Publications
472 results found
Cann PME, Hamer JC, Sayles RS, et al., 1996, Direct observation of particle entry and deformation in rolling EHD contact, The third body concept: interpretation of tribological phenomena, proceedings of the 22nd Leeds-Lyon symposium on tribology, Lyon, France September 5-8th, 1995, Publisher: Elsevier, Pages: 127-134
Cann PME, Hutchinson J, Spikes HA, 1996, Development of a space layer imaging method (SLIM) for mapping elastohydrodynamic contacts, Tribology Transactions, Vol: 39, Pages: 915-921, ISSN: 0569-8197
Caporiccio G, Cann PME, Spikes HA, 1996, Additives for fluorosilicone oils at high temperature, Wear, Vol: 193, Pages: 261-268, ISSN: 0043-1648
Guangteng G, Spikes HA, 1996, The role of surface tension and disjoining pressure in starved and parched lubrication, Proceedings of the Institution of Mechanical Engineers Part J-Journal of Engineering Tribology, Vol: 210, Pages: 113-124, ISSN: 1350-6501
Spikes HA, Cann PME, 1996, The thickness and rheology of boundary lubricating layers, Proceedings of the International Tribology Conference Yokohama October 1995, Publisher: JST, Pages: 1089-1094
Zhu YY, Kelsall G, Spikes HA, 1996, Triboelectrochemistry on a nanometre scale, Tribology Letters, Vol: 2, Pages: 287-312, ISSN: 1023-8883
Tripaldi G, Vettor A, Spikes HA, 1996, Friction behaviour of ZDDP films in the mixed boundary/EHD regime, SAE Technical Paper 962036, Publisher: Society of Automotive Engineers, ISSN: 0148-7191
Smeeth M, Gunsel S, Spikes HA, 1996, Boundary film formation by viscosity index improvers, Tribology Transactions, Vol: 39, Pages: 726-734, ISSN: 0569-8197
Palios S, Cann PME, Spikes HA, 1996, Behaviour of PTFE suspensions in rolling/sliding contacts, The Third Body Concepts: Interpretation of Tribological Phenomena Proceedings of the 22nd Leeds/Lyon Symposium on Tribology, Lyon France September 5th-8th 1995, Publisher: Elsevier, ISBN: 9780444825025
Bovington C, Anghel V, Spikes HA, 1996, Predicting sequence VI and VIA fuel economy from laboratory bench tests, SAE Paper 961142, Publisher: Society of Automotive Engineers
Glovnea RP, Spikes HA, 1995, Mapping shear stress in elastohydrodynamic contacts, Tribology Transactions, Vol: 38, Pages: 932-940, ISSN: 1040-2004
A new method has been, devised for investigating the rheological properties of lubricant films in two-dimensional EHD contacts. A lubricated, sliding contact is produced between a sapphire flat and a steel ball. Thermal infrared, emission microscopy is then employed to obtain 2-D maps of the variation of temperature rise due to friction across the contact. These maps are then used in conjunction with moving heal source theory to produce maps of energy dissipation and thus shear strength of the lubricant, film across the contact. A series of mixtures of two lubricants, one giving high traction and one with low traction, have been studied using this technique to investigate the influence of lubricant, blending on shear stress and traction. © 1995 Taylor & Francis Group, LLC.
Enthoven JC, Spikes HA, 1995, Visual Observation of the Process of Scuffing, Tribology Series, Vol: 30, Pages: 487-494, ISSN: 0167-8922
A visual study has been made of the process of scuffing between a lubricated steel ball and a sapphire flat. This has shown that the onset of scuffing is always preceded by the build-up of fine particles of wear debris in the contact inlet which result in starvation and consequently scuffing. Based upon these observations a new mechanism of scuffing is proposed: that scuffing is caused by a critical rate of production of wear debris and its accumulation in the inlet of the lubricated contact. © 1995 Elsevier Science B.V.
Cann PM, Spikes HA, 1995, Visualisation of starved grease and fluid lubricant films, Tribology Series, Vol: 30, Pages: 161-166, ISSN: 0167-8922
Most grease lubricated applications operate under starved conditions as there is usually no mechanism to continually resupply the contact with bulk grease. Consequently the grease is rapidly pushed to the side of the track where it is thought to act as a reservoir supplying oil to the contact (3). Recent work (5) has shown that grease lubricant films measured under such conditions in a rolling contact have two Theologically distinct components; a solid surface film of deposited thickener particles, which is augmented by a hydrodynamically generated film from base oil either in the track or supplied from the grease reservoir. The resulting film thickness represents a balance between increasing bulk starvation, deposition of shear degraded grease thickener within the track and oil replenishment from the grease reservoir. All these effects are time, speed and temperature dependent. It is impossible therefore to predict film thickness from simple rheological properties or from classical elastohydrodynamic theory using the base oil viscosity. These effects have been studied in a series of papers in which grease film thickness has been measured with time and rolling speed for the fully starved condition in a model rolling contact (4)(5)(6). The current paper provides visual evidence for some of the proposed mechanisms by direct observation of the changes in the grease track using spacer layer imaging. © 1995 Elsevier Science B.V.
Bovington C, Caprotti R, Meyer K, et al., 1995, Development of laboratory tests to predict the lubricity properties of diesel fuels and their application to the development of highly refined diesel fuels, Tribotest, Vol: 2, Pages: 93-112, ISSN: 1354-4063
In the last few years there has been an increasing requirement for the provision of environmentally benign diesel fuels. However, the introduction of such fuels into service has been associated with high levels of field failure of rotary distribution fuel pumps due to wear. This is because the refining processes necessary to produce ecologically acceptable fuels result in greatly reduced levels of sulphur compounds, aromatics, and polar material, many of which are potential lubricity agents. This paper describes the development of bench test methods to evaluate diesel fuel lubricity and thus enable the identification of appropriate ‘solutions’. It has been found that the key to obtaining good correlation between field experience and bench tests is (1) to reproduce the thermal conditions present in operating pump contacts and (2) to ensure that the same mechanisms of wear operate in the bench test as in the pump environment. The physical and chemical processes involved in the lubrication of fuel pumps and the influence of temperature on these processes are outlined. As a result of the work described in this paper, effective additive solutions have been discovered for controlling the failure of diesel fuel pumps in the field and a provisional ISO (ISO/TC 22 / SC 7 M595: ‘Diesel engines ‐ diesel fuel ‐ performance requirement and test method for assessing fuel lubricity’) and CEC test method for assessing diesel fuel lubricity has also been developed. Copyright © 1995 John Wiley & Sons, Ltd
Smeeth M, Cann PM, Spikes HA, 1995, Measurement of Elastohydrodynamic Film Formation in Rolling Contacts at Very High Pressures, Tribology Series, Vol: 30, Pages: 497-502, ISSN: 0167-8922
A modified optical interferometry technique was used to measure the EHD central film thickness of two oils up to pressures of 3.6 GPa. In order to generate such pressures a tungsten carbide ball was loaded against a hardened steel disc with a sapphire window insert. The results showed that the film thickness generated was slightly lower than that predicted by the Dowson-Hamrock equation and the load exponent lay between that predicted by Dowson-Hamrock and recent high pressure computed solutions. © 1995 Elsevier Science B.V.
Guangteng G, Spikes HA, 1995, Behaviour of lubricants in the mixed elastohydrodynamic regime, Tribology Series, Vol: 30, Pages: 479-485, ISSN: 0167-8922
A range of lubricant base fluids have been chosen and their film-forming properties measured in the mixed elastohydrodynamic regime in pure rolling conditions. The Dowson-Hamrock elastohydrodynamic film thickness equation was found to remain valid over a large film thickness range for the tested base fluids. For hexadecane, the film thickness equation remains valid down to a film thickness of about 0.5 nm, a size equivalent to a molecular monolayer on each solid surface. However thicker films than predicted by elastohydrodynamic theory were found for all the other tested fluids at low speeds in the very thin film regime. This effect can be interpreted as boundary film formation by the fluids. The origins of these boundary films are still being explored but may be due to adsorption of molecules of the fluid on the solid surfaces and/or enhancement of viscosity due to the presence of a solid surface. This study has shown that full film lubrication is still possible for smooth surfaces in pure rolling in the very thin film regime where the film thickness is far smaller than the composite surface roughness. © 1995 Elsevier Science B.V.
Smeeth M, Spikes H, Gunsel S, 1995, Boundary film formation by viscosity index improvers, STLE/ASME 1995 Tribology Conference, Publisher: SOC TRIBOLOGISTS & LUBRICATION ENGINEERS, Pages: 121-129
Spikes HA, 1994, The Behaviour of Lubricants in Contacts: Current Understanding and Future Possibilities, Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, Vol: 208, Pages: 3-15, ISSN: 1350-6501
<jats:p> The main role of a lubricant is to form a protective, low shear strength film between rubbing surfaces and thereby reduce friction and surface damage. The science, or art, of both the lubricant and the mechanical designer is to develop combinations of lubricant and mechanical system best able to form such films. This task is not straightforward since modern technology is continually demanding lower friction and better protection over an ever-widening range of operating conditions. Furthermore, environmental concerns are also producing both design constraints and the need for rapid change. </jats:p><jats:p> The aim of this paper is to show how progress is being made by experimental research which looks inside rubbing contacts to see how lubricants behave therein. The paper focuses on concentrated contacts, as found in gears, cams and rolling element bearings, and describes a number of techniques for probing such contacts to observe just how a range of lubricant types, from greases to emulsions, behave in such contacts to reduce friction and form films. </jats:p>
Enlhoven JC, Spikes HA, 1994, Temperature Profiling of EHD Contacts prior to and during Scuffing, Tribology Series, Vol: 27, Pages: 73-80, ISSN: 0167-8922
In this paper a novel “nodding mirror” infra-red line scanner is used to study the effect of additives on contact temperatures and hence scuffing in a sliding point contact. The “nodding mirror” line scanner is capable of taking temperature profiles across the contact in a very short time (less than 30 msec). The objective is to capture the temperature history across the contact just prior to and during scuffing using lubricants with and without additives. Tests were carried out in a device consisting of a steel ball loaded and sliding against a stationary sapphire window. The lubricant basestock used in this study was purified hexadecane. This was chosen as it is a simple, low viscosity lubricant that forms a negligible EHD film under the conditions of these tests. This was important as one of the aims was to study boundary additive response to contact temperatures and their effectiveness in postponing or preventing failure. Temperature profiles prior to and during scuffing have been taken in tests with pure hexadecane and with hexadecane containing (i) 1.0 wt% dibenzyldisulfide, an EP additive, and (ii) 0.1 wt% stearic acid, a friction modifier. © 1994, Elsevier Science B.V.
Cann PM, Spikes HA, 1994, The Influence of Base Oil Rheology on the Behaviour of VI Polymers in Concentrated Contacts, Tribology Series, Vol: 27, Pages: 65-72, ISSN: 0167-8922
Whereas elastohydrodynamic (EHD) film thicknesses for simple base stocks can be predicted with some confidence from their bulk properties this is not so for polymer-containing fluids. The behaviour of such fluids in an EHD contact is extremely complex and can include elements of shear thinning, viscoelasticity and boundary properties. In this paper polymer solution behaviour in a concentrated contact has been investigated through detailed EHD film thickness measurements. A series of model polymers; polyisoprenes in the molecular weight range 27-86,000, have been studied in two different basestocks, the intention being to examine the effect of base stock rheology and solvation properties on polymer behaviour. © 1994, Elsevier Science B.V.
Cann PM, Spikes HA, 1994, The Behavior of Polymer Solutions in Concentrated Contacts: Immobile Surface Layer Formation, Tribology Transactions, Vol: 37, Pages: 580-586, ISSN: 1040-2004
Zhu YY, Kelsall GH, Spikes HA, 1994, The Influence of Electrochemical Potentials on the Friction and Wear of Iron and Iron Oxides in Aqueous Systems, Tribology Transactions, Vol: 37, Pages: 811-819, ISSN: 1040-2004
Kelsall GH, Zhu Y, Spikes HA, 1993, Electrochemical effects on friction between metal oxide surfaces in aqueous solutions, Journal of the Chemical Society, Faraday Transactions, Vol: 89, Pages: 267-272, ISSN: 0956-5000
The dependence on potential of the coefficient of friction between metal oxides in aqueous solutions has been investigated experimentally and modelled theoretically in terms of the effect of the electrostatic repulsion between surfaces, the charge on which was controlled by pH and/or electrode potential. The inter-surface pressure, resulting from the sum of van der Waals attraction and double-layer repulsion, was found to be important in determining the friction between metal/metal oxides in aqueous solutions when the applied pressure was < 10 times the electrostatic repulsion pressure acting within the rubbing contact region.
Aderi ME, Johnsto GJ, Spikes HA, et al., 1993, The film‐forming properties of polyalkylene glycols, Journal of Synthetic Lubrication, Vol: 10, Pages: 23-45, ISSN: 0265-6582
<jats:title>Abstract</jats:title><jats:p>It is now recognised that, for many practical applications, an important property of a lubricant is its ability to generate thick, elastohydrodynamic (EHD) films in concentrated contacts. This paper describes a study of the EHD film‐ forming properties of polyalkylenie glycol lubricants. A wide range of polyglycol structures have been examined, with different monomer types, initiators, and molecular weights. Film thickness has been measured at several different temperatures using both conventional and ultra‐thin film interferometry. From the measured film thicknesses, the effective pressure–viscosity coefficients of the lubricants have been evaluated. This has enabled a systematic investigation of the effect of polyalkylene glycol structure on both pressure–viscosity coefficient and EHD film formation.</jats:p>
Chang HS, Wayte R, Spikes HA, 1993, Measurement of Piston Ring and Land Temperatures in a Firing Engine Using Infrared, Tribology Transactions, Vol: 36, Pages: 104-112, ISSN: 1040-2004
Barker DC, Johnston GJ, Spikes HA, et al., 1993, EHD Film Formation and Starvation of Oil-in-Water Emulsions, Tribology Transactions, Vol: 36, Pages: 565-572, ISSN: 1040-2004
Enthoven JC, Cann PM, Spikes HA, 1993, Temperature and Scuffing, Tribology Transactions, Vol: 36, Pages: 258-266, ISSN: 1040-2004
Gunsel S, Spikes HA, Aderin M, 1993, In-Situ Measurement of ZDDP Films in Concentrated Contacts, Tribology Transactions, Vol: 36, Pages: 276-282, ISSN: 1040-2004
SPIKES HA, 1993, BOUNDARY LUBRICATION AND BOUNDARY FILMS, 19th Leeds-Lyon Symposium on Tribology: Thin Films in Tribology, Publisher: ELSEVIER SCIENCE PUBL B V, Pages: 331-346
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- Citations: 36
ADERIN M, JOHNSTON GJ, SPIKES HA, et al., 1992, THE ELASTOHYDRODYNAMIC PROPERTIES OF SOME ADVANCED NONHYDROCARBON-BASED LUBRICANTS, LUBRICATION ENGINEERING, Vol: 48, Pages: 633-638, ISSN: 0024-7154
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- Citations: 25
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