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  • Conference paper
    Hartinger M, Gosman D, Ioannides S, Spikes Het al., 2008,

    Thermal effects in an elastohydrodynamic line contact using a CFD approach

    , ASME/STLE International Joint Tribology Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 179-180
  • Journal article
    Reddyhoff T, Dwyer-Joyce RS, Zhang J, Drinkwater BWet al., 2008,

    Auto-calibration of ultrasonic lubricant-film thickness measurements

    , Measurement Science and Technology, Vol: 19, ISSN: 0957-0233

    The measurement of oil film thickness in a lubricated component is essential information for performance monitoring and design. It is well established that such measurements can be made ultrasonically if the lubricant film is modelled as a collection of small springs. The ultrasonic method requires that component faces are separated and a reference reflection recorded in order to obtain a reflection coefficient value from which film thickness is calculated. The novel and practically useful approach put forward in this paper and validated experimentally allows reflection coefficient measurement without the requirement for a reference. This involves simultaneously measuring the amplitude and phase of an ultrasonic pulse reflected from a layer. Provided that the acoustic properties of the substrate are known, the theoretical relationship between the two can be fitted to the data in order to yield reflection coefficient amplitude and phase for an infinitely thick layer. This is equivalent to measuring a reference signal directly, but importantly does not require the materials to be separated. The further valuable aspect of this approach, which is demonstrated experimentally, is its ability to be used as a self-calibrating routine, inherently compensating for temperature effects. This is due to the relationship between the amplitude and phase being unaffected by changes in temperature which cause unwanted changes to the incident pulse. Finally, error analysis is performed showing how the accuracy of the results can be optimized. A finding of particular significance is the strong dependence of the accuracy of the technique on the amplitude of reflection coefficient input data used. This places some limitations on the applicability of the technique. 2008 IOP Publishing Ltd.
  • Conference paper
    Topolovec-Miklozic K, Forbus TR, Lockwood F, Spikes Het al., 2008,

    Behaviour of boundary lubricating additives on DLC coatings

    , ASME/STLE International Joint Tribology Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 141-143
  • Conference paper
    Korsunsky AM, Dini D, Walsh MJ, 2008,

    Fatigue crack growth rate analysis in a titanium alloy

    , 7th International Conference on Fracture and Damage Mechanics, Publisher: TRANS TECH PUBLICATIONS LTD, Pages: 5-+, ISSN: 1013-9826
  • Journal article
    Wong JSS, Granick S, 2007,

    Open questions about polymer friction

    , Journal of Polymer Science. Part B, Polymer Physics, Vol: 45
  • Journal article
    Song X, Zhang SY, Dini D, Korsunsky AMet al., 2007,

    Microscopic energy dissipation and fatigue crack initiation in polycrystalline metallic alloys

    , Computational Plasticity - Fundamentals and Applications, COMPLAS IX, Pages: 709-712

    In this paper we propose an energy-based criterion for life-prediction of fatigue crack initiation via a 3D, elastically anisotropic FE model for cyclic deformation and hardening of face-centred cubic (FCC) materials. © CIMNE, 2007.
  • Journal article
    Zhang SY, Song X, Dini D, Korsunsky AMet al., 2007,

    Formulation and calibration of a crystal plasticity finite element model for HCP polycrystals

    , Computational Plasticity - Fundamentals and Applications, COMPLAS IX, Pages: 639-642
  • Journal article
    Olver AV, Dini D, Lainé E, Beveridge TA, Hua DYet al., 2007,

    Roughness and lubricant chemistry effects in micropitting

    , American Gear Manufacturers Association - Fall Technical Meeting of the American Gear Manufacturers Association 2007, AGMA, Pages: 151-160

    Micropitting has been studied using a disc machine in which a central carburised steel test roller contacts three, harder, counter-rollers ("rings") with closely controlled roughness. We varied the roughness using different finishing techniques and investigated the effects of different oil base-stocks and additives, whilst keeping the viscosity approximately constant. We also developed a predictive model for the approximate analysis of rough-surface elastohydrodynamic lubrication based on the FFT approach of Hooke. Damage on the test rollers included dense micropitting and "micropitting erosion" in which tens of microns of the test surface were completely removed. This phenomenon is particularly damaging in gear teeth where it has the potential to destroy profile accuracy. It was found that anti-wear additives led to a high rate of micropitting erosion and that the effect correlated more or less inversely with simple sliding wear results. There were also appreciable effects from base-stock chemistry. The key parameter affecting the severity of damage seemed to be the near-surface shear stress amplitude arising from the evolved roughness; different chemistries led to the evolution of different roughness during initial running and thence to different contact stresses and different levels of damage. © AGMA 2007 - All rights reserved.
  • Journal article
    Fan J, Mueller M, Stoehr T, Spikes HAet al., 2007,

    Reduction of friction by functionalised viscosity index improvers

    , TRIBOLOGY LETTERS, Vol: 28, Pages: 287-298, ISSN: 1023-8883
  • Journal article
    Müller M, Fan J, Spikes H, 2007,

    Design of functionalized PAMA viscosity modifiers to reduce friction and wear in lubricating oils

    , Journal of ASTM International, Vol: 4, Pages: 116-125, ISSN: 0066-0558

    Polyalkylmethacrylates (PAMAs) are widely used as both viscosity index improvers and dispersant boosters in engine, hydraulic, and transmission oils. Since they are employed in a relatively high concentration in these roles, it is desirable that they be able to enhance other characteristics of a lubricant and, in particular, its boundary lubricating properties. A series of functionalized PAMAs have been synthesized that can adsorb from oil solution onto rubbing surfaces to produce thick boundary films. These films enhance lubricant film formation in slow speed and high temperature conditions and thus make a significant contribution to their lubricating ability. The current paper describes a systematic study of the influence of functionallzed PAMAs on boundary lubrication performance. The high frequency reciprocating test rig (HFRR) was applied to investigate friction and wear under pure sliding. A new test method has been developed which allows wear to be monitored in a rolling and sliding contact based on the mini traction machine (MTM). This, in combination with other tests, is employed to investigate the influence of polymer architecture, functionality, concentration and molecular weight on friction and wear in a range of lubricant formulations. This enables the tailored design of polymers which offer low friction and wear properties. Copyright © 2007 by ASTM International.
  • Journal article
    Olver AV, Dini D, 2007,

    Roughness in lubricated rolling contact: the dry contact limit

    , P I MECH ENG J-J ENG, Vol: 221, Pages: 787-791, ISSN: 1350-6501

    A difficulty with the standard fast Fourier transform (FFT) perturbation model of roughness in lubricated rolling contacts is that it does not necessarily converge towards the elastic case as the film thickness is reduced; rather it leads to a situation in which all the roughness is completely flattened. This is rarely the case for real engineering surfaces.Here, it is shown that this difficulty can be avoided by carrying out a Fourier transform of the elastostatically flattened roughness and using the resulting (complex) amplitude as the low-film thickness limit of each Fourier component in the elastohydrodynamic lubrication (EHL) analysis.Results give a plausible convergence to the elastostatic solution, which is nevertheless consistent with the expected near-full-film EHL behaviour and which becomes identical to the earlier model for roughness that, statically, can be fully flattened. As expected, hydrodynamic action persists at the finest scale, even for very thin films.
  • Conference paper
    Müller M, Bartels T, Hedrich K, Wincierz C, Spikes Het al., 2007,

    Tailor-made polyalkylmethacrylate additives to meet the stringent requirements of current and future generations of engine, transmission, gear and hydraulic oils

    A discussion covers an introduction into polyalkylmethacrylates (PAMA) and their chemistry; viscometric and tribological effects of PAMA in lubricant formulations; recent findings from a scientific study of EHD film formation, friction and wear reduction through specifically designed PAMA; results of various performance and application tests demonstrating the effect of PAMA on different performance aspects of modern lubricants; wear reduction and fuel economy engine oils, including pitting performance, operating temperature control, and energy efficiency in transmission and gear oils; and the effect of PAMA on hydraulic pump efficiency and delivered hydraulic work in different performance and field tests. This is an abstract of a paper presented at the 13th Annual Fuels and Lubes Asia Conference (Bangkok, Thailand 3/7-9/2007).
  • Journal article
    Chapkov AD, Bair S, Cann P, Lubrecht AAet al., 2007,

    Film thickness in point contacts under generalized Newtonian EHL conditions: Numerical and experimental analysis

    , TRIBOLOGY INTERNATIONAL, Vol: 40, Pages: 1474-1478, ISSN: 0301-679X
  • Journal article
    Olver AV, Wilson D, Crofton PSJ, 2007,

    Investigation of service failures of steel music wire

    , Engineering Failure Analysis, Vol: 14, Pages: 1224-1232, ISSN: 1350-6307
  • Journal article
    Cann PME, Stack MM, 2007,

    A celebration of 25 years of the Tribology Group: from tribo-physics to tribo-chemistry

    , JOURNAL OF PHYSICS D-APPLIED PHYSICS, Vol: 40, ISSN: 0022-3727
  • Journal article
    Cann PME, Lubrecht AA, 2007,

    Bearing performance limits with grease lubrication: the interaction of bearing design, operating conditions and grease properties

    , JOURNAL OF PHYSICS D-APPLIED PHYSICS, Vol: 40, Pages: 5446-5451, ISSN: 0022-3727
  • Conference paper
    Korsunsky AM, Dini D, Dunne FPE, Walsh MJet al., 2007,

    Comparative assessment of dissipated energy and other fatigue criteria

    , 6th International Conference on Fatique Damage of Structural Materials, Publisher: ELSEVIER SCI LTD, Pages: 1990-1995, ISSN: 0142-1123
  • Journal article
    Nikas GK, Burridge G, Sayles RS, 2007,

    Modelling and optimization of rotary vane seals

    , PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY, Vol: 221, Pages: 699-715, ISSN: 1350-6501
  • Journal article
    Choo J-H, Forrest AK, Spikes HA, 2007,

    Influence of organic friction modifier on liquid slip: A new mechanism of organic friction modifier action

    , TRIBOLOGY LETTERS, Vol: 27, Pages: 239-244, ISSN: 1023-8883
  • Journal article
    Cann PM, 2007,

    Grease lubrication of rolling element bearings - Role of the grease thickener

    , Lubrication Science, Vol: 19, Pages: 183-196, ISSN: 0954-0075

    The contribution of grease thickener to lubricant film formation was examined in this paper. Lubricant film thickness and friction were measured for different grease thickener types in a bearing simulation device. The results showed that the greases formed thick (20-80 nm), low friction surface layers at low speeds, which were much greater than the corresponding base oil film. These films appeared to be formed by the physical deposition of thickener in the track during overrolling of the grease. This was confirmed by infrared reflection analysis, which showed the deposited films to have increased thickener content. The ability of grease to form renewable physically deposited solid films has significant implications for optimising lubricant formulation for certain applications, e.g. bearings operating at high temperatures and low speeds where a conventional elastohydrodynamic lubricating film would be inadequate. Copyright © 2007 John Wiley & Sons, Ltd.
  • Journal article
    Qiu H, Hills DA, Dini D, 2007,

    The influence function for self-equilibrating forces on a semi-infinite wedge

    , JOURNAL OF STRAIN ANALYSIS FOR ENGINEERING DESIGN, Vol: 42, Pages: 351-359, ISSN: 0309-3247
  • Journal article
    Choo JH, Glovnea RP, Forrest AK, Spikes HAet al., 2007,

    A low friction bearing based on liquid slip at the wall

    , JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME, Vol: 129, Pages: 611-620, ISSN: 0742-4787
  • Journal article
    Fan J, Spikes H, 2007,

    New test for mild lubricated wear in rolling-sliding contacts

    , TRIBOLOGY & LUBRICATION TECHNOLOGY, Vol: 63, Pages: 36-45, ISSN: 1545-858X
  • Conference paper
    Dini D, Hills DA, 2007,

    Frictional Energy Dissipation In A Rough Hertzian Contact (MCMAT2007-30565)

    , ASME Applied Mechanics and Materials Conference
  • Journal article
    Karuppanan S, Dini D, Hills DA, 2007,

    Fretting fatigue test analysis of contact

    , FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES, Vol: 30, Pages: 499-509, ISSN: 8756-758X
  • Journal article
    Sackfield A, Dini D, Hills DA, 2007,

    Contact of a rotating wheel with a flat

    , INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, Vol: 44, Pages: 3304-3316, ISSN: 0020-7683
  • Journal article
    Topolovec-Miklozic K, Forbus TR, Spikes HA, 2007,

    Film thickness and roughness of ZDDP antiwear films

    , TRIBOLOGY LETTERS, Vol: 26, Pages: 161-171, ISSN: 1023-8883
  • Journal article
    Cann PM, Webster MN, Doner JP, Wikstrom V, Lugt Pet al., 2007,

    Grease degradation in R0F bearing tests

    , TRIBOLOGY TRANSACTIONS, Vol: 50, Pages: 187-197, ISSN: 1040-2004
  • Journal article
    Fan J, Spikes H, 2007,

    New test for mild lubricated wear in rolling-sliding contacts

    , TRIBOLOGY TRANSACTIONS, Vol: 50, Pages: 145-153, ISSN: 1040-2004
  • Journal article
    Fowell M, Olver AV, Gosman AD, Spikes HA, Pegg Iet al., 2007,

    Entrainment and inlet suction: Two mechanisms of hydrodynamic lubrication in textured bearings

    , JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME, Vol: 129, Pages: 336-347, ISSN: 0742-4787
  • Journal article
    Duo P, Liu J, Dini D, Golshan M, Korsunsky AMet al., 2007,

    Evaluation and analysis of residual stresses due to foreign object damage

    , MECHANICS OF MATERIALS, Vol: 39, Pages: 199-211, ISSN: 0167-6636
  • Journal article
    Xu X, Spikes H, 2007,

    Study of zinc dialkyldithiophosphate in di-ethylhexyl sebacate using electrochemical techniques

    , TRIBOLOGY LETTERS, Vol: 25, Pages: 141-148, ISSN: 1023-8883
  • Journal article
    Choo JW, Olver AV, Spikes HA, 2007,

    The influence of transverse roughness in thin film, mixed elastohydrodynamic lubrication

    , TRIBOLOGY INTERNATIONAL, Vol: 40, Pages: 220-232, ISSN: 0301-679X
  • Journal article
    Choo JH, Spikes HA, Ratoi M, Glovnea R, Forrest Aet al., 2007,

    Friction reduction in low-load hydrodynamic lubrication with a hydrophobic surface

    , TRIBOLOGY INTERNATIONAL, Vol: 40, Pages: 154-159, ISSN: 0301-679X
  • Journal article
    Masen MA, De Rooij MB, Schipper DJ, Adachi K, Kato Ket al., 2007,

    Single asperity abrasion of coated nodular cast iron

    , TRIBOLOGY INTERNATIONAL, Vol: 40, Pages: 170-179, ISSN: 0301-679X
  • Journal article
    Müller M, Fan J, Spikes H, 2007,

    Influence of polymethacrylate viscosity index improvers on friction and wear of lubricant formulations

    , SAE Technical Papers, ISSN: 0148-7191

    Polyalkylmethacrylates (PAMAs) are widely used as viscosity index improvers and dispersant boosters in engine, transmission and hydraulic oils. They have been shown to be 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 of friction and wear. In a recent systematic study a range of dispersant and non-dispersant PAMAs has been synthesized. The influence of different functionalities, molecular weights and architectures 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. In the current paper the film forming, friction and wear properties of solutions of two functionalised PAMAs is first described. Then the impact of different lubricant additives on these friction and wear properties is explored. A number of components from all major classes of additives commonly used in commercial DI packages have been investigated. The results help the performance of PAMAs in fully formulated oils to be predicted and thus their design to be optimized.
  • Journal article
    Vorster WJJ, Zhang SY, Golshan M, Laundy D, Dini D, Korsunsky AMet al., 2007,

    Comparison of X-ray diffraction measurement of residual elastic strains: monochromatic beam and image plate versus white beam energy-dispersive analysis

    , JOURNAL OF STRAIN ANALYSIS FOR ENGINEERING DESIGN, Vol: 42, Pages: 23-37, ISSN: 0309-3247
  • Conference paper
    Korsunsky AM, Song X, Belnoue J, Prakash LDG, Dini D, Walsh MJet al., 2007,

    Modeling crack initiation and propagation in nickel base superalloys

    , 6th International Conference on Fracture and Damage Mechanics, Publisher: TRANS TECH PUBLICATIONS LTD, Pages: 53-+, ISSN: 1013-9826
  • Journal article
    Jeffers JRT, Browne M, Lennon AB, Prendergast PJ, Taylor Met al., 2007,

    Cement mantle fatigue failure in total hip replacement: Experimental and computational testing

    , JOURNAL OF BIOMECHANICS, Vol: 40, Pages: 1525-1533, ISSN: 0021-9290
  • Journal article
    Sackfield A, Dini D, Hills DA, 2006,

    The contact problem for a wheel having a 'flat'

    , WEAR, Vol: 261, Pages: 1265-1270, ISSN: 0043-1648
  • Conference paper
    Cann PM, 2006,

    Grease degradation in a bearing simulation device

    , 32nd Leeds-Lyon Symposium on Tribology, Publisher: ELSEVIER SCI LTD, Pages: 1698-1706, ISSN: 0301-679X
  • Journal article
    Cann PM, 2006,

    The "leaves on the line" problem - a study of leaf residue film formation and lubricity under laboratory test conditions

    , TRIBOLOGY LETTERS, Vol: 24, Pages: 151-158, ISSN: 1023-8883
  • Journal article
    Spikes HA, 2006,

    Sixty years of EHL

    , Lubrication Science, Vol: 18, Pages: 265-291, ISSN: 0954-0075

    It is now 60 years since Ertel produced the first solution to the elastohydrodynamic lubrication (EHL) problem. There has been enormous progress since then, both in numerical modelling and in experimental research on EHL. The moving, rough surface EHL problem can now be solved on laptop-level computers, while maps of film thickness, pressure and temperature can be obtained experimentally from within rolling/sliding contacts. However, there remain some important questions that have not been fully resolved. One of the most contentious is how to describe the Rheological properties of lubricants under the very severe conditions present in thin film EHL contacts. A second is how to model mixed lubricated contact, where the fluid film can break down at asperity conjunctions. But perhaps the greatest challenge to researchers in EHL is to produce useful design equations for predicting the performance of machine components operating in EHL and thereby ensure that EHL theory becomes an integral part of the design process. Copyright © 2006 John Wiley & Sons, Ltd.
  • Conference paper
    Hills DA, Dini D, 2006,

    A new method for the quantification of nucleation of fretting fatigue cracks using asymptotic contact solutions

    , 4th International Symposium on Fretting Fatique, Publisher: ELSEVIER SCI LTD, Pages: 1114-1122, ISSN: 0301-679X
  • Journal article
    de Vicente J, Spikes HA, Stokes JR, 2006,

    Viscosity ratio effect in the emulsion lubrication of soft EHL contact

    , JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME, Vol: 128, Pages: 795-800, ISSN: 0742-4787
  • Journal article
    Churchman CM, Dini D, Hills DA, 2006,

    Closure at the root of a sharp notch

    , INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, Vol: 48, Pages: 1063-1071, ISSN: 0020-7403
  • Journal article
    Nikas GK, Sayles RS, 2006,

    Study of leakage and friction of flexible seals for steady motion via a numerical approximation method

    , TRIBOLOGY INTERNATIONAL, Vol: 39, Pages: 921-936, ISSN: 0301-679X
  • Journal article
    Korsunsky AM, Liu J, Golshan M, Dini D, Zhang SY, Vorster WJet al., 2006,

    Measurement of residual elastic strains in a titanium alloy using high energy synchrotron X-ray diffraction

    , EXPERIMENTAL MECHANICS, Vol: 46, Pages: 519-529, ISSN: 0014-4851
  • Conference paper
    Dini D, Regino GM, Dunne FPE, Korsunsky AMet al., 2006,

    Polycrystal Deformation: Modelling And Diffraction Measurements For The Development Of Microscopic Energy-Based Fatigue Prediction Criteria

    , Mesomechanics 2006 (8th Mesomechanics Conference)
  • Journal article
    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.

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