33 results found
Shin S, Alyasiri, D'Auria M, et al., 2019, Polymer-based 3-D printed Ku-band steerable phased-array antenna subsystem, IEEE Access, Vol: 7, Pages: 106662-106673, ISSN: 2169-3536
This paper introduces the first fully 3-D printed tunable microwave subsystem, consisting of 26 circuit elements. Here, a polymer-based 3-D printed Ku-band 4-element steerable phased-array antenna with fully integrated beam forming network is demonstrated. Polyjet was adopted for fabricating the main body of the subsystem, as it is capable of producing a geometrically complex structure with high resolution over a large volume. Low-cost fused deposition modeling was chosen to manufacture the dielectric inserts and brackets for the phase shifters. The measured radiation pattern revealed that the phased-array antenna subsystem has total beam steering angles of 54° and 52° at 15 GHz and 17 GHz, respectively. Excellent input return loss behavior was observed across the optimum operational frequency range of 15 to 17 GHz; with a worst-case measured return loss of 12.9 dB. This work clearly shows the potential of using 3-D printing technologies for manufacturing fully integrated subsystems with complex geometric features.
Carpenter G, Bozorgi S, Vladescu S, et al., 2019, A study of saliva lubrication using a compliant oral mimic, Food Hydrocolloids, Vol: 92, Pages: 10-18, ISSN: 0268-005X
Due to ethical issues and the difficulty in obtaining biological tissues, it is important to find synthetic elastomers that can be used as replacement test media for research purposes. An important example of this is friction testing to understand the mechanisms behind mouthfeel attributes during food consumption (e.g. syrupy, body and clean finish), which requires an oral mimic. In order to assess the suitability of possible materials to mimic oral surfaces, a sliding contact is produced by loading and sliding a hemispherical silica pin against either a polydimethyl siloxane (PDMS), agarose, or porcine tongue sample. Friction is measured and elastohydrodynamic film thickness is calculated based on the elastic modulus of the samples, which is measured using an indentation method. Tests were performed with both saliva and pure water as the lubricating fluid and results compared to unlubricated conditions.PDMS mimics the tongue well in terms of protein adhesion, with both samples showing significant reductions in friction when lubricated with saliva versus water, whereas agarose showed no difference between saliva and water lubricated conditions. This is attributed to PDMS's OSi(CH3)2- group which provides excellent adhesion for the saliva protein molecules, in contrast with the hydrated agarose surface. The measured modulus of the PDMS (2.2 MPa) is however significantly greater than that of tongue (3.5 kPa) and agarose (66–174 kPa). This affects both the surface (boundary) friction, at low sliding speeds, and the entrained elastohydrodynamic film thickness, at high speeds.Utilising the transparent PDMS sample, we also use fluorescence microscopy to monitor the build-up and flow of dyed-tagged saliva proteins within the contact during sliding. Results confirm the lubricous boundary film forming nature of saliva proteins by showing a strong correlation between friction and average protein intensity signals (cross correlation coefficient = 0.87). This demonstrates
Shin S, Alyasiri D, D’Auria M, et al., Fully 3-D printed tunable microwave subsystem, International Microwave Workshop Series on Advanced Materials and Processes (IMWS-AMP), Publisher: IEEE
Lucyszyn S, Shang X, Otter W, et al., Polymer-based 3D printed millimeter-wave components for spacecraft payloads, International Microwave Workshop Series on Advanced Materials and Processes (IMWS-AMP), Publisher: IEEE MTT-S
This paper summarizes the current state of research & development within the U.K. for polymer-based 3D printed guided-wave and quasi-optical components for spacecraft payloads. Preliminary measured results look promising and show that this emerging technology may well overtake existing machined technologies in the not too distant future for general aerospace applications.
Wu B, Myant C, Weider SZ, 2017, The value of additive manufacturing: future opportunities, Briefing paper, 2
The global additive manufacturing (AM) – 3D printing – industr y was valued at $6 billion for 2016, and is predicted to grow to more than $26 billion by 20221. This rapid growth has arisen mainly because of the evolution of AM from primarily a prototyping tool to a useful end-product fabrication method in some high-value manufacturing applications (e.g., in the aerospace, medical device and automotive industries).• AM has the potential to offer many economic, technical and environmental advantages over traditional manufacturing approaches, including decreased production costs and times, the possibility of flexible and bespoke production, as well as a reduction in energy usage and waste. To realise these benefits, however, several barriers – across the entire AM process chain – need to be overcome. For example, improved design software, faster printing technology, increased automation and better industry standards are required.• To realise a more-efficient and more-profitable industr y, ‘game-changing’ AM research breakthroughs are thus required. Involving more researchers – from a wide array of scientific and engineering backgrounds – will be beneficial, as will a closer working relationship between academia and industr y.• The concept of molecular science and engineering2 – melding a deep understanding of molecular science with an engineering mind-set – provides an excellent framework for the ‘cross pollination’ of research ideas. In the pursuit of solving some of the biggest needs in AM, scientists and engineers – from a range of disciplines – can be brought together to communicate and collaborate at all stages of the AM research-to-final-product chain. In this way, costly late-stage changes can be avoided and the route to final, functional end-use products can be rapidly optimised. In addition, a new generation of scientists and engineers can be trained in a transdi
Tsui S, Tandy J, Myant C, et al., 2016, Friction measurements with yoghurt in a simulated tongue-palate contact, Biotribology, Vol: 8, Pages: 1-11
© 2016 The perception of many food attributes is related to mechanical stimulation and friction experienced in the tongue-palate contact during mastication. Friction in the tongue-palate is determined by the changing film properties (composition, component distribution, thickness) in the conjunction. We suggest this evolution is essentially determined by tongue-palate film loss rather than shear flow entrainment which predominates in conventional bearing lubrication. The paper reports friction measurements in a simulated tongue-palate contact for a range of high and low fat dairy foods. A reciprocating, sliding contact with restricted stroke length ( < contact width) was used; under these conditions there is negligible shear-entrainment of fluid from outside the contact area. The tongue-palate contact was simulated by a PDMS ball and glass surface. The effect of hydrophobic and hydrophilic surfaces on friction was investigated for different fat contents (0, 4.2, 9.5% wt fat). Friction was measured over 60 s of rubbing. Significant differences were observed in the friction change with time for different fat contents (μ 9.5 < μ 4.2 < μ 0 wt%) and for different surface energy conditions (μ hydrophilic < μ hydrophobic). Post-test visualisation of the rubbed films showed that low friction coefficient was associated with the formation of a thin oil film on deposited particulate solids.
Li J, wu BILLY, Myant CONNOR, 2016, The Current Landscape for Additive Manufacturing Research
Masen M, Myant C, 2015, Second International Conference on Biotribology (ICoBT), Tribology International, Vol: 89, Pages: 1-1, ISSN: 1879-2464
Parkes M, Myant C, Cann PM, et al., 2015, Synovial fluid lubrication: The effect of protein interactions on adsorbed and lubricating films, Biotribology, Vol: 1-2, Pages: 51-60, ISSN: 2352-5738
© 2015 Elsevier Ltd. All rights reserved. Synovial fluid lubrication is dependent on protective protein films that form between joint surfaces. Under static conditions surface film formation occurs through adsorption, while under dynamic conditions protein aggregation under shear and load becomes the dominant mechanism. This work examines how the protein content of six model synovial fluids affects film formation under static and rolling conditions and if the changes in properties can be correlated. With an increase in the statically adsorbed mass and the rate of adsorption the film thickness under rolling increased. These increases did not correlate with the total protein content of the fluid, but were dependent on the type of protein. An increase in pH reduced the adsorbed mass, rate of adsorption and film thickness, but was of secondary importance to the type of protein. The rolling film thickness was also correlated with the viscoelastic properties of the films formed under static conditions. In this case thinner rolling films corresponded to the more hydrated, viscoelastic adsorbed films. The strong correlations found between the properties of the adsorbed films and those formed under rolling indicate that the same protein-protein and protein-surface interactions may govern both mechanisms of film formation despite the differences in the film structures.
Parkes M, Myant C, Dini D, et al., 2014, Tribology-optimised silk protein hydrogels for articular cartilage repair, Tribology International, Pages: ---, ISSN: 0301-679X
Myant CW, fowell M, spikes H, et al., 2014, A Study of Lubricant Film Thickness in Compliant Contacts of Elastomeric Seal Materials Using a Laser Induced Fluorescence Technique, Tribology International, Vol: 80, Pages: 76-89, ISSN: 1879-2464
A laser induced fluorescence technique was used to investigate the build-up of lubricant films in compliant contacts operating in the isoviscous elasto-hydrodynamic regime (I-EHL). The described technique utilises an optimised optical set-up with a relatively high signal-to-noise ratio and was shown to be able to produce film thickness maps of the complete contact area and measure a very wide span of thicknesses, from 50 nm to 100 μm. Maps of film thickness were obtained over a range of entrainment speeds and loads for three different contact configurations and two elastomer materials, polydimethylsiloxane (PDMS) and a fluorocarbon rubber (FKM) which is typically used in rotary seal applications. In a model contact of a nominally smooth PDMS ball sliding on a glass flat, a crescent shaped area of reduced film thickness was observed towards the contact exit. In contrast to typical elasto-hydrodynamic contacts, no side-lobes of reduced film thickness were recorded, while the central film region exhibited a converging wedge shape. The elliptical contact of an FKM O-ring rolling on a flat glass showed a central region of flat film while areas of minimum film thickness were located near the contact edges either side of the centre. The highly conformal contact of relatively rough FKM O-ring sliding against a concave glass lens, a geometry more representative of that found in elastomeric seals, showed discrete regions of reduced film, corresponding to surface roughness asperities. With rising entrainment speed, some lift-off was observed, with surface roughness asperities appearing to be increasingly compressed. Measured films thicknesses were compared to existing theoretical predictions for I-EHL contacts and the level of agreement was found to be highly dependent on contact geometry and applied conditions.
Myant CW, Cann P, 2014, The effect of transient conditions on synovial fluid protein aggregation lubrication, Journal of the Mechanical Behavior of Biomedical Materials, Vol: 34, Pages: 349-357, ISSN: 1751-6161
Little is known about the prevailing lubrication mechanisms in artificial articular joints and the way in which these mechanisms determine implant performance. The authors propose that interfacial film formation is determined by rheological changes local to the contact and is driven by aggregation of synovial fluid proteins within the contact inlet region. A direct relationship between contact film thickness and size of the protein aggregation within the inlet region has been observed.In this paper the latest experimental observations of the protein aggregation mechanism are presented for conditions which more closely mimic joint kinematics and loading. Lubricant films were measured for a series of bovine calf serum solutions for CoCrMo femoral component sliding against a glass disc. An optical interferometric apparatus was employed to study the effects of transient motion on lubricant film formation. Central film thickness was measured as a function of time for a series of transient entrainment conditions; start-up motion, steady-state and non-steady-state uni-directional sliding, and bi-directional sliding. The size of the inlet aggregations was found to be dependent upon the type of transient condition. Thick protective protein films were observed to build up within the main contact region for all uni-directional tests. In contrast the inlet aggregation was not observed for bi-directional tests. Contact film thickness and wear was found to be directly proportional to the presence of the inlet protein phase. The inlet phase and contact films were found to be fragile when disrupted by surface scratches or subjected to reversal of the sliding direction.
Myant C, Cann P, 2014, On the matter of synovial fluid lubrication: Implications for Metal-on-Metal hip tribology, Journal of the Mechanical Behavior of Biomedical Materials, Vol: 34, Pages: 338-348, ISSN: 1751-6161
Artificial articular joints present an interesting, and difficult, tribological problem. These bearing contacts undergo complex transient loading and multi axes kinematic cycles, over extremely long periods of time (>10 years). Despite extensive research, wear of the bearing surfaces, particularly metal–metal hips, remains a major problem. Comparatively little is known about the prevailing lubrication mechanism in artificial joints which is a serious gap in our knowledge as this determines film formation and hence wear. In this paper we review the accepted lubrication models for artificial hips and present a new concept to explain film formation with synovial fluid. This model, recently proposed by the authors, suggests that interfacial film formation is determined by rheological changes local to the contact and is driven by aggregation of synovial fluid proteins. The implications of this new mechanism for the tribological performance of new implant designs and the effect of patient synovial fluid properties are discussed.
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.
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
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.
Myant C, Cann P, 2013, Lubrication of artificial articular joints, Pages: 132-134
Timm K, Myant C, Nuguid H, et al., 2012, Investigation of friction and perceived skin feel after application of suspensions of various cosmetic powders, INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Vol: 34, Pages: 458-465, ISSN: 0142-5463
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
Polymer powders are commonly added to cosmetic formulations to improve product performance and skin feel. This study investigates the effect of particle concentration and size on the lubricating properties of powder suspensions. Results are reported for various particle sizes and concentrations.When the tribological contact was fully immersed the addition of particles had no effect. However different behaviour was observed when the contact was only partially lubricated. In this case, a three-stage friction coefficient curve was observed. By varying the particle size and concentration it was shown that the duration and magnitude of each stage can be controlled.
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.
Timm K, Myant C, Spikes HA, et al., 2011, Cosmetic powder suspensions in compliant, fingerprintlike contacts, BIOINTERPHASES, Vol: 6, Pages: 126-134, ISSN: 1934-8630
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.
Myant C, Fowell M, Spikes HA, et al., 2010, An Investigation of Lubricant Film Thickness in Sliding Compliant Contacts, TRIBOLOGY & LUBRICATION TECHNOLOGY, Vol: 66, Pages: 46-+, ISSN: 1545-858X
Myant C, Fowell M, Spikes HA, et al., 2010, An Investigation of Lubricant Film Thickness in Sliding Compliant Contacts, Tribology Transactions, Vol: 53, Pages: 684-694, ISSN: 1547-397X
Andablo-Reyes E, de Vicente J, Hidalgo-Alvarez R, et al., 2010, Soft Elasto-Hydrodynamic Lubrication, Tribology Letters, Vol: 39, Pages: 109-14, ISSN: 1023-8883
This article examines the use of ferrofluids to control starvation in lubricated contacts. Starvation in a ball-plate contact is experimentally studied under sliding-rolling conditions using a Mini Traction Machine (MTM). Friction is measured and the experimental results are presented in the form of Stribeck curves. The volume of lubricant is controlled in such a way that no free bulk oil is present in the vicinity of the contact. An abrupt change in the slope of the Stribeck curve in the Hydrodynamic Lubrication zone is interpreted as the onset of starvation. It is then shown that the use of ferrofluids in the presence of a magnetic field distribution can change the conditions at which this onset of starvation occurs. Different magnetic field distributions are tested for different values of load and ferrofluid viscosity. It is proposed that ferrofluid lubricants in conjunction with a suitably positioned magnetic field can be used to promote replenishment, and thus control and reduce lubricant starvation.
Myant C, Spikes HA, 2010, FILM THICKNESS STUDY OF LUBRICATED, COMPLIANT CONTACTS, ASME/STLE International Joint Tribology Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 59-61
Myant C, Spikes HA, Stokes JR, 2010, Influence of load and elastic properties on the rolling and sliding friction of lubricated compliant contacts, TRIBOLOGY INTERNATIONAL, Vol: 43, Pages: 55-63, ISSN: 0301-679X
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.