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  • Conference paper
    Reina S, Dini D, 2009,

    INCIPIENT SLIP AND FRICTIONAL CREEP OF TYRED SYSTEMS

    , STLE/ASME 2008 International Joint Tribology Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 613-615
  • Conference paper
    Accardi MA, Dini D, 2009,

    MODELLING OF THE MECHANICAL BEHAVIOUR OF HUMAN JOINTS CARTILAGE

    , STLE/ASME 2008 International Joint Tribology Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 147-149
  • Conference paper
    Balcombe R, Fowell MT, Dini D, 2009,

    Modelling rolling contact fatigue cracks in the hydrodynamic lubrication regime: a coupled approach

    , Mesomechanics 2009 Conference, Publisher: ELSEVIER SCIENCE BV, Pages: 245-248, ISSN: 1877-7058
  • Conference paper
    Zografos A, Dini D, 2009,

    A combined BEM/Contact Asymptotics (BEM-CA) semi-analytical formulation for the assessment of fretting damage in bolted joints

    , Mesomechanics 2009 Conference, Publisher: ELSEVIER SCIENCE BV, Pages: 201-204, ISSN: 1877-7058
  • Conference paper
    Reina S, Dini D, Hills DA, 2009,

    On the accurate prediction of interfacial micro-slip in frictional joints using distributed dislocations and quadratic programming techniques

    , Mesomechanics 2009 Conference, Publisher: ELSEVIER SCIENCE BV, Pages: 181-184, ISSN: 1877-7058
  • Conference paper
    Sih GC, Korsunsky AM, Dini D, 2009,

    Mesomechanics 2009 Foreword: Dissipation and damage across multiple scales in physical and mechanical systems

    , Mesomechanics 2009 Conference, Publisher: ELSEVIER SCIENCE BV, Pages: 1-3, ISSN: 1877-7058
  • Journal article
    Laine E, Olver AV, Lekstrom MF, Shollock BA, Beveridge TA, Hua DYet al., 2009,

    The Effect of a Friction Modifier Additive on Micropitting

    , TRIBOLOGY TRANSACTIONS, Vol: 52, Pages: 526-533, ISSN: 1040-2004
  • Conference paper
    Hili J, Olver AV, Edwards S, Jacobs Let al., 2009,

    EXPERIMENTAL INVESTIGATION OF FILM THICKNESS BEHAVIOUR AT VERY HIGH SPEEDS

    , STLE/ASME 2008 International Joint Tribology Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 291-+
  • Journal article
    Benedet J, Green JH, Lamb GD, Spikes HAet al., 2009,

    Spurious Mild Wear Measurement Using White Light Interference Microscopy in the Presence of Antiwear Films

    , TRIBOLOGY TRANSACTIONS, Vol: 52, Pages: 841-846, ISSN: 1040-2004
  • Conference paper
    Mavraki A, Cann PM, 2009,

    Lubricating Film Thickness Measurements on Bovine Serum

    , STLE/ASME 2008 International Joint Tribology Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 123-125
  • Conference paper
    Fowell MT, Olver A, Spikes HA, Pegg IGet al., 2009,

    MODELLING OF MICRO TEXTURED BEARINGS WITH MASS-CONSERVING CAVITATION: A TWO DIMENSIONAL PROBLEM

    , STLE/ASME 2008 International Joint Tribology Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 343-+
  • Conference paper
    Medina S, Dini D, Olver AV, Hills DAet al., 2009,

    FAST COMPUTATION OF FRICTIONAL ENERGY DISSIPATION IN ROUGH CONTACTS UNDER PARTIAL SLIP

    , STLE/ASME 2008 International Joint Tribology Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 573-575
  • Journal article
    Dini D, Song X, Zhang SY, Korsunsky AMet al., 2009,

    Residual strain analysis in polycrystalline aggregates using diffraction measurement and finite element modelling

    , J STRAIN ANAL ENG, Vol: 44, Pages: 55-70, ISSN: 0309-3247

    This paper reviews some of the modelling and experimental techniques recently employed by the authors for the analysis of the macro- and mesoscopic behaviour of polycrystalline aggregates. A joined-up approach is used for assessing the deformation behaviour of polycrystalline materials at the macroscopic and grain levels, based on combining modelling using the crystal plasticity finite element (CPFE) method with experimental characterization by in situ loading and continuous lattice strain measurement by diffraction. The complementarity of the two methodologies is emphasized, as it helps to improve understanding of the physics underlying inelastic deformation, damage mechanisms, and fatigue crack initiation. The proposed approach is part of the attempt to develop a general framework that will enable reliable and accurate determination of the inhomogeneous fields of plastic strain, the regions of localized plasticity, and intergranular residual stresses. Examples are given of microscopically calibrated CPFE simulations being used to match the experimentally observed evolution of lattice stresses and strains in advanced structural alloys of industrial interest.
  • Journal article
    Reddyhoff T, Spikes HA, Olver AV, 2009,

    Compression heating and cooling in elastohydrodynamic contacts

    , Tribology Letters, Vol: 36, Pages: 69-80, ISSN: 1023-8883

    In this study, the infrared temperature mapping technique, originally developed by Sanborn and Winer (Trans ASME J Tribol 93:262-271, 1971) and extended by Spikes et al. (Tribol Lett 17(3):593-605, 2004), has been made more sensitive and used to study the temperature rise of elastohydrodynamic contacts in pure rolling. Under such conditions lubricant shear heating within the contact is considered negligible and this allows temperature changes due to lubricant compression to be investigated. Pure rolling surface temperature distributions have been obtained for contacts lubricated with a range of lubricants, included a group I, and group II mineral oil, a polyalphaolefin (group IV), the traction fluid Santotrac 50 and 5P4E, a five-ring polyphenyl-ether. Resulting maps show the temperature rise in the contact increases in the inlet due to compression heating and then decreases and in most cases becomes negative in the exit region due to the effect of decompression. Temperature changes increase with entrainment speed but in the current tests are always very small, and less than 1 C. Contact temperature rises from compression were compared to those from sliding contacts (where a slide-roll ratio of 0.5 was applied). Here the contribution to the contact temperature from compression is shown to decrease dramatically with entrainment speed. The lubricant 5P4E is found to behave differently from other lubricants tested in that it showed a peak in temperature at the outlet. This effect becomes more pronounced with increasing speed, and has tentatively been attributed to a phase change in the exit region. Using moving heat source theory, the measured temperature distributions have been converted to maps showing rate of heat input into each surface and the latter compared with theory. Qualitative agreement between theory and experiment is found, and a more accurate theoretical comparison is the subject of ongoing study. 2009 Springer Science+Business Media, LLC.
  • Conference paper
    Reddyhoff T, Spikes HA, Olver AV, 2009,

    Improved temperature mapping of ehl contacts

    , Miami, FL, United states, 2008 STLE/ASME International Joint Tribology Conference, IJTC 2008, October 20, 2008 - October 22, 2008, Publisher: ASME, Pages: 265-267

    An effective means of studying lubricant film rheology within EHL contacts is by detailed mapping of the temperature of the fluid and the bounding surfaces within the lubricated contact area. This provides a way of directly measuring the rheology of lubricant films under true EHL conditions. Furthermore, temperature measurement itself provides a very effective means of testing and validating computer simulations. In the current work, the experimental approach initially developed by Sanborn and Winer [11 and then by Spikes and co-workers [2], has been advanced to include a high specification infrared (IR) camera and microscope. This is a similar approach to that taken by Yagi and Kyogoku [3]. As well as the instantaneous capture of full field measurements, this has the advantage of increased sensitivity and higher spatial resolution than previous systems used. The increased sensitivity enables a much larger range of testable operating conditions; namely lower loads, speeds and reduced sliding. In addition, the range of test lubricants can be extended beyond high shearing traction fluids. One additional advantage of instantaneous full field measurements is that the weak infrared optical interference caused by the film can be observed and can used to exactly locate the centre of the contact in the resulting temperature maps. These new possibilities have been used to investigate and compare the rheological properties and compression cooling effects exhibited by a PAO, a group II mineral oil, and a traction fluid. Copyright 2008 by ASME.
  • Journal article
    Dickinson A, Browne M, Jeffers J, Taylor Aet al., 2009,

    Pre-clinical analysis of an acetabular cup with improved in vivo stability and integrity

    , Key Engineering Materials, Vol: 396-398, Pages: 31-34
  • Journal article
    Jeffers JRT, Roques A, Taylor A, Tuke MAet al., 2009,

    The problem with large diameter metal-on-metal acetabular cup inclination.

    , Bull NYU Hosp Jt Dis, Vol: 67, Pages: 189-192, ISSN: 1936-9719

    Large diameter metal-on-metal hip bearings have proven to be clinically successful in active patients, but, in a small number, they are associated with elevated wear and high metal ion levels when cup inclination angles are too steep and the version is too extreme, or either alone. Based on the geometry of six different commercially available large diameter metal-on-metal acetabular components, this study demonstrated that the critical bearing surface operates at an angle up to 16 masculine greater than the cup face inclination. Due to geometry alone, measured cup inclination is not the angle that most surgeons perceive it to be. We strongly recommend when employing large diameter metal-on-metal bearings that lower inclination and version angles are targeted to prevent excessive wear.
  • Conference paper
    Korsunsky AM, Song X, Belnoue J, Jun T, Hofmann F, De Matos PFP, Nowell D, Dini D, Aparicio-Blanco O, Walsh MJet al., 2009,

    Crack tip deformation fields and fatigue crack growth rates in Ti–6Al–4V☆

    , Pages: 1771-1779, ISSN: 0142-1123

    In this paper we present an overview of experimental and modelling studies of fatigue crack growth rates in aerospace titanium alloy Ti-6Al-4V. We review work done on the subject since the 1980s to the present day, identifying test programmes and procedures and their results, as well as predictive approaches developed over this period. We then present the results of some of our recent experiments and simulations. Fatigue crack growth rates (FCGRs) under constant applied load were evaluated as a function of crack length, and the effect of overload (retardation) was considered. Crack opening was measured during cycling using digital image correlation, and residual stress intensity factor was determined using synchrotron X-ray diffraction mapping. Modelling techniques used for the prediction of FCGRs are then reviewed, and an approach based on the analysis of energy dissipation at the crack tip is proposed. Finally, directions for further research are identified.
  • Conference paper
    Ku ISY, Reddyhoff T, Choo JH, Holmes AS, Spikes HAet al., 2009,

    Lubrication performance of liquids of different viscosities in MEMS devices

    , Lake Buena Vista, FL, United states, Society of Tribologists and Lubrication Engineers Annual Meeting and Exhibition 2009, May 17, 2009 - May 21, 2009, Publisher: Society of Tribologists and Lubrication Engineers, Pages: 178-180
  • Journal article
    Cann PM, 2008,

    In-contact molecular spectroscopy of liquid lubricant films

    , MRS Bulletin, Vol: 33, Pages: 1151-1158, ISSN: 0883-7694
  • Journal article
    Dini D, Hills DA, 2008,

    Characteristics of asymptotic solutions for slightly rounded contacts

    , Tribology - Materials, Surfaces and Interfaces, Vol: 2, Pages: 121-127, ISSN: 1751-5831

    The characteristics of a semi-infinite flat and rounded contact, subject to constant normal load and oscillating shear, are found. These include the slip displacement and frictional energy expenditure, together with the process of frictional shakedown. The set of solutions is applied to the problem of a D shaped punch having a very small radius at the notionally sharp corner. The possible application of the methodology outlined in this paper to a range of fretting fatigueproblems is also discussed. © 2008 W. S. Maney & Son Ltd.
  • Journal article
    Banerjee N, Dini D, Hills DA, 2008,

    Frictional complete contacts subject to shear and bulk tension

    , PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE, Vol: 222, Pages: 2301-2309, ISSN: 0954-4062
  • Journal article
    Qiu H, Dini D, Hills DA, 2008,

    Torsional contact of an elastic flat-ended cylinder

    , JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, Vol: 56, Pages: 3352-3362, ISSN: 0022-5096
  • Journal article
    Dini D, Sackfield A, Hills DA, 2008,

    An axi-symmetric Hertzian Contact subject to cyclic shear and severe wear

    , WEAR, Vol: 265, Pages: 1918-1922, ISSN: 0043-1648
  • Journal article
    Topolovec-Miklozic K, Lockwood F, Spikes H, 2008,

    Behaviour of boundary lubricating additives on DLC coatings

    , WEAR, Vol: 265, Pages: 1893-1901, ISSN: 0043-1648
  • Conference paper
    Spikes H, 2008,

    Low saps antiwear additives

    Modern engine lubricant specifications impose limits on permissible sulfur and phosphorus and ash levels. This necessitates a reduction in the concentration of the additive ZDDP which, in future, may require the latter's partial or complete replacement by other chemistries which have less or zero phosphorus, sulfur, and/or ash. The main types of low SAPS additive that have been suggested to have antiwear performance includes MDDP, thiophosphates and thiophosphonates, metal dialkylphosphates phosphates, metal dithiocarbamates, and organosulfides. These classes of additives were presented. This is an abstract of a paper presented at the 16th International Colloquium Tribology Lubricants Materials and Lubrication Engineering (Stuttgart/Ostfildern, Germany 1/15-17/2008).
  • Conference paper
    Laine E, Olver AV, Beveridge TA, 2008,

    Effect of lubricants on micropitting and wear

    , 34th Leeds-Lyon Symposium on Tribology, Publisher: ELSEVIER SCI LTD, Pages: 1049-1055, ISSN: 0301-679X
  • Journal article
    Nikas GK, Sayles RS, 2008,

    Finite-element analysis of layered rolling contacts

    , PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY, Vol: 222, Pages: 865-886, ISSN: 1350-6501
  • Conference paper
    Song X, Zhang SY, Dini D, Korsunsky AMet al., 2008,

    Finite element modelling and diffraction measurement of elastic strains during tensile deformation of HCP polycrystals

    , Symposium on Frontiers in Computational Materials Science, Publisher: ELSEVIER SCIENCE BV, Pages: 131-137, ISSN: 0927-0256
  • Journal article
    Hartinger M, Dumont M-L, Ioannides S, Gosman D, Spikes Het al., 2008,

    CFD modeling of a thermal and shear-thinning elastohydrodynamic line contact

    , JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME, Vol: 130, ISSN: 0742-4787
  • Journal article
    Nikas GK, Sayles RS, 2008,

    A study of lubrication mechanisms using two-phase fluids with porous bearing materials

    , PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY, Vol: 222, Pages: 771-783, ISSN: 1350-6501
  • Journal article
    Dini D, Barber JR, Churchman CM, Sackfield A, Hills DAet al., 2008,

    The application of asymptotic solutions to contact problems characterised by logarithmic singularities

    , EUR J MECH A-SOLID, Vol: 27, Pages: 847-858, ISSN: 0997-7538

    We give the contact pressure distribution near a contacting wedge having a slightly rounded form adjacent to a discontinuity in surface profile. It is shown that, well away from the rounding the pressure is logarithmic in form, just as it is near the apex of a sharp wedge. This pair of solutions may then be used to 'patch in' a roundness correction relevant to any punch having a discontinuous gradient. Further, it is noted that the multiplier on the logarithm term is pre-determined by the change in gradient. This process is applied to a finite, slightly blunt wedge, where the exact answer is known, and to a wheel having a worn flat. The agreement with the exact solution in the former case is seen to be very good. (c) 2007 Elsevier Masson SAS. All rights reserved.
  • Journal article
    Qiu H, Hills DA, Dini D, 2008,

    Further consideration of closure at the root of a sharp notch

    , JOURNAL OF STRAIN ANALYSIS FOR ENGINEERING DESIGN, Vol: 43, Pages: 405-409, ISSN: 0309-3247
  • Conference paper
    Smeeth M, Hamer C, Spikes HA, 2008,

    A study of antiwear additive film build up using the MTM (mini-traction machine)

    , Pages: 101-103

    The measurement of lubricant film thickness under elastohydrodynamic (EHL) contact conditions is well established and a variety of experimental techniques have been used, the most accurate and widely used of which is optical interferometry. This lends itself particularly well to the study of the all-important mixed and boundary regimes, since the films are of the same order of magnitude as the wavelength of light. The vast majority of these studies have been made under pure rolling conditions, since the necessary optical coatings preclude the use of high sliding speeds within the critical thin fluid film regime. These conditions are however precisely those required to activate ZDDPs and other antiwear additives, making accurate 'in situ' optical studies of additive film build-up difficult. A modification to the existing MTM (mini-traction machine) has allowed steel on steel contacts to be run under high sliding speed conditions, thereby allowing antiwear additive reactions to occur. By optically measuring the film thickness of these reaction films as they form, in tandem with friction measurements, a full picture of both friction and reaction film build-up can be made. Using a novel LED (light emitting diode) light source and accurate calibration procedures, the film thickness of the whole contact area can be measured down to a few nanometres. This paper presents a study of the behaviour of standard additive combinations under realistic operating conditions and describes the rig in detail. Copyright © 2007 by ASME.
  • Journal article
    Bae SC, Wong JSS, Kim M, Jiang S, Hong L, Granick Set al., 2008,

    Using light to study boundary lubrication: spectroscopic study of confined fluids

    , Philosophical Transactions of the Royal Society A. Mathematical, Physical and Engineering Sciences, Vol: 366
  • Journal article
    Spikes H, 2008,

    Low- and zero-sulphated ash, phosphorus and sulphur anti-wear additives for engine oils

    , LUBRICATION SCIENCE, Vol: 20, Pages: 103-136, ISSN: 0954-0075
  • Journal article
    Choo JW, Olver AV, Spikes HA, Dumont M-L, Ioannides Eet al., 2008,

    Interaction of asperities on opposing surfaces in thin film, mixed elastohydrodynamic lubrication

    , JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME, Vol: 130, ISSN: 0742-4787
  • Journal article
    Reddyhoff T, Dwyer-Joyce RS, Zhang J, Drinkwater BWet al., 2008,

    Auto-calibration of ultrasonic lubricant-film thickness measurements

    , Measurement Science & 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.
  • Journal article
    Qiu H, Paynter RJH, Dini D, Hills DAet al., 2008,

    The state of stress induced by ring dislocations in a semi-infinite stepped shaft

    , EUROPEAN JOURNAL OF MECHANICS A-SOLIDS, Vol: 27, Pages: 269-284, ISSN: 0997-7538
  • Journal article
    Qiu H, Hills DA, Nowell D, Dini Det al., 2008,

    Skew sliding of an elastic cylinder: An investigation of convection in contact

    , INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, Vol: 50, Pages: 293-298, ISSN: 0020-7403
  • Journal article
    Kadiric A, Sayles RS, Ioannides E, 2008,

    Thermo-mechanical model for moving layered rough surface contacts

    , Journal of Tribology-Transactions of the Asme, Vol: 130, ISSN: 1528-8897

    A numerical model designed to simulate a moving line contact of two rough layered bodies is presented. Fourier transforms are used to obtain fundamental solutions to relevant differential equations and then these solutions are used as kernel functions in a numerical scheme designed to provide a full thermomechanical solution for real layered contacts. The model assumes steady state heat transfer and predicts contact pressures and deformations, contact temperature rise, and resulting thermal stresses. The heat division between the contacting components is fully accounted for, as are the interactions between the mechanical and thermal displacements. Some results are presented to illustrate the potential importance of a full thermomechanical analysis as compared to a purely mechanical one as well as to demonstrate the influence of coating properties and surface roughness structure on the contact temperatures.
  • Conference paper
    Song X, Zhang SY, Dini D, Korsunsky AMet al., 2008,

    Inter-granular residual stresses in polycrystalline aggregates: finite element modelling and diffraction post-processing

    , MECASENS 4th International Conference on Stress Evaluation using Neutrons and Synchrotron Radiation, Publisher: TRANS TECH PUBLICATIONS LTD, Pages: 271-+, ISSN: 0255-5476
  • Journal article
    Korsunsky AM, Dini D, Walsh MJ, 2008,

    Prediction of fatigue crack growth rates in Ti-6Al-4V alloy

    , Solid Mechanics and its Applications, Vol: 152, Pages: 47-64, ISSN: 0925-0042

    Crack initiation under thermo-mechanical fatigue is analyzed with consideration given to oxidation and creep strain accumulation. Transitions and interactions between different mechanisms, crack initiation and crack propagation rates display significant scaling and size effects. The objective of this work is to present experimental data for crack initiation and propagation in aerospace alloys, and to offersome means of describing these data so as to develop improved capabilities for life prediction in aerospace materials and assemblies. © Springer Science+Business Media B.V. 2008.
  • 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
    Topolovec-Miklozic K, Forbus TR, Spikes H, 2008,

    Film forming and friction properties of overbased calcium sulphonate detergents

    , TRIBOLOGY LETTERS, Vol: 29, Pages: 33-44, ISSN: 1023-8883
  • 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
  • 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
  • Journal article
    Reddyhoff T, Dwyer-Joyce RS, Harper P, 2008,

    A new approach for the measurement of film thickness in liquid face seals

    , Tribology Transactions, Vol: 51, Pages: 140-149, ISSN: 1040-2004

    Face seals operate by allowing a small volume of the sealed fluid to escape and form a thin film between the contacting parts. The thickness of this film must be optimized to ensure that the faces are separated, yet the leakage is minimized. In this work the liquid film is measured using a novel ultrasonic approach with a view to developing a condition monitoring tool. The trials were performed in two stages. Initially tests were based on a lab simulation, where it was possible to compare the ultrasonic film thickness measurements with optical interference methods and capacitance methods. A direct correlation was seen between ultrasonic measurements and capacitance. Where ultrasonic and optical methods overlap, good correlation is observed; however, the optical method will not record film thickness above 0.72 m. A second set of trials was carried out, where the film thickness was monitored inside a seal test apparatus. Film thickness was successfully recorded as speed and load were varied. The results showed that while stationary the film thickness varied noticeably with load. When rotating, however, the oil film remained relatively stable around 2 m. During the normal operation of the seal, both sudden speed and load changes were applied in order to initiate a seal failure. During these events, the measured film thickness was seen to drop dramatically down to 0.2 m. This demonstrated the ability of the technique to predict failure in a face seal and therefore its aptitude for condition monitoring.
  • Book chapter
    Korsunsky AM, Dini D, Walsh MJ, 2008,

    Prediction of Fatigue Crack Growth Rates in Ti-6Al-4V Alloy

    , Multiscale Fatigue Crack Initiation and Propagation of Engineering Materials: Structural Integrity and Microstructural Worthiness, Editors: SIh, Netherlands, Publisher: Springer, Pages: 47-64, ISBN: 978-1-4020-8519-2
  • 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.

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