. Copyright © 1991 Society of Automotive Engineers, Inc.
Cann PM, Spikes HA, 1991, In Lubro Studies of Lubricants in EHD Contacts Using FTIR Absorption Spectroscopy, Tribology Transactions, Vol: 34, Pages: 248-256, ISSN: 1040-2004
Johnston GJ, Wayte R, Spikes HA, 1991, The Measurement and Study of Very Thin Lubricant Films in Concentrated Contacts, Tribology Transactions, Vol: 34, Pages: 187-194, ISSN: 1040-2004
Black CM, Clark RP, Darton K, et al., 1990, A pyroelectric thermal imaging system for use in medical diagnosis, Journal of Biomedical Engineering, Vol: 12, Pages: 281-286, ISSN: 0141-5425
The value of infra-red thermography in a number of pathologies, notably rheumatology and vascular diseases, is becoming well established. However, the high cost of thermal scanners and the associated image processing computers has been a limitation to the widespread availability of this technique to the clinical community. This paper describes a relatively inexpensive thermographic system based on a pyroelectric vidicon scanner and a microcomputer. Sofware has been written with particular reference to the use of thermography in rheumatoid arthritis and vasospastic conditions such as Raynaud's phenomenon. © 1990.
Wardle RWM, Coy RC, Cann PM, et al., 1990, An ‘in lubro’ study of viscosity index improvers in end contacts, Lubrication Science, Vol: 3, Pages: 45-62, ISSN: 0954-0075
Polymeric viscosity index (VI) improver solutions in oils suffer from both temporary and permanent viscosity losses in high shear hydrodynamic and elastohydrodynamic (EHD) contacts. In some cases in EHD contacts, these losses can be so severe that the additive makes negligible contribution to oil film thickness. This paper describes the use of a combination of optical interferometry and FTIR micro‐reflectance spectroscopy to measure the effectiveness, and to observe directly the behaviour, of conventional VI improver solutions within rolling and sliding EHD contacts. The study shows the extent to which polymers enter EHD contacts and charts the degradation that they suffer therein. Copyright © 1990 John Wiley & Sons, Ltd
Spikes HA, 1990, Instrumental techniques in lubrication. Chester, UK, 28th March 1990, ISSN: 0301-679X
Spikes HA, 1990, A Thermodynamic Approach to Viscosity, Tribology Transactions, Vol: 33, Pages: 140-148, ISSN: 1040-2004
Spikes HA, Cann PM, 1990, The Influence of Sliding Speed and Lubricant Shear Stress on EHD Contact Temperatures, Tribology Transactions, Vol: 33, Pages: 355-362, ISSN: 1040-2004
Spikes HA, 1989, Additive-additive and additive-surface interactions in lubrication., IN: 6TH INT. COLLOQUIUM ON INDUSTRIAL LUBRICANTS - PROPERTIES, APPLICATION, DISPOSAL., (OSTFILDERN, FED. REP GERMANY: JAN 12-, Vol: 1 , Ostfildern, Fed. Rep. Germany, Esslingen Tech. Akad., 1988, Paper 4, p.4.2-1-4.2-12. (ISBN 3-92481
Combinations of additives are often found to exhibit antagonistic or synergistic effects compared to the performance of the individual additives. This paper reviews the state of our knowledge concerning such effects. Direct interactions, where two additives combine at a molecular level are distinguished from complementary of exclusary effects where the individual contributions of separate additives enhance or reduce overall performance, but with no direct interaction. Additive interactions takes place in solution and at surface and both are discussed.
KIMURA Y, OKADA K, 1989, LUBRICATING PROPERTIES OF OIL-IN-WATER EMULSIONS, TRIBOLOGY TRANSACTIONS, Vol: 32, Pages: 524-532, ISSN: 0569-8197
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- Citations: 61
Spikes HA, 1989, Additive‐additive and additive‐surface interactions in lubrication, Lubrication Science, Vol: 2, Pages: 3-23, ISSN: 0954-0075
<jats:title>Abstract</jats:title><jats:p>Combinations of additives are often found to exhibit antagonistic or synergistic effects compared to the performance of the individual additives. This paper reviews the state of knowledge concerning such effects. Direct interactions, where two additives combine at a molecular level, are distinguished from complementary or exclusary effects where the individual contributions of separate additives enhance or reduce overall performance but with no direct interaction. Additive interactions take place in solution and at surfaces, and both are discussed.</jats:p>
Cann PM, Spikes HA, 1989, Determination of the Shear Stresses of Lubricants in Elastohydrodynamic Contacts, Tribology Transactions, Vol: 32, Pages: 414-422, ISSN: 1040-2004
Spikes HA, 1988, Why lubrication science?, Lubrication Science, Vol: 1, Pages: 1-2, ISSN: 0954-0075
Spikes HA, Guangteng G, 1988, Properties of ultra-thin lubricating films using wedged spacer layer optical interferometry.
This paper describes a method of using optical interferometry to look at films much thinner than the conventional limit of one quarter the wavelength of visible light. A wedge of spacer layer material is sputtered on to the chromium plated glass disc glass disc of an optical elastohydrodynamic, point contact, test rig. As the disc rotates, the spacer layer thickness is constant. From the variation in the position of intereference figures around the circumference of the glass disc, accurate measurements of film thickness below 10nm (1/40th the wavelength of light) have been achieved. This technique is used to test the validity of EHD film thickness relationships down to very low film thickness where the basic assumptions of continuum fluid mechanics become problematical.
Wan GTY, Spikes HA, 1988, The behavior of suspended solid particles in rolling and sliding elastohydrodynamic contacts, Tribology Transactions, Vol: 31, Pages: 12-21, ISSN: 1040-2004
Tiny, dispersed, solid particles are often present in oils, either having been added deliberately as solid lubricants or having been formed during wear. It has been shown that such solids may be beneficial or deleterious, depending upon the nature of the particles and the operating conditions employed. This paper describes a study of the behavior of a range of solid particle suspensions in elastohydrodynamic (EHD) lubrication. The main aim of the work was to gain some insights into the reasons for the varying effects on performance of solid suspended particles in the EHD and mixed EHD-boundary regimes. © 1988 Taylor & Francis Group, LLC.
Spikes HA, 1988, A thermodynamic approach to viscosity.
For use in elastohydrodynamic systems, the ideal lubricant is generally one which forms a thick separating film between the rubbing surfaces over a wide range of operating conditions. This implies a fluid with a high temperature-viscosity coefficient and a low pressure-viscosity coefficient. Unfortunately there is a broad correlation between these two values for liquids. This paper derives and then verifies, using experimental data, an expression for this correlation based upon the assumption that viscosity is a thermodynamic property of state. From the resultant expression, the factors that contribute to a high ratio of pressure- to temperature- viscosity coefficient are identified and discussed by reference to a range of lubricant structures. (from author's abstract)
Cann PME, Johnston GJ, Spikes HA, 1987, FORMATION OF THICK FILMS BY PHOSPHORUS-BASED ANTI-WEAR ADDITIVES., Pages: 543-554, ISSN: 0144-0799
Phosphorus-containing esters are widely used as additives in lubricating oils to reduce wear of rubbing steel surfaces. Recent work has suggested that these additives function by forming a protective layer on the rubbing surfaces, of the order of the surface roughness in thickness. This layer can be a rigid polymeric solid but in some cases appears to be material weakly bonded to the metal surfaces and easily rubbed off. The enhanced viscosity of this material relative to that of bulk oil appears to ensure surface separation by elastohydrodynamic means even at high temperatures where the viscosity of the bulk oil is very low. This paper provides experimental support for the existence of thick anti-wear films for a range of phosphorous esters and discusses their structure, mechanism of formation and practical implications.
BLACK CM, CLARK RP, DARTON K, et al., 1987, A PYROELECTRIC VIDICON THERMOGRAPHIC SYSTEM FOR PHYSIOLOGICAL AND CLINICAL USE, JOURNAL OF PHYSIOLOGY-LONDON, Vol: 384, Pages: P6-P6, ISSN: 0022-3751
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- Citations: 3
Waterhouse C, Johnston GJ, Ewing PD, et al., 1987, The elastohydrodynamic behaviour of simple liquids at low temperatures.
This paper describes a feasibility study into the technique of using very low temperatures to convert simple, low viscosity liquids into lubricants and thus systematically investigate the influence of structure on elastohydrodynamic (EHD) properties. An optical EHD ball on plate rig was modified to study the lubricating properties of simple fluids down to 120DEGREESC. At these temperatures many simple fluids are found to attain the useful viscosity range for lubrication without freezing. Two classes of fluid were studied, the phthalate esters and the alkylbenzenes. Both gave measurable EHD film thicknesses though the alkylbenzenes were effective over a very limited and low temperature range.
Spikes HA, Guangteng G, 1987, Paper XI(i) Properties of ultra-thin lubricating films using wedged spacer layer optical interferometry, Tribology Series, Vol: 12, Pages: 275-279, ISSN: 0167-8922
This paper describes a method of using optical interferometry to look at films much thinner than the conventional limit of one quarter the wavelength of visible light. A wedge of spacer layer material is sputtered on to the chromium-plated glass disc glass disc of an optical elastohydrodynamic, point contact, test rig. As the disc rotates, the spacer layer thickness varies between zero and one wavelength of light whilst the elastohydrodynamic film thickness is constant. From the variation in the position of intereference figures around the circumference Of the glass disc, accurate measurements of film thickness below 10nm (1/40th the wavelength of light) have been achieved. This technique is used to test the valldity of EHD film thickness relationships down t o very low film thickness where the basic assumptions of continuum fluid mechanics become problematical. © 1988, Elsevier B.V. All rights reserved.
Cann PM, Spikes HA, 1987, The influence of lubricant on temperature generated in elasto-hydrodynamic contacts.
Direct measurement of temperatures generated in concentrated contacts by infra-red (IR) radiometry can be used to explore the rheological properties of lubricants under elastohydrodynamic (EHD) conditions. This paper describes the influence of lubricant composition on thermal effects in EHD and attempts to relate rheological characteristics of the fluids to the temperature produced. The lubricants have been chosen to provide a range of rheological and chemical properties. They include synthetic hydrocarbons, polyglycols, perfluorethers, and a traction fluid. An emission technique similar to that employed by Winer and coworkers (1976) has been used to measure the surface temperature distribution within an EHD contact. Significant differences have been found between the surface temperature response of these fluids. The role of lubricant rheology in determining temperature with EHD contacts is discussed together with the implications of such measurement in the study of the traction response of lubricants.
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