Publications
170 results found
Parkes M, Myant C, Cann PM, et al., 2014, The effect of buffer solution choice on protein adsorption and lubrication, Tribology International, Vol: 72, Pages: 108-117, ISSN: 0301-679X
Myant CW, fowell M, cann P, 2013, The effect of transient motion on Isoviscous-EHL films in compliant, point, contacts, Tribology International, Vol: 72, Pages: 98-107, ISSN: 1879-2464
Laser induced fluorescence was employed to measure lubricant film thickness in a compliant, point, contact during transient motion. Two types of transient sliding motion were investigated: start-up and sudden halting. The effects of acceleration rate and sliding speed on film formation and breakdown were studied.A clear relationship between start-up acceleration and the period of the film formation phase was observed. During sudden halting motion entrapment of fluid occurred in the centre of the contact. This trapped fluid was squeezed out of the contact over several seconds. The size of this entrapment was dependent on the initial sliding speed. The findings are compared to similar results for hard, point, contacts and the implications discussed.
Accardi MA, McCullen SD, Callanan A, et al., 2013, Effects of fiber orientation on the frictional properties and damage of regenerative articular cartilage surfaces, Tissue Engineering: Parts A, B, and C, Vol: 19, Pages: 2300-2310, ISSN: 1937-3368
Articular cartilage provides a low-friction, wear-resistant surface for diarthrodial joints. Due to overloading and overuse, articular cartilage is known to undergo significant wear and degeneration potentially resulting in osteoarthritis (OA). Regenerative medicine strategies offer a promising solution for the treatment of articular cartilage defects and potentially localized early OA. Such strategies rely on the development of materials to restore some aspects of cartilage. In this study, microfibrous poly(ɛ-caprolactone) scaffolds of varying fiber orientations (random and aligned) were cultured with bovine chondrocytes for 4 weeks in vitro, and the mechanical and frictional properties were evaluated. Mechanical properties were quantified using unconfined compression and tensile testing techniques. Frictional properties were investigated at physiological compressive strains occurring in native articular cartilage. Scaffolds were sheared along the fiber direction, perpendicular to the fiber direction and in random orientation. The evolution of damage as a result of shear was evaluated via white light interferometry and scanning electron microscopy. As expected, the fiber orientation strongly affected the tensile properties as well as the compressive modulus of the scaffolds. Fiber orientation did not significantly affect the equilibrium frictional coefficient, but it was, however, a key factor in dictating the evolution of surface damage on the surface. Scaffolds shear tested perpendicular to the fiber orientation displayed the highest surface damage. Our results suggest that the fiber orientation of the scaffold implanted in the joint could strongly affect its resistance to damage due to shear. Scaffold fiber orientation should thus be carefully considered when using microfibrous scaffolds.
Myant C, Cann P, 2013, In contact observation of model synovial fluid lubricating mechanisms, 1st International Conference on Biotribology (ICoBT), Publisher: ELSEVIER SCI LTD, Pages: 97-104, ISSN: 0301-679X
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- Citations: 31
Hart AJ, Muirhead-Allwood S, Porter M, et al., 2013, Which Factors Determine the Wear Rate of Large-Diameter Metal-on-Metal Hip Replacements?, JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME, Vol: 95A, Pages: 678-685, ISSN: 0021-9355
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- Citations: 53
Myant CWI, Cann PME, 2013, In contact observation of model synovial fluid lubricating mechanisms, Tribology International, Vol: 63, Pages: 97-104, ISSN: 0301-679X
This paper examines the fundamental mechanisms of synovial fluid lubrication in artificial joints. Film thickness measurements were made for bovine serum solutions in a model test device. In contact imaging was also carried out to aid interpretation of these results. The results indicated that two types of film are formed; a boundary layer of adsorbed protein molecules, which are augmented by a high-viscosity fluid film generated by hydrodynamic effects. The high-viscosity film is due to inlet aggregation of protein molecules forming a gel which is entrained into the contact preferentially at low speeds. As the speed increases this gel appears to shear thin, giving much lower lubricant film thickness. Results suggest that protein-containing fluids do not obey classical Newtonian EHL models. © 2012 Elsevier Ltd. All rights reserved.
Underwood RJ, Fowell M, Sayles R, et al., 2013, The development of a standard method for assessing wear of explanted metal-on-metal hip joints, ASTM Special Technical Publication, Vol: 1560 STP, Pages: 130-145, ISSN: 0066-0558
The concerns surrounding the current generation of metal-on- metal (MoM) hips and the regulatory requirements regarding the reporting of revised MoM components highlight the need for a standardised method for measuring the wear of explanted MoM hip components. This paper reviews the published measurement and analysis protocols used in studies of explanted MoM hips. Because of differences in the measurement and analysis techniques, it is not reliable to directly compare measurements between studies. This paper considers the requirements for a standardised measurement protocol and forms the rationale for a proposed international standard. Copyright © 2013 by ASTM International.
Underwood RJ, Kocagoz SB, Smith R, et al., 2013, A protocol to assess the wear of head/neck taper junctions in large head metal-on-metal (LHMoM) hips, ASTM Special Technical Publication, Vol: 1560 STP, Pages: 209-234, ISSN: 0066-0558
Researchers have hypothesized that the increased revision rate of LHMoM (Large Head Metal-on-Metal) hips compared to MoM hip resurfacings may be attributed to corrosion and wear at the head neck taper junction. Studies have reported visual evidence of fretting and corrosion at the taper junction, but no method has been described in the literature to quantify the amount of material lost from the taper junction. This paper describes a measurement protocol using a Taylor Hobson Talyrond Roundness instrument that allows the simultaneous measurement of surface form (wear) and surface topography (roughness). The methodology allows the measurement of the taper angle, geometry of worn region (depth, length), 3D surface maps and surface topography of the head conical taper. The accurate quantification of the taper geometry, wear and topography is essential to the understanding of the in vivo wear and corrosion mechanisms of taper junctions in LHMoM hips. Copyright © 2013 by ASTM International.
Ingram M, Underwood R, Denyer P, et al., 2013, The development of a laboratory screening method to optimize lubrication maintenance of high voltage equipment, NLGI Spokesman, Vol: 76, Pages: 9-21, ISSN: 0027-6782
Imperial College and National Grid Electricity Transmission carried out a study to evaluate lubrication maintenance of electrical switchgear used throughout the network. A discussion on this project covers the switchgear components and lubrication requirements; identification of lubricant degradation mechanisms; development of pertinent screening tests; survey of current lubricants used; and recommendations for the future.
Myant C, Cann P, 2013, Lubrication of artificial articular joints, Pages: 132-134
Myant CW, Fan T, Underwood R, et al., 2012, Synovial Fluid Lubrication of Artificial Joints: Protein Film Formation and Composition, Faraday Discussions, ISSN: 1364-5498
Fan J, Myant C, Underwood R, et al., 2012, Synovial fluid lubrication of artificial joints: protein film formation and composition, FARADAY DISCUSSIONS, Vol: 156, Pages: 69-85, ISSN: 1359-6640
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- Citations: 21
Underwood RJ, Zografos A, Sayles RS, et al., 2012, Edge loading in metal-on-metal hips: low clearance is a new risk factor, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART H-JOURNAL OF ENGINEERING IN MEDICINE, Vol: 226, Pages: 217-226, ISSN: 0954-4119
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- Citations: 74
Bills PJ, Racasan R, Underwood RJ, et al., 2012, Volumetric wear assessment of retrieved metal-on-metal hip prostheses and the impact of measurement uncertainty, Wear, Pages: 212-219
Myant CW, underwood R, fan J, et al., 2011, Lubrication of metal-on-metal hip joints: The effect of proteincontent and load on film formation and wear, Journal of the Mechanical Behavior of Biomedical Materials, Vol: 6, Pages: 30-40, ISSN: 1751-6161
Lubricant films were measured for a series of bovine serum and protein containing (albumin, globulin) saline solutions for CoCrMo femoral component sliding against a glass disc. Central film thickness was measured by optical interferometry as a function of time (constant mean speed: 0 and 10 mm/s) and variable mean speed (0–50 mm/s). The effect of load (5–20 N) on film thickness was also studied. The development of the wear scar on the CoCrMo surface was monitored by measuring the width of the contact zone during the film thickness tests. The results showed film thickness increased with time for both the static and sliding tests. Films formed in the static, loaded test were typically in the range of 3–40 nm. The globulin containing solutions formed the thickest films. In the sliding tests a wear scar rapidly formed on the implant component for the bovine serum and albumin fluids, negligible wear was observed for the globulin solutions. Film thickness increased with sliding time for all test solutions and was much greater than predicted by isoviscous EHL models. The film increase was found to correlate with increasing wear scar size and thus decreasing contact pressure. A new lubricating mechanism is proposed whereby during sliding the fluid undergoes bulk phase separation rheology, so that an elevated protein phase forms in the inlet zone. This protein phase is a high-viscosity biphasic matrix, which is periodically entrained into the contact forming a thick protective hydro-gel film. One of the main findings of this study is that film thickness was very sensitive to load; to a much greater extent than predicted by EHL models. Thus film formation in MoM hip joints is very susceptible to high contact pressures which might be due to implant misalignment and edge-loading.
Underwood R, Matthies A, Cann P, et al., 2011, A comparison of explanted Articular Surface Replacement and Birmingham Hip Resurfacing components, JOURNAL OF BONE AND JOINT SURGERY-BRITISH VOLUME, Vol: 93B, Pages: 1169-1177, ISSN: 0301-620X
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- Citations: 58
Mavraki A, Cann PM, 2011, Lubricating film thickness measurements with bovine serum, TRIBOLOGY INTERNATIONAL, Vol: 44, Pages: 550-556, ISSN: 0301-679X
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- Citations: 46
Accardi MA, Dini D, Cann PM, 2011, Experimental and numerical investigation of the behaviour of articular cartilage under shear loading-Interstitial fluid pressurisation and lubrication mechanisms, TRIBOLOGY INTERNATIONAL, Vol: 44, Pages: 565-578, ISSN: 0301-679X
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- Citations: 50
Matthies A, Underwood R, Cann P, et al., 2011, Retrieval analysis of 240 metal-on-metal hip components, comparing modular total hip replacement with hip resurfacing, JOURNAL OF BONE AND JOINT SURGERY-BRITISH VOLUME, Vol: 93B, Pages: 307-314, ISSN: 0301-620X
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- Citations: 85
Hart AJ, Ilo K, Underwood R, et al., 2011, The relationship between the angle of version and rate of wear of retrieved metal-on-metal resurfacings A PROSPECTIVE, CT-BASED STUDY, JOURNAL OF BONE AND JOINT SURGERY-BRITISH VOLUME, Vol: 93B, Pages: 315-320, ISSN: 0301-620X
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- Citations: 73
Fan J, Myant CW, Underwood R, et al., 2011, Inlet protein aggregation: a new mechanism for lubricating film formation with model synovial fluids, Proceedings of the Institution of Mechanical Engineers Part H - Journal of Engineering in Medicine, Vol: 225, Pages: 696-709, ISSN: 0954-4119
This paper reports a fundamental study of lubricant film formation with model synovial fluid components (proteins) and bovine serum (BS). The objective was to investigate the role of proteins in the lubrication process. Film thickness was measured by optical interferometry in a ball-on-disc device (mean speed range of 2–60 mm/s). A commercial cobalt–chromium (CoCrMo) metal femoral head was used as the stationary component. The results for BS showed complex time-dependent behaviour, which was not representative of a simple fluid. After a few minutes sliding BS formed a thin adherent film of 10–20 nm, which was attributed to protein absorbance at the surface. This layer was augmented by a hydrodynamic film, which often increased at slow speeds. At the end of the test deposited surface layers of 20–50 nm were measured. Imaging of the contact showed that at slow speeds an apparent ‘phase boundary’ formed in the inlet just in front of the Hertzian zone. This was associated with the formation of a reservoir of high-viscosity material that periodically moved through the contact forming a much thicker film. The study shows that proteins play an important role in the film-forming process and current lubrication models do not capture these mechanisms.
Arora H, Cann PM, 2010, Lubricant film formation properties of alkyl imidazolium tetrafluoroborate and hexafluorophosphate ionic liquids, TRIBOLOGY INTERNATIONAL, Vol: 43, Pages: 1908-1916, ISSN: 0301-679X
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- Citations: 29
Nakano K, Reddyhoff T, Cann P, et al., 2009, Film formation of liquid crystals in EHD contacts
The film formation of two types of liquid crystals, i.e., 4-pentyl-4′-cyanobiphenyl (5CB) and 4-octyl-4′-cyanobiphenyl (8CB), was studied in EHD contacts. The enhancement of film formation by the addition of palmitic acid affected the traction characteristics of 5CB. The traction coefficient of pure 5CB increased significantly with a decrease in the entrainment speed at entrainment speeds below 0.1 m/sec. The change in the EHD film of pure 8CB was similar to that of 5CB with 0.1 wt % palmitic acid. The traction coefficient of 8CB was lower than that of 5CB, ≈ 0.02, which was maintained at low entrainment speeds. These special properties were attributed to the layer structure of the smectic phase. This is an abstract of a paper presented at the Proceedings of World Tribology Conference (Kyoto, Japan 9/6-11/2009).
Cann P, 2009, Grease degradation in rolling element bearings - Development of a simulation tests, World Tribology Congress 2009 - Proceedings
Improvements in rolling element bearing design, manufacturing standards and materials have resulted in significant increase in bearing life and performance. Thus, bearing life is often limited by lubrication failure of the grease. A study was carried out to examine grease degradation under controlled operating conditions simulating those experienced in rolling element bearings. The critical bearing factors determining grease lubrication failure wee considered to be the short replenishment time between over-rolling, thin lubricant films in the raceway, and the presence of metal wear debris. This is an abstract of a paper presented at the 2009 World Tribology Congress (Kyoto, Japan 9/6-11/2009).
Arora H, Cann P, 2009, Lubrication properties of alkyl imidazolium tetrafluoroborate and hexafluorophosphate ionic liquids under mixed sliding-rolling conditions, World Tribology Congress 2009 - Proceedings
The ionic liquids (IL) lubrication properties in mixed rolling-sliding and rolling EHL conditions were studied. The tribological performance of four neat IL was compared with an additized mineral oil (MO). RITL friction coefficients were less than the MO for all speed and slide-roll conditions studied. The film thickness results showed that three of the fluids demonstrated classical EHL behavior with log film vs. log speed gradients in the range 0.56-0.66. However, the 1-butyl-3-methyl imidazolium tetrafluoroborate fluid gave anomalously thick, time-dependent film results at low speeds. This behavior was associated with the shorter, alkyl chain cations (l-butyl-3-methyl) rather than the anion. Film formation was not due to RTIL decomposition and subsequent anion reaction with the wear surface. This is an abstract of a paper presented at the World Tribology Congress (Kyoto, Japan 9/6-11/2009).
Mavraki A, Cann PM, Mischler S, et al., 2009, FRICTION AND LUBRICANT FILM THICKNESS MEASUREMENTS ON SIMULATED SYNOVIAL FLUID, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY, Vol: 223, Pages: 606-607, ISSN: 1350-6501
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- Citations: 2
Mavraki A, Cann PM, 2009, Friction and lubricant film thickness measurements on simulated synovial fluids, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY, Vol: 223, Pages: 325-335, ISSN: 1350-6501
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- Citations: 28
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
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- Citations: 1
Cann PM, 2008, In-contact molecular spectroscopy of liquid lubricant films, MRS Bulletin, Vol: 33, Pages: 1151-1158, ISSN: 0883-7694
Chapkov AD, Bair S, Cann P, et 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
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- Citations: 58
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