Publications
472 results found
Spikes HA, 1987, Wear and fatigue problems in connection with water‐based hydraulic fluids, Journal of Synthetic Lubrication, Vol: 4, Pages: 115-135, ISSN: 0265-6582
Water‐containing fluids are widely used in hydraulic applications where there is a significant risk of fire, as in underground mining and metal working applications. Although primarily intended as power transmitting media, hydraulic fluids need to possess a modicum of lubricating ability to limit wear, seizure and contact fatigue of pumps and other rubbing parts. Unfortunately water‐based hydraulic fluids generally show significantly poorer wear and rolling‐contact fatigue performance than mineral or synthetic oil‐based fluids of similar viscosity and this means that pumping equipment usually has to be derated when used with water‐based fluids. This paper examines the poor wear and fatigue performance of water‐based fluids and discusses, in some detail, the origins of this poor performance and the ways it can be mitigated. Copyright © 1987 John Wiley & Sons, Ltd
Cann PME, Johnston GJ, Spikes HA, 1987, The formation of thick films by phosphorous-based anti-wear additives., IN: PROC. IMECHE INT. CONF. ON TRIBOLOGY - FRICTION, LUBRICATION AND WEAR, FIFTY YEARS ON, (LONDON, U.K.: JUL. 1-3, 1987), Vol: I, Bury St Edmunds, U.K., Mech. Engng. Publications Ltd., 1987, Paper C208/87, Pages: 543-554
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 antiwear films for a range of phosphorous esters and discusses their structure, mechanism of formation and practical implications. (A)
Cann PM, Spikes HA, 1987, The influence of lubricant on temperature generated in elasto-hydrodynamic contacts., Tribology Series, Vol: 12, Pages: 183-192, ISSN: 0167-8922
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.
Wan GTY, Spikes HA, 1987, The behavior of suspended solid particles in rolling and sliding elastohydrodynamic contacts.
This paper describes a study of the behaviour of a range of solid particle suspensions in elastohydrodynamic 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 elastohydrodynamic and mixed elastohydrodynamic/boundary regimes. (from authors' abstract)
Waterhouse C, Johnston GJ, Ewing PD, et al., 1987, Paper VIII(iv) The elastohydrodynamic behaviour of simple liquids at low temperatures, Tribology Series, Vol: 11, Pages: 267-275, ISSN: 0167-8922
The relationship between molecular structure and elastohydrodynamic rheological properties of lubricants is only poorly understood. One reason for this is that normal liquid lubricants, such as mineral oils and esters, enerally have complex multi-atom molecular structures and are also often mixtures. It is thus difficult to correlate EHD performance with structural details. 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 has been modified to study the lubricating properties of simple fluids down to −120°C. At these temperatures many simple fluids are found to attain the useful viscosity range for lubrication without freezing. Two classes of fluid have been 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. © 1987, Elsevier B.V. All rights reserved.
Spikes HA, 1986, HELICOPTER LUBRICATION., Pages: 59-74
Helicopter systems, and in particular helicopter transmissions, pose severe problems of lubrication and these are reflected in shorter overhaul periods and lower reliability than other, comparable systems in fixed wing aircraft. Many of these problems may be met by the introduction of new materials, such as ceramic engine bearings, flexible rotor parts, new gear steels and synthetic transmission oils. One stumbling block should, however be recognised. Helicopters, though important and irreplaceable for some applications, are not produced in large numbers and the cost of applying new technology can be prohibitive if a significant amount of development work needs to be done. Even the validation of a new material is enormously expensive, involving as it must, helicopter flying time. It is these costs, rather than the merits or availability of new materials and technologies that may be the main barrier to improvements in helicopter lubrication.
Spikes HA, Olver AV, Macpherson PB, 1986, Wear in rolling contacts, Wear, Vol: 112, Pages: 121-144, ISSN: 0043-1648
Danping W, Spikes HA, 1986, The lubricity of diesel fuels, Wear, Vol: 111, Pages: 217-235, ISSN: 0043-1648
Spikes HA, 1986, Future helicopter transmission oils, Journal of Synthetic Lubrication, Vol: 3, Pages: 181-208, ISSN: 0265-6582
<jats:title>Abstract</jats:title><jats:p>For many years helicopter transmissions have shown low reliability relative to planned overhaul lives and to other comparable lubricated systems. Reasons for this include the extremely wide range of conditions encountered by the lubricant in helicopter transmissions and also the requirement that, in many cases, the oil be common to both transmission and gas turbine engines.</jats:p><jats:p>Recently acquired understanding of lubrication mechanisms shows that potential exists both for improved performance and for the ability to cater for higher temperatures by the development of new helicopter transmission oils based on synthetic lubricants.</jats:p><jats:p>This paper discusses the particular lubricating problems associated with helicopter transmission lubrication and describes test methods and formulation approaches to improving such lubricants.</jats:p>
Johnston G, Cann PME, Spikes HA, 1986, A new mechanism for gear and bearing anti-wear additive behaviour., IN: 5TH INT. COLLOQUIUM ON ADDITIVES FOR LUBRICANTS AND OPERATIONAL FLUIDS, (OSTFILDERN, FED. REP. GERMANY: JAN. 14-16, 1986), Vol: 1 , Ostfildern, Fed. Rep. Germany, Esslingen Tech. Akad., 1986, Session 3, Paper 3.12, p.3.12-1-3.12-1
Work was carried out to examine the formation of thick films on rubbed metal surfaces by phosphorous containing antiwear additives. These investigations provide ample evidence that films over a hundred nanometers thick can form on surfaces from ZDDP and phosphonate ester solutions and separate surfaces by this amount in rolling and sliding conditions. (from paper)
Wan GTY, Spikes HA, 1986, Two phase lubricants in elastohydrodynamic contacts - graphite in oil dispersions.
Low shear strength lamellar solids, such as graphite and molybdenum disulphide, have been added to mineral oils and greases for many years in an attempt to reduce friction and wear. There is, however, very little known about what factors influence the performance of these solid lubricants in oil, and whether the solid particles enter rolling and sliding elastohydrodynamic contacts, such as are found in gears and rolling bearings. This study reports on the behaviour of suspended particles of graphite in oils in a dynamic loaded point contact using optical interferometry. It was found that the nature and concentration of solid lubricant play a significant role in the formation of elastohydrodynamic lubricant films. 'Polar' graphite particles in oils were readily 'plated out' in the contact to form an adherent solid lubricant film. By contrast 'oleophilic' graphite in oils was observed to enter the contact, resulting in a thicker fluid film. Discussion of this paper is included on p.284. (A)
Wan GTY, Spikes HA, 1986, Two phase lubricants in elastohydrodynamic contacts - graphite in oil dispersions.
Low shear strength lamellar solids, such as graphite and molybdenum disulphide, have been added to mineral oils and greases for many years in an attempt to reduce friction and wear. There is, however, very little known about what factors influence the performance of these solid lubricants in oil, and whether the solid particles enter rolling and sliding elastohydrodynamic contacts, such as are found in gears and rolling bearings. This study reports on the behaviour of suspended particles of graphite in oils in a dynamic loaded point contact using optical interferometry. It was found that the nature and concentration of solid lubricant play a significant role in the formation of elastohydrodynamic lubricant films. 'Polar' graphite particles in oils were readily 'plated out' in the contact to form an adherent solid lubricant film. By contrast 'oleophilic' graphite in oils was observed to enter the contact, resulting in a thicker fluid film. Discussion of this paper is included on p.284. (A)
Spikes HA, 1986, Wear and fatigue problems in connection with water-based fluids.
This paper examines the poor wear and fatigue performance of water based fluids and discusses the origins of this poor performance and the ways it can be mitigated. The main mechanisms for the high wear and short fatigue lives of water based hydraulic fluids are said to be the low elastohydrodynamic lubrication film thickness and thus low specific film thickness produced by these fluids and the specific chemical effects of water in initiating fatigue cracks by corrosion fatigue and propagating them by hydrogen embrittlement. (from paper)
Spikes HA, 1986, Future trends in helicopter transmission lubricants.
Some recent fundamental studies relating to the lubrication of helicopter transmissions are presented and their implications for future oil development discussed. The resulting enhanced understanding of lubrication mechanisms has shown that real potential exists both for improved performance and for the ability to cater for higher temperatures, by means of the formulation and use of improved transmission oils. If such benefits are recognized and if the new knowledge is correctly applied, there is no reason why helicopter gearbox reliability should not be appreciably improved by the end of the decade. (A)
Johnston G, Cann PM, Spikes HA, 1986, Phosphorus anti-wear additives: thick film formation and its influence on surface distress.
It has recently been shown, using optical interferometry, that phosphonate ester antiwear additives form thick polymeric films in rolling elastohydrodynamic contacts. This paper uses interferometric and electrical contact resistance techniques to demonstrate that similar films develop in contacts under conditions of sliding, and, initially, boundary lubrication. Discussion of this paper is included on p.157-158. (A)
Lacey IN, Kelsall GH, Spikes HA, et al., 1986, Thick Antiwear Films in Elastohydrodynamic Contacts. Part I: Film Growth in Rolling/Sliding EHD Contacts, A S L E Transactions, Vol: 29, Pages: 299-305, ISSN: 0569-8197
Olver AV, Spikes HA, Bower AF, et al., 1986, The residual stress distribution in a plastically deformed model asperity, Wear, Vol: 107, Pages: 151-174, ISSN: 0043-1648
Lacey IN, Kelsall GH, Spikes HA, et al., 1986, Thick Antiwear Films in Elastohydrodynamic Contacts. Part II: Chemical Nature of the Deposited Films, A S L E Transactions, Vol: 29, Pages: 306-311, ISSN: 0569-8197
Lacey IN, Spikes HA, Macpherson PB, 1985, Phosphorus anti-wear additives in helicopter transmissions.
This report describes a study into the mechanism of action of one class of phosphurus antiwear additives, the phosphonate esters. It is shown that these additives form thick, polymeric films on rolling and rolling/sliding steel surfaces, and these films are able to greatly increase surface separation above that produced by normal elastohydrodynamic lubrication. (A)
Olver AV, Spikes HA, MacPherson PB, 1985, WEAR IN ROLLING CONTACTS., Pages: 254-272, ISSN: 0192-4990
Unexpectedly high, uniform rates of wear occur from time to time in concentrated, lubricated, rolling contacts having low slide-roll ratios. Such wear can occur under quite mild conditions and this poses a significant practical problem, especially in gears. This phenomenon of high wear rate at low slide-roll ratio has been reproduced consistently and studied in the laboratory using a disc machine. The outcome of this study is reported. It is shown that the wear is caused by plastic deformation, fatigue cracking, ductile extrusion and fracture on a scale associated with asperity contact.
Spikes HA, Cann P, Caporiccio G, 1984, Elastohydrodynamic film thickness measurements of perfluoropolyether fluids, Journal of Synthetic Lubrication, Vol: 1, Pages: 73-86, ISSN: 0265-6582
Wan GTY, Kenny P, Spikes HA, 1984, Elastohydrodynamic properties of water-based fire-resistant hydraulic fluids, Tribology International, Vol: 17, Pages: 309-315, ISSN: 0301-679X
The elastohydrodynamic (ehd) lubricating properties of commercial fire-resistant hydraulic fluids in rolling point contacts are described. Earlier work is reviewed and new work presented on water-in-oil and oil-in-water emulsions. It is shown that in general, elastohydrodynamic film thicknesses of water-in-oil emulsions are close to those of their base oils. For very fine particle size emulsions, however, thicker films are observed. Commercial oil-in-water emulsions in fully flooded conditions have not been found to give measurable elastohydrodynamic films. However, when the emulsions are destabilized, a localized pool of oil collects in the contact zone which enables ehd films to form, though these films do not survive very high rolling speeds. Polyglycol solutions give low ehd film thicknesses, approximately one third those of mineral oils of corresponding viscosity. This can be attributed to the low pressure-viscosity coefficient of these solutions. © 1984.
Spikes HA, Margetts RG, 1984, Lubrication of wire rope: single contact testing.
The objective of the research programme was to improve the design of wire ropes using procedures similar to those used for other structural members. Chapters are included on hydrodynamics, dynamic behaviour, effects of external loads, elastic properties of large strands, fatigue strength, electrochemical protection, nitrocarburising, corrosion fatigue, fretting corrosion, lubrication, load and acoustic emission, service life, defects and effects caused by seawater. (H.C.B.)
Cann P, Spikes H, 1984, Determination of oil films on lubricated surfaces.
It is often important in tribology to be able to determine the thickness of lubricant on surfaces before and after rubbing. This paper describes a method of measuring oil film thickness in the range 20-1000 nm using reflection infrared spectroscopy. Results for some practical applications are included and their implications are discussed. (A)
Wan GTY, Spikes HA, 1984, The elastohydrodynamic lubricating properties of water-polyglycol fire-resistant fluids, ASLE Transactions, Vol: 27, Pages: 366-372, ISSN: 0569-8197
Commercial aqueous polyglycol hydraulic fluids are found to give very low elastohydrodynamic film thicknesses. By studying mixtures of polyglycol, monoglycol, and water, it is shown that this is became the pressure-viscosity coefficients of polyglycol and monoglycol fall very sharply when they are mixed together or when water is added. Over the polyglycol, monoglycol, water mixture range, pressure-viscosity coefficient appears to be inversely related to free volume. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Hartford, Connecticut, October 18–20, 1983. © 1984 Taylor & Francis Group, LLC.
Spikes HA, Cann P, Caporiccio G, 1984, Elastohydrodynamic film thickness measurements of perfluoropolyether fluids.
The EHD film thickness properties of various perfluoropolyether lubricants were measured using optical interferometry. From these results, calculated pressure/viscosity coefficients were calculated. Perfluorinated polyethers derived from hexafluoropropene have high pressure/viscosity coefficients, in the range 28-36 GPa SUP - SUP 1. Perfluorinated polyethers derived from tetrafluroethane have lower pressure viscosity coefficients, in the range 4-12 GPa SUP - SUP 1. (from paper)
Cann P, Spikes H, 1984, DETERMINATION OF OIL FILMS ON LUBRICATED SURFACES., Pages: 79-82
It is often important in Tribology to be able to determine the thickness of lubricant on surfaces before and after rubbing. This paper describes a method of measuring oil film thickness in the range 20-1000nm using reflection infrared spectroscopy. Results for some practical applications are included and their implications are discussed.
Spikes HA, 1984, Helicopter transmission lubricants.
This paper outlines problems associated with the lubrication of helicopter transmissions and then discusses how helicopter lubricants are likely to change over the next decade. For many years, helicopter transmission reliability has suffered both in the U.K. and the U.S.A. from the requirement that the oil is common to both the transmission and the gas turbine. In practice, certainly in the U.K., most helicopters do not use a common oil. The U.K. helicopter industry is in sympathy with the logistic advantages of minimizing the number of oils stocked but feels that this could be more successfully achieved by adopting a single transmission oil for all NATO helicopters. It now appears that this is being considered as a practical alternative. In the U.K., the Ministry of Defence has funded the successful development of a helicopter transmission oil in anticipation of such a move. The U.S.A. is about to embark on a relevant oil development programme. Another likely change is the move towards a higher temperature transmission oil, as the amount of external cooling is progressively removed. The British helicopter industry is engaged in developing new oils to meet this requirement. (A)
Cann P, Spikes HA, Caporiccio G, 1984, Spreading of perfluorinated fluids on metal surfaces.
Of the theoretical models reviewed the kinetic analysis of Lopez, Miller and Ruckstein would appear to offer a satisfactory model for the spreading of perfluropolyether lubricants and silicones. The spreading of drops in the 'gravity-viscous' regime was monitored and the results are in reasonable agreement with theoretical predictions. Spreading gradients of 0.097-0.2 were measured compared to a theoretical slope of 0.125. The slope was also found to be invariant with drop volume, but not with fluid viscosity. The second result is contrary to prediction, and may result from an intermolecular force contribution to spreading. Support for the theory that drops can experience successive regimes of spreading is provided by the observation that the spreading gradient of some low viscosity fluids increase as spreading proceeeds. The formation of a ridge near the spreading edge was also observed. This was considered to be due to the predominance of intermolecular forces. Tests on an experimental fluid show that minor modifications in composition can lead to a great increase of spreading rates. (from paper)
Margetts B, Spikes HA, 1983, Single contact testing and the lubrication of wire ropes.
The importance of effective lubrication of wire ropes is discussed. The extent to which laboratory testing can simulate the relevant wear processes and provide information about lubricant performance is considered and the effects of variations in contact angle, load, displacement amplitude and frequency are described. Results of friction and wear tests are presented to demonstrate the interaction of the factors such as the wire surface material, degree of corrosion and lubricant type. (A)
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