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  • Conference paper
    Bovington C, Spikes HA, 1996,

    Prediction of the influence of lubricant formulation on fuel economy, from laboratory bench tests

    , Proceedings of the International Tribology Conference Yokohama, October 1995, Publisher: JST, Pages: 817-822
  • Conference paper
    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
  • Journal article
    Caporiccio G, Cann PME, Spikes HA, 1996,

    Additives for fluorosilicone oils at high temperature

    , Wear, Vol: 193, Pages: 261-268, ISSN: 0043-1648
  • Conference paper
    Smeeth M, Spikes HA, 1996,

    The influence of slide/roll ratio on the film thickness in EHD contact operating in the mixed lubrication regime

    , The Third Body Concept: Interpretation of Tribological Phenomena Proceedings of the 22nd Leeds-Lyon Symposium on Tribology, Lyon France September 5th-8th 1995, Publisher: Elsevier, Pages: 695-703
  • Conference paper
    Cann PME, Hamer JC, Sayles RS, Spikes HA, Ioannides Eet 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
  • Book chapter
    Spikes HA, 1996,

    The rheology of very thin lubricant films

    , Solid-state interactions:proceedings of the first Royal Society-Unilever Indo-UK forum in Materials Science and Engineering, Editors: Adams, Biswas, Briscoe, Publisher: Imperial College Press and Royal Society-Unilever, Pages: 334-351, ISBN: 9781860940101
  • Journal article
    Enthoven J, Spikes HA, 1996,

    Infrared and visual study of the mechanisms of scuffing

    , Tribology Transactions, Vol: 39, Pages: 441-447, ISSN: 0569-8197
  • Conference paper
    Wei DP, Korcek S, Spikes HA, 1996,

    Comparison of the lubricity of gasoline and diesel fuels

    , Gasoline Performance and Deposit Control Additives San Antonio October 1996, Publisher: Society of Automotive Engineers, Pages: 51-60
  • Conference paper
    Cann PME, Hamer JC, Sayles RS, Spikes HA, Ioannides Eet 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
  • Journal article
    Guangteng G, Spikes HA, 1996,

    Fractionation of lubricants at solid surfaces

    , Wear, Vol: 200, Pages: 336-345, ISSN: 0043-1648
  • Journal article
    Marginson HJ, Sayles RS, Olver AV, 1995,

    Limitations of thin film microtransducers in highly loaded contacts

    , TRIBOLOGY INTERNATIONAL, Vol: 28, Pages: 517-521, ISSN: 0301-679X
  • Journal article
    Bovington C, Caprotti R, Meyer K, Spikes HAet 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
  • Journal article
    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.
  • Journal article
    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.
  • Journal article
    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.
  • Journal article
    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.
  • Journal article
    Chevalier F, Lubrecht AA, Cann PME, Colin F, Dalmaz Get al., 1995,

    Starved Film Thickness: A Qualitative Explanation

    , Tribology Series, Vol: 30, Pages: 249-257, ISSN: 0167-8922

    Numerically calculated film thickness can accurately predict measured film thicknesses under fully flooded conditions. However, as more detailed information concerning real life applications becomes available, the validity of the “fully flooded” assumption becomes less tenable. Starved films are much thinner than those formed under fully flooded conditions and it is of great practical importance therefore to be able to predict the ensuing lubrication level. Previous researchers have investigated the relation between the position of the inlet meniscus and starved film thickness. This paper combines a hydrodynamic lubrication approach with a physical boundary condition: the oil inlet film thickness distribution on the surface. Three different cases are investigated; a constant and a harmonic oil inlet film thickness distribution, and the effect of repeated passes. The results are compared qualitatively with experimental observations of starved EHL. © 1995 Elsevier Science B.V.
  • Journal article
    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.
  • Conference paper
    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
  • Journal article
    POON CY, SAYLES RS, 1994,

    CONTACT ANALYSIS OF A SMOOTH BALL ON AN ANISOTROPIC ROUGH-SURFACE

    , JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME, Vol: 116, Pages: 850-859, ISSN: 0742-4787
  • Journal article
    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: 0569-8197
  • Journal article
    CANN P, IOANNIDES E, JACOBSON B, LUBRECHT AAet al., 1994,

    THE LAMBDA RATIO - A CRITICAL REEXAMINATION

    , WEAR, Vol: 175, Pages: 177-188, ISSN: 0043-1648
  • Journal article
    DWYERJOYCE RS, SAYLES RS, IOANNIDES E, 1994,

    AN INVESTIGATION INTO THE MECHANISMS OF CLOSED 3-BODY ABRASIVE WEAR

    , WEAR, Vol: 175, Pages: 133-142, ISSN: 0043-1648
  • Journal article
    POON CY, SAYLES RS, 1994,

    NUMERICAL CONTACT MODEL OF A SMOOTH BALL ON AN ANISOTROPIC ROUGH-SURFACE

    , JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME, Vol: 116, Pages: 194-201, ISSN: 0742-4787
  • Journal article
    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>
  • Journal article
    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.
  • Journal article
    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
  • Journal article
    Aderi ME, Johnsto GJ, Spikes HA, Balson TG, Emery MGet 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>
  • Journal article
    KELSALL GH, ZHU YY, 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
  • Journal article
    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
  • Journal article
    Barker DC, Johnston GJ, Spikes HA, Bünemann TFet al., 1993,

    EHD Film Formation and Starvation of Oil-in-Water Emulsions

    , Tribology Transactions, Vol: 36, Pages: 565-572, ISSN: 1040-2004
  • Journal article
    Enthoven JC, Cann PM, Spikes HA, 1993,

    Temperature and Scuffing

    , Tribology Transactions, Vol: 36, Pages: 258-266, ISSN: 1040-2004
  • Journal article
    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
  • Conference paper
    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
  • Conference paper
    OLVER AV, COLE SJ, SAYLES RS, 1993,

    CONTACT STRESSES IN NITRIDED STEELS

    , 19th Leeds-Lyon Symposium on Tribology: Thin Films in Tribology, Publisher: ELSEVIER SCIENCE PUBL B V, Pages: 71-80
  • Journal article
    POON CY, SAYLES RS, JONES TA, 1992,

    SURFACE MEASUREMENT AND FRACTAL CHARACTERIZATION OF NATURALLY FRACTURED ROCKS

    , JOURNAL OF PHYSICS D-APPLIED PHYSICS, Vol: 25, Pages: 1269-1275, ISSN: 0022-3727
  • Journal article
    ADERIN M, JOHNSTON GJ, SPIKES HA, CAPORICCIO Get al., 1992,

    THE ELASTOHYDRODYNAMIC PROPERTIES OF SOME ADVANCED NONHYDROCARBON-BASED LUBRICANTS

    , LUBRICATION ENGINEERING, Vol: 48, Pages: 633-638, ISSN: 0024-7154
  • Journal article
    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>
  • Journal article
    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
  • Conference paper
    COLE SJ, SAYLES RS, 1992,

    A NUMERICAL-MODEL FOR THE CONTACT OF LAYERED ELASTIC BODIES WITH REAL ROUGH SURFACES

    , Publisher: ASME, Pages: 334-340, ISSN: 0742-4787
  • Journal article
    Guangteng G, Cann PM, Spikes HA, 1992,

    A study of parched lubrication

    , Wear, Vol: 153, Pages: 91-105, ISSN: 0043-1648
  • Conference paper
    POON CY, SAYLES RS, 1992,

    THE CLASSIFICATION OF ROUGH-SURFACE CONTACTS IN RELATION TO TRIBOLOGY

    , Publisher: IOP PUBLISHING LTD, Pages: A249-A256, ISSN: 0022-3727
  • Conference paper
    CANN PM, WILLIAMSON BP, COY RC, SPIKES HAet 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
  • Journal article
    Cann PM, Williamson BP, Coy RC, Spikes HAet 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.
  • Journal article
    BAILEY DM, SAYLES RS, 1991,

    EFFECT OF ROUGHNESS AND SLIDING FRICTION ON CONTACT STRESSES

    , JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME, Vol: 113, Pages: 729-738, ISSN: 0742-4787
  • Journal article
    HAMER JC, SAYLES RS, IOANNIDES E, 1991,

    THE COLLAPSE OF SLIDING MICRO-EHL FILMS BY PLASTIC EXTRUSION

    , JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME, Vol: 113, Pages: 805-810, ISSN: 0742-4787
  • Journal article
    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.
  • Journal article
    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
  • Journal article
    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
  • Journal article
    HAMER JC, SAYLES RS, IOANNIDES E, 1991,

    AN EXPERIMENTAL INVESTIGATION INTO THE BOUNDARIES OF SMEARING FAILURE IN ROLLER-BEARINGS

    , JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME, Vol: 113, Pages: 102-109, ISSN: 0742-4787

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